Apparatus and method for determining boring direction when boring underground

• US 5,880,680 A
• Filed: 12/06/1996
• Issued: 03/09/1999
• Est. Priority Date: 12/06/1996
• Status: Expired due to Term

• Current Assignee: Charles Machine Works Incorporated The
• Original Assignee: Charles Machine Works Incorporated The
• Inventors: Wisehart, John C., Jin, Jian, Widener, Austin L.
• Primary Examiner(s): Horabik, Michael
• Assistant Examiner(s): Edwards, Jr., Timothy
• Application Number:
  US08/759,656
• Time in Patent Office: 823 Days
• Field of Search: 73/152.43, 73/152.44, 73/152.45, 73/152.46, 175/26, 175/45, 175/61, 340/853.1, 340/853.3, 340/853.5, 340/853.6, 340/853.4
• US Class Current: 340/853.4
• CPC Class Codes: E21B 47/024 of devices in the borehole determining slope or direction of the borehole E21B47/022

Abstract

A guidance module for an underground horizontal boring assembly. The module determines the pitch angle of the boring tool independent of roll using a single accelerometer sensor. The accelerometer sensor has a single sensitive axis which is aligned parallel to, and preferably coaxial with, the longitudinal axis of the boring tool. The accelerometer sensor is calibrated to obtain a temperature offset and a gain compensating gain factor. Data samples are read from the accelerometer sensor while the boring tool is rotating. The temperature is read from the temperature sensor. The data samples from the accelerometer sensor and the temperature from the temperature sensor are transmitted to a processor. The processor applies simple average filtering to the accelerometer data samples to get an average result, and adjusts the average result for gain. The average result is adjusted for the temperature offset and for the gain compensating gain factor. The average result then can be adjusted for an optional roll angle offset. The pitch angle is determined either from a lookup table or from the arcsin value of the quantity of the average result minus the temperature offset divided by the gain compensating gain factor.

Claims

1. A guidance module for use in the boring tool of a horizontal underground boring assembly, wherein the boring assembly includes an output device for presenting directional information received from the guidance module and wherein the boring tool has a longitudinal axis, the module comprising:

an accelerometer sensor having a single sensitive axis which is aligned parallel to the boring tool axis, the accelerometer sensor adapted to sense a plurality of pitch data samples of the boring tool between a horizontal plane and the axis of the boring tool and to transmit the pitch data samples in a pitch signal;

a temperature sensor adapted to measure temperature near the accelerometer and to transmit the temperature in a temperature signal; and

a processor adapted to receive the pitch signal from the accelerometer sensor and the temperature signal from the temperature sensor, to process the temperature in the temperature signal to determine a temperature offset, to process the pitch data samples from the pitch signal with the temperature offset to determine a pitch angle, and to transmit an output signal containing the pitch angle to the output device.

2. The guidance module of claim 1 wherein the module contains only one accelerometer sensor.

3. The guidance module of claim 1 further comprising an input interface adapted to accept processor input signals from an external source and to transmit the processor input signals to the processor.

4. The guidance module of claim 1 further comprising a memory adapted to store data and to transmit the data between the processor and the memory.

5. The guidance module of claim 1 further comprising a memory adapted to store programming and to transmit the programming between the processor and the memory.

6. The guidance module of claim 1 further comprising an output interface adapted to receive the output signal from the processor and to output the output signal to the output device.

7. The guidance module of claim 1 wherein the temperature signal is in an analog format and wherein the module further comprises a converter adapted to receive the temperature signal from the temperature sensor, to convert the temperature signal to a digital format, and to transmit the temperature signal in the digital format to the processor.

8. The guidance module of claim 1 wherein the pitch signal is in an analog format and wherein the module further comprises a converter adapted to receive the pitch signal from the accelerometer sensor, to convert the pitch signal to a digital format, and to transmit the pitch signal in the digital format to the processor.

9. The guidance module of claim 1 wherein the guidance module further comprises a roll sensor adapted to measure a roll angle of the boring tool and to transmit roll angle data in a roll angle signal to the processor and wherein the processor is adapted to process the roll angle data to determine a roll angle offset and to process the pitch data samples with the roll angle offset to determine the pitch angle.

10. The guidance module of claim 9 wherein the roll angle data is in an analog format and wherein the guidance module further comprises a converter adapted to receive the roll angle data from the roll sensor, to convert the roll angle data to a digital format, and to transmit the roll angle data in the digital format to the processor.

