Sensorless angle estimation method for brushed dc motor using impedance variation by contact switching

A sensorless angle estimation method for brushed DC motor is proposed in this paper. In order to estimate the angle of the rotor without any mechanical sensors, the proposed method uses impedance variation by contact switching. In usual sensorless angle estimation methods, the angle of the rotor is estimated by the counter electromotive force (EMF). However, methods based on the counter EMF cannot estimate the angle accurately during standstill and at low speed. Furthermore, estimation errors occur due to the modeling error. In the proposed method, the angle of the rotor is estimated by using angle-dependent impedance. This paper focuses on the pulse variation due to contact switching. The impedance is measured by high-frequency signal injection and discrete Fourier transform. This method can be used to estimate the angle of the rotor directly. Therefore, it is possible to estimate the angle accurately at low speeds. The validity of the proposed method is verified through experiments. © 2017 The Institute of Electrical Engineers of Japan.