Biomimetic Prosthetic Ankle Torque Control
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Solution Overview
Problem
Current prosthetic ankle-foot devices, especially powered ones, lack adaptive capabilities to varying terrain and walking speeds, leading to inefficient gait patterns and increased metabolic energy expenditure in amputees, as they rely on fixed torque-ankle state relationships and fail to integrate principles of legged mechanics effectively.
Innovation Solution
A neuromuscular model-based control system that utilizes sensory feedback to command biomimetic torques at the ankle, knee, and hip joints, incorporating a muscle model and reflex control equations to dynamically adjust stiffness, damping, and power output, mimicking human locomotion principles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If fixed torque-ankle state relationships are used in powered prosthetic devices, then device complexity is reduced, but adaptability to varying terrain and walking speeds deteriorates
Solution Approach 1:
The patent implements dynamic control by transitioning from fixed torque-ankle state relationships to a neuromuscular model that continuously adapts torque commands based on real-time sensory feedback from sensors mounted at each joint. The system dynamically adjusts stiffness, damping, and power output to match varying terrain conditions and walking speeds, resolving the contradiction between simplicity and adaptability.
Solution Approach 2:
The patent employs sensory feedback from sensors mounted at each joint of the robotic leg device to continuously monitor joint state and feed this information back to the neuromuscular model. This feedback loop enables the system to adapt to varying terrain and walking speeds while maintaining a relatively simple device architecture, thus resolving the technical contradiction.
2Ease of operation
If fixed torque-ankle state relationships are used, then ease of operation is improved, but metabolic energy expenditure increases
Solution Approach 1:
The patent implements self-service control where the neuromuscular model autonomously generates appropriate torque commands based on sensory feedback and integrated principles of legged mechanics. The system self-adjusts to varying conditions without requiring complex user intervention, maintaining ease of operation while optimizing energy efficiency by producing gait patterns that reduce metabolic energy expenditure.
3Adaptability or versatility
If neuromuscular model with sensory feedback is implemented, then adaptability to terrain and speeds is improved, but device complexity increases
Solution Approach 1:
The patent applies universality by using a single neuromuscular model that performs multiple functions: it processes sensory feedback, generates torque commands, adjusts stiffness, and adapts to various terrain conditions and walking speeds. This multi-functional approach achieves high adaptability without proportionally increasing device complexity, as one integrated system handles diverse control tasks.
4Productivity
If biomimetic torques are commanded based on neuromuscular model, then gait efficiency is improved, but manufacturing precision requirements increase
Solution Approach 1:
The patent employs parameter changes by dynamically adjusting torque commands, stiffness, and damping parameters based on sensory feedback and the neuromuscular model. The system adapts these parameters in real-time to optimize gait efficiency for varying terrain and speeds, achieving high productivity while managing manufacturing precision requirements through software-based parameter adaptation rather than requiring ultra-precise mechanical components.
Data Source
AI summary
Artificial limbs and joints that behave like biological limbs and joints employ a synthetic actuator which consumes negligible power when exerting zero force, consumes negligible power when outputting force at constant length (isometric) and while performing dissipative, nonconservative work, is capable of independently engaging flexion and extension tendon-like, series springs, is capable of independently varying joint position and stiffness, and exploits series elasticity for mechanical power amplification.