Hybrid step motor position estimation from back EMF

Hybrid stepping motors exhibit a back EMF voltage from which absolute position measurements may be extracted. This work analyses a novel technique for extracting these position measurements for constant velocity applications. The method produces accurate measurements (/spl plusmn/0.1 mechanical degrees). To increase the utility of these measurements, Kalman filtering techniques have been employed. To reject unmodeled disturbance step functions, the nonlinear dynamics have been exploited. The resulting control law is able to use Kalman filtering to improve the bandwidth while retaining disturbance step rejection.