Overshoot controlled servo system synthesis using bode plot and its application to PM brushless DC motor drive

Abstract

The design of current and speed controllers remains to a large extent a mystery to many engineers in the motor drives field. An attempt is made in this paper to simplify the design of the current and speed controllers using Bode plots. This paper outlines the theoretical background behind the techniques of symmetric optimum and dominant time constant compensation methods. The techniques are compared and contrasted using the overshoot and phase margin criteria. An application of these techniques to controller design for permanent magnet brushless DC motor (PMBDCM) drive system is made and verified with simulation. In order to apply these techniques to PMBDCM drive for the design of the current and speed controllers, the model of the motor drive is given for the benefit of the reader. The current and speed controller synthesis of a PMBDCM drive is achieved with the presented technique. Simulation results demonstrate for reference (current or speed) changes, symmetric optimum and dominant time compensation methods perform similarly. But for a load torque disturbance, the adverse effect on the speed is compensated faster only with the symmetric optimum method.