Powered Knee and Ankle Prosthesis with Adaptive Control Enables Climbing
Stairs with Different Stair Heights, Cadences, and Gait Patterns
- Sarah Hood ,
- Lukas Gabert ,
- Tommaso Lenzi
Abstract
Powered prostheses can enable individuals with above-knee amputations to
ascend stairs step-over-step. To accomplish this task, available stair
ascent controllers impose a pre-defined joint impedance behavior or
follow a pre-programmed position trajectory. These control approaches
have proved successful in the laboratory. However, they are not robust
to changes in stair height or cadence, which is essential for real-world
ambulation. Here we present an adaptive stair ascent controller that
enables individuals with above-knee amputations to climb stairs of
varying stair heights at their preferred cadence and with their
preferred gait pattern. We found that modulating the prosthesis knee and
ankle position as a function of the user's thigh in swing provides toe
clearance for varying stair heights. In stance, modulating the
torque-angle relationship as a function of the prosthesis knee position
at foot contact provides sufficient torque assistance for climbing
stairs of different heights. Furthermore, the proposed controller
enables individuals to climb stairs at their preferred cadence and gait
pattern, such as step-by-step, step-over-step, and two-steps. The
proposed adaptive stair controller may improve the robustness of powered
prostheses to environmental and human variance, enabling powered
prostheses to more easily move from the lab to the real-world.