Using mechanical vibration to estimate rotor speed in induction motor drives

Motor speed information is important for high-performance induction motor drives. Various sensorless control methods have been proposed in the last two decades to eliminate the cost for conventional speed sensors. In this paper, a new method of determining motor speed using torque-ripple-induced vibration with a relatively low-cost piezoelectric material vibration sensor is introduced. The piezoelectric speed sensor has the advantage of low cost, small size and relatively straightforward implementation. In addition, the proposed method is independent of machine parameters. Digital signal processing methods are applied to obtain the motor speed information from vibration signals. Experimental results validate the effectiveness and accuracy of the proposed method.