Force Sensor Calibration via Optimized Resistance Curve
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Solution Overview
Problem
Force sensing devices in electronic devices, such as touch screens, experience significant errors in force calculation due to variations in design, actuator integration, and material factors, leading to increased error margins, especially with preload and force transfer inefficiencies.
Innovation Solution
A method and apparatus for calibrating force sensing devices by establishing an optimized force-resistance curve through mean resistance calculation, applying calibration points, and adapting the curve using interpolation techniques like Piecewise Cubic Hermite Interpolating Polynomial (PCHIP) to determine multiplier values, thereby reducing force errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If force sensing devices are integrated into electronic devices with preload and multiple materials, then the device becomes more functional and integrated, but the force measurement precision deteriorates due to increased error margins
Solution Approach 1:
The patent applies parameter changes by establishing an optimized force-resistance curve that transforms the relationship between force and resistance measurements. The calibration process determines multiplier values for different force levels, effectively changing the measurement parameters to compensate for integration-induced errors. This allows the device to maintain functional integration while correcting measurement precision through mathematical transformation of the force-resistance relationship.
2Stability of the object's composition
If preload is applied to the force sensing device during integration, then the device structure is stabilized, but the force error increases significantly from 10% to 50%
Solution Approach 1:
The patent implements preliminary action by performing calibration before actual force measurements are taken. The optimized force-resistance curve is established in advance, and multiplier values are determined beforehand to compensate for the effects of preload. This preliminary calibration action allows the system to maintain structural stability with preload while correcting the resulting measurement errors through pre-computed compensation factors.
3Ease of manufacture
If force transfer through the electronic device is reduced due to material losses, then the device design becomes more flexible, but the force measurement accuracy deteriorates
Solution Approach 1:
The patent applies feedback by using the measured resistance values and the optimized force-resistance curve to determine actual force measurements. The system continuously references the pre-established curve and calculated multiplier values to compensate for force transfer losses. This feedback mechanism allows flexible device design while maintaining measurement accuracy by constantly comparing and adjusting measurements against the calibrated reference.
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 calibration method significantly reduces force errors from triple-digit percentages to single-digit percentages, ensuring more accurate force measurement and consistent user input responses, even with variable preloads and force transfer inefficiencies.
Implementation Method 1
a pressure sensitive layer between said first conductive layer and said second conductive layer
Data Source
AI summary
A method of calibrating a force sensing device comprises establishing an optimized force-resistance curve by obtaining a mean resistance of a plurality of force-resistance curves for a set of substantially similar force sensing devices and measuring calibration data of the force sensing device. The method applies a plurality of calibration points defined from the measuring step to the optimized force-resistance curve and adapts the optimized force-resistance curve to form an adapted force-resistance curve by interpolating the plurality of calibration points and determining a multiplier value for each calibration point.