Research On Elevator Weight Compensation Method Without Weight Sensor Based On Permanent Magnet Synchronous Motor

Nowadays elevator market comes to a fiercely competitive occupation, so more attention is paid to promote products’ comfort and to enhance the cost-effective. Elevators’ performance is asked to reach a higher requirement in these areas. In order to improve the starting performance of elevators, weight sensors are installed in the lift car what can make motor running smoothly and provide scheduling information. However, the weight sensor does not only increase the cost of purchasing and installing of the elevator, but also requires routine maintenance and adjustment to ensure its performance, which cause the increasing of the elevator’s operating costs, and reduce the reliability of the system. On the other hand, permanent magnet synchronous motors are widely used in elevator traction. Because of the characteristics of the PMSM that the output torque can be reflected directly in the cross-axis current, the elevator can be directly informed by the forces of change in the measured current. According to this performance the weight of the lift can be indirectly measured by the starting current.In this paper a new elevator weight compensation method without weight sensor is proposed which depends on the characteristics of permanent magnet synchronous motor. This method identifies the acceleration and the changing current to adjust the staring current instead of measuring weight by the quality sensors. In this way the elevator maintaining the smooth operation while reducing the purchase and operation cost.Considering the motion characteristics of the lift, a mechanical model which describes the starting of elevator is suggested. According to the characteristics of permanent magnet synchronous motor the relation between ideal compensation force and cross-axis current is established. All of those steps guidance the design of the weight compensation algorithm. Simulation and experimental results show that load change causes significant changing in acceleration during the starting of the facility. And the compensation method can effectively identify the weight of the elevator and suppress the fluctuation of the acceleration. Therefore the results of no sensor system operating during the starting and braking are close to the effects of the system which installs weight sensor.