Quantized-Input Control Lyapunov Approach for Permanent Magnet Synchronous Motor Drives

We present a new method for the generation of input switching sequences in a synchronous motor control system based on the evaluation of a control Lyapunov function over a discrete set of realizable inputs. Typical reference input realization methods, such as space vector modulation, rely on high-frequency state space averaging which can yield unnecessary switching events and increased switching losses. Alternative input selection strategies, such as lookup-table-based direct torque control, rely on heuristically chosen hysteresis bands to determine switching instants, which often results in a suboptimal choice between switching frequency and other performance measures. In this paper, we use an energy-related Lyapunov function to guide the input selection process by making switching decisions based on the stabilizing effect each input has on the closed-loop system. We provide a theoretical analysis of a motor-inverter system, leading to a stability proof for a quantized input control law. The controller performance is verified through computer simulations and experimental results.