Kyushu University Academic Staff Educational and Research Activities Database
List of Papers
Kenji Tahara Last modified date:2018.06.07

Associate Professor / Control Systems / Department of Mechanical Engineering / Faculty of Engineering


Papers
1. Ken Masuya, Shu Ono, Kentaro Takagi, Kenji Tahara , Feedforward Control of Twisted and Coiled Polymer Actuator Based on a Macroscopic Nonlinear Model Focusing on Energy, IEEE Robotics and Automation Letters, 10.1109/LRA.2018.2801884, 3, 3, 1824-1831, 2018.07, This letter proposes a feedforward (FF) controller for the twisted and coiled polymer actuator (TCPA), the so-called fishing line/sewing thread artificial muscle, based on its macroscopic nonlinear model. TCPA is an artificial muscle, and it contracts up to 50% in response to heating. Although several methods considering Joule heating as the input have been proposed to control the TCPA displacement, the FF controller based on the linear model shows the nonnegligible offset error. Therefore, the FF controller should be designed based on a nonlinear model, e.g., the model constructed by the authors. However, computing the inverse of the nonlinear model for the FF controller is difficult. Even if the inverse can be computed under static conditions, the problem of how to compensate the dynamics still remains. For this problem, we compensate the dynamics based on the idea of the Hammerstein model, namely we divide the inverse dynamics into the nonlinear transformation part and linear dynamics part. The former part consists of a converter from the displacement to temperature and a ratio adjuster for the squared voltage. Meanwhile, the latter is represented by the linear model of TCPA temperature. Through experiments, it is verified that the proposed FF controller can reduce the offset error of the displacement compared with the linear controller..
2. Y. Matsutani, Kenji Tahara, H. Kino, H. Ochi, Complementary compound set-point control by combining muscular internal force feedforward control and sensory feedback control including a time delay, Advanced Robotics, https://doi.org/10.1080/01691864.2018.1453375, 32, 8, 1-15, 2018.03, This paper proposes a new set-point control method for a musculoskeletal arm by combining muscular internal force feedforward control with feedback control including a large time delay. The proposed method accomplishes robust and rapid positioning with a relatively small muscular force. In the positioning by the muscular internal force feedforward controller, a large muscular force is required to achieve good performance. On the other hand, in the positioning by the feedback controller including the large time delay, the system can easily fall into an unstable state. A simple linear combination of these two controllers makes it possible to improve the control performance and to overcome the drawbacks of each controller in a complementary manner. First, a two-link six-muscle arm model is considered as a musculoskeletal system in this study. Second, the new set-point control method, which consists of the feedforward control signal and the feedback control signal including the time delay, is designed. Third, the stability of the proposed method is investigated using the Lyapunov–Razumikhin method. Finally, the results of numerical simulations and experiments are presented to demonstrate the advantages of the proposed method..
3. Efi Psomopoulou, Daiki Karashima, Zoe Doulgeri, Kenji Tahara, Stable pinching by controlling finger relative orientation of robotic fingers with rolling soft tips, Robotica, https://doi.org/10.1017/S0263574717000303, 36, 2, 204-224, 2018.02, There is a large gap between reality and grasp models that are currently available because of the static analysis that characterizes these approaches. This work attempts to fill this need by proposing a control law that, starting from an initial contact state which does not necessarily correspond to an equilibrium, achieves dynamically a stable grasp and a relative finger orientation in the case of pinching an object with arbitrary shape via rolling soft fingertips. Controlling relative finger orientation may improve grasping force manipulability and allow the appropriate shaping of the composite object consisted of the distal links and the object, for facilitating subsequent tasks. The proposed controller utilizes only finger proprioceptive measurements and is not based on the system model. Simulation and experimental results demonstrate the performance of the proposed controller with objects of different shapes..
4. Miao Li, Kenji Tahara, Aude Billard, Learning task manifolds for constrained object manipulation, Autonomous Robots, https://doi.org/10.1007/s10514-017-9643-z, 42, 1, 159-174, 2018.01, Reliable physical interaction is essential for many important challenges in robotic manipulation. In this paper, we consider Constrained Object Manipulations tasks (COM), i.e. tasks for which constraints are imposed on the grasped object rather than on the robot’s configuration. To enable robust physical interaction with the environment, this paper presents a manifold learning approach to encode the COM task as a vector field. This representation enables an intuitive task-consistent adaptation based on an object-level impedance controller. Simulations and experimental evaluations demonstrate the effectiveness of our approach for several typical COM tasks, including dexterous manipulation and contour following..
5. Yuki Matsutani, Kenji Tahara, Hitoshi Kino, Hiroaki Ochi, Stiffness evaluation of a tendon-driven robot with variable joint stiffness mechanisms, 17th IEEE-RAS International Conference on Humanoid Robotics, Humanoids 2017 2017 IEEE-RAS 17th International Conference on Humanoid Robotics, Humanoids 2017, https://doi.org/10.1109/HUMANOIDS.2017.8246877, Part F134101, 213-218, 2017.12, This paper proposes a new tendon-driven robot with variable joint stiffness mechanisms. The tendon-driven robot is able to vary the stiffness of joints by sliding variable stiffness mechanisms over the link by wire tensions. As a reason for that structure and moment arms of the tendon-driven robot are changed depending on the position of the variable mechanism. Thus in this paper, the tendon-driven robot with variable stiffness mechanisms is designed, and the stiffness of the tendon-driven robot is evaluated by using a stiffness ellipsoid..
6. Ken Masuya, Shu Ono, Kentaro Takagi, Kenji Tahara, Modeling framework for macroscopic dynamics of twisted and coiled polymer actuator driven by Joule heating focusing on energy and convective heat transfer, Sensors and Actuators, A: Physical, https://doi.org/10.1016/j.sna.2017.10.016, 267, 443-454, 2017.11, In this paper, a nonlinear dynamics model of the twisted and coiled polymer actuator (TCPA) driven by Joule heating is proposed. TCPA is an actuator based on the phenomenon that the twisted and coiled polymer contracts by heating. TCPA has received considerable research attention after the discovery of this phenomenon. Although several conventional models were proposed to explain TCPA behavior, they do not address several characteristics of a real TCPA, namely, the delay of the displacement to the temperature, temperature behavior to the input (Joule heating), and effect of the convective heat transfer on the relationship between the displacement and temperature. The macroscopic modeling framework presented herein explains these properties. The main ideas of the proposed model are (1) the energy relating to TCPA, and (2) the temperature and velocity dependence of the convective heat transfer coefficient. Experiments were conducted for three kinds of TCPA. It was verified that the proposed model is more viable than a conventional model. In particular, the proposed model reduced the prediction errors of the displacement by more than 50% compared with the conventional model..
7. Ryuta Ozawa, Kenji Tahara, Grasp and dexterous manipulation of multi-fingered robotic hands
a review from a control view point, Advanced Robotics, https://doi.org/10.1080/01691864.2017.1365011, 31, 19-20, 1030-1050, 2017.10, Manipulation is one of the most important fields in robotics. Nevertheless, even given the long history of manipulation research, technologies for multi-fingered robotic hands are still in development. This paper investigates past research studies on control systems of multi-fingered robotic hands for grasping and manipulation..
8. Ken Masuya, Shu Ono, Kentaro Takagi, Kenji Tahara, Nonlinear dynamics of twisted and coiled polymer actuator made of conductive nylon based on the energy balance, 2017 IEEE International Conference on Advanced Intelligent Mechatronics, AIM 2017 2017 IEEE International Conference on Advanced Intelligent Mechatronics, AIM 2017, https://doi.org/10.1109/AIM.2017.8014112, 779-784, 2017.08, This paper proposes a novel dynamics model of the twisted and coiled polymer actuator (TCPA) which is one of the artificial muscles recently discovered. It can be driven by Joule heating and can contract up to 25%. Most of the conventional works employed the linear model of TCPA which represents the relationships between the input voltage, the temperature, and the displacement, but the real TCPA shows the nonlinearity. Although a nonlinear model was proposed based on the curve fitting, it is difficult to apply the model to the various TCPAs. Additionally, the conventional works cannot explain the effect of the convective heat transfer condition on the displacement behavior of TCPA. This paper aims to construct a general nonlinear model of TCPA based on the following two ideas: (1) The energy balance of TCPA and (2) the temperature and velocity dependence of the heat transfer coefficient. The temperature model is obtained from the time derivative of the energy balance, and the displacement model is derived as Lagrange's equation of motion with the dissipation function. Through experiments, it is verified that the proposed model is closer to the real dynamics than the conventional linear model..
9. H. Kino, H. Ochi, Y. Matsutani, Kenji Tahara, Sensorless point-to-point control for a musculoskeletal tendon-driven manipulator
analysis of a two-DOF planar system with six tendons, Advanced Robotics, https://doi.org/10.1080/01691864.2017.1372212, 31, 16, 851-864, 2017.08, Tendon-driven robot utilizes only tensile force (i.e. tension) for motion generation. Therefore, a redundant actuation is characteristically necessary, and then it yields the internal force among tendons. Given the internal force for balance at a desired posture, the musculoskeletal tendon-driven manipulator has the inherent possibility of point-to-point position control without any sensory feedback. However, the motion convergence is strongly governed by the arrangement of tendons.This study analyzes the mathematical conditions of convergence for this sensorless position control by use of a Lyapunov function. Subsequently, targeting the two-link musculoskeletal structure with six tendons, the sufficient conditions for the convergence at desired posture are further defined by employing an approximation of the tendon-length based on a Taylor expansion. Finally, the convergent conditions are verified through simulation and validated via experimental results..
10. Tetsuya Morizono, Kenji Tahara, Hitoshi Kino, A study on effect of biarticular muscles in an antagonistically actuated robot arm through numerical simulations, Artificial Life and Robotics, https://doi.org/10.1007/s10015-016-0322-5, 22, 1, 74-82, 2017.03, Control of articulated robots by biarticular actuation has recently attracted great attention in the research field of robotics. Although many of studies concerned with this issue deal with legged robots or robot arms kinetically interacting with environment such as a floor or an object, motion control of an articulated robot arm with no kinetic interaction is also an interesting topic of biarticular actuation. In the motion control, a major issue is how it is possible for biarticular actuation to contribute to improvement of control; however, showing a clear finding for this issue seems to be considerably difficult. This paper considers a study for exploring that issue. Biarticular actuation usually constitutes a redundant actuation system; therefore, control of a robot arm to a desired posture can be achieved by many combinations of actuator forces. Based on this feature, this paper considers three typical combinations of actuator forces. Point-to-point control of the robot is performed for each of the combinations in simulation, and control performances of the combinations are compared with each other. In addition, the performances are compared with that of monoarticular actuation. In those comparisons, two of the three combinations show similar control performances, which suggests possibility of major contribution of biarticular actuators to motion control of a robot arm. On the other hand, control performance of the other combination is similar to that of monoarticular actuation, rather than those of other two combinations..
11. Kentaro Takagi, Takeshi Arakawa, Jun Takeda, Ken Masuya, Kenji Tahara, Kinji Asaka, Position control of twisted and coiled polymer actuator using a controlled fan for cooling, Electroactive Polymer Actuators and Devices (EAPAD) 2017 Electroactive Polymer Actuators and Devices (EAPAD) 2017, https://doi.org/10.1117/12.2259766, 10163, 2017, Recently, artificial muscles made of fishing lines or sewing threads, namely twisted and coiled polymer actuators (TCPAs), have been proposed by Haines et al. A TCPA contracts by applying heat and returns to its initial length by cooling. A TCPA can be driven by voltage if the TCPA is plated by metal or if conductive wire such as nichrome is wound around it. Compared with the conventional electroactive polymers, advantages of TCPAs are low cost, simple structure, large actuation strain, and large force. However, a big disadvantage of TCPAs is slow response due to heat transfer. The problem becomes apparent during cooling, although the response of heating can be improved by feedback control. This paper proposes a control method of switching heating and cooling. In the proposed method, a TCPA is cooled by an electric cooling fan. When the TCPA is heating, the cooling fan is stopped. In a previous report, the response speed can be improved by keeping cooling fan always on; however, unnecessary energy consumption is required even during heating. In the proposed method, energy consumption during heating does not increase and the response speed can be improved using fan only during cooling. The proposed control law is as follows. Firstly, the desired control input is determined by PI-D control with respect to the length of the actuator. Then, the control inputs to the heater and to the cooling fan are switched according to the sign of the PI-D controller output. The effectiveness of the proposed control method is demonstrated by comparing the cases with and without the cooling fan in the experiments..
