Discretized Numerical Field Model for Electromagnetic Tracking
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Solution Overview
Problem
Electromagnetic trackers are prone to inaccuracies and instability when dealing with significant field distortions caused by conductive or ferromagnetic objects, leading to unreliable position and orientation measurements.
Innovation Solution
The implementation of a discretized numerical field model for electromagnetic tracking, which replaces the conventional analytical dipole model, allows for more stable distortion compensation by representing the electromagnetic field as a finite series of numerical values, improving the accuracy of position and orientation tracking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If conventional analytical dipole model is used for electromagnetic tracking, then the tracking algorithm is simple to implement, but the algorithm becomes unstable when dealing with significant field distortions from conductive or ferromagnetic objects
Solution Approach 1:
The patent transforms the continuous analytical dipole model parameters into discrete numerical field values at predefined grid points. This parameter transformation from continuous analytical functions to discrete numerical values enables stable distortion compensation by representing the electromagnetic field as a finite series of numerical values that can be robustly fitted even when measurements are considerably deviated from model predictions
Solution Approach 2:
The patent replaces the conventional analytical dipole model (mathematical continuous function) with a discretized numerical field model (numerical discrete representation). This substitution involves creating a numerical model through data acquisition at grid points and using numerical fitting algorithms instead of analytical fitting, which provides stability when dealing with significant field distortions
2Measurement precision
If P&O mapping is used to correct distortion, then position and orientation measurements can be recovered for fixed sensor positions, but the tracker fails when signals are significantly distorted by conductive shields
Solution Approach 1:
The patent performs preliminary data acquisition and numerical model creation in advance by measuring electromagnetic field values at predefined grid points before actual tracking. This preliminary action creates a complete numerical field model that can handle significant distortions, allowing the system to reliably process measurements even when conductive shields are present during operation
3Device complexity
If conventional tracking algorithms are used, then the system operates with simple model fitting, but the directly-calculated P&O optimization becomes unstable when measurements deviate from model predictions
Solution Approach 1:
The patent segments the continuous electromagnetic field into discrete values at predefined grid points. By dividing the field representation into discrete numerical values rather than using a continuous analytical function, the system enables stable numerical fitting algorithms that can handle measurements considerably deviated from model predictions without becoming unstable
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 enhances the stability and reliability of electromagnetic tracking systems by accurately modeling and compensating for field distortions, ensuring precise position and orientation measurements even in the presence of significant metal interference.
Implementation Method 1
electromagnetic transmitter (Tx) or receiver (Rx)
Implementation Method 2
Presence of metallic targets near to an electromagnetic transmitter (Tx) or receiver (Rx) may distort the transmitting signals
Data Source
AI summary
A method for electromagnetic tracking the position and orientation of an object using a discretized numerical field model, rather than the conventional analytical dipole model. The method including the steps of determining a discretized numerical field model associated with a particular distortion source; acquiring mutual inductance signals between electromagnetic sensors and the particular distortion source, the sensors being rigidly attached to a tracked object; estimating an initial position for the tracked object in the presence of the particular distortion source; refining the estimated position of the tracked object; and estimating an orientation of the tracked object.