Robust Performance Improvement Method Of Deadbeat Predictive Current Control For AC Servo System

PMSM has been widely used as the actuator of AC servo system due to its high power density,high dynamic response and wide speed range.With the rapid development of industrial robots,radar tracking,aerospace and other high-tech fields,the performance requirements of servo drive systems are getting higher and higher,which leads that the research of AC servo systems with high precision,high reliability and high dynamic response has become very important.In the AC motor servo drive systems,the current loop is the innermost loop of the three-loop control in drive system,whose dynamic and steady-state performance directly determines the electromagnetic torque output by the motor.However,the conventional current loop linear control strategy is difficult to meet the high performance requirements of the AC servo in industrial occasions.Therefore,predictive current control algorithm with high dynamic performance has become a research hotspot in recent years.Although predictive current control of PMSM has a good dynamic response,the control precision depends heavily on the accuracy of the object model.When there is a mismatch between the model parameters and the actual system,the current loop will appear a tracking error or even lead to system instability.Firstly,in this paper,a PMSM servo system based on the principle of rotor field orientation is introduced.And a deadbeat predictive current control(DPCC)algorithm for PMSM is subsequently constructed based on the mathematical models of PMSM under coordinate systems and parameter sensitivity of the DPCC algorithm are analyzed.Secondly,Aiming at the steady-state current error and stability problems caused by model parameters and other unmodeled dynamics in conventional DPCC of PMSM,a sliding model current disturbance observer(SMCDO)based on exponential-based bi-power reaching law is researched,which is able to simultaneously observe and compensate the disturbance in the predictive current control system in real time.Meanwhile,the prediction of stator current also can compensate digital control delay.Finally,the stability and convergence of SMCDO are theoretically analyzed,and the hardware structure and main algorithm implementation process of predictive current control system of PMSM based on SMCDO are briefly introduced.Using Matlab/Simulink simulation software and DSP+FPGA as the hardware experiment platform of control chip,the DPCC of PMSM based on sliding mode current disturbance observer is simulated and experimentally researched respectively.The simulation and experimental results show that the method can effectively improve the robust performance of conventional DPCC of servo system.