Multi-Position Fine Alignment for Gyroscope Bias Suppression
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Solution Overview
Problem
Existing attitude measurement methods for directional drilling in harsh environments, such as high temperature and strong vibration, face challenges with gyroscope reliability and bias repeatability errors, leading to inaccurate well trajectory control.
Innovation Solution
A method using a strapdown inertial navigation system with fine alignment at multiple positions, employing the Kalman algorithm for attitude and velocity updates, and zero-velocity and earth rotation angular rate corrections to suppress gyroscope drift errors and improve alignment accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If existing calibration methods are used, then the calibration process is simple, but the calibration accuracy is limited by gyroscope bias repeatability error in harsh environments
Solution Approach 1:
The calibration process is divided into multiple calibration positions (at least two different positions) to segment the measurement process. By performing calibration at different positions, the method captures variations in gyroscope bias repeatability error caused by environmental factors such as temperature and vibration, enabling more accurate error characterization and compensation.
Solution Approach 2:
The calibration method introduces a positional dimension by performing measurements at multiple different positions rather than a single position. This dimensional expansion allows the system to observe and compensate for environmental effects on gyroscope bias that would be invisible in a single-position calibration, thereby improving calibration accuracy without requiring higher precision instruments.
2Measurement precision
If single position fine alignment is used, then the alignment process is fast, but the observability of inertial instrument errors is insufficient
Solution Approach 1:
The alignment process is segmented into multiple fine alignment operations at different positions. Each fine alignment operation processes data from a specific position, and the results are integrated to achieve comprehensive error observability. This segmentation allows the system to maintain relatively quick alignment times while significantly improving the observability of inertial instrument errors through multi-position data collection.
3Measurement precision
If high precision inertial instruments are used, then the measurement precision is improved, but the device complexity and cost increase
Solution Approach 1:
Instead of using a single high-precision inertial instrument, the method creates multiple measurements by positioning the same instrument at different positions. This copying approach through spatial replication allows standard precision instruments to achieve the measurement accuracy that would otherwise require more expensive, higher-precision instruments, thereby reducing device complexity and cost.
Data Source
AI summary
An attitude measurement method, which relates to the technical field of measurement while drilling in directional drilling, which can improve the observability of inertial instrument errors, suppress the repeatability errors of gyroscopes and improve the attitude measurement accuracy. The method adopts the method of fine alignment at multiple positions to carry out initial alignment; the method includes the steps of: S1, taking current attitude data and velocity data of the strapdown inertial navigation system as first initial values, and performing fine alignment at a first position; S2, changing the position of a strapdown inertial navigation system to an nth position, and performing attitude update and velocity update according to the last fine alignment result in the position changing process; and S3, taking the results of attitude update and velocity update as the nth initial values, performing the nth fine alignment at the nth position to complete the initial alignment of the strapdown inertial navigation system, thereby realizing attitude measurement. The solution of the present invention is suitable for measuring the horizontal attitude and azimuth of the whole inclined section of a horizontal well, especially the application of directional drilling gyro measurement while drilling in the attitude measurement of large inclined wells and horizontal wells.