Rotating Magnetic Field 3D Positioning Without Line of Sight
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Solution Overview
Problem
Current positioning solutions for objects in computer applications, such as VR/AR games, often require line of sight between sensors and objects, which can be obstructed, limiting their effectiveness.
Innovation Solution
A method using a rotating magnetic field generated by a spinning magnet or pulsed electromagnets to determine the 3D position and orientation of a magnetometer/accelerometer device without line of sight constraints, by separating the external magnetic field and calculating distance and angles from magnetic field readings, and converting these into Cartesian coordinates to derive the object's pose.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If visual tracking with video camera or laser beam is used to track object pose, then positioning accuracy can be achieved, but line of sight is required which can be blocked by obstacles
Solution Approach 1:
The patent replaces optical tracking systems (video cameras, laser beams) with a magnetic field-based sensing system. A rotating magnet generates a time-varying magnetic field that is detected by a magnetometer, eliminating the need for line of sight while maintaining positioning capability. This substitution of mechanical/optical systems with electromagnetic field-based systems resolves the contradiction between measurement precision and adaptability to obstructed environments.
Solution Approach 2:
The system uses a rotating magnet to generate a time-varying magnetic field, transforming the static magnetic field problem into a dynamic one. By rotating the magnet at a known frequency, the system creates a periodic signal that can be analyzed to determine position and orientation. This parameter change from static to dynamic field enables obstacle-free tracking while maintaining measurement accuracy.
2Adaptability or versatility
If a rotating magnetic field is used to determine position without line of sight, then adaptability to obstructed environments is improved, but device complexity increases due to rotating magnet or pulsed electromagnets
Solution Approach 1:
The system employs periodic rotation of a magnet at a known frequency to generate a time-varying magnetic field. This periodic action creates a characteristic signal pattern that can be detected and analyzed to determine position and orientation. The periodic nature of the field generation simplifies the rotating mechanism requirements compared to continuous control systems, as only consistent rotational motion is needed rather than precise positional control.
Solution Approach 2:
The rotating magnet serves multiple functions: it generates the magnetic field for position determination, provides a known frequency reference for signal analysis, and its rotation speed can be used as an additional reference for calibration. This multi-functionality reduces the need for separate reference systems or additional sensors, thereby reducing overall device complexity despite the rotating component.
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
Enables accurate determination of an object's pose in three dimensions without the need for direct line of sight, allowing for reliable input in applications like VR/AR games, even when obstacles block the line of sight.
Implementation Method 1
A method using a rotating magnetic field generated by a spinning magnet or pulsed electromagnets to determine the 3D position and orientation of a magnetometer/accelerometer device
Implementation Method 2
using at least one sensor near the field source, sensing magnetic field strength during at least one complete revolution of the magnet
Data Source
AI summary
To derive three dimensional (3D) position and orientation of a 3-axis (or more) magnetometer/accelerometer device (such as may be implemented in VR or AR headset or computer game controller) without line of sight constraints, a spinning magnetic field is used to discriminate and remove the external (Earth's) magnetic field from the spinning magnetic field. This reduces the problem to finding the distance to the source of the magnetic field using a calibration table (or formula), finding two angles describing the deviation of the magnetic sensor from the axis of rotation of the spinning magnetic field and the phase around this axis, and from these values deriving the orientation of the sensor.