Multi-Key Force Sensing With Parasitic Force Compensation
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Solution Overview
Problem
Multi-key devices with force-sensitive resistors (FSR) struggle to accurately determine which keys are pressed, especially when multiple keys are pressed simultaneously, due to parasitic forces from neighboring keys, leading to incorrect activation of unintended keys.
Innovation Solution
A method using a transmission rate matrix to quantify and eliminate parasitic forces between keys, allowing precise determination of the keys actually pressed by the user, involving the calculation of pressing forces applied to each key and accounting for distances between keys to optimize calculations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If force sensors are used to detect key presses in a multi-key device, then the device can detect key activation through force sensing, but parasitic forces from neighboring keys cause incorrect detection of pressed keys
Solution Approach 1:
The patent measures the parasitic forces transmitted between keys and uses this information beneficially to compensate for the interference. By characterizing the mechanical coupling between keys through transmission rate values, the system converts the harmful parasitic forces into useful data that enables accurate key detection through compensation algorithms.
Solution Approach 2:
The patent introduces transmission rate values as an intermediary parameter that mediates between the raw force sensor readings and the actual key press detection. These transmission rate values characterize the mechanical coupling between keys and serve as a compensation factor to eliminate the influence of parasitic forces on detection accuracy.
2Productivity
If simple force threshold comparison is used to detect key presses, then the detection algorithm is simple and fast, but it cannot distinguish between direct key presses and forces transmitted from neighboring keys
Solution Approach 1:
The patent performs preliminary characterization of the mechanical coupling between keys by measuring and storing transmission rate values before actual key press detection. This pre-established data enables the system to quickly compensate for parasitic forces during real-time operation without adding complex calculations to the detection process itself.
Solution Approach 2:
The patent replaces the simple mechanical threshold comparison with a compensated detection algorithm that uses transmission rate values to account for mechanical coupling between keys. This substitution maintains real-time performance while significantly improving detection accuracy by eliminating false positives from parasitic forces.
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 method effectively identifies the correct keys pressed by the user, even when multiple keys are activated simultaneously, reducing errors caused by parasitic forces and improving the accuracy of key detection.
Implementation Method 1
force sensors having a resistance sensitive to an applied force (FSR, in English Force Sensitive Resistor)
Data Source
Figure 1~2(a)
Figure 2(b)~2(c)
Figure 3
AI summary
The invention relates to a method for determining whether at least one key of a device having multiple keys has been actuated. The device having multiple keys includes a plurality of keys (K1 to Kn) and a plurality of force sensors (C1 to Cn), each force sensor (C1 to Cn) being associated with a key (K1 to Kn), respectively, and capable of supplying a value representing a force which is applied thereto. The method is characterized in that it includes the steps of: obtaining the values (F'1 to F'n ) representing the force applied to each of the force sensors (C1 to Cn); outputting values of the rate of transmission of a bearing force among the keys; suppressing the contribution of each of the force values (F'1 to F'n ) from the bearing force transmitted among the keys using the output rate of transmission values; and determining values (F1 to Fn) representing the bearing force which was applied by the user to the keys (K1 to Kn).