Research On Current Loop Bandwidth Influence Factors And Expansion Technologies For Galvanometer Servo System

Servo control system is the basis of motion control,affecting the overall performance of motion control system in the wide range of applications in robotics,advanced processing,aerospace and other fields.The domestic servo industry started late,and the technical level and accumulation are relatively insufficient.However,with the in-depth research in recent years,the performance of servo system is gradually improved,and there are many manufacturers and brands,which occupy more and more market share in China.Among all kinds of motor types,AC permanent magnet synchronous motor,which is deeply loved by electrical engineers,has become the mainstream because of its unique advantages.In the galvanometer scanning system,high-power laser processing products are still restricted by foreign countries.Most of the original schemes use the voice coil motor to realize the swing of the small lens.However,in the high-power laser system,because the ordinary lens which can not bear the high-power is replaced by the metal galvanometer with large inertia,the voice coil motor can not be applied,so the permanent magnet synchronous motor servo system is used to make the galvanometer operate at high frequency.This requires a higher bandwidth of the servo current loop.Therefore,this paper focuses on the reduction of various kinds of delay in the current loop,and studies and applies the integration into servo system from a variety of algorithms in the system current loop,the bandwidth extension is realized.Firstly,based on the vector control theory of permanent magnet synchronous motor(PMSM),the basic important algorithms are briefly discussed;according to the mathematical model of the system,the controlled objects’ models like motor are established based on the classical control theory,the theoretical analysis of influence factors of the current loop bandwidth and the verification of analysis correctness in MATLAB are implemented;the simulation model is built by Simulink,and the system performance under the basic PI control is analyzed.The correct model is used to face the following algorithm simulation tasks.Secondly,according to the existing problems of PI control algorithm,the current predictive control algorithm is studied and applied to reduce the calculation delay in the current loop and resolve the problems of PI controller.At the same time,the effectiveness of reducing the delay in the current loop is qualitatively analyzed.Moreover,most of the existing system adopts double sampling and double updating strategies.In order to further speed up the dynamic response of the current loop,the paper proposes the over-sampling strategy.The new strategy further shortens the delay time of PWM update.The simulation is carried out.Then,based on the above two algorithms,the corresponding dead time compensation algorithm is proposed,the principle is introduced in detail,and the compensation effect of the algorithm on reducing referenced voltage error is verified.Finally,the above methods are integrated and implemented on the simulation and hardware platform.According to different algorithms,the current and position are compared in the upper oscilloscope software.The current loop control algorithm is optimized and improved and the bandwidth is expanded,which can meet the working requirements of the aluminum Laser Galvanometer servo system.