Weight-transducerless Starting Torque Compensation Of Gearless Permanent-magnet Traction Machine For Direct-drive Elevators

The direct-drive elevator system can transmit power to the application directlywithout the use of gears. It has many advantages such as energy saving, highefficiency, compact structure, low noise and vibration. The traction machine in thedirect-drive elevator system has better control precision, faster dynamic responses,and is able to provide high torque at low speeds by employing the permanentmagnet synchronous motor as the energy conversion component. As one of themajor concerns, improving riding comfort during direct-drive elevator start-up fromthe standby mode to the running mode is very significant. In order to achieve aquick balance of load torque during the electromagnetic brake releasing at theelevator starting, the load information from the weight transducer installed underthe elevator car is usually required for the drive to provide a matchedelectromagnetic torque with feed forward control. However, the installation of theweight transducer decreases the robustness when the feedback signal is affected bynoise and sometimes may not be able to provide the actual load information. As aresult, it might make the wrong torque compensation and cause uncomfortableriding feel. Therefore, eliminating the weight transducer and exploiting adaptivestarting torque compensation strategy is an emerging technique to improve thestarting reliability of the direct-drive elevator nowadays.In this thesis the dynamic model of the direct-drive elevator traction systemconsidering the rope elasticity, the brake releasing and the friction torque isestablished. Based on the dynamic model, the characteristics of the synthetic loadtorque exerted on the traction machine during elevator start-up are obtained. Inorder to balance the unknown load torque for the gearless elevator, a fuzzyself-tuning strategy is adopted to generate a suitable starting torque forcompensation by tuning the change rate of electromagnetic torque according to theencoder signal. The torque compensator is designed with the aim of getting aminimized sliding distance and avoiding traction sheave reversal.The weight-transducerless starting torque tracking strategy based on modelpredictive control is proposed. In order to improve the dynamic performances andwiden the bandwidth of the speed loop, the model predictive controller using thetraction machine mechanical motion model takes the place of the conventional PIcontroller. A load torque disturbance observer is introduced into the modelpredictive controller aiming to eliminate the velocity steady state error. Theproposed control algorithm with lower computation burden can achieve theweight-transducerless starting control of the direct-drive elevator with great riding comfort.Based on the simulation, the experimental results are provided to verify theeffectiveness of the proposed weight-transducerless starting torque compensationstrategies under different load. The Sin-Cos encoder is used as the rotor positionsensor. Both simulation and experimental results verify that the proposed adaptivestarting torque compensation strategies can achieve weight-transducerless start withsuperior riding comfort.