Volitional Walking Controller for Powered Prostheses
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Solution Overview
Problem
Conventional powered prostheses for above-knee amputations lack adaptability in swing trajectory control, making it difficult for users to navigate environmental barriers such as curbs and uneven surfaces, and they require explicit classification of the environment for trajectory adjustment.
Innovation Solution
A powered prosthesis with a controller that continuously modulates the knee flexion trajectory based on the user's residual limb movements, using a minimum jerk engine to update the desired knee joint position, velocity, and acceleration, allowing for volitional control of foot clearance without explicit environmental classification.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If position-based controllers are used to simplify tuning and provide flexibility, then ease of operation is improved, but adaptability to environmental barriers deteriorates
Solution Approach 1:
The controller dynamically adjusts impedance parameters (stiffness, damping, equilibrium point) during the swing phase based on real-time thigh angle measurements. This allows the system to transition from a static, pre-programmed trajectory to a dynamic, adaptive trajectory that responds to environmental barriers while maintaining the simplicity of position-based control.
Solution Approach 2:
The system continuously monitors the thigh angle of the residual limb and uses this feedback to modulate the desired prosthesis trajectory. This feedback loop enables the controller to adapt the knee flexion trajectory in real-time without requiring complex environmental classification, thus maintaining ease of operation while improving adaptability.
2Adaptability or versatility
If classification-based controllers are used to achieve ambulation over different terrains, then adaptability is improved, but device complexity increases
Solution Approach 1:
The patent extracts only the essential feedback signal (thigh angle) needed for trajectory adaptation, eliminating the need for complex environmental classification systems. By taking out just the necessary sensory input and processing it through a simplified controller, the system achieves terrain adaptability without the complexity of classification-based approaches.
3Reliability
If swing trajectory is determined by impedance parameters tuned to imitate nominal knee trajectory, then reliability is improved, but adaptability deteriorates
Solution Approach 1:
The system transforms the static impedance parameters into dynamic, time-varying parameters that are continuously adjusted during swing based on thigh angle feedback. This dynamic adjustment allows the reliable, tested impedance-based control to adapt to different terrains and walking conditions without sacrificing its proven reliability.
Data Source
AI summary
A powered prosthesis for providing volitional control of knee flexion during swing is configured to (i) determine that a swing phase has initiated, (ii) obtain a thigh angle based on the sensor data associated with a residual limb of a user, (iii) based on a time elapsed since initiation of the swing phase, and based on the thigh angle, determine a desired maximum knee flexion angle, (iv) during the swing phase, continuously update the desired maximum knee flexion angle using subsequent measurements of thigh angle and time elapsed since initiation of the swing phase, and (v) output a signal configured to cause actuation of the knee joint based on the desired maximum knee flexion angle.