Design and characterization of electronic sensing system for a 13 × 13 biomechanical ground reaction sensor array

This paper presents the design and characterization of an electronic sensing system interfaced with 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 over time 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 x 13 GRSA to a capacitance-to-voltage converter followed by a 12-bit ADC sampled at 66.7 k-samples/sec, a digital timing & control unit, and a driving circuitry. The electronics were fabricated in XFAB 0.35 μm CMOS process and can achieve a gait ground velocity sensing resolution of 40 μm/sec while dissipating 3mW power.