Performance of a newly developed torque-sensor motor

Abstract A new type of induction motor with a built-in torque sensor (called a ‘torque-sensor motor’) has been developed in order to monitor grinding torque. Its rotor shaft consists of a hollow shaft and torsion bar, each of which has a disc with equiangularly located magnets. The torque output is calculated by microcomputer from the time delay of pulses generated in detecting coils. This toque sensor has good linearity. Torque ripple and zero-point drift caused by rotational speed change are estimated to be less than 1 Nm. It is so sensitive that it can detect torque ripple from rotational error of the driving belts on the grinding machine. Further, it can accurately monitoring grinding torque by using a low pass filter to remove such torque ripple. It can also be used to estimated the time constant of the grinding wheel and workpiece system in the transient torque situation of a grinding cycle. The performance of the grinding wheel motor is as good as that of a conventional motor.