Because control moment gyroscopes (CMGs) are capable of generating a much larger control torque f... more Because control moment gyroscopes (CMGs) are capable of generating a much larger control torque for attitude maneuvers than can reaction wheels (RWs), vibration becomes a significant issue for flexible structures such as solar paddles. This paper presents an integrated feedback/feedforward control system for reducing the vibration of flexible structures, as well as for completing a rapid, large-angle attitude maneuver of the spacecraft. The proposed Lyapunov control integrated with the Nil-Mode-Exciting (NME) profiler and an extended Input Shaping (IS) technique effectively improves the transient vibration of the modal response. The results of numerical simulations, based on the dynamics model of a typical flexible spacecraft, are shown for demonstrating the capability of the proposed control designs. In order to attenuate the residual vibration of the flexible structure more effectively, a new method is proposed for generating the feedforward input torque, i.e., the integrated NME profiler and Input Shaping. The integrated Lyapunov control using this input shaper is most effective in suppressing the transient vibration of the modal responses.
This paper presents the input shaping technique for reducing the vibrations of flexible structure... more This paper presents the input shaping technique for reducing the vibrations of flexible structures under attitude control inputs applied to the flexible spacecraft. The input shaping profile is investigated for the effective suppression of transient vibrations of modal responses. It is applied to the input commands to minimize the residual vibrations and suppress the overshoot of the modal responses. The results of numerical simulations, using a simple dynamic model of a flexible spacecraft, show that the input shaping technique is useful for suppressing the residual vibrations caused by attitude maneuvers.
Proceedings International Conference on Motion and Vibration Control, 2002
Uncertainties in the dynamics model ofa smart structure are often of significance due to model er... more Uncertainties in the dynamics model ofa smart structure are often of significance due to model errors caused by parameter ldentification errors and reduced-order modeling of the system. Design of a model-based FDI (Failure Detection and Isolation) system for smart structures, therefore, needs a carefu1 consideration about robustness with respect to such model uncertainties. This paper proposes a new method of robust fault detection that is insensitive to the disturbances caused by unknown modeling errors while it is highly sensitiye to the component failures. Capability of the robust detection algorithm is examined for the sensor failure of a flexible smart bearn control system. It is shown by numerical simulations that the proposed method suppresses the disturbances due to mode} errors and remarkably improves the detection perforrnance.
International Symposium on Artificial Intelligence, Aug 1, 2005
A cluster of small-sized single-gimbal control moment gyros (SGCMGs) is proposed as an attitude c... more A cluster of small-sized single-gimbal control moment gyros (SGCMGs) is proposed as an attitude control actuator for high-speed maneuver of small satellites. Singularity problem of the system of 4-SGCMGs in pyramid configuration is investigated to show the singularity surfaces in the three-dimensional angular momentum space. This paper presents a simple singularity avoidance control logic using the singular value decomposition algorithm. Capability of the present steering method in singularity avoidance is demonstrated with numerical simulations for attitude control of a small satellite. .
A self-sensing actuator is known to be effective for the vibration control of flexible structures... more A self-sensing actuator is known to be effective for the vibration control of flexible structures. Currently, a self-sensing piezoelectric actuator is implemented by using a tuned bridge circuit. This circuit easily becomes unbalanced because of the variation in the piezoelectric capacitance, which is sensitive to ambient temperature. If the bridge circuit is unbalanced, the closed-loop system becomes unstable. In this
Journal of Intelligent Material Systems and Structures, May 14, 2020
The application of adaptive structures (smart structures) in ultrahigh precision space structures... more The application of adaptive structures (smart structures) in ultrahigh precision space structures such as X-ray astronomical satellites is being studied extensively. To ensure the reliability of such ultrahigh precision space structures, it is necessary to introduce an automated fault diagnosis system. In this study, the Taguchi method (Mahalanobis-Taguchi system) is applied to the self-diagnosis problem, wherein a damage in the smart structure is detected using the vibration response data of a smart beam. This article reports on the preliminary results of hardware experiments using a smart beam model in the laboratory.
