Dual-Gyro Borehole Navigation with Adaptive Orientation
Solution Overview
Problem
Existing navigation systems for boreholes, particularly those using strapdown inertial navigation, face limitations in accurately measuring azimuth and maintaining a stable Gyro Toolface at high angular rotations and varying inclinations due to gyroscopic bias and saturation issues.
Innovation Solution
A navigation device with a first and second gyro, each with sensitive axes, and a gimbal system that allows operation in two modes: one mode renders measurements insensitive to gravity, enabling bias-free attitude computation at all inclinations, and a second mode forms an inertial navigation system for continuous surveying and Gyro Toolface determination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of stationary object
If strapdown inertial navigation is used to map a borehole, then the system can provide continuous survey data, but the system becomes sensitive to unmodelled g-dependent gyro bias at increased inclination angles
Solution Approach 1:
The patent implements a dynamically adjustable gyro configuration where the second gyro can be oriented in different modes. In the first mode, the gyro is positioned to be insensitive to g-dependent bias for azimuth measurement. In the second mode, the gyro is repositioned to form an inertial navigation system for continuous surveying. This dynamic reconfiguration allows the system to adapt to different operational requirements and eliminate g-dependent bias errors.
Solution Approach 2:
The system changes the physical orientation parameter of the second gyro between two distinct positions. By altering the gyro's spatial configuration from a g-insensitive orientation to an inertial navigation orientation, the system can selectively activate different measurement capabilities and eliminate parameter-dependent biases through adaptive Kalman filtering.
2Productivity
If the drill string rotates at high speeds, then drilling productivity increases, but the gyroscope saturates and loses navigation accuracy
Solution Approach 1:
The patent divides the gyroscopic measurement function into two separate gyro systems with distinct roles. The first gyro is dedicated to measuring earth rate for azimuth determination and is protected from saturation by its specific orientation. The second gyro handles the inertial navigation functions. This segmentation allows high-speed drilling to continue without saturating the azimuth-sensing gyro.
Solution Approach 2:
The patent introduces a mechanical or electromagnetic intermediary mechanism (driving unit) that controls the orientation of the second gyro. This intermediary allows the system to decouple the roll axis measurements from the azimuth-sensing gyro, preventing saturation while maintaining navigation accuracy during high-speed rotation.
3Measurement precision
If the second gyro is oriented to eliminate g-dependent bias, then azimuth measurement accuracy improves, but the system cannot perform continuous inertial navigation surveying
Solution Approach 1:
The system employs a dynamically reconfigurable gyro arrangement where the second gyro can switch between two operational modes. In the first mode, it is oriented to eliminate g-dependent bias for accurate azimuth measurement. In the second mode, it repositions to form a complete inertial navigation system for continuous surveying. This dynamic adaptability allows the system to perform both functions as needed.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The system provides accurate azimuth and inclination measurements and stable Gyro Toolface across all drilling conditions, including high roll rates, by decoupling the roll axis and using adaptive Kalman filtering to eliminate gyro bias, ensuring continuous INS survey and improved accuracy.
Implementation Method 1
a first gyro (2) including a first sensitive axis (5) and a second sensitive axis (6); a second gyro (4) including at least a third sensitive axis (7)
Implementation Method 2
a driving unit (9) configured to orient the second gyro (4) in a first mode in a first position in which an earth acceleration (g) dependent error on the second gyro (4) is insignificant
Implementation Method 3
by decoupling the roll axis and using adaptive Kalman filtering to eliminate gyro bias
Data Source
AI summary
A navigation device for surveying and directing a borehole comprises: a first gyro including a first sensitive axis and a second sensitive axis; a second gyro including at least a third sensitive axis; and a driving unit configured to orient the second gyro in a first mode in a first position in which an earth acceleration dependent error on the second gyro is insignificant and to orient the second gyro in a second mode in a second position in which the third sensitive axis is perpendicular to the first sensitive axis and perpendicular to the second sensitive axis.