High-order Sliding Mode Control For Trajectory Tracking Of Robotic Manipulators

In recent decades,the robot industry has developed rapidly all over the world and its application covers all fields of people's production and life.Industrial robotic manipulators have attracted great attention on the control problem in the automation engineering.Based on uncertain nonlinear robotic manipulator system,this thesis addresses the control problem about trajectory tracking of robotic manipulators by adopting high-order sliding mode control,adaptive technique,extended state observer and Lyapunov stability theory.The main contents are concluded as follows:(1)An adaptive second-order fast nonsingular terminal sliding mode controller is presented for trajectory tracking of robotic manipulators in the presence of external disturbances and system perturbations.Firstly,to achieve fast convergence,strong robustness and desirable tracking precision,a second-order fast nonsingular terminal sliding mode surface is designed to guarantee system performance and stability.Besides,chattering is eliminated using continuous control law due to high-frequency switching terms contained in the first derivative of actual control signals.Meanwhile,uncertainties are compensated by introducing the adaptive technique,whose prior knowledge about upper bound is not required.Finally,simulation results validate the effectiveness of the proposed control scheme.(2)An adaptive super-twisting global integral terminal sliding mode controller is designed for trajectory tracking of n-DOF rigid robotic manipulators in the presence of system perturbations,external disturbances and nonlinear frictions.Firstly,the global integral terminal sliding mode surface is proposed to realize the robustness against matched disturbances throughout the control process,which can eliminate the reaching phase and ensure the existence of sliding mode around the surface right from the initial time.In addition,based on the super-twisting algorithm,adaptive technique is applied to estimate the upper bound of matched uncertainties.Moreover,according to the Lyapunov stability theory,it can be proved that the sliding mode surface can be established in finite time,and then the tracking errors will converge to zero on the sliding surface.Finally,simulation results verify the validity of the designed control method.(3)Based on super-twisting extended state observer and output feedback high-order sliding mode observer respectively,the adaptive global integral fast terminal sliding mode controller is constructed for trajectory tracking of rigid robotic manipulators in the presence of system perturbations,external disturbances and damping frictions.Firstly,the global integral fast terminal sliding mode surface is designed to eliminate the reaching phase such that global strong robustness against matched uncertainties can be guaranteed throughout the control process.The avoidance of chattering and the reduction of energy consumption can be realized by the adaptive super-twisting algorithm.Furthermore,the unknown uncertainties can be estimated by super-twisting extended state observer and the control law is designed to compensate them by the observations.Practically,it is difficult to accurately measure the angular velocity of each joint.Therefore,the output feedback high-order sliding mode observer is presented to estimate the angular velocity as well as unknown disturbance only with the measurement information of the angle of each joint.Then the observations are used to redesign sliding mode manifold and control law.With the help of the Lyapunov stability theory,the finite-time convergence of observation errors,the finite-time establishment of sliding mode surface and the asymptotic convergence of tracking errors can be proved.Finally,simulation results validate the effectiveness of the proposed control strategies.