PASSIVE RANGING/TRACKING PROCESSING METHOD

• US 20020180636A1
• Filed: 04/23/2001
• Published: 12/05/2002
• Est. Priority Date: 04/22/2000
• Status: Active Grant

• Current Assignee: American GNC Corporation
• Original Assignee: American GNC Corporation
• Inventors: Lin, Ching-Fang, An, Dong
• Granted Patent: US 6,489,922 B1
• Time in Patent Office: Days
• US Class Current: 342/357.14
• CPC Class Codes: G01C 21/165 combined with non-inertial navigation instruments
• CPC Class Codes: G01C 3/18 with one observation point at each end of the base G01C3/20 takes precedence
• CPC Class Codes: G01S 11/12 using electromagnetic waves other than radio waves
• CPC Class Codes: G01S 5/0284 Relative positioning
• CPC Class Codes: G01S 5/04 Position of source determined by a plurality of spaced direction-finders
• CPC Class Codes: G01S 5/16 using electromagnetic waves other than radio waves

Abstract

A passive ranging/tracking processing method provides information from passive sensors and associated tracking control devices and GPS/IMU integrated navigation system, so as to produce three dimensional position and velocity information of a target. The passive ranging/tracking processing method includes the procedure of producing two or more sets of direction measurements of a target with respect to a carrier, such as sets of elevation and azimuth angles, from two or more synchronized sets of passive sensors and associated tracking control devices, installed on different locations of the carrier, computing the range vector measurement of the target with respect to the carrier using the two or more sets of direction measurements, and filtering the range vector measurement to estimate the three-dimensional position and velocity information of the target.

Claims

1. A passive ranging/tracking method for tracking a target, comprising the steps of:

(a) producing at least a first and a second sets of direction measurements of the target with respect to a carrier from at least a first and second passive sensors through at least a first and second tracking control devices respectively, wherein said two passive sensors are installed on said carrier and each of said passive sensors is controlled by said respective tracking control device to keep pointing to said target;

(b) producing navigation data of said carrier, including position, velocity, and attitude data, using an onboard navigation system;

(c) computing a target range vector measurement of said target with respect to said carrier using said two sets of direction measurements; and

(d) extracting three-dimensional position and velocity information of said target at a current epoch using said target range vector measurement.

2. The passive ranging/tracking method, as recited in claim 1, wherein each of said passive sensors receives energy or signals emitted by said target and generates said first and second sets of direction measurements of said target which are sets of elevation and azimuth angle measurements of said target respectively.

3. The passive ranging/tracking method, as recited in claim 2, wherein said range vector measurement contains direction and distance information of said target with respect to said carrier.

4. The passive ranging/tracking method, as recited in claim 1, wherein each of said tracking control device comprises a two degree-of-freedom observation platform, wherein each of said passive sensors is generated mounted on said two degree-of-freedom observation platform in order to isolate a maneuvering motion of said carrier to keep tracking said target.

5. The passive ranging/tracking method, as recited in claim 4, wherein each of said tracking control devices comprises an encoder installed in two gimbal axes to output a precise angular position of said passive sensor direction relative to a carrier body coordinate system of said carrier.

6. The passive ranging/tracking method, as recited in claim 3, wherein each of said tracking control device comprises a two degree-of-freedom observation platform, wherein each of said passive sensors is generated mounted on said two degree-of-freedom observation platform in order to isolate a maneuvering motion of said carrier to keep tracking said target.

7. The passive ranging/tracking method, as recited in claim 6, wherein each of said tracking control devices comprises an encoder installed in two gimbal axes to output a precise angular position of said passive sensor direction relative to a carrier body coordinate system of said carrier.

8. The passive ranging/tracking method, as recited in claim 1 or 3, wherein the step (a) further comprises the steps of:

(a.1) producing said first set of direction measurements of said target with respect to said carrier using said first passive sensor through said first tracking control device; and

(a.2) producing said second set of direction measurements of said target with respect to said carrier using said second passive sensor through said second tracking control device.

