Tunable filter device for spatial positioning systems

• US 6,889,175 B2
• Filed: 01/13/2003
• Issued: 05/03/2005
• Est. Priority Date: 01/13/2003
• Status: Active Grant

• Current Assignee: Trimble Navigation Limited (Trimble Inc.)
• Original Assignee: Trimble Navigation Limited (Trimble Inc.)
• Inventors: Green, Francisco Roberto
• Primary Examiner(s): Tsai, Carol S. W.
• Application Number:
  US10/341,571
• Publication Number:
  US 20040138859A1
• Time in Patent Office: 841 Days
• Field of Search: 702/122, 702/123, 702/126, 702189-191, 702/193, 702/195, 702/197, 702/198, 455/173.1, 455/176.1, 455/177.1, 455/178.1, 455/180.1, 455/182.1, 455/182.3, 455/183.2, 455/184.1, 455/185.1, 455/186.1, 455/188.1, 455/190.1, 455/192.1, 455/192.3, 455/193.1, 375/295, 375/296, 375/302, 375/316, 375/344, 375/345, 375/346, 375/350
• US Class Current: 702/190
• CPC Class Codes: G01S 5/0215 Interference
• CPC Class Codes: G01S 5/0294 Trajectory determination or predictive filtering, e.g. target tracking or Kalman filtering

Abstract

A device for spatial positioning systems includes a programmable measurement filter that is dynamically tuned by the device signal processing unit. The signal processing unit analyzes available data including the measurement signal to determine the likelihood that a detected measurement comprises true device movement and adjusts the measurement filter bandwidth accordingly.

Claims

1. A device for a spatial positioning system comprising:

a detector adapted to detect a measurement signal;

a signal processing unit communicably coupled to said detector, said signal processing unit adapted to analyze said measurement signal and determine at least one filter parameter value therefrom, said signal processing unit further comprising a programmable measurement filter adapted to receive and filter said measurement signal based upon said at least one filter parameter value determined by said signal processing unit wherein said programmable measurement filter comprises a programmable low pass filter having a cut off frequency determined at least in part, by said at least one filter parameter value provided by said signal processing unit, wherein said signal processing unit selects a first filter parameter value between at least two predetermined filter values, wherein said first parameter value is selected such that said programmable low pass filter has a first cutoff frequency in response to detected device movement and a second cutoff frequency different from said first cutoff frequency in response to detected noise; and

an output device coupled to said signal processing unit.

2. The device according to claim 1, wherein said signal processing unit selects a first filter parameter value from at least two predetermined filter parameter values.

3. The device according to claim 2, wherein said signal processing unit selects said first filter parameter value based upon an attempt to discriminate device movement from noise in said measurement signal.

4. The device according to claim 2, wherein said signal processing unit is adapted to compute said at least one filter parameter value such that a frequency characteristic of said programmable measurement filter varies linearly within a predetermined operational range.

5. The device according to claim 2, wherein said signal processing unit is adapted to compute at least one filter parameter value that varies linearly within a predetermined operational range.

6. The device according to claim 2, wherein said signal processing unit selects a first filter parameter value from within a range of operational values based upon a likelihood that said measurement signal represents device movement compared to noise.

7. The device according to claim 1, wherein said signal processing unit is adapted to compute said at least one filter parameter value such that said cutoff frequency of said programmable measurement filter varies linearly within a predetermined operational range.

8. The device according to claim 1, wherein said signal processing unit is adapted to compute at least one filter parameter value that varies linearly within a predetermined operational range.

9. The device according to claim 1, wherein said signal processing unit compares a first filter output of a first filter to a second filter output of a second filter where said first and second filters have at least one different filter characteristic to discriminate device movement from noise detected by said detector.

10. The device according to claim 9, wherein each of said first and second filters processes said measurement signal.

11. The device according to claim 9, wherein said first filter comprises a median filter and said second filter comprises a low pass filter.

12. The device according to claim 1, wherein said programmable measurement filter is implemented digitally as software code and said signal processing unit communicates said at least one filter parameter value to said programmable measurement filter by storing said at least one filter parameter value in a storage location of a storage device accessible by a processor executing said software code.

13. The device according to claim 12, wherein said processor is a component of said signal processing unit.

14. The device according to claim 1, wherein said programmable measurement filter filters said measurement signal to produce a filtered output signal that is coupled to a display device.

15. The device according to claim 1, wherein said programmable measurement filter filters said measurement signal to produce a filtered output signal that is coupled to an automated control device.

16. The device according to claim 1, wherein said programmable measurement filter filters said measurement signal to produce a filtered output signal that is manipulated to compute a control signal to control an automated control device.

17. The device according to claim 1, wherein said measurement signal comprises at least one of an angular measurement, a detected laser signal, a detected global positioning signal, and a detected automated tracking system signal.

18. The device according to claim 1, wherein said measurement signal is communicated from said detector to said signal processing unit using a wireless communications link.

19. The device according to claim 18, wherein said wireless communications link comprises a wireless radio link.

20. A device for a spatial positioning system comprising:

a detector adapted to provide a measurement signal;

a first filter communicably coupled to said detector and arranged to filter said measurement signal, said first filter having a first filter output;

a second filter communicably coupled to said detector and arranged to filter said measurement signal, said second filter having a second filter output;

a signal processing unit adapted to determine at least one filter parameter value based at least partially from an analysis of said first and second filter outputs; and

a programmable measurement filter communicably coupled to said signal processing unit, said programmable measurement filter adapted to filter said measurement signal based upon said at least one filter parameter value determined by said signal processing unit.

