Sliding mode speed controller for trapezoidal brushless motors

ABSTRACT This paper describes the application of a variable structure speed controller for a non sinusoidal brushless permanent magnets motor drive. Our trapezoidal brushless motor model changes the working conditions for every phase commutation and moreover it allows to simulate the different structural motor configurations. Controller synthesis is carried out using sliding mode theory with a pole assignment technique. During the sliding motion the state point is forced to reach a prescribed surface due to an active change of the control action. The order of the system is therefore reduced and moreover the dynamic behaviour of the closed-loop system is imposed. Results by digital computer simulation prove parametric variation insensitivity, disturbance rejection, fast transient responses, no overshoot and absence of speed ripples during phase commutations.