9. The passive ranging/tracking method, as recited in claim 8, wherein the step (c) further comprises said steps of:

(c.1) forming a first presumed target-sensor vector, representing a direction measurement between said first passive sensor and said target, expressed in a first passive sensor coordinate system, using said first elevation angle and azimuth angle measurement of said target from output of said first passive sensor and a first unknown distance between said first passive sensor and said target;

(c.2) forming a second presumed target-sensor vector, representing a direction measurement between said second passive sensor and said target, expressed in a second passive sensor coordinate system, using said second elevation angle and azimuth angle measurement of said target from output of said second passive sensor and a second unknown distance between said second passive sensor and said target;

(c.3) converting said first presumed target-sensor vector from said first passive sensor coordinate system to a navigation coordinate system of said carrier, using navigation data from a GPS/IMU integrated navigation system which provides position and attitude information of said carrier;

(c.4) converting said second presumed target-sensor vector from said second passive sensor coordinate system to said navigation coordinate system of said carrier, using said navigation data from said GPS/IMU integrated navigation system;

(c.5) computing said first passive sensor location vector, expressed in a local navigation coordinate system, using knowledge of a first passive sensor location in a carrier body coordinate system and said navigation data from said GPS/IMU integrated navigation system;

(c.6) computing said second passive sensor location vector, expressed in said local navigation coordinate system, using knowledge of a second passive sensor location in said carrier body coordinate system and said navigation data from said GPS/IMU integrated navigation system;

(c.7) forming a first presumed target vector, expressed in navigation coordinates, by adding said first target-sensor vector and said first passive sensor location vector;

(c.8) forming a second presumed target vector expressed in said navigation coordinates, by adding said second target-sensor vector and said second passive sensor location vector;

(c.9) finding said first unknown distance and said second known distance, using said first presumed target vector and said second presumed target vector;

(c.10) forming said first target vector, by inserting said first known distance into said first presumed target vector;

(c.11) forming said second target vector, by inserting said second known distance into said second presumed target vector; and

(c.12) forming a range vector measurement, using said first target vector and said second target vector.

10. The passive ranging/tracking method, as recited in claim 9, wherein the step (c.9) further comprises the steps of:

(c.9.A1) forming a vector equation by differencing said first target vector and said second target vector; and

(c.9.A2) finding said first unknown distance and said second unknown distance, by resolving said vector equation, thereby a first position of said first passive sensors in said carrier body coordinate system and said target determine a first straight line in a 3-dimensional space and a second position of said second passive sensors in said carrier body coordinate system and said target determine a second straight line in said 3-dimensional space, so that an intersecting point of said first and second straight lines is a ranged position of said target.

11. The passive ranging/tracking method, as recited in claim 9, wherein the step (c.9) further comprises the steps of:

(c.9.B1) forming a formula for a distance parameter, which represents a distance of two points between said first target vector and said second target vector, using said first target vector and said second target vector; and

(c.9.B2) finding a set of said first unknown distance and said second unknown distance, which makes a value of said distance parameter be minimal.

12. The passive ranging/tracking method, as recited in claim 9, wherein the step (c.9) further comprises the steps of:

(c.9.C1) forming a vector equation by differencing said first target vector and said second target vector; and

(c.9.C2) finding said first unknown distance and said second unknown distance, by resolving said vector equation using a least squares method.

13. The passive ranging/tracking method, as recited in claim 9, wherein the step (d) further comprises said step of filtering said range vector measurement at each epoch to estimate a current position of said target by a filter at said current epoch.

14. The passive ranging/tracking method, as recited in claim 10, wherein the step (d) further comprises said step of filtering said range vector measurement at each epoch to estimate a current position of said target by a filter at said current epoch.

15. The passive ranging/tracking method, as recited in claim 11, wherein the step (d) further comprises said step of filtering said range vector measurement at each epoch to estimate a current position of said target by a filter at said current epoch.

16. The passive ranging/tracking method, as recited in claim 12, wherein the step (d) further comprises said step of filtering said range vector measurement at each epoch to estimate a current position of said target by a filter at said current epoch.

17. The passive ranging/tracking method, as recited in claim 1, wherein each of said passive sensors is passive image sensor and the step (a) comprises the steps of:

(a.1) determining at least a first and a second feature area in at least two synchronized image data from said two passive image sensors, wherein said pair of features represents said target;

(a.2) computing a centroid for each of said feature areas in each of said synchronized images; and

(a.3) computing said direction measurements, using said centroids.

