Pulsed-DC position and orientation measurement system

• US 5,453,686 A
• Filed: 04/08/1993
• Issued: 09/26/1995
• Est. Priority Date: 04/08/1993
• Status: Expired due to Term

• Current Assignee: Chittenden Bank (People's United Financial Incorporated)
• Original Assignee: Polhemus Incorporated
• Inventors: Anderson, Peter T.
• Primary Examiner(s): O'Shea, Sandra L.
• Assistant Examiner(s): Edmonds, Warren S.
• Application Number:
  US08/045,469
• Time in Patent Office: 901 Days
• Field of Search: 324/207.12, 324/207.16, 324/207.17, 324/207.26, 324/244, 324/245, 324/247, 324/225, 324/260, 33/361, 364/559
• US Class Current: 324/207.17
• CPC Class Codes: G01S 5/0247 Determining attitude

Abstract

A remote object position and orientation determining system employs electromagnetic coupling to sense the position and orientation of a remote object. A plurality of electromagnetic fields are generated having steady state components by applying time-division multiplexed pulsed DC signals to a plurality of field generating elements having spatially independent components defining a source reference coordinate frame. In this manner, the fields are distinguishable from one another. The generated electromagnetic fields are sensed with a remote sensor having a plurality of passive field-sensing elements having spatially independent elements in order to detect the rate-of-change of each of the generated electromagnetic fields. The output of the remote sensors are integrated in order to establish the steady state components of the generated electromagnetic fields. The steady state components are resolved into remote object position and orientation relative to the source reference coordinate frame.

Claims

1. An apparatus for determining the position and orientation of a remote object relative to a reference coordinate frame comprising:

a source having a plurality of field generating elements, wherein said field generating elements generate electromagnetic fields and have spatially independent components defining a source reference coordinate frame;

a driver, wherein said driver applies to said plurality of field generating elements, signals which generate a plurality of electromagnetic fields, wherein said driver generates pulsed-DC Signals that are applied sequentially to said field generating elements, defining a field generation cycle, whereby said electromagnetic fields have steady state components and are time-division multiplexed, said electromagnetic fields being distinguishable from one another;

a remote sensor having a plurality of field sensing elements, wherein said field sensing elements sense each of said generated electromagnetic fields and have spatially independent components; and

a processor, wherein said processor processes the output of said sensor into remote object position and orientation relative to said source reference coordinate frame, said processor including a signal integrator that is adapted to integrating the output of at least one of said sensing elements over a given period of time in order to establish the steady state components of said generated electromagnetic field and a calculator that is adapted to calculate remote object position and orientation from the steady state components.

2. The apparatus in claim 1 wherein said given period of time is one said field generation cycle.

3. The apparatus in claim 2 wherein said processor samples said integral approximately at the end of each of said pulsed-DC signals.

4. The apparatus in claim 2 wherein said processor samples said integral a plurality of times during each of said pulsed-DC signals.

5. The apparatus in claim 1 wherein processor samples said integral approximately at the end of each of said pulsed-DC signals.

6. The apparatus in claim 5 wherein said processor samples said integral a plurality of times during each of said pulsed-DC signals.

7. The apparatus in claim 1 wherein each of said field sensing elements is a passive sensor that responds to the rate-of-change of said electromagnetic fields.

8. The apparatus in claim 1 wherein said given period of time is one said field generation cycle.

9. The apparatus in claim 1 wherein said processor resets said integrator after said given period of time and samples said integral before and after resetting said integrator.

10. The apparatus in claim 1 wherein said signal integrator is adapted to integrate the outputs of all of said sensing elements over said given period of time.

11. The apparatus in claim 1 wherein said processor includes a programmed computer and wherein said programmed computer defines said integrator.

12. An apparatus for determining the position and orientation of a remote object relative to a reference coordinate frame comprising:

a source having a plurality of field generating elements, wherein said field generating elements generate electromagnetic fields and have spatially independent components defining a source reference coordinate frame;

a driver, wherein said driver applies sequentially to said plurality of field generating elements pulsed-DC signals which are time-division multiplexer, defining a field generation sequence, in order to generate a plurality of electromagnetic fields that have steady state components and are distinguishable from one another;

a remote sensor having a plurality of passive field sensing elements that are responsive to the rate-of-change of said generated electromagnetic fields in order to sense each of said generated electromagnetic fields, said sensing elements having spatially independent components; and

a processor, wherein said processor processes the output of said sensor into remote object position and orientation relative to said source reference coordinate frame.

13. The apparatus in claim 12 wherein said processor includes a signal integrator, wherein said integrator integrates the output of all of said field sensing elements over a given period of time in order to produce an integral for each said output, and a calculator, wherein said calculator calculates remote object position and orientation relative to said source reference coordinate frame from said integrals.

