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Stair Ascent Phase-Variable Control of a Powered Knee-Ankle Prosthesis
Ross J Cortino1, Edgar Bolívar-Nieto1, T Kevin Best1
1Department of Electrical Engineering and Computer Science and the Robotics Institute, University of Michigan, Ann Arbor, MI 48109.
IEEE International Conference on Robotics and Automation : ICRA : [Proceedings]. IEEE International Conference on Robotics and Automation
|September 5, 2022
Summary
This study introduces a novel controller for powered knee-ankle prostheses, enabling natural stair ascent. The controller synchronizes joint motion using residual thigh movement, providing essential positive mechanical work for users.
Area of Science:
- Biomedical Engineering
- Robotics
- Biomechanics
Background:
- Passive prostheses lack the power for stair ascent.
- Powered prostheses require precise user synchronization for natural gait.
- Existing control methods need refinement for stair ascent tasks.
Purpose of the Study:
- To develop a phase variable-based controller for powered knee-ankle prostheses.
- To enable natural stair ascent gaits by synchronizing joint motion with user's residual thigh movement.
- To allow powered prostheses to perform net positive mechanical work during stair ascent.
Main Methods:
- Developed a stair ascent controller driven by residual thigh motion.
- Utilized reference kinematics from able-bodied data for joint trajectories.
- Redefined the gait cycle starting at maximum hip flexion for improved phase estimation.
- Validated the controller using able-bodied bypass adapter experiments.
Main Results:
- The controller replicated normative able-bodied kinematic trajectories with low root mean squared error (12.66° knee, 2.64° ankle).
- Powered knee and ankle joints delivered net positive mechanical work (0.39 J/kg and 0.21 J/kg per stride).
- Performance closely matched normative averages for able-bodied individuals.
Conclusions:
- The proposed controller effectively enables powered knee-ankle prostheses to assist stair ascent.
- Synchronization of joint motion via residual thigh movement is critical for natural gait.
- This advancement allows for net positive mechanical work, improving prosthesis functionality.
