Research On Multi DOF Manipulator Based On Improved Active Disturbance Rejection Control

The increasingly powerful national comprehensive strength promotes the development of advanced control science and robot technology.In order to improve work efficiency,the multi degree of freedom manipulator arm has been widely used in industry and life.Positioning accuracy is the premise of multi degree of freedom manipulator to complete the work efficiently and accurately,so the control accuracy is an important index.However,due to the complex structure of multi degree of freedom manipulator,the interference of working environment and the existence of joint friction and other uncertain factors,the motion system is highly coupled,and the traditional control strategy can not meet the requirements of control accuracy.In this thesis,the control accuracy of multi degree of freedom manipulator is taken as the research object,and the control effect is expected to be stable.In order to improve the positioning accuracy,response speed and anti-interference ability of manipulator control,a multi degree of freedom manipulator control system based on active disturbance rejection control(ADRC)strategy is designed.Firstly,the working mode of the multi degree of freedom manipulator is introduced,and the working circuit of the manipulator joint actuator motor is analyzed.According to the running circuit and balance equation of the DC torque motor,the mathematical model of the DC torque motor is established through reasonable simplification and assumptions.Secondly,the mechanical structure of the multi degree of freedom manipulator is analyzed.The base of the manipulator is selected as the reference coordinate system of the whole system,and the transformation matrix of adjacent links is obtained by using the Denavit-Hartenberg four-parameter modeling method.The forward kinematics model of the multi degree of freedom manipulator is derived and calculated,and the dynamic equation of the multi degree of freedom manipulator is calculated based on Lagrange function.Then,the principle of ADRC mechanism is briefly introduced,and the structure of ADRC and its role in the controller are introduced.Nonlinear function plays a leading role in ADRC.Because the traditional nonlinear function is not differentiable around the origin,it is easy to appear the phenomenon of high frequency flutter.Therefore,a new type of nonlinear function is selected in the form of exponential and tangent function combination,which solves the problem of unsmooth and jitter at inflection point and has good robustness.Based on the new nonlinear function,the extended state observer and nonlinear error feedback control law are optimized.At the same time,Kalman filter is added in front of the extended state observer to estimate the disturbance and suppress the residual more accurately.Then,the stability of the improved ADRC is proved.Finally,under the same input signal,PID control,the traditional ADRC and the improved ADRC are compared and analyzed after the appropriate parameters are selected for the components of the controller.The simulation and experimental results show that the improved ADRC has faster response speed and stronger anti-jamming ability than the other two control methods,and realizes no overshoot tracking.The improved ADRC designed in this thesis is applied to the control system of multi degree of freedom manipulator,which has good dynamic performance.The control strategy can achieve good control effect in the case of internal and external interference.There is no overshoot,the response time is 0.018s,and the tracking error is within 60cts.This is of great significance to the research of linkage mechanism.