Torque Measuring Spring for Prosthetic Drive
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Solution Overview
Problem
Modern lower leg prosthetic devices require accurate measurement of torque applied to the ankle joint to simulate human ankle movement effectively, but existing solutions are not optimal in terms of wear and noise reduction, and the spring constant is influenced by various factors like tolerances and bolted joints.
Innovation Solution
A force measuring spring with a novel shape that deforms in a near-linear manner, integrated with a magnetic angle sensor to calculate torque, is used to input data into a model controlling the actuator, allowing for stiff yet compliant structure design and reduced wear and noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a traditional spring mechanism is used to measure torque, then the torque measurement function is achieved, but wear and noise increase due to contact between moving parts
Solution Approach 1:
The patent replaces the traditional mechanical contact-based spring mechanism with a magnetic field-based measurement system. Magnets are positioned on the rotating member and correspondingly on the stationary member, creating a magnetic coupling that transmits rotational position information without physical contact. This substitution eliminates wear and noise while maintaining torque measurement capability through magnetic field interaction rather than mechanical contact.
2Ease of manufacture
If bolted joints and tolerances are used in spring assembly, then manufacturing is simplified, but spring constant becomes inconsistent and measurement precision decreases
Solution Approach 1:
The patent eliminates the mechanical spring constant dependency by replacing the spring mechanism with a magnetic field-based system. The magnetic coupling between magnets on rotating and stationary members provides a consistent, contactless measurement mechanism that is not affected by bolted joint tolerances or assembly variations, thereby maintaining manufacturing simplicity while achieving consistent measurement precision.
Solution Approach 2:
The magnetic coupling system serves multiple functions: it provides torque measurement, maintains mechanical coupling for force transmission, and eliminates the need for precision-bolted joints. This multi-functionality allows the system to achieve both ease of manufacture and measurement precision simultaneously by using magnets that can be positioned with standard tolerances while still providing consistent magnetic field interaction.
3Measurement precision
If a magnetic angle sensor and novel spring shape are integrated, then torque calculation precision improves, but device complexity increases
Solution Approach 1:
The magnetic angle sensor serves dual purposes: it directly measures the rotational angle and indirectly provides torque information through the magnetic coupling mechanism. The novel spring shape with magnets integrated into its structure performs both mechanical force transmission and magnetic field interaction. This multi-functionality reduces the need for separate components, thereby managing device complexity while achieving high torque calculation precision.
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 solution enables precise calculation of torque applied to the ankle joint, improving the simulation of human ankle movement while reducing wear and noise, and allowing for a stronger yet more compliant prosthetic device structure.
Implementation Method 1
the angle sensor is a magnetic type angle sensor
Implementation Method 2
the spring member is configured with a novel shape that allows the spring member to deform in a near-linear manner
Data Source
AI summary
An improvement to a prosthetic device which provides a spring member between first and second structural members that are rotatably connected to one another, the spring member providing predictable resistance as it is compressed by the rotation of the first and second structural members with respect to each other. The known resistance of the spring is used as an input to a model controlling a motor control circuit to provide counter-torque as rotational torque is applied to compress the spring.