High speed high resolution ultrasonic position and orientation tracker using a single ultrasonic frequency

• US 5,495,427 A
• Filed: 06/29/1994
• Issued: 02/27/1996
• Est. Priority Date: 07/10/1992
• Status: Expired due to Term

• Current Assignee: MedFlex LLC
• Original Assignee: Northrop Grumman Corporation
• Inventors: Lee, Gregory R., Puma, Sam C., Brody, Brian D.
• Primary Examiner(s): Voeltz, Emanuel T.
• Assistant Examiner(s): CHOI, KYLE JAEHUN
• Application Number:
  US08/267,709
• Time in Patent Office: 608 Days
• Field of Search: 364/516, 364/559, 364/561, 364/562, 367/117, 367/118, 367/124, 367/125, 340/870.41, 244/221, 244/222
• US Class Current: 367/117
• CPC Class Codes: G01S 5/186 Determination of attitude using inertial means G01C9/00; control of attitude G05D1/49
• CPC Class Codes: G01S 5/30 Determining absolute distances from a plurality of spaced points of known location

Abstract

An ultrasonic tracking system embodying the invention has an array of plural ultrasonic detectors at discrete locations, the plural detectors being responsive to an ultrasonic signal of frequency f emanating from a single remote transmitter to produce respective plural electronic signals corresponding to the ultrasonic signal as received at respective ones of the plural detectors, and a processor for determining from the plural electronic signals a direction of travel of the ultrasonic signal relative to the array of ultrasonic detectors. In order to provide range, a phase shift key encoder connected to the transmitter encodes every N cycles of the ultrasonic signal with one of a succession of encoder counts, while a phase shift key decoder coupled to receive an electronic signal from one of the plural detectors produces a new decoder count every N cycles of the electronic signal that are decodable. A range processor connected to the phase shift key encoder and to the phase shift key decoder receives simultaneously the encoder counts and the decoder counts. From the encoder and decoder counts, the range processor computes a distance between the transmitter and the one detector.

Claims

1. An acoustic tracking system, comprising:

a transmitter producing an acoustic signal of frequency f at first location;

an array of plural acoustic detectors at a second location, said array of plural acoustic detectors comprising plural detectors at discrete locations, said plural detectors being responsive to said acoustic signal to produce respective plural electronic signals corresponding to said acoustic signal as received at respective ones of said plural detectors, said array having a frame of reference;

a processor for generating a location Signal defining an orientation of said first location relative to said second location;

means for storing a matrix K which is a function of a displacement matrix D comprising vectors defining locations of respective ones of said plural detectors in said frame of reference;

means for sensing the phase angles of each of said electronic signals and for producing a phase difference vector comprising, respectively, differences between the phase angle of the electronic signal of one of said plural detectors and the phase angles of the electronic signals of respective remaining ones of said plural detectors;

means for producing an orientation vector defining an orientation of said transmitter relative to said frame of reference of said array of detectors by multiplying said phase difference vector by said matrix K; and

wherein,

the processor comprises means for producing an updated location signal from said orientation vector.

2. The acoustic tracking system of claim 1 further comprising means for computing an azimuth angle and an elevation angle from said orientation vector.

3. The acoustic tracking system of claim 1 further comprising:

a phase shift key encoder connected to said transmitter for encoding every N cycles of said acoustic signal with one of a succession of encoder counts;

a phase shift key decoder coupled to receive an electronic signal from one of said plural detectors for producing a new decoder count every N cycles of said electronic signal that are decodable; and

a range processor connected to said phase shift key encoder and to said phase shift key decoder to receive simultaneously said encoder counts and said decoder counts, said range processor comprising means for computing from said encoder counts and said decoder counts a distance between said transmitter and said one detector.

4. The acoustic tracking system of claim 3 wherein said means for computing comprises:

means for storing a first encoder count from said phase shift key encoder;

means responsive upon receipt from said phase shift key decoder of a decoder count equal to said first encoder count for sensing a concurrent encoder count from said phase shift key encoder; and

means for computing said distance from a difference between said concurrent encoder count and said first encoder count.

5. The acoustic tracking apparatus of claim 4 wherein said means for computing comprises means for multiplying said difference by Nc/f, where N is the number of cycles of said acoustic signal encoded by said phase shift key encoder with an encoder count, c is the speed of propagation of said acoustic signal from said transmitter to said array of acoustic detectors and f is the frequency of said acoustic signal.

