Compliant Arm Torque Sensing for Prosthetic Joint Stability
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Solution Overview
Problem
Existing prosthetic joint actuation mechanisms face issues with instability, weight, and limited sensor options, particularly in torque measurement, leading to undesirable movements and discomfort for users.
Innovation Solution
A torque sensing transmission assembly for prosthetic joints that includes a base, first and second rigid arms, and a sensor to measure the deflection of the second arm, allowing accurate torque determination and controlled rotational movement, enhancing stability and comfort while reducing weight.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a traditional torque measurement system is used in prosthetic joints, then torque measurement capability is provided, but the joint mechanism becomes unstable and heavier
Solution Approach 1:
The torque sensing function is separated from the structural support function by using a compliant second arm that can deflect independently to indicate torque while the first arm provides stable structural support. This segmentation allows the measurement function without compromising joint stability.
Solution Approach 2:
The second arm is designed with specific compliance characteristics (flexibility) to allow controlled deflection under torque loads. By changing the mechanical parameter of the second arm from rigid to compliant, the system enables torque sensing while maintaining overall joint stability through the rigid first arm.
2Measurement precision
If a traditional torque sensing mechanism is implemented, then torque measurement is achieved, but the device weight increases
Solution Approach 1:
The compliant second arm serves multiple functions: it acts as a structural support element, a torque sensor, and a movement indicator. This multi-functionality eliminates the need for separate torque measurement components, thereby reducing overall device weight while maintaining sensing capability.
Solution Approach 2:
By changing the material or cross-sectional properties of the second arm to be compliant rather than rigid, the system enables torque measurement through deflection without adding heavy sensor components. The compliance itself becomes the sensing mechanism, reducing weight compared to traditional rigid sensor installations.
3Stability of the object's composition
If rigid arms are used for structural support, then stability is improved, but torque measurement capability is reduced
Solution Approach 1:
The mechanical arm is segmented into two distinct parts with different properties: the first arm is rigid for structural stability, while the second arm is compliant for torque measurement. This segmentation allows each part to optimize its function without interfering with the other.
Solution Approach 2:
Different parts of the mechanical arm have different mechanical qualities - the first arm is rigid where structural stability is needed, while the second arm is compliant where torque measurement is required. This local differentiation of material or structural properties enables both stability and measurement capability simultaneously.
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 assembly provides stable and controlled rotational movement, improves torque measurement accuracy, and allows for a variety of sensors, resulting in enhanced user comfort and reduced device weight.
Implementation Method 1
the second arm may deflect to a second amount that is greater than the first amount
Data Source
AI summary
A prosthetic joint device may include a base coupled to an actuator of the joint mechanism. The device may include a first arm and a second arm extending from the base with a gap between the first arm and the second arm. The first arm and the second arm may form a closed loop. Distal ends of the first arm and the second arm may be coupled together at a distal connection point. A distal attachment portion including an opening may be rotatably coupled to a shank portion of the prosthetic device. The device may include a sensor to measure rotation of the distal attachment portion relative to the shank portion when the torque is applied to the base.