Measuring System with dual magnetic sensors for outer-rotor type torque motor

As there is no round optical grating and magnetic grating with large diameter that is over 0.5m in the market, a measuring system adopting dual magnetic sensors based on FPGA is proposed in this paper to measure the position/displacement and velocity of the rotating outer-rotor motor. Through using strip-type magnetic grating to stick around the outer rotor over half circumstance, the proposed system is able to produce continuous position pulse signals by switching the signals of dual magnetic sensors. The system core chip distinguishes, subdivides and filters the signals from two sensors, judging the operational state of the sensor and generating the dual magnetic sensor switching signals. It can switches the sensor signals in real time during motor operation and measures the position/displacement and velocity of motor in a precise manner. Moreover, the position/displacement, operating time and positive/negative rotation can be displayed through man-machine interactive unit. The experimental results show that arc-second control accuracy of the outer-rotor torque motor can be achieved by using the proposed system to measure the speed and position/ displacement of the outer-rotor torque motor as the feedback signal through the motion control system of motor.