Electromagnetic position measurement system with sensor parasitic loop compensation
Inventors
Ashe, Westley S. • Brunner, Georg
Assignees
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Publication Number
US-12274515-B2
Publication Date
2025-04-15
Expiration Date
Abstract
A magnetic tracking device includes a sensor configured to generate a sensor electromotive force (EMF). The device includes a mechanism configured to select between a first operating mode in which the sensor generates the sensor EMF when receiving the magnetic field and a second operating mode in which the sensor generates a reduced amount of the sensor EMF when receiving the magnetic field. An interconnecting circuit generates a parasitic EMF in each of the first operating mode and the second operating mode. The interconnecting circuit connects to a processing device which receives a first measurement for the first operating mode, the first measurement representing the sensor EMF and the parasitic EMF, receives a second measurement for the second operating mode, the second measurement representing the parasitic EMF, compares the first measurement and the second measurement, and determines an approximate value of the sensor EMF.
Core Innovation
A magnetic tracking device includes a sensor configured to generate a sensor electromotive force (EMF) that measures a magnetic field generated by a magnetic field transmitter. A processing device selects between a first operating mode in which the sensor generates the sensor EMF and a second operating mode in which the sensor generates a reduced sensor EMF, and a switching device placed in parallel with the sensor is in a high impedance state in the first operating mode and in a low impedance state in the second operating mode.
An interconnecting circuit is configured to generate a parasitic EMF in each of the first operating mode and the second operating mode when receiving the magnetic field. In the first operating mode, the processing device receives a first measurement representing the sensor EMF and the parasitic EMF, and in the second operating mode, the processing device receives a second measurement representing the parasitic EMF and the reduced sensor EMF.
The processing device compares the first measurement and the second measurement and determines an approximate value of the sensor EMF based on the comparison. The comparison comprises determining a change in an impedance of the interconnecting circuit in the second operating mode relative to the impedance of the interconnecting circuit in the first operating mode, and in some implementations the processing device further determines an approximate position of the sensor relative to the magnetic field transmitter.
Claims Coverage
The document provides three independent claims covering a magnetic tracking device architecture, a related device configuration using impedance-change-based comparison, and a corresponding method. Across the independent claims, the inventive coverage is focused on operating-mode switching that creates different sensor EMF levels while the interconnecting circuit parasitic EMF is generated in both modes, and on using a comparison of two measurements to determine an approximate value of the sensor EMF.
Mode-selectable sensor EMF via parallel switching device
A sensor generates a sensor electromotive force (EMF) measuring a magnetic field from a magnetic field transmitter; a processing device selects between a first operating mode that produces the sensor EMF and a second operating mode that produces a reduced sensor EMF; a switching device in parallel with the sensor is in a high impedance state in the first operating mode and in a low impedance state in the second operating mode.
Parasitic EMF generation in both operating modes
An interconnecting circuit configured to generate a parasitic EMF in each of the first operating mode and the second operating mode when receiving the magnetic field.
Two-mode measurement comparison to determine approximate sensor EMF
The processing device receives a first measurement representing the sensor EMF and the parasitic EMF in the first operating mode; receives a second measurement representing the parasitic EMF and the reduced sensor EMF in the second operating mode; compares the first measurement and the second measurement; and determines an approximate value of the sensor EMF based on comparing the first measurement and the second measurement.
Impedance-change-based comparison between modes
Comparing the first measurement and the second measurement comprises determining a change in an impedance of the interconnecting circuit in the second operating mode relative to the impedance of the interconnecting circuit in the first operating mode.
DC-component saturation of the sensor in second operating mode
In the method, the second operating mode comprises a direct current (DC) component having a value that exceeds a threshold value to saturate a core of the sensor, while the switching device is in the low impedance state in the second operating mode.
Across independent claims, the core inventive concept is switching a sensor between a first operating mode and a second operating mode using a parallel switching device, while the interconnecting circuit generates parasitic EMF in both modes; then comparing measurements from the two modes to determine an approximate sensor EMF, including an impedance-change-based comparison, with the option in the method to use a second operating mode having a DC component exceeding a threshold to saturate a core.
Stated Advantages
Increased positional accuracy.
Reduced need for shielding/twisting due to compensating interconnect parasitic EMF.
Documented Applications
Magnetic tracking device/system for measuring and determining an approximate position of a sensor relative to a magnetic field transmitter, including cycling sensor operating modes synchronized with a cycle of the magnetic field generated by the magnetic field transmitter.
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