Variable-Rigidity Elastic Body for Wide-Range Torque Sensing
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Solution Overview
Problem
Existing series elastic actuators face challenges in precisely measuring torque with low-resolution sensors without causing permanent deformation or damage, especially in high-torque applications, due to the need for high-resolution sensors and the limitations of low-stiffness springs.
Innovation Solution
A variable-stiffness elastic body with a link portion and a spring portion that changes stiffness based on torque, featuring a deformable portion with alternating first and second elastic portions, allowing for self-contact and adjustable elastic moduli to vary stiffness in response to torque levels, enabling precise measurement in low-torque regions while preventing damage in high-torque regions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a low-stiffness spring is used to achieve large displacement for precise measurement with low-resolution sensors, then measurement precision is improved, but the spring is highly likely to be permanently deformed or damaged when high torque is applied
Solution Approach 1:
The spring portion is designed with a deformable section that dynamically changes its stiffness characteristic based on the applied torque. When torque is low, the spring exhibits high compliance for large displacement and precise measurement. When torque increases, the spring transitions to a higher stiffness state through self-contact, preventing permanent deformation and damage.
Solution Approach 2:
The spring's stiffness parameter is changed from a fixed value to a variable value that depends on the applied torque. This is achieved by designing the spring geometry such that the deformable portion makes contact with itself at different deformation stages, effectively changing the spring's mechanical properties during operation.
2Measurement precision
If a high-resolution sensor is used to measure small spring displacement for precise torque measurement, then measurement precision is improved, but costs increase and applicability is limited
Solution Approach 1:
Instead of using a high-resolution sensor to measure small displacements, the invention changes the spring's stiffness parameter to produce large displacements even with low torque. This allows standard low-resolution sensors to achieve precise torque measurement without increasing device complexity or cost.
3Length of moving object
If the spring portion is designed to be flexible for large displacement, then measurement range is improved, but the spring becomes vulnerable to damage under high torque
Solution Approach 1:
The spring transitions from a flexible state with large displacement capability to a stiff state with high damage resistance based on the applied load. The deformable portion's self-contact mechanism dynamically adjusts the spring's mechanical properties to match the operational requirements at different torque levels.
Solution Approach 2:
Different portions of the spring have different structural characteristics. The deformable portion is designed with specific geometry to make contact with itself, creating a local structural change that affects the overall spring behavior. This local quality change enables the spring to exhibit both flexibility and strength as needed.
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 variable-stiffness elastic body increases torque resolution and measurement range by altering stiffness in response to torque levels, allowing for sensitive action and safe operation in robotic applications.
Implementation Method 1
the spring portion being integrally formed with the link portion, the spring portion having stiffness that varies due to contact with the link portion when deformed by torque applied thereto
Data Source
AI summary
Proposed is an elastic body having variable rigidity, wherein the elastic body is used in a series elastic actuator module, connects an input and an output, and has a rigidity that varies according to the applied torque. The elastic body having variable rigidity comprises: a connection part which receives torque from the input side or the output side; and a spring part connected to and receiving torque from the one selected from among the input side and the output side which is different from the connection part, wherein the spring part is formed integrally with the connection part and has a rigidity that varies as the connection part and the spring part come into contact with each other due to deformation caused by the applied torque.