14. The apparatus in claim 13 wherein said given period of time is one said field generation cycle.

15. The apparatus in claim 13 wherein calculator samples each said integral approximately at the end of each of said pulsed-DC signals.

16. The apparatus in claim 13 wherein said calculator samples each said integral a plurality of times during each of said pulsed-DC signals.

17. The apparatus in claim 13 wherein said processor resets said integrator after said given period of time and samples said integral before and after resetting said integrator.

18. The apparatus in claim 17 wherein said calculator calculates remote position and orientation from a matrix S where ##EQU2## where XsrcXsen=AD(XSRC,Xinteg)-0.75AD(RESET,Xinteg)-0.25AD(NOSRC,Xinteg)

XsrcYsen=AD(XSRC,Yinteg)-0.75AD(RESET,Yinteg)-0.25AD(NOSRC,Yinteg)

XsrcZsen=AD(XSRC,Zinteg)-0.75AD(RESET,Zinteg)-0.25AD(NOSRC,Zinteg)

YsrcXsen=AD(YSRC,Xinteg)-0.50AD(RESET,Xinteg)-0.50AD(NOSRC,Xinteg)

YsrcYsen=AD(YSRC,Yinteg)-0.50AD(RESET,Yinteg)-0.50AD(NOSRC,Yinteg)

YsrcZsen=AD(YSRC,Zinteg)-0.50AD(RESET,Zinteg)-0.50AD(NOSRC,Zinteg)

ZsrcXsen=AD(ZSRC,Xinteg)-0.25AD(RESET,Xinteg)-0.75AD(NOSRC,Xinteg)

ZsrcYsen=AD(ZSRC,Yinteg)-0.25AD(RESET,Yinteg)-0.75AD(NOSRC,Yinteg)

ZsrcZsen=AD(ZSRC,Zinteg)-0.25AD(RESET,Zinteg)-0.75AD(NOSRC,Zinteg)

and where, for X, Y and Z sources and X, Y and Z sensor integrators,

AD(iSRC, jinteg) is the sampled integrator value for the jth sensor integrator;

while the ith source is transmitting,

AD(RESET, jinteg) is the sampled integrator value for the jth sensor integrator during an integrator reset interval, and

AD(NOSRC, jinteg) is the sampled integrator value for the jth sensor integrator during an interval when no transmission source is transmitting.

19. The apparatus in claim 14 wherein said processor includes a programmed computer and wherein said programmed computer defines said integrator.

20. The apparatus in claim 12 wherein each of said field sensing elements is a dipole antenna.

21. An apparatus for determining the position and orientation of a remote object relative to a reference coordinate frame comprising:

a source having a plurality of field generating elements, wherein said field generating elements generate electromagnetic fields and have spatially independent components defining a source reference coordinate frame;

a driver, wherein said driver applies sequentially to said plurality of field generating elements pulsed-DC signals which are time-division multiplexed in order to generate a plurality of electromagnetic fields that have steady state components and are distinguishable from one another;

a remote sensor having a plurality of passive field sensing elements that are responsive to the rate-of-change of said generated electromagnetic fields in order to sense each of said generated electromagnetic fields, said sensing elements having spatially independent components; and

an integrator, wherein said integrator integrates the output of said remote sensor in order to establish the steady state components of said generated electromagnetic fields.

22. The apparatus in claim 21 including a processor, wherein said processor resolves said steady state components into remote object position and orientation.

23. The apparatus in claim 21 wherein said processor includes a programmed computer and wherein said programmed computer defines said integrator.

24. A method of determining the position and orientation of a remote object relative to a reference coordinate frame comprising:

generating a plurality of electromagnetic fields in a source reference coordinate frame, said fields having spatially independent components and being distinguishable from one another, wherein said generating includes applying pulsed-DC signals sequentially to a plurality of field generator elements having spatially independent components, defining a field generation cycle, whereby said electromagnetic fields have steady state components and are time-division multiplexed;

sensing said generated electromagnetic fields with a remote sensor having a plurality of field sensing elements, said sensing elements having spatially independent components in order to detect each of said generated electromagnetic fields; and

processing the output of said remote sensor into remote object position and orientation relative to said source reference coordinate frame by integrating the output of said field sensor over a given period of time in order to establish the steady state components of said generated electromagnetic fields and resolving said steady state components into remote object position and orientation.

25. The method of claim 24 wherein said processing includes integrating the output of said field sensor over a given period of time that is one said transmission cycle.

26. The method of claim 25 wherein said processing includes sampling said integral approximately at the end of each of said pulsed-DC signals.

