System and method for navigation using two-way ultrasonic positioning

• US 6,674,687 B2
• Filed: 01/25/2002
• Issued: 01/06/2004
• Est. Priority Date: 01/25/2002
• Status: Active Grant

• Current Assignee: Deere & Company
• Original Assignee: Navcom Technology, Inc. (Deere & Company)
• Inventors: Zeitzew, Michael A.
• Primary Examiner(s): Pihulic, Daniel T.
• Application Number:
  US10/057,662
• Publication Number:
  US 20030142587A1
• Time in Patent Office: 711 Days
• Field of Search: 367/6, 367/13, 367/127, 367/128, 367/907
• US Class Current: 367/6
• CPC Class Codes: G01S 15/46 Indirect determination of position data
• CPC Class Codes: G01S 15/74 Systems using reradiation of acoustic waves, e.g. IFF, i.e. identification of friend or foe
• CPC Class Codes: G01S 2015/465 by Trilateration, i.e. two transducers determine separately the distance to a target, whereby with the knowledge of the baseline length, i.e. the distance between the transducers, the position data of the target is determined
• CPC Class Codes: G01S 7/52004 Means for monitoring or calibrating short-range imaging G01S7/5205
• CPC Class Codes: G01S 7/52006 with provision for compensating the effects of temperature
• CPC Class Codes: G05D 1/0221 involving a learning process
• CPC Class Codes: G05D 1/0255 using acoustic signals, e.g. ultra-sonic singals sonar systems designed for anti-collision purposes G01S15/93
• CPC Class Codes: G05D 1/027 comprising intertial navigation means, e.g. azimuth detector inertial navigation G01C21/16; inertial navigation combined with non-inertial navigation instruments G01C21/165
• CPC Class Codes: G05D 1/0272 comprising means for registering the travel distance, e.g. revolutions of wheels measuring distance traversed on the ground by vehicles, e.g. using odometers G01C22/00
• CPC Class Codes: G05D 1/0274 using mapping information stored in a memory device navigation using map-matching G01C21/30
• CPC Class Codes: G05D 1/028 using a RF signal

Abstract

A two-way ultrasonic positioning and navigation system and method involve a plurality of objects each capable of transmitting and receiving ultrasonic signals. A first object transmits an initiating ultrasonic signal and identifies a second object for responding to the initiating ultrasonic signal. The second object transmits a responding ultrasonic signal after a predetermined time delay from receiving the initiating ultrasonic signal. The first objectives the responding ultrasonic signal, and determines a distance between the first object and the second object based on a time period starting at the transmission of the initiating ultrasonic signal and ending at the reception of the responding ultrasonic signal, and on knowledge about the predetermined time delay and other known in advance time delays.

Claims

1. A method of operating a positioning system having a plurality of objects each configured to transmit and receive ultrasonic signals, comprising

transmitting an initiating ultrasonic signal from a first one of the plurality of objects, the initiating ultrasonic signal including a code identifying one or both of the first one and a second one of the plurality of objects;

transmitting a responding ultrasonic signal from the second one of the plurality of objects after a predetermined time delay from receiving the initiating ultrasonic signal at the second one of the plurality of objects;

receiving the responding ultrasonic signal at the first one of the plurality of objects; and

determining a distance between the first one and the second one of the plurality of objects based on a time of transmitting the initiating ultrasonic signal, a time of receiving the responding ultrasonic signal, and the predetermined time delay.

2. The method of claim 1 wherein the first one of the plurality of objects includes an ultrasonic transceiver or transducer coupled to a matched filter, and wherein receiving the responding ultrasonic signal at the first one of the plurality of objects comprises:

producing a series of output values from the matched filter and determining a maximum output value among the series of output values; and

determining the time of receiving the responding ultrasonic signal based on a time when the maximum output value is produced.

3. The method of claim 1 wherein the second one of the plurality of objects includes multiple ultrasonic transceivers or transducer pairs facing different directions, and transmitting the responding ultrasonic signal comprises:

determining a figure of merit for each ultrasonic transceiver or transducer pair receiving the initiating ultrasonic signal; and

transmitting the responding ultrasonic signal from the ultrasonic transceiver or transducer pair having a highest figure of merit.

4. The method of claim 3 wherein each of the multiple ultrasonic transceivers or transducer pairs is coupled to a matched filter and wherein determining the figure of merit for an ultrasonic transceiver or transducer pair receiving the initiating ultrasonic signal comprises:

producing a series of output values from the matched filter coupled to the ultrasonic transceiver or transducer pair receiving the initiating ultrasonic signal; and

determining the figure of merit based on a maximum output value among the series of output values.

