Research On Vibration Control Of A Three Degree-of-Freedom Flexibel Parallel Manipulator

The vibration suppression of flexible manipulator can reduce the defection, vibration and noises in the high-speed motion. Furthermore, the vibration suppression is a good method to improve the motion track and positioning accuracy, to decrease opterating time of manipulator motion, to increase the efficiency of execution, and to avoid decreasing the performance and fatigue damage. It is widely used in aerospace, manufacturing, MEMS structures and medical therapy equipments.A three degree-of-freedom (3-DOF) parallel manipulator with three lightweight links is researched in this paper. The defection and vibration characteristics of the linkages of the manipulator are analyzed in detail when the manipulator is in the high-speed movement. It is systematically researched to how to suppress the vibration of the flexible linkages of the manipulator.The architecture and control system of the three degree-of-freedom parallel manipulator are introduced. The fixed coordinate system and moving coordinate system are established. The kinematics equations are created based on the inverse kinematics. The dynamic equations are established based on assumed mode method and beading vibration method. And the vibration modes of the manipulator are analyzed by ANSYS. The natural frequencies and damping ratio are obtained by the experiments and the simulation. And the modes of vibration are analyzed.The characteristics of PZT smart materials and basic control principle are introduced. The direct output feedback and the independent modal space active vibration control strategy based on the PZT sensors and actuators are presented. The vibration modal coupling behavior of the manipulator is analyzed. The control gain selection strategy for the modal controller is presented. The filters are developed for the online estimation of modal coordinates and modal velocity. An efficient multiple-mode PZT vibration control strategy is expressed.The vibration control system is set up using Lab VIEW Real-Time Module. Two-mode vibration control strategy of the three degree-of-freedom parallel manipulator is established. The experimental results demonstrate that the independent modal space controller and two-mode vibration controller can significantly suppress the vibration of the manipulator.The theories of the single-mode and multiple-mode positive impulses input shaping and the single-mode negative impulses input shaping based on the time-optimal are introduced. They are proposed to the theories and construction methods of the multiple-mode negative impulses input shaping based on the time-optimal. The positive impulses and negative impulses input shapers of the single-mode and two-mode of the three degree-of-freedom manipulator are established based on the Zero Vibration, Zero Vibration and Derivative and Extra Insensitive input shapers, separately. The performances of the vibration suppression, sensitive and delay-time of the output responses are expressed and analyzed. The results of analysis expressed the input shapers can effectively suppress the residual vibration of the manipulator, and the negative impulse input shapers can decrease the delay-time of the system response. Furthermore, the multiple-mode input shapers can effectively reduce the residual vibration of the manipulator with multiple modes.The errors of kinematic track of the three degree-of-freedom parallel manipulator are analyzed. And they are compared with the errors of kinematic track without vibration control. The kinematic accuracies of the manipulator with and without vibration control are analyzed based on the reliability method. The results show that the reliability for kinematic accuracy of the manipulator with vibration control is improved.