Load Sensorless Novel Control Scheme for Minimizing the Starting Jerk and Energy of the PMSM Driven Gearless Elevators With Varying Stiction and Rotor Flux Linkage

PMSM has started replacing induction motor in electric elevator systems, thanks to its' high efficiency and high torque/power density. One of the challenges in elevator systems is to maintain the comfort of the passengers with optimal energy consumption. One such instance where it is quite intricate to achieve both is during the starting of the elevator due to nonlinear variation of friction with speed. Accurate friction compensation without employing weight transducer is vital to reduce the cost, starting jerk and energy consumption. However, due to the high dynamic response of PMSM and limited bandwidth of the elevator speed controller, conventional starting jerk control schemes lead to increase in starting jerk resulting in increased starting energy if stiction (static friction) or rotor flux linkage or both vary from their predetermined values. Further, due to low mechanical resonance frequency of the elevator systems, classical disturbance observers (DOB) cannot have high bandwidth which hampers their disturbance rejection capability. Higher order and non-linear DOBs/controllers are quite complex to design due to the unpredictable dynamics of friction and intricacies of estimating rotor flux linkage at very low speeds. To alleviate these issues, a novel disturbance observer is proposed in this paper, which momentarily controls the speed of the stator flux linkage instead of torque/current during starting. The control scheme is substantiated by MATLAB/SIMULINK simulation results.