Research On Low Speed Control Of AC Servo Systems Based On EKF

High performance PMSM servo systems have a wide application in the region of industrial automation, numerical control and robot. Servo systems are further researched and developed by many scientific research institutions. A servo drive device based on DSP and IPM is designed in this thesis. Much debugging and experimentation on the system have been done. Theoretical study and simulation are carried out on improving the performance in the low speed region.Firstly, according to the detailed analysis on the mathematical model of PMSM, the principle of Field Oriented Control(FOC) is illustrated. SPWM and SVPWM are analyzed and contrasted in detail too, and the digital realization techniques based on DSP are given. Then the hardware frame of the servo driver is introduced, especially the design of the DSP minimal system, current detecting circuit, speed and position-acquiring circuit, power circuit based on IPM are further researched. The software frame of the servo system is introduced and the flow chart is given. Many experiments have been done on improving the speed and current response performance. The experimental result has shown that high speed performance is satisfactory while speed performance is poor in the low region. Ripple of speed is serious in low speed.Low speed control performance has much more influence on the precision of servo systems. To improve the speed response in low speed region is very useful to servo systems. So Extend Kalman Filter (EKF) is applied to low speed control of AC servo systems in order to identify the information of position of magnet poles and low speed instead of incremental encoder. In high speed region, encoder is still used to acquire speed information. The simulation of AC servo system with EKF has been carried out under MATLAB. The result has shown that detecting low speed with EKF has good static and dynamic performance. Especially in low speed, this method has good motor position tracking performance and speed tracking performance. So with this method, the static and dynamic performance can be guaranteed in the whole speed range.