Joško Deur

Servo system with Vector-Controlled Permanent Magnet Synchronous Motor

Faculty of Electrical Engineering and Computing University of Zagreb, 1993

In the thesis the system structure of vector controlled permanent-magnet synchronous motor (PMSM) is developed. Speed and position controller design and microcomputer realization have also been carried out.

In the proposed control model, vector control principle is realized by feedback control of current vector components in rotor reference frame. The optimization of current vector in a steady state has been performed taking into account inverter current and voltage limits. The criterion of minimum current for given speed and torque is used as the optimal criterion. Two algorithms for current vector reference generation based on the optimized results have been developed and compared. The algorithms are different only in speed range above the base speed. The first algorithm is based on feedforward and the second on the feedback stator voltage control. The behavior of vector control system is examined by simulation characteristic operating modes.

The control features of two still often used permanent-magnet servo drives are described: interior permanent-magnet synchronous motor drive and brushless DC motor drive.

If PMSM is used only at speeds below the base speed, then the system structure of vector control becomes simplified and can be realized in analog technique. For such a drive, realized by using a laboratory model, the analysis of analog speed control loop and speed controller design have been carried out.

Digital speed and position control loops are realized by linking PC-XT computer with analog vector controller. Speed and position measuring values are reconstructed from incremental encoder signals.

Discrete speed controller design is made by using a bilinear transformation and symmetrical optimum criterion. Three anti reset windup algorithms are examined and compared in speed control mode.

Point-to-point position control has been considered. Nonlinear static position controller for digital speed control and limited output PI position controller for analog speed control are used. In the latter case the controller output is limited according to the nonlinear function of position error. The controllers in both cases are tuned so as to have time_suboptimal position response. Microcomputer implementation of controllers is quite simple.

Simulation programs are written in programming language C. In the case of control program, time-noncritical modules are written in C and time critical modules are written in assembler.

The behavior of speed and position control loops have been examined by simulation and experiment.