Sensorless speed control of brushed DC machine

The automotive industry is ramping in volume. New models of battery-powered vehicles are introducing to the mass market customer on a monthly based. Upcoming automobiles are using more than 60 rotating electric machines. The dominant part of this amount consists of brushed DC motors dedicated to the car body segment. Cost reduction and simple control are the main reasons why manufacturers prefer using DC machines in applications like window lift, seat positioning, or sunroof control. In addition, safety in the automotive segment pushes control strategies of DC machines toward sensorless operation. In this article, the current ripple caused by commutation is used for accurate sensorless speed control. The new method is analyzed and compared with the traditional encoder-based speed control cascade structure. The real-time control system was developed at dSPACE 1103 and tested using an automotive-qualified H-bridge.