Inertial Sensing for Gait Event Detection and Transfemoral Prosthesis Control Strategy

Objective: This paper presents a method for walking gait event detection using a single inertial measurement unit (IMU) mounted on the shank. Methods: Experiments were conducted to detect heel strike (HS) and toe off (TO) gait events of 10 healthy subjects and 5 transfemoral amputees walking at various speeds and slopes on an instrumented treadmill. The performance of three different algorithms [thresholding (THR), linear discriminant analysis, and quadratic discriminant analysis] was evaluated on both timing and frequency of gait event detections compared to data collected using force plates. Results: Though all algorithms could be used reliably (within 8.2% stride temporal error and 0.2% frequency error), THR was the most accurate, detecting 100% of gait events within an average of 2% stride for both the healthy subjects and the amputees. Furthermore, universal parameters could be used across all speeds and slopes within each demographic. Conclusion: HS and TO for walking gait can be reliably detected in healthy and transfemoral amputee subjects using a single IMU. Significance: This work provides a robust, simple, and inexpensive method of gait event detection that does not rely on a load cell and could be easily implemented in a lower-limb prosthesis.