A simple and easy-to-build optoelectronics force sensor based on light fork: Design comparison and experimental evaluation

In this paper, the design and the implementation of a force sensor based on a commercial optoelectronic component called light fork and characterized by the simple construction process is presented. The proposed sensor implementation is designed to measures the force applied by a cable-based actuation by detecting the deformation of a properly designed compliant structure integrated into the actuation module. Despite this, the design method here presented allows to adapt the sensor to a large set of robotic applications, thanks to its simplicity in the construction and low cost. The main advantages of the proposed sensor consist in the use of a very compact commercial optoelectronic component, called light fork, as sensing element. This solution allows a very simple assembly procedure together with a good sensor response in terms of sensitivity, linearity and noise rejection to be achieved using an extremely simple electronics, thereby obtaining in this way a reliable and very cheap sensor that can be easily integrated in actuation modules for robots and can easily adapted to a wide application set. The paper presents the basic sensor working principle and the compliant frame design. An analytic model of the compliant frame deformation is proposed and verified both by finite element analysis and by experimental measures performed on four different sensor specimens manufactured by 3D printing and CNC milling, and the results have been compared. Moreover, the sensor specimens calibration and the experimental validation have been performed both in static and dynamic conditions.