System and method for magnetic position tracking

• US 9,474,465 B2
• Filed: 06/27/2012
• Issued: 10/25/2016
• Est. Priority Date: 06/27/2012
• Status: Active Grant

• Current Assignee: Northern Digital Inc. (Roper Technologies, Inc.)
• Original Assignee: Ascension Technology Corporation (Roper Technologies, Inc.)
• Inventors: Ashe, Westley
• Primary Examiner(s): Hollington, Jermele M
• Assistant Examiner(s): RAJAPUTRA, SURESH KS
• Application Number:
  US13/534,666
• Publication Number:
  US 20140002063A1
• Time in Patent Office: 1,581 Days
• Field of Search: None
• US Class Current: 1/1
• CPC Class Codes: A61B 2034/2051 Electromagnetic tracking systems
• CPC Class Codes: A61B 2090/378 using ultrasound
• CPC Class Codes: A61B 34/20 Surgical navigation systems; Devices for tracking or guiding surgical instruments, e.g. for frameless stereotaxis
• CPC Class Codes: A61B 5/062 using magnetic field
• CPC Class Codes: A61B 8/4254 using sensors mounted on the probe
• CPC Class Codes: G01B 7/003 for measuring position, not involving coordinate determination coordinate measuring G01B7/004

Abstract

An improved system for magnetic position tracking of a device includes a magnetic transmitter, a magnetic sensor, a computing system and a polarity inverter. The magnetic transmitter includes at least one transmitter coil that outputs a transmitted magnetic field having a time derivative component. The magnetic sensor includes at least one sensor coil that has coil terminals having a polarity, and the sensor coil is responsive to the time derivative component of the transmitted magnetic field and outputs a sensor signal. The computing system computes position and angular orientation data of a device based on the sensor signal and the polarity inverter is configured to connect to the coil terminals and to cause the polarity of the coil terminals to be reversed according to a switching signal.

Claims

1. A system for magnetic position tracking of a device comprising:

a magnetic transmitter including at least one transmitter coil, wherein said transmitter coil outputs a transmitted magnetic field including a time derivative component;

a magnetic sensor including at least one sensor coil, wherein said sensor coil includes coil terminals having a polarity, and wherein said sensor coil is responsive to said time derivative component of said transmitted magnetic field and outputs a sensor signal;

a computing system for computing position and angular orientation data of a device based on said sensor signal; and

a polarity inverter configured to connect to said coil terminals and to cause the polarity of the coil terminals to be reversed according to a switching signal,

wherein magnetic field errors that are caused by connectors and traces that are responsive to said time derivative component of said transmitted magnetic field are substantially removed from the sensor signal.

2. The system of claim 1, further comprising a sign inverter configured to invert a digitized output from an analog to digital (A/D) converter, and wherein said sign inverter is operated concurrently with said switching signal, so that said polarity of said coil terminals is maintained at said computing system'"'"'s input.

3. The system of claim 2, further comprising a synchronizer configured to operate concurrently with said magnetic transmitter.

4. The system of claim 2, further comprising averaging means.

5. The system of claim 2, where said sign inverter is also configured to invert the sensor signal at said (A/D) converter'"'"'s input.

6. The system of claim 1, wherein said transmitted magnetic field comprises a sinusoid.

7. The system of claim 6, wherein said sinusoid comprises a plurality of sine waves.

8. The system of claim 6, wherein said sinusoid is continuous with respect to time.

9. The system of claim 6, wherein said sinusoid is time division multiplexed.

10. The system of claim 1 wherein said transmitted magnetic field comprises one of trapezoidal, triangular, half sinusoid, exponential, or square amplitude versus time characteristics shape.

11. The system of claim 1, wherein said polarity inverter is located adjacent to said magnetic sensor.

12. The system of claim 1, wherein said polarity inverter is connected to said magnetic sensor via a twisted pair cable.

13. The system of claim 1, wherein said polarity inverter comprises an analog switch.

14. The system of claim 1, wherein said switching signal is transmitted wirelessly.

15. The system of claim 4, wherein said averaging means is configured to sum signals received with opposite polarity from said sign inverter.

16. The system of claim 4, wherein said averaging means comprises a lowpass filter.

17. A method for magnetic position tracking of a device comprising:

providing a magnetic transmitter including at least one transmitter coil, wherein said transmitter coil outputs a transmitted magnetic field including a time derivative component;

providing a magnetic sensor including at least one sensor coil, wherein said sensor coil includes coil terminals having a polarity, and wherein said sensor coil is responsive to said time derivative component of said transmitted magnetic field and outputs a sensor signal;

providing a computing system for computing position and angular orientation data of a device based on said sensor signal;

providing a polarity inverter configured to connect to said coil terminals and to cause the polarity of the coil terminals to be reversed according to a switching signal;

substantially removing, from the sensor signal, magnetic field errors that are caused by connectors and traces that are responsive to said time derivative component of said transmitted magnetic field.

18. The method of claim 17, further comprising providing a sign inverter configured to invert a digitized output from an analog to digital (A/D) converter, and wherein said sign inverter is operated concurrently with said switching signal, so that said polarity of said coil terminals is maintained at said computing system'"'"'s input.

19. The method of claim 18, further comprising providing a synchronizer configured to operate concurrently with said magnetic transmitter.

20. The method of claim 18, further comprising providing averaging means.

21. The method of claim 18, where said sign inverter is also configured to invert the sensor signal at said (A/D) converter'"'"'s input.

22. The method of claim 17, wherein said transmitted magnetic field comprises a sinusoid.

23. The method of claim 22, wherein said sinusoid comprises a plurality of sine waves.

24. The method of claim 22, wherein said sinusoid is continuous with respect to time.

25. The method of claim 22, wherein said sinusoid is time division multiplexed.

26. The method of claim 17 wherein said transmitted magnetic field comprises one of trapezoidal, triangular, half sinusoid, exponential, or square amplitude versus time characteristics shape.

27. The method of claim 17, wherein said polarity inverter is located adjacent to said magnetic sensor.

28. The method of claim 17, wherein said polarity inverter is connected to said magnetic sensor via a twisted pair cable.

29. The method of claim 17, wherein said polarity inverter comprises an analog switch.

30. The method of claim 17, wherein said switching signal is transmitted wirelessly.

31. The method of claim 20, wherein said averaging means is configured to sum signals received with opposite polarity from said sign inverter.

32. The method of claim 20, wherein said averaging means comprises a lowpass filter.

33. A method comprising:

outputting, by a transmitter coil, a transmitted magnetic field including a time derivative component;

outputting, by a sensor coil that is responsive to the time derivative component of the transmitted magnetic field, a sensor signal;

computing position and angular orientation data of the sensor coil based on the sensor signal;

reversing a polarity of coil terminals of the sensor coil according to a switching signal; and

substantially removing, from the sensor signal, magnetic field effects caused by conductive connections that are responsive to the time derivative component of the transmitted magnetic field.