Effects and Detection of Misaligned Position Sensor in AC Servo Drive System with Filtered Current Delay

In AC servo drives, the rotor position and measured stator currents of permanent magnet synchronous motor (PMSM) are required as feedbacks of drive system. The rotor position of PMSM is very important variable to be known correctly to obtain the optimal torque per ampere from the motor. Unfortunately, manufacturerspsila position sensor datasheets may not include the angular relationship between the back emfs of motor and angle measured by sensors. As a result, implementing the incorrect rotor position, the produced torque is not optimal, resulting in lower efficiency, lower starting torque, and degraded performance. Another issue is related to measured currents through commonly used passive low-pass filters. These filters would also introduce both reduced magnitude and phase delay in the measured currents, affecting the torque production as well. This paper illustrates the effects of misaligned position sensor and phase delay of filtered currents to the overall drive system. A practical technique of detecting the angle misaligned by the position sensor installation is presented. In this paper, both simulation and experimental results will demonstrate the effects of incorrect rotor position and filtered current delay to the torque production. The overall drive algorithms are implemented on a 32-bit fixed-point digital signal processor TMS320F2808 based controller.