12. Torque Control of Torsional-Type Fishing-Line Artificial Muscle Actuator.
13. Macroscopic Displacement Model of Twisted and Coiled Polymer Actuator based on the Temperature and Velocity Dependence of Convective Heat Transfer.
14. Position and Stiffness Control of 2-DOF Manipulator Using Multiple Fishing Line Actuators.
15. Position and Force Control of 1 DOF Manipulator driven by Dielectric Elastomer Actuators.
16. Development of Actuator Unit consisting of Multiple Twisted and Coiled Polymer Actuators.
17. Kenji Tahara, Yuki Matsutani, Daisuke Nakagawa, Masataka Sato, Hitoshi Kino, Variable combination of feed-forward and feedback manners for set-point control of a musculoskeletal arm considering the maximum exertable muscular force, 42nd Conference of the Industrial Electronics Society, IECON 2016 Proceedings of the IECON 2016 - 42nd Annual Conference of the Industrial Electronics Society, https://doi.org/10.1109/IECON.2016.7793411, 815-820, 2016.12, In this paper, our previously proposed set-point control method for a musculoskeletal system is improved to reduce required muscular forces and to avoid a saturation of muscular forces during movement. The previous method is robust against a considerable time-delay in sensory information, but it still requires large muscular forces to accomplish a desired position, and the maximum exertable muscular force has not yet been taken into consideration. To cope with these two issues, two variable parameters are newly introduced. One is for changing the combination ratio of feed-forward and feedback controllers to reduce necessary muscular forces. The other is for avoiding the saturation of muscular forces during movement The effectiveness of the proposed controller is demonstrated through several numerical simulation results..
18. Tetsuya Morizono, Kenji Tahara, Hitoshi Kino, Experimental investigation of contribution of biarticular actuation to mappings between sensory and motor spaces, 41st Annual Conference of the IEEE Industrial Electronics Society, IECON 2015 IECON 2015 - 41st Annual Conference of the IEEE Industrial Electronics Society, https://doi.org/10.1109/IECON.2015.7392655, 3573-3578, 2016.01, This paper considers experimental investigation of an antagonistically actuated robot manipulator. The focus of the investigation is how biarticular actuation contributes to control of the manipulator. Based on the feature that antagonistically robot manipulators can be controlled by feedforward control with constant inputs, this paper treats the case of PTP (point-to-point) control of robot postures. Due to expectation of difficulty for analytical approach, this paper takes experimental methodology of acquiring mappings between sensory and motor spaces by ANNs (artificial neural networks). Based on the idea that contribution of biarticular actuation may be influenced by choice of a sensory space, this paper considers not only joint angles of a manipulator but also Cartesian coordinate and angles in binocular visual space at the hand of the manipulator as sensory spaces. For each of them, the mappings obtained from trained ANNs are compared for the cases with and without biarticular actuation, based on interpolation performance of the ANNs examined through PTP control of the manipulator. The results of the comparison shows that choice of a sensory space is less effective to the interpolation performance in the case of biarticular actuation..
19. Hiroaki Ochi, Hitoshi Kino, Kenji Tahara, Yuki Matsutani, Geometrie conditions for feedforward positioning of musculoskeletal tendon-driven structure, 41st Annual Conference of the IEEE Industrial Electronics Society, IECON 2015 IECON 2015 - 41st Annual Conference of the IEEE Industrial Electronics Society, https://doi.org/10.1109/IECON.2015.7392248, 1109-1114, 2016.01, The human body possesses a musculoskeletal structure in which muscles exist around the bones and joints. The musculoskeletal tendon-driven robot utilizes this structure. This robotic system uses sets of mechanical tendons, such as wire-cables and actuators instead of the vital muscles. The redundant actuation is necessary for the system when it does not actively use any external force nor a tensioner because the mechanical tendon can transmit only a tensile force. This structural characteristic enables feedforward motion-generation that does not need any sensory feedback. However, the convergent posture strongly depends on the tendon-arrangement. Targeting the tendon-driven manipulator, which has two links and six tendons, this paper expands the mathematical conditions for the convergence into the geometric conditions of tendon-arrangement. Based on the geometric conditions, a design method of the tendon-arrangement is discussed..
20. Muscular Arrangement Conditions of Musculoskeletal System with Two Joints and Six Muscles for Feedforward Position Control.
21. Takeshi Arakawa, Kentaro Takagi, Kenji Tahara, Kinji Asaka, Position control of fishing line artificial muscles (coiled polymer actuators) from nylon thread, Electroactive Polymer Actuators and Devices (EAPAD) 2016 Electroactive Polymer Actuators and Devices (EAPAD) 2016, https://doi.org/10.1117/12.2218850, 9798, 2016, Recently, fishing line artificial muscle has been developed and is paid much attention due to the properties such as large contraction, light weight and extremely low cost. Typical fishing line artificial muscle is made from Nylon thread and made by just twisting the polymer. In this paper, because of the structure of the actuator, such actuators may be named as coiled polymer actuators (CPAs). In this paper, a CPA is fabricated from commercial Nylon fishing line and Ni-Cr alloy (Nichrome) wire is wound around it. The CPA contracts by the Joule heat generated by applied voltage to the Nichrome wire. For designing the control system, a simple model is proposed. According to the physical principle of the actuator, two first-order transfer functions are introduced to represent the actuator model. One is a system from the input power to the temperature and the other is a system from the temperature to the deformation. From the system identification result, it is shown that the dominant dynamics is the system from the input power to the temperature. Using the developed model, position control of the voltage-driven CPA is discussed. Firstly, the static nonlinearity from the voltage to the power is eliminated. Then, a 2-DOF PID controller which includes an inversion-based feed forward controller and a PID controller are designed. In order to demonstrate the proposed controller, experimental verification is shown..
22. Set-point Control for a Musculoskeletal System using Complementary Combination of a Sensory Feedback Including a Time-delay and a Muscular Internal Force Feedforward.
23. Tokuo Tsuji, Kosei Baba, Kenji Tahara, Kensuke Harada, Kenichi Morooka, Ryo Kurazume, Grasp stability evaluation based on energy tolerance in potential field, IEEE/RSJ International Conference on Intelligent Robots and Systems, IROS 2015 IROS Hamburg 2015 - Conference Digest IEEE/RSJ International Conference on Intelligent Robots and Systems, https://doi.org/10.1109/IROS.2015.7353688, 2015-December, 2311-2316, 2015.12, We propose an evaluation method of grasp stability which takes into account the elastic deformation of fingertips from the viewpoint of energy. An evaluation value of grasp stability is derived as the minimum energy which causes slippage of a fingertip on its contact surface. To formulate the evaluation value, the elastic potential energy of fingertips and the gravitational potential energy of a grasped object are considered. It is ensured that fingertips do not slip on grasped object surfaces if the external energy applied to the object is less than the evaluation value. Since our evaluation value explicitly considers the deformation values of fingertips, grasp stability is evaluated by taking into consideration the contact forces generated by the deformation. The effectiveness of our method is verified through numerical examples..
24. 1P1-X02 Set-point Control of a Musculoskeletal System Considering Maximum Muscular Force.
25. 1P2-O08 Object Manipulation using a Particle Filter to Estimate a Position and Attitude of an Grasped Object.
26. 2A2-K06 Development of Wearable Walking Assist Device using Linear Actuator and Its Verification through Numerical Simulations.
27. Miao Li, Hang Yin, Kenji Tahara, Aude Billard, Learning object-level impedance control for robust grasping and dexterous manipulation, Quaternary International, https://doi.org/10.1109/ICRA.2014.6907861, 6784-6791, 2014.09, Object-level impedance control is of great importance for object-centric tasks, such as robust grasping and dexterous manipulation. Despite the recent progress on this topic, how to specify the desired object impedance for a given task remains an open issue. In this paper, we decompose the object's impedance into two complementary components-The impedance for stable grasping and impedance for object manipulation. Then, we present a method to learn the desired object's manipulation impedance (stiffness) using data obtained from human demonstration. The approach is validated in two tasks, for robust grasping of a wine glass and for inserting a bulb, using the 16 degrees of freedom Allegro Hand mounted with the SynTouch tactile sensors..
28. Yuki Matsutani, Kenji Tahara, Hitoshi Kino, Hiroaki Ochi, Motoji Yamamoto, Set-point control of a musculoskeletal arm by The complementary combination of a feedforward and feedback manner, Quaternary International, https://doi.org/10.1109/ICRA.2014.6907729, 5908-5914, 2014.09, This paper proposes a novel set-point control method of a musculoskeletal system by combining a feedforward and feedback manner To complement each drawback each other. In our previous work, a feedforward positioning method of The musculoskeletal arm model was proposed which does not need any realtime sensory information. Its performance, however, depends on a muscular arrangement and an attitude of The arm, and Thereby a large initial muscular internal force is necessary To make a good performance. On The other hand, it is well-known That a visual servoing is effective and versatile for The set-point control. However, There is a considerable Time-delay due To a computational burden To acquire useful information from an image and an insufficient sampling period To capture each image when using a video frame rate camera. Thus in This paper, The feedforward and feedback signal are linearly combined into one in order To mutually complement each drawback. The combined control signal is newly designed and Then numerical simulation results are shown To demonstrate The effectiveness and usefulness of The proposed method..
29. Ryota Ishibashi, Hiroaki Ochi, Takahiko Oda, Ryuji Okuda, Katsuya Umeda, Kenji Tahara, Hitoshi Kino, Akira Kojima, A proposal of a SMA actuated wing mechanism using flexible structure for the capability of various flow speeds, 2014 IEEE International Conference on Robotics and Biomimetics, IEEE ROBIO 2014 2014 IEEE International Conference on Robotics and Biomimetics, IEEE ROBIO 2014, https://doi.org/10.1109/ROBIO.2014.7090746, 2673-2678, 2014.04, This paper proposed a concept of flexible wing-mechanism for the underwater fishlike robots. The proposed system consists of a fishlike body and a pair of flexible wing. The flexible wing mechanism utilizes a Shape Memory Alloy (SMA) actuator to realize small and lightweight system with high output/weight ratio. The SMA actuator can be controlled to adjust the shape. In the flow of water, shape of the wings is controlled and then the fluid resistance will be changed. Then, we can control the posture of the robot. The wing mechanism is constructed mainly from flexible materials. Thus, range of the fluid resistance becomes different between the high speed flow and low speed flow. In the fast flow condition, flexible wing mechanism is compressed and the range of the shape control becomes low. Then, the mechanism can control the posture of the robot under the various flow speeds..
30. Tokuo Tsuji, Kosei Baba, Kenji Tahara, Kensuke Harada, Kenichi Morooka, Ryo Kurazume, Grasp stability analysis for elastic fingertips by using potential energy, 7th IEEE/SICE International Symposium on System Integration, SII 2014 2014 IEEE/SICE International Symposium on System Integration, SII 2014, https://doi.org/10.1109/SII.2014.7028081, 453-458, 2014.01, We propose a grasp stability index which takes into account the elastic deformation of fingertips. In this index, an evaluation value of grasp stability is derived as the minimum energy which causes slippage of a fingertip on a grasped object surface. Elastic potential energy of the fingertips and gravitational potential energy of the object are considered in this index. It is ensured that any fingertip does not slip on a grasped object surface if the external energy added to the object is less than the evaluation value. This index has good features as follows. (i) Contact forces corresponding to the grasping state are taken into account. (ii) It is possible to derive a condition of stable grasp including the kinetic energy of a grasped object. The effectiveness of this index is verified through several numerical examples..