Journal of Intelligent Material Systems and Structures, Dec 2, 2013
A semi-active vibration suppression system is developed for flexible structures. The vibration su... more A semi-active vibration suppression system is developed for flexible structures. The vibration suppression system comprises bimorph piezoelectric ceramic tiles shunted by a resistor–inductor electrical circuit with a switching component. The vibration suppression control is designed by tuning the optimal resistance and inductance parameters of the shunted resistor–inductor network. In this article, we propose a semi-active vibration control technique to improve the damping effect while maintaining the stability of the passive control system. The proposed control law is similar to a sliding-mode control that accelerates the convergence of the system using switching functions. This study shows that the resonant circuit functions as a type of dynamic damper for mechanical systems and that the sliding-mode control is very effective for damping the multi-mode responses. The results of the numerical simulations of a cantilevered beam show that a semi-active vibration control system is more effective in damping vibrations than a passive control system. A hardware demonstration based on a laboratory model has also been carried out. The preliminary results of the experiment show that the system is sensitive to the noise, and improved implementation of the switching circuit is needed for practical application.
This work proposes a new method for measuring the position and attitude of an autonomous land veh... more This work proposes a new method for measuring the position and attitude of an autonomous land vehicle navigating in a rough terrain. The measurement system proposed here provides precise information on position and heading quickly and continuously. It consists of two laser scanners mounted on the vehicle and corner cubes placed in the environment as landmarks. Each laser scanner rotates
Inpllt shaping refers し o a ． pa ． rticu 玉 ar command shaping technique that explQits the convolu... more Inpllt shaping refers し o a ． pa ． rticu 玉 ar command shaping technique that explQits the convolution of the referellce signal with a sequence of impulses to reduce the systenl vibrations ， The method requires only estimates of 癒 e Ilatural frequelicies and dampirlg rati ． Not on ！ y vibration eduction of tlle fiexil)le structure ， tracking of tra ． jectory is important in も he fields of boも h sp れcecraft dynamics and rQbotics ， This paper presents a n エethod of inpu し 一 shaped control β or a flexible manipulat 1 ・ ， and shows by numerical silnulations that the comrnand input shaping technique is llighly effeci ！ ive fbr the near −minimurrl −time t− rackirt9 (： OlltI ' ol ． Key LVords ： inpu 七 shaping ， trajectory tracking ， flexible manipulator ，
Because control moment gyroscopes (CMGs) are capable of generating a much larger control torque f... more Because control moment gyroscopes (CMGs) are capable of generating a much larger control torque for attitude maneuvers than can reaction wheels (RWs), vibration becomes a significant issue for flexible structures such as solar paddles. This paper presents an integrated feedback/feedforward control system for reducing the vibration of flexible structures, as well as for completing a rapid, large-angle attitude maneuver of the spacecraft. The proposed Lyapunov control integrated with the Nil-Mode-Exciting (NME) profiler and an extended Input Shaping (IS) technique effectively improves the transient vibration of the modal response. The results of numerical simulations, based on the dynamics model of a typical flexible spacecraft, are shown for demonstrating the capability of the proposed control designs. In order to attenuate the residual vibration of the flexible structure more effectively, a new method is proposed for generating the feedforward input torque, i.e., the integrated NME profiler and Input Shaping. The integrated Lyapunov control using this input shaper is most effective in suppressing the transient vibration of the modal responses.
This paper presents the input shaping technique for reducing the vibrations of flexible structure... more This paper presents the input shaping technique for reducing the vibrations of flexible structures under attitude control inputs applied to the flexible spacecraft. The input shaping profile is investigated for the effective suppression of transient vibrations of modal responses. It is applied to the input commands to minimize the residual vibrations and suppress the overshoot of the modal responses. The results of numerical simulations, using a simple dynamic model of a flexible spacecraft, show that the input shaping technique is useful for suppressing the residual vibrations caused by attitude maneuvers.
Proceedings International Conference on Motion and Vibration Control, 2002
Uncertainties in the dynamics model ofa smart structure are often of significance due to model er... more Uncertainties in the dynamics model ofa smart structure are often of significance due to model errors caused by parameter ldentification errors and reduced-order modeling of the system. Design of a model-based FDI (Failure Detection and Isolation) system for smart structures, therefore, needs a carefu1 consideration about robustness with respect to such model uncertainties. This paper proposes a new method of robust fault detection that is insensitive to the disturbances caused by unknown modeling errors while it is highly sensitiye to the component failures. Capability of the robust detection algorithm is examined for the sensor failure of a flexible smart bearn control system. It is shown by numerical simulations that the proposed method suppresses the disturbances due to mode} errors and remarkably improves the detection perforrnance.
