Powered Ankle-Foot Prosthesis Multi-Axis Impedance Control
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Solution Overview
Problem
Conventional ankle-foot prostheses are inadequate for efficient locomotion, particularly during turning, as they lack the ability to modulate impedance and admittance in multiple axes, leading to increased energy consumption and reduced mobility in amputees compared to able-bodied individuals.
Innovation Solution
A powered prosthesis system that includes a multi-axis ankle with a socket, shaft, foot piece, and motor assembly, equipped with a computer and sensors to detect states and control impedance and position, allowing for both impedance modulation at push-off and admittance modulation at heel-strike, enhancing maneuverability and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If passive prosthesis are used, then the device complexity is reduced, but the energy consumption increases and mobility is reduced
Solution Approach 1:
The patent replaces passive mechanical structures with an active powered system that uses electrical motors to generate motion. The motor assembly converts electrical energy to mechanical work, actively controlling ankle joint movement in both sagittal and coronal planes, thereby reducing the metabolic energy burden on the user while providing controlled locomotion assistance.
Solution Approach 2:
The prosthesis transitions from a static passive structure to a dynamic active system with real-time control. The powered ankle joint dynamically adjusts its motion and impedance based on gait phase and terrain, enabling adaptive response to varying locomotion requirements and improving overall mobility efficiency.
2Device complexity
If conventional single-axis prostheses are used, then the device complexity is reduced, but the adaptability to different gait conditions deteriorates
Solution Approach 1:
The powered ankle prosthesis integrates multiple functions into a single device: it provides dorsiflexion-plantarflexion motion in the sagittal plane and inversion-eversion motion in the coronal plane. This multi-functional design enables the prosthesis to adapt to various gait conditions including straight walking, turning, and uneven terrain, replacing the need for multiple specialized passive components.
Solution Approach 2:
The control system is segmented into independent control loops for different degrees of freedom (sagittal plane and coronal plane movements). This segmentation allows each control module to independently manage specific motion aspects, enabling flexible adaptation to different gait requirements without increasing overall system complexity.
3Ease of manufacture
If passive prosthesis are used, then the manufacturing cost is reduced, but the productivity of locomotion deteriorates
Solution Approach 1:
The patent replaces passive mechanical energy storage and transfer mechanisms with an active powered system that directly generates the necessary work. The motor assembly provides active propulsion during push-off and controlled dorsiflexion during swing phase, significantly improving locomotion efficiency and reducing the metabolic cost for the user compared to passive mechanical systems.
4Ease of operation
If multi-axis powered control is implemented, then the maneuverability during turning is improved, but the device complexity increases
Solution Approach 1:
The patent merges the control of multiple degrees of freedom into a single integrated motor assembly. The motor simultaneously controls both sagittal plane (dorsiflexion-plantarflexion) and coronal plane (inversion-eversion) movements through a unified power and control architecture, reducing the number of separate actuators and simplifying the overall system while maintaining full maneuverability.
Data Source
AI summary
A system and method for operating a prosthesis is provided. The system includes a socket configured to engage a residual limb of a subject and a shaft having a first end connected to the socket and an opposing second end. The system also includes a foot piece connected to the second end of the shaft. The foot piece includes an ankle plate and a sole piece configured to contact a surface. The system also includes at least one computer configured to detect a state of the foot piece and to transmit an indication of the state of the foot. The system further includes a motor assembly configured to receive the indication of the state of the foot and to control a position and impedance of the ankle plate based on the state of the foot.