Digital speed control system for a motor using two speed detection methods of an incremental encoder

A digital speed control system for a motor with an incremental shaft encoder has been used as a basic system that drives various industrial machines. The speed control system using the conventional speed detection method (MT method) has a problem in that the mechanical errors of the encoder slit intervals cause the motor speed fluctuation in the steady state. In this paper, a new speed detection method (SR method) that is not influenced by mechanical errors is proposed. Furthermore, a speed control system that uses the MT method in the transient state and the SR method in the steady state is proposed. Simulation and experimental results show that the proposed speed control system has a fast response and few speed fluctuations. The proposed system can be realized at low cost because it does not require a high-accuracy encoder or any additional hardware.