Triaxial Force Sensor Bridge Circuit Design
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Solution Overview
Problem
Conventional triaxial force sensors require a large number of strain sensitive elements, leading to increased costs and size limitations, particularly when miniaturization is needed for applications like robot hands, and they often suffer from disconnection issues due to fatigue failure at joints.
Innovation Solution
A triaxial force sensor design that uses a bridge circuit combining X-axial and Y-axial bridge circuits to detect forces in the Z-axial direction without additional strain sensitive elements, reducing the number of components and enhancing reliability by positioning joints to avoid stress-induced disconnection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple strain sensitive elements are arranged on the surface of the strain causing plate to detect forces in X, Y and Z directions, then the detection capability is improved, but the number of components increases causing cost increase and size enlargement
Solution Approach 1:
The patent makes strain sensitive elements serve multiple functions by arranging them to detect forces in both X and Z directions simultaneously. The same strain sensitive elements that detect X-direction forces also contribute to Z-direction force detection when combined with specific bridge circuit configurations, eliminating the need for separate dedicated elements for each direction.
Solution Approach 2:
The patent combines the detection functions for X-direction and Z-direction forces into a single bridge circuit system. By merging the signal processing paths and using common strain sensitive elements for both detection purposes, the system reduces the total number of required components while maintaining full triaxial detection capability.
2Measurement precision
If sixteen strain sensitive elements are used to detect forces in all three directions, then the detection accuracy is improved, but the sensor size increases preventing miniaturization for applications like robot fingertips
Solution Approach 1:
Each strain sensitive element is designed to serve multiple detection purposes. The elements are positioned and configured so that they respond to stresses from both X-direction and Z-direction forces, allowing a reduced number of elements to provide comprehensive triaxial detection coverage that would otherwise require sixteen separate elements.
Solution Approach 2:
The patent changes the operational parameters of the strain sensitive elements by modifying their arrangement pattern and the bridge circuit configuration. This allows the same physical elements to operate in multiple detection modes, effectively reducing the total element count needed while maintaining detection accuracy across all three spatial directions.
3Device complexity
If strain sensitive elements are arranged in a conventional configuration, then the structural simplicity is maintained, but joints are subjected to tension-compression stress causing fatigue failure and disconnection
Solution Approach 1:
The patent inverts the conventional joint arrangement by positioning joints away from the high-stress regions and relocating them to areas experiencing minimal tension-compression cycling. This reverse positioning strategy prevents fatigue failure at connection points while maintaining the overall structural simplicity of the sensor design.
Solution Approach 2:
The patent applies different structural qualities to different regions of the sensor. Joints are specifically positioned in low-stress zones where they experience minimal mechanical loading, while the strain sensitive elements are placed in high-stress zones where they need to detect force. This localized optimization protects joints from fatigue failure without complicating the overall structure.
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 achieves cost and size reduction by using fewer strain sensitive elements and improves reliability by minimizing stress on joints, enabling effective force detection in all three axial directions within a compact form factor suitable for small-scale applications.
Implementation Method 1
multiple strain sensitive elements arranged on the other surface of a strain causing plate for detecting forces acting on the load action element in the X, Y and Z-axial directions
Implementation Method 2
strain sensors arranged on the surfaces of an upward arm, a right-pointing arm, a downward arm and a left-pointing arm, which form the cross part, respectively; and a signal processing circuit conducts pre-determined arithmetic processing using a strain sensor resistance value
Data Source
AI summary
The detection unit Ud is configured by arranging two strain sensitive elements X1 and X2 respectively at each side of the X-axial direction relative to the center of the strain causing plate 2, and arranging two strain sensitive elements Y1 and Y2 respectively at each side of the Y-axial direction relative to the center of the strain causing plate 2. The signal processing part Um is provided with the X-axial bridge circuit 4 for detecting a force in the X-axial direction by the strain sensitive elements X1 and X2 arranged at the both sides in the X-axial direction, the Y-axial bridge circuit 5 for detecting a force in the Y-axial direction by the strain sensitive elements Y1 and Y2 arranged at both sides in the Y-axial direction, and the Z-axial bridge circuit 6 for detecting a force in the Z-axial direction by a bridge circuit including the X-axial bridge circuit 4 and the Y-axial bridge circuit 5.