Quasi bang-bang and sliding-mode controls for a DC shunt motor

We propose a hybrid fuzzy-linear controller for a nonlinear terminal voltage-controlled DC motor. The nonlinearity includes the effect of magnetization saturation and a nonlinear fan load. The input to the proposed fuzzy logic controller (FLC) is an "aggregate" error between the required and the actual RPM and its time derivatives. The FLC is designed to approximate a bang-bang controller and its coefficients are chosen a trade-off between short rise time, small steady-state errors and control chattering. The FLC performance was compared to that of a well known design, namely a sliding mode controller with a boundary layer. Although the FLC design procedure is easier, the performance of the two controllers are quite similar.