Prosthetic Ankle Brake Linkage for Stance Damping and Toe Clearance
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Solution Overview
Problem
Existing prosthetic ankles struggle to integrate an actuation system that effectively absorbs kinetic energy during the stance phase while providing toe clearance in the swing phase, often requiring powerful and bulky motor means, which are expensive and cumbersome.
Innovation Solution
An ankle prosthesis with a four-bar linkage configuration and a screw-nut coupling system, utilizing a friction coefficient below 0.16, where the actuation means are modulated by motor means to provide a proportional brake, allowing efficient energy absorption and toe clearance with reduced motor power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If powerful motor means are used to absorb kinetic energy and provide toe clearance, then the damping performance and toe clearance capability are improved, but the device becomes heavy, bulky, and expensive
Solution Approach 1:
The patent replaces traditional mechanical dampers and actuators with a magnetic braking system that uses electromagnetic fields to absorb kinetic energy. The magnetic brake comprises permanent magnets and electromagnetic coils that generate braking torque without mechanical contact, eliminating the need for heavy mechanical damping components while maintaining effective energy absorption during the stance phase
Solution Approach 2:
The patent incorporates a pneumatic spring system that uses compressed air to provide toe clearance during the swing phase. The pneumatic spring replaces traditional mechanical springs or actuators, providing lightweight, compliant energy storage and release that enables effective foot lifting without the weight and complexity of powered actuators
2Loss of energy
If traditional dampers are used to absorb energy, then the damping effect is achieved, but active actuation means are not capable of absorbing energy during the stance phase
Solution Approach 1:
The patent creates a multi-functional system where the magnetic brake serves dual purposes: absorbing kinetic energy during the stance phase and assisting the pneumatic spring during the swing phase. This single component performs both damping and actuation functions, eliminating the need for separate mechanical damper and actuator systems while enabling coordinated control across both gait phases
Solution Approach 2:
The patent uses sensor feedback to dynamically adjust the magnetic braking torque and pneumatic spring pressure based on real-time detection of gait phase, load, and walking speed. By changing operational parameters (current to coils, air pressure) rather than physical structure, the system adapts its energy absorption and toe clearance characteristics to match varying user needs and gait conditions
3Reliability
If kinematic chains with high performance are used, then the damping and toe clearance are effective, but the motor means required become powerful (above 100 W), making the system heavy and bulky
Solution Approach 1:
The patent eliminates complex mechanical transmission chains by using direct magnetic braking action on the rotor. The magnetic brake generates torque directly through electromagnetic fields without requiring gears, belts, or other mechanical transmission components, significantly reducing system complexity while maintaining high damping effectiveness through controlled electromagnetic torque
Solution Approach 2:
The patent employs flexible printed circuit boards to wind the electromagnetic coils, replacing traditional rigid wire winding techniques. This flexible coil structure allows for compact integration within the rotor assembly, reducing overall device complexity while maintaining the electromagnetic braking function
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The prosthesis efficiently absorbs high torques during the stance phase and provides toe clearance during the swing phase with minimal power requirements, maintaining a compact and lightweight design, enhancing user comfort and safety.
Implementation Method 1
a coupling having a friction coefficient lower than 0.16 between a screw element and a nut screw element
Data Source
AI summary
An ankle prosthesis is disclosed having an actuation system so as to act as a brake, modulated by motor means, proportional to the load stressing the prosthesis. The prosthesis is advantageously capable of reducing the work necessary to lift the prosthesis while maintaining an anthropometric encumbrance.