31. Tomofumi Okada, Kenji Tahara, Development of a two-link planar manipulator with continuously variable transmission mechanism, 2014 IEEE/ASME International Conference on Advanced Intelligent Mechatronics, AIM 2014 AIM 2014 - IEEE/ASME International Conference on Advanced Intelligent Mechatronics, https://doi.org/10.1109/AIM.2014.6878147, 617-622, 2014, This paper proposes a novel two-link planar manipulator with continuously variable transmission (CVT) mechanism by means of plural linear shaft motors. In our previous works, we have proposed the parallel-link manipulator with the CVT mechanism which has two orthogonal DOFs. However, its configuration is not useful for a practical field because only one main link can be rotated around two joints like a joystick. In order for this mechanism to be more useful, the two-link planar type manipulator with the CVT is newly modeled and developed. Firstly, the proposed manipulator is modeled, and its control signals are designed. Next, the output force of the end-point of the manipulator is evaluated by using both the Manipulating-Force Ellipsoid and the Dynamic Manipulability Ellipsoid. After that, several fundamental experiments are performed to evaluate the CVT mechanism and show the effectiveness of the proposed manipulator..
32. Hitoshi Kino, Shiro Kikuchi, Yuki Matsutani, Kenji Tahara, Takahiro Nishiyama, Numerical analysis of feedforward position control for non-pulley musculoskeletal system
A case study of muscular arrangements of a two-link planar system with six muscles, Advanced Robotics, https://doi.org/10.1080/01691864.2013.824133, 27, 16, 1235-1248, 2013.08, In a musculoskeletal system like a tendon-driven robot, redundant actuation is necessary because muscles (or mechanical parts such as tendons) can transmit tension only unidirectionally. This redundancy yields internal force among muscles, which has a particular field of potential energy. Using internal force as a feedforward input, a musculoskeletal system can achieve feedforward position control with no sensory feedback. This paper studies the feedforward position control coming from the redundancy for a non-pulley musculoskeletal system. Targeting a planar two-link system with six muscles as a case study, the motion convergence depending on the muscular arrangement is examined quasi-statically. The results point out that the convergence is extremely sensitive to the muscular arrangement, and adding small offsets for the muscular connected points can remarkably improve the positioning performance..
33. Akihiro Kawamura, Kenji Tahara, Ryo Kurazume, Tsutomu Hasegawa, Dynamic grasping of an arbitrary polyhedral object, Robotica, http://dx.doi.org/10.1017/S0263574712000525, 31, 4, 511-523, 2013.07.
34. Akihiro Kawamura, Kenji Tahara, Ryo Kurazume, Tsutomu Hasegawa, Dynamic grasping of an arbitrary polyhedral object, Robotica, https://doi.org/10.1017/S0263574712000525, 31, 4, 511-523, 2013.07, This paper proposes a novel dynamic stable grasping method of an arbitrary polyhedral object for a hand-arm system with hemispherical fingertips. This method makes it possible to satisfy the force/torque equilibrium condition for the immobilization of the object without knowledge of the object. Two control signals are proposed which generate grasping forces normal and tangential to an object surface in a final state. The dynamics of the overall system is modeled and analyzed theoretically. We demonstrate the stable grasping of an arbitrary polyhedral object using the proposed controller through numerical simulations and experiments using a newly developed mechanical hand-arm system..
35. Hitoshi Kino, Shiro Kikuchi, Yuki Matsutani, Kenji Tahara, Takahiro Nishiyama, Numeracal Analysis of Feedforward Position Control for Non-pulley Musculoskeletal System: a Case Study of Muscular Arrangements of a Two-link Planar System with Six Muscles, Robotics Society of Japan, 10.1080/01691864.2013.824133, 27, 16, 1235-1248, 2013.03.
36. Akihiro Kawamura, Kenji Tahara, Ryo Kurazume, Tsutomu Hasegawa, Robust visual servoing for object manipulation against temporary loss of sensory information using a multi-fingered hand-arm, Journal of Robotics and Mechatronics, 25, 1, 125-135, 2013.01.
37. Akihiro Kawamura, Kenji Tahara, Ryo Kurazume, Tsutomu Hasegawa, Robust visual servoing for object manipulation against temporary loss of sensory information using a multi-fingered hand-arm, Journal of Robotics and Mechatronics, https://doi.org/10.20965/jrm.2013.p0125, 25, 1, 125-135, 2013.01, This paper proposes a robust visual servoing method for object manipulation against temporary loss of sensory information. It is known that visual information is useful for reliable object grasping and precise manipulation. Visual information becomes unavailable, however when occlusion occurs or a grasped object disappears during manipulation. In that case, the behavior of the visual servoing system becomes unstable. Our proposed method enables an object to be grasped and manipulated stably even if visual information is temporarily unavailable during manipulation. This method is based on dynamic stable object grasping and manipulation proposed in our previous work and the concept of virtual object information. A dynamic model of the overall system is first formulated. A new controller using both actual and virtual object information is proposed next. The usefulness of this method is finally verified through both numerical simulation and experiments using a triple-fingered mechanical hand..
38. Yuki Matsutani, Hiroaki Ochi, Hitoshi Kino, Kenji Tahara, Motoji Yamamoto, Feed-forward positioning of musculoskeletal-like robotic systems with muscular viscosity
Determination of an adequate internal force, 2013 IEEE Workshop on Advanced Robotics and Its Social Impacts, ARSO 2013 2013 IEEE Workshop on Advanced Robotics and Its Social Impacts, ARSO 2013 - Conference Digest, https://doi.org/10.1109/ARSO.2013.6705498, 7-12, 2013, This paper proposes a new feed-forward positioning method for a musculoskeletal-like robotic system considering a muscle-like nonlinear viscosity, and a new determination method of the internal force using the reinforcement learning scheme. In our previous works, a feed-forward positioning method for the musculoskeletal-like robotic systems has been proposed. In the method, the position regulation of the system can be accomplished by inputting a desired internal force balancing at a desired position. It has been quite effective for the muscle-like driven mechanism because no sensor is necessary to regulate the position. However, this method often induces an overshoot phenomenon when performing a set-point control. In addition, there is another intrinsic problem that musculoskeletal-like redundant-driven mechanisms own the ill-posed problems that the internal force is unable to determine uniquely. In this paper, for the farmer problem, a muscle-like nonlinear viscosity is newly added to the controller to reduce such an overshoot phenomenon and then to expand the stable region of the manipulator. For the latter problem, a determination method of the internal force using a reinforcement learning scheme is newly proposed. In what follows, firstly a new feed-forward controller which considers the muscle-like viscosity is introduced, and shows its effectiveness through numerical simulations. Next, the determination method of the internal force using a reinforcement learning scheme is proposed and its effectiveness is also shown through numerical simulations..
39. Hitoshi Kino, Shiro Kikuchi, Yuki Matsutani, Kenji Tahara, Sensibility to muscular arrangement of feedforward position control for non-pulley-musculoskeletal system, 5th FTRA International Conference on Information Technology Convergence and Services, ITCS 2013 and the 3rd International Conference on Intelligent Robotics, Automations, Telecommunication Facilities, and Applications, IRoA 2013 Information Technology Convergence: Security, Robotics, Automations and Communication, https://doi.org/10.1007/978-94-007-6996-0-86, 253 LNEE, 827-833, 2013, This paper studies the feedforward position control induced by the redundancy in a non-pulley-musculoskeletal system. Targeting a planar two-link musculoskeletal system with six muscles as a case study, the motion convergence depending on the muscular arrangement is examined. The results indicate that the motion convergence is extremely sensitive to the muscular arrangement and that adding small offsets for the points of muscle connection can remarkably improve the positioning performance..
40. Hitoshi Kino, Hiroaki Ochi, Kenji Tahara, Yuki Matsutani, Ryota Ishibashi, Study of human motion generation based on redundancy of musculoskeletal structure
Analysis of potential generated by internal force for two-link system, 2013 IEEE Workshop on Advanced Robotics and Its Social Impacts, ARSO 2013 2013 IEEE Workshop on Advanced Robotics and Its Social Impacts, ARSO 2013 - Conference Digest, https://doi.org/10.1109/ARSO.2013.6705497, 1-6, 2013, The human body has a musculoskeletal system with the muscles which exist around the bones and joints. Taking notice of the structural characteristics that a human possesses inherently, this paper analyzes feedforward position control for the musculoskeletal system. The feedforward positioning does not need any sensory feedback by use of internal force balancing at a desired posture. Targeting a non-pulley musculoskeletal system with two links and six muscles, this paper clarifies mathematical conditions of the feedforward positioning to converge at a desired posture. In the analysis, muscular length is approximated by Taylor expansion. Based on quasi-statical approach, the convergent conditions are clarified. The verification of the conditions is conducted through simulation..
41. Kenji Tahara, Keigo Maruta, Akihiro Kawamura, Motoji Yamamoto, Externally sensorless dynamic regrasping and manipulation by a triple-fingered robotic hand with torsional fingertip joints, 2012 IEEE International Conference on Robotics and Automation, ICRA 2012 2012 IEEE International Conference on Robotics and Automation, ICRA 2012, https://doi.org/10.1109/ICRA.2012.6224681, 3252-3257, 2012.01, This paper presents an improvement of our previously proposed dynamic object grasping and manipulation method. This method, which utilizes a dual-fingered hand of which each soft and hemispheric fingertip owns a torsional joint, has performed novel 3-dimensional dynamic object grasping and manipulation stably without the use of any external sensing device. However, several limitation and weakness have still remained in terms of dexterity and robustness. In order to improve it, firstly a triple-fingered hand is newly introduced instead of the dual-fingered hand to perform regrasping. Next, the previously proposed stable object grasping controller is adequately modified to perform dynamic regrasping during manipulation. Additionally, the virtual object attitude controller is also modified to improve its performance. Finally, several experiments are conducted by using a prototype, and the usefulness of proposed controller is demonstrated through these results..
42. Kenji Tahara, Keigo Maruta, Motoji Yamamoto, Alternative dexterous object manipulation using torsional fingertip joints of multifingered hand, 22nd Annual Symp. on Micro-Nano Mechatronics and Human Science, MHS 2011, Held Jointly with the Symp. on COE for Education and Research of Micro-Nano Mechatronics, Micro-Nano GCOE 2011, Symp. on Hyper Bio Assembler for 3D Cellular System Innovation 2011 Int. Symp. on Micro-NanoMechatronics and Human Science, Symp. on "COE for Education and Research of Micro-Nano Mechatronics", Symposium on "Hyper Bio Assembler for 3D Cellular System Innovation", https://doi.org/10.1109/MHS.2011.6102234, 469-471, 2012, This paper proposes a novel object manipulation method by a multifingered robotic hand with torsional fingertip joints. By using the unique joint configuration effectively, a dynamic object manipulation can be achieved without the use of any external sensing. Firstly, a dynamic equation of motion of the overall system considering contact models between each fingertip and objectsurface is given. Secondly, an externally sensorless control signal to grasp and manipulate the object is designed. A numerical simulation and an experiment using a prototype are performed, and then finally the effectiveness of proposed method is illustrated through a simulation and an experiment..