5. The method of claim 1 wherein the responding ultrasonic signal is encoded to identify one or both of the first one and the second one of the plurality of objects.

26. The method of claim 1, wherein the first one of the plurality of objects includes multiple ultrasonic transducers or transceivers and the initiating ultrasonic signal is transmitted by different ultrasonic transducers or transceivers in different directions.

27. The method of claim 1, wherein the first one of the plurality of objects includes multiple ultrasonic transducers or transceivers each coupled to a matched filter, and wherein receiving the responding ultrasonic signal at the first one of the plurality of objects comprises:

for each ultrasonic transducer or transceiver receiving the responding ultrasonic signal, producing a series of output values from the matched filter coupled to the ultrasonic transducer or transceiver and determining a maximum output value for the ultrasonic transducer or transceiver among the series of output values;

determining a highest maximum output value among the maximum output values determined for the ultrasonic transducers or transceivers receiving the responding ultrasonic signal; and

determining the time of receiving the responding ultrasonic signal based on a time when the highest maximum output value is produced.

6. A method of operating a positioning system having a plurality of objects each configured to transmit and receive ultrasonic signals, comprising

transmitting an initiating ultrasonic signal from a first one of the plurality of objects, the initiating ultrasonic signal being accompanied by a radio frequency signal triggering a second one of the plurality of objects to receive the initiating ultrasonic signal;

transmitting a responding ultrasonic signal from the second one of the plurality of object;

receiving the responding ultrasonic signal at the first one of the plurality of objects; and

determining a distance between the first one and the second one of the plurality of objects based on a time period starting at the transmission of said initiating ultrasonic signal and ending at the reception of said responding ultrasonic signal.

7. The method of claim 6 wherein the second one of the plurality of objects transmits the responding ultrasonic signal after a time delay from receiving the initiating ultrasonic signal.

8. The method of claim 7, wherein the radio frequency signal includes information for the time delay.

9. The method of claim 6 wherein the radio frequency signal is coded to identify one or both of the first one and the second one of the plurality of objects.

10. The method of claim 6 wherein the responding ultrasonic signal is accompanied by a radio frequency signal identifying one of both of the first one and the second one of the plurality of objects.

11. An ultrasonic positioning system, comprising:

a plurality of objects each configured to transmit and receive ultrasonic signals, a number of the plurality of objects being greater than 2;

a first ultrasonic array positioned on a first one of the plurality of objects and configured to transmit initiating ultrasonic signals, each initiating ultrasonic signal including a code that identifies another one of the plurality of objects for responding to the initiating ultrasonic signal;

a second ultrasonic array positioned on a second one of the plurality of objects and configured to respond to an initiating ultrasonic signal coded to identify the second one of the plurality of objects by transmitting a responding ultrasonic signal after a predetermined time delay from receiving an initiating ultrasonic signal; and

wherein the first ultrasonic array is configured to receive the responding ultrasonic signal, and is coupled to a timer that records a time of transmitting the initiating ultrasonic signal and a time of receiving the responding ultrasonic signal; and

wherein the first ultrasonic array is also coupled to a processor that determines a distance between the first one and the second one of the plurality of objects based on the recorded times, and the predetermined time delay.

12. The system of claim 11, wherein the first ultrasonic array includes a plurality of ultrasonic transceivers or transducer pairs facing different directions.

13. The system of claim 11, wherein the responding ultrasonic signal is encoded to identify the object from which the responding ultrasonic signal is transmitted.

14. The system of claim 12, wherein the plurality of ultrasonic transceivers or transducer pairs are divided into groups of ultrasonic transceivers or transducer pairs and different groups of ultrasonic transceivers or transducer pairs are configured to transmit initiating ultrasonic signals at different times and in different directions.

15. The system of claim 11, wherein the processor is configured to calculate a speed of sound based on the recorded times and the predetermined time delay.

16. The system of claim 15, further comprising:

temperature and humidity sensors coupled to the processor for providing temperature and humidity readings that are used by the processor to calculated the speed of sound.

17. The system of claim 15 wherein the first one of the plurality of objects is a mobile platform to be positioned and the second one of the plurality of objects is one of a plurality of beacons at fixed locations.

18. The system of claim 17 wherein the speed of sound is determined by inter-beacon ultrasonic measurements or ultrasonic measurements between the platform and a plurality of beacons.