18. The passive ranging/tracking method, as recited in claim 17, wherein, in the step (a.1), said feature areas are determined by a feature matching method.

19. The passive ranging/tracking method, as recited in claim 18, wherein said feature matching method is an attributed graph matching, wherein attributed graphs are represented by nodes and arcs where each of said nodes corresponds to a derived image feature and arcs represent relationships between said nodes.

20. The passive ranging/tracking method, as recited in claim 17, wherein before the step (a.1), further comprises the steps of detecting said moving target in both images from said passive image sensors.

21. The passive ranging/tracking method, as recited in claim 17, wherein said each of said passive image sensors is a visible/infrared camera, wherein said passive image sensors are externally synchronized with GPS timer signals, therefore said visible/infrared camera capture image simultaneously and said synchronized image data are directly related.

22. The passive ranging/tracking method, as recited in claim 17, 20 or 21, wherein the step (c) further comprises said steps of:

(c.1) forming a first presumed target-sensor vector, representing a direction measurement between said first passive sensor and said target, expressed in a first passive sensor coordinate system, using said first elevation angle and azimuth angle measurement of said target from output of said first passive sensor and a first unknown distance between said first passive sensor and said target;

(c.2) forming a second presumed target-sensor vector, representing a direction measurement between said second passive sensor and said target, expressed in a second passive sensor coordinate system, using said second elevation angle and azimuth angle measurement of said target from output of said second passive sensor and a second unknown distance between said second passive sensor and said target;

(c.3) converting said first presumed target-sensor vector from said first passive sensor coordinate system to a navigation coordinate system of said carrier, using navigation data from a GPS/IMU integrated navigation system which provides position and attitude information of said carrier;

(c.4) converting said second presumed target-sensor vector from said second passive sensor coordinate system to said navigation coordinate system of said carrier, using said navigation data from said GPS/IMU integrated navigation system;

(c.5) computing said first passive sensor location vector, expressed in a local navigation coordinate system, using knowledge of a first passive sensor location in a carrier body coordinate system and said navigation data from said GPS/IMU integrated navigation system;

(c.6) computing said second passive sensor location vector, expressed in said local navigation coordinate system, using knowledge of a second passive sensor location in said carrier body coordinate system and said navigation data from said GPS/IMU integrated navigation system;

(c.7) forming a first presumed target vector, expressed in navigation coordinates, by adding said first target-sensor vector and said first passive sensor location vector;

(c.8) forming a second presumed target vector expressed in said navigation coordinates, by adding said second target-sensor vector and said second passive sensor location vector;

(c.9) finding said first unknown distance and said second known distance, using said first presumed target vector and said second presumed target vector;

(c.10) forming said first target vector, by inserting said first known distance into said first presumed target vector;

(c.11) forming said second target vector, by inserting said second known distance into said second presumed target vector; and

(c.12) forming a range vector measurement, using said first target vector and said second target vector.

23. The passive ranging/tracking method, as recited in claim 22, wherein the step (c.9) further comprises the steps of:

(c.9.A1) forming a vector equation by differencing said first target vector and said second target vector; and

(c.9.A2) finding said first unknown distance and said second unknown distance, by resolving said vector equation, thereby a first position of said first passive sensors in said carrier body coordinate system and said target determine a first straight line in a 3-dimensional space and a second position of said second passive sensors in said carrier body coordinate system and said target determine a second straight line in said 3-dimensional space, so that an intersecting point of said first and second straight lines is a ranged position of said target.

24. The passive ranging/tracking method, as recited in claim 22, wherein the step (c.9) further comprises the steps of:

(c.9 B1) forming a formula for a distance parameter which represents a distance of two points between said first target vector and said second target vector, using said first target vector and said second target vector; and

(c.9.B2) finding a set of said first unknown distance and said second unknown distance, which makes a value of said distance parameter be minimal.

25. The passive ranging/tracking method, as recited in claim 22, wherein the step (c.9) further comprises the steps of:

(c.9.C1) forming a vector equation by differencing said first target vector and said second target vector; and

(c.9.C2) finding said first unknown distance and said second unknown distance, by resolving said vector equation using a least squares method.

