Force Detection in Two-Finger Touch Using Expected Deflection Models
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Solution Overview
Problem
Existing input devices face challenges in accurately determining which of multiple input objects is applying the largest force to a surface, especially when the spacing between force sensors is wide and the surface deforms globally rather than locally, making it difficult to distinguish between input objects.
Innovation Solution
The solution involves measuring deflections at existing force sensor locations, calculating expected deflections using a model, and comparing measured deflections with expected deflections to determine which input object is applying the force with the smallest deviation, thereby identifying the input object with the largest force.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the spacing between force sensors is increased, then the device complexity is reduced, but the measurement precision deteriorates because it becomes difficult to distinguish which input object is applying the largest force
Solution Approach 1:
The patent introduces a computational model as an intermediary between the force sensors and the determination of which input object is applying the largest force. The model calculates expected deflection patterns for each possible input object location and compares them with actual sensor readings, enabling accurate force attribution even with widely spaced sensors.
Solution Approach 2:
The patent creates a virtual copy of the physical system through a computational model that simulates deflection patterns. This model copy allows the system to predict and compare deflection scenarios without requiring dense physical sensor coverage, thereby maintaining measurement precision while reducing device complexity.
2Measurement precision
If the surface is made more flexible to improve force sensing, then the force detection capability is improved, but the reliability deteriorates because the surface deforms globally rather than locally, making it difficult to distinguish between input objects
Solution Approach 1:
The patent implements a feedback mechanism where the computational model uses actual force sensor readings to determine which input object is applying the largest force. The system continuously compares expected deflection patterns with actual measurements and uses this feedback to reliably identify the active input object, even when global deformation occurs.
Solution Approach 2:
The patent changes the approach from directly measuring local deformation to analyzing the pattern of force distribution across multiple sensors. By examining the relative force values and their spatial distribution, the system can distinguish between different input object locations and identify which one is applying the largest force, maintaining reliability despite global surface deformation.
Data Source
AI summary
A processing system for a force sensing device, including: sensor circuitry that receives resulting signals from force sensors; and processing circuitry that: determines a first location of a first input object and a second location of a second input object on a surface; determines force values for the force sensors based on the resulting signals; obtains a first plurality of expected force values for the force sensors based on the first location and a second plurality of expected force values for the force sensors based on the second location; executes a first comparison of the first plurality of expected force values to the force values; executes a second comparison of the second plurality of expected force values to the force values; and determines, based on the first comparison and the second comparison, that the first input object is applying an input force to the surface.