Weight-transducerless starting torque compensation of gearless permanent-magnet traction machine for direct-drive elevators

To improve the starting performance of a permanent-magnet traction machine without a weight transducer in a gearless elevator, an adaptive starting torque compensation strategy is proposed in this paper. The dynamic model of the direct-drive elevator traction system considering the rope elasticity, the brake releasing, and the friction torque is established. Based on the dynamic model, the characteristics of the synthetic load torque exerted on the traction machine during elevator start-up are obtained. In order to balance the unknown load torque for the gearless elevator, a fuzzy self-tuning strategy is adopted to generate a suitable starting torque for compensation by tuning the change rate of electromagnetic torque according to the encoder signal. The torque compensator is designed with the aim of getting a minimized sliding distance and avoiding traction sheave reversal. Both simulation and experimental results are provided to verify that the proposed weight-transducerless adaptive starting torque compensation strategy can achieve superior riding comfort of shorter sliding distance, faster dynamic response, and smaller sliding speed.