Language：English   Publishing type：Research paper (scientific journal)  

A new station-keeping strategy based on nonlinear output regulation theory has been proposed for the periodic orbits in the circular restricted three-body problem. A Fourier series approximation was employed to generate the desired orbits, and then the output regulation theory for nonlinear systems was applied. The output regulation problem was solved in an analytical form. The proposed controller has been applied and verified in numerical simulations for the halo orbit of the sun–Earth L2 point. In the case that the reference orbit is the natural periodic orbit, the controller can approximate the optimal controller in the sense of minimizing the station-keeping cost. As an application of the proposed method, formation flying using circular orbits around the chief satellite has been worked out.

DOI： 10.2514/1.G002845

Language：English   Publishing type：Research paper (scientific journal)  

This study introduces a new robust nonlinear control scheme based on the theory of nonsingular terminal sliding mode control (NTSMC). Since conventional NTSMC utilizes a discontinuous switching function, a significant flaw called chattering can occur. The main purpose of this study is to design a new switching function based upon Lyapunov stability in order to alleviate this drawback over time. There are many approaches to mitigate the chattering drawback in SMC such as utilizing a smooth approximation of the switching element, or employing higher order sliding mode control (HOSMC) strategy. However, the use of a continuous approximation affects the system's performance and a finite reaching time to the sliding manifold, and in HOSMC the estimation of high-order derivatives of states is usually difficult and it still exhibits chattering in the presence of parasitic dynamics. In this study by employing a new sliding manifold including a time function, the chattering is attenuated as well as keeping the robustness. Finally, a second-order nonlinear dynamical system subject to disturbance is simulated to highlight the validity and applicability of the proposed method.

DOI： 10.1002/asjc.1477

Repository Public URL： http://hdl.handle.net/2324/4479597

Language：English   Publishing type：Research paper (scientific journal)  

Recent studies of vision-based navigation and guidance for robotic vehicles have been inspired by the biological systems found in flying insects. The wide-field integration of optic flow is one pre-existing method, in which the sensed optic flow is integrated along with sensitivity functions to mimic the action of directionally sensitive cells observed in some insects' visual systems. This study re-examines the wide-field integration method and reformulates the problem from a summation rather than an integral. This reformulation allows the wide-field integration measurement outputs to be directly compared with nonintegrated optic flow measurements. The method using nonintegrated optic flow measurements is shown to have some practical advantages, such as eliminating the need to define input sensitivity functions and having a measurement Jacobian that is easier to derive analytically. Also, the state estimates obtained with the nonintegrated method are proven to have minimum variance compared with those from the wide-field integration method. Numerical simulations of each method are shown for a vehicle maintaining level flight at constant altitude over a flat terrain.

DOI： 10.2514/1.59084

Language：Japanese   Publishing type：Research paper (scientific journal)  

Feedback Control of a Planar Space Robot Using a Moving Manifold

DOI： 10.7210/jrsj.25.745

Language：Japanese   Publishing type：Research paper (scientific journal)  

A Study on Orbital Transfer of a Rigid Satellite System Using Its Nonholonomic Constraint

DOI： 10.2322/jjsass.54.477

DOI： 10.2514/1.G008270

Web of Science

Publisher：AIAA SciTech Forum and Exposition, 2024  

The precise trajectory control of UAVs, including multirotors, is challenging due to uncertainties such as modeling errors, unmodeled aerodynamic forces, and wind disturbances. To address this issue, this paper focuses on real-time modeling of quadrotor motion exploiting recently developed data-driven methods. By constructing a dynamical model in real-time using data collected during flight, it is expected to develop a dynamical model that incorporates uncertainties arising from modeling errors and disturbances. In particular, the data-driven modeling method called Real-Time Update Dynamic Mode Decomposition (RTDMD), an extension of the DMD algorithm with sequential update rules, is employed for the real-time modeling of dynamical models. Identification experiments using experimental data demonstrate that the RTDMD successfully obtained a dynamical model for estimating the quadrotor’s state.

DOI： 10.2514/6.2024-0568

Scopus

Language：English   Publisher：International Symposium on Space Technology and Science  

<p>Spacecraft with movable parts can change their attitude through utilizing non-holonomic features generated by their motion. This can be used as an alternative attitude control method when their equipped attitude control devices no longer generate control torque. No propellant is required in this method, so it has attracted attention as a control method to extend the life of spacecraft. This paper discusses the optimization of the structural configurations to increase the efficiency of the non-holonomic features when attitude control devices are malfunctioned. The optimization problem is difficult due to several reasons: non-holonomic attitude change can be evaluated from numerical integration along trajectories in joint space, spacecraft might have many movable parts as well as structural design parameters, and so on. In this paper, the optimization problem is solved as iterative optimizations in the subspace consisting of the extracted parameters rather than considering all parameters simultaneously. The numerical results show that structural optimization can make the attitude change much more significant.</p>

DOI： 10.57350/jesa.169

CiNii Research

Language：English   Publisher：International Symposium on Space Technology and Science  

<p>This study aims at the attitude control problem of spacecraft with periodic disturbances and model uncertainty by using anticipatory Iterative Learning Control (ILC), a combination of feedback control and ILC in a discrete-time system. Using a sampling point a little forward in one previous cycle, the convergence accuracy to the target value is improved step by step by the anticipatory ILC scheme, and its effectiveness against periodic disturbances is verified. In addition, we compare the accuracy to the target value by changing the sampling point selected in one previous cycle.</p>

DOI： 10.57350/jesa.171

CiNii Research

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Publisher：Journal of Guidance, Control, and Dynamics  

DOI： 10.2514/1.G007151

Web of Science

Scopus

Language：English   Publisher：宇宙航空研究開発機構宇宙科学研究所 (JAXA)(ISAS)  

レポート番号: ASTRO-2023-A014(018)/In-person

CiNii Research

Language：English   Publisher：宇宙航空研究開発機構宇宙科学研究所 (JAXA)(ISAS)  

レポート番号: ASTRO-2023-C002(022)/In-person

CiNii Research

Language：English   Publisher：宇宙航空研究開発機構宇宙科学研究所 (JAXA)(ISAS)  

レポート番号: ASTRO-2023-C019(031)/In-person

CiNii Research

Language：English   Publisher：宇宙航空研究開発機構宇宙科学研究所 (JAXA)(ISAS)  

レポート番号: ASTRO-2023-C001(010)/In-person

CiNii Research

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (scientific journal)   Publisher：International Symposium on Space Technology and Science  

<p>This paper proposes an algorithm to systematically search for a good sequence and the number of intermediate orbits in order to design the low-thrust minimum-fuel halo-to-halo transfer. The proposed algorithm applies successive convex optimization for the optimal transfer design, and initial guesses for the optimization are generated by beam search. In the beam search process, intermediate halo orbits that construct the initial guesses are chosen from a family of halo orbits so that they are located between the initial and final halo orbits. By determining the appropriate evaluation index for the intermediate orbit design, the proposed algorithm can collect local optimal solutions with a reasonable computational time. The obtained optimal transfers provide several options for the total △<i>V</i> and time of flight, which helps to find the suitable solution based on mission requirements.</p>

DOI： 10.57350/jesa.48

CiNii Research

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEEE Access  

Navigation and control near asteroids are challenging due to high levels of uncertainty, necessitating a high degree of autonomy and safety. To address this challenge, we propose a novel method for leveraging data-driven approaches, which have garnered significant attention in recent years. Traditional data-driven and machine learning techniques have been applied to space exploration problems; however, they often require large amounts of data in advance and are not robust to unknown environments. Hence, they are typically used in auxiliary roles and are not easily adaptable to real-time modeling and control. We propose the use of the theory of dynamic mode decomposition (DMD) and delayed embedding to construct a data-driven real-time guidance and control system for asteroid landings. Our approach employs low-dimensional information obtained from onboard sensors to construct nonlinear dynamics in the vicinity of asteroids. Based on the constructed dynamical model, we propose a guidance control strategy for accurate and reliable spacecraft landing. Our proposed method has the potential to improve guidance and control systems for space exploration by enabling real-time modeling and control with reduced computational cost.

