Gait Mode Recognition Using an Inertia Measurement Unit on a Powered Ankle-foot-orthosis

One of the challenges that any powered lower limb orthotic or prosthetic device must address for activities in the real world is its ability to recognize gait modes (level ground walking, stairs, ramps, etc.) and adapt to mode changes promptly. There are two critical aspects of this problem. First, the gait mode has to be recognized at the earliest possible time to prevent potential misfiring (e.g., plantarflexor assistance during stair descent). Failing to do so can increase the fall risk of the wearer dramatically. Second, the device must have enough sensors to reliably detect gait mode. In the PPAFO, the original sensor array had only three sensors (heel and toe contact force and ankle joint angle). This construction limited sensing ability.