Some approaches on instantaneous angular speed measurement using a two-phase n poles AC generator as sensor

Abstract

The paper proposes an instantaneous angular speed (IAS) measurement method, based on computer-aided processing of two instantaneous induced electromotive force (EMF) signals (in phase quadrature) delivered by a two-phase n poles AC rotary generator used as sensor, which works also as a n poles sine and cosine waves rotary encoder. In this approach, firstly, an optional number of m virtual EMF signals are generated by computing the two real EMF signals. Afterwards, a high sampling rate and high accuracy IAS measurement method is proposed using the elapsed time between zero-crossing moments of each two consecutive virtual EMF signals. On the same generator, a known IAS measurement method (slightly adapted) is used also for comparison purposes. In this method, the two real EMF signals define by calculus a rotation angle whose numerical differentiation produces the IAS value. Both IAS measurement methods validate well each other through frequency domain signal processing and analysis, from 0 to 7000 Hz. Some experiments, achieved on a lathe headstock output spindle, confirm the availability of the proposed IAS measurement method for monitoring and diagnosis.