26. The passive ranging/tracking method, as recited in claim 22, wherein the step (d) further comprises said step of filtering said range vector measurement at each epoch to estimate a current position of said target by a filter at said current epoch.

27. The passive ranging/tracking method, as recited in claim 23, wherein the step (d) further comprises said step of filtering said range vector measurement at each epoch to estimate a current position of said target by a filter at said current epoch.

28. The passive ranging/tracking method, as recited in claim 24, wherein the step (d) further comprises said step of filtering said range vector measurement at each epoch to estimate a current position of said target by a filter at said current epoch.

30. The passive ranginig/tracking method as recited in claim 29, wherein each of said passive sensors receives energy or signals emitted by said target and generates said first and second sets of direction measurements of said target which are sets of elevation and azimuth angle measurements of said target respectively.

31. The passive ranging/tracking method, as recited in claim 30, wherein said range vector measurement contains direction and distance information of said target with respect to said carrier.

32. The passive ranging/tracking method, as recited in claim 29, wherein each of said tracking control device comprises a two degree-of-freedom observation platform, wherein each of said passive sensors is generated mounted on said two degree-of-freedom observation platform in order to isolate a maneuvering motion of said carrier to keep tracking said target.

33. The passive ranging/tracking method, as recited in claim 32, wherein each of said tracking control devices comprises an encoder installed in two gimbal axes to output a precise angular position of said passive sensor direction relative to a carrier body coordinate system of said carrier.

34. The passive ranging/tracking method, as recited in claim 31, wherein each of said tracking control device comprises a two degree-of-freedom observation platform, wherein each of said passive sensors is generated mounted on said two degree-of-freedom observation platform in order to isolate a maneuvering motion of said carrier to keep tracking said target.

35. The passive ranging/tracking method, as recited in claim 34, wherein each of said tracking control devices comprises an encoder installed in two gimbal axes to output a precise angular position of said passive sensor direction relative to a carrier body coordinate system of said carrier.

36. The passive ranging/tracking method, as recited in claim 29 or 31, wherein the step (a) further comprises the steps of:

(a.1) producing said first set of direction measurements of said target with respect to said first carrier using said first passive sensor through said first tracking control device; and

(a.2) producing said second set of direction measurements of said target with respect to said second carrier using said second passive sensor through said second tracking control device.

37. The passive ranging/tracking method, as recited in claim 36, wherein the step (c) further comprises said steps of:

(c.1) forming a first presumed target-sensor vector, representing a direction measurement between said first passive sensor and said target, expressed in a first passive sensor coordinate system, using said first elevation angle and azimuth angle measurement of said target from output of said first passive sensor and a first unknown distance between said first passive sensor and said target;

(c.2) forming a second presumed target-sensor vector, representing a direction measurement between said second passive sensor and said target, expressed in a second passive sensor coordinate system, using said second elevation angle and azimuth angle measurement of said target from output of said second passive sensor and a second unknown distance between said second passive sensor and said target;

(c.3) converting said first presumed target-sensor vector from said first passive sensor coordinate system to a first navigation coordinate system of said first carrier, using first navigation data from a GPS/IMU integrated navigation system which provides position and attitude information of said first carrier;

(c.4) converting said second presumed target-sensor vector from said second passive sensor coordinate system to a second navigation coordinate system of said second carrier, using said second navigation data from said GPS/IMU integrated navigation system which provides position and attitude information of said second carrier;

(c.5) computing said first passive sensor location vector, expressed in a first local navigation coordinate system, using knowledge of a first passive sensor location in a first carrier body coordinate system and said first navigation data from said GPS/IMU integrated navigation system;

(c.6) computing said second passive sensor location vector, expressed in a second local navigation coordinate system, using knowledge of a second passive sensor location in a second carrier body coordinate system and said second navigation data from said GPS/IMU integrated navigation system;

(c.7) forming a first presumed target vector, expressed in navigation coordinates, by adding said first target-sensor vector and said first passive sensor location vector;

(c.8) forming a second presumed target vector expressed in said navigation coordinates, by adding said second target-sensor vector and said second passive sensor location vector;

(c.9) finding said first unknown distance and said second known distance, using said first presumed target vector and said second presumed target vector;

(c.10) forming said first target vector, by inserting said first known distance into said first presumed target vector;

(c.11) forming said second target vector, by inserting said second known distance into said second presumed target vector; and

(c.12) forming a range vector measurement, using said first target vector and said second target vector.

