Closed loop performance of a permanent magnet brushless dc motor incorporating the nonlinearity in torque-balance equation (Transient operation)

This paper deals with the closed loop transient performance of a permanent magnet brushless dc motor drive system and the design of a controller to obtain minimum transient undershoot/overshoot coupled with negligible steady state error when it is subjected to a sequence of load torque disturbances. In view of the complicated modeling including nonlinearities of the problem, the transient solution can be obtained by computer simulation only, where the design of the controller is carried out in an iterative manner. Accordingly, a performance index based on the principle of integral-mean-squared-error is formulated. A series of simulation runs for minimizing the performance index were carried out for different combinations of gain parameters. Mathematically, this criterion not only minimizes overshoot/undershoot, but also reduces the settling time. Using this optimized controller design; the transient performance of the motor and the drive system is obtained. 3-D graphs of the performance index and settling time in the controller parameter space corresponding to various settings are also presented.