Language：English   Publishing type：Research paper (scientific journal)   Publisher：Elsevier BV  

The controller optimization task is rarely spotlighted despite its importance for vehicle drivetrain mechanisms although many studies have been dedicated to developing vibration control strategies. Based on the adaptive grey wolf optimizer (AGWO), this research develops a fast-optimization scheme for a drivetrain oscillation control system that simultaneously addresses effects of nonlinear backlash. A drivetrain system model governed by a backlash nonlinearity is presented, and a baseline controller is derived for damping low-frequency drivetrain resonance based on the optimal H2 synthesis. The introduction of a time-dependent-switched Kalman filter realizes a solution for dealing with the nonlinear backlash issue, relying on straightforward controller-switching-based compensation for the backlash and contact modes. Optimal solutions for the control system parameters are efficiently obtained using AGWO. AGWO exhibits both global search capability and superior computational efficiency because of its systematic stopping criteria and adaptive exploration/exploitation parameter. This study improves the efficiency of optimizing active drivetrain vibration control by introducing the adaptive mechanism into the controller parameter tuning. Comparative experiments demonstrate that the AGWO-based scheme provides a sufficiently good controller with the fastest time.

DOI： 10.1016/j.mechmachtheory.2024.105825

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Institute of Electrical and Electronics Engineers (IEEE)  

DOI： 10.1109/tcyb.2024.3372989

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Elsevier BV  

DOI： 10.1016/j.isatra.2024.07.001

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SAGE Publications  

To address vehicle drivetrain vibrations that cause discomfort and poor drivability, this study proposes a new active damping strategy with simple backlash compensation based on the simultaneous perturbation stochastic approximation (SPSA) with norm-limited update vector. First, an experimental device developed for a simplified drivetrain mechanism is demonstrated. A mechanism for reproducing both the contact mode and the backlash mode is included in the device. For the contact mode, a model-based [Formula: see text] controller is employed as the baseline damping strategy. Further, to mitigate the backlash effect, a simple algorithm based on mode-switching-based compensation is used with the [Formula: see text] controller. In particular, for the critical controller parameters, this article presents a systematic design approach to search for their optimal values. The key parameters, which are needed for the backlash and contact mode controllers, are simultaneously auto-tuned using norm-limited update vector-based SPSA, which ensures the stability in the iterative tuning. The novelty of this study is that both the backlash mode controller and the contact mode controller are simultaneously optimized by the improved version of SPSA, thus realizing a comprehensive auto-tuning design of an active drivetrain damping system. Finally, the active controller is experimentally verified using the actual test device. Comparative studies show that the proposed approach significantly reduces drivetrain vibrations and is robust against fluctuations in the backlash.

DOI： 10.1177/14644193241243158

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Other Link： https://journals.sagepub.com/doi/full-xml/10.1177/14644193241243158

Language：English   Publishing type：Research paper (scientific journal)   Publisher：Informa UK Limited  

DOI： 10.1080/00207179.2024.2332539

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SAGE Publications  

To improve the performance and durability of vehicle components, efforts have been made to reduce driveline oscillations using advanced active control algorithms. However, existing methods often rely on subjective parameter adjustments, which can be burdensome for designers. This study introduces an effective tuning algorithm for a driveline vibration controller that accounts for nonlinear backlash effects. Initially, a driveline dynamics model is developed to focus on transient oscillations resulting from changes in driving force and the presence of nonlinear backlash. The backlash impact is incorporated into the model through a discontinuous dead-zone region. Two operational dynamics, which are the contact mode and the backlash mode, are considered. A dynamic output feedback [Formula: see text] controller is designed as a baseline controller to mitigate low-frequency resonance in the driveline. A solution for managing the nonlinear backlash challenges is introduced, involving the use of a simple control mode switching algorithm in conjunction with the controller. This algorithm relies on a time-dependent-switched Kalman filter. Additionally, the optimal settings for the parameters needed by the mode-switching algorithm are autonomously determined using the grey wolf optimizer (GWO). The proposed active controller can be implemented in real vehicles by using an on-vehicle acceleration sensor and electronic control unit (ECU). In a simulation environment, the vehicle body vibration is online fed back to the resultant controller, and an actuator is supposed to apply control commands to the driveline. The effectiveness of this newly proposed active controller is confirmed through comparative tests, revealing the superior vibration control.

