Design of a flexible tactile sensor for measuring fingertip force and contact recognition

Abstract

Among the various ways to apprehend the user intention in hand exoskeletons, measuring a contact force is definitely the most straightforward and intuitive method of attracting one's intention in grip motion. The main problem of this method is that a force sensor, being located at the center of a fingertip, hinders the tactile sensation of the user. To overcome this problem, indirect force measurement is inevitable when it comes to measuring the contact force and acquiring the tactile sensation. This work presents the mechanical design, implementation and evaluation of a soft fingertip force sensor. To maximize tactile sensation of the user, we adopted a horse-hoof-shape structure to make the front side of the sensor widely opened. Optical sensing mechanism was selected because it showed compatibility with a transparent soft elastomer. The whole sensor system has a soft exterior so that it gives conformability and user-friendly interface. To test the sensor’s performance, a customized test bed was designed. We tested three different dimensions of the sensors and executed the design parameter study. Then, we investigated both static and dynamic response and observed how the mechanical behavior and light intensity change are related via system identification. Lastly, we applied the proposed sensor to the glove actuating system to extract human intention.