DOI： 10.1109/ACCESS.2023.3276754

Web of Science

Scopus

Language：English   Publishing type：Research paper (scientific journal)   Publisher：International Symposium on Space Technology and Science  

<p>This paper aims to construct a method to design low-energy transfer trajectories from Jupiter to Europa, one of the Galilean satellites, via ballistic transfer. The proposed method leverages the periapsis Poincaré map and efficiently finds ballistic transfer trajectories from Jupiter’s sphere of influence (SOI) to Europa. For the evaluation of the proposed method, the interplanetary trajectory from Earth to Jupiter’s SOI is designed by using existing methods, the Tisserand map and multiple gravity assists. By solving the phasing problem that considers the ephemeris of the celestial bodies, this map can find interplanetary trajectories with various transfer times depending on the launch date. It is demonstrated that the periapsis Poincaré map can efficiently find all ballistic transfer trajectories in the region, although it depends on the initial conditions. Furthermore, by applying the clustering method to the obtained ballistic transfer trajectories, we succeeded in finding families of ballistic transfer trajectories existing within the region.</p>

DOI： 10.57350/jesa.35

CiNii Research

Publisher：Proceedings of the International Astronautical Congress, IAC  

The Gateway will be constructed as a staging point for exploring cislunar space in the Artemis program. For the maintenance of this platform, uncrewed cargo transport is planned by JAXA. To efficiently conduct cargo transport, this study proposes a novel methodology to design low-energy chaotic transfers based on lobe dynamics in the planar circular restricted three-body problem (CR3BP). Lobe dynamics focuses on the " lobe, " the region determined by stable and unstable manifolds of a resonant orbit, and can reveal phase space transport of chaotic trajectories. In general, lobe dynamics of one resonant orbit can transfer a spacecraft only around the tori related to the resonant orbit in concern. The proposed method combines lobe dynamics of various resonant orbits to make a desired transfer. The fuel-optimal transfer path is found based on a graph by introducing some simplification. By adding trajectory correction maneuvers, the robust optimal transfer trajectory is achieved in the CR3BP.

Scopus

Language：Japanese   Publisher：The Japan Joint Automatic Control Conference  

DOI： 10.11511/jacc.66.0_536

CiNii Research

Language：Japanese   Publisher：The Japan Joint Automatic Control Conference  

DOI： 10.11511/jacc.66.0_526

CiNii Research

Publisher：Lecture Notes in Electrical Engineering  

For deep space landing missions, spacecraft are required to identify their expected landing sites autonomously because of the extremely long time delay caused by the distance between the spacecraft and Earth. This identification process is desirable to finish within several seconds by onboard computers with limited calculation performance. Moreover, autonomous identification based on natural features of landing sites are highly recommended in future missions, although some artificial target markers have been used for navigation and control to the landing site in some previous missions. To make fast but reliable identification of landing sites for the automatic task, this research utilizes a deep learning processing for images taken in different light-conditions and altitudes. First, a semantic segmentation model for rocks in terrain images is developed. For robust identification, some improvements are introduced in the semantic segmentation process. Then, to identify the same place in images taken at different altitudes, a comparison algorithm based on triangular shapes is applied. Thus after training, the semantic segmentation model can detect the same place from several images in a relatively short computational time.

DOI： 10.1007/978-981-19-2635-8_66

Web of Science

Scopus

Publisher：Proceedings of the International Astronautical Congress, IAC  

This paper presents optimization methods that incorporate elements of Adaptive Moment Estimation (Adam) into Sequential Quadratic Programming (SQP) for designing two-impulse transfer trajectories from one halo orbit to another with minimum velocity increment. The optimization problem can be formulated by a cost function that evaluates velocity increments at endpoints. The gradient and Hessian of the problem are calculated using the state transition tensors and then used for the Adam-enhanced SQP implementaion. To validate the effectiveness of this approach, we solve the optimal transfer problem using random initial guesses and stochastic disturbing acceleration. The results from numerical simulations are analyzed with respect to the cost function, transfer time, and orbit stability.

Scopus

Publisher：Proceedings of the International Astronautical Congress, IAC  

In recent years, comet exploration missions represented by the Comet Interceptor mission have attracted our attention to unravel the origin of our solar system. Motivated by the Comet Interceptor mission concept, this paper firstly proposes designing standby orbits by leveraging invariant manifold structures in the Sun-Earth CRTBP system. To expand accessible regions, the optimization problem is solved, and the optimal input added to unstable manifolds emanating from periodic and quasi-periodic orbits is obtained. Moreover, the two-point boundary value problem (TPBVP) about the final time of the propagation is solved to make multiple space probes form a constellation by leveraging both single and multiple shooting methods. Designing the trajectories to expand accessible areas by leveraging invariant manifolds and low-thrust engines enables even small spacecraft to observe and explore unknown comets.

Scopus

Publisher：Proceedings of the International Astronautical Congress, IAC  

Aerocapture is the one of the most effective methods for future large-scale exploration because it enable trajectory transformation with less fuel. In this study, optimal aerocapture problem is investigated based on the analysis of aerocapture trajectory. Simulate the aerocapture trajectory with and without uncertainties, and from the results, the optimal control condition for guided control of of aerocapture of developed. Using the optimal aerocaputre problem, this paper proposes the problem involving re-solving to design trajectories that can be more robust to uncertainties.

Scopus

Language：Japanese   Publisher：The Japan Joint Automatic Control Conference  

DOI： 10.11511/jacc.66.0_335

CiNii Research

Publisher：Proceedings of the International Astronautical Congress, IAC  

Recently, deep space exploration has advanced particularly with orbital characteristics of NRHO being widely studied. However, studies for spacecraft autonomy have not progressed well. A control law that combines feedback control and Iterative Learning Control(ILC) is applied to the attitude control system of a spacecraft, and furthermore, the control input is realized by a CMG capable of high output, with the aim of improving the attitude tracking control system step by step by increasing the orbital motion.

Scopus

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.3389/frspt.2022.919932

Web of Science

Language：English   Publishing type：Research paper (scientific journal)  

Publisher：Journal of the Astronautical Sciences  

This paper proposes the sparse optimal control in the circular restricted three-body problem to exploit the dynamical structure of the linearized motion around equilibrium points or periodic orbits. First, optimal transfer problem is formulated for a linearized system where the objective function and constraints are given by convex sets. For a long time transfer problem in the vicinity of periodic orbits, the Floquet-Lyapunov transformation and a normal form are introduced to enable numerical calculations. Then, the proposed method is applied to several transfer problems around an equilibrium point or periodic orbits and a parameter analysis is performed to understand the optimal transfer by changing the maximum thrust acceleration and time of flight. Finally, a new station-keeping strategy is proposed to implement the sparse optimal solution in a nonlinear dynamics.

DOI： 10.1007/s40295-022-00315-1

Web of Science

Scopus

Language：English   Publishing type：Research paper (scientific journal)  

Other Link： doi.org/10.1007/s40295-022-00315-1

Language：English   Publishing type：Research paper (scientific journal)   Publisher：Journal of Guidance, Control, and Dynamics  

In space missions, numerical techniques for minimizing the fuel consumption of spacecraft using low-thrust propulsion are desirable. Among various nonlinear optimization methods, convex optimization has been attracting attention because it allows optimal solutions to emerge robustly and requires short computation times. In particular, trajectory design in the three-body problem near the Lagrange points involves instability and nonlinearity. Hence, this study considers the application of convex optimization to trajectory design with low-thrust propulsion in cislunar space and verifies that this technique performs well, even for sensitive and highly nonlinear dynamics. Specifically, the convex optimization scheme is applied in the transfer from a halo orbit to a near-rectilinear halo orbit where both are periodic as defined in the circular restricted three-body problem. As a further step, the transfer problem is transitioned to an ephemeris model. In addition, extensive investigations of the dependence on various parameters used in convex optimization are conducted, and a trajectory corrections maneuver method is constructed combined with the convex optimization process. This investigation provides valuable insight into the convex optimization technique in the three-body problem and facilitates the estimation of low-thrust trajectory designs for complex space missions.

DOI： 10.2514/1.G005916

Web of Science

Scopus

researchmap

Other Link： https://doi.org/10.2514/1.G005916

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Publisher：Proceedings of the International Astronautical Congress, IAC  

The fuel minimization problem for a low-thrust spacecraft in a gravity field is formulated as a nonlinear optimal control problem. Euler-Lagrange equation is the necessary condition of a nonlinear optimal control problem and this is the Hamiltonian flow. To find the optimal solution of nonlinear optimal control problem, a two-point boundary value problem for the Euler-Lagrange equation have to be solved. However, since this problem cannot be solved analytically, it is solved numerically, which is generally known to be difficult to find the optimal solution. In this paper, a new method to solve a nonlinear optimal control problem is proposed, which the Koopman Operator theory is applied to Hamiltonian flow. The Koopman Operator is the finite dimensional linear operator in the functional space, so this cannot be calculated. But by using data science, the Koopman Operator of the Hamiltonian flow can be computed approximately. In my method, taking advantage of the linearity of the Koopman Operator, the solution of a nonlinear optimal control problem satisfying the boundary conditions can be easily obtained.

Scopus

Language：Japanese   Publisher：The Japan Joint Automatic Control Conference  

DOI： 10.11511/jacc.65.0_1450

CiNii Research

Web of Science

Publisher：33rd Congress of the International Council of the Aeronautical Sciences, ICAS 2022  

In the design of multi-rotor vehicles, it is very important to predesign the overall layout from the perspectives of fluid dynamics, flight dynamics, and control performance. However, there is currently no unified guiding principle. In addition, traditional multi-rotor vehicles are usually not capable of high-speed flight and long endurance. This study discusses a kind of compound multi-rotor vehicle configurations and analyze the influence of the overall layout of multi-rotors on flight performance by utilizing Blade Element Momentum Theory (BEMT) and Particle Swarm Optimization (PSO). First, the flight dynamics model of the compound multi-rotor aircraft is established based on BEMT. Next, by using the PSO algorithm, aiming at the longest cruising distance, some results of proper layouts are shown according to different rotor sizes, positions, wing area, propeller sizes and rotating speeds. Finally, according to the simulation results, the influence of each independent variable on the optimal layout is analyzed. The results show that the method proposed in this paper can be applied as a guideline for the layout design of multi-rotor vehicles, and the compound multi-rotor has better flight performance than the traditional multi-rotor.