28. The system of claim 11, further comprising:

a matched filter coupled to each ultrasonic transceiver or transducer pair in the second ultrasonic array, the matched filter configured to produce an output value in response to an arrival of the initiating ultrasonic signal at the ultrasonic transceiver or transducer pair, wherein the output value is compared with a threshold to detect a reception of the initiating ultrasonic signal by the ultrasonic transceiver or transducer pair.

29. The system of claim 28, wherein the matched filter is configured to produce a series of output values in response to the reception of the initiating ultrasonic signal by the transceiver, and the processor is configured to select a maximum value among the series of output values as a figure of merit for the received initiating ultrasonic signal.

19. An ultrasonic positioning system, comprising:

a plurality of objects each configured to transmit and receive ultrasonic signals;

a first ultrasonic array positioned on a first one of the plurality of objects and configured to transmit initiating ultrasonic signals;

a radio transmitter positioned on the first one of the plurality of objects and configured to transmit a radio frequency signal with each initiating ultrasonic signal to trigger another one of the plurality of objects to respond to the initiating ultrasonic signal;

a radio receiver positioned on a second one of the plurality of objects and configured to receive radio frequency signals; and

a second ultrasonic array positioned on the second one of the plurality of objects and configured to receive initiating ultrasonic signals and to transmit a responding ultrasonic signal in response to receiving an initiating ultrasonic signal that follows a radio frequency signal triggering the second one of the plurality of objects to respond to the initiating ultrasonic signal; and

wherein the first ultrasonic array is configured to receive the responding ultrasonic signal, and is coupled to a timer that records a time period between the transmission of the initiating ultrasonic signal and the reception of the responding ultrasonic signal.

20. The system of claim 19, further comprising a radio transmitter positioned on the second one of the plurality of objects, and configured to transmit a radio frequency signal with the responding ultrasonic signal to acknowledge receipt of the initiating ultrasonic signal by the second one of the plurality of objects.

21. The system of claim 19 wherein the ultrasonic array on the second one of the plurality of objects transmits the responding ultrasonic signal after a time delay from receiving the initiating ultrasonic signal that follows the radio frequency signal triggering the second one of the plurality of objects to respond to the initiating ultrasonic signal.

22. The system of claim 21 wherein the radio frequency signal further includes information of the time delay.

23. The system of claim 19, wherein the first one of the plurality of objects is a mobile platform to be positioned and the second one of the plurality of objects is one of a plurality of beacons at fixed locations.

24. A method for calibrating a positioning system having a plurality of beacons, comprising

placing the beacons in or around a service volume according to a set of predetermined constraints;

determining a set of inter-beacon distances using inter-beacon 2-way ultrasonic measurements;

setting the origin of a coordinate frame at a first beacon;

setting one axis of the coordinate frame along the direction from the first beacon and a second beacon;

determining initial coordinates of the second beacon based on the distance between the first beacon and the second beacon;

determining initial coordinates of a third beacon based on the distances between the first beacon and the second beacon, between the second beacon and the third beacon, and between the third beacon and the first beacon, and based on the predetermined constraints.

25. The method of claim 24, further comprising:

iteratively improving the initial coordinates to obtain final coordinates for the beacons.

30. A mobile platform capable of positioning itself with respect to a plurality of beacons in fixed locations, comprising:

an ultrasonic array including a first set of ultrasonic transceivers or transducer pairs, the first set of ultrasonic transceivers or transducer pairs configured to transmit simultaneously a first set of initiating ultrasonic signals in different directions to poll a beacon;

a timer coupled to the ultrasonic array and configured to record a time of transmitting the first set of initiating ultrasonic signals by the first set of ultrasonic transceivers or transducer pairs and a time of receiving a responding ultrasonic signal from the beacon by one of the first set of ultrasonic transceivers or transducer pairs; and

a processor coupled to the timer and configured to determine a distance between the mobile platform and the beacon based on the time of transmitting the first set of initiating ultrasonic signals and the time of receiving the responding ultrasonic signal.

31. The mobile platform in claim 30 wherein the ultrasonic array further includes a second set of ultrasonic transceivers or transducer pairs, the second set of ultrasonic transceivers or transducer pairs configured to transmit a second set of initiating ultrasonic signals to poll the beacon subsequent to the transmission of the first set of initiating the ultrasonic signals, the second set of ultrasonic signals being transmitted in different directions from those in which the first set of ultrasonic signals have been transmitted.