DOI： 10.1177/09544070241240019

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Other Link： https://journals.sagepub.com/doi/full-xml/10.1177/09544070241240019

Publishing type：Research paper (scientific journal)   Publisher：Institute of Electrical and Electronics Engineers (IEEE)  

DOI： 10.1109/access.2024.3355541

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Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Elsevier BV  

DOI： 10.1016/j.ymssp.2023.110526

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Publishing type：Research paper (scientific journal)   Publisher：SAGE Publications  

To ensure comfortability and lifetime of components, transient vibrations in a vehicle powertrain must be suppressed. This study proposes a novel active vibration control strategy with straightforward fuzzy inference compensation for time-fluctuations of control periods of engines used as actuators. First, a model prediction algorithm including a sampled-data controller (SDC) is applied for addressing the maximal phase lag of the control input caused by the fluctuated control period. Fluctuated renewal timings of the control input that are deviated from those of the periodical operated SDC are defined by fuzzy sets. These fuzzy sets are expressed as “Nearly past timing” and “Nearly future timing.” Using a human-intuition-like fuzzy compensation with only four inference rules, unknown control inputs at fluctuated update timings are reasonably determined from such fuzzy sets and periodical control signals given by the SDC. Experiments using an actual test device are performed to investigate the damping performance of the proposed control scheme. The experimental tests demonstrate that the novel active damping strategy significantly reduces transient vibrations despite the fluctuated control period. Moreover, several different test conditions newly reveal the robustness of the fuzzy compensation against fluctuations of variable regions in the control periods.

DOI： 10.1177/09544070231178103

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Other Link： http://journals.sagepub.com/doi/full-xml/10.1177/09544070231178103

Language：English   Publishing type：Research paper (scientific journal)   Publisher：MDPI AG  

Dual-ball-screw feed drive systems (DBSFDSs) are designed for most high-end manufacturing equipment. However, the mismatch between the dynamic characteristic parameters (e.g., stiffness and inertia) and the P-PI cascade control method reduces the accuracy of the DBSFDSs owing to the structural characteristic changes in the motion. Moreover, the parameters of the P-PI cascade controller of the DBSFDSs are always the same even though the two axes have different dynamic characteristics, and it is difficult to tune two-axis parameters simultaneously. A new application of the combination of the grey wolf optimization (GWO) algorithm and the P-PI cascade controller is presented to solve these problems and enhance the motion performance of DBSFDSs. The novelty is that the flexible coupling model and dynamic stiffness obtained from the motor current can better represent the two-axis coupling dynamic characteristics, and the GWO algorithm is used to adjust the P-PI controller parameters to address variations in the positions of the moving parts and reflect characteristic differences between the two axes. Comparison of simulation and experimental results validated the superiority of the proposed controller over existing ones in practical applications, showing a decrease in the tracking error of the tool center and non-synchronization error of over 34% and 39%, respectively.

DOI： 10.3390/math11102259

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Institute of Electrical and Electronics Engineers (IEEE)  

DOI： 10.1109/access.2023.3310540

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Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：SAGE Publications  

This study experimentally verifies robustness of a model-free vibration controller based on a virtual controlled object (VCO) considering parametric uncertainty of actuator. A proof-mass actuator, which can be modeled as a single-degree-of-freedom (SDOF) system, is used. A VCO, which is defined as an SDOF structure, is introduced between a real controlled object and the actuator model. The parameters of the VCO are determined so as to achieve model-free vibration control. A state equation to derive the model-free controller is constructed using the two-degree-of-freedom (2DOF) structure composed of the actuator model and the VCO. The parametric uncertainty of the actuator is quantitatively characterized in the 2DOF structure. The mixed [Formula: see text] control theory is used to design a model-free controller. The vibration suppression performance and robustness to the actuator uncertainty of the proposed method are validated by experiments. Simulation studies are also conducted to enhance the validity of the experimental results. As a result, the proposed damping method exhibits good damping performance and strong robustness to the actuator uncertainty and characteristic changes in controlled object.