Scopus

Publisher：Proceedings of the International Astronautical Congress, IAC  

In trajectory design of satellite tours in multibody dynamical systems such as the Jovian system, it is important to make good use of the gravity of celestial bodies. However, trajectory design is difficult in the Jovian region because the dynamics around this system is highly nonlinear due to the influence of several satellites as well as Jupiter and Sun. This paper proposes a new method for satellites tour design utilizing the Poincaré map which enables us to find the natural or ∆v-assisted satellite tour of the Galilean satellites.

Scopus

Publisher：Proceedings of the International Astronautical Congress, IAC  

This paper constructs the framework to design low-thrust minimum-fuel trajectories for a phase-free orbit-to-orbit transfers by leveraging convex optimization and beam search. The proposed method formulates the convex optimization problem involving the departure and arrival phases as optimization parameters; it optimizes the position and velocity of the initial point along the departure orbit and those of the final point along the arrival orbit, as well as the whole transfer trajectory and control inputs. Initial guesses for the optimization problem are generated by choosing intermediate orbits from a family of periodic orbits. Intermediate orbits are located between the departure and arrival orbits to guide a transfer trajectory. The selection of intermediate orbits changes the optimal solution to be obtained. To find the good sequence and number of intermediate orbits, this paper introduces the beam search algorithm to the proposed framework. As an example, the design of low-thrust transfers between halo orbits in the Earth-Moon system is conducted. The obtained results demonstrate that the proposed framework can find the transfer trajectories with lower fuel consumption by adjusting the departure and arrival phases. In conclusion, when the departure and arrival orbits are given, the proposed framework can widely search for the local optimal transfer trajectories between them by utilizing periodic orbits of a certain family.

Scopus

Publisher：Proceedings of the International Astronautical Congress, IAC  

The dynamics in the vicinity of asteroids is highly uncertain，therefore, guidance and control requires a high degree of autonomy and safety. We propose a method to deal with the uncertainty by applying data-driven methods, which have attracted much attention in recent years. The proposed method enables us to construct the nonlinear dynamics for guidance and control the vicinity of asteroids in real-time using low-dimensional information obtained from on-board sensors, and propose a guidance control strategy for the spacecraft landing based on the obtained accurate dynamics.

Scopus

Publisher：33rd Congress of the International Council of the Aeronautical Sciences, ICAS 2022  

In this paper, we propose an altitude estimation method by using Wide-Field-Integration (WFI) of optic flow. WFI of optic flow is a motion estimation method inspired by a biological research on the visual processing system of flying insects' compound eyes. In the standard estimation process, altitude information of a flying vehicle is necessary to estimate the motion variables of flying vehicles. The method proposed in this paper can estimate the altitude as well as the motion variables by using two patterns of optic flow acquired by two onboard cameras. The proposed method is useful for reducing onboard instrument mass and thus suitable for small autonomous vehicles. This paper discusses the mechanism of the altitude estimation and explores the suitable positions of the WFI of optic flow sensors in simulations.

Scopus

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.2322/tastj.19.562

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.2322/tastj.19.545

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Repository Public URL： http://hdl.handle.net/2324/4479733

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.2322/tjsass.63.243

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (scientific journal)  

Language：Japanese   Publishing type：Research paper (scientific journal)  

DOI： 10.1299/transjsme.15-00550

Repository Public URL： http://hdl.handle.net/2324/4479600

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (scientific journal)  

The hyperbolic instability of collinear libration point orbits dominates the distribution of orbit uncertainty, which is closely related with the unstable manifold of the local orbit. Exploiting the distribution of orbit uncertainty in an unstable orbital environment, an integrated orbit determination and maintenance approach is proposed. X-ray pulsar navigation embedded in the Kalman filtering architecture is adopted to determine the orbit of a spacecraft flying along the Earth-Moon L₂ halo orbit. To keep the spacecraft in the vicinity of the nominal trajectory, the newly proposed orbit maintenance approach based on the covariance matrix is proposed to design the orbit maintenance maneuver. The numerical simulations show that the proposed approach has a good performance in orbit determination and maintenance.

DOI： 10.1016/j.actaastro.2018.11.041

Language：English   Publishing type：Research paper (scientific journal)  

This paper proposes a new approach of using differentials in aerodynamic drag in combination with thrusters to control satellite formation flying in low Earth orbits. Parameterized output regulation theory for formation-flying missions with combined control action is developed based on the Schweighart–Sedwick relative dynamics equations. The theory is implemented to precisely track the different trajectories of reference relative motion and eliminates the effects of the J₂ perturbations. The parametric Lyapunov algebraic equation is proposed to ensure the stability of the linear relative model subject to saturated inputs. The main goal of this study is to approve the viability of using the differentials in aerodynamic drag to precisely control different formation-flying missions. Numerical simulations using a high-fidelity relative dynamics model and a high-precision orbit propagator are implemented to validate and analyze the performance of the proposed control algorithm in comparison with the linear quadratic regulator algorithm based on actual satellite models.

DOI： 10.2514/1.G004219

Repository Public URL： http://hdl.handle.net/2324/4479055

Language：English   Publishing type：Research paper (scientific journal)  

Many of the equations of motion appearing in the aerospace field are nonlinear, and the problem of input optimization under this equation of motion is important. There are two methods for solving the nonlinear optimal control problem: direct method and indirect method. In the direct method, the equation of motion is discretized, and the problem is solved as a nonlinear programming problem with motion equations as constraints. In the direct method, it is possible to solve the problem by adding various constraints, but the solution becomes complicated and it is difficult to guarantee the convergence to the optimal solution. In this study, we consider a set of unknowns that satisfy constraints as Riemannian manifolds, and treat the problem as an unconstrained optimization problem on Riemannian manifolds. A simplified rocket trajectory optimization problem illustrates the proposed method.

Language：English   Publishing type：Research paper (scientific journal)  

This paper considers manifold-to-manifold transfers in the circular-restricted three-body problem enabled by low-thrust acceleration where an initial and target states lie on invariant manifolds associated to libration point orbits with different Jacobi constant. The basic idea is to utilize a family of stable and center manifolds that lie arbitrarily close to the target invariant manifold to reduce the cost of transfer. The linear quadratic regulator is used to design feedback control to transfer to the target manifold. Time invariant and time periodic controlleres are derived based on the linearized motion around the equilibrium point and periodic orbit respectively. The results show that the feedback controller can shape the linearized motion around manifold to be that around the equilibrium point or a periodic orbit. As a demonstration, transfer trajectories are designed to target the unstable manifold associated with an unstable Lyapunov orbit in the Earth-Moon system.

Language：English   Publishing type：Research paper (scientific journal)  

This paper investigated the manifold-based robust stationkeeping approach for the halo orbit near the Earth-Moon L2 point in the ephemeris model. The well-known Hamiltonian structure-preserved (HSP) method is utilized to design the controller for stationkeeping. However, conventional HSP method is proposed under the ideal condition, where the equations of motion are constructed in the circular restricted three-body problem, and the navigational uncertainty is not considered as well. Actually, these uncertainties always exist and have significant influence on the performance of stationkeeping. To make the results more realistic, the dynamics in the ephemeris model is used to describe the motion of a spacecraft. A filtering structure-based navigation is incorporated in the stationkeeping, where the navigational uncertainty is introduced. In addition, the navigation filter is reformed to compensate for the control uncertainty. Simulation is performed to observe the influence of the control gain and the magnitude of the uncertainty on the stationkeeping performance.

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

This paper proposes a new numerical method for finding libration point orbits in the vicinity of collinear libration points in the circular restricted three-body problem. The main advantage of this method is that it requires neither an initial guess nor complex algebraic manipulations for finding both quasi-periodic and periodic orbits. The proposed method consists of two steps: center manifold design and differential correction. The first step provides a quasi-periodic orbit parametrized by a single parameter vector. In the second step, the parameter vector in the first step is used to obtain an exact periodic orbit. This method is applied to find periodic and quasi-periodic orbits in the Sun-Earth restricted three-body problem around the L₁ and L₂ libration points.

DOI： 10.1016/j.actaastro.2019.02.029

Language：English   Publishing type：Research paper (scientific journal)  

The 29th Workshop on JAXA Astrodynamics and Flight Mechanics 2019 (Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency (JAXA)(ISAS)), Sagamihara, Kanagawa Japan

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (international conference proceedings)  

This paper proposes the controllability analysis of relative motion using different configurations for hybrid control actions of space environmental forces. It tends to present a minimal configuration for the missions exploiting these forces. It illustrates the constraints in each space environmental force and analyzes the integration between these forces to achieve full controllability of the satellite formation flight for near-circular low earth orbits with different orbit configurations. The paper implements a Kalman decomposition approach to decompose the system into controllable and uncontrollable subspaces for linear time-invariant control actions. Numerical simulations are investigated to study the controllability analysis for nonlinear models and substantiate the success of the controllability study for all hybrid control actions with different orbit configurations.