43. Kenji Tahara, Yuta Kuboyama, Ryo Kurazume, Iterative learning control for a musculoskeletal arm
Utilizing multiple space variables to improve the robustness, 25th IEEE/RSJ International Conference on Robotics and Intelligent Systems, IROS 2012 2012 IEEE/RSJ International Conference on Intelligent Robots and Systems, IROS 2012, https://doi.org/10.1109/IROS.2012.6385628, 4620-4625, 2012, In this paper, a new iterative learning control method which uses multiple space variables for a musculoskeletal-like arm system is proposed to improve the robustness against noises being included in sensory information. In our previous works, the iterative learning control method for the redundant musculoskeletal arm to acquire a desired endpoint trajectory simultaneous with an adequate internal force was proposed. The controller was designed using only muscle space variables, such as a muscle length and contractile velocity. It is known that the movement of the musculoskeletal system can be expressed in a hierarchical three-layered space which is composed of the muscle space, the joint space and the task space. Thus, the new iterative learning control input is composed of multiple space variables to improve its performance and robustness. Numerical simulations are conducted and their result is evaluated from the viewpoint of the robustness to noises of sensory information. An experiment is performed using a prototype of musculoskeletal-like manipulator, and the practical usefulness of the proposed method is demonstrated through the result..
44. Ryota Ishibashi, Takahiko Oda, Kenji Tahara, Hitoshi Kino, Akira Kojima, Parallel system using V-shaped shape memory alloy actuator, 2012 51st Annual Conference on of the Society of Instrument and Control Engineers of Japan, SICE 2012 2012 Proceedings of SICE Annual Conference, SICE 2012, 1745-1750, 2012, This paper proposed a type of tendon driven system using V-shaped SMA (shape-memory-alloy) actuator. In the proposed system, SMA actuators are bended at the end effector and the bended angles are controllable. Thus, the stiffness of the system can be adjusted by the bended angles. In addition, to control the end effector to the desired position, we developed a position control method based on the internal force using only the geometric constraints of the system. The validity of the proposed method was examined by some experiments..
45. Akihiro Kawamura, Kenji Tahara, Ryo Kurazume, Tsutomu Hasegawa, Robust visual servoing for object manipulation with large time-delays of visual information, 25th IEEE/RSJ International Conference on Robotics and Intelligent Systems, IROS 2012 2012 IEEE/RSJ International Conference on Intelligent Robots and Systems, IROS 2012, https://doi.org/10.1109/IROS.2012.6385589, 4797-4803, 2012, This paper proposes a new visual servoing method for object manipulation robust to considerable time-delays of visual information. There still remain several problems in visual servoing methods although they are quite useful and effective for dexterous object manipulation. For instance, time-delays to obtain necessary information for object manipulation from visual images induce unstable behavior. The time-delays are mainly caused by low sampling rate of visual sensing system, computational cost for image processing, and latency of data transmission from visual sensor to processor. The method makes it possible to avoid such unstable behavior of the systems due to considerable time-delays using virtual object frame defined by only each joint angle. Firstly, a new control scheme for object manipulation using the virtual object frame is designed. Next, numerical simulations are conducted to verify the effectiveness of the control scheme. Finally, experimental results are shown to demonstrate the practical usefulness of proposed method..
46. K. Tahara, S. Arimoto, R. Ozawa and Z.W. Luo, Bio-mimetic pinching movements of musculo-skeletal dual finger model, Advanced Robotics, 25, 1-2, 175-204, 2011.01.
47. Kenji Tahara, Suguru Arimoto, Ryuta Ozawa, Zhi Wei Luo, Biomimetic pinching movements of a musculo-skeletal dual-finger model, Advanced Robotics, https://doi.org/10.1163/016918610X538543, 25, 1-2, 175-204, 2011.01, The present paper investigates pinching movements using an index finger and a thumb actuated by redundant nonlinear digitorum muscles mimicking the configuration of human fingers. A dual-finger model with 2-d.o.f. joints for each finger and redundant nonlinear digitorum muscles is formulated to mimic the structure of human fingers. First, the kinematics and dynamics of the overall finger-object system, as well as the nonlinear muscular dynamics, are derived in accordance with the results of physiological studies. Next, a sensory-motor control law is proposed to enable stable pinching simultaneously with orientation regulation of an object. This control law includes an internal force term generated by co-construction of the redundant muscles. It is shown that the internal force term can modulate the damping factor in the joint space by its nonlinearity. Based on this effect, it is then shown by numerical simulation that our sensory-motor control law with co-contraction of each digitorum muscle makes it possible to realize pinching movements. Therefore, the pinching movements may be realized by means of a musculo-skeletal dual-finger system with the sensory-motor control law and co-contraction of redundant digitorum muscles..
48. Akihiro Kawamura, Kenji Tahara, Ryo Kurazume, Tsutomu Hasegawa, Dynamic object manipulation using a multi-fingered hand-arm system
Enhancement of a grasping capability using relative attitude constraints of fingers, IEEE 15th International Conference on Advanced Robotics: New Boundaries for Robotics, ICAR 2011 IEEE 15th International Conference on Advanced Robotics: New Boundaries for Robotics, ICAR 2011, https://doi.org/10.1109/ICAR.2011.6088574, 8-14, 2011, In this paper, an enhancement of a dynamic object grasping and manipulation method, which has been proposed by us previously, is presented. This enhancement makes it possible to grasp more various shaped objects which could not have been grasped by our previous method. In our previous method, a force/torque equilibrium condition to satisfy stable object grasping has been realized by only using grasping forces normal to an object surfaces. It is because each fingertip is soft and hemispheric and then rolling constraints arise during movement, and these phenomena cannot be stopped while existing the rolling constraint forces. Therefore, satisfying the dynamic force/torque equilibrium condition depends not only on a configuration of the multi-fingered hand system, but also on the shape of the grasped object. In this paper, a class of satisfying the force/torque equilibrium condition is expanded by generating counter tangential forces to suspend the rolling motion of each fingertip. In order to generate the counter tangential force, a relative attitude constraint between each finger is introduced. Firstly, a rolling constraint between each fingertip and object surface is given. Then, a relative attitude constraint control signal to generate constantly-produced tangential forces is designed. Finally, it is demonstrated through numerical simulations that the proposed control method accomplishes to grasp arbitrary shaped polyhedral objects and regulate its position and attitude, simultaneously..
49. Kenji Tahara, Shingo Iwasa, Shu Naba, Motoji Yamamoto, High-backdrivable parallel-link manipulator with continuously variable transmission, 2011 IEEE/RSJ International Conference on Intelligent Robots and Systems: Celebrating 50 Years of Robotics, IROS'11 IROS'11 - 2011 IEEE/RSJ International Conference on Intelligent Robots and Systems: Celebrating 50 Years of Robotics, https://doi.org/10.1109/IROS.2011.6048069, 1843-1848, 2011, This paper proposes a novel high-backdrivable parallel-link manipulator with Continuously Variable Transmission (CVT) mechanism using several shaft actuators. The backdrivability is important and necessary for robots that operate around our life space to guarantee the safety of us, themselves and environments. A rotational actuator with a high reduction ratio reducer has been commonly used in traditional robotics field, but it cannot realize the high-backdrivability without any sensory feedback. In this study, several high-backdrivable shaft actuators are used instead of it. Moreover, the CVT mechanism which is brought by a novel configuration of the parallel mechanism is employed effectively. To utilize multiple shaft actuators with the CVT mechanism is able to surmount a drawback of the shaft actuator whose output force is relatively weak. A simple 1 DOF manipulator is proposed as the first step of this study. Firstly, its kinematic and dynamic models are given. Next, a PD type feedback control signal to regulate the arm's angle and the CVT simultaneously is designed. A static relation between an output end-point force and the CVT mechanism is analyzed. Finally, several fundamental experiments are conducted to show the effectiveness of proposed mechanism..
50. Kenji Tahara, Suguru Arimoto, Iterative learning scheme for a redundant manipulator
Skilled hand writing motion on an arbitrary smooth surface, 2011 IEEE International Conference on Robotics and Automation, ICRA 2011 2011 IEEE International Conference on Robotics and Automation, ICRA 2011, https://doi.org/10.1109/ICRA.2011.5979700, 4682-4687, 2011, This paper proposes an iterative learning control scheme for a redundant manipulator to acquire a skilled hand writing motion of its end-point specified on an arbitrary smooth surface. Firstly, the existence of a unique solution to the Lagrange equation of motion of the robot, whose end-point motion is coincident with a given desired end-point trajectory described in Cartesian coordinate system, is shown theoretically. Second, the iterative learning control signal that enables the robot end-point to trace a desired trajectory specified on an arbitrary smooth surface with fulfilling a desired contact force is designed. Next, a numerical simulation for the iterative learning scheme is conducted to show the effectiveness of the proposed controller, and its result is compared to a theoretically derived desired joint angle trajectory. This comparison shows that there exists a unique solution of the desired joint angle trajectory when an initial pose of the manipulator and a desired end-point trajectory on the constraint surface are given, even under the existence of holonomic constraint and joint redundancy..
51. Akihiro Kawamura, Kenji Tahara, Ryo Kurazume, Tsutomu Hasegawa, Robust manipulation for temporary lack of sensory information by a multi-fingered hand-arm system, 2011 IEEE/RSJ International Conference on Intelligent Robots and Systems: Celebrating 50 Years of Robotics, IROS'11 IROS'11 - 2011 IEEE/RSJ International Conference on Intelligent Robots and Systems: Celebrating 50 Years of Robotics, https://doi.org/10.1109/IROS.2011.6048102, 4201-4206, 2011, This paper proposes a novel vision-based grasping and manipulation scheme of a multi-fingered hand-arm system robust for a temporary lack of sensory information. Visual information is one of the fundamental components for reliable grasping and manipulation by a multi-fingered hand-arm system. However, in case that visual information such as position and attitude of an object comes to be unavailable due to the occlusion or if the object goes out-of-sight temporarily, unstable and unfavorable behavior is often induced. The proposed method, which utilizes the stable grasping control and the concept of virtual frame, enables to grasp and manipulate an object stably even if the visual information becomes suddenly and temporarily unavailable during manipulation. Firstly, a dynamical model of object grasping using a multi-fingered hand-arm system is formulated. Next, a new control scheme for robust object grasping and manipulation using the virtual frame is proposed. Finally, numerical simulations are performed to verify the usefulness of the proposed method..
52. K. Tahara and H. Kino, Reaching movements of a redundant musculo-skeletal arm: Acquisition of an adequate internal force by iterative learning and its evaluation through a dynamic damping ellipsoid, Advanced Robotics, 24, 5-6, 783-818, 2010.04.
53. Kenji Tahara, Hitoshi Kino, Reaching movements of a redundant musculoskeletal arm
Acquisition of an adequate internal force by iterative learning and its evaluation through a dynamic damping ellipsoid, Advanced Robotics, https://doi.org/10.1163/016918610X493615, 24, 5-6, 783-818, 2010.04, This paper presents a proposal of an iterative learning control method for a musculoskeletal arm to acquire adequate internal force in order to realize human-like natural movements. Additionally, a dynamic damping ellipsoid at the end-point is introduced to evaluate internal forces obtained through the iterative learning scheme. Our previous works presented that a human-like smooth reaching movement using a musculoskeletal redundant arm model can be achieved by introducing a nonlinear muscle model and 'the virtual spring-damper hypothesis'. However, to date, the internal forces have been determined heuristically. As described in this paper, to determine internal forces more systematically, an iterative learning control method is used for acquisition of an adequate dynamic damping ellipsoid according to a given task. It is presented that the learning control method can perform effectively to realize given tasks, even though strong nonlinear characteristics of the muscles exist. After acquiring a given task, the dynamic damping ellipsoid is introduced to evaluate the relation between a damping effect generated by the acquired internal forces and a trajectory of the end-point. Some numerical simulations are performed and the usefulness of the learning control strategy, despite strong nonlinearity, is demonstrated through these results..
54. S. Arimoto, M. Sekimoto and K. Tahara, What does the central nervous system or computer learn through exercises of multi-joint movement, Journal of Robotics, 10.1155/2010/217867, 2010.03.
