Power Wheelchair Footplate Pressure and Positioning Sensor.

Power wheelchair users are at risk for severe injuries caused by foot mis-position on the footplate. This can lead to collisions or foot dragging which are severe or lifethreatening injuries for people with spinal cord injuries. The foot cannot be safely immobilized due to tilting pressure relief injuries, therefore, the foot can easily fall into a vulnerable position without the user realizing it. To reduce the likelihood of injury, we have developed a sensor for monitoring foot position in real time, as the wheelchair is driven. The sensor uses an array of force-sensing resistors and infrared distance sensors to detect the pressure and location of the foot within the immediate confines of the footplate. Sensor arrays with 23 force sensors and 14 infrared sensors per foot were fabricated on standard printed circuit boards and encapsulated in a durable thermoplastic urethane for environmental resistance. Fabricated sensors transmitted foot pressures and position data at 10 Hz using a Bluetooth Low Energy radio. An iOS app was developed to notify users of vulnerable foot position. Measured results confirmed the functionality of the system over typical foot pressures, and indicated that the device is ready for next-stage clinical trials with spinal cord injured power wheelchair users.