Language：English   Publishing type：Research paper (scientific journal)  

This paper presents a new method of optimal trajectory design for formation flying. Under linearized assumptions and a quadratic performance index, we introduce an attractive set of optimal control based on the linear quadratic regulator theory. The attractive set is defined as a set of all initial states to reach a desired state for a given cost. In particular, we consider attractive sets for two problems: a fixed final-state, fixed final-time problem and an infinite-time problem, and the optimal initial state is found based on the geometry of the attractive set. The optimal trajectories for two problems are evaluated in terms of L₁-norm of control input and termination time.

DOI： 10.2322/tastj.17.96

Language：English   Publishing type：Research paper (international conference proceedings)  

This paper proposes a new hybrid control action of differentials aerodynamic drag and thrusters to control satellite formation flying in low Earth orbits. Parameterized output regulation algorithm for formation flying missions is developed based on the Schweighart-Sedwick relative dynamics equations. It is implemented to precisely track the different trajectories of reference relative motion and eliminates the effects of the J₂ perturbations. Parametric Lyapunov algebraic equation is derived to ensure the stability of the linear relative model subject to saturated inputs. The main goal of this study is to approve the viability of using the differentials in aerodynamic drag to precisely control different formation flying missions. Numerical simulations using a high fidelity relative dynamics model are implemented to analyze the performance of the proposed control algorithm in comparison with the linear quadratic regulator algorithm for actual satellite parameters. The paper exploits a high-precision orbit propagator model to verify the robustness of the control algorithm.

Repository Public URL： http://hdl.handle.net/2324/4479055

Language：English   Publishing type：Research paper (international conference proceedings)  

This paper generalizes the invariant manifolds of unstable libration point orbits through the application of continuous thrust. Considering Jacobi constant of the end of invariant manifolds, an artificial periodic orbit around a libration point realizes heteroclinic connections between itself and an unforced periodic orbit with same Jacobi constant of the end of invariant manifolds. Heteroclinic connections between libration point orbits are constructed by detecting intersections of states of manifolds on the Poincaré map. We reveal low-energy spacecraft can transfer to some periodic orbits with different Jacobi constant. In addition, this paper defines New Jacobi constant of low-thrust spacecraft. By utilizing new Jacobi constant, we illustrate zero-velocity curves of low-thrust spacecraft and reveal that there is a crack of zero-velocity curves and spacecraft can pass the crack.

Language：English   Publishing type：Research paper (international conference proceedings)  

A structure of the optimal trajectory for minimizing fuel consumption in an unstable dynamical environment such as the three-body problem is not well studied. Recently, it has been found that a sparse solution structure appears in the optimal control of a dynamical system. The concept of sparsity explains the property that the minimum fuel trajectory corresponds to the trajectory which minimizes the total thrusting time. In this paper, we propose a numerical method to obtain the minimum fuel sparse optimal trajectory in the unstable dynamical system. As an example, proposed methods are applied to the transfer in the Sun-Earth system.

Language：Japanese   Publishing type：Research paper (scientific journal)  

Wide-Field-Integration of optic flow for autonomous vehicles

DOI： 10.11511/jacc.61.0_1136

Language：English   Publishing type：Research paper (scientific journal)  

In trajectory design of a spacecraft, reducing the fuel consumption is important factor. In order to find the minimum fuel trajectory, this paper considers the L ¹ norm as the performance index. This paper discuss design parameters characterizing the L ¹ optimal trajectory, such as sampling time, flight time and magnitude of thrust. Also, this paper compare with the conventional method from the viewpoint of fuel consumption. In addition, this paper consider the rendezvous problem considering safety.

Language：English   Publishing type：Research paper (scientific journal)  

This paper presents novel methods to provide libration point orbits (LPOs) and invariant manifolds (IMs) associated with libration point orbits in the elliptic restricted three-body problem (ERTBP). First, we introduce an extended autonomous system to describe the ERTBP. By introducing an autonomous system which generates a periodic function and integrating it with the ERTBP which is non-autonomous, we can obtain the extended autonomous system. Then, the center manifold design method which can uniquely provide an LPO in the circular restricted three-body problem is applied to the ERTBP. Next, we present a design method for IMs in the ERTBP by using the local stability characteristics obtained by the state transition matrix along LPOs of the extended system. The proposed design methods are applied and verified for the Earth-Moon L ₁ ERTBP. We show various LPOs in the ERTBP by changing design parameters, and IMs associated with a libration point and an LPO.

Language：English   Publishing type：Research paper (scientific journal)  

In this study, a concept of optimality is introduced into Port-Hamilton systems for attitude control of spacecraft. Port-Hamiltonian systems make it possible to design asymptotically stable controllers in a uniform procedure for a wide variety of physical systems. By introducing optimality to Port-Hamilton system, conventional error systems of Port-Hamilton systems are expanded to minimize a quadratic form of evaluation function. In this study, as an optimal control method of Port-Hamiltonian system, Hamilton-Jacobi-Bellman (HJB) equation is considered. Since solving HJB equation is not easy, the equation is simplified through generalized canonical transformation, which is a unique conversion of Port-Hamiltonian system. Furthermore, by considering the minimum evaluation function as a Hamiltonian transformed through the generalized canonical transformation, the analytical solution of the HJB equation can be derived. This method can be used for a time-varying error system and applied for tracking control of spacecraft to specified trajectories. The optimality of the control input obtained from the proposed procedure is verified in numerical simulations.

Language：English   Publishing type：Research paper (scientific journal)  

The study examines the control algorithm of a three-dimensional attitude and position of a free-floating rigid body with three thruster forces in which the force directions are fixed with respect to the body. This study provides a theory to develop a control method of an underactuated satellite with the minimum thruster number. In the procedure, three switching controllers are used in conjunction with motion planning in the final angular-rate deceleration phase to individually control the six state variables to the target values. The switching controllers have a hierarchical structure by using invariant manifolds as switching surfaces. The state variables in higher class manifolds that include lower class ones are adjusted by repeatedly adding intentional disturbances while the lower class state variables are returned to the original values by using lower class invariant manifolds. This study describes methods to define the invariant manifolds and also the intentional disturbance for achieving the forementioned control strategy. Finally, the motion planning in the angular-rate deceleration phase from a remained single-axis rotation finalizes the six state values of the body to the target values. Numerical simulations verify the proposed method.

DOI： 10.1155/2018/2825681

Language：English   Publishing type：Research paper (scientific journal)  

The 28th Workshop on JAXA Astrodynamics and Flight Mechanics 2018 (July 30-31, 2018. Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency (JAXA)(ISAS)), Sagamihara, Kanagawa Japan

Language：English   Publishing type：Research paper (scientific journal)  

The 28th Workshop on JAXA Astrodynamics and Flight Mechanics 2018 (July 30-31, 2018. Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency (JAXA)(ISAS)), Sagamihara, Kanagawa Japan

Language：English   Publishing type：Research paper (scientific journal)  

This study applies a sliding mode control (SMC) strategy for a robust controller of a quad-rotor vehicle. First, a controller combined with a nested control loop and an SMC is introduced, because a quad-rotor vehicle has only four control inputs although the vehicle has six degrees of freedom. The control performance for the feedback gains in the nested loop is investigated in numerical simulations. Subsequently, the effects of practical system limitations (control cycle and rotor dynamics) on the control performance are examined. Finally, the robust performance of the SMC strategy on a quad-rotor vehicle is discussed.

DOI： 10.20965/jrm.2018.p0397

Language：English   Publishing type：Research paper (international conference proceedings)  

This paper explores the influence of unstable dynamics on orbit determination. A halo orbit about the Earth-Moon L2 is considered to be the nominal orbit and the dynamics model is constructed based on the Earth-Moon circular restricted three body problem. X-ray pulsar navigation method is introduced for orbit determination that is performed by Kalman filter. Simulation results show that unstable manifold of halo orbit dominates the growth of orbit-determination error and the corresponding uncertainty. However, when the orbit-determination measurements are incorporated in, the results change and are greatly influenced by the characteristic of the X-ray pulse measurements.

Language：Japanese   Publishing type：Research paper (scientific journal)  

Motion Estimation for Aerospace Vehicles Based on a Compound Eye System of Flying Insects

DOI： 10.11499/sicejl.57.266

Repository Public URL： http://hdl.handle.net/2324/4479732

Language：English   Publishing type：Research paper (scientific journal)  

The swing-by maneuver is known as a method to change the velocity of a spacecraft by using the gravity force of the celestial body. The powered swing-by has been studied to enhance the velocity change during the swing-by maneuver. This paper studies another way of the powered swing-by using tether cutting, which does not require additional propellant consumption, and shows that the proposed powered swing-by can increase the effect of the swing-by as same as using impulsive thrust. Moreover, it is discussed whether the system has possibility to realize both the powered swing-by of a mother satellite and the planetary capture of a subsatellite simultaneously.

