Design and Evaluation of a Wearable Haptic Feedback System for Lower Limb Prostheses During Stair Descent

Abstract

We designed a wearable haptic feedback system to assist stair descent for users of lower limb prostheses. Our haptic feedback system consists of a custom insole with four force sensors, a thigh band with four vibrotactile actuators, and an on-board embedded processor. The loss of sensation and range of motion in the foot-ankle complex presents a challenge to lower limb prosthesis users during stair descent. By providing force information through haptic feedback, we restore access to sensory information of the stair edge. We tested our system on 2 subject experiments. In the first experiment, 15 subjects wearing the thigh band were tasked to report the perceived position of stimulation on the sensor insole. All subjects were able to detect the stimulation position in terms of the actuator that was vibrating with a minimum of 82% accuracy for all four positions. In the second experiment, 13 subjects wore the haptic feedback system and the sensor insole and stepped on a visually obstructed staircase step of variable depth. Overall, the provision of haptic feedback reduced error in reporting the step edge position. Our haptic feedback system demonstrates the capability to provide sensory information that is otherwise absent, enabling a more natural stair descent. Future work includes performing the experiments on subjects with lower limb amputation and a complete stair descent performance assessment wearing the haptic feedback system.