Linear grade encoder for high resolution angle control of SRM drive

In SRM drives, the ON-OFF angles of each phase switch should be accurately controlled in order to control the torque and the speed stably. The accuracy of switching angles is dependent upon the resolution of the encoder and the sampling period of the microprocessor, that are used to provide the information of rotor position and to control the SRM power circuit, respectively. However, as the speed increases, the amount of switching angle deviation from the preset values is also increased. In this paper, a new low-price linear grade encoder, suitable for the practical and stable SRM drives, is proposed. And also, a control algorithm to provide the switching signals using the simple digital logic circuit is presented. As a result, a stable high speed SRM drive can be achieved by the high resolution switching angle control and it is verified from the experiments that the proposed encoder and its logic controller can be a powerful candidate for the practical low cost SRM drive.