11. A boring tool for use in a horizontal underground boring assembly, wherein the boring assembly includes an output device for presenting directional information received from the boring tool and wherein the boring tool has a longitudinal axis, the boring tool comprising:

a guidance module installed in the boring tool, the module comprising;

an accelerometer sensor having a single sensitive axis which is aligned parallel to the boring tool axis, the accelerometer sensor adapted to sense a plurality of pitch data samples of the boring tool between a horizontal plane and the axis of the boring tool and to transmit the pitch data samples in a pitch signal;

a temperature sensor adapted to measure temperature near the accelerometer and to transmit the temperature in a temperature signal; and

a processor adapted to receive the pitch signal from the accelerometer sensor and the temperature signal from the temperature sensor, to process the temperature in the temperature signal to determine a temperature offset, to process the pitch data samples from the pitch signal with the temperature offset to determine a pitch angle, and to transmit an output signal containing the pitch angle to the output device.

12. The boring tool of claim 11 wherein the guidance module contains only one accelerometer sensor.

13. The boring tool of claim 11 wherein the guidance module further comprises an input interface adapted to accept processor input signals from an external source and to transmit the processor input signals to the processor.

14. The boring tool of claim 11 wherein the guidance module further comprises a memory adapted to store data and to transmit the data between the processor and the memory.

15. The boring tool of claim 11 wherein the guidance module further comprises a memory adapted to store programming and to transmit the programming between the processor and the memory.

16. The boring tool of claim 11 wherein the guidance module further comprises a roll sensor adapted to measure a roll angle of the boring tool and to transmit roll angle data in a roll angle signal to the processor and wherein the processor is adapted to process the roll angle data to determine a roll angle offset and to process the pitch data samples with the roll angle offset to determine the pitch angle.

17. The boring tool of claim 11 wherein the guidance module further comprises an output interface adapted to receive the output signal from the processor and to output the output signal to the output device.

18. The boring tool of claim 11 wherein the temperature signal is in an analog format and wherein the guidance module further comprises a converter adapted to receive the temperature signal from the temperature sensor, to convert the temperature signal to a digital format, and to transmit the temperature signal in the digital format to the processor.

19. The apparatus of claim 11 wherein the pitch signal is in an analog format and wherein the guidance module further comprises a converter adapted to receive the pitch signal from the accelerometer sensor, to convert the pitch signal to a digital format, and to transmit the pitch signal in the digital format to the processor.

20. A boring assembly for underground horizontal boring, comprising:

a boring tool having a longitudinal axis, wherein the boring tool comprises;

a guidance module, comprising;

an accelerometer sensor having a single sensitive axis which is aligned parallel to with the boring tool axis, the accelerometer sensor adapted to sense a plurality of pitch data samples of the boring tool between a horizontal plane and the axis of the boring tool and to transmit the pitch data samples in a pitch signal;

a temperature sensor adapted to measure temperature near the accelerometer and to transmit the temperature in a temperature signal; and

a processor adapted to receive the pitch signal from the accelerometer sensor and the temperature signal from the temperature sensor, to process the temperature in the temperature signal to determine a temperature offset, to process the pitch data samples from the pitch signal with the temperature offset to determine a pitch angle, and to transmit an output signal containing the pitch angle; and

a control system comprising;

a drive system adapted to drive the boring tool through the earth;

a steering system adapted to control the direction of the boring tool; and

an output device adapted to receive the output signal containing the pitch angle and to present the pitch angle.

21. The boring assembly of claim 20 wherein the guidance module in the boring tool comprises only one accelerometer sensor.

22. The boring assembly of claim 20 wherein the output device is adapted to display the pitch angle visually.

23. The boring assembly of claim 20 wherein the guidance module of the boring tool further comprises an input interface adapted to accept processor input signals from an external source and to transmit the processor input signals to the processor.

24. The boring assembly of claim 20 wherein the guidance module of the boring tool further comprises a memory adapted to store data and to transmit the data between the processor and the memory.

25. The boring assembly of claim 20 wherein the guidance module of the boring tool further comprises a roll sensor adapted to measure a roll angle of the boring tool and to transmit roll angle data in a roll angle signal to the processor and wherein the processor is adapted to process the roll angle data to determine a roll angle offset and to process the pitch data samples with the roll angle offset to determine the pitch angle.

26. The boring assembly of claim 20 wherein the temperature signal is in an analog format and wherein the guidance module in the boring tool further comprises a converter adapted to receive the temperature signal from the temperature sensor, to convert the temperature signal to a digital format, and to transmit the temperature signal in the digital format to the processor.

27. The boring assembly of claim 20 wherein the pitch signal is in an analog format and wherein the guidance module in the boring tool further comprises a converter adapted to receive the pitch signal from the accelerometer sensor, to convert the pitch signal to a digital format, and to transmit the pitch signal in the digital format to the processor.

