Displacement Sensing with Acceleration Compensation for False Touch Rejection
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Solution Overview
Problem
Existing displacement sensing technologies face challenges in distinguishing between user-induced displacements and inertial effects caused by mechanical perturbations, leading to false positives in touch-sensitive input devices.
Innovation Solution
A sensing apparatus combining displacement and acceleration sensors, where the processing circuitry uses the acceleration sensor output to differentiate between user-input-induced displacements and inertial effects by adjusting the baseline displacement sensor output during periods of significant acceleration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a displacement sensor is used to detect user input by measuring separation distance between a displacement element and a reference element, then touch sensitivity and aesthetic appeal are improved, but false positive detections occur due to inertial effects from mechanical perturbations
Solution Approach 1:
An acceleration sensor is introduced as an intermediary device to detect mechanical perturbations and inertial effects. The acceleration sensor output serves as a mediator to distinguish between genuine user inputs and false positives caused by device movement, thereby improving reliability while maintaining touch sensitivity
Solution Approach 2:
The system implements feedback by continuously monitoring acceleration sensor output and using this information to adjust the interpretation of displacement sensor readings. When acceleration exceeds a threshold, the system adjusts its sensitivity to displacement changes, preventing false positives while maintaining accurate detection of genuine user inputs
2Device complexity
If the reference element is mechanically coupled to the device housing to provide a stable reference, then structural integration is improved, but displacement measurements become inaccurate during device acceleration
Solution Approach 1:
The acceleration sensor acts as an intermediary that compensates for the mechanical coupling between the reference element and housing. By detecting housing acceleration, the system can mathematically compensate for inertial effects on the displacement measurement, maintaining both structural integration and measurement precision
Solution Approach 2:
The system dynamically adjusts the interpretation parameters of displacement measurements based on acceleration sensor output. When acceleration parameters exceed thresholds, the system modifies its detection criteria to account for inertial effects, thereby maintaining measurement precision despite the fixed mechanical coupling
3Speed
If a simple displacement threshold is used to detect user input, then response speed is improved, but discrimination between user input and inertial effects deteriorates
Solution Approach 1:
The system performs preliminary detection using the acceleration sensor to identify periods of mechanical perturbation before evaluating displacement threshold crossings. This preliminary action allows the system to maintain simple, fast threshold-based detection while pre-filtering out periods when inertial effects are likely to cause false positives
Solution Approach 2:
The detection threshold dynamically adjusts based on acceleration sensor output. During periods of high acceleration, the effective threshold for detecting user input increases, preventing false positives while maintaining fast response during normal operation. This dynamic adjustment preserves both response speed and discrimination accuracy
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 effectively reduces false positive detections by compensating for changes in displacement caused by inertial effects, improving the accuracy of user input detection in touch-sensitive devices.
Implementation Method 1
the sensor element comprises a displacement sensor arranged to sense a separation between a frame element and a displacement element movably mounted with respect to the frame element
Implementation Method 2
an acceleration sensor configured to sense an acceleration associated with the frame element
Data Source
AI summary
A sensing apparatus comprising a displacement sensor element arranged to sense a separation between a first element (2) and a second element (3) movably mounted with respect to the first element; an acceleration sensor element configured to sense an acceleration associated with the first element; displacement measurement circuitry (4A) configured to make a measurement indicative of separation on the basis of the sensed separation; acceleration measurement circuitry (4C) configured to make a measurement of acceleration on the basis of the sensed acceleration; and a processing element (4D) configured to output a signal to indicate there is determined to be a change in the separation of the second element relative to the first element on the basis of the measurement indicative of separation and the measurement of acceleration.