Research On Current Loop Performance Of AC Servo System

With the development of modern control theory,motor manufacturing technology and the improvementof accuracy of encoder.Servo system has entered a new stage of development.Dynamic performance is the key index to measure the performance of AC servo system.It is of great significance to analyze the dynamic characteristics of the system.The space vector pulse width modulation(SVPWM)is widely used in AC servo control system,field programmable gate array(Field Programmable Gate Arrays)has the advantages of high adaptability,high integration,short development cycle,field upgrading advantages,and characterized by low power consumption,fast running speed.The absolute encoder can measure the rotor position of the permanent magnet synchronous motor accurately.Therefore,this paper uses FPGA as the main control chip,and the absolute encoder as feedback element to realizes the control of AC servo system by space vector PWM technology.This paper firstly describes the basic structure and working principle of permanent magnet synchronous motor(PMSM)and the mathematical model of PMSM in different coordinate systems.Based on the mathematical model in the d-q coordinate system,a more common id=0 vector control method is given.The basic principle and implementation process of space vector pulse width modulation(SVPWM)are expounded and analyzed.A scheme of measuring the position value of motor rotor using Heidenhain’s ECN1113 absolute encoder is designed,and the voltage and current are sampled by using Holzer components.The hardware platform of ac servo control system based on Altera company FPGA is set up,which includes FPGA minimum system,drive circuit,current sampling circuit,voltage sampling circuit,the rotor speed and position feedback circuit,and finally complete the welding work principle chart drawing,production and related components of the PCB panel.The software part introduces the design idea and process of main composing program.The design idea and process of the main modules are introduced.The program of the AC servo control system including main program module,PI program module,SVPWM program module,encoder data acquisition module and protection program module is written.Finally,we did experimentsand modificationson the experimental platform,realized the closed loop control of current loop,collected the related voltage and current waveforms,and studied the dynamic characteristics of the current loop of AC servo system through the data obtained from experiment.