A large-area tactile force sensor for measuring ground reaction forces from small legged robots

This work presents the design, fabrication, calibration, and testing of a multi-touch force sensor designed to measure normal ground reaction forces generated by highspeed locomotion of milli-scale legged robots. The sensor is based on the optical principle of frustrated total internal reflection (FTIR) and is capable of resolving multiple simultaneous normal forces in the range of 50-1000 mN at a rate of 250 Hz with measurement error of less than 1%. The sensor is integrated with commercial, off-the-shelf motion capture hardware and the whole system is demonstrated with a simple experiment tracking a bouncing ball and simultaneously-recording kinematic state and ground reaction force data.