6. The acoustic tracking system of claim 5 wherein said encoder count and said decoder count each lie in a range of values between 0 and 2^N -1.

7. The acoustic tracking system of claim 6 wherein said phase shift key encoder employs a phase shift key code in which respective ones of said N cycles correspond to respective binary bits and wherein each one of said N cycles represents a binary one if shifted by a predetermined phase shift and represents a binary zero if not shifted.

8. The acoustic tracking system of claim 7 wherein said predetermined phase shift is 180 degrees.

9. The acoustic tracking system of claim 1 wherein at least some of said plural acoustic detectors lie in a plane.

10. The acoustic tracking system of claim 9 wherein at least another one of said plural detectors lies out of said plane.

11. An ultrasonic tracking system, comprising:

an array of plural ultrasonic detectors at discrete locations, said plural detectors being responsive to an ultrasonic signal of frequency f emanating from a remote transmitter to produce respective plural electronic signals corresponding to said ultrasonic signal as received at respective ones of said plural detectors;

a processor for generating a location signal defining an orientation of said remote transmitter to said array;

means for storing a matrix K which is a function of a displacement matrix D comprising location vectors defining locations of respective ones of said plural detectors in said frame of reference;

means for sensing the phase angles of each of said electronic signals and for producing a phase difference vector comprising, respectively, differences between the phase angle of the electronic signal of one of said plural detectors and the phase angles of the electronic signals of respective remaining ones of said plural detectors;

means for producing an orientation vector defining an orientation of said transmitter relative to said frame of reference of said array of detectors by multiplying said phase difference vector by said matrix K; and

wherein,

the processor comprises means for producing an updated location signal from said direction of travel.

12. The ultrasonic tracking system of claim 11 further comprising means for computing an azimuth angle and an elevation angle from said orientation vector.

13. The ultrasonic tracking system of claim 12 wherein said means for sensing phase angles comprise:

respective analog to digital converters having analog inputs connected to respective ones of said plural detectors and having digital outputs;

respective digital signal processors having digital inputs connected to the digital outputs of respective analog to digital converters, said digital signal processors being programmed to compute a phase angle of the signal received at its input.

14. The ultrasonic tracking system of claim 11 wherein each row of said displacement matrix D comprises a respective one of said location vectors, and wherein said matrix K is equal to [c/2pif][D^T DD^T ]^-1, where c is the speed of propagation of said ultrasonic signal and f is the frequency of said ultrasonic signal.

15. The ultrasonic tracking system of claim 11 further comprising:

a phase shift key encoder connected to said transmitter for encoding every N cycles of said ultrasonic signal with one of a succession of encoder counts;

a phase shift key decoder coupled to receive an electronic signal from one of said plural detectors for producing a new decoder count every N cycles of said electronic signal that are decodable; and

a range processor connected to said phase shift key encoder and to said phase shift key decoder to receive simultaneously said encoder counts and said decoder counts, said range processor comprising means for computing from said encoder counts and said decoder counts a distance between said transmitter and said one detector.

16. The ultrasonic tracking system of claim 15 wherein said means for computing comprises:

means for storing a first encoder count from said phase shift key encoder;

means responsive upon receipt from said phase shift key decoder of a decoder count equal to said first encoder count for sensing a concurrent encoder count from said phase shift key encoder; and

means for computing said distance from a difference between said concurrent encoder count and said first encoder count.

17. The ultrasonic tracking apparatus of claim 16 wherein said means for computing comprises means for multiplying said difference by Nc/f, where N is the number of cycles of said ultrasonic signal encoded by said phase shift key encoder with an encoder count, c is the speed of propagation of said ultrasonic signal from said transmitter to said array of ultrasonic detectors and f is the frequency of said ultrasonic signal.

18. The ultrasonic tracking system of claim 17 wherein said encoder count and said decoder count each lie in a range of values between 0 and 2^N -1.

19. The ultrasonic tracking system of claim 18 wherein said phase shift key encoder employs a phase shift key code in which respective ones of said N cycles correspond to respective binary bits and wherein each one of said N cycles represents a binary one if shifted by a predetermined phase shift and represents a binary zero if not shifted.

20. The ultrasonic tracking system of claim 19 wherein said predetermined phase shift is 180 degrees.