55. Kazuya Matsuo, Kouji Murakami, Katsuya Niwaki, Tsutomu Hasegawa, Kenji Tahara, Ryo Kurazume, A tactile sensing for estimating the position and orientation of a joint-axis of a linked object, 23rd IEEE/RSJ 2010 International Conference on Intelligent Robots and Systems, IROS 2010 IEEE/RSJ 2010 International Conference on Intelligent Robots and Systems, IROS 2010 - Conference Proceedings, https://doi.org/10.1109/IROS.2010.5649899, 1884-1889, 2010, This paper describes a tactile sensing to estimate the position and orientation of a joint-axis of a linked object. This tactile sensing is useful when a multi-jointed multi-fingered robotic hand manipulates a tool which has a joint. This estimation requires sensing of the location of a contact point and the direction of an edge of the tool as contact information measured by a robotic fingertip. A conventional hard fingertip with a force sensor can measure only the location of a contact point. In contrast, we have already developed a robotic fingertip with a force sensor and a soft skin, and it can measure not only the location of a contact point but also the direction of an edge of an object. The estimation of a joint-axis of a linked object is demonstrated by using the soft fingertip..
56. Hitoshi Kino, Shiro Kikuchi, Kenji Tahara, Decision method of internal force for sensorless positioning of musculoskeletal system, 5th International Conference on Broadband Wireless Computing, Communication and Applications, BWCCA 2010 Proceedings - 2010 International Conference on Broadband, Wireless Computing Communication and Applications, BWCCA 2010, https://doi.org/10.1109/BWCCA.2010.163, 731-736, 2010, In a musculoskeletal structure, a set of internal force among muscles plays an important role. The internal force has the particular potential field. Using this property, we can control the position of a musculoskeletal system without any sensory feedback. However, the internal force can not be selected uniquely due to the muscular redundancy. This paper proposes a decision method of the internal force for the feedforward positioning. The usefulness of the proposed method is demonstrated through numeral analysis..
57. Kenji Tahara, Suguru Arimoto, Morio Yoshida, Dynamic object manipulation using a virtual frame by a triple soft-fingered robotic hand, 2010 IEEE International Conference on Robotics and Automation, ICRA 2010 2010 IEEE International Conference on Robotics and Automation, ICRA 2010, https://doi.org/10.1109/ROBOT.2010.5509372, 4322-4327, 2010, This paper proposes a novel object manipulation method to regulate the position and attitude of an object in the task space with dynamic stability by using a triple soft-fingered robotic hand system. In our previous works, a dynamic object grasping method without use of any external sensing, called "the Blind Grasping", has been proposed. Although stable grasping in a dynamic sense has been realized by the method, a simultaneous object position and attitude control has not yet been treated, so far. In this paper, instead of using any information of the real object position and attitude, virtual data of object position and attitude are introduced by defining a virtual frame. By using the virtual information, a control signal to regulate the virtual object position and attitude without use of any external sensing is designed. The usefulness of our proposed control method even under the existence of nonholonomic rolling constraints is illustrated through a numerical simulation result..
58. Kenji Tahara, Keigo Maruta, Motoji Yamamoto, External sensorless dynamic object manipulation by a dual soft-fingered robotic hand with torsional fingertip motion, 2010 IEEE International Conference on Robotics and Automation, ICRA 2010 2010 IEEE International Conference on Robotics and Automation, ICRA 2010, https://doi.org/10.1109/ROBOT.2010.5509816, 4309-4314, 2010, This paper proposes a novel object manipulation method by using a dual soft-fingered robotic hand system, in which each fingertip has a torsional joint. By using the torsional motion of the fingertips, a novel 3-dimensional dynamic object manipulation without use of any external sensing can be achieved even though the hand system has only two fingers. Firstly, our proposed system, which includes contact models between each fingertip and surfaces of an object, is modeled. A rolling contact between each fingertip and the object surfaces can be allowed because our proposed system has soft and deformable hemispheric fingertips. Moreover, a torsional contact model between each fingertip and the object surfaces is newly proposed. It is based on an assumption that the torsional motion induces an elastic strain potential. Secondly, a dynamic object manipulation control method is designed. The control signal is composed of four parts, the one is for grasping the object stably, the second one is for controlling a position of the object, the third one is for controlling an attitude of the object, and the last one is for the torsional fingertip motion. A numerical simulation based on our model is performed, and a manipulation experiment by using our developed setup is performed. The usefulness of our proposed method is demonstrated through these results..
59. Kenji Tahara, Hitoshi Kino, Iterative learning control for a redundant musculoskeletal arm
Acquisition of adequate internal force, 23rd IEEE/RSJ 2010 International Conference on Intelligent Robots and Systems, IROS 2010 IEEE/RSJ 2010 International Conference on Intelligent Robots and Systems, IROS 2010 - Conference Proceedings, https://doi.org/10.1109/IROS.2010.5650071, 234-240, 2010, This paper presents a proposal of an iterative learning control method for a musculoskeletal arm to acquire adequate internal force to realize human-like natural movements. Additionally, a dynamic damping ellipsoid at the end-point is introduced to evaluate internal forces obtained through the iterative learning. In our previous works, we have presented that a human-like smooth reaching movement using a musculoskeletal redundant arm model can be obtained by introducing a nonlinear muscle model and "the Virtual spring-damper hypothesis". However, the internal forces have been determined heuristically, so far. In this paper, an iterative learning control method is used for acquisition of an adequate dynamic damping ellipsoid according to a given task, in order to determine internal forces more systematically. It is presented that the learning control scheme can perform effectively to realize given desired tasks, even under the existence of strong nonlinear characteristics of the muscles. After acquiring a given task, the dynamic damping ellipsoid is introduced to evaluate the relation between a damping effect generated by the acquired internal forces and a trajectory of the end-point. Some numerical simulations are performed and the usefulness of the learning control strategy, despite strong nonlinearity of the muscles, is demonstrated through these results..
60. Kenji Tahara, Hitoshi Kino, Iterative learning scheme for a redundant musculoskeletal arm
Task space learning with joint and muscle redundancies, 5th International Conference on Broadband Wireless Computing, Communication and Applications, BWCCA 2010 Proceedings - 2010 International Conference on Broadband, Wireless Computing Communication and Applications, BWCCA 2010, https://doi.org/10.1109/BWCCA.2010.168, 760-765, 2010, This paper proposes an iterative learning control scheme in a task space for a musculoskeletal redundant planar arm model to accomplish a desired time dependent trajectory tracking task. In our previous work, we have proposed the iterative learning control scheme in a muscle length space for a two-link six-muscle planar arm model. This proposed method has been effective for performing a time dependent desired trajectory tracking task even under the existence of strong nonlinearity of muscles dynamics. However in the previous work, a muscle redundancy only treated, and a joint redundancy has not yet been considered. Also a solution of inverse kinematics from the task space to the joint angle space must be calculated in real-time. This paper considers both muscle and joint redundancies, and the task space iterative learning scheme is newly exploited. By introducing the task space controller, it is unnecessary to compute inverse kinematics from the task space to the joint space in real-time. Firstly, a three-joint nine-muscle redundant planar arm is modeled. Secondly, the task space iterative learning control signal is designed. Then finally, the effectiveness of our proposed controller is illustrated through some numerical simulation results even under the existence of both redundancies and the nonlinear muscle dynamics..
61. Akihiro Kawamura, Kenji Tahara, Ryo Kurazume, Tsutomu Hasegawa, Sensory feedback attitude control for a grasped object by a multi-fingered hand-arm system, 2010 IEEE International Conference on Robotics and Biomimetics, ROBIO 2010 2010 IEEE International Conference on Robotics and Biomimetics, ROBIO 2010, https://doi.org/10.1109/ROBIO.2010.5723559, 1542-1548, 2010, This paper proposes a novel method for stable grasping and attitude regulation of an object using a multi-fingered hand-arm system. The proposed method is based on a simple sensory-feedback control using the information of an object attitude, and any mathematically complicated computation, such as calculation of inverse dynamics and kinematics, are not required. In addition, the stability of the overall system applied this method is verified. Firstly, nonholonomic rolling constraints between a multi-fingered hand-arm system and an object are formulated. Then, a novel control method for stable grasping and attitude regulation of the grasped object is proposed. It is assumed that information of the attitude of the object is available in real time by external sensors, such as vision, force, tactile sensors, and so on. Next, the stability of the overall system is verified by analyzing the closed-loop dynamics. Finally, it is demonstrated through numerical simulations that our proposed method enables to grasp the object with arbitrary shape, and regulate the attitude of the object stably..
62. Kenji Tahara, Suguru Arimoto, Morio Yoshida, Dynamic force/torque equilibrium for stable grasping by a triple robotic fingers system, 2009 IEEE/RSJ International Conference on Intelligent Robots and Systems, IROS 2009 2009 IEEE/RSJ International Conference on Intelligent Robots and Systems, IROS 2009, https://doi.org/10.1109/IROS.2009.5354563, 2257-2263, 2009.12, This paper proposes a stable object grasping method to realize dynamic force/torque equilibrium by using a triple robotic fingers system with soft and deformable hemispherical fingertips. In the authors' previous works, "Blind Grasping" control scheme, which realizes stable object grasping without use of any external sensing such as vision, force, or tactile sensing in the case of using a pair of robot fingers, has been proposed. This control methodology is based on a unique configuration of human hand, called "Fingers-Thumb Opposability". In this paper, a ternary finger in addition to a pair of fingers is introduced not only to expand a stable region of grasping, but also to enhance dexterity and versatility of the multi-fingered robotic hand system. To this end, a "Blind Grasping" manner is modified in order to install it in the triple fingers system. First, dynamics of the triple robotic fingers system and a grasped object with considering rolling constraints is modeled, and a control input based on the blind grasping manner is designed. Next, the closed-loop dynamics is derived and a stability analysis is shown briefly. Finally, its usefulness is discussed through numerical simulation results..
63. Akihiro Kawamura, Kenji Tahara, Ryo Kurazume, Tsutomu Hasegawa, Dynamic grasping for an arbitrary polyhedral object by a multi-fingered hand-arm system, 2009 IEEE/RSJ International Conference on Intelligent Robots and Systems, IROS 2009 2009 IEEE/RSJ International Conference on Intelligent Robots and Systems, IROS 2009, https://doi.org/10.1109/IROS.2009.5354174, 2264-2270, 2009.12, This paper proposes a novel control method for stable grasping using a multi-fingered hand-arm system with soft hemispherical finger tips. The proposed method is simple but easily achieves stable grasping of an arbitrary polyhedral object using an arbitrary number of fingers. Firstly, we formulate nonholonomic constraints between a multi-fingered hand-arm system and an object constrained by rolling contact with finger tips, and derive a condition for stable grasping by stability analysis. A new index for evaluating the possibility of stable grasping is proposed and efficient initial relative positions between finger tips and the object for realizing stable grasping are analyzed. The stability of the proposed system and the validity of the index are verified through numerical simulations..
64. Morio Yoshida, Suguru Arimoto, Kenji Tahara, Pinching 2D object with arbitrary shape by two robot fingers under rolling constraints, 2009 IEEE/RSJ International Conference on Intelligent Robots and Systems, IROS 2009 2009 IEEE/RSJ International Conference on Intelligent Robots and Systems, IROS 2009, https://doi.org/10.1109/IROS.2009.5354836, 1805-1810, 2009.12, Modeling of pinching an object with arbitrary shape by a pair of robot fingers with hemispherical ends in a horizontal plane is proposed in a mathematical and computational manner. Since the curvature of an object contour with an arbitrary curve is variable according to the change of the contact point between the object surface and the rigid finger tip, the arclength paremeter "s" explicitly appears in the overall fingers-object dynamics. It is shown that the overall fingers-object system should be accompanied with the first-order differential equation of the parameter "s" that includes the curvatures of both the object contour and finger-tip curve. A control input, which is of the same category as the control input called "blind grasping" appeared in our former papers, is utilized for the realization of stable grasp. The control input does neither need to use the kinematic information of the object nor use any external sensing. Finally, numerical simulations are carried out in order to confirm the effectiveness of our proposed model and control input..
