Research On Position Tracking Control Of Servo System Based On Sliding Mode Method

The permanent magnet synchronous motor(PMSM)servo system has become an integral part of modern industrial production.However,as a multi-variable strongly coupled nonlinear system,its parameters are often perturbed due to changes in the environment during operation.Besides,the uncertainty of the load torque and the non-modeling characteristics of the motor will affect the stable operation of the motor.Therefore,it is of great significance to study the robust algorithm of the motor servo system in the presence of the above interference.In this paper,the tracking control of the speed and position of PMSM servo system is realized based on the sliding mode method and the disturbance observer.The disturbance observer is used to estimate the lumped disturbance of the system online and compensate it to the sliding mode controller in real time to improve the robustness of the system.It is verified by digital simulation and the experiment of dSPACE motor platform.(1)The development status of the motor servo system and the research status of motor control strategies at home and abroad are systematically explained,and the challenges and countermeasures in the field of motor control are analyzed.The transformation relationship of PMSM servo system mathematical model in various coordinate systems is introduced,and the principle of motor vector control and SVPWM modulation strategy are introduced.(2)Aiming at the problem of parameter deviation and load torque uncertainty in the speed tracking of PMSM servo system,a PMSM terminal sliding mode control method based on reaching law is proposed.First,considering the uncertainty of the motor parameters and load torque as lumped disturbances,an adaptive extended sliding mode disturbance observer is designed to estimate the disturbances.Secondly,the sliding mode disturbance observer compensates the disturbances to the controller.At the same time,an online identification method based on the viscous friction coefficient and the moment of inertia of the disturbance observer is adopted to reduce the influence of parameter uncertainty on the control system.Finally,the effectiveness of this method is verified by simulation and experiments.(3)Aiming at the external disturbance problem in position tracking control of PMSM servo system,a new hybrid second-order sliding mode control strategy was proposed.First,considering the uncertainty of the motor parameters and load torque as lumped disturbances,an adaptive extended sliding mode disturbance observer is designed to estimate the disturbances.Secondly,a new terminal sliding mode function is proposed,and a super-twisting controller based on an adaptive extended sliding mode disturbance observer is designed,in which a second-order super-twisting nonlinear switching term is introduced to weaken the system jitter.Then,the convergence of the terminal sliding mode surface and the stability of the controller are proved mathematically.Finally,experimental verification shows that the method has faster response time and stronger anti-interference ability than the traditional sliding mode method.(4)Aiming at the problem of load uncertainty and parameter drift of PMSM servo system,a novel fractional sliding mode control strategy is proposed.Specifically,first,the motor parameter drift,the additional unknown disturbances,and the uncertainty of the load torque are considered as lumped disturbances,and a nonlinear disturbance observer is designed to estimate the lumped disturbances.Secondly,fractional order terminal sliding mode surfaces are designed for the current loop and position-speed loop respectively,and fractional-order sliding mode controllers are designed based on the nonlinear disturbance observer,respectively,where a second-order super-twisting term is introduced into the position-speed loop fractional-order sliding mode controller to reduce system jitter.In addition,the stability of the fractional-order sliding mode control strategy is analyzed mathematically.Finally,experimental verification shows that the method has faster response time and stronger anti-interference ability than the traditional sliding mode method.