Force Sensor Drift Compensation via Inverse Transfer Function
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Solution Overview
Problem
Force sensing devices in computing devices experience drift due to elastic deformation characteristics of materials, leading to inaccurate force detection and delayed reactions, which diminish the user experience.
Innovation Solution
A method and system that calibrate force sensing devices by determining a system model to approximate a transfer function, applying an inverse transfer function to compensate for drift, and using an inverse filter to generate a reconstructed output signal that accurately reflects the input force.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If force sensing devices use elastomeric materials to detect force, then the device can detect force input, but the elastic deformation characteristics cause drift and inaccurate force detection over time
Solution Approach 1:
The system performs preliminary calibration by applying known test forces to the force sensing device and measuring the output. Based on these measurements, the system pre-calculates correction factors or establishes a transfer function that compensates for the elastomeric material's elastic deformation characteristics. This preliminary action enables the system to predict and correct drift before it affects actual measurements.
Solution Approach 2:
The system continuously monitors the output signal from the force sensing device and compares it against expected values based on the calibrated transfer function. When drift is detected, the system applies real-time corrections using the pre-established model. This feedback mechanism ensures that measurement accuracy is maintained despite the inherent elastic properties of the elastomeric materials.
2Productivity
If the force sensing device uses materials with elastic properties, then the device can function as a force sensor, but the delayed elastic response causes delayed reaction to force input
Solution Approach 1:
The system pre-characterizes the elastic deformation behavior of the elastomeric materials through calibration tests with known force inputs. By establishing the transfer function in advance, the system can compensate for the delayed elastic response in real-time during actual operation, effectively eliminating the lag caused by material properties.
Solution Approach 2:
The system replaces direct reliance on the mechanical elastic response of the elastomeric materials with a computational model (transfer function) that mathematically describes the relationship between input force and output signal. This substitution allows the system to compensate for mechanical delays through software-based correction rather than being constrained by the physical response time of the materials.
3Stability of the object's composition
If the force sensor continues to detect force after force removal due to elastic properties, then the material returns to original state, but this causes drift in the output signal
Solution Approach 1:
The system performs preliminary calibration that includes applying force and then removing it, measuring how the output signal behaves during the recovery phase. This calibration process establishes the transfer function that accounts for the delayed return to nominal position, enabling the system to correct for drift caused by elastic recovery in real-time operations.
Solution Approach 2:
The system continuously monitors the output signal and uses the calibrated transfer function to detect and correct drift caused by elastic recovery. When the force sensor exhibits delayed return to its nominal state, the feedback mechanism applies appropriate corrections based on the pre-established model, maintaining output signal accuracy despite the material's elastic properties.
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 effectively compensates for drift in force sensing devices, providing accurate and timely responses to user inputs, enhancing the user experience by improving the precision and speed of force detection.
Implementation Method 1
due to different elastic deformation characteristics of the materials and/or structures
Data Source
AI summary
Disclosed herein are methods and systems for compensating for drift that may be present in a force sensing device. In some embodiments, the force sensing device may be calibrated to compensate for the drift. The calibration may include receiving an input waveform associated with a received amount of force on the force sensing device. A system model that approximates a transfer function that provides an output waveform associated with the input waveform is then determined. Using the system model, an inverse transfer function associated with the system model is also determined. The inverse transfer function may then be applied to the output waveform which compensates for the drift.