Research On Trajectory Planning And Trajectory Tracking Of Multi-joint Manipulator

With the national “Made in China 2025” put forward,industrial robots and other intelligent equipment will be the focus of future development.For industrial robot manipulators,trajectory planning and trajectory tracking provide important guarantee for their accurate and safe work.According to the specific tasks of a given target can accurately complete the planning trajectory of manipulator joint variables,then the mechanical arm trajectory tracking control,control input target driving torque can make the accurate tracking of the given manipulator.Therefore,trajectory planning and trajectory tracking are the basis of robot arm to complete a given task,and it has important research significance.Firstly,according to the Denavit-Hartenberg to establish the coordinate model of six degrees of freedom BO-6-3 manipulator and based on D-H parameters of each link of the relationship between the position of each joint is obtained,which can get the end effector position relative to the mechanical arm body by homogeneous transformation matrix to derive the manipulator kinematics equation and the brief process of obtaining inverse kinematics solution by geometry method is analyzed.Then this paper proposed based on differential evolution(Differential Evolution)to solve the optimization of BP manipulator neural network inverse kinematics method and compared with the BP neural network,the simulation results show that the inverse solution obtained by DE-BP neural network is of high accuracy.At the same time,the shortcomings of the traditional inverse kinematics solution are also analyzed.The trajectory planning of manipulator is carried out in joint space and Cartesian space respectively,in the joint space the joint angular value sequence is obtained by inverse kinematics and the five polynomial interpolation method is used,then the position,velocity and acceleration of the joint angle in the joint space are obtained.In Cartesian space,the linear interpolation method is used to complete the trajectory planning from the initial position to the termination position,and the target assignment is completed.Finally,the sliding mode variable structure control strategy with double power reaching law and modified terminal sliding surface is adopted,and trajectory tracking control of planar two DOF Manipulator is carried out.In view of the shortcomings of the traditional power reaching law,slow convergence speed and obvious chattering phenomenon,a sliding mode control method with double power reaching law is adopted to guarantee that the system can reach the sliding surface rapidly in a limited time.At the same time in the traditional terminal sliding mode to the position error of mechanical arm joint angle and velocity error tracking precision is low,it is also very difficult to control the state of the system when the system enters the sliding surface,prone to strong chattering phenomenon,so this paper adopts the modified terminal sliding mode surface.After the double power reaching law and the modified terminal sliding mode surface are combined,the control law of the manipulator system is deduced for the dynamic equations of the manipulator.It will make a comparative analysis of different approach laws in the case of the same sliding surface,similarly,the different sliding surfaces are compared and analyzed under the condition that the same approach law is selected.The simulation results show that the combination of the double power reaching law and the modified terminal sliding surface can keep the robot arm system robust stability and robustness in the presence of external disturbances.It improves the tracking accuracy of the robot arm and reduces chattering phenomenon of mechanical arm to a certain extent very effectively.