DOI： 10.1177/09544062221140814

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Other Link： http://journals.sagepub.com/doi/full-xml/10.1177/09544062221140814

Language：English   Publishing type：Research paper (scientific journal)   Publisher：Elsevier BV  

DOI： 10.1016/j.mechmachtheory.2022.104957

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Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Elsevier BV  

This study presents a simple active vibration controller with a self-tuning mechanism free from a mathematical model of an actual controlled object. First, a virtual controlled object (VCO), which is defined as a single-degree-of-freedom (SDOF) system, is inserted between an actuator model and an actual controlled object. Traditional model-based control theories are applied to a two-degree-of-freedom (2DOF) system composed of the actuator and the VCO instead of a model of the actual controlled object to realize a model-free vibration controller. Then a self-tuning method based on the simultaneous perturbation stochastic approximation (SPSA) is introduced to the VCO-based model-free controller to obtain sufficient damping performances for various controlled objects. The model-free controller design is easily achieved because the traditional model-based control theory can be applied to the 2DOF system composed of the actuator and the VCO. Moreover, the proposed self-tuning mechanism provides sufficient vibration suppression effects for various controlled objects without manual controller tunings. Simulation studies compare the damping performance of the VCO-based model-free adaptive control scheme with that of the conventional approach. The simulations employ five controlled objects with different structures and characteristics, including time-varying properties. The proposed control scheme provides better damping effects than the conventional method for all controlled objects.

DOI： 10.1016/j.ymssp.2022.108801

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER HEIDELBERG  

Purpose This study improves the robustness of the model- free controller based on a virtual structure. Additionally, the adverse interference between the proof-mass actuator resonance and a controlled object is investigated as it is not clarified in the previous studies.Methods and Results A virtual structure modeled as a SDOF system was inserted between the actuator and the actual controlled object. This achieved the indirect damping of the actual controlled object and model-free control. Vibration control simulations were conducted for various finite element models with a model-free H-infinity controller based on a virtual structure. The results demonstrate that the actuator resonance adversely affects the stability of the control system when the controlled object has a mode whose natural frequency is too close to that of the actuator. Therefore, a notch filter was applied to the model-free H-infinity controller design approach to suppress the resonance without affecting the damping performance. The improved controller with notch filter is more robust to the resonance of the actuator than the previous one.Conclusions The resonance of the proof-mass actuator adversely affects the stability of the control system composed of the previous model-free H-infinity controller when the low-order vibration mode of the actual controlled object is too close to the natural frequency of the actuator. Introducing a notch filter into the model-free approach based on a virtual structure effectively reduces the negative impact due to the resonance of the actuator and improves the robustness of the control system.

DOI： 10.1007/s42417-022-00436-9

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Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：ACADEMIC PRESS LTD- ELSEVIER SCIENCE LTD  

A parameter tuning technique without manual trial-and-error procedures is proposed for a controller in a model-free vibration control system based on a virtual controlled object (VCO), which is defined as a single-degree-of-freedom (SDOF) system. The model-free control system is constructed by inserting a VCO between the actuator and the actual controlled object. A reference controlled object (RCO), which is also expressed as an SDOF system, is defined for the configured model-free control system. Then the loss function, which is calculated using the RCO vibration control simulation results, is used to evaluate the vibration suppression performance. The simultaneous perturbation stochastic approximation (SPSA) adjusts the controller tuning parameters to minimize the loss function. The SPSA- and RCO-based tuning procedures automatically tune the model-free controller without manual trial-and-error procedures. Simulations and experiments demonstrate that a model-free linear quadratic regulator designed by the proposed approach provides sufficient vibration reduction.

DOI： 10.1016/j.ymssp.2021.108313

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Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：SAGE PUBLICATIONS LTD  

The purpose of this research is to construct a simple and practical controller design method, considering the actuator's parameter uncertainty, without using a model of controlled objects. I n this method, a controller is designed with an actuator model including a single-degree-of-freedom virtual structure inserted between actuator and controlled object, resulting in a model-free controller design. Furthermore, an H-infinity control problem is defined so that the actuator's parameter uncertainty is compensated by satisfying a robust stability condition. Because the actuator model including the virtual controlled object is a simple low-order system, and the actuator's parameter uncertainty is considered, a controller with high robustness to the actuator's parameter uncertainty can be designed based on traditional model-based control theory. The effectiveness of the proposed method is verified by both simulation and experiment.

