A New Cost-Effective Drive Control Technique to Improve Reference Trajectory Tracking for Gearless PMSM Driven Elevator System

In modern gearless Permanent Magnet Synchronous Motor (PMSM) driven elevator system, accurate reference trajectory tracking is one of the major performance metrics as it has direct impact on landing accuracy, travel time, energy consumption, traffic handling capacity and safety. However, due to the finite compliance of the suspension system connecting the traction motor to the elevator car, achieving zero tracking error at every instant of the travel is impossible. With conventional control, the accumulated tracking error is compensated at the end of the travel with the help of floor position sensors so that the landing accuracy and safety are not compromised. However, this technique increases the cost, energy consumption, travel time and decreases the traffic handling capacity. To overcome the above drawbacks, a new control scheme has been proposed that reduces the tracking error throughout the travel with no additional cost. In this scheme, to the output of the conventional speed controller, a current component is added which is generated based on virtually minimizing the rate of change of potential energy associated with the suspension system. This involves transforming the motor currents into the virtual rotating frame of reference. The proposed control scheme has been validated through simulations in MATLAB.