Dual Loop Strain Gauge Architecture for Non-Uniform Force Sensing
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Solution Overview
Problem
Existing force sensors are less accurate and cumbersome when sensing forces applied by amorphous objects or non-uniformly over large areas, and they often require significant redesign to be compatible with electronic devices.
Innovation Solution
The use of single or dual loop strain gauge architectures, which include strain-sensitive resistors formed on or attached to a substrate, to sense force distributions on electronic devices, with supplementary loops for temperature compensation and enhanced signal-to-noise ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional load cells are used to sense force, then force measurement capability is provided, but measurement precision deteriorates when sensing non-uniform force distributions
Solution Approach 1:
The force sensing area is divided into multiple discrete sensing elements (strain gauges) arranged in a grid pattern. Each strain gauge measures local strain at its specific position, and the combined readings from multiple segmented sensors provide accurate measurement of non-uniform force distributions that a single load cell cannot capture.
Solution Approach 2:
The patent replaces the mechanical load cell system with an electrical strain gauge measurement system. Strain gauges bonded to the substrate convert mechanical strain into electrical resistance changes, which are then measured and processed to determine force distribution, providing better adaptability to non-uniform loading conditions.
2Ease of operation
If load cells are integrated into electronic devices, then force sensing is enabled, but device complexity increases due to required redesign
Solution Approach 1:
The substrate serves multiple functions: it is both the structural component of the electronic device and the mounting surface for the strain gauge sensor array. This multi-functionality eliminates the need for separate force sensing components, reducing device complexity and simplifying integration while maintaining ease of operation.
Solution Approach 2:
The force sensing functionality is merged directly into the device substrate by bonding strain gauges to it. This combination integrates the sensor with the structural element, eliminating the need for separate load cell assemblies and reducing overall device complexity while enabling straightforward integration.
3Adaptability or versatility
If strain gauges are used to sense force, then compatibility with electronic devices is improved, but reliability deteriorates due to temperature sensitivity
Solution Approach 1:
Temperature compensation is achieved by placing compensation strain gauges in locations on the substrate that experience the same temperature variations but not the mechanical strain. These compensation sensors have the same thermal characteristics as the active sensors, allowing local temperature effects to be measured and subtracted from the force measurements, thereby maintaining reliability under thermal gradients.
Solution Approach 2:
The compensation strain gauges act as intermediaries that measure temperature effects separately. By using these intermediary sensors to capture thermal expansion or contraction of the substrate, the system can distinguish between temperature-induced strain and force-induced strain, maintaining reliable force measurements despite temperature variations.
Data Source
AI summary
Dual loop strain gauge architectures (or other multiple loop strain gauge architectures) are used to sense an amount of force applied to an electronic device. The force may be applied by a transverse, uneven pressure field, such as a force that is applied by an amorphous object and/or a force that is applied non-uniformly, over a large area and/or to multiple points or areas. In some embodiments, a dual loop (or other multiple loop) strain gauge architecture is used to sense a pressure distribution on an electronic device. In some embodiments, a single loop strain gauge architecture is used to sense an amount of force applied to an electronic device.