Low-cost direct torque control of permanent magnet synchronous motor using Hall-effect sensors

In this paper, a direct torque control (DTC) scheme for permanent magnet (PM) synchronous motors (surface-mount type) using cost-effective Hall-effect sensors for constant torque region is presented. Unlike conventional DTC proposed method estimates necessary quantities in the rotor reference frame by obtaining continuous position and speed information from the Hall-effect sensors resembling expensive high resolution position sensors (encoder and resolver). Furthermore, this method requires no dc-link sensing and removes some common problems those conventional DTC drives suffer from such as the effect of resistance change, low speed operation integration drift, and the initial rotor position requirement. The proposed drive, considering the constant torque region operation, is applied to the agitation part of a laundry washing machine for speed and torque performance comparison with the existing low-cost agitation cycle speed control technique used by some washing machine companies around the world. Results of the tests clarify the effectiveness of the proposed DTC scheme over the commercial agitator speed control and even conventional DTC drive.