A Miniaturized Optical Force Sensor for Tendon-driven Mechatronic Systems: Design and Experimental Evaluation

In this paper, an innovative sensor for the control of a tendon-driven mechatronic system is presented. The proposed sensor measures the tendon tension using optoelectronic components properly selected and mounted on a suitably designed compliant frame. This solution presents several advantages mainly in terms of simplicity and compactness with respect to force sensors based on strain-gauge or Bragg-grating. By exploiting the properties of optoelectronic components with a narrow angle of view and by means of a very simple conditioning electronics, the very small deformation of the compliant frame caused by the tendon force can be measured. Moreover, the compliant frame has been designed to allow the sensor to be mounted in any position along the tendon. The sensor working principle, an optimal design procedure and the results of an experimental testbench where two of the proposed sensors are used for the feedback control of a tendon-driven mechatronic system are reported in the paper. The experimental verification of a contact force estimation algorithm useful for grasping and manipulation purposes in which the data collected by the optoelectronic tendon force sensors are exploited is also reported in the paper