Study On The Self-tuning Strategy Of Control Parameters For PMSM Servo System:A Frequency Domain Approach

The performance of permanent magnet synchronous motor(PMSM) system is determined by the control parameters. The servo system self-tuning technique is able to set the control parameters automatically. In order to improve the performance of servo system, it is of great significance to study the servo system self-tuning technique.Based on the frequency domain analysis, speed loop of PMSM servo system is chosen to illustrate the approach of tuning Proportional-Integral(PI) controller parameters.To identify the frequency response of controlled system, an investigation is undertaken to study the components of servo system. Based on the investigation, the controlled system which needs to be estimated is pointed out. The algorithm based on discrete fourier transform(DFT) is employed to identify the frequency response of controlled system by measuring the amplitude and phase of stimulus and response. In order to eliminate the influence of spectrum leakage, which can improve the result of frequency response estimation, the method of determining the frequency of stimulus and the sampling points is proposed.To evaluate the characteristic of system, four frequency domain evaluation indexes are specified, including cutoff frequency, phase margin, modified gain margin and close-loop resonant index. The system stability constraint is proposed taking concerned of the indexes above.The explicit relationship between PI controller gain and open-loop cutoff frequency as well as phase margin is proposed. The control parameter table optimization method is put forward based on the system stability constraint and integral gain maximization principle.Simulation and actual experiment platform are constructed. Several experiments are carried out including frequency response estimation test and step test. As a result, the proposed servo system control parameter self-tuning strategy is verified.