Hemisphere Ambiguity Correction in EM Position Tracking
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Solution Overview
Problem
Electromagnetic position tracking systems face hemisphere ambiguity, where multiple valid solutions arise from calculations converting EM field magnitude values into position data, leading to uncertainty in determining the correct position of a receiver relative to a transmitter.
Innovation Solution
Incorporating a second sensor, such as an IMU, to generate direction of movement data, which is compared with estimated movement derived from EM pose values to disambiguate the correct pose, thereby resolving hemisphere ambiguity without user input.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If EM field magnitude values are used to calculate position data, then position tracking is enabled, but hemisphere ambiguity occurs resulting in multiple valid solutions
Solution Approach 1:
The patent introduces an intermediary sensor (such as an accelerometer, gyroscope, or magnetometer) that provides additional measurement data to resolve the hemisphere ambiguity. This intermediary sensor acts as a mediator between the EM field measurements and the final position determination, providing the extra information needed to select the correct hemisphere without modifying the fundamental EM tracking system.
Solution Approach 2:
The patent adds another dimension of measurement by incorporating data from a second sensor type. Instead of relying solely on the three spatial dimensions from EM field magnitude, the system adds a fourth dimension of information (such as acceleration, angular velocity, or magnetic field direction) that breaks the symmetry and allows disambiguation between opposite hemispheres.
2Measurement precision
If a second sensor is added to resolve hemisphere ambiguity, then position accuracy improves, but device complexity increases
Solution Approach 1:
The patent leverages the universality of modern mobile devices by using sensors (accelerometers, gyroscopes, magnetometers) that are already standard components in smartphones and tablets. This multi-functional approach allows the same device to perform both its primary functions and EM position tracking with ambiguity resolution, avoiding the need for specialized dedicated hardware.
Solution Approach 2:
The patent enables the mobile device to resolve its own position ambiguity using its built-in sensors without requiring external assistance or additional specialized equipment. The device serves itself by utilizing its existing sensor suite to disambiguate the EM field measurements, reducing system complexity from an external perspective.
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 effectively selects the correct candidate pose value aligned with the direction of movement, improving the accuracy and user experience in position tracking systems by eliminating ambiguity in EM field calculations.
Implementation Method 1
a transmitter that generates an EM field using a tri-axis coil to induce a current on a second tri-axis coil located at a remote receiver
Data Source
AI summary
A method of receiving EM field magnitude values indicative of a first pose of a mobile unit in relation to a base unit, receiving sensor data from a second sensor associated with the mobile unit, where the sensor data is indicative of a direction of movement of the mobile unit, calculating a set of candidate pose solutions based on the EM field magnitude values, selecting a pose from the set of candidate pose solutions based on the sensor data from the second sensor, and sending the pose to the processor.