Sensorless speed estimation of permanent magnet DC brushed motor considering the effect of armature teeth-slots and commutation

This study proposes a novel technique of speed estimation for permanent magnet direct current (PMDC) brushed motor. The impact of armature teeth-slots and commutation of PMDC motor on armature current is considered in this study to estimate the speed. In many applications, speed measurement of motors is essentially required. Conventionally mechanical sensors are coupled to the motor shaft for speed measurement. Recently many sensorless methods for speed estimation of motor had been introduced. This study proposes a new method where the variation in effective magnetic path reluctance due to continuous alternation in teeth-slots positions with respect to stationery poles is considered. Combined effects of effective magnetic path reluctance variation and armature commutation cause ripple in armature current. In this study, the effect of teeth-slots in armature current is investigated using finite-element approach and also it is verified experimentally. Furthermore, an elementary circuitry is included in this study in support of the proposed method from armature current. The performed test on a 24V-100W brushed PMDC motor indicates that the proposed method is effective in wide range of speed estimation considering the effect of change in mechanical load or terminal voltage level.