A rapid and high-accuracy control scheme of starting torque for elevators without a weight transducer

In order to reduce the cost of the elevator traction system and to provide a comfortable riding experience for the passengers, a rapid and high-accuracy control scheme of starting torque for elevators without a weight transducer is proposed in this paper. A main problem on how to provide an electromagnetic torque to balance the load torque is considered as the one how to maintain a zero velocity during brake releases. Firstly, we propose an approach to obtain a high-accuracy speed measurement from a quadrature encoder. Then as a feedforward compensation, an estimated load torque based on a reduced-order observer is introduced to improve the dynamic performance of the motor. The impact of different moment of inertia used in the observer and in the real system has been analyzed as well. Moreover, an adjusting method of the PI controller is established to suppress the speed overshot. Finally, results of experiments on a permanent magnet synchronous motor are provided to illustrate the validity and improvement of the scheme.