Force Sensor with Dual Bridge Circuits for Mechanical Trouble Detection
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Solution Overview
Problem
The existing six-axis force-torque sensors face reliability issues due to difficulties in detecting failures in strain gauges, as a failure in one gauge can disrupt the bridge circuit's ability to accurately detect forces, and comparing values across different bridge circuits is challenging.
Innovation Solution
A force sensor design incorporating primary and secondary bridge circuits on opposite faces of a strain element, allowing independent detection of force components in specific directions, with a processor to determine mechanical troubles by comparing outputs from these circuits and switch between them if necessary.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single bridge circuit with strain gauges is used to detect force components, then the device complexity is reduced, but the reliability decreases because failure in one strain gauge causes the entire bridge circuit to fail
Solution Approach 1:
The patent divides the force detection system into multiple independent bridge circuits (first bridge circuit and second bridge circuit) that detect force components in different directions. Each bridge circuit operates independently, so failure in one does not affect the others. This segmentation allows the system to maintain partial functionality even when individual strain gauges fail, thereby improving reliability without excessive complexity increase.
Solution Approach 2:
The patent changes the operational parameters by having different bridge circuits detect force components in different directions (e.g., Fz, Mx, My in one circuit; Fx, Fy, Mz in another). This parameter differentiation allows the system to continue providing useful detection data in unaffected directions even when some strain gauges fail, improving overall system reliability.
2Measurement precision
If multiple bridge circuits are used to detect forces in different directions, then the measurement capability is improved, but the difficulty of detecting and measuring failures increases because it is hard to determine which circuit has failed
Solution Approach 1:
The patent implements a feedback mechanism where the controller continuously monitors the detection results from multiple bridge circuits. When a discrepancy is detected between circuits measuring the same or related force components, the controller identifies potential failures and can switch to using data from reliable circuits. This feedback loop makes failure detection straightforward by comparing consistency across multiple measurement channels.
Solution Approach 2:
The patent designs the system so that multiple bridge circuits can detect overlapping or complementary force components. For example, both circuits may contribute to detecting the same force component through different measurement paths. This multi-functionality allows the system to cross-validate measurements and easily identify failures by comparing results, reducing the difficulty of detecting which circuit has failed.
3Reliability
If strain gauges are disposed on only one face of the strain element, then the manufacturing process is simpler, but the reliability decreases because there is no redundancy for failure detection
Solution Approach 1:
The patent extends the strain gauge arrangement from a single face to multiple opposite faces of the strain element. By disposing strain gauges on both the first face and the second face (opposite to the first face), the system creates spatial redundancy. This dimensional expansion allows independent detection paths that can compensate for failures, improving reliability while maintaining manufacturing simplicity through symmetric placement patterns.
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
This design enhances the reliability of force sensors by enabling early detection of mechanical issues and ensuring continued operation even if one bridge circuit fails, improving accuracy and maintaining functionality.
Implementation Method 1
The strain gauges detect strain in a strain element caused by the force applied to the strain element
Data Source
AI summary
The present invention improves the reliability of a force sensor in terms of mechanical troubles. The force sensor includes: a primary bridge circuit that includes a first strain gauge group disposed on a first main face of a strain element and that is configured to detect a component, in a specific direction, of a force exerted on a strain element; and a secondary bridge circuit that includes a second strain gauge group disposed on a second main face of the strain element and that is configured to detect a component of a force in the same direction as the specific direction.