DOI： 10.1016/j.actaastro.2017.11.002

Language：English   Publishing type：Research paper (international conference proceedings)  

In previous research, a controller design procedure via generalized canonical transformations has been proposed to keep the passivity feature of Port-controlled Hamiltonian systems. The procedure has a general form and is applicable to spacecraft's attitude motion described with quaternion parameters. This paper investigates the roles of several design parameters in the generalized canonical transformations. Special attention is placed on the relation between the shape of Lyapunov functions and the convergence speed of the state variables. Furthermore, from the analysis utilizing the linearized form of the Port-controlled Hamiltonian system, the guideline to decide the preferable ratio between two parameters in the design procedure is proposed.

DOI： 10.23919/SICE.2017.8105722

Language：English   Publishing type：Research paper (international conference proceedings)  

This paper proposes a new method of optimal trajectory design for formation flying along an elliptical orbit. Under linearized assumptions and a quadratic performance index, the optimal cost is quadratic in the initial state. Attractive sets of optimal control are defined as contours of the optimal cost based on linear quadratic regulator theory. It describes a set of all initial states to reach a desired state by a given cost. By solving the optimal control problem for TH equations, the optimal cost is obtained as a time-periodic function. This paper develops the attractive set for a time-periodic system and procedure to draw the attractive set is shown. The advantage of using attractive sets for optimal trajectory design is that it can determine the optimal initial state immediately. The various shape of the periodic orbit and the attractive sets are demonstrated by weight parameters of optimal control theory.

Language：English   Publishing type：Research paper (international conference proceedings)  

In this paper, we extend the flow function method for finding resonant orbits. The relation between flow function, resonance number and order of the resonant orbit are revealed. The resonant orbits design in the Sun-Earth CRTBP are demonstrated and the results show that the resonant orbits can be found globally and systematically by the flow function method. The flow function method can also be applied to obtain higher order resonant orbits. As an application, we propose a transfer trajectory to the L₄/L₅ SPOs by using various resonant orbits. Our results reveals that two types of insertion is possible for SPO insertion with small ΔV.

Language：English   Publishing type：Research paper (international conference proceedings)  

This paper presents a novel method to realize station-keeping and control attitude motion simultaneously on a libration point orbit based on the nonlinear output regulation. First, the coupled orbit-attitude motion of a rigid spacecraft subject to three-body dynamics is formulated using the quaternion. Next, the reference orbit and attitude are represented as the output of an autonomous system called exosystem, assuming the reference orbit and attitude are given by a truncated Fourier series. Then the controller is derived by solving the output regulation problem. The derived controller has the explicit form and can achieve the asymptotically tracking for any reference orbit and attitude represented in the Fourier series. The proposed controllers are applied and verified for the Sun-pointing attitude control and station-keeping along Sun-Earth L₂ Halo orbits.

Language：English   Publishing type：Research paper (international conference proceedings)  

This paper proposes a novel optic flow-based navigation system for planetary rovers. Optic flow is a vector field of relative velocities between the camera mounted on a rover and environments, and it is often utilized for motion estimations or relative distance estimations. However, only either one of them can be estimated in general optic flow processing. The method proposed in this paper enables both of the estimations by utilizing an image segmentation technique in computer vision and applying Wide-Field-Integration (WFI) of optic flow for robust estimations. Thus, both obstacle avoidance and avoidance of getting stuck, which are key technologies for planetary exploration rovers, are realized in the method. Furthermore, since the estimation is accomplished in linear processing, a real-time estimation is possible by onboard computers. The effectiveness of the proposed method is examined through numerical simulations, considering sensor noises and the shape of obstacles.

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.5923

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

This paper presents the trajectory design and analysis of the near-Earth asteroid (NEA) deflection mission enabled by a kinetic impact of an intermediate asteroid. The sequential transfer trajectory is designed by solving two Lambert's problems that yield a chain collision between a spacecraft and an intermediate asteroid, followed by a collision between the intermediate asteroid and an NEA. The characteristics of the low-cost trajectories are then identified with respect to the optimal collision point. We show that the feasibility of the mission depends on the existence of an intermediate asteroid with small minimum orbit interception distance (MOID) with the NEA. Moreover the selection strategy of an intermediate asteroid that makes the mission feasible is discussed. We show that several asteroids exist that allow a 10 ton spacecraft with limited ΔV to be launched and impact the NEA 99442 Apophis allowing a deflection given several years warning time.

DOI： 10.1016/j.asr.2015.08.016

Language：Japanese   Publishing type：Research paper (scientific journal)  

Environment recognition through laser-range-finder for small exploration rover

DOI： 10.1299/transjsme.15-00550

Repository Public URL： http://hdl.handle.net/2324/4479599

Language：English   Publishing type：Research paper (scientific journal)  

Underactuated control offers fault-tolerance for satellite systems, which not only enables the position and attitude control of a satellite with fewer thrusters, but also can reduce the number of thrusters equipped on the satellite even when considering the need for backups. Due to having fewer thrusters, the coupling effect between the translational motion and rotational motion of the satellite cannot be avoided, and the coupled motion must be considered in control procedures. This paper presents a global trajectory design procedure required for the position and attitude control of an underactuated satellite. The satellite has four thrusters with constant thrust magnitudes on one plane of the satellite body. Then, an analytical solution for coupled motion between the rotation and translation of the satellite is obtained using three-step maneuvers of attitude control. The trajectory design based on the analytical solution is shown for the control of translational and rotational motion in three dimensions. Finally, a numerical simulation is performed to verify the effectiveness of the proposed design procedure.

DOI： 10.2322/tjsass.59.107

Language：English   Publishing type：Research paper (international conference proceedings)  

This paper studies a control law to stabilize the orbital motion in the vicinity of an unstable equilibrium points and periodic orbits in the circular-restricted three-body problem. Utilizing the eigenstructure of the system, the fuel efficient formation flying controller via linear quadratic regulator (LQR) is developed. Then the chattering attenuation sliding mode controller (CASMC) is designed and analyzed for the in-plane motion of the circular circular-restricted three-body problem. Simulation studies are conducted for the Sun-Earth L₂ point and a halo orbit around it. The total velocity change required to reach the halo orbit as well as to maintain the halo orbit is calculated. Simulation results show that the chattering attenuation sliding mode controller has good performance and robustness in the presence of unmodeled nonlinearity along the halo orbit with relatively small fuel consumption.

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：Japanese   Publishing type：Research paper (scientific journal)  

Language：Japanese   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (scientific journal)  

Language：Japanese   Publishing type：Research paper (scientific journal)  

Circular Restricted Three-body Problem as a Subject of Internship in the Field of Aeronautics and Astronautics

DOI： 10.4307/jsee.62.2_73

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (international conference proceedings)  

In this paper, an approach to optimize deflection mission of Near Earth asteroids under uncertainty is proposed based on control theoretical framework. By using the nonlinear mapping from initial deviation to the final deviation, the performance index J which is expressed as a function of the distance of the Earth in the Earth's closest approach time is minimized for the worst case initial condition. We also formulate the robust orbital transfer problem of kinetic impactor spacecraft where the initial state estimation error exists.

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

This study proposes a new control method for under-actuated planar satellites having body-fixed thrusters that can generate unilateral and constant forces. The proposed method is applicable when the thrusters are not balanced, which means a rotational motion is inevitably induced whenever the thrusters are turned on. By applying the method, the position and attitude of any planar satellite can be controlled to arbitrary target states so long as a controllability condition is satisfied. The control logic is based on a switching control using plural manifolds. First, the satellite is transferred to an initial manifold, and then it moves to another manifold while decreasing its velocity and approaching the target states. The ON/OFF timing of the thrusters to transfer among the manifolds is explicitly specified in this paper. A numerical simulation validates the proposed control logic.

DOI： 10.1299/kikaic.79.225

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：Japanese   Publishing type：Research paper (scientific journal)  

DOI： No.2012-JCR-0553

Language：English   Publishing type：Research paper (international conference proceedings)  

This paper develops a new robust nonlinear control algorithm based on the theory of sliding mode to control the attitude of a satellite. The system comprises a satellite with three pairs of thrusters on the satellite's principal axes. Since conventional sliding mode controllers include a discontinuous function, a significant problem called chattering can occur. The main purpose of this paper is to design a new switching function in order to alleviate this drawback. Moreover, for increasing the robustness of the proposed controller, a new slope-varying hyperbolic function is utilized. Simulation results highlight the effectiveness of the proposed method.

Language：English   Publishing type：Research paper (international conference proceedings)  

In this paper, we apply Wide-Field integration (WFI) of optic flow for the state estimation of a planetary landing vehicle. This study utilizes nonlinear expressions for the Fourier coefficients of the optic flow instead of linearized expressions. By using the nonlinear expressions, it is shown that the vehicle's attitude angles can be estimated as well as its velocity components. First this paper deals with a two-dimensional model and explains how to estimate state variables. Then two three-dimensional models are discussed. Numerical simulation results are shown to evaluate the estimation accuracy.