27. The method of claim 25 wherein said processing includes sampling said integral a plurality of times during each of said pulsed-DC signals.

28. The method of claim 24 wherein said processing includes sampling said integral approximately at the end of each of said pulsed-DC signals.

29. The method of claim 24 wherein said processing includes sampling said integral a plurality of times during each of said pulsed-DC signals.

30. The method of claim 24 wherein said sensing includes use of passive sensing elements that respond to the rate-of-change of said electromagnetic fields.

31. The method of claim 24 wherein said processing includes resetting said integral after said given period of time.

32. The method of claim 31 including sampling said integral before and after said resetting.

33. The apparatus in claim 24 wherein said processing includes integrating the outputs of all of said field sensing elements over said given period of time in order to produce multiple integrals, sampling said multiple integrals and calculating said remote object position and orientation from the sampled integrals.

34. A method of determining the position and orientation of a remote object relative to a reference coordinate frame comprising:

generating a plurality of electromagnetic fields by applying time-division multiplexed pulsed-DC signals to a plurality of field generating elements, defining a field generation cycle, said field generating elements having spatially independent components defining a source reference coordinate frame, whereby said fields have steady state components and are distinguishable from one another;

sensing said generated electromagnetic fields with a remote sensor having a plurality of passive field sensing elements having spatially independent components in order to detect the rate-of-change of each of said generated electromagnetic fields; and

resolving the output of said remote sensor into remote object position and orientation relative to said source reference coordinate frame.

35. The method of claim 34 wherein said resolving includes integrating the output of said passive field sensor over a given period of time in order to produce an integral for each said independent component, and calculating remote object position and orientation from the integrals.

36. The method of claim 35 wherein said resolving includes integrating over a given period of time that is one said field generation cycle.

37. The method of claim 35 wherein said resolving includes sampling each said integral approximately at the end of each of said pulsed-DC signals.

38. The method of claim 35 wherein said resolving includes sampling each said integral a plurality of times during each of said pulsed-DC signals.

39. The method of claim 35 wherein said resolving includes resetting said integral after said given period of time.

40. The method of claim 39 including sampling said integral before and after said resetting.

41. The method of claim 40 wherein said resolving includes calculating remote position and orientation from a matrix S where ##EQU3## where XsrcXsen=AD(XSRC,Xinteg)-0.75AD(RESET,Xinteg)-0.25AD(NOSRC,Xinteg)

XsrcYsen=AD(XSRC,Yinteg)-0.75AD(RESET,Yinteg)-0.25AD(NOSRC,Yinteg)

XsrcZsen=AD(XSRC,Zinteg)-0.75AD(RESET,Zinteg)-0.25AD(NOSRC,Zinteg)

YsrcXsen=AD(YSRC,Xinteg)-0.50AD(RESET,Xinteg)-0.50AD(NOSRC,Xinteg)

YsrcYsen=AD(YSRC,Yinteg)-0.50AD(RESET,Yinteg)-0.50AD(NOSRC,Yinteg)

YsrcZsen=AD(YSRC,Zinteg)-0.50AD(RESET,Zinteg)-0.50AD(NOSRC,Zinteg)

ZsrcXsen=AD(ZSRC,Xinteg)-0.25AD(RESET,Xinteg)-0.75AD(NOSRC,Xinteg)

ZsrcYsen=AD(ZSRC,Yinteg)-0.25AD(RESET,Yinteg)-0.75AD(NOSRC,Yinteg)

ZsrcZsen=AD(ZSRC,Zinteg)-0.25AD(RESET,Zinteg)-0.75AD(NOSRC,Zinteg)

and where, for X, Y and Z sources and X, Y and Z sensor integrators,

AD(iSRC, jinteg) is the sampled integrator value for the jth sensor integrator;

while the ith source is transmitting,

AD(RESET, jinteg) is the sampled integrator value for the jth sensor integrator during an integrator reset interval, and

AD(NOSRC, jinteg) is the sampled integrator value for the jth sensor integrator during an interval when no transmission source is transmitting.

42. A method of determining the position and orientation of a remote object relative to a reference coordinate frame comprising:

generating a plurality of electromagnetic fields having steady state components by applying time-division multiplexed pulsed-DC signals to a plurality of field generating elements having spatially independent components defining a source reference coordinate frame, whereby said fields are distinguishable from one another;

sensing said generated electromagnetic fields with a remote sensor having a plurality of passive field sensing elements having spatially independent elements in order to detect the rate-of-change of each of said generated electromagnetic fields; and

integrating the output of said remote sensor in order to establish the steady state components of said generated electromagnetic fields.

43. The method of claim 42 including resolving said established steady state components into remote object position and orientation.