21. The device according to claim 20, wherein said signal processing unit computes a difference between said first and second filter outputs to distinguish device movement from noise.

22. A device for a spatial positioning system comprising:

a signal processing unit;

at least one storage device communicably coupled to said at least one signal processing unit arranged to store a programmable measurement filter program code;

programmable measurement filter program code stored on said storage device and executable by said signal processing unit for;

receiving an measurement signal;

analyzing said measurement signal to discriminate between noise and actual detected movement of said device and computing a tuning output therefrom;

computing at least one filter parameter value based upon said tuning output;

using said at least one filter parameter value to program a programmable measurement filter;

filtering said measurement signal with said programmable measurement filter;

outputting at least one of a filtered measurement signal and a control signal derived from said filtered measurement signal; and

at least one of a display unit and a control unit communicably coupled to said signal processing unit.

23. The device according to claim 22, wherein said tuning output is computed by taking magnitude of the difference between two filtered outputs of said measurement signal where each of said two filtered outputs is provided from one of two filters having at least one different filter characteristic.

24. The device according to claim 23, wherein said two filters comprise a median filter and a lowpass filter.

25. The device according to claim 22, wherein said programmable measurement filter implements a lowpass filter and said tuning output is used to compute said filter parameter value such that a cutoff frequency of said lowpass filter varies generally linearly with said tuning signal.

26. The device according to claim 22, wherein said programmable measurement filter implements a lowpass filter and said tuning output is used to compute said filter parameter value such that said filter parameter value varies generally linearly with said tuning signal.

27. The device according to claim 22, wherein said tuning output is computed such that said programmable measurement filter is adjustable across a predetermined operational range.

28. The device according to claim 27, wherein said predetermined operational range is based at least partly upon a variance in noise of a measurement of said input signal.

29. The device according to claim 22, wherein said programmable measurement filter is implemented as an infinite impulse response filter.

30. The device according to claim 29, wherein said programmable measurement filter is implemented as a second order filter.

31. A method of filtering a measurement signal in a device for a spatial positioning system comprising:

analyzing a measurement signal from a detector of said device;

determining a likelihood that said measurement signal represents device movement compared to noise;

determining at least one filter characteristic based upon said likelihood;

automatically tuning a programmable measurement filter based upon said at least one filter characteristic; and

filtering said measurement signal using said programmable measurement filter.

32. A method of filtering a measurement signal in a device for a spatial positioning system comprising:

providing a detector adapted to detect a measurement signal;

communicably coupling a signal processing unit to said detector;

analyzing said measurement signal to determine a likelihood that said measurement signal represents device movement compared to noise and assigning said at least one filter parameter value based upon said likelihood;

providing a programmable measurement filter adapted to receive and filter said measurement signal;

tuning said programmable measurement filter based upon said at least one filter parameter value determined by said signal processing unit.

33. The method according to claim 32, further comprising selecting said filter parameter value based upon an attempt to discriminate device movement from noise in said measurement signal.

34. The method according to claim 32, wherein said at least one filter parameter value is selected such that a frequency characteristic of said programmable measurement filter varies linearly within a predetermined operational range.

35. The method according to claim 32, wherein said at least one filter parameter value varies linearly within a predetermined operational range.

36. The method according to claim 32, wherein said at least one parameter value is selected such that said programmable measurement filter implements a low pass filter having a first cutoff frequency in response to detected device movement and a second cutoff frequency different from said first cutoff frequency in response to detected noise.

37. A method of filtering a measurement signal in a device for a spatial positioning system comprising:

providing a detector adapted to provide a measurement signal;

communicably coupling a first filter to said detector and arranged to filter said measurement signal, said first filter having a first filter output;

communicably coupling a second filter to said detector and arranged to filter said measurement signal, said second filter having a second filter output;

analyzing said first and second filter outputs to derive at least one filter parameter; and

tuning a programmable measurement filter arranged to filter said measurement signal with said at least one filter parameter value.

38. The method according to claim 37, wherein said analysis comprises computing the magnitude of the difference of said first and second filter outputs to distinguish device movement from noise.

39. A device for a spatial positioning system comprising:

a detector adapted to provide a measurement signal;

a first processor communicably coupled to said detector, said first processor adapted to process said measurement signal and derive a tuning signal output that dynamically changes in response to predetermined conditions;

a programmable measurement filter communicably coupled to said first processor, said programmable measurement filter adapted to filter said measurement signal based upon said tuning signal output to produce a measurement filter output;

a control application communicably coupled to said device, said control application adapted to receive at least one of said tuning signal output and said measurement filter output and to compensate for phase lag changes of said measurement signal.

40. The device according to claim 39, wherein said control application uses at least one of said measurement signal and said tuning signal to selectively switch among at least two control feedbacks.

41. The device according to claim 39, wherein said control application uses at least one of said measurement signal and said tuning signal to selectively tune a continuously variable feedback.

42. The device according to claim 39, wherein the output of two or more controllers controllably coupled to said control application may be added in proportion to the selection of said at least one of said measurement signal and said tuning signal.

43. The device according to claim 39, wherein said control application implements a proportional-integral-derivative control algorithm and at least one of said tuning signal and said position signal are used by said control application to switch one or more proportional-integral-derivative control algorithm constants to compensate for changes in phase lag of the system.

44. The device according to claim 43, wherein at least one of said tuning signal and position signal are used by the control application to dynamically adjust said proportional-integral-derivative control algorithm so as to control the proportional gain of the algorithm.