38. The passive ranging/tracking method, as recited in claim 37, wherein the step (c.9) further comprises the steps of:

(c.9.A1) forming a vector equation by differencing said first target vector and said second target vector; and

(c.9.A2) finding said first unknown distance and said second unknown distance, by resolving said vector equation, thereby a first position of said first passive sensors in said first carrier body coordinate system and said target determine a first straight line in a 3-dimensional space and a second position of said second passive sensors in said second carrier body coordinate system and said target determine a second straight line in said 3-dimensional space, so that an intersecting point of said first and second straight lines is a ranged position of said target.

39. The passive ranging/tracking method, as recited in claim 37, wherein the step (c.9) further comprises the steps of:

(c.9.B1) forming a formula for a distance parameter, which represents a distance of two points between said first target vector and said second target vector, using said first target vector and said second target vector; and

(c.9.B2) finding a set of said first unknown distance and said second unknown distance, which makes a value of said distance parameter be minimal.

40. The passive ranging/tracking method, as recited in claim 37, wherein the step (c.9) further comprises the steps of:

(c.9.C1) forming a vector equation by differencing said first target vector and said second target vector; and

(c.9.C2) finding said first unknown distance and said second unknown distance, by resolving said vector equation using a least squares method.

41. The passive ranging/tracking method, as recited in claim 37, wherein the step (d) further comprises said step of filtering said range vector measurement at each epoch to estimate a current position of said target by a filter at said current epoch.

42. The passive ranging/tracking method, as recited in claim 38, wherein the step (d) further comprises said step of filtering said range vector measurement at each epoch to estimate a current position of said target by a filter at said current epoch.

43. The passive ranging/tracking method, as recited in claim 39, wherein the step (d) further comprises said step of filtering said range vector measurement at each epoch to estimate a current position of said target by a filter at said current epoch.

44. The passive ranging/tracking method, as recited in claim 40, wherein the step (d) further comprises said step of filtering said range vector measurement at each epoch to estimate a current position of said target by a filter at said current epoch.

45. The passive ranging/tracking method, as recited in claim 37, wherein each of said passive sensors is passive image sensor and the step (a) comprises the steps of:

(a.1) determining at least a first and a second feature area in at least two synchronized image data from said two passive image sensors, wherein said pair of features represents said target;

(a.2) computing a centroid for each of said feature areas in each of said synchronized images; and

(a.3) computing said direction measurements, using said centroids.

46. The passive ranging/tracking method, as recited in claim 45, wherein, in the step (a.1), said feature areas are determined by a feature matching method.

47. The passive ranging/tracking method, as recited in claim 46, wherein said feature matching method is an attributed graph matching, wherein attributed graphs are represented by nodes and arcs where each of said nodes corresponds to a derived image feature and arcs represent relationships between said nodes.

48. The passive ranging/tracking method, as recited in claim 45, wherein before the step (a.1), further comprises the steps of detecting said moving target in both images from said passive image sensors.

49. The passive ranging/tracking method, as recited in claim 45, wherein said each of said passive image sensors is a visible/infrared camera, wherein said passive image sensors are externally synchronized with GPS timer signals, therefore said visible/infrared camera capture image simultaneously and said synchronized image data are directly related.

29. A passive ranging/tracking method for tracking a target, comprising the steps of:

(a) producing at least a first and a second sets of direction measurements of the target with respect to at least a first carrier and a second carrier from at least a first and second passive sensors through at least a first and second tracking control devices respectively, wherein said passive sensors and said tracking control devices are installed on said carriers respectively and each of said passive sensors is controlled by said respective tracking control device to keep pointing to said target;

(b) producing navigation data of said first and second carriers, including position, velocity, and attitude data, using a first onboard navigation system provided on said first carrier and a second onboard navigation system on said second carrier;

(c) computing a target range vector measurement of said target with respect to each of said carriers, using said two or more sets of direction measurements;

wherein said first carrier and said second carrier are data-linked; and

(d) extracting three-dimensional position and velocity information of said target, expressed in a navigation coordinate system, at a current epoch using said target range vector measurement.