High accuracy torque measurement with position measuring devices

The measurement of torque is often based on a measured deformation, which results from a torsional load acting on the sensor. Strain gauges are standard devices for quantifying the deformation. In this paper, a device determining the torque based on a measured relative distortion of a torsional flexible body is presented. Two position measuring devices are used to determine the relative distortion. The design criteria for the flexible body of the sensor are discussed. A prototype using the proposed measurement principle was built up and analyzed regarding the achievable accuracy of the torque measurement at pure torsional loads and also under disturbing loads. The results show a high accuracy in the torque measurement with a linearity error in the range of 0.11% of the maximum torque. The influence of disturbing loads on the torque measurement can be neglected, which is an advantage compared to other torque sensors.