Sensor sensitivity to posture transitions in a lower-extremity orthotic device

This study evaluates sensitivity and relative timing of a system of sensors in detecting posture transitions by a user wearing a lower-extremity orthotic device. The sensors in the orthosis included accelerometers, gyroscopes, potentiometers, and force sensitive resistors positioned at various locations. Data was collected from subjects wearing the orthotic device while seated, followed by a transition to a standing position and a transition to walking. The initial posture and rate of the transition were varied to cover a range of initial conditions and transitions speeds. The data collected from three healthy adults were used to perform initial analysis of repeatability of sensor signals to identify sensors that reliably respond to certain posture transitions. Relative timing of the sensors was studied to identify sensors that respond the earliest to a posture transition and thus potentially be used to recognize user´s intent to change posture. The results suggest that accelerometers and gyroscopes located on the lateral side of the shank and thigh may detect transition events earlier and more consistently than potentiometers on the knee and ankle joints and force sensitive resistors on the sole of the foot.