Method and apparatus for borehole surveying
First Claim
1. A strapdown inertial navigation method comprising:
- maneuvering a probe including at least three vibrating mass, Coriolis effect gyroscopes in a borehole;
initializing the probe'"'"'s attitude in the borehole within the probe'"'"'s frame of reference;
determining, from the gyroscopes, three orthogonal, incremental rotation angles for the probe within the probe'"'"'s frame of reference;
determining three orthogonal, incremental velocities for the probe within the probe'"'"'s frame of reference;
translating the three incremental velocities from the probe'"'"'s frame of reference into the inertial frame of reference using the three incremental rotation angles;
determining from the translated incremental velocities a velocity vector in a local-vertical, wander-azimuth frame of reference;
obtaining a velocity error observation;
estimating a system error from the velocity vector and a velocity error observation; and
feeding the system error back into the inertial navigation method.
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Abstract
The invention is, in its various aspects, a method and apparatus useful for strapdown inertial navigation and surveying in a borehole. The method comprises maneuvering a probe including three vibrating mass, Coriolis effect gyroscopes in a borehole and initializing the probe'"'"'s attitude in the borehole within the probe'"'"'s frame of reference. Three orthogonal, incremental rotation angles and three orthogonal, incremental velocities are determined for the probe within the probe'"'"'s frame of reference. The incremental rotation angles are determined from the gyroscopes. The method then translates the three incremental velocities from the probe'"'"'s frame of reference into the inertial frame of reference using the three incremental rotation angles. Next, a velocity vector in a local-vertical, wander-azimuth frame of reference is determined from the translated incremental velocities. A velocity error observation is then obtained. A system error is then estimated from the velocity vector and the velocity error observation. The system error is then fed back into the inertial navigation system for use in refining the method. In as second aspect, the invention is a strapdown, inertial measurement unit. The inertial measurement unit includes a housing, three accelerometers, and three vibrating mass, Coriolis effect gyroscopes. The three accelerometers are mounted within the housing. The three vibrating mass, Coriolis effect are rigidly mounted within the housing.
155 Citations
71 Claims
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1. A strapdown inertial navigation method comprising:
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maneuvering a probe including at least three vibrating mass, Coriolis effect gyroscopes in a borehole;
initializing the probe'"'"'s attitude in the borehole within the probe'"'"'s frame of reference;
determining, from the gyroscopes, three orthogonal, incremental rotation angles for the probe within the probe'"'"'s frame of reference;
determining three orthogonal, incremental velocities for the probe within the probe'"'"'s frame of reference;
translating the three incremental velocities from the probe'"'"'s frame of reference into the inertial frame of reference using the three incremental rotation angles;
determining from the translated incremental velocities a velocity vector in a local-vertical, wander-azimuth frame of reference;
obtaining a velocity error observation;
estimating a system error from the velocity vector and a velocity error observation; and
feeding the system error back into the inertial navigation method. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29)
obtaining a cable velocity; and
translating the cable velocity into the local-vertical frame of reference.
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23. The method of claim 1, wherein estimating a system error from the velocity vector and the velocity error observation includes
summing the velocity vector and the velocity error observation; - and
filtering the sum.
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24. The method of claim 23, wherein filtering the sum comprises filtering the sum through a Kalman filter.
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25. The method of claim 1, further comprising buffering the incremental rotation angles and the incremental velocities before translating the three incremental velocities from the probe'"'"'s frame of reference into the inertial frame of reference.
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26. The method of claim 1, wherein feeding the system error back into the inertial navigation method includes feeding the system error back into at least one of the initialization of the probe'"'"'s attitude, the translation of the three incremental velocities from the probe'"'"'s frame of reference into the inertial frame of reference, and the determination of the updated velocity vector.
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27. The method of claim 1, wherein at least one of determining the rotation angles and determining the velocities includes at least one of accelerometer error compensation and gyroscopic error compensation.
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28. The method of claim 27, wherein at least one of accelerometer error compensation and gyroscopic error compensation includes compensating for major deterministic errors.
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29. The method of claim 28, wherein the major deterministic errors include a major deterministic error selected from the group comprising bias, scale factor error, and misalignment.
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30. A strapdown, inertial measurement unit, comprising:
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a housing;
three accelerometers mounted within the housing; and
three vibrating mass, Coriolis effect gyroscopes rigidly mounted within the housing. - View Dependent Claims (31, 32, 33, 34, 35, 36, 37, 38)
an axisymmetric resonator;
a forcer joined to the resonator;
a pickoff bonded to the forcer a vacuum housing into which the resonator, forcer, and pickoff are placed.
