Full-bridge Strain-gauge Array for Thermal Drift Compensation
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Solution Overview
Problem
Existing input devices, such as touchpads and touch screens, face challenges in accurately detecting multi-point forces due to thermal drift, which interferes with the measurement of applied forces, leading to reduced accuracy in user input detection.
Innovation Solution
A force sensor system utilizing a full-bridge configuration of piezo-resistive electrodes with two types of resistors, where one type responds only to thermal drift and the other type responds to both thermal drift and applied force, allowing for differential sensing to isolate and magnify the force response, thereby eliminating thermal drift and enhancing force detection accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single-type resistor array is used for force sensing, then the device structure is simple, but thermal drift interferes with force measurement accuracy
Solution Approach 1:
The sensor array is segmented into two distinct resistor types: first resistor types that respond only to thermal drift, and second resistor types that respond to both thermal drift and applied force. This segmentation allows differential measurement where thermal responses are canceled out, isolating the force component and improving measurement precision without excessive complexity
Solution Approach 2:
The patent changes the thermal response parameter characteristics by using resistors with different thermal sensitivities. First resistor types are designed with minimal thermal response while second resistor types have significant thermal response. This parameter differentiation enables the processing system to subtract thermal drift from the combined signal, extracting accurate force measurements
2Measurement precision
If thermal drift compensation is implemented, then force measurement accuracy improves, but device complexity increases
Solution Approach 1:
The array is divided into first and second resistor types with distinct functional roles. First resistors provide thermal reference signals while second resistors provide combined thermal and force signals. This functional segmentation enables automated thermal compensation through signal processing, achieving high accuracy without complex mechanical compensation mechanisms
Solution Approach 2:
The processing system uses feedback by continuously comparing signals from first and second resistor types. The thermal response measured from first resistors is fed back and subtracted from the combined signals of second resistors, creating a compensated force measurement. This automated feedback loop maintains high accuracy while keeping the physical structure relatively simple
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 enables true multi-point force detection with improved accuracy by canceling out thermal responses, allowing for precise measurement of applied forces, thus enhancing the usability and reliability of input devices.
Implementation Method 1
A force sensor system utilizing a full-bridge configuration of piezo-resistive electrodes
Data Source
AI summary
A force sensor having a strain gauge array including force sensing electrodes arranged in a full-bridge configuration comprising at least two of a first resistor type and at least two of a second resistor type, wherein the at least two of the first resistor type form a first force sensing node and the at least two of the second resistor type form a second force sensing node, a processing system communicatively coupled to the force sensing electrodes, the processing system being configured to receive a first signal from the first force sensing node and a second signal from the second force sensing node, wherein the first signal includes a thermal response, and the second signal includes the thermal response and an applied force, and remove the thermal response by comparing the first and second signals to obtain the applied force.