A prototype wireless inertial-sensing device for measuring toe clearance

Tripping and slipping are serious health concerns\ud for the elderly because they result in life threatening injuries i.e.,\ud fractures and high medical costs. Our recent work in detection\ud of tripping gait patterns has demonstrated that minimum\ud toe clearance (MTC) is a sensitive falls risk predictor. MTC\ud measurement has previously been done in gait laboratories\ud and on treadmills which potentially imposes controlled walking\ud conditions. In this paper, we describe a prototype design\ud of a wireless device for monitoring vertical toe clearance.\ud The sensors consists of a tri-axis accelerometer and dual-axis\ud gyroscope connected to Crossbow sensor motes for wireless\ud data transmission. Sensor data are transmitted to a laptop and\ud displayed on a Matlab graphic user interface (GUI). We have\ud performed zero base and treadmill experiments to investigate\ud sensor performance to environmental variations and compared\ud the calculated toe clearance against measurements made by\ud an Optotrak motion system. It was found that device outputs\ud were approximately independent of small ambient temperature\ud variations, had a reliable range of 20m indoors and 50m\ud outdoors and a maximum transmission rate of 20 packets/s.\ud Toe clearance measurements were found to follow the Optotrak\ud measurement trend but could be improved further by dealing\ud with double integration errors and improving data transmission\ud rates