Speed control of converter fed DC machine using nonlinear state-space model

The control problem of a nonlinear second-order system is considered. A transcendental nonlinearity is considered to be present while modeling a DC drive system fed by a three-phase AC-to-DC converter. The modeling of the DC machine along with the converter system is done in state space. The field excitation of the DC machine, however, is considered to be constant. The investigation considers both open- and closed-loop performance. The control problem is formulated as how the firing angle of the converter can regulate the speed when there is a step change in load torque. In view of this, two aspects of regulation, proportional and proportional plus integral, are investigated. The nonlinearity of the converter-fed DC machine system is simulated on a digital computer using a predictor-corrector method. In the present work, the formulated control law is very unusual and nonlinear