Environmentally mitigated navigation system

• US 6,778,908 B2
• Filed: 04/07/2003
• Issued: 08/17/2004
• Est. Priority Date: 06/25/2002
• Status: Active Grant

• Current Assignee: Charles Stark Draper Laboratory Incorporated
• Original Assignee: Charles Stark Draper Laboratory Incorporated
• Inventors: Martorana, Richard T., Ash, Michael E.
• Primary Examiner(s): Barlow, John
• Assistant Examiner(s): Taylor, Victor J.
• Application Number:
  US10/408,704
• Publication Number:
  US 20030236628A1
• Time in Patent Office: 498 Days
• Field of Search: 702/9, 702/6, 731/59, 731/521.3, 175/236, 175/45, 175/57, 333/04
• US Class Current: 702/9
• CPC Class Codes: G01V 1/52 Structural details
• CPC Class Codes: G01V 11/002 Details, e.g. power supply systems for logging instruments, transmitting or recording data, specially adapted for well logging, also if the prospecting method is irrelevant means for transmitting well survey signals E21B47/12; signal transmission systems in general G08C; transmission in general H04B

Abstract

An environmentally mitigated navigation system includes a thermal isolating chamber, an inertial measurement unit that can include individual gyroscopes and accelerometers for making inertial measurements, and a temperature control system; the temperature control system includes a thermoelectric cooling system, which in a powered mode maintains the inertial measurement unit at a substantially predetermined temperature, and a phase change device for maintaining the inertial measurement unit or inertial sensors at substantially a predetermined temperature in an unpowered mode; the phase change device substantially maintains the predetermined temperature by changing phase to define a stable temperature window for the inertial measurement unit or individual sensors to make inertial measurements during the unpowered mode as well as during the powered mode.

Claims

1. An environmentally mitigated navigation system comprising:

a thermal isolating chamber;

an inertial measurement unit, for making inertial measurements, disposed on said isolating chamber; and

a temperature control system including a thermoelectric cooling system which in a powered mode maintains said inertial measurement unit at substantially a predetermined temperature and a phase change device for maintaining the inertial measurement unit at substantially said predetermined temperature in an unpowered mode while the phase change device changes phase to define a stable temperature window for said inertial measurement unit to make inertial measurements during the unpowered mode.

2. The environmentally mitigated navigation system of claim 1 in which said thermal isolating chamber is pressure resistant.

3. The environmentally mitigated navigation system of claim 1 in which said inertial measurement unit includes a micro electromechanical system (MEMS).

4. The environmentally mitigated navigation system of claim 1 in which said inertial measurement unit includes at least one gyroscope for determining the azimuth of said inertial measurement unit and at least one accelerometer for determining the vertical orientation of said inertial measurement unit.

5. The environmentally mitigated navigation system of claim 1 in which said inertial measurement unit includes three gyroscope input axes for determining the azimuth of said inertial measurement unit after slant drilling and three accelerometer input axes for determining the vertical orientation of said inertial measurement unit after slant drilling.

6. The environmentally mitigated navigation system of claim 1 in which said thermoelectric cooling system includes semiconductor junctions.

7. The environmentally mitigated navigation system of claim 1 in which said phase change device includes a medium which is at least partially solid at the instruments'"'"' operating temperature.

8. The environmentally mitigated navigation system of claim 1 in which said phase change device includes paraffin.

9. The environmentally mitigated navigation system of claim 1 further including a drilling mud driver electric generator for powering said thermoelectric cooling system in said powered mode.

10. The environmentally mitigated navigation system of claim 1 further including a shock and vibration isolation system for reducing vibration of said inertial measurement unit.

11. The environmentally mitigated navigation system of claim 1 in which said inertial measurement unit includes one or more gimbals configured such that one or more measurement biases of the inertial measurement unit sensors can be determined.

12. An environmentally mitigated borehole navigation system comprising:

a drilling mud driver electric generator;

a thermally isolated and pressure proof chamber;

an inertial measurement unit, for making inertial measurements, disposed in said chamber;

a temperature control system including a thermoelectric cooling system powered by said drilling mud driver for maintaining said inertial measurement unit at a predetermined temperature; and

a shock and vibration isolation system for reducing vibration of said inertial measurements at least during drilling periods.

13. The environmentally mitigated bore hole navigation system of claim 12 in which said inertial measurement unit includes micro eletromechanical system (MEMS) gyros and accelerometers.

14. The environmentally mitigated bore hole navigation system of claim 12 in which said inertial measurement unit includes at least one gyroscope for determining the azimuth of said inertial measurement unit and at least one accelerometer for determining the vertical orientation of said inertial measurement unit.

15. The environmentally mitigated bore hole navigation system of claim 12 in which said inertial measurement unit includes three gyroscope input axes for determining the azimuth of said inertial measurement unit and three accelerometer input axes for determining the vertical orientation of said inertial measurement unit.

16. The environmentally mitigated bore hole navigation system of claim 12 in which said thermoelectric cooling system includes a semiconductor device.

17. The environmentally mitigated bore hole navigation system of claim 12 in which said temperature control system further includes a phase change device for maintaining the inertial measurement unit at substantially the predetermined temperature when the thermoelectric cooling system is unpowered and a medium of the phase change device is changing phase.

18. The environmentally mitigated bore hole navigation system of claim 17 in which said phase change device includes a medium which is solid or partially solid at the operating temperature of the inertial measurement unit.

19. The environmentally mitigated bore hole navigation system of claim 12 in which said phase change device includes paraffin.

20. The environmentally mitigated bore hole navigation system of claim 12 in which said inertial measurement unit includes one or more gimbals configured such that one or more measurement biases of the inertial measurement unit can be determined.

21. An environmentally mitigated navigation system comprising:

a drilling mud driver electric generator;

a thermally isolated and pressure proof chamber;

an inertial measurement unit, for making inertial measurements, disposed on said isolating chamber; and

a temperature control system including a thermoelectric cooling system powered by said drilling mud driver for maintaining said inertial measurement unit at substantially a predetermined temperature in a powered mode and a phase change device for maintaining the inertial measurement unit at substantially the predetermined temperature in an unpowered mode while the phase change device changes phase to define a stable temperature window for said inertial temperature unit to make inertial measurements during the unpowered mode; and

a shock and vibration isolation system for reducing vibration of said inertial measurement unit at least during drilling periods.