Magnetic Tracking Phase Disambiguation via Time-Multiplexed Coils
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Solution Overview
Problem
Wireless magnetic tracking systems face phase ambiguity issues due to the lack of synchronization between the transmitter and receiver, making it difficult to determine the phase of the received signal components accurately.
Innovation Solution
A method involving co-located orthogonal transmit coils emitting a time-multiplexed sequence of magnetic fields with a known phase relationship, allowing the receiver to derive phase information using Fourier transforms and a matrix determinant calculation to resolve phase ambiguity, ensuring accurate position and orientation calculations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If wireless magnetic tracking systems are used to avoid direct connection between transmitter and receiver, then ease of operation is improved, but measurement precision deteriorates due to phase ambiguity
Solution Approach 1:
The transmitter alternates between activating different coil pairs in a periodic sequence (X-Y, Y-Z, Z-X pairs), with each pair emitting magnetic fields at known phase relationships. This time-multiplexed periodic activation allows the receiver to determine phases relative to a common reference without requiring continuous synchronization, resolving the phase ambiguity problem while maintaining wireless operation
Solution Approach 2:
The system changes the operational parameters by using time-multiplexed activation of different coil pairs with specific duty cycles and timing sequences. By varying which coils are active at different time intervals and establishing known phase relationships during these intervals, the system enables phase determination without continuous transmitter-receiver synchronization
2Productivity
If frequency-multiplexed AC system with continuous sinusoidal signals is used, then productivity is improved, but device complexity increases due to need for synchronization
Solution Approach 1:
Instead of using continuous sinusoidal signals from all coils simultaneously, the system employs periodic activation of different coil pairs in sequence. Each pair is activated for a specific time interval with known phase relationships, maintaining high tracking speed through rapid alternation while eliminating the need for complex continuous synchronization mechanisms
Solution Approach 2:
The continuous tracking function is segmented into discrete time intervals, with different coil pairs activated during different intervals. This segmentation allows each coil pair to be measured independently with known phase relationships, reducing overall system complexity while maintaining productivity through rapid sequential measurement
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 simplifies the resolution of phase ambiguity in wireless magnetic tracking systems without the need for complex synchronization measures, providing accurate position and orientation data.
Implementation Method 1
a magnetic locating system includes a sender or transmitter which applies magnetic fields in space, and a sensor which detects the fields
Implementation Method 2
each transmitter coil is actuated to emit a magnetic field and the resulting magnetic field component in the direction of each sensor coil or other sensor is measured by the receiver
Data Source
AI summary
A method and system for magnetic locating resolves phase ambiguity. The system uses time-division multiplexed magnetic fields emitted from plural transmit coils. The magnetic fields are alternating fields at a carrier frequency, and the fields emitted from different coils in different transmit intervals have known phase relationship with one another as, for example where the alternating fields are coherent with one another. A receiver uses a plurality of sensor coils and derives plural components using the common phase reference or plural phase reference times having a known relationship. If the determinant of a matrix of the components has a first value, the phase information in the components is correct, and position and orientation are derived from the components. If the determinant has a second value, the phase information in the components is incorrect. In this case, corrected components are formed by shifting the phases of the components π radians; the position and orientation are derived from the corrected components.