Star Sensor Dynamic Attitude Measurement Using Gyro Correlation
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Solution Overview
Problem
High-precision attitude measurement of star sensors is severely deteriorated under dynamic conditions due to the blurring of star images caused by the motion of the carrier, leading to significant errors in angular velocity measurements and limited precision improvement methods that fail to meet the requirements for high-precision navigation positioning.
Innovation Solution
A dynamic attitude measurement method is proposed, where each star sensor measurement frame is processed with angular velocity compensation, followed by matching vector pairs to establish a correlated measurement equation using a series of frames as a single measurement frame, and an attitude matrix is solved using the least square method to obtain high-precision attitudes and their changes, incorporating a strapped-down rigid coupling of a gyro unit with three orthogonally mounted single-axis gyros and a star sensor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the star sensor measures attitude under dynamic conditions, then real-time navigation capability is improved, but measurement precision deteriorates due to star image blurring from carrier rotation
Solution Approach 1:
The patent applies preliminary anti-action by using gyro data to predict and compensate for the carrier's rotation motion during the star sensor's exposure time. The compensation algorithm pre-calculates the expected star image displacement based on gyro angular velocity measurements, then applies reverse transformation to the captured image, effectively counteracting the blurring effect before attitude measurement is performed.
Solution Approach 2:
The patent introduces the gyro as an intermediary device that measures carrier rotation independently. The gyro data serves as a mediator between the dynamic carrier motion and the star sensor measurement, providing compensation information that allows the star sensor to maintain high precision despite dynamic conditions. The combined gyro-star sensor system resolves the contradiction by using the gyro's high-speed response to protect the star sensor's high-precision attitude measurement capability.
2Measurement precision
If the exposure time of the star sensor is increased, then the signal-to-noise ratio is improved, but the star image blurring is worsened due to carrier rotation during exposure
Solution Approach 1:
The compensation algorithm applies preliminary anti-action by calculating the expected star image displacement during exposure based on gyro data, then applying reverse transformation to counteract the blurring effