The tracking of orientation and angular velocity is a primary attitude control task for an on-orbit spacecraft.The problem for a rigid spacecraft tracking a desired angular velocity profile is addressed using an adapt...The tracking of orientation and angular velocity is a primary attitude control task for an on-orbit spacecraft.The problem for a rigid spacecraft tracking a desired angular velocity profile is addressed using an adaptive feedback control.An angular velocity feedback tracking algorithm is firstly developed based on the precisely known attitude dynamics of the spacecraft,and the global tracking of the control algorithm is proved based on the Lyapunov analysis.An adaptation mechanism is then designed to deal with the dynamic uncertainties of the spacecraft.Such an adaptation mechanism enables the controller to track any desired angular velocity trajectories even in the presence of uncertain inertia parameters,although it does not guarantee the inertia tensor being precisely identified.To verify the effectiveness of the proposed adaptive control policy,computer simulations on dynamic equations of a spacecraft are conducted and their results are discussed.展开更多
Super depth digital microscope was employed to observe the macro-/micro-structure of Coleoptera's elytra.The non-smooth surface textures of elytra have shown superior performance of friction reduction and lubricat...Super depth digital microscope was employed to observe the macro-/micro-structure of Coleoptera's elytra.The non-smooth surface textures of elytra have shown superior performance of friction reduction and lubrication.Bionic models of regular hexagonal convex texture and circular concave texture inspired by the beetle were established and verified by numerical calculations and simulations.Further tribological experiments were performed and the results show that the circle texture has the lowest coefficient,which is consistent with the numerical calculations.The research may be further applied to new bionic surface texture designs and also work as a biological template for new bionic inventions.展开更多
An experimental study of an active body-weight support（BWS） system for improving treadmill-based locomotion training is performed.The dynamical foundation of the proposed system is developed based on a simplified ca...An experimental study of an active body-weight support（BWS） system for improving treadmill-based locomotion training is performed.The dynamical foundation of the proposed system is developed based on a simplified cable suspended mass-spring-damping system which is used to mimic the vertical gait of a walking human.A specifically designed cable pulley suspended cam-slider system is used to mimic the walking gait of a human in vertical direction.A load cell is installed to connect the slider and the cable which is driven by a winch based on the acceleration feedback.The contact force between the slider and the cam is measured to evaluate the walking load of the system.The experimental results demonstrate that the proposed active BWS system can simultaneously reduce both gravitational and inertial load of the walking body,which implies that the walking body suspended in such a BWS system will dynamically behave as if certain amount of body mass had been removed.展开更多
基金Supported by the Innovation Fund of Shanghai Aerospace Science and Technology(SAST 201308)
文摘The tracking of orientation and angular velocity is a primary attitude control task for an on-orbit spacecraft.The problem for a rigid spacecraft tracking a desired angular velocity profile is addressed using an adaptive feedback control.An angular velocity feedback tracking algorithm is firstly developed based on the precisely known attitude dynamics of the spacecraft,and the global tracking of the control algorithm is proved based on the Lyapunov analysis.An adaptation mechanism is then designed to deal with the dynamic uncertainties of the spacecraft.Such an adaptation mechanism enables the controller to track any desired angular velocity trajectories even in the presence of uncertain inertia parameters,although it does not guarantee the inertia tensor being precisely identified.To verify the effectiveness of the proposed adaptive control policy,computer simulations on dynamic equations of a spacecraft are conducted and their results are discussed.
基金supported in part by the National Natural Science Foundation of China(Nos.51175249,51475230)
文摘Super depth digital microscope was employed to observe the macro-/micro-structure of Coleoptera's elytra.The non-smooth surface textures of elytra have shown superior performance of friction reduction and lubrication.Bionic models of regular hexagonal convex texture and circular concave texture inspired by the beetle were established and verified by numerical calculations and simulations.Further tribological experiments were performed and the results show that the circle texture has the lowest coefficient,which is consistent with the numerical calculations.The research may be further applied to new bionic surface texture designs and also work as a biological template for new bionic inventions.
文摘An experimental study of an active body-weight support（BWS） system for improving treadmill-based locomotion training is performed.The dynamical foundation of the proposed system is developed based on a simplified cable suspended mass-spring-damping system which is used to mimic the vertical gait of a walking human.A specifically designed cable pulley suspended cam-slider system is used to mimic the walking gait of a human in vertical direction.A load cell is installed to connect the slider and the cable which is driven by a winch based on the acceleration feedback.The contact force between the slider and the cam is measured to evaluate the walking load of the system.The experimental results demonstrate that the proposed active BWS system can simultaneously reduce both gravitational and inertial load of the walking body,which implies that the walking body suspended in such a BWS system will dynamically behave as if certain amount of body mass had been removed.
