Research On Trajectory Tracking Control Of 3-DOF Parallel Manipulator Leg

Aiming at the control problem of 3-DOF parallel manipulator leg,this paper explores and studies the establishment of system dynamics model,the trajectory planning at the end of manipulator leg and the trajectory tracking control.Parallel legs have been gradually applied to the mechanism design of foot robots because of their advantages such as high load-carrying capacity,high motion accuracy and flexible mechanism configuration.However,because of its complex mathematical model,the difficulty of control is increased.Therefore,the research on mathematical modeling,trajectory planning and control strategy of 3-DOF parallel manipulator leg has important theoretical value and practical significance.The main work of this paper is as follows:Firstly,on the basis of nominal dynamics model,considering external uncertainties,unmodeled dynamics of the system and friction between driving mechanism and transmission mechanism,a complete dynamic model of 3-DOF parallel manipulator leg is established.Through geometric analysis of the mechanism,the forward and inverse position solutions of the end of the mechanism are derived.The foot trajectory of the robot is planned,and the planned trajectory is taken as the reference trajectory in the trajectory tracking control.Secondly,for the trajectory tracking control of the 3-DOF parallel manipulator leg affected by external uncertainties,an inverse sliding mode control based on non-singular fast terminal sliding surface is designed,and an adaptive law is introduced into the control to ensure the stability of the system and improve the robustness of the control system.The stability of the system is proved by constructing Lyapunov function,and is verified by simulation with MATLAB.Thirdly,aiming at the chattering phenomenon in sliding mode variable structure control,the causes of chattering and the methods of eliminating chattering are analyzed,and an improved exponential reaching law is designed,and the reachability of the improved reaching law is analyzed.Considering the influence of external disturbance and unmodeled dynamics,an improved reaching law global terminal sliding mode control based on nominal model is proposed.The stability of the system is proved by constructing Lyapunov function and verified by simulation.Finally,a fuzzy adaptive robust control based on dead-time compensation is designed to solve the problem of dead-time caused by friction term in the complete dynamic model of 3-DOF parallel manipulator leg.The stability of the system is proved by constructing Lyapunov function.Aiming at whether dead-time compensation is considered,the PD controller and the fuzzy adaptive robust control based on dead-time compensation are designed.The PD control is used for the controller without dead-time compensation,and the adaptive robust control based on fuzzy compensation is used for the controller with dead-time compensation.The simulation results show that the adaptive robust control based on fuzzy compensation is effective.