Touchpad Force Estimation for Multiple Contacts Using Calibration Weights
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Solution Overview
Problem
Existing force sensing touchpads struggle to accurately determine the forces exerted by multiple contacts, such as fingers, palms, or other body parts, simultaneously contacting the touchpad, leading to challenges in user input recognition and experience, particularly in gaming and accessibility applications.
Innovation Solution
A method involving a predetermined set of calibration weights is used to assign forces to each contact on a touchpad, utilizing a greater number of calibration positions than force sensors, and normalizing measured forces to accurately estimate the force exerted by each contact, with the option to generate force-adjusted weights for refined accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a force sensing touchpad uses multiple force sensors to detect contacts, then it can detect the presence and location of contacts, but it cannot accurately determine the individual forces exerted by multiple simultaneous contacts
Solution Approach 1:
The system performs preliminary calibration by applying known calibration forces at multiple predetermined positions on the touchpad surface. This pre-characterization creates a calibration dataset that maps sensor responses to actual forces at different locations, enabling accurate force determination during actual use without requiring complex real-time calculations
Solution Approach 2:
The touchpad surface is divided into multiple discrete calibration positions where calibration forces are applied individually. Each position is characterized separately, and the system segments the force determination problem by assigning calibration weights to each sensor based on which calibration positions are nearest to the detected contact locations
2Measurement precision
If the touchpad uses a simple force sensing mechanism, then the device complexity is low, but the precision in determining forces from multiple contacts is insufficient
Solution Approach 1:
Instead of using complex physical force sensors at every calibration position, the system creates a virtual model (calibration dataset) that copies the mechanical behavior of the touchpad structure. This computational model allows the system to predict sensor responses to forces at any position without physically instrumenting every location with sensors
Solution Approach 2:
The system changes the parameter representation from direct force measurement to calibrated weight assignment. By transforming the problem into determining calibration weights for each contact based on proximity to calibration positions, the system achieves accurate force estimation using standard sensor technology without requiring specialized high-precision sensors
Data Source
AI summary
Touchpads, computing devices, and methods for estimating a plurality of forces exerted by a plurality of contacts on a touchpad are disclosed. In one example, a method comprises estimating a plurality of forces exerted by a plurality of contacts at a plurality of touch locations on a touchpad. For each contact, a plurality of assigned calibration weights are determined from a predetermined set of calibration weights. The plurality of assigned calibration weights and data from touchpad force sensors are used to determine a force exerted by the contact on the touchpad.