28. The boring assembly of claim 20 wherein the guidance module of the boring tool further comprises an output interface adapted receive the output signal from the processor and to output the output signal to the control assembly.

29. The boring assembly of claim 28 wherein the output interface is adapted to transmit the output signal over a transmission line to the output device.

30. The boring assembly of claim 28 wherein the output interface comprises a radio frequency transmitter and is adapted to transmit the output signal from the radio frequency transmitter to the output device with a radio frequency signal.

31. A method for determining boring direction when boring underground with a boring assembly having a boring tool with a longitudinal axis, the method comprising:

sensing in an accelerometer sensor pitch data samples representative of a pitch angle of the boring tool between a horizontal plane and the axis of the boring tool;

sensing a temperature sample near the accelerometer;

determining a compensating gain factor;

determining a temperature offset using the temperature sample;

averaging the pitch data samples; and

processing the pitch data samples with the temperature offset and the compensating gain factor to determine a pitch angle.

32. The method of claim 31 wherein sensing the pitch data samples comprises sensing the pitch data samples with only one accelerometer sensor.

33. The method of claim 31 wherein the boring assembly includes an output device for presenting directional information, and wherein the method further comprises transmitting the pitch angle to the output device.

34. The method of claim 31 wherein the pitch data samples are in an analog format and wherein the method further comprises converting the pitch data samples to a digital format.

35. The method of claim 31 wherein the temperature sample is in an analog format and wherein the method further comprises converting the temperature sample to a digital format.

36. The method of claim 31 wherein processing the pitch data samples with the temperature offset and the gain calibrating offset to determine the pitch angle comprises:

subtracting the temperature offset and the compensating gain factor from the averaged data samples to get a result having a sign;

determining if the result is positive or negative;

removing the sign if the result is negative and setting the sign to negative;

leaving the sign if the result is positive and setting the sign to positive;

looking up a pitch angle in a pitch lookup table using the result as an index; and

multiplying the pitch angle by the sign.

37. The method of claim 31 wherein a number of data samples are sampled and wherein averaging the data samples comprises summing the data samples to get a summation and dividing the summation of the data samples by a value equal to the number of data samples that were sampled.

38. The method of claim 31 wherein the accelerometer sensor has a single sensitive axis and wherein the method further comprises aligning the single sensitive axis parallel to the boring tool axis before sensing in the accelerometer sensor.

39. The method of claim 38 wherein the method further comprises aligning the single sensitive axis coaxial with the boring tool axis before sensing in the accelerometer sensor.

40. The method of claim 31 further comprising:

sensing a roll angle sample of the boring tool;

determining a roll angle offset using the roll angle sample; and

processing the pitch data samples with the roll angle offset to determine the pitch angle.

41. The method of claim 40 wherein the roll angle sample is in an analog format and wherein the method further comprises converting the roll angle sample to a digital format.

42. The method of claim 31 further comprising calibrating the accelerometer sensor before sensing the pitch data samples.

43. The method of claim 42 wherein calibrating the accelerometer sensor comprises calibrating the accelerometer sensor with a temperature calibration mode and a gain calibration mode.

44. The method of claim 31 wherein averaging the data samples produces an average result and wherein determining the pitch angle comprises using the relationship wherein the pitch angle is equal to the arcsin of the quantity of the average result minus the temperature offset divided by the compensating gain factor.

45. The method of claim 44 wherein determining the pitch angle further comprises subtracting a roll angle offset.

46. A method for determining boring direction when boring underground with a boring tool having a longitudinal axis, the method comprising:

sensing with only one accelerometer sensor pitch data samples of the boring tool between a horizontal plane and the axis of the boring tool with a reference to a gravity vector, the only one accelerometer having a single sensitive axis; and

processing the pitch data samples to determine a pitch angle.

47. The method of claim 46 further comprises aligning the sensitive axis of the only one accelerometer sensor parallel to the axis of the boring tool before sensing with the only one accelerometer sensor.

48. The method of claim 46 further comprising:

sensing a temperature near the only one accelerometer sensor;

using the temperature to determine a temperature offset; and

processing the pitch data samples with the temperature offset to determine the pitch angle.

49. The method of claim 48 further comprising:

sensing a roll angle sample of the boring tool;

determining a roll angle offset using the roll angle sample; and

processing the pitch data samples with the roll angle offset to determine the pitch angle.

