Design and Characterization of a New Soft Fingertip Force Sensor for Precision Robotic Grasping Task

Nowadays, a new robotic field has emerged, called Soft Robotics, and it is a new field that involves new challenges, such as soft manipulation, considering external force measure or contact sensors. Thus, in this paper, a new soft fingertip force sensor is introduced. The methodology proposed consists in a quantitative applied research aiming to propose a device able to detect and measure external applied forces. In order to reach the above target, the following steps have been performed: i.) requirements identification, ii) transductor selection, ii) rigid structure design, iii.) soft structure design, iv.) definition of variables parameters for sensor characterization, v.) implementation of the experiments to quantify the relation between external forces and output voltage for different operation conditions, and vi.) proposition of the mathematical model. The mathematical model is defined to describe applied external force and sensor output voltage, demonstrating different mathematical models for two soft materials (polyaddition and polycondensation silicones). It has been found out that using a softer silicone increases the sensor sensitivity. However, the selection of silicone depends on the application requirements. Moreover, the use of soft materials gives a high compliance level with contact objects. On the other hand, a new sensor structure that could be implemented using a 3D print and a FSR traductor, easily implemented by a 3D Printer, has been proposed. Then the mathematical model presented could be used by researchers Moreover, researchers could modify the parameters explained in order to obtain different soft sensor performance. Thus, the soft sensor is endowed with versatility, compliance, and molding.