Passive Artificial Knee Using Ground Reaction Force Locking
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Solution Overview
Problem
Current above-knee prostheses in developing countries often employ single-axis joints with mechanical failures and high costs, limiting user satisfaction and accessibility for amputees due to socio-economic constraints.
Innovation Solution
A passive artificial knee design featuring a knee hinge assembly and locking hinge assembly that utilizes ground reaction force to lock and unlock rotation, eliminating the need for onboard energy and reducing mechanical failures, while being cost-effective and suitable for resource-constrained settings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If passive artificial knee is designed to enable able-bodied kinematics, then user satisfaction and gait quality improve, but device complexity increases
Solution Approach 1:
The knee assembly is divided into functionally independent components: a knee hinge assembly defining a knee axis, a locking hinge assembly defining a locking axis, and a post linking them. This segmentation allows each component to perform its specific function (knee flexion/extension, locking/unlocking) independently, achieving complex gait control through simple, modular elements rather than a single complex mechanism.
Solution Approach 2:
The locking and unlocking mechanism is entirely passive and self-actuating, utilizing ground reaction forces during the gait cycle to automatically lock the knee during heel strike/early-stance and unlock during mid-stance. No onboard energy source, motors, or active control systems are required—the terrain itself provides the energy to control knee rotation, eliminating complex power and control systems while maintaining high gait quality.
2Reliability
If passive artificial knee uses ground reaction force for locking mechanism, then reliability improves by reducing mechanical failures, but device complexity increases
Solution Approach 1:
The design converts the typically harmful or uncontrollable ground reaction forces into a beneficial locking and unlocking mechanism. During heel strike and early-stance, the ground reaction force creates an interfering relation that locks the knee; during mid-stance, the same force mechanism unlocks the knee. This transforms environmental forces that could cause instability into the primary control mechanism, improving reliability without adding complex active control systems.
Solution Approach 2:
The patent eliminates manual locks and complex mechanical failure points by using a passive locking mechanism. The interfering relation between the locking hinge assembly and knee hinge assembly creates automatic locking during critical gait phases, removing the need for manual intervention and reducing mechanical failures associated with traditional locked-knee designs.
3Ease of manufacture
If artificial knee is designed for developing countries with resource constraints, then accessibility and affordability improve, but manufacturing precision requirements increase
Solution Approach 1:
The knee assembly is divided into functionally independent components: a knee hinge assembly defining a knee axis, a locking hinge assembly defining a locking axis, and a post linking them. This segmentation allows each component to perform its specific function (knee flexion/extension, locking/unlocking) independently, achieving complex gait control through simple, modular elements rather than a single complex mechanism.
Solution Approach 2:
The design employs simple, passive mechanical components without expensive motors, sensors, or electronic control systems. The locking mechanism uses basic hinge assemblies and geometric interference rather than complex actuation systems, making the device suitable for low-cost manufacturing and deployment in resource-constrained settings while maintaining functional effectiveness.
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
Enables able-bodied kinematics with minimal metabolic energy expenditure, reduces catastrophic failure risk, and meets socio-economic needs by being low-cost and energy-independent, making it suitable for transfemoral amputees in developing countries.
Implementation Method 1
A spring between the head plate and the linking member biases rotation of the linking member about the early-stance flexion axis to thereby direct the knee hinge and the first end of the post toward the head plate
Implementation Method 2
a ground reaction force applied to the artificial knee posterior to the locking axis causes an interfering relation at a point between the locking hinge assembly and the knee hinge assembly during heel strike and early-stance gait phases of an individual wearing the artificial knee, whereby rotation of the knee hinge causes radial compression of the knee hinge assembly at the point of interfering relation, thereby locking rotation of the post about the knee axis
Implementation Method 3
shifting of the ground reaction force anterior to the locking axis during a mid-stance gait phase of the individual causes rotation of the post about the locking axis, thereby unlocking rotation of the post about the knee axis
Data Source
AI summary
A passive artificial knee includes a knee hinge assembly defining a knee axis, a locking hinge assembly defining a locking axis, and a post linking the knee hinge assembly and the locking hinge assembly. A ground reaction force applied to the artificial knee posterior to the locking axis causes an interfering relation by compression of the locking hinge assembly and the knee hinge assembly during heel strike at early-stance gait phase of an individual wearing the artificial knee, thereby locking rotation of the post about the knee axis. Shifting of ground reaction force anterior to the locking axis during a mid-stance to late-stance gait phase of the individual causes rotation of the post about the locking axis, thereby unlocking rotation of the post about the knee axis and enabling flexion and subsequent swing phase extension of the passive artificial knee joint. The artificial knee is a passive joint that can be fabricated and maintained at low expense.