Adaptive Variable Structure Control Of Manipulator System Based On Improved Reaching La

With the vigorous development of robot control technology,the manipulator has been further applied to medical,aerospace,defense and other fields in traditional industrial manufacturing.As a complex nonlinear system,in order to cope with different control tasks in the control process of the manipulator,the requirements of the system trajectory tracking control performance are also getting more and more.Moreover,considering the control accuracy of the actuator,system modeling error,dead zone nonlinearity,unknown external disturbance and other complex working conditions,the positioning accuracy,response speed and trajectory accuracy of the manipulator system will be affected,and even lead to various errors when the manipulator performs the preset trajectory action.Sliding mode variable structure control is a widely used typical nonlinear control method.It has the advantages of simple design method,fast response speed and strong robustness.It is regarded as one of the effective and reliable control methods for manipulator system.However,although some achievements have been made so far to apply the sliding mode strategy to the theoretical research and practical application of the tracking control of the manipulator system,there are still many problems to be further studied in the finite time convergence of the system state,chattering suppression and control accuracy improvement.Based on the previous research results,this paper studies the trajectory tracking control of the manipulator system based on the modified reaching law method.The specific research contents are as follows:1.A modified reaching law scheme is proposed for a class of manipulator systems with parameter uncertainties and unknown disturbances.Combined with disturbance observer technology,a new adaptive sliding mode controller design algorithm is given.Firstly,the modeling uncertainty and external unknown disturbance of the system are estimated based on the disturbance observer,and then the control input torque signal is compensated.Secondly,the modified reaching law scheme is adopted,which can not only realize the dynamic adjustment of the gain of the sliding mode robust term,but also make the designed adaptive sliding mode controller ensure that the error tracking signal of the closed-loop system reaches the sliding mode surface in finite time,and effectively suppress the chattering of the system.Then,the asymptotic convergence of the error tracking signal of the closed-loop system is proved by Lyapunov stability theory.Finally,the effectiveness of the proposed control strategy is verified by simulation experiments and data analysis.2.Aiming at the manipulator system with modeling error,external disturbance and actuator dead zone,in order to realize the high efficiency and high precision tracking control of the desired trajectory,a novel adaptive terminal sliding mode controller design scheme based on finite time disturbance observer is proposed.Firstly,the finite time disturbance observer technology is used to estimate the lumped disturbances such as the actuator dead zone,external unknown disturbance and modeling parameter uncertainty of the system,and then the controller design is effectively compensated.Secondly,based on a modified variable gain reaching law,a new nonsingular fast adaptive terminal sliding mode controller design algorithm is proposed,which not only avoids the singularity problem in traditional terminal sliding mode control,but also realizes the system state to reach the pre-designed sliding mode surface quickly,and further weakens the chattering of the system.The finite time convergence of the closed-loop system error tracking signal is analyzed by combining the finite-time stability theory and Lyapunov function method.Finally,the simulation results verify the feasibility and effectiveness of the designed control scheme.3.For the manipulator system with external disturbances and modeling errors,a new adaptive global sliding mode controller design scheme is proposed to further improve the robustness and dynamic performance of the closed-loop control system.Firstly,an improved global sliding surface design scheme is introduced to ensure the global robustness of the system,and the problem that the sliding surface of the traditional global sliding mode control cannot evolve into a linear sliding surface in finite time is solved.Secondly,based on the proposed modified reaching law method and the disturbance observer technique,a new global adaptive sliding mode controller design algorithm is proposed.Furthermore,the asymptotic convergence of the closed-loop system error tracking signal is proved by Lyapunov stability theory.Finally,the simulation results verify the effectiveness of the designed control method.