Language：English   Publishing type：Research paper (international conference proceedings)  

New advances in vision-based navigation for micro air vehicles (MAVs) have been inspired by the biological systems of flying insects and the use of optic flow. These biologically-inspired optical sensor systems for MAVs are computationally efficient and have low mass and low power consumption, which makes them attractive for small spacecraft. This study explores the applicability of the wide-field integration (WFI) of optic flow to a spacecraft operating in close proximity to an asteroid. In contrast with past WFI work, this study uses an asteroid-relative reference trajectory and known a priori environment model such that the optimal sensitivity functions are recalculated onboard the vehicle at each time step. Numerical simulations with computer-generated images of the asteroid surface are used to estimate the vehicle's translational and angular velocities. Although the accuracy of these state estimates are reasonable considering the noise in the optic flow measurements, the onboard recalculation of the sensitivity functions for this time-varying scenario add computational burden which negates the main advantage of the WFI method. Hence, future applications to time-invariant scenarios for small-body missions are also discussed.

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (international conference proceedings)  

This paper deals with the two-dimensional position and attitude control of a satellite by on-off thrusters which are fixed to the satellite's body. Since the thrusters generate constant and unilateral forces, the equations of motion form nonholonomic constraint and cannot be integrated. Furthermore, the satellite's mass changes due to the fuel consumption. Utilizing Fresnel integrals and the partial integrals, we derive the approximate analytic solution considering the satellite's mass change to achieve a specified satellite's position and attitude. The accuracy of the proposed approximate technique is verified by applying it to a condition considered in SLIM project of JAXA.

Language：English   Publishing type：Research paper (international conference proceedings)  

This paper discusses a position and attitude control problem of an underactuated satellite which uses on-off thruster mechanisms for control. Each thrusters has constant orientation relative to the satellite's body, and can generate only unilateral forces. The purpose of this paper is to clarify the control law for simultaneous position and attitude control for this type of satellite configuration. Considering the input constraints, we obtain the analytical solutions of the satellite's translational and rotational motion. Then the control procedure utilizing an invariant manifold is derived. Some numerical simulations are shown to verify the effectiveness of the proposed controller.

Language：English   Publishing type：Research paper (scientific journal)  

This paper deals with the three-dimensional attitude control of an underactuated satellite equipped with thrusters whose force directions are fixed to the satellite. First, the necessary number of thrusters for the satellite's attitude control is discussed utilizing the Minkowski-Farkas theorem. Then, using the wz parameters for a satellite's attitude expression, this paper proposes a non holonomic attitude controller which is effective for any satellite regardless of its moment of inertia. Numerical simulation demonstrates the effectiveness of the proposed controller. Furthermore, the efficiency of the controller for different thruster positions is also discussed.

DOI： 10.20965/ijat.2011.p0892

Language：Japanese   Publishing type：Research paper (scientific journal)  

Position and Attitude Feedback Controller of a Planar Satellite with Two Thrusters

DOI： 10.2322/jjsass.59.183

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (scientific journal)  

This study deals with a multi-legged planetary rover with a spherically isotropic leg arrangement. The legged rover is a reliable rover system for exploration on rough terrains, because it can continue walking even after overturning. Moreover, the legged rover can also show a rotational motion by utilizing its isotropic shape. This paper discusses the walking performance of two types of rover shapes: one has a six-leg arrangement based on a regular octahedron and the other has an eight-leg arrangement based on a regular hexahedron. The design procedure of the proposed rover is explained, and a test-bed system, which is developed to demonstrate the fundamental motions, is also presented.

DOI： 10.1163/016918611X563300

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (scientific journal)  

This study deals with the in-plane motion of a free-floating satellite equipped with thrusters whose force directions are fixed to the satellite. The system's governing equations form nonintegrable second-order “nonholonomic” constraints due to the fixed force directions to the satellite. This paper treats a satellite with three thrusters, and at first assumes that the magnitudes of the thrusters can continuously be changed from zero to a specified positive value. Under the assumption, it is shown that the nonholonomic governing equations can be transformed into holonomic ones by a feedback of the rotational angular velocity. Then, this paper shows the procedures to control the satellite's position and attitude precisely. Finally, we restrict the magnitude of the thrusters to be constant, and discuss the control techniques for such systems.

DOI： 10.2322/tastj.8.Pd_1

Language：English   Publishing type：Research paper (international conference proceedings)  

This paper discusses a position and attitude control problem of an underactuated satellite which uses on-off thruster mechanisms for control. Each thrusters has constant orientation relative to the satellite's body, and can generate only unilateral forces. The purpose of this paper is to clarify the control law for simultaneous position and attitude control for this type of satellite configuration. Considering the input constraints, we obtain the analytical solutions of the satellite's translational and rotational motion. Then the control procedure utilizing an invariant manifold is derived. Some numerical simulations are shown to verify the effectiveness of the proposed controller.

DOI： 10.2514/6.2011-6352

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (international conference proceedings)  

This study deals with the in-plane motion of a free-floating planar satellite equipped with two thrusters having constant force magnitude and fixed direction with respect to the satellite. This paper discusses the motion of such a satellite, and proposes a simple trajectory design procedure for controlling both the satellite's position and attitude angle. First, this paper investigates the motion for constant force magnitude. A drift-less rotational maneuver forms an "invariant manifold", which can be used to design a trajectory for the target state. Then, the condition of the input profile for the drift-less motion is discussed. Furthermore, this paper explains an advantage of a rotational maneuver which intentionally generates drift velocity.

DOI： 10.2514/6.2010-8393

Language：English   Publishing type：Research paper (international conference proceedings)  

This paper deals with an in-plane trajectory design method for a solar sail spacecraft to rendezvous with a planet. In the interplanetary rendezvous problem, the spacecraft's velocity must coincide with the orbital velocity of the planet when it reaches the planet's orbit. This paper proposes a trajectory design procedure that utilizes an invariant manifold for a specified control profile to reach a target orbit. The proposed strategy allows a rendezvous to a planet in an elliptical orbit by adjusting the launch timing of the sailcraft when it starts from a circular orbit. Numerical simulations demonstrate the validity of the proposed procedure.

DOI： 10.2514/6.2010-8137

Language：English   Publishing type：Research paper (international conference proceedings)  

This study deals with a multi-legged planetary rover with a spherically isotropic leg arrangement. This robot is a reliable system for the exploration on rough terrains, because the rover can continue walking even after overturning. Moreover, this rover can exhibit a rotational motion by utilizing its isotropic shape in addition to quadruped walking motion. This paper discusses two rotational motions; a quasi-static rotational motion and a dynamic rotational motion. This paper investigates reasonable attitudes for the quasi-static rotational motion from the view point of the energy consumption required for traveling. For the dynamic rotational motion, adequate attitudes to resist the shock for kicking and touchdown are discussed.

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (international conference proceedings)  

This paper proposes a method for designing a rendezvous trajectory for active debris removal using Lambert's problem. For the active debris removal mission, it is preferable to remove multiple target debris in sequence during a single mission with a low required ΔV. The trajectory design process for the removal mission consists of the following three steps: selection of the removal target debris from among many candidates; specification of the rendezvous order for the chosen debris; and design of the rendezvous transfer orbits. Since Lambert's problem has multiple solutions, the design process requires a large number of computations. By limiting the debris removal mission to low-Earth orbit, this paper proposes a procedure to specify a unique solution for Lambert's problem. To demonstrate the feasibility of the proposed procedure, this paper deals with a simple rendezvous for three debris as an example, and applies a genetic algorithm to find a solution having a reasonable ΔV with low calculation cost. Numerical results show that the proposed design procedure can find a reasonable solution for the multiple rendezvous problem.

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (international conference proceedings)  

This paper proposes a feedback control method for the in-plane motion of a satellite equipped with two thrusters, whose force directions are fixed to the satellite. The satellite's equations of motion have second-order nonholonomic constraints. This paper utilizes an invariant manifold and develops a feedback controller based on the Lyapunov's second method. The developed controller can control the satellite's state composed of six components for the position and attitude angle by two thruster systems. Furthermore, the controller has robustness for the system's modeling errors. Some simulations results are shown to demonstrate the effectiveness of the developed controller.

Language：English   Publishing type：Research paper (scientific journal)  

This paper deals with in-plane motion of a solar sail spacecraft to rendezvous with a planet. In the interplanetary rendezvous problem, the spacecraft's velocity must coincide with the orbital velocity of the planet when it reaches the planet's orbit. Thus, the spacecraft's radial and tangential velocities as well as its orbital radius are controlled by one control input, i.e. the spacecraft's pitch angle. In this paper, we propose a trajectory design method which can reduce the amount of computational iterations considerably. This is applied to a rendezvous mission to a planet in a circular orbit and is achieved by utilizing locally optimal control techniques. A hidden problem in the method is pointed out, and a countermeasure is proposed. Then, numerical results of the proposed method are shown and compared with the results obtained by a fully numerical iteration method. Finally, some mathematical properties of a sailcraft's governing equations are discussed in the framework of nonlinear control theory. We show analytically that a solar sail spacecraft can rendezvous with any planet in any elliptical orbit by using only pitch angle control.

