Indentation Force Control Using a Non-Linear Spring
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Solution Overview
Problem
Conventional measuring apparatuses using springs for material characterization are bulky and lack precision in controlling force over a broad range, with softer springs required for soft materials and harder springs for hard materials, leading to design constraints and safety issues.
Innovation Solution
A measuring apparatus employing a non-linear spring configuration, where the spring constant increases with deformation, and a controller modulates the actuator to achieve target loads, using serially or parallelly coupled linear springs with limiters to manage deformation and load distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a softer spring is used to improve load control accuracy and follow work piece deformation, then the measuring apparatus becomes bulky and the energy stored in the spring increases
Solution Approach 1:
The patent employs a non-linear spring whose stiffness dynamically changes with deformation amount. The spring is soft when deformed little (for accurate initial contact and low load) and becomes hard when deformed much (for compactness and safety). This dynamic stiffness adjustment resolves the contradiction between requiring soft spring characteristics for measurement precision and avoiding the bulky size associated with permanently soft springs.
2Measurement precision
If a softer spring is used to detect weak contact forces, then the spring stroke increases and the risk of work piece or stage shattering increases
Solution Approach 1:
The non-linear spring provides high sensitivity for detecting weak contact forces when deformation is small, while simultaneously limiting the maximum stroke and stored energy through its hardening characteristic at large deformations. This dynamic behavior allows the spring to be soft enough for sensitive detection yet compact enough to prevent catastrophic failure from excessive energy storage.
3Measurement precision
If different springs are selected for different materials and purposes, then measurement accuracy improves, but device complexity and the need for multiple measuring apparatuses increases
Solution Approach 1:
The non-linear spring provides universal functionality by combining the characteristics of both soft and hard springs within a single component. It can accurately measure both soft materials (requiring soft spring characteristics) and hard materials (requiring hard spring characteristics) with the same apparatus, eliminating the need for multiple specialized measuring devices and reducing overall system complexity.
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 precise control of force over a broad range with high accuracy while maintaining compactness, allowing for diverse material measurements with improved safety and reduced design constraints.
Implementation Method 1
a non-linear spring in which a spring constant increases as an amount of deformation increases, and the deformation generates a load that presses the indenter against the material surface
Data Source
AI summary
Utilizing a load generated by a non-linear spring, a spring constant of which increases as an amount of deformation increases, a measuring apparatus presses an indenter against a material surface and evaluates material characteristics. The measuring apparatus includes: an actuator that causes the non-linear spring to deform; a scale that measures the amount of deformation of the non-linear spring when the non-linear spring is deformed; and a controller that stores non-linear spring characteristic data for reciprocally calculating the amount of deformation and the load, and that drives the actuator based on the amount of deformation and the non-linear spring characteristic data such that the load reaches a target load.