Powered Leg Prosthesis Knee Ankle Joint Control
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Solution Overview
Problem
Current commercial transfemoral prostheses are energetically passive, unable to deliver net power at joints, limiting their ability to restore normal locomotive functions such as walking up stairs or slopes, and lack a natural gait behavior.
Innovation Solution
A powered leg prosthesis with a powered knee and ankle joint, equipped with motor units, sensors, and a control system that allows for real-time energy delivery based on user input, enabling net energy transfer during specific phases of the gait cycle, and a control methodology that decomposes joint behavior into passive and active components for stable interaction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If passive energy storage/dissipation mechanisms are used in prosthetic joints, then device complexity is reduced and reliability is improved, but the ability to deliver net power and restore normal locomotive functions is impaired
Solution Approach 1:
The prosthesis is divided into separate functional modules: a powered knee joint with motor unit and a powered ankle joint with motor unit. Each joint can independently deliver power, allowing the system to restore normal locomotive functions while managing complexity through modular design. The segmentation enables targeted power delivery at specific joints based on gait phase requirements.
Solution Approach 2:
The prosthesis transitions from static passive energy storage to dynamic active power delivery. Motor units provide time-varying torque that adapts to different gait phases (stance, swing, transition), enabling the delivery of net power during specific phases while maintaining controlled interaction during others. This dynamic behavior restores natural gait patterns that require active power modulation.
2Adaptability or versatility
If active power delivery is implemented at joints, then ability to restore locomotive functions is improved, but energy consumption and control complexity increase
Solution Approach 1:
The control system operates in periodic cycles corresponding to the gait cycle, with motor units delivering power during specific phases (e.g., push-off at ankle, extension at knee) and remaining inactive or dissipating energy during other phases. This periodic activation pattern enables adaptable gait behavior while managing energy consumption by avoiding continuous power delivery.
Solution Approach 2:
The control system uses feedback from joint position sensors and force sensors to modulate motor unit output in real-time. This feedback mechanism allows the prosthesis to adapt to varying terrain, user intent, and gait phase requirements, providing versatile gait behavior while optimizing energy usage based on actual mechanical demands rather than continuous operation.
3Measurement precision
If multiple sensor inputs and control algorithms are used to achieve natural gait, then measurement precision and control accuracy are improved, but device complexity and difficulty of manufacture increase
Solution Approach 1:
The control system integrates multiple sensor inputs (joint position, force, acceleration) into a unified control algorithm that manages both knee and ankle motor units. This multi-functional controller handles diverse measurement tasks and actuation requirements through a single integrated system, improving measurement precision while avoiding the need for separate dedicated systems for each function, thereby simplifying manufacturing.
Data Source
AI summary
A powered leg prosthesis includes powered knee joint comprising a knee joint and a knee motor unit for delivering power to the knee joint. The prosthesis also includes a prosthetic lower leg having a socket interface coupled to the knee joint and a powered ankle joint coupled to the lower leg opposite the knee joint comprising an ankle joint and an ankle motor unit to deliver power to the ankle joint. The prosthesis further includes a prosthetic foot coupled to the ankle joint, at least one sensor for measuring a real-time input, and at least one controller for controlling movement of the prosthesis based on the real-time input.