Disturbance control of the hydraulic brake in a wind turbine

This paper discusses control of the brake torque from the mechanical disc brake in a wind turbine. Brake torque is determined by friction coefficient and clamp force; the latter is the main focus of this paper. Most mechanical disc brakes are actuated by hydraulics, which means that controlling caliper pressure is the key to controlling clamp force. A pressure controller is implemented on a laboratory-sized test system and uses a disturbance estimator to reject disturbances in order to track a reference curve. The estimator is capable of estimating both input equivalent disturbances and disturbances caused by brake disc irregularities. The controller can reject input equivalent disturbances and a strategy for cancelling the disturbance from the brake disc is proposed.