Improving Instantaneous Angular Speed Monitoring by Means of Sinusoidal EMF Signals Delivered by a Two-Phase n Poles AC Generator Used as a Sensor

This paper introduces a new approach in instantaneous angular speed monitoring using a two-phase n poles AC generator as sensor. A two-phase n poles (n=50) stepper motor plays the role of sensor. Its rotor is firmly connected to the rotary part whose instantaneous angular speed should be measured. The sensor produces two identical sinusoidal EMF (electromotive force) signals (theoretically shifted with π/2 radians) with the same periods T. This paper proposes to use the mathematical product of the numerical descriptions of these EMF signals in order to define a new EMF signal with a period T/2 whose analysis allows the determination of 4·n=200 samples of instantaneous angular velocity on each full rotation. Each period of this new EMF signal (with an overlap of a semi period) is involved in the description of the instantaneous angular speed. In this way, the sensor is virtually converted in a single-phase 2·n poles (2·n=100) AC generator. The experimental results confirm the validity of this approach.