Force Input Sensor Calibration via Mechanical Model
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Solution Overview
Problem
Existing force sensors in electronic devices face inaccuracies due to external influences and degradation over time, leading to imprecise interpretations of user input, as the electrical properties of the input-sensitive structures change independently of user input.
Innovation Solution
The implementation of a force-sensitive structure with independent force sensors arranged in a grid or gasket seal, coupled to a substrate, and an input resolver that uses a mechanical model to calibrate and update sensor outputs based on force location and properties, projecting raw data vectors onto calibrated reference vectors to correct for mechanical responsiveness and noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If force sensors are used to measure user input, then force detection capability is provided, but measurement precision deteriorates over time due to degradation and external influences
Solution Approach 1:
The system performs preliminary calibration by applying known test forces to the force-sensitive structure and measuring the actual sensor outputs. These measurements are used to pre-compute calibration factors that compensate for manufacturing variations and initial drift. This preliminary action ensures accurate force measurement from the start of operation.
Solution Approach 2:
The system continuously monitors sensor outputs and compares them against expected values based on the mechanical model. When drift or degradation is detected, the system automatically updates calibration factors using feedback from the sensor measurements. This closed-loop feedback mechanism maintains measurement precision over time despite aging and external influences.
2Measurement precision
If a mechanical model is used to calibrate sensor outputs, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent replaces complex physical calibration mechanisms with a computational mechanical model. Instead of using adjustable mechanical components to compensate for drift, the system uses software-based modeling and calculation to predict sensor behavior and compute calibration factors. This substitution reduces mechanical complexity while maintaining or improving precision.
Solution Approach 2:
The system changes the approach from fixed mechanical calibration to dynamic parameter adjustment. Calibration factors are computed based on measured sensor responses to known forces, and these parameters are updated over time based on observed drift. This allows the system to adapt to changing conditions without adding mechanical complexity.
3Measurement precision
If multiple independent force sensors are arranged in a force-sensitive structure, then force input location identification is improved, but manufacturing precision requirements increase
Solution Approach 1:
The system measures the actual outputs of multiple sensors when known test forces are applied at known locations. Using this feedback data, it computes a mechanical model that captures the actual force distribution and sensor responses. This model compensates for manufacturing variations in sensor placement and ensures accurate location identification despite imperfections in the physical arrangement.
Solution Approach 2:
Instead of requiring precise fixed sensor positions, the system changes to a flexible computational approach where the mechanical model adapts to the actual sensor arrangement. The model parameters are determined from measurements and can accommodate variations in sensor placement, eliminating the need for high manufacturing precision while maintaining accurate location identification.
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 approach enhances the accuracy of force input measurements by mitigating noise and mechanical response variations, ensuring precise force input detection and location identification, even as the mechanical responsiveness of the force-sensitive structure drifts over time.
Implementation Method 1
Some sensors obtain user input by measuring changes in an electrical property of an input-sensitive structure coupled to an external surface of the electronic device. A change in the electrical property corresponds to a change in the user's input. In one example, a change in the resistance exhibited by the input-sensitive structure corresponds to a change in a magnitude of force applied by a user to a display of the electronic device.
Data Source
AI summary
Systems and methods for calibrating a force input device are disclosed. The force input device includes a force-sensitive structure with a number of individual force sensors that compress or expand in response to input. The force input device measures an electrical property of the force sensors of the force-sensitive structure. After the force sensors are measured, the values obtained are adjusted based on a mechanical model of the response of the force sensitive structure. Upon receiving a force input event of high magnitude, the force input device recalibrates the mechanical model.