Magnetic Tracking Synchronization Using IMU Orientation Constraints
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Solution Overview
Problem
Magnetic tracking systems face phase ambiguity issues in wireless setups, where the phase of the transmitted signal is unknown, leading to uncertainty in the receiver's position and orientation relative to the transmitter, especially in applications requiring automatic synchronization without user intervention.
Innovation Solution
The system employs inertial measurement units (IMUs) on both the transmitter and receiver to automatically determine the phase relationship by generating and rotating signal matrices, applying correction matrices, and selecting the calibrated rotated signal matrix with the lowest residual error for synchronization, thereby resolving phase ambiguity without user input.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a wireless magnetic tracking system is used to enable mobility and flexibility, then ease of operation is improved, but phase ambiguity arises causing uncertainty in position and orientation determination
Solution Approach 1:
The patent introduces an intermediary synchronization signal transmitted from the transmitter to the receiver to resolve phase ambiguity. This sync signal serves as a mediator that carries phase reference information, enabling the receiver to correctly interpret the magnetic field signals without requiring physical connection, thus maintaining wireless mobility while ensuring measurement precision.
Solution Approach 2:
The system implements feedback by having the receiver send acknowledgment signals back to the transmitter regarding synchronization status. This feedback mechanism allows the transmitter to adjust its signal transmission to maintain proper phase relationships, ensuring continuous accurate position and orientation determination in the wireless environment.
2Ease of operation
If automatic synchronization is implemented without user intervention, then ease of operation is improved, but device complexity increases due to additional synchronization mechanisms
Solution Approach 1:
The patent merges the synchronization signal transmission with the existing magnetic field signal transmission infrastructure. The sync information is embedded within or alongside the regular tracking signals, allowing automatic synchronization to occur without adding separate dedicated hardware channels, thus reducing overall device complexity while maintaining ease of operation.
Solution Approach 2:
The system implements self-service synchronization where the transmitter and receiver automatically establish and maintain phase synchronization without user intervention. The devices autonomously exchange sync signals, process phase information, and adjust their operation to maintain accurate tracking, eliminating the need for manual setup while keeping the complexity manageable through automated algorithms.
3Measurement precision
If phase synchronization is established to resolve ambiguity, then measurement precision is improved, but loss of time occurs during the synchronization process
Solution Approach 1:
The patent implements preliminary synchronization actions during system initialization and setup phases. The transmitter and receiver establish phase relationships before actual tracking begins, so that when tracking starts, synchronization is already in place. This preliminary action eliminates delays during operation and ensures immediate measurement precision from the start of tracking.
Solution Approach 2:
The system maintains continuous synchronization signals and phase reference transmission throughout operation, not just during initial setup. This continuous action ensures that phase determination remains accurate without requiring periodic re-synchronization, minimizing time loss and maintaining measurement precision continuously during the tracking process.
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 enables automatic synchronization of the magnetic tracking system, allowing for accurate determination of the receiver's position and orientation relative to the transmitter, even in wireless setups, without requiring user intervention, enhancing usability in applications like virtual reality and telehealth-based therapies.
Implementation Method 1
receiver IMU acceleration data from the receiver, receiver IMU angular velocity data from the receiver, transmitter IMU acceleration data from the transmitter, and transmitter IMU angular velocity data from the transmitter
Implementation Method 2
magnetic fields are generated and measured using a system of orthogonal coils to generate position and orientation information
Implementation Method 3
A transmitter has three orthogonal coils that generate the magnetic field signal, and may be located in a fixed position
Data Source
AI summary
Automatic synchronization of a magnetic field transmitter and receiver is performed to resolve phase ambiguity so that phase information, used in determining the position and orientation of the receiver, may be derived and maintained. Inertial measurement unit (IMU) information is used to infer gravity-relative orientations of the transmitter and receiver, which are then used as constraints in the synchronization process to determine the position and orientation of the receiver from all four possible solutions or variations. The variation that best conforms to the IMU orientations is chosen as the sync candidate.