Head-Worn IMU Alignment Calibration with Minimal User Motion
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Solution Overview
Problem
Existing methods for aligning head and sensor coordinate systems in head-worn apparatuses, such as in-ear and over-ear headphones, are inefficient, require significant user intervention, and are not user-friendly, particularly when plug-and-play functionality is desired.
Innovation Solution
A semi-automatic calibration method using a 6-axis IMU with a static calibration stage and a mathematical correction, eliminating the need for complex head motions by leveraging apparatus-specific alignment information to determine misalignment between the head and sensor coordinate systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional calibration methods are used to determine misalignment between head and sensor coordinate systems, then alignment accuracy can be achieved, but the calibration process requires significant user intervention and complex head motions
Solution Approach 1:
The patent applies preliminary action by pre-storing apparatus-specific alignment information (factory calibration data) that represents the typical misalignment between head and sensor coordinate systems. This pre-prepared data eliminates the need for users to perform complex calibration motions, as the system automatically applies this preliminary alignment correction to quickly determine the user's specific misalignment with minimal interaction.
Solution Approach 2:
The system performs self-service calibration by automatically using the stored apparatus-specific alignment information to compute misalignment without requiring the user to execute specific head motions. The calibration process becomes self-contained, using the apparatus's own stored data to guide the minimal user actions needed (such as holding the device statically), thereby reducing dependency on user cooperation.
2Measurement precision
If conventional calibration methods are used to determine misalignment, then alignment information can be obtained, but the calibration process is time-consuming and not user-friendly
Solution Approach 1:
By pre-storing apparatus-specific alignment information at the factory, the system has already performed the time-consuming portion of alignment calibration during manufacturing. This preliminary action allows the field calibration to skip lengthy procedures and directly compute user-specific misalignment using the pre-established reference frame, dramatically reducing calibration time while maintaining accuracy.
Solution Approach 2:
The patent applies partial action by requiring only a static holding position from the user during calibration, rather than demanding complete head motion sequences. This partial user action (holding the device still) combined with the pre-stored alignment information is sufficient to achieve accurate calibration, eliminating the need for excessive calibration motions and reducing time loss.
3Ease of operation
If apparatus-specific alignment information is used for mathematical correction, then calibration can be simplified, but the method requires a static calibration stage with specific user positioning
Solution Approach 1:
The calibration procedure is segmented into two distinct stages: a static calibration stage where the user holds the device in a specific position to capture initial alignment data, and a dynamic calibration stage where the user performs head motions to determine remaining misalignment. This segmentation allows each stage to focus on specific calibration aspects, simplifying the overall process while maintaining systematic thoroughness.
Solution Approach 2:
The static calibration stage serves as a preliminary action that establishes a reference frame using the pre-stored apparatus-specific alignment information. By completing this preliminary alignment correction first, the system simplifies the subsequent dynamic calibration stage, as the remaining misalignment can be determined more easily through head motions without dealing with the full complexity of initial coordinate system misalignment.
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
Achieves precise and reliable alignment of the head and sensor coordinate systems with minimal user interaction, ensuring accurate head tracking under dynamic conditions and improving the user experience.
Implementation Method 1
determining a misalignment of a first sensitive axis of the inertial measurement unit with respect to a direction of gravity
Data Source
AI summary
A method for alignment calibration of an inertial measurement unit contained in a head-worn apparatus. The method includes: wearing an apparatus on the head of a user; performing a static calibration stage including determining a misalignment of a first sensitive axis of the inertial measurement unit with respect to a direction of gravity while the user holds their head statically, looks straight ahead and horizontally.