Novel Rotor Position Estimation Technique For Switched Reluctance Motor Using Vibration Signature Analysis

In this paper, we present a novel technique to estimate the position of the rotor of a switched reluctance motor by observing the characteristics of the vibration of the stator during the motor operation. This removes the need of the shaft position sensor which is known for its unreliability and problems associated with its application. Vibration in switched reluctance motors is generated mainly due to stator deformation as a result of radial forces caused by the magnetic flux. The magnetic flux density varies significantly with the rotor position depending upon the alignment of the poles of the rotor and the stator. Thus, at different rotor positions, the vibration amplitude recorded at a particular point on the stator lamination varies. This makes it possible to correlate rotor position with the stator vibration pulses. We have carried out simulations on a 6/4 SR motor to demonstrate this position estimation technique. Initially, we generate vibration pulses separately in the simulation with respect to the flux density keeping the point above a particular stator pole as the frame of reference. This is done to closely approximate and simulate the data recorded by an accelerometer imagined to be installed at that point. We have used the characteristics determined and the analysis made on the vibration of SR motors by previous research experiments to generate the vibration pulses with respect to the flux. We then estimate the rotor position by detecting the regular spikes in vibration and then compare it with the actual position of the rotor. We find that although the resolution of the rotor position measurement using our technique is not very high at low speeds, this method is highly efficient at high rotor speeds and it requires less computational power thereby saving costs. We analyze our technique in detail and outline its several key advantages when compared to other position estimation schemes for SR motors.