DOI： 10.2322/tstj.7.Pd_37

Language：English   Publishing type：Research paper (scientific journal)  

This paper discusses the in-planar and out-of-planar dynamics of a Tethered Satellite System (TSS), which aims to inject a satellite into a different orbit plane. The orbital transfer is achieved by only varying the tether length in a gravity gradient field. A previous work treating in-plane orbital transfer induces the system's pitch motion, and proposes a control procedure. For a transfer in a different orbit plane, the system's roll motion must be controlled as well as its pitch motion. First, this paper shows the system's governing equations of motion, and compares the features of the roll motion with its pitch motion. Then, a control method is proposed to increase the angular momentum of the roll motion. Finally, the effectiveness of the proposed method is demonstrated by numerical simulations.

DOI： 10.2322/tstj.7.Pd_57

Language：Japanese   Publishing type：Research paper (scientific journal)  

Feedback Control for Satellite Orbit Transfer by a Tethered Satellite System

DOI： 10.2322/jjsass.57.301

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (international conference proceedings)  

This study deals with the in-plane motion of a free-floating planar satellite equipped with two thrusters whose force directions are fixed with respect to the satellite. The system's governing equations form non-integrable second-order "nonholonomic" constraints due to the fixed force directions within the satellite. First, this paper shows the general expressions of the system's equations of motion, and shows that its translational and rotational motions can not be controlled independently. Next, by assuming an imaginary thruster controlled by a feedback law, we transform the nonholonomic constraints into holonomic ones. This concept is followed by a strategy to achieve a rotational motion without drift for a satellite system with two fixed thrusters. Afterwards, this paper shows a procedure for precise control of the position and attitude of the system. The validity of the proposed method is verified by numerical simulations. Finally, this paper discusses the special case when the magnitude of the thruster force is taken constant.

DOI： 10.2514/6.2009-6183

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：Japanese   Publishing type：Research paper (scientific journal)  

Orbital Transfer of a Tethered Satellite System Using Pitching Motion Control through Tether Length Variation

DOI： 10.2322/jjsass.56.308

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：Japanese   Publishing type：Research paper (scientific journal)  

Feedback Control of Orbital Parameters for a Rigid Satellite under Nonholonomic Constraint

DOI： 10.2322/jjsass.56.1

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (international conference proceedings)  

This study deals with orbital control of a rigid coplanar dumbbell-type satellite system. While most of the previous work for orbital transfer aim at changing just one parameter of the orbital elements, by applying a nonlinear method, this study proposes two control laws to change an orbit into a prescribed one defined by its orbital elements: semi-major axis (equivalent to semilatus rectum), eccentricity and argument of pericenter. First controller is developed from a two-step approach combining a solution for a chained formed system and numerical modification based on motion planning. Another is a feedback controller, which can compensate model uncertainty or disturbance. These two controllers can be combined to a complementary control technique. The effectiveness of the proposed control laws are demonstrated through a series of numerical simulations.

DOI： 10.2514/6.2007-6849

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (international conference proceedings)  

This study deals with feedback control of reorientation of a planar space robot. Mukherjee and Kamon propose to define 'a radially isometric orientation' and successfully establish a smooth time invariant control system. However the proposed controller suffers from slow rate of convergence for a desired configuration being placed on or near a zero-holonomy curve. They also propose two modified controllers for such configurations, but stability problem for the modified controllers remains future work and a criterion for choosing the original or modified controller is not discussed for general configurations. This paper proposes to adopt a 'moving desired configuration' for convergence to any desired configuration. The moving desired configuration is designed to move to a 'real' desired configuration with the system states close to an invariant manifold. The paper describes how to define the invariant manifold and how to move the moving desired point to the real one.

DOI： 10.2514/6.2006-6519

Language：English   Publishing type：Research paper (international conference proceedings)  

This study deals with orbital transfer of a tethered satellite system into a specified orbit (defined in the equatorial plane as a set of semilatus rectum, eccentricity, and augment of pericenter,) by using tether-length variations. While in the 55th IAC conference the tethered satellite system was assumed as a rigid dumbbell type satellite, the tethered satellite system dealt in this paper is not rigid, and the system has only one control input: tether-length variation. By comparing the nature of the systems to that of rigid satellite systems, this paper points out that the timing of changing the tether length on its orbital motion is a key of orbital transfer. And controllability of the system is discussed numerically by examining the distribution of the control effect.

Language：English   Publishing type：Research paper (international conference proceedings)  

This study deals with orbital control of a rigid dumbbell-type satellite system. While most of the previous works for orbital transfer aim at changing just one parameter of the orbital element or the orbital energy, in this study the system is transferred by using its inner force into a prescribed orbit defined as a set of orbital elements: semilatus rectum, eccentricity, and argument of pericenter. By applying nonlinear control theories, it is shown that the satellite system is controllable except its pericenter and its apocenter in the elliptic orbit. Then, this paper transforms the nonlinear governing equations into a canonical system, called 'a chained system', and demonstrates that a specified orbit is accomplished by appropriately shaped time histories of control inputs.

Language：Japanese   Publishing type：Research paper (scientific journal)  

Considerations for Control of Planar Space Robot using Manifolds

DOI： 10.7210/jrsj.23.594

Language：English   Publishing type：Research paper (international conference proceedings)  

This study deals with orbital transfer of a tethered satellite system (TSS) on orbit. Dynamics of TSS is restricted to the angular momentum conservation law of the system around a planet. This constraint is not integrable (, that is called "nonholonomic constraint"), and the final state of TSS depends on a time history of the input. While previous works for orbital transfer mainly investigated dynamics of the system for specified time profiles of the tether-length, this study aims to make tether extension profiles to achieve some specified orbit. This paper, as a preliminary study, gives a brief overview of the previous works and investigates the fundamental property of the constraint based on the angular momentum conservation. Integrability and accessibility /controllability are analyzed and also numerically verified. For simplicity, TSS is modeled to a dumbbell-type satellite in this study.

Language：English   Publishing type：Research paper (international conference proceedings)  

An Autonomous Path Planning of a Rover Utilizing Multi-Image Shape from Shading

Language：English   Publishing type：Research paper (international conference proceedings)  

It is known that the manipulators with free-joints are typical mechanical systems dominated by second-order nonholonomic constraints. This paper points out that only the second-order nonholonomic constraint at the first free-joint of the manipulator is integrable to first-order constraint, and that the integrated constraint has linear form of generalized velocities. This constraint implies that a planar manipulator whose first joint is replaced to a free-joint driven by a reaction wheel can be controlled using the same control strategy as that used for the original manipulator. Integrability of the resulting first-order constraint is also discussed for different planar manipulators with free-joints, and the usefulness of the first-order nonholo-nomic constraint is demonstrated numerically in a path-planning problem for a manipulator with two free-joints.

Language：English   Publishing type：Research paper (international conference proceedings)  

Dynamical Interaction of a Tethered Space Robot

Language：English   Publishing type：Research paper (international conference proceedings)  

For planetary exploration, path planning for a rover is one of the important missions. This paper deals with Shape from Shading (SfS) scheme for estimation of planet terrain. As a reliable reflectance model of a surface, the Hapke model is formed in the world of remote sensing. This paper proposes to utilize the Hapke model in the SfS algorithm for multiple camera images. Since the Hapke model has singularity when the gradient vector of a surface element is coincident with a certain direction, the model is modified not to show the singularity. As a result, the SfS algorithm is applicable to multiple camera images and valid regardless of the degree of albedo of the surface. Applying the proposed SfS algorithm for multiple images, an autonomous path planning based on Dynamic Programming is shown. The effectiveness of the proposed scheme is investigated in numerical simulations, and some discussion about the results is presented.

Language：English   Publishing type：Research paper (scientific journal)  

Dynamics and Control of a Tethered Space Robot with Tension

Language：English   Publishing type：Research paper (international conference proceedings)  

Dynamic Behavior of a Multi-Legged Planetary Rover of Isotropic Shape

Language：English   Publishing type：Research paper (international conference proceedings)  

Fundamental Abilities of Multi-Legged Rover with Isotropic Shape

Language：Japanese   Publishing type：Research paper (scientific journal)  

Torque-Unit-Manipulator Driven by Control Moment Gyros

Language：Japanese   Publishing type：Research paper (scientific journal)  

Torque-Unit-Manipulator Driven by Control Moment Gyros

Language：English   Publishing type：Research paper (international conference proceedings)  

Path Planning for a Space Robot Using Surface Integral Map

Language：English   Publishing type：Research paper (scientific journal)  

Formulation and Control of a Flexible Space-Based Robot with Slewing-Deployable Links

DOI： 10.1016/S0094-5765(98)00040-X

Language：English   Publishing type：Research paper (scientific journal)  

The present study deals with a space-based variable geometry mobile manipulator with an arbitrary number of modules, each with two flexible links: one of them free to slew (revolute joint); and the other deployable (prismatic joint). The versatile manipulator has several attractive features: favorable obstacle avoidance, absence of singular configurations, reduced inertia coupling, relatively simpler inverse kinematics as well as governing equations of motion, to mention a few. To begin with, derivation of the governing equations of motion, using the Lagrangian procedure, is explained. As can be expected, the recursive equations are highly nonlinear, nonautonomous and coupled. This is followed by the development of a numerical algorithm leading to the solution for the inverse kinematics. Finally, some typical simulation results for trajectory control of the end-effector using the resolved acceleration approach are presented. They clearly emphasize importance of the control strategy based on the flexible manipulator model.

