Resistive Force Sensor Compensation for Thermal False Detection

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Solution Overview

Problem

Force sensors in electronic devices are susceptible to thermal effects, leading to reduced sensitivity and potential false detection of user inputs due to changes in resistance values and temperature gradients, which can degrade user experience and device performance.

Innovation Solution

The implementation of compensation circuitry that monitors electrical parameters of resistive force sensors to determine absolute resistance values and apply compensation factors, adjusting operational parameters such as gain, time constant, and signal validity thresholds to differentiate between valid user inputs and thermal effects, thereby enhancing the accuracy of force sensor outputs.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Volume of moving object

If force sensors are used to replace mechanical switches, then device size is reduced and durability is improved, but thermal sensitivity causes false detection and reduced measurement precision

Engineering Contradiction:

Improvedevice sizeVSAvoidforce detection accuracy

Core Design Contradiction:

Volume of moving objectVSMeasurement precision

Solution Approach 1:

The system dynamically adjusts operational parameters including gain, time constant, and threshold values based on real-time temperature measurements. When temperature changes are detected, the processing circuitry modifies these parameters to compensate for thermal effects on the force sensor's resistance, thereby maintaining measurement precision across varying temperature conditions

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The system implements a feedback mechanism where temperature is continuously monitored and used to adjust force sensor operational parameters. The temperature sensor provides feedback about thermal conditions, and the processing circuitry uses this information to dynamically modify gain and threshold settings, creating a closed-loop system that maintains detection accuracy despite thermal variations

Inventive Principle:

Principle #23Feedback

2Adaptability or versatility

If force sensors operate in varying temperature conditions, then device adaptability is improved, but thermal effects cause resistance changes leading to false positives

Engineering Contradiction:

Improvetemperature environment toleranceVSAvoiduser input detection reliability

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The system changes operational parameters dynamically in response to temperature variations. The processing circuitry adjusts gain, time constant, and threshold values based on real-time temperature data, allowing the force sensor to maintain reliable operation across different temperature environments without producing false positives

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The system introduces temperature monitoring as an intermediary measurement to mediate between the force sensor and the detection logic. By measuring temperature separately and using it to adjust operational parameters, the system creates an intermediate control layer that prevents thermal effects from directly causing false input detection

Inventive Principle:

Principle #24Intermediary (Mediator)

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 solution effectively compensates for thermal effects, maintaining consistent sensitivity and reducing false positives in user input detection, ensuring reliable performance of force sensors in varying temperature conditions.

Implementation Method 1

a force sensor, particularly a resistive force sensor, in use generates an output signal that varies in response to a change in temperature

Methodology Applied

Scientific EffectPiezoresistive effect: Piezoresistive Effect

Implementation Method 2

the sensitivity of the force sensor changes with a change in temperature, and/or a thermal gradient across the force sensor causes an output signal to be generated

Methodology Applied

Scientific EffectThermal effect: Thermal Expansion

Data Source

PatentUS11913846B2Force sensing systems

Publication Date: 2024.02.27 CIRRUS LOGIC INC

AI summary

Compensation circuitry for compensating for a thermal effect in an output signal output by a force sensor may comprise monitoring circuitry configured to monitor one or more electrical parameters of the resistive force sensor and processing circuitry. The processing circuitry is configured to determine an absolute resistance value for the force sensor based on the one or more monitored electrical parameters and to adjust one or more operational parameters of the force sensor system based at least in part on the determined absolute resistance value.