65. Kazuya Matsuo, Kouji Murakami, Tsutomu Hasegawa, Kenji Tahara, Ryo Kurazume, Segmentation method of human manipulation task based on measurement of force imposed by a human hand on a grasped object, 2009 IEEE/RSJ International Conference on Intelligent Robots and Systems, IROS 2009 2009 IEEE/RSJ International Conference on Intelligent Robots and Systems, IROS 2009, https://doi.org/10.1109/IROS.2009.5354069, 1767-1772, 2009.12, This paper proposes a segmentation method of human manipulation task based on measurement of contact force imposed by a human hand on a grasped object. We define an index measure for segmenting a human manipulation task into primitives. The indices are calculated from the set of the contact forces measured at all the contact points during a manipulation task. Then, we apply the EM algorithm to the set of the indices in order to segment the manipulation task into primitives. These primitives are mapped onto the robotic hand to impose appropriate contact forces on a grasped object. In the experiments, manipulation tasks performed in daily human life have been successfully segmented..
66. S. Arimoto, M. Yoshida, M. Sekimoto and K. Tahara, Modeling and control of 2-D grasping of an object with arbitrary shape under rolling contact, SICE Journal of Control, Measurement and System Integration, 2, 6, 379-386, 2009.06.
67. S. Arimoto, M. Yoshida, M. Sekimoto and K. Tahara, A Riemannian-geometry approach for modeling and control of dynamics of object manipulation under constraints, Journal of Robotics, 10.1155/2009/892801, 2009.03.
68. K. Tahara, S. Arimoto, M. Sekimoto and Z.W. Luo, On control of reaching movements for musculo-skeletal redundant arm model, Applied Bionics and Biomechanics, 6, 1, 57-72, 2009.03.
69. Hitoshi Kino, Toshiaki Yahiro, Shohei Taniguchi, Kenji Tahara, Sensorless position control using feedforward internal force for completely restrained parallel-wire-driven systems, IEEE Transactions on Robotics, https://doi.org/10.1109/TRO.2009.2013495, 25, 2, 467-474, 2009.03, Generally, point-to-point control for a completely restrained (CR) parallel-wire-driven system requires a balancing internal force to prevent slackening of wires, along with a feedback term based on some displacement sensor. This paper specifically describes CR systems' internal force properties, then presents the possibility of motion convergence at a desired position when the internal force balancing at a position is given as sensorless feedforward input. Subsequently, we use the property of internal force positively for sensorless position control. This positioning method is applicable for low-cost manipulation, which does not require high accuracy, and for emergency positioning of systems when sensors malfunction..
70. S. Arimoto, M. Yoshida, M. Sekimoto and K. Tahara, A Riemannian-geometry approach for control of robotic systems under constraints, SICE Journal of Control, Measurement and System Integration, 2, 2, 107-116, 2009.02.
71. H. Kino, T. Yahiro, S. Taniguchi and K. Tahara, Sensorless position control using feedforward internal force for completely restrained parallel-wiredriven systems, IEEE Transactions on Robotics, 25, 2, 467-474, 2009.02.
72. Kenji Tahara, Suguru Arimoto, Masahiro Sekimoto, Zhi Wei Luo, On control of reaching movements for musculo-skeletal redundant arm model, Applied Bionics and Biomechanics, https://doi.org/10.1080/11762320902789848, 6, 1, 11-26, 2009.01, This paper focuses on a dynamic sensory-motor control mechanism of reaching movements for a musculo-skeletal redundant arm model. The formulation of a musculo-skeletal redundant arm system, which takes into account non-linear muscle properties obtained by some physiological understandings, is introduced and numerical simulations are perfomed. The non-linear properties of muscle dynamics make it possible to modulate the viscosity of the joints, and the end point of the arm converges to the desired point with a simple task-space feedback when adequate internal forces are chosen, regardless of the redundancy of the joint. Numerical simulations were performed and the effectiveness of our control scheme is discussed through these results. The results suggest that the reaching movements can be achieved using only a simple task-space feedback scheme together with the internal force effect that comes from non-linear properties of skeletal muscles without any complex mathematical computation such as an inverse dynamics or optimal trajectory derivation. In addition, the dynamic damping ellipsoid for evaluating how the internal forces can be determined is introduced. The task-space feedback is extended to the 'virtual spring-damper hypothesis' based on the research by Arimoto et al. (2006) to reduce the muscle output forces and heterogeneity of convergence depending on the initial state and desired position. The research suggests a new direction for studies of brain-motor control mechanism of human movements..
73. Suguru Arimoto, Morio Yoshida, Masahiro Sekimoto, Kenji Tahara, A riemannian-geometry approach for dynamics and control of object manipulation under constraints, 2009 IEEE International Conference on Robotics and Automation, ICRA '09 2009 IEEE International Conference on Robotics and Automation, ICRA '09, https://doi.org/10.1109/ROBOT.2009.5152414, 1683-1690, 2009, A Riemannian-geometry approach for control and stabilization of dynamics of object manipulation under holonomic or non-holonomic (but Pfaffian) constraints is presented. First, position/force hybrid control of an endeffector of a multijoint redundant (or nonredundant) robot under a nonholonomic constraint is reinterpreted in terms of "submersion" in Riemannian geometry. A force control signal constructed in the image space spanned from the constraint gradient can be regarded as a lifting in the direction orthogonal to the kernel space. By means of the Riemannian distance on the constraint submanifold, stability on a manifold for a redundant system under holonomic constraints is discussed. Second, control and stabilization of dynamics of two-dimensional object grasping and manipulation by using a pair of multi-joint robot fingers are tackled, when a rigid object is given with arbitrary shape. Then, it is shown that rolling contact constraint induce the Euler equation of motion in an implicit function form, in which constraint forces appear as wrench vectors affecting on the object. The Riemannian metric can be introduced in a natural way on a constraint submanifold induced by rolling contacts. A control signal called "blind grasping" is defined and shown to be effective in stabilization of grasping without using the details of information of object shape and parameters or external sensing. The concept of stability of the closedloop system under constraints is renewed in order to overcome the degrees-of-freedom redundancy problem. An extension of Dirichlet-Lagrange's stability theorem to a system of DOFredundancy under constraints is presented by using a Morse- Lyapunov function..
74. H. Kino, S. Kikuchi, T. Yahiro, Kenji Tahara, Basic study of biarticular muscle's effect on muscular internal force control based on physiological hypotheses, 2009 IEEE International Conference on Robotics and Automation, ICRA '09 2009 IEEE International Conference on Robotics and Automation, ICRA '09, https://doi.org/10.1109/ROBOT.2009.5152196, 4195-4200, 2009, In a musculoskeletal structure, the internal force among muscles plays an important role. Changing the internal force enables to control not only joint angles but also impedance, so that vertebrate animals can produce a motion according to a situation. Focusing on a musculoskeletal system with two links and six muscles, this paper investigate the effect of biarticular muscles when feedforward position control is inputted. This control gives the constant internal force balancing at desired posture as feedforward input, based on the EP hypothesis in physiology. From the result, we point out that the biarticular muscles can reduce the convergent time of the motion, and theyalso can stabilize the system..
75. Morio Yoshida, Suguru Arimoto, Kenji Tahara, Manipulation of 2D object with arbitrary shape by robot finger under rolling constraint, ICROS-SICE International Joint Conference 2009, ICCAS-SICE 2009 ICCAS-SICE 2009 - ICROS-SICE International Joint Conference 2009, Proceedings, 695-699, 2009, Contact of two contours of a pinched object and a robot finger tip, with arbitrary shape, is expressed in terms of differential geometry. The overall finger-object dynamics with rolling and contact constraints is derived as Euler-Lagrange' equation of motion and the first differential equation with curvatures of the contours is derived for updating the length parameters. Despite the complicated mathematical structure, a control input signal is proposed, which can be constructed without using object geometrical information or external sensing, and it is shown that it is effective to stabilize rotation of the object. Consequently, numerical simulations are carried out in order to demonstrate the practicality of the proposed model and control signal..
76. Kazuya Matsuo, Kouji Murakami, Tsutomu Hasegawa, Kenji Tahara, Ryo Kurazume, Measurement of static constraints imposed by a human hand on a grasped object, 2009 International Conference on Advanced Robotics, ICAR 2009 2009 International Conference on Advanced Robotics, ICAR 2009, 2009, This paper proposes a method of directly measuring static constraints imposed by a human hand on a grasped object.Based on the analysis of the demonstration data of the human grasp, the static constraints are expressed as a combination of frictional force and normal force generated by the human hand.The static constraints are an important property to be mapped to robotic hands in the programming-by-demonstration.Measured static constraints are to be generated to robotic hands to establish the stable grasp.In the experiments, we have successfully measured the static constraints appeared in various different grasps used in the daily human life..
77. S. Arimoto, M. Yoshida, M. Sekimoto, Kenji Tahara, J. H. Bae, Modeling and control for 2-D grasping of an object with arbitrary shape under rolling contact, IFAC-PapersOnLine, https://doi.org/10.3182/20090909-4-JP-2010.00066, 42, 16, 383-388, 2009, Modeling, control, and stabilization of dynamics of two-dimensional object grasping by using a pair of multi-joint robot fingers are investigated under rolling contact constraints and arbitrariness of the geometry of the object and fingerends. First, a fundamental testbed problem of modeling and control of rolling motion between 2-D rigid bodies with arbitrary shape is treated under the assumption that the two contour curves coincide at the contact point and share the same tangent. The rolling constraint induces the Euler equation of motion that is parameterized by a common arclength parameter and constrained onto the kernel space as an orthogonal complement to the image space spanned from the constraint gradient. By extending the analysis to the problem of stable grasp of a 2D-object with arbitrary shape, the Euler- Lagrange equation of motion of the overall fingers/object system parametrized by arclength parameters is derived, and shown to be accompanied with a couple of first-order differential equations that express evolutions of contact points in terms of the second fundamental form. Further, it is shown that rolling contact constraints are integrable in the sense of Frobenius and hence regarded as being holonomic. A control signal called "blind grasping" is defined and shown to be effective in stabilization of grasping without using the details of object shape and parameters or external sensing..
78. Akihiro Kawamura, Kenji Tahara, Ryo Kurazume, Tsutomu Hasegawa, Simple orientation control of an object by regrasping using a dual-arm manipulator with multi-fingered hands, 2009 International Conference on Advanced Robotics, ICAR 2009 2009 International Conference on Advanced Robotics, ICAR 2009, 2009, This paper proposes a novel control method for stable object grasping and orientation control using a dual-arm manipulator with multi-fingered hands. The control signal of the proposed method is simple but it can easily achieve stable grasping without external sensors and an orientation control of a grasped object. Firstly, holonomic constraints between a dual-arm manipulator with multi-fingered hands and the object surfaces are formulated, and the stability of the system is discussed through its convergence analysis. Next, it is shown that the relationship between a final orientation of an object and initial contact positions of finger tips becomes quasi-linear. Using this quasi-linear relationship, an orientation control method utilizing regrasping of the object is derived. It is verified that the proposed method enables to perform simple orientation control of the object without real-time external sensing through numerical simulations..
79. Kenji Tahara, Suguru Arimoto, Morio Yoshida, Dynamic object grasping by a triple-fingered robotic hand, 2008 IEEE/RSJ International Conference on Intelligent Robots and Systems, IROS 2008 IEEE/RSJ International Conference on Intelligent Robots and Systems, IROS, https://doi.org/10.1109/IROS.2008.4650702, 2685-2690, 2008, This paper deals with dynamic object grasping and position control by using a triple-fingered robotic hand with hemispherical soft finger tips. In the authors' previous works, a dynamic object grasping method by using a pair of robotic fingers, called "Blind Grasping", which does not need to use any external sensing, was proposed. However, it is so far assumed that spinning motion around the opposite axis for the object does not occur during the overall movement, because there are only two opposite fingers and thereby the spinning is uncontrollable. By introducing a surplus finger in addition to a pair of robotic fingers, this spinning can be inhibited and it becomes controllable. In this paper, a triple-fingered robotic hand system with nonholonomic constraints is modeled, and a control input to realize stable grasping with object position control is proposed. Its usefulness and effectiveness are illustrated through some numerical simulation results..