DOI： 10.1016/S0094-5765(98)00040-X

Language：English   Publishing type：Research paper (scientific journal)  

This paper deals with a space manipulator which is called Torque-Unit-Manipulator (TUM) : TUM separates its actuator called torque unit from its joints; i.e., torque unit is placed on an arbitrary place on a link, and each rotational joint is a free joint. The TUM proposed in the previous work, however, is driven by reaction wheels, and thus it has a problem to be solved : the angular velocity of the reaction wheel may saturate when external force disturbs the posture of the TUM repeatedly. The reason is that the reaction wheels accumulate angular momentum during the maneuver because of non-holonomic constraint for the free joints. Therefore, TUM driven by Control Moment Gyros (CMGs) is proposed in this paper. For the proposed TUM, an asymptotically stable controller can be designed through Lyapunov's approach, and besides the gimbal angular velocity of the CMG returns to zero after each maneuver. The dynamics of the proposed TUM is computed in numerical simulation, and the effectiveness of the designed controller is shown.

DOI： 10.1299/kikaic.64.4292

Language：English   Publishing type：Research paper (scientific journal)  

This paper deals with a space manipulator which is called Torque-Unit-Manipulator (TUM): TUM separates its actuator called torque unit from its joint: i.e., torque unit is placed on an arbitrary place on a link, and each rotational joint is a free joint. The TUM proposed in the previous work, however, is driven by reaction wheels, and thus it has a problem to be solved: the angular velocity of the reaction wheel may saturate when repeated external force disturbs the posture of the TUM. The reason is that the reaction wheels accumulate angular momentum during the maneuver because of non-holonomic constraint for the free joints. Therefore, TUM driven by Control Moment Gyros (CMGs) is proposed in this paper. For the proposed TUM, an asymptotically stable controller can be designed through Lyapunov's approach, and besides this the gimbal angular velocity of the CMG returns to zero after each maneuver. The dynamics of the proposed TUM is computed in numerical simulation, and the effectiveness of the designed controller is shown.

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (scientific journal)  

Language：Japanese   Publishing type：Research paper (scientific journal)  

Language：Japanese   Publishing type：Research paper (scientific journal)  

Formulation and Dynamics of Flexible Space Robots with Deployable Links

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

This paper deals with a manipulator interconnected by an arbitrary number of modules, each with a flexible slewing link and a flexible deployable link. This manipulator has several inherent advantages compared to a manipulator connected by rotational joints. The two main ones are that integration of modules leads to a variable geometry manipulator with favorable obstacle avoidance and redundancy characteristics, and that there are no singular positions as in the revolute type manipulator. The equations of motion of the manipulator are derived from Lagrange's equations for the quasicoordinates using the elastic deformation modes orthogonal to the translational displacements. The total amount of calculation for the control torque is proportional to the number of links. Finally, to verify the validity of the derived equation and the computer program, the conservation of energy in a few dynamics problems is checked numerically.

DOI： 10.1299/kikaic.62.1495

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

This paper proposes a new control technique, based on the low authority control/ high authority control (LAC/HAC) concept, to suppress the vibration of flexible space structures. The control system designed by the new control technique has a mechanism to adjust the HAC feedback gain between zero and one in such a manner as to enhance the effectiveness of control and to obtain global stability even when the magnitude of the LAC gain is not suitable. The paper first describes the theoretical mechanism of the new control technique and proposes a numerical method for determining the HAC feedback gain based on a neural network system. Then it shows the characteristic features of the new technique by computer simulation examples. The computer simulation shows that the new technique is quite effective in suppressing the spillover effects, and quite feasible for implementation.

DOI： 10.1299/jsmec1993.37.431

Language：Japanese   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (scientific journal)  

In this paper a new control technique based on the LAC/HAC concept is proposed to suppress the vibration of flexible space structures. The new technique employs the mechanism to turn on or off the HAC part of the LAC/HAC system in such a manner as to suppress the spillover effects as quickly as possible. The control system designed by the new technique has global stability and is more effective than a pure LAC system, even when an ordinary LAC/HAC system results in failure because of spillover instability. To show the characteristics features of the new technique and how to implement the system, computer simulation examples are given. Finally, the technique is applied to the transversal vibration control of a cantilever beam to show its effectiveness and practicality.

Language：Japanese   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：Japanese   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

In this paper a new control technique based on the LAC/HAC concept is proposed to suppress the vibration of flexible space structures. The new technique employs the mechanism to turn on or off the HAC part of the LAC/HAC system in such a manner as to suppress the spillover effects as quickly as possible. The control system designed by the new technique has global stability and is more effective than a pure LAC system, even when an ordinary LAC/HAC system results in failure because of spillover instability. To show the characteristic features of the new technique and how to implement the system, computer simulation examples are given. Finally, the technique is applied to the transversal vibration control of a cantilever beam to show its effectiveness and practicality.

Language：Japanese   Publishing type：Research paper (scientific journal)  

Language：Japanese   Publishing type：Research paper (scientific journal)  

A New Control Technique Based on the LAC/HAC Concept for Flexible Structures.

DOI： 10.2322/jjsass1969.39.686

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：Japanese   Publishing type：Research paper (scientific journal)  

Language：Others   Publishing type：Research paper (scientific journal)  

Modal instability due to spillover is investigated for a flexible vibration control system that employs a modal filter as a state estimator. First the characteristic equation of the system equipped with actuators, sensors and a modal filter is derived in a determinantal form. Then it is shown that the characteristic equation can be expanded. By applying the perturbation technique to the expanded characteristic equation, a criterion is obtained to predict whether a residual mode become stable or unstable. Using the criterion, it is mathematically proved that the control system equipped with one actuator and one sensor always has unstable modes if they are non-colocated.

DOI： 10.5687/iscie.3.414

Language：English   Publishing type：Research paper (bulletin of university, research institution)  

Modal instability due to spillover is investigated of a flexible vibration control system that employs a modal filter as the state estimator. First the characteristic equation of the closed-loop system containing actuators, sensors and a modal filter is derived in a determinantal form. Then it is shown that the characteristic equation can be expanded in a mathematically tractable form. By applying the perturbation technique to the expanded characteristic equation, a criterion is obtained that determines whether or not a residual mode is destabilized. Finally it is proved through the use of the criterion that the control system equipped with one actuator and one sensor always has unstable modes if they are non-colocated.

Language：Japanese   Publishing type：Research paper (scientific journal)  

Language：Others   Publishing type：Research paper (scientific journal)  

Precise attitude and shape control of flexible spacecraft requires active control of flexural vibrations. This paper first derives a general closed loop characteristic equation of a flexural vibration control system equipped with arbitrary numbers of non-point actuators and sensors whose regions of actions and observations are expressed by weight functions. Then, the characteristic equation in a determinantal form is expanded in a mathematically tractable form in which each coefficient is a product of an actuator-dependent determinant, a sensor-dependent determinant and a compensator-dependent determinant. By applying the perturbation technique to the expanded characteristic equation, it is shown that a modal stabilizing condition can be obtained for a rate and position feedback control system. Finally, a numerical example is given to illustrate the usage of the condition.

DOI： 10.5687/iscie.2.343

Language：Japanese   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Precise attitude and shape control of flexible spacecraft requires active control of flexural vibrations. This paper is concerned with the root locus method applied to active vibration control systems for a certain class of flexible bodies. A general characteristic equation is derived for a feedback system to control flexural vibrations with arbitrary numbers of sensors and actuators. Then it is shown, for the first time, that the characteristic equation in determinantal form may be reduced to a mathematically tractable form. It is also shown that under the condition of colocation of sensors and actuators the characteristic equation assumes a form in which the significance of this condition can be readily appreciated. Finally, the paper presents a numerical study to illustrate a practical procedure applying the root locus method to flexural vibration control systems.

Language：English   Publishing type：Research paper (scientific journal)  

Event date： 2008.11

Country：Japan  

Event date： 2008.8

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Venue：Hokkaido   Country：Japan  

Event date： 2008.8

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Event date： 2008.8

Venue：Hokkaido   Country：Japan  

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Event date： 2008.7

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Event date： 2008.7

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Event date： 2008.7

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Event date： 2008.6

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Event date： 2008.5 - 2009.5

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