50. The method of claim 49 further comprising:

sensing a roll angle sample of the boring tool;

determining a roll angle offset using the roll angle sample; and

processing the pitch data samples with the roll angle offset to determine the pitch angle;

wherein determining the pitch angle comprises using the relationship wherein the pitch angle is equal to the arcsin of the quantity of the average result minus the temperature offset divided by the compensating gain factor minus the roll angle offset.

51. The method of claim 46 further comprising calibrating the only one accelerometer sensor to determine the compensating gain factor and a temperature offset.

52. The method of claim 51 wherein processing the pitch data samples to determine the pitch angle comprises:

averaging the data samples;

adjusting the data samples with the compensating gain factor;

adjusting the data samples with the temperature offset; and

determining a pitch angle after the data samples have been averaged, adjusted with the compensating gain factor, and adjusted with the temperature offset.

53. The method of claim 52 wherein processing the pitch data samples to determine the pitch angle further comprises:

subtracting the temperature offset and the compensating gain factor from the filtered data samples to get a result with a sign;

determining if the result is positive or negative;

removing the sign if the result is negative and setting the sign to negative;

leaving the sign if the result is positive and setting the sign to positive;

looking up a pitch angle in a pitch lookup table using the result as an index; and

multiplying the pitch angle by the sign.

54. The method of claim 52 wherein averaging the data samples produces an average result and wherein determining the pitch angle comprises using the relationship wherein the pitch angle is equal to the arcsin of the quantity of the average result minus the temperature offset divided by the compensating gain factor.

55. The method of claim 52 wherein a number of data samples are sampled and wherein averaging the data samples comprises summing the data samples to get a summation and dividing the summation of the data samples by a value of the number of data samples that were sampled.

56. A method for boring underground horizontally using a boring assembly comprising a boring tool with a longitudinal axis, the method comprising:

calibrating an accelerometer sensor;

reading a plurality of data samples from the accelerometer sensor;

sensing a temperature near the accelerometer sensor;

filtering the data samples;

adjusting the data samples with a compensating gain factor;

adjusting the data samples with a temperature offset;

determining a pitch angle after the data samples have been filtered, adjusted for the compensating gain factor, and adjusted with the temperature offset.

57. The method of claim 56 wherein only one accelerometer sensor reads the plurality of data samples.

58. The method of claim 56 wherein the boring assembly includes a control system which includes a steering system adapted to control the direction of the boring tool, and wherein the method further comprises:

transmitting to a control system the pitch angle in an output signal; and

adjusting the direction of the boring tool after receiving the output signal at the control system.

59. The method of claim 56 further comprising subtracting a roll offset from the data samples.

60. The method of claim 56 wherein adjusting the data samples with the temperature offset comprises subtracting a temperature offset from the data samples.

61. The method of claim 56 wherein adjusting the data samples for compensating gain factor comprises subtracting a compensating gain factor from the data samples.

62. The method of claim 56 wherein determining the pitch angle comprises:

subtracting a temperature offset and a compensating gain factor from the filtered data samples to get a result with a sign;

determining if the result is positive or negative;

removing the sign if the result is negative and setting the sign to negative;

leaving the sign if the result is positive and setting the sign to positive looking up a pitch angle in a pitch lookup table using the result as an index; and

multiplying the pitch angle by the sign.

63. The method of claim 56 wherein calibrating the accelerometer sensor on the boring tool to determine an offset comprises determining a compensating gain factor comprising:

reading a first sensor value at a maximum input position and a second sensor value at a minimum input position;

determining an sample peak value of the first sensor value and the second sensor value by dividing by two the quantity of the sensor value at the maximum accelerometer placement minus the sensor value at the minimum input position; and

storing the sample peak value in a memory as the compensating gain factor.

64. The method of claim 56 wherein the accelerometer sensor has a single sensitive axis and the method further comprises aligning the single sensitive axis of the accelerometer sensor parallel to the axis of the boring tool before calibrating the accelerometer sensor.

65. The method of claim 64 wherein the accelerometer sensor has a single sensitive axis and the method further comprises aligning the single sensitive axis of the accelerometer sensor coaxial with the axis of the boring tool before calibrating the accelerometer sensor.

66. The method of claim 56 wherein determining the pitch angle comprises using the relationship wherein the pitch angle is equal to the arcsin of the quantity of the average result minus the temperature offset divided by the compensating gain factor.

67. The method of claim 66 further comprising:

sensing a roll angle sample of the boring tool;

determining a roll angle offset using the roll angle sample; and

processing the pitch data samples with the roll angle offset to determine the pitch angle;

wherein determining the pitch angle comprises using the relationship wherein the pitch angle is equal to the arcsin of the quantity of the average result minus the temperature offset divided by the compensating gain factor minus the roll angle offset.

