Research On Control Strategy Of Permanent Magnet Synchronous Motor Servo System

Servo systems are used more widely, such as in industrial controllers and household appliances. Performance, function and price of servo products are being concerned more and more. Digital controlled AC servo systems will be the trend, which uses Permanent Magnet Synchronous Motors (PMSM) as power units and high quality control strategy, based on DSP.First of all, mathematical model of PMSM is presented after studying physical equations and equivalent circuits. PU model of PMSM is also given for digital control of motor.Field Oriented Control (FOC) and Direct Torque Control (DTC) are the two classical projects for AC drive systems. To catch the difference of system performance between FOC and DTC of PMSM servo system, both principles are analyzed and their characteristics are presented. The simulating models of these two schemes are built, and experiments are carried out. The results of simulation and experiments show: DTC has better torque dynamic performance than FOC, because current PI adjustor is eliminated. But, only one space voltage vector applied in each sampling period in PMSM DTC servo system results in large ripples of torque and stator flux linkage.To take full advantages of DTC and FOC, a novel direct torque control of PMSM based on observing error of stator flux linkage is proposed. It can realize continuous voltage vector modulation and decrease the torque ripple. This scheme is validated by simulating and experimental results of PMSM DTC-SVM servo system.AC servo system is a nonlinear and coupling system. So Fuzzy logic control (FLC) is introduced. A simple and effective position controller is designed, and also realized, whose PI parameters can be adapted by FLC. Experimental results show its validity in PMSM servo system.Finally, a DSP-based PMSM servo control system is proposed. The control system's hardware and software are designed and tested.