Electronic Pen Sensor Drift Compensation via Moving Average
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Solution Overview
Problem
Inertial measurement systems in electronic pens face errors in velocity and position determination due to minor measurement inaccuracies, leading to significant drift in motion signals, which existing compensation techniques struggle to fully address.
Innovation Solution
The method involves using inertial measurement sensors with a specified coordinate system, moving average processes, high-pass and low-pass filtering, and sensor data transformation to correct for drift and noise, ensuring accurate pen position detection by integrating sensor data along orthogonal axes and accounting for gravitational acceleration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If inertial measurement sensors are used to detect pen movements through integration, then movement detection capability is enabled, but measurement inaccuracies accumulate leading to significant drift in position signals
Solution Approach 1:
The patent applies feedback by continuously monitoring the integrated position signal and comparing it against expected motion patterns. When drift is detected through analysis of velocity and acceleration relationships, the system adjusts the position signal to correct the accumulated errors, creating a closed-loop correction mechanism that maintains accuracy over time.
Solution Approach 2:
The patent changes parameters by dynamically adjusting the integration method based on detected motion characteristics. When stationary or slow motion is detected, the system switches to alternative calculation methods or resets integration accumulators, thereby preventing error accumulation during periods when inertial integration is less reliable.
2Loss of information
If integration of sensor data is performed to obtain position signals, then movement reconstruction is achieved, but errors in velocity and position determination accumulate over time
Solution Approach 1:
The patent implements periodic action by regularly resetting the integration process at detected stationary points or transition moments. Between these periodic resets, integration accumulates motion data, but at predetermined intervals when the pen is stationary, the system clears accumulated errors and re-establishes the integration baseline, preventing indefinite error growth.
Solution Approach 2:
The patent applies preliminary action by detecting stationary conditions and transition points before they cause significant error accumulation. By identifying these critical moments in advance through monitoring acceleration and velocity patterns, the system proactively resets integration accumulators to prevent the buildup of positioning errors.
3Measurement precision
If high-pass and low-pass filtering are applied to sensor data, then noise reduction is achieved, but signal processing complexity increases
Solution Approach 1:
The patent segments the filtering process into distinct high-pass and low-pass stages, each targeting specific frequency ranges. The high-pass filter removes low-frequency drift while the low-pass filter eliminates high-frequency noise, allowing each filter to be optimized for its specific function rather than requiring a single complex filter to handle all frequency ranges simultaneously.
Data Source
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AI summary
The invention concerns a method to detect and evaluate movement patterns and pen positions of an electronic pen with inertial measurement sensors during writing on a two-dimensional writing substrate, comprising: • an initial specification of two axes X, Y, that are orthogonal to each other on the writing substrate, and an axis Z that is perpendicular to the two-dimensional writing substrate, • whereby the X-axis defines the predominant writing direction, as well as a compensation of undesired drift in the pen position signal of the electronic pen to be output, comprising: • a moving average process during a predefined time interval and a predetermined frequency of the pen movements on the writing substrate, determined by the inertial measurement sensors during writing through integration of the sensor data of the measurement sensors, along the two said axes X, Y, that are orthogonal to each other, and a • periodic comparison of currently determined moving average values with initial average values and/or with previously determined moving average values, as well as the • subtraction of deviations, arising during said comparison between currently determined moving average values and initial average values and/or deviations between currently determined moving average values and previously determined moving average values from a pen position signal to be output.