Gravity-Based Dominant Axis Assignment for Rotational Insensitivity
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Solution Overview
Problem
Portable devices equipped with accelerometers face challenges in maintaining a fixed orientation due to rotational insensitivity, leading to difficulties in accurately measuring motion and user activity.
Innovation Solution
A method is developed to identify a dominant axis based on gravity by creating rolling averages of accelerations over a sample period, detecting cadence of motion, and using gravitational influence logic to assign the dominant axis, which facilitates motion recognition and orientation determination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the accelerometer is used to measure motion in portable devices, then motion detection capability is improved, but rotational insensitivity causes orientation measurement accuracy to deteriorate
Solution Approach 1:
The system performs preliminary action by determining the dominant axis based on gravitational influence before motion measurement begins. The gravitational influence logic identifies the dominant axis during an initial period, and this pre-established orientation information is then used to correctly interpret subsequent motion measurements, resolving the rotational insensitivity issue.
Solution Approach 2:
The system changes parameters by dynamically identifying the dominant axis orientation based on gravitational acceleration components. Instead of assuming a fixed sensor orientation, the system continuously adapts the measurement coordinate system by determining which axis experiences dominant gravitational influence, thereby adjusting the parameter of axis assignment to maintain measurement accuracy regardless of device rotation.
2Measurement precision
If the device orientation is fixed to ensure accurate measurement, then measurement accuracy is improved, but device usability and ease of operation deteriorate
Solution Approach 1:
The accelerometer system performs self-service by automatically determining its own dominant axis orientation based on gravitational influence without requiring user intervention. The gravitational influence logic autonomously identifies the correct measurement axis, eliminating the need for users to manually orient the device or follow orientation instructions, thereby maintaining measurement accuracy while greatly improving ease of operation.
3Stability of the object's composition
If rolling averages are used to reduce noise, then measurement stability is improved, but response time to orientation changes deteriorates
Solution Approach 1:
The system applies dynamics by adaptively adjusting the rolling average calculation based on detected cadence of motion. When motion is detected, the system modifies the averaging parameters to provide faster response. The cadence detection mechanism allows the system to dynamically switch between stable averaging for static conditions and faster response for dynamic conditions, resolving the contradiction between stability and response speed.
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 approach enhances the rotational insensitivity of accelerometers, allowing for more accurate monitoring of user activity and motion recognition by aligning the dominant axis with the gravitational influence, reducing lag and improving sensitivity to orientation changes.
Implementation Method 1
a gravitational influence is identified based upon the rolling average of accelerations and a dominant axis is assigned based upon the gravitational influence
Data Source
AI summary
A personal electronic device determines its orientation by performing a number of operations. The personal electronic device determines one or more sample periods and creates rolling averages of accelerations for a plurality of axes over the one or more sample periods. The personal electronic device then identifies current values for the rolling averages of accelerations along each of the plurality of axes, wherein the current values indicate a gravitational influence and assigns a dominant axis based upon the current values.