Encoderless Servo Drive With Adequately Designed IPMSM for Pulse-Voltage-Injection-Based Position Detection

This paper presents a technology fusion of encoderless control technique and encoderless-specialized motor applied for servo drive applications. First, a fast encoderless control technique which employs a high-frequency pulsating signal injection method with square-wave pulse voltage atd-axis is proposed. The estimation principle is almost the same as that of a resolver, and the control technique includes a fast initial position estimation algorithm based on magnetic hysteresis phenomenon. Next, a prototype interior permanent-magnet synchronous motor is designed to act like a resolver. Then, evaluation results of the prototype encoderless drive system are reported. Finally, the prototype system is confirmed to fulfill major servo specifications of about 10-b net resolution of the position detection at standstill and more than 60-Hz speed control bandwidth in operation speed from 0 up to 1000 min-1. In conclusion, the proposed encoderless drive system is verified to achieve major control performances almost comparable to those of encoder-assisted servo drive systems.