32. The mobile platform in claim 30 wherein each initiating ultrasonic signal is coded to identify the beacon.

33. The mobile platform in claim 30 wherein each initiating ultrasonic signal is coded to identify the ultrasonic transceiver or transducer pair from which it is transmitted.

34. The mobile platform in claim 30, further comprising a matched filter coupled to each ultrasonic transceiver or transducer pair, the matched filter configured to produce output values in response to an arrival of the responding ultrasonic signal at the ultrasonic transceiver or transducer pair, wherein the processor is configured to compare the output values with a threshold value to detect a reception of the responding ultrasonic signal by the ultrasonic transceiver or transducer pair.

35. The mobile platform in claim 34 wherein the processor is configured to produce a figure of merit for the ultrasonic transceiver or transducer pair based on the output values when a reception of the responding ultrasonic signal is detected.

36. The mobile platform in claim 35, wherein the processor is further configured to determine the time of receiving the responding ultrasonic signal based on the figure of merit produced by the matched filter coupled to an ultrasonic transceiver or transducer pair receiving the responding ultrasonic signal.

37. The mobile platform in claim 30, further comprising a radio frequency transmitter coupled to the ultrasonic array and configured to transmit a radio frequency signal with the first set of ultrasonic signals to trigger the beacon to respond to at least one of the first set of ultrasonic signals.

38. A mobile platform capable of positioning itself with respect to a plurality of beacons, comprising

an ultrasonic array configured to transmit a sequence of initiating ultrasonic signals to poll a beacon, the sequence of initiating ultrasonic signals including a first initiating ultrasonic signal transmitted in a first direction and a second initiating ultrasonic signal transmitted in a second direction different from the first direction, wherein the ultrasonic array is further configured to receive from the beacon a first responding ultrasonic signal corresponding to the first initiating ultrasonic signal and a second responding ultrasonic signal corresponding to the second initiating ultrasonic signal;

a timer coupled to the ultrasonic array and configured to record a time of transmitting the first initiating ultrasonic signal, a time of receiving the first responding ultrasonic signal, a time of transmitting the second ultrasonic signal, and a time of receiving the second responding ultrasonic signal; and

a processor coupled to the timer and configured to determine a distance between the mobile platform and the beacon based on a shorter one of a first time period and a second time period, wherein the first time period is between the time of transmitting the first initiating ultrasonic signal and the time of receiving the first responding ultrasonic signal, and the second time period is between the time of transmitting the second initiating ultrasonic signal and the time of receiving the second responding ultrasonic signal.

39. The method of claim 38 wherein the ultrasonic array includes a plurality of ultrasonic transceivers or transducer pairs facing different directions.

40. The method of claim 38, further comprising a radio transmitter coupled to the ultrasonic array and configured to transmit a radio frequency signal with each of the first and the second initiating ultrasonic signals to trigger the beacon to respond to the initiating ultrasonic signal.

41. A beacon for positioning a mobile platform, comprising:

an ultrasonic array including multiple ultrasonic transceivers or transducer pairs facing different directions, each ultrasonic transceiver or transducer pair configured to transmit and receive ultrasonic signals;

a matched filter coupled to each ultrasonic transceiver or transducer pair, and the matched filter configured to detect a reception of an ultrasonic signal by the ultrasonic transceiver or transducer pair and to produce a figure of merit when a reception is detected; and

a processor coupled to the ultrasonic array and configured to select an ultrasonic transceiver or transducer pair to respond to the ultrasonic signal based on the figure of merit produced by the matched filter coupled to each ultrasonic transceiver or transducer pair receiving the ultrasonic signal.

42. A mobile platform capable of positioning itself with respect to a plurality of beacons using ultrasonic signals, comprising:

an ultrasonic array configured to transmit and receive ultrasonic signals; and

a radio transmitter configured to transmit a radio frequency signal associated with each of some or all of the ultrasonic signals transmitted by the ultrasonic array, the radio frequency signal triggering one or more of the plurality of beacons to receive the associated ultrasonic signal.

43. The mobile platform of claim 42 wherein the ultrasonic array includes multiple ultrasonic transceivers or transducer pairs, and the radio frequency signal includes a code identifying at least one ultrasonic transceiver or transducer pair.

44. The mobile platform of claim 43 wherein the multiple ultrasonic transceivers or transducer pairs face different directions.

