Current Sensorless Speed Servo System of PM Motor Based on Current Estimation Method

Abstract

This paper proposes a new speed servo system of PM motor without current sensor, which is constructed by the current simulator of PM motor. The proposed speed servo system is simple and economical. The sensor of the proposed system is only a position sensor such as an encoder. Hence, the proposed speed servo system has little influence of the switching noise of PWM inverter. Moreover, the resolution of proposed current simulator can be higher than of the conventional actual current feedback system.
In this paper, the experimental results point out that the proposed current sensorless speed servo system has the desired current and speed response. The current waveform of the proposed system is smooth and clean. Moreover, this paper proposes a new identification algorithm of motor resistance R_a and main flux Φ_fa by using only position sensor.