Stylus Position Calculation Using Even-Odd Centroid Weighting
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Solution Overview
Problem
Touch sensor panels face challenges in accurately calculating the position of a stylus due to stylus tip wobble, which is caused by non-ideal signal coupling and algorithmic errors, leading to discrepancies between actual and calculated positions.
Innovation Solution
An algorithm that calculates a first position estimate using an even-point centroid and a second position estimate using an odd-point centroid, with weighting based on the ratios of amplitude signals, is employed to determine the stylus position, potentially utilizing a look-up table (LUT) for correction and combining these estimates to reduce wobble.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single position calculation method is used, then the calculation is simple, but the positional accuracy is poor due to stylus tip wobble
Solution Approach 1:
The position calculation is segmented into two distinct methods: even-point centroid calculation and odd-point centroid calculation. Each method processes signal contributions from electrodes in a specific pattern, and the final position is determined by combining results from both segmentation approaches, thereby reducing stylus tip wobble while maintaining computational feasibility
Solution Approach 2:
The patent merges two separate position estimation results (even-point centroid and odd-point centroid) into a single final position estimate. By combining the strengths of both calculation methods through weighted averaging, the system achieves higher positional accuracy and reduces wobble artifacts that would be present if only a single method were used
2Reliability
If weighted combination of position estimates is used, then the wobble is reduced, but the computational complexity increases
Solution Approach 1:
The system performs preliminary calculations of both even-point and odd-point centroids before combining them. By pre-computing these separate estimates and their associated weights based on signal amplitudes, the algorithm prepares refined position data in advance, which then can be combined to produce the final reliable position estimate with reduced wobble
Solution Approach 2:
The patent dynamically adjusts the weighting parameters applied to each centroid estimate based on the relative signal amplitudes from different electrodes. By changing these weight parameters adaptively rather than using fixed weights, the system optimizes the combination of position estimates to minimize wobble while managing computational complexity through parameter optimization
Data Source
AI summary
Algorithms can be used to reduce stylus tip wobble for a stylus translating on a surface over and between electrodes of a touch sensor panel. In some examples, a first position estimate can be calculated using a first position calculation method and a second position estimate can be calculated using a second position calculation method. The position of the stylus can be determined based on a weighted combination of the first and second position estimates. In some examples, the first position estimate can be calculated using an even-point centroid of signal contributions from an even number of electrodes of a touch sensor panel and the second position estimate can be calculated using an odd-point centroid of signal contributions from an odd number of electrodes. In some examples, the weighting can be assigned based on a ratio of the two largest amplitude signals and based on a ratio of the second and third largest amplitude signals.