Sliding mode scheme for speed and current control of brushless DC (BLDC) motor

This paper proposes a sliding mode control scheme for effective speed tracking by obtaining ripple free torque through the inner loop current control for a BLDC motor. The second order mathematical model of the BLDC motor is developed for simulation purposes. Two first order sliding controllers based on the exponential reaching law algorithm are proposed for the inner loop current control and also for outer loop speed control of the drive. Performance of the speed tracking is then compared with a classical PI (Proportional and Integral) controller implemented for the speed loop, and the advantages of the proposed sliding mode scheme related with reduction of steady state error, settling time, percentage overshoot and disturbance rejection are summarized.