Sensorless speed/position control of brushed DC motor

This paper presents a new and novel technique for speed control of a brushed DC motor without employing any direct shaft transducer in its feedback mechanism. This method uses the current/voltage variation produced on the motor main input power lines as the brushes move from collector blade to the next. The frequency of variation is proportional to the motor speed and the rotor position can also be detected by monitoring the changes for each collector blade. The performance of the motor torque speed characteristic using this system as its feedback has been evaluated through laboratory testing. This configuration is very suitable for harsh environment and places with not enough space for the motor with discrete sensors.