Novel Active Damping Scheme to Enhance the Performance of PMSM Driven Gearless Elevators by Minimizing their Vertical Vibrations

The direct driven (without gearbox) Permanent Magnet Synchronous Motor (PMSM) traction elevators are becoming more popular in low rise and medium rise buildings compared to geared induction motor driven elevators as the former has higher efficiency and power density. In order to achieve high landing accuracy and optimum ride comfort in such systems, there is a need for comparatively higher bandwidth speed controllers. However, such a controller might induce vertical vibrations in the elevator car due to rope compliance. Active damping of oscillations is an effective approach to mitigate this issue. But, the conventional active damping schemes available for elevators either demand the need for additional hardware or they involve complex estimation/signal processing algorithms. In order to alleviate these drawbacks, a novel active damping scheme is proposed in this paper, in which the damping coefficient has been made adaptive by augmenting a suitable pole zero pair with the conventional active damping scheme available for low torque/short shaft servo drives. The pole/ zero location is selected judiciously with due consideration to the dynamics of the current controller. The proposed control scheme has been validated through simulations for a 2:1 roping based PMSM driven gearless elevator system.