Path Following And Terminal Force Control Of Manipulators Based On Predictive Control

As a mechanical device that simulates a human arm,a mechanical arm is the main actuator of a robot.It can replace humans to complete some simple repetitive or dangerous work.Since the advent of the first robotic arm,after more than 60 years of development,it has been widely used in industrial production,medical surgery,and manned spaceflight.When the robot arm performs most of its tasks,its end will contact with the external environment.In order to ensure the best working effect of the robot arm,it is necessary to apply force control while the robot arm moves along the desired path.To this end,this paper proposes a nonlinear model predictive control strategy,while solving the path tracking and end contact force control of the robotic arm.The main research contents are as follows:A Nonlinear Model Predictive Control(NMPC)method is proposed based on Nonlinear dynamic and constrained conditions.In which the inverse kinematics solution of the robotic arm during online optimization is omitted,and the feedback linearization is used to implement the path tracking problem defined in the output space.The joint torque control of the manipulator is realized by adjusting the deviation between the end position and the reference position,and finally the path tracking control is realized.At the same time,in order to overcome the unmodeled dynamics and external disturbances in the manipulator system,a nonlinear disturbance observer is designed,and its input feedback compensation control input channel is used to suppress the impact of the disturbance on the system.Aiming at the problem of contact force control at the end of the robotic arm,this paper briefly describes the principle of impedance control,and applies NMPC to position-based impedance control(PBIC).It re-describes the optimization problem,and simultaneously solves the path tracking and contact force tracking problems through the NMPC controller.Through formula derivation and control system simulation,the effects of impedance parameters on force tracking and steady-state errors of impedance control are analyzed.Considering that it is impossible to obtain an accurate environment in practice,this paper proposes an adaptive control algorithm.This algorithm uses Lyapunov asymptotic stability theorem to achieve online adjustment of impedance parameters and achieve tracking of expected forces.