Global speed control of separately excited DC motor

The global speed control problem over a very wide range operation for a separately excited DC motor is considered in the paper. The motor was firstly modeled in two local areas, the first model is a linear one when speed is under base speed, the other is nonlinear one when field weakening is used to obtain the speed well above base speed. Then a linear robust state feedback controller was designed for the linear model while an adaptive backstepping controller was designed for the nonlinear model. Uncertainties in armature and field resistances and load torque disturbance are considered. Then a global control methodology is utilized to combine the local controllers together to obtain smooth interpolation between the two local controllers. Finally, some simulations have been carried out to test the proposed controllers.