80. Kenji Tahara, Suguru Arimoto, Masahiro Sekimoto, Morio Yoshida, Zhi Wei Luo, On iterative learning control for simultaneous force/position trajectory tracking by using a 5 D.O.F. robotic thumb under non-holonomic rolling constraints, 2008 IEEE International Conference on Robotics and Automation, ICRA 2008 2008 IEEE International Conference on Robotics and Automation, ICRA 2008, https://doi.org/10.1109/ROBOT.2008.4543606, 2611-2616, 2008, This paper proposes an iterative learning control method for simultaneous force/position tracking tasks by using a 5 D.O.F. robotic thumb under non-holonomic rolling constraints. In our previous works, "blind touching", which is defined as a point-to-point control scheme for the robot to realize a desired contact position and a contact force simultaneously without any external sensing, have proposed. In this paper, an iterative learning control manner to realize a desired continuous trajectory of the center of the contact point together with a desired contact force on the task plane is proposed. The usefulness of this learning control method is demonstrated by showing results of computer simulations..
81. Masaki Onishi, Zhi Wei Luo, Tadashi Odashima, Shinya Hirano, Kenji Tahara, Toshiharu Mukai, Generation of human care behaviors by human-interactive robot RI-MAN, 2007 IEEE International Conference on Robotics and Automation, ICRA'07 2007 IEEE International Conference on Robotics and Automation, ICRA'07, https://doi.org/10.1109/ROBOT.2007.363950, 3128-3129, 2007.11, Recently, active researches have been performed to increase a robot's intelligence so as to realize the dexterous tasks in complex environment such as in the street or homes. However, since the skillful human-like task ability is so difficult to be formulated for the robot, not only the analytical and theoretical control researches but also the direct human motion mimetic approach is necessary. In this paper, we propose that to realize the environmental interactive tasks, such as human care tasks, it is insufficient to replay the human motion along. We show a novel motion generation approach to integrate the cognitive information into the mimic of human motions so as to realize the final complex task by the robot..
82. Kenji Tahara, Suguru Arimoto, Zhi Wei Luo, Morio Yoshida, On control for "blind touching" by human-like thumb robots, 2007 IEEE International Conference on Robotics and Automation, ICRA'07 2007 IEEE International Conference on Robotics and Automation, ICRA'07, https://doi.org/10.1109/ROBOT.2007.363051, 592-598, 2007, Human can pinch or grasp and manipulate an object stably and dexterously. Accomplishment of such tasks is contributed from human hand's configuration, called "Fingers-thumb opposability". This opposability of the thumb against other digits is specific and granted to only human among primates. When we use a cell phone, or change a TV's channel using a remote controller, we grasp it by a palm and digits other than the thumb, and push buttons using the thumb quickly, without looking the buttons. These kinds of thumb's movement seem to be one of the most intelligent movements in a human. Therefore, execution of such touching tasks without visual or tactile sensing is called in this paper "Blind Touching". The goal of this research is to realize human-like "Blind Touching" by means of a 5 D.O.F. thumb robot model with soft and hemispherical finger-tip. To do this, we formulate a simultaneous contact position and touching force control by using 3-Dimensional rolling contact with the task plane. First, dynamics of the 5 D.O.F. thumb robot model with hemispherical soft finger-tip under rolling constraints is derived. Then, a sensory-motor control law without vision, force or tactile sensing is proposed. Some numerical simulations show that the desired contact position and touching force can be attained by the proposed control scheme. A theoretical proof of convergence to the desired state is also presented..
83. Kenji Tahara, Zhi Wei Luo, Suguru Arimoto, On control mechanism of human-like reaching movements with musculo-skeletal redundancy, 2006 IEEE/RSJ International Conference on Intelligent Robots and Systems, IROS 2006 2006 IEEE/RSJ International Conference on Intelligent Robots and Systems, IROS 2006, https://doi.org/10.1109/IROS.2006.281931, 1402-1409, 2006, This paper focuses on a sensory-motor control mechanism in human reaching movements from the perspective of robotics. By formulating a musculo-skeletal redundant system which takes into account a nonlinear muscle property and performing numerical simulations, we suggest that the human-like reaching movements can be realized by using only simple task-space feedback scheme together with the internal force effect coming from nonlinear property of muscles without any complex mathematical computation such as an inverse dynamics or some optimal trajectory derivation. Firstly, we introduce both kinematics and dynamics of a three-link serial manipulator with six monoarticular muscles and three biarticular muscles model whose movements are limited within a horizontal plane. Secondly, the nonlinear muscle property coming from a physiological study based on Hill's muscle model, is taken into consideration. This nonlinearity makes it possible to modulate the damping effect in joint-space by considering the internal force generated by the redundant muscles. By utilizing this feature, the end-point converges to the desired point using only simple task-space feedback control scheme, even thought the system owns both the joint and muscle redundancies. Finally, we illustrate numerical simulations to show the effectiveness of the control scheme, and suggest one of the direction to study brain-motor control mechanism of human movements..
84. Kenji Tahara, Zhi Wei Luo, On dynamic control mechanisms of redundant human musculo-skeletal system, Advances in Robot Control: From Everyday Physics to Human-Like Movements, https://doi.org/10.1007/978-3-540-37347-6_11, 217-247, 2006, This chapter deals with modeling of human-like reaching and pinching movements. For the reaching movements, we construct a two-link planar arm model with six redundant muscles. A simple task-space feedback control scheme, taking into account internal forces induced by the redundant and nonlinear muscles, is proposed for this model. Numerical simulations show that our sensory-motor control can realize human-like reaching movements. The effect of gravity is also studied here and a method for the gravity compensation on the muscle input signal level is introduced. The stability of this method is proved and its effectiveness is shown through numerical simulations. For the pinching movements, realized by the index finger and the thumb, the co-contraction between the flexor and extensor digitorum muscles is analyzed. It is shown that an internal force term can be generated by the redundant muscles to modulate a damping factor in the joint space. Numerical simulations show that the co-contraction of each digitorums makes it possible to realize human-like pinching movements. Our results suggest that the central nervous system (CNS) does not need to calculate complex mathematical models based on the inverse dynamics or on the planning of optimal trajectories. Conversely, the human motor functions can be realized through the sensory-motor control by exploiting the passivity, nonlinearity and the redundancy of the musculo-skeletal systems..
85. K. Tahara, Z.W. Luo, S. Arimoto and H. Kino, Sensory-motor control mechanism for reaching movements of a redundant musculo-skeletal arm, Journal of Robotic Systems, 22, 11, 639-651, 2005.11.
86. Kenji Tahara, Zhi Wei Luo, Suguru Arimoto, Hitoshi Kino, Sensory-motor control mechanism for reaching movements of a redundant musculo-skeletal arm, Journal of Field Robotics, https://doi.org/10.1002/rob.20089, 22, 11, 639-651, 2005.11, This paper studies the human arm's sensory-motor control mechanism in reaching movements. First, we formulate both the kinematics and dynamics of a two-link planar arm model with six redundant muscles. The nonlinear muscle dynamics is modeled based on several biological understandings. We then show the stability of the overall system and perform some numerical simulations. By considering the internal forces induced by the redundant muscles, we show that the damping factors in each joint can be regulated, and as the result, it can realize humanlike quasistraight line reaching movements. In addition, we also propose the gravity compensation method at the muscle input level and present the result of numerical simulation to verify the usefulness of this method..
87. Kentaro Takagi, Zhi Wei Luo, Kinji Asaka, Kenji Tahara, Limited-angle motor using ionic polymer-metal composite, Proceedings of SPIE - The International Society for Optical Engineering, https://doi.org/10.1117/12.599503, 5759, 487-496, 2005.10, The essential motion of the ionic polymer-metal composite (IPMC) is bending, therefore some mechanisms are expected to transform from the bending to other required motions. Motivated by the motion of a spiral spring, we discovered that the bending of the ionic polymer could be directly transformed to the limited angle rotation. We introduce the model of the rotary actuator, which consists of mechanical, electrical and electromechanical dynamics. The motion of the rotary actuator is demonstrated in the experiment. The stationary properties are measured and the parameters of the dynamical model are identified, which are also validated by experiments..
88. Kenji Tahara, Zhi Wei Luo, Suguru Arimoto, Hitoshi Kino, Sensory-motor control of a muscle redundant arm for reaching movements - Convergence analysis and gravity compensation, IEEE IRS/RSJ International Conference on Intelligent Robots and Systems, IROS 2005 2005 IEEE/RSJ International Conference on Intelligent Robots and Systems, IROS, https://doi.org/10.1109/IROS.2005.1545411, 2870-2875, 2005, -In this paper, we study the sensory motor control mechanism in human reaching movements by considering the redundant muscle dynamics. We first formulate the kinematics and dynamics of a two-link arm model with six muscles, and introduce the nonlinear muscle dynamics based on the biological understanding. Secondly, we show the stability of the system by using intrinsic muscle characteristics and La Salle's invariance theorem. From this result and the numerical simulations, we propose that the reaching movement can be regulated by the internal forces of the redundant muscles, in detail, the muscle's internal forces can be used to control the damping of the joints. In addition, human can compensate the gravity by using antigravity muscles. To realize this effect in the arm, we propose the gravity compensation method at the muscle input level from the viewpoint of robotics. We present the result of numerical simulation to verify the usefulness of this compensation method..
89. Kenji Tahara, Zhi Wei Luo, Suguru Arimoto, Hitoshi Kino, Task-space feedback control for a two-link arm driven by six muscles with variable damping and elastic properties, 2005 IEEE International Conference on Robotics and Automation Proceedings of the 2005 IEEE International Conference on Robotics and Automation, https://doi.org/10.1109/ROBOT.2005.1570123, 2005, 223-228, 2005, It is well-known that a human musculo-skeletal body is redundant in terms of both kinematics and dynamics. The former means that the degree of freedom in joint space is larger than that in task space, and the latter means that a joint is driven by a number of muscles. All human skillful movements can be performed by using both redundancies. However, these redundancies induce the underlying ill-posedness problem that each joint angle and muscle's output forces cannot be uniquely determined. These ill-posedness problems are known as "Bernstein's problem" and are important to understand how human multi-joint movements are produced. In this study, we address the latter redundancy problem on how muscle's output forces can be determined from the viewpoint of robotics. In this paper, we consider a reaching movement by means of a two-link planar arm with six muscles and show that both damping and elastic properties coming from nonlinear dynamics of the muscles play a crucial role. By using a simple task space feedback control input together with an additional term to control the internal force to regulate damping and elasticity in joint space, we show some simulation results which exhibit human-like quasi-straight line movement..
90. S. Arimoto, K. Tahara and J.-H. Bae, A stability theory on a manifold: Concurrent realization of grasp and orientation control of an object by a pair of robot fingers, Robotica, 21, 2, 163-178, 2003.03.
91. S. Arimoto, M. Yoshida, J.-H. Bae and K. Tahara, Dynamic force/torque balance of 2D polygonal objects by a pair of rolling contacts and sensorymotor coordination, Journal of Robotic Systems, 20, 9, 517-537, 2003.09.
92. Fumihiko Asano, Zhi Wei Luo, Masaki Yamakita, Kenji Tahara, Shigeyuki Hosoe, Bio-mimetic control for whole arm cooperative manipulation, Conference Proceedings - IEEE International Conference on Systems, Man and Cybernetics, 1, 704-709, 2004.12, This paper studies modeling and biomimetic control of a 3D 8-dof whole arm cooperative manipulation system using sensitive skin. The control law is designed based on integration of voluntary movement and reflex considering the system's redundancy. The voluntary task for holding the object is realized by impedance control at four contact points with the object using the contact force information from the sensitive skin. The reflection on the other hand is introduced as a regulation problem of the direction between the points of end-effectors and elbows. We then investigate the exact solutions for the combined motion and their solvable conditions. The validity of the proposed method is investigated by numerical simulations..
