On a new torque sensor for tendon drive fingers

A new type of torque sensor is proposed for finger actuation with N actuators and tendons per N external degrees of freedom. The finger joint around a drive pulley is proportional to the tension difference on both ends of the pulley. Using a coupling mechanism between tendons, this tension difference can be measured directly without sensing individual tendon tensions. On the basis of this idea, a tension differential-type torque (TDT) sensor is proposed. With a single body of small size and fewer signal lines, the TDT sensor has several advantages over the conventional approach, which obtains the torque by attaching two tension sensors at both ends of the drive pulley and feeding sensor signals to a differential circuit. The basic principle of the TDT sensor is described, together with the design orientation. The dynamic and static characteristics are examined with the introduction of equivalent rotational stiffness, which is useful for examining system stability. The specially designed TDT sensors were implemented in a two-fingered robot hand, and the effectiveness of the sensor was confirmed