Research On Control Strategy Of PMSM Direct Drive Position Servo System

Direct drive servo system leaves out the deceleration transmission device between the driving motor and the load.This greatly improves the transmission efficiency and rigidity of the system.At the same time,the motor needs to endure a wide range of load torque change.This puts forward higher requirements on the performance of the motor and its controller.Permanent magnet synchronous motor(PMSM)has become the mainstream driving motor in the direct drive servo system with its characteristics like high power density?strong overload capacity.In this paper,we do research on the control strategy of PMSM according to the control requirements of the direct drive servo system.Firstly,this paper analyzes the transfer function model of direct drive servo system according to the classical control theory,and by the theory we get controllers' parameters.The result shows that the system gets a higher dynamic response performance and better stability with PI controller.Secondly,this paper studies the impact of the back-EMF on the current loop by using complex vector analysis and proposes dynamic decouple control strategies to improve the performance of the current control.Then the load torque identification is researched and a torque observer is designed based on the principle of Luenberger theory.On observer parameter selection,an optimization method is proposed.To improve the anti-disturbance performance of the system,the observed torque compensation is used.This paper also proposes a position compound control method to reduce the tracking error of the position ramp input signal.Finally,a simulation model of direct drive servo system is built in Matlab/Simulink software.At the same time,experimental platform is designed and built.The control performance results were compared between the optimal control strategy and PI control strategy.The simulation and experimental results all show that,under the optimal control strategy,the robustness of the current control becomes better,the anti-disturbance of system gets enhanced and the position servo tracking performance is also improved.These all verify the effectiveness and practicability of optimal control strategy.