Effect of the Method of Control on the Transfer Function Parameters of a Two-Phase Servomotor

In this paper, the effect of the method of control on the transfer function of two-phase servomotors is investigated. The methods of control considered are the amplitude, time-phase, frequency, voltage-frequency, pulse-width and space-phase control. Torque equations are derived for different methods. The motor gain and time-constant are determined from the torque-speed and speed-signal characteristics. The servomotor torque, speed, time-constant and gain — and their dependence on the signal magnitude — are compared for the different methods of control. It is shown that for the same value of the signal, the motor time-constant may vary between 2·2 msec and 45 msec and the gain may be increased six times if the method of control is changed.