45. The mobile platform of claim 42 wherein the radio frequency signal includes a code identifying the one or more of the plurality of beacons for receiving the ultrasonic signal.

46. A beacon for positioning a mobile platform, comprising:

an ultrasonic array configured to transmit and receive ultrasonic signals; and

a radio transmitter configured to transmit a radio frequency signal associated with each of some or all of the ultrasonic signals transmitted by the ultrasonic array, the radio frequency signal triggering the mobile platform to receive the associated ultrasonic signal.

47. A method of operating a positioning system having a plurality of objects each configured to transmit and receive ultrasonic signals, comprising

from a first one of the plurality of objects, transmitting simultaneously a set of initiating ultrasonic signals for receipt by a second one of the plurality of objects, the set of initiating ultrasonic signals including ultrasonic signals transmitted in different directions;

transmitting a responding ultrasonic signal from the second one of the plurality objects after a predetermined time delay from receiving one initiating ultrasonic signal by the second one of the plurality of objects, the one initiating ultrasonic signal being the first among the set of initiating ultrasonic signals to arrive at the second one of the plurality of objects;

receiving the responding ultrasonic signal at the first one of the plurality of objects; and

determining a distance between the first one and the second one of the plurality of objects based on a time of transmitting the set of initiating ultrasonic signal, a time of receiving the responding ultrasonic signal, and the predetermined time delay.

48. The method of claim 47 wherein the second one of the plurality of objects includes multiple ultrasonic transceivers or transducer pairs facing different directions, and transmitting the responding ultrasonic signal comprises:

determining a figure of merit for each ultrasonic transceiver or transducer pair receiving the one initiating ultrasonic signal; and

transmitting the responding ultrasonic signal from the ultrasonic transceiver or transducer pair having a highest figure of merit.

49. The method of claim 48, wherein each of the multiple ultrasonic transceivers or transducer pairs is coupled to a matched filter and wherein determining the figure of merit for an ultrasonic transceiver or transducer pair receiving the first initiating ultrasonic signal comprises:

producing a series of output values from the matched filter coupled to the ultrasonic transceiver or transducer pair receiving the one initiating ultrasonic signal; and

determining the figure of merit based on a maximum output value among the series of output values.

50. The method of claim 49, further comprising transmitting a radio frequency signal with the set of initiating ultrasonic signals to trigger the second one of the plurality of objects to respond to the one initiating ultrasonic signal.

51. A method of operating a positioning system having a plurality of objects each configured to transmit and receive ultrasonic signals, comprising

transmitting a first initiating ultrasonic signal in a first direction from a first one of the plurality of objects;

in response to receiving the first initiating ultrasonic signal by a second one of the plurality of objects, transmitting a first responding ultrasonic signal from the second one of the plurality of objects;

receiving the first responding ultrasonic signal at the first one of the plurality of objects;

computing a first time period starting at a time of transmitting the first initiating ultrasonic signal and ending at a time of receiving the first responding ultrasonic signal;

subsequent to transmitting the first initiating ultrasonic signal, transmitting a second initiating ultrasonic signal in a second direction from the first one of the plurality of objects, the second direction being different from the first direction;

in response to receiving the second initiating ultrasonic signal by the second one of the plurality of objects, transmitting a second responding ultrasonic signal from the second one of the plurality of objects;

receiving the second responding ultrasonic signal at the first one of the plurality of objects;

computing a second time period starting at a time of transmitting the second initiating ultrasonic signal and ending at a time of receiving the second responding ultrasonic signal; and

determining a distance between the first one and the second one of the plurality of objects based on a shorter one of the first time period and the second time period.

52. The method of claim 51 wherein each of the first and the second initiating ultrasonic signals includes a code identifying one or both of the first and the second one of the plurality of objects.

53. The method of claim 51 wherein the first or the second responding ultrasonic signal is transmitted after a predetermined time delay from when the first or the second initiating ultrasonic signal, respectively, is received at the second one of the plurality of objects.

54. The method of claim 51, further comprising transmitting a radio frequency signal with each of the first and the second ultrasonic signals to trigger the second one of the plurality of objects to respond to the initiating ultrasonic signal.

55. The method of claim 51 wherein the first initiating ultrasonic signal is one of a plurality of ultrasonic signals transmitted simultaneously and in a first plurality of directions from the first one of the plurality of objects, the first plurality of directions being different from the second direction, and the first initiating ultrasonic signal is the first among the plurality of ultrasonic signals to arrive at the second one of the plurality of objects.