68. The method of claim 56 wherein calibrating the accelerometer sensor on the boring tool to determine an offset comprises determining the temperature offset comprising:

placing the accelerometer sensor in a heating/cooling unit with a temperature sensor;

setting a temperature in the heating/cooling unit to a value;

reading the temperature from the temperature sensor;

reading a data sample from the accelerometer sensor if the temperature from the temperature sensor is at a temperature index; and

storing the data sample from the accelerometer in a memory and indexing the stored data sample by the temperature from the temperature sensor.

69. The method of claim 68 further comprising:

increasing the temperature in the heating/cooling unit;

determining if the heating/cooling unit has reached a maximum temperature;

incrementing the temperature index if the heating/cooling unit has not reached the maximum temperature;

reading the temperature from the temperature sensor if the heating/cooling unit has not reached the maximum temperature;

reading a data sample from the accelerometer sensor if the temperature from the temperature sensor is at the incremented temperature index and if the heating/cooling unit has not reached the maximum temperature;

storing the data sample from the accelerometer in a memory and indexing the stored data sample by the temperature from the temperature sensor if the heating/cooling unit has not reached the maximum temperature; and

ending the temperature calibration if the heating/cooling unit has reached the maximum temperature.

70. The method of claim 56 wherein calibrating the accelerometer sensor on the boring tool to determine an offset comprises determining a roll angle offset comprising:

setting the boring tool to a roll angle index point;

reading a roll sensor to determine a roll angle offset; and

storing the roll angle offset by the index point in a memory.

71. The method of claim 70 further comprising:

determining if the boring tool is set at a final index point;

setting the boring tool at a next roll angle index point if the boring tool is not set at the final index point;

reading the roll sensor to determine the roll angle if the boring tool is not set at the final index point;

storing the roll angle offset by the index point in the memory if the boring tool is not set at the final index point; and

ending the roll angle calibration if the boring tool is set at the final index point.

72. The method of claim 56 wherein calibrating the accelerometer sensor comprises:

reading a first sensor value at a maximum input position and a second sensor value at a minimum input position;

determining an sample peak value of the first sensor value and the second sensor value;

determining a zero offset of the first sensor value and the second sensor value;

obtaining a gain reference setpoint;

obtaining a reference peak value;

determining a weighted sample peak value;

comparing the sample peak value to the reference peak value; and

adjusting the gain reference setpoint to a compensating gain setpoint and adjusting the zero offset to a compensating gain factor if the reference peak value is not equal to the sample peak value.

73. The method of claim 72 wherein reading a plurality of data samples comprises reading a number of data samples that is equal to the compensating gain setpoint.

74. The method of claim 72 wherein filtering the sensor input signals comprises summing the plurality of data samples to get a summation and dividing the summation of the data samples by the compensating gain setpoint.

75. The method of claim 72 further comprising raising the gain reference setpoint to a compensating gain setpoint and raising the zero offset to a compensating gain factor if the reference peak value is greater than the sample peak value.

76. The method of claim 75 wherein raising the gain reference setpoint to the compensating gain setpoint and raising the zero offset to the compensating gain factor comprises setting the compensating gain setpoint to the gain reference setpoint and the compensating gain factor to the zero offset and iteratively raising the compensating gain setpoint by a gain adjustment value and iteratively raising the compensating gain factor by an offset adjustment value by iteratively comparing the reference peak value to the sample peak value raised by a weighted sample peak value and thereby iteratively raising the compensating gain setpoint with the gain adjustment value and iteratively raising the compensating gain factor with the offset adjustment value for each comparison until the sample peak value iteratively raised by the weighted sample peak value is not lower than the reference peak value.

77. The method of claim 72 further comprising lowering the gain reference setpoint to a compensating gain setpoint and lowering the zero offset to a compensating gain factor if the reference peak value is lower than the sample peak value.

78. The method of claim 77 wherein lowering the gain reference setpoint to the compensating gain setpoint and lowering the zero offset to the compensating gain factor comprises setting the compensating gain setpoint to the gain reference setpoint and the compensating gain factor to the zero offset and iteratively lowering the compensating gain setpoint by a gain adjustment value and iteratively lowering the compensating gain factor by an offset adjustment value by iteratively comparing the reference peak value to the sample peak value lowered by a weighted sample peak value and thereby iteratively lowering the compensating gain setpoint with the gain adjustment value and iteratively lowering the compensating gain factor with the offset adjustment value for each comparison until the sample peak value iteratively raised by the weighted sample peak value is not greater than the reference peak value.