Electronic sensing system with flexible biomechanical ground reaction sensor array achieving 100 μm/sec gait ground velocity resolution

This paper presents a prototype electronic sensing system design for a high-density flexible biomechanical ground reaction sensor array (GRSA). The prototype system can be incorporated into a personal boot heel to measure real-time ground force, shear strain and sole deformation associated with a human bipedal locomotion, thus providing zero-velocity correction to an inertial measurement unit placed in a close proximity. This approach can greatly reduce inertial error accumulation and improve positioning accuracy. The electronic sensing system consists of a front-end multiplexer that can sequentially connect individual capacitive sensing nodes from a 13 × 13 GRSA to a capacitance-to-voltage converter followed by a 12-bit ADC sampled at 66.7 k-samples/sec. The entire sensor array can be scanned within 10 msec. The integrated sensing electronics are fabricated in XFAB 0.35 μm CMOS process and dissipate 3mW power. Static and dynamic pressure testing demonstrates the prototype system functionality achieving a gait ground velocity sensing resolution of 100 μm/sec.