93. Kenji Tahara, Z. W. Luo, T. Odashima, M. Onishi, S. Hosoe, A. Kato, Dynamic control and simulation of human musculo-skeletal model, SICE Annual Conference 2004 SICE Annual Conference 2004, 1373-1376, 2004.12, In this paper, we propose a dynamic human motion simulator to clarify and obtain the natural movement as human carries out. This system consists of a 3D motion capturing system, which has 6 high-speed cameras, 8 force plates, 10 3-axis accelerometers and 32 EMG sensors. To reconstruct the human's complex movement in VR space, a dynamic simulation model of human muscle-skeletal body is constructed. This model has 100 segments of born and has totally 105 D.O.F. in whole body, and also 300 muscles are included in this model. These muscles have the properties of stiffness, damping and contractive force generation. This platform makes it possible for construct human dynamic motion control functions more precisely and is thus useful for biomimetic robots. By using the super-redundant human body model, we are studying the brain motor control functions through the dynamic simulations..
94. Fumihiko Asano, Zhi Wei Luo, Kenji Tahara, Masaki Yamakita, Shigeyuki Hosoe, Modeling and control for whole arm dynamic cooperative manipulation, 2004 IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS) 2004 IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS), 4, 3282-3287, 2004.12, This paper studies modeling and bio-mimetic control of a 3D 8-dof whole arm cooperative manipulation system using sensitive skin. A sphere is considered here as a manipulated object. The control law is designed based on integration of voluntary and reflex movements considering the system's redundancy. The voluntary task for holding the object is realized by impedance control at the four contact points with the object using the contact force information from the sensitive skin. The reflection on the other hand is introduced as a regulation problem of the direction between the points of end-effectors and elbows. The solution for the redundant control is formulated and derived from the optimization point of view. The validity of the proposed method is investigated by numerical simulations..
95. S. Arimoto, Kenji Tahara, J. H. Bae, M. Yoshida, A stability theory of a manifold
Concurrent realization of grasp and orientation control of an object by a pair of robot fingers, Robotica, https://doi.org/10.1017/S026357470200468X, 21, 2, 163-178, 2003.01, This paper is concerned with a stability theory of motion governed by Lagrange's equation for a pair of multi-degrees of freedom robot fingers with hemi-spherical finger ends grasping a rigid object under rolling contact constraints. When a pair of dual two d.o.f. fingers is used and motion of the overall fingers-object system is confined to a plane, it is shown that the total degree of freedom of the fingers-object system is redundant for realization of stable grasping though there arise four algebraic constraints. To resolve the redundancy problem without introducing any other extra and artificial performance index, a concept of stability of motion starting from a higher dimensional manifold to a lower-dimensional manifold, expressing a set of states of stable grasp with prescribed contact force, is introduced and thereby it is proved in a rigorous way that stable grasp in a dynamic sense is realized by a sensory feedback constructed by means of measurement data of finger joint angles and the rotational angle of the object. Further, it is shown that there exists an additional sensory feedback that realizes not only stable grasp but also orientation control of the object concurrently. Results of computer simulation based on Baumgarte's method are presented, which show the effectiveness of the proposed concept and analysis..
96. J. H. Bae, Kenji Tahara, S. Nakamura, S. Arimoto, Computer simulation of grasping and object-manipulation by a pair of multi-degrees of freedom robot fingers, 2003 IEEE International Symposium on Computational Intelligence in Robotics and Automation, CIRA 2003 Proceedings - 2003 IEEE International Symposium on Computational Intelligence in Robotics and Automation Computational Intelligence in Robotics and Automation for the New Millennium, https://doi.org/10.1109/CIRA.2003.1222171, 3, 1219-1226, 2003.01, This paper is concerned with computer simulation of concurrent grasp and orientation control of an object with two parallel flat surfaces by a pair of multi-degrees of freedom robot fingers that have rigid hemispherical ends. Firstly, geometrical relationships in the overall fingers-object system are discussed through four algebraic constraints between the finger tips and surfaces of the object. Then, differential algebraic equations expressing dynamics of the overall system are derived. Secondly, a sensory feedback signal for concurrent grasp and orientation control of the object is proposed and a full description of matrix form for numerically solving the closed-loop differential algebraic equation of the overall fingers-object system on the basis of the CSM (constraint stabilization method) is presented. Thirdly, simulation results of grasping and orientation control of the object are shown and then, the effects of each term of the proposed control input signal on the system performances are discussed. Finally, a guidance of gain tuning is suggested on the basis of well-known force-velocity characteristics of human muscle in muscle physiology..
97. S. Arimoto, K. Tahara, M. Yamaguchi, P.T.A. Nguyen and H.-Y. Han, Principle of superposition for controlling pinch motions by means of robot fingers with soft tips, Robotica, 19, 1, 89-98, 2001.01.
98. S. Arimoto, M. Yoshida, J. H. Bae, Kenji Tahara, Dynamic force/torque balance of 2D polygonal objects by a pair of rolling contacts and sensory-motor coordination, Journal of Field Robotics, https://doi.org/10.1002/rob.10102, 20, 9, 517-537, 2003.01, It is well known that three frictionless fingers suffice to immobilize any 2D object with triangular shape but four fingers are necessary for a parallelepiped. However, it has been recently shown that only two fingers are enough to realize secure grasp of a rigid object with parallel flat surfaces in a dynamic sense if finger ends have a hemispherical shape with appropriate radius and thereby rollings are induced between finger ends and object surfaces. This paper focuses on the two problems: (1) dynamic force/torque balance of 2D polygonal objects under the effect of gravity force by means of a pair of rolling contacts and (2) concurrent realization of dynamically secure grasp and orientation control of 2D polygonal objects by using a pair of multi-fingered hands with hemispherical ends and sensory feedback signals without knowing object kinematics and mass center. It is shown that the force/torque balance can be attained by controlling both the contact positions and inducing adequate forces in both normal and tangential directions at each of contact points indirectly through finger joints without knowing object mass center and other kinematic parameters..
99. S. Nakamura, Kenji Tahara, J. H. Bae, M. Sekimoto, S. Arimoto, Experiments of grasping and object-manipulation by a pair of multi-degrees of freedom robot fingers, 2003 IEEE International Symposium on Computational Intelligence in Robotics and Automation, CIRA 2003 Proceedings - 2003 IEEE International Symposium on Computational Intelligence in Robotics and Automation Computational Intelligence in Robotics and Automation for the New Millennium, https://doi.org/10.1109/CIRA.2003.1222161, 3, 1162-1167, 2003.01, This paper is concerned with experimental analysis of pinching motion by a pair of multi-degrees of freedom robot fingers with rigid hemispherical tips. The experiments were carried out in the case that a parallelepiped object is placed on a non-slippery plate in a horizontal plane and motion of the fingers and the object is confined to the plane. As predicted from the theoretical analyses, experimental results show that stable grasping in a dynamic sense is realized by a sensory feedback constructed by using measurement data of finger joint angles and the rotational angle of the object. Further, it is shown from the experiments that an additional sensory feedback works well in realizing concurrent stable grasp and orientation control of the object..
100. S. Arimoto, J. H. Bae, Kenji Tahara, Stability on a manifold
Simultaneous realization of grasp and orientation control of an object by a pair or robot fingers, Proceedings - IEEE International Conference on Robotics and Automation, 2, 2336-2343, 2003, This paper is concerned with a stability theory of motion governed by Lagrange's equation for a pair of multi-degrees of freedom robot fingers with hemispherical finger ends grasping a rigid object under rolling contact constraints. When a pair of two d.o.f. fingers is used and motion of the overall fingers-object system is confined to a plane, it is shown that the total degree of freedom of the fingers-object system is redundant for realization of stable grasping though there arise four algebraic constraints. To resolve the redundancy problem without introducing extra performance specifications, a concept of stability of motion starting from a higher dimensional manifold to a lower-dimensional manifold expressing a set of states of stable grasp with prescribed contact force is introduced and thereby it is proved in a rigorous way that stable grasp in a dynamic sense is realized by a sensory feedback constructed on the basis of measurement data of finger joint angles and the rotational angle of the object. Further, it is shown that there exists an additional sensory feedback that realizes not only stable grasp but also orientation control of the object concurrently. These results can be extended to other two cases that 1) motion of the overall system is confined to a vertical plane and therefore it is affected directly by the gravity and 2) the object has non-parallel but flat surfaces..
101. S. Arimoto, Kenji Tahara, M. Yamaguchi, P. T A Nguyen, H. Y. Han, Principles of superposition for controlling pinch motions by means of robot fingers with soft tips, Robotica, https://doi.org/10.1017/S0263574700002939, 19, 1, 21-28, 2001.01, This paper analyzes the dynamics and control of pinch motions generated by a pair of two multi-degrees-of-freedom robot fingers with soft and deformable tips pinching a rigid object. It is shown firstly that passivity analysis leads to an effective design of a feedback control signal that realizes dynamic stable pinching (grasping), even if extra terms of Lagrange's multipliers arise from holonomic constraints of tight area-contacts between soft finger-tips and surfaces of the rigid object and exert torques and forces on the dynamics. It is shown secondly that a principle of superposition is applicable to the design of additional feedback signals for controlling both the posture (rotational angle) and position (some of task coordinates of the mass center) of the object provided that the number of degrees of freedom of each finger is specified for satisfying a condition of stationary resolution of controlled position state variables. The details of feedback signals are presented in the case of a special setup consisting of two robot fingers with two degrees of freedom..
102. S. Arimoto, Kenji Tahara, M. Yamaguchi, Existence of feedbacks from sensing to action for stable grasping and dextrous manipulation by multi-fingered robot hands, Proceedings of the 2001 IEEE International Conference on Control Applications CCA '01 IEEE Conference on Control Applications - Proceedings, 524-529, 2001, This paper derives lumped-parameter dynamics of motion of a pair of robot fingers with soft and deformable tips pinching a rigid object. The dynamics of the system in which area contacts between the finger-tips and the surfaces of the object arise are compared with those of a pair of rigid robot fingers with rigid contacts with an object. It is then shown that even in the simplest case of dual single degree-of-freedom fingers there exists a sensory feedback from measurement of finger joint angles and the rotational angle of the object to command inputs to joint actuators and this feedback connection from sensing to action eventually realizes stable grasping of the object, provided that the object is a rectangular parallelepiped and motion is confined to a horizontal plane. It is further shown that in the case of a pair of one d.o.f. and two d.o.f. fingers with soft tips there exists a sensory feedback that realizes not only stable grasping but also regulating the posture of the object at a specified rotational angle..
103. H. Y. Han, S. Arimoto, Kenji Tahara, M. Yamaguchi, P. T A Nguyen, Robotic pinching by means of a pair of soft fingers with sensory feedback, 2001IEEE International Conference on Robotics and Automation (ICRA) Proceedings - IEEE International Conference on Robotics and Automation, https://doi.org/10.1109/ROBOT.2001.932536, 1, 97-102, 2001, This paper proposes a pair of single or multi D.O.F. robot fingers with soft and deformable tips that can pinch an object stably in a dynamic sense with the aid of real-time sensory feedback. To realize dynamic stable pinching, a practical method of using optical devices is proposed for measuring both the maximum displacement of finger-tip deformation and the relative angle between the object surface and each of finger links. It is shown theoretically and by computer simulation that the overall closed-loop system of a pair of two single-D.O.F. fingers with soft tips with real-time sensory feedback of the difference between centers of two area-contacts at both sides of the object becomes asymptotically stable. This means that the pair achieves dynamic stable grasping (pinching). In the case of a pair of 1 D.O.F. and 2 D.O.F. fingers with soft tips, it is shown that the proposed method of closed-loop feedback of the difference between centers of two area-contacts and the rotational angle of the object can establish not only dynamic stable grasping but also regulation of the posture of the object..