DC motor speed control via buck-boost converter through a state dependent limited frequency switching rule

In this paper, a state dependent switching function with limited switching frequency is applied and experimentally validated in the context of speed control of a DC motor driven by a buck-boost power converter. The combination DC-motor/Buck-boost converter, very useful in practical applications, is modeled as a discrete-time switched affine system. The switching rule is based on the adoption of a general quadratic Lyapunov function whose time variation is bounded above by a concave-convex function with center determined by minimax theory and assures that the state trajectories converge to an invariant set of minimum volume containing the desired equilibrium. Experimental and simulated results are presented and discussed.