DOI： 10.1177/1077546320940922

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Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC  

This study proposes an active vibration control method with a simple design process without using a plant model. The proposed method is robust against the actuator's parameter uncertainty. To realize model-free control of the controlled object, a virtual structure represented by a single-degree-of-freedom system is inserted between the controlled object and the actuator. A controller, which compensates for the uncertainties of the actuator's parameters, is designed using the sliding mode control theory. By designing a controller using a model composed of the virtual structure and the actuator, model-free design can be easily performed with few design variables. After the virtual structure is introduced, the controller can be designed using the same process as a traditional model-based control theory. An advantage of the sliding mode control system is it can provide high robustness against the uncertainty in the actuator's parameters. The robustness to the actuator's uncertainty and vibration suppression performance of the proposed method are verified by controlling a two-degree-of-freedom time-varying system. Finally, the applicability of the proposed method to an actual mechanical system is confirmed by vibration control experiments.

DOI： 10.1109/ACCESS.2020.3047810

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SAGE PUBLICATIONS LTD  

The purpose of this study is to develop a simple and practical controller design method without modeling controlled objects. In this technique, modeling of the controlled object is not necessary and a controller is designed with an actuator model, which includes a single-degree-of-freedom virtual structure inserted between the actuator and the controlled object. The parameters of the virtual structure are determined so that indirect active vibration suppression is effectively achieved by considering the frequency transfer function from the vibration response of the controlled object to that of the virtual structure. Since the actuator model, which includes a virtually controlled object, is a simple low-order system, a controller with high control performance can be designed by traditional model-based optimal control theory. In this research, a mixed H2/H infinity controller is designed considering both control performance and robust stability. The effectiveness of the proposed method is validated experimentally. The robustness of the controller is demonstrated by applying the same controller to various structures.

DOI： 10.1177/1077546320902348

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Event date： 2024.9

Language：Japanese   Presentation type：Oral presentation (general)  

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Event date： 2023.10 - 2023.11

Language：English   Presentation type：Oral presentation (general)  

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Event date： 2023.10 - 2023.11

Language：English   Presentation type：Oral presentation (general)  

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Event date： 2023.10

Language：Japanese   Presentation type：Oral presentation (general)  

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Event date： 2023.8

Language：Japanese   Presentation type：Oral presentation (general)  

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Event date： 2022.11

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Event date： 2022.11

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Event date： 2022.11

Language：English   Presentation type：Oral presentation (general)  

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Event date： 2022.9

Language：Japanese   Presentation type：Oral presentation (general)  

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Event date： 2021.12

Language：Japanese  

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Event date： 2021.11

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Event date： 2021

Language：English  

This study proposes a novel model-free vibration controller based on a virtual controlled object (VCO) considering actuator parameter uncertainty. A proof-mass actuator, which is modeled as a single-degree-of-freedom (SDOF) system, is employed. A VCO, which is defined as an SDOF system, is inserted between the actual controlled object and the actuator model. Considering frequency transfer characteristic from actual controlled object to VCO, setting appropriate parameters of the VCO realizes model-free control. A state equation to design the model-free controller is derived based on the two-degree-of-freedom (2DOF) system composed of the actuator model and the VCO. The actuator parameter uncertainty is quantitatively modeled in the 2DOF plant. Traditional mixed H2/H∞ control theory is applied for the uncertain plant to design a model-free controller with high damping performance and robustness to the actuator uncertainty. The effectiveness of the proposed controller is confirmed by vibration control experiments.

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Event date： 2020.11

Language：Japanese  

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Event date： 2020

Language：English  

The purpose of this study is to construct a simple controller design method considering actuator's parameter uncertainty without using a model of controlled objects. In this approach, a SDOF virtual structure is inserted between an actuator and a controlled object. The model-free design without the actual object model can be realized by designing a controller for the 2DOF system composed of the actuator and the virtual object. Both the high vibration control performance and robust stability against the actuator uncertainty are realized by applying a mixed H2/H∞ control theory. In the present approach, because the virtual object is a simple low-order model and traditional model-based control theory can be applied directly, the easier design process than previous model-free techniques offers a vibration controller with a high damping effect and the robustness with respect to the actuator uncertainty. Finally, the effectiveness of the proposed method is demonstrated by numerical simulations.

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Event date： 2019.8

Language：Japanese  

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Event date： 2019

Language：English  

There are some problems in model-based active vibration controls. It is required to maintain performance and stability of a closed-loop system when characteristics of a target structure change. In addition, the control performance and stability depend on the accuracy of the model. In this study, model-free vibration control system to enable vibration suppression of arbitrary structures is proposed. Vibration suppression can be realized by using the model of virtual structure corresponding to the controlled object. The effectiveness and robustness of the control system are validated by control simulations with several types of controlled objects using a unique mode-free controller.

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