Torque Sensing from Harmonic Drives by Using Three Strain Gages

The paper addresses the topic of torque sensing by using strain gages, which are cemented directly on the flexpline of Harmonic Drive gear reducer. Conventionally two or four strain gages were used to reduce the ripple signal, which is generated by the gear operation, however, our analysis shows that three strain gages are more suitable for the ripple compensation. In the paper, we present a mathematical model fof the ripple and explain the new method for successful compensation. The method does not need on-line calculations and reduces requirements on the strain gages positioning accuracy, therefore it easy to be practically implemented.