The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Sep. 17, 2002
Filed:
Jun. 08, 1999
Ichiro Shirasaka, Sugar Land, TX (US);
Kirby G. Schrader, Houston, TX (US);
Jean-Michel Hache, Houston, TX (US);
Schlumberger Technology Corporation, Sugar Land, TX (US);
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.