International Symposium on Artificial Intelligence, Aug 1, 2005
A cluster of small-sized single-gimbal control moment gyros (SGCMGs) is proposed as an attitude c... more A cluster of small-sized single-gimbal control moment gyros (SGCMGs) is proposed as an attitude control actuator for high-speed maneuver of small satellites. Singularity problem of the system of 4-SGCMGs in pyramid configuration is investigated to show the singularity surfaces in the three-dimensional angular momentum space. This paper presents a simple singularity avoidance control logic using the singular value decomposition algorithm. Capability of the present steering method in singularity avoidance is demonstrated with numerical simulations for attitude control of a small satellite. .
A self-sensing actuator is known to be effective for the vibration control of flexible structures... more A self-sensing actuator is known to be effective for the vibration control of flexible structures. Currently, a self-sensing piezoelectric actuator is implemented by using a tuned bridge circuit. This circuit easily becomes unbalanced because of the variation in the piezoelectric capacitance, which is sensitive to ambient temperature. If the bridge circuit is unbalanced, the closed-loop system becomes unstable. In this
Journal of Intelligent Material Systems and Structures, May 14, 2020
The application of adaptive structures (smart structures) in ultrahigh precision space structures... more The application of adaptive structures (smart structures) in ultrahigh precision space structures such as X-ray astronomical satellites is being studied extensively. To ensure the reliability of such ultrahigh precision space structures, it is necessary to introduce an automated fault diagnosis system. In this study, the Taguchi method (Mahalanobis-Taguchi system) is applied to the self-diagnosis problem, wherein a damage in the smart structure is detected using the vibration response data of a smart beam. This article reports on the preliminary results of hardware experiments using a smart beam model in the laboratory.
Journal of Intelligent Material Systems and Structures, Dec 2, 2013
A semi-active vibration suppression system is developed for flexible structures. The vibration su... more A semi-active vibration suppression system is developed for flexible structures. The vibration suppression system comprises bimorph piezoelectric ceramic tiles shunted by a resistor–inductor electrical circuit with a switching component. The vibration suppression control is designed by tuning the optimal resistance and inductance parameters of the shunted resistor–inductor network. In this article, we propose a semi-active vibration control technique to improve the damping effect while maintaining the stability of the passive control system. The proposed control law is similar to a sliding-mode control that accelerates the convergence of the system using switching functions. This study shows that the resonant circuit functions as a type of dynamic damper for mechanical systems and that the sliding-mode control is very effective for damping the multi-mode responses. The results of the numerical simulations of a cantilevered beam show that a semi-active vibration control system is more effective in damping vibrations than a passive control system. A hardware demonstration based on a laboratory model has also been carried out. The preliminary results of the experiment show that the system is sensitive to the noise, and improved implementation of the switching circuit is needed for practical application.
This work proposes a new method for measuring the position and attitude of an autonomous land veh... more This work proposes a new method for measuring the position and attitude of an autonomous land vehicle navigating in a rough terrain. The measurement system proposed here provides precise information on position and heading quickly and continuously. It consists of two laser scanners mounted on the vehicle and corner cubes placed in the environment as landmarks. Each laser scanner rotates
Inpllt shaping refers し o a ． pa ． rticu 玉 ar command shaping technique that explQits the convolu... more Inpllt shaping refers し o a ． pa ． rticu 玉 ar command shaping technique that explQits the convolution of the referellce signal with a sequence of impulses to reduce the systenl vibrations ， The method requires only estimates of 癒 e Ilatural frequelicies and dampirlg rati ． Not on ！ y vibration eduction of tlle fiexil)le structure ， tracking of tra ． jectory is important in も he fields of boも h sp れcecraft dynamics and rQbotics ， This paper presents a n エethod of inpu し 一 shaped control β or a flexible manipulat 1 ・ ， and shows by numerical silnulations that the comrnand input shaping technique is llighly effeci ！ ive fbr the near −minimurrl −time t− rackirt9 (： OlltI ' ol ． Key LVords ： inpu 七 shaping ， trajectory tracking ， flexible manipulator ，
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Papers by Hiroshi Okubo