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37. The strapdown inertial measurement unit of claim 34, wherein the longitudinal axis of the gyroscopes is skewed relative to the longitudinal axis of the inertial measurement unit.
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38. The strapdown inertial measurement unit of claim 30, further comprising three magnetometers mounted within the housing.
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39. An inertial navigation probe, comprising:
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a strapdown inertial measurement unit, including;
three accelerometers oriented orthogonally respective to each other and mounted within the housing; and
three vibrating mass, Coriolis effect gyroscopes oriented orthogonally respective to each other and rigidly mounted within the housing; and
acquisition electronics for the accelerometers and the gyroscopes; and
an external bus;
an electronics subassembly capable of communicating with the inertial measurement unit over the external bus, the electronics subassembly including;
a plurality of magnetometers;
a controller; and
an internal bus over which the magnetometers and the controller communicate;
a power supply for powering at least one of the accelerometers, gyroscopes, magnetometers, acquisition electronics, controllers. - View Dependent Claims (40, 41, 42, 43, 44, 45)
an axisymmetric resonator;
a forcer joined to the resonator;
a pickoff bonded to the forcer a vacuum housing into which the resonator, forcer, and pickoff are placed.
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43. The inertial navigation probe of claim 41, wherein the longitudinal axis of the gyroscopes is skewed relative to the longitudinal axis of the inertial measurement unit.
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44. The inertial navigation probe of claim 39, wherein the strapdown inertial measurement unit further includes three magnetometers.
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45. The inertial navigation probe of claim 39, further comprising a program storage device encoded with instructions that, when executed by the controller, perform a method comprising:
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initializing the probe'"'"'s attitude in the borehole within the probe'"'"'s frame of reference;
determining three orthogonal, incremental rotation angles for the probe within the probe'"'"'s frame of reference;
determining three orthogonal, incremental velocities for the probe within the probe'"'"'s frame of reference;
translating the three incremental velocities from the probe'"'"'s frame of reference into the inertial frame of reference using the three incremental rotation angles;
determining from the translated incremental velocities a velocity vector in a local-vertical, wander-azimuth frame of reference;
obtaining a velocity error observation;
estimating a system error from the velocity vector and a velocity error observation; and
feeding the system error back into the inertial navigation method.
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46. A strapdown inertial navigation method for use in measurement-while-drilling operations, the method comprising:
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maneuvering a probe in a borehole during drilling operations;
initializing the probe'"'"'s attitude in the borehole within the probe'"'"'s frame of reference;
determining three orthogonal, incremental rotation angles for the probe within the probe'"'"'s frame of reference;
determining three orthogonal, incremental velocities for the probe within the probe'"'"'s frame of reference;
translating the three incremental velocities from the probe'"'"'s frame of reference into the inertial frame of reference using the three incremental rotation angles;
determining from the translated incremental velocities a velocity vector in a local-vertical, wander-azimuth frame of reference;
obtaining a velocity error observation;
estimating a system error from the velocity vector and a velocity error observation; and
feeding the system error back into at least one of initializing the probe'"'"'s attitude, translating the three incremental velocities, and determining the velocity vector. - View Dependent Claims (47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71)
obtaining a cable velocity; and
translating the cable velocity into the local-vertical frame of reference.
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65. The method of claim 46, wherein estimating a system error from the velocity vector and the velocity error observation includes
summing the velocity vector and the velocity error observation; - and
filtering the sum.
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66. The method of claim 65, wherein filtering the sum comprises filtering the sum through a Kalman filter.
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67. The method of claim 46, further comprising buffering the incremental rotation angles and the incremental velocities before translating the three incremental velocities from the probe'"'"'s frame of reference into the inertial frame of reference.
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68. The method of claim 46, wherein feeding the system error back into the inertial navigation method includes feeding the system error back into at least one of the initialization of the probe'"'"'s attitude, the translation of the three incremental velocities from the probe'"'"'s frame of reference into the inertial frame of reference, and the determination of the updated velocity vector.
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69. The method of claim 46, wherein at least one of determining the rotation angles and determining the velocities includes at least one of accelerometer error compensation and gyroscopic error compensation.
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70. The method of claim 69, wherein at least one of accelerometer error compensation and gyroscopic error compensation includes compensating for major deterministic errors.
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71. The method of claim 70, wherein the major deterministic errors include a major deterministic error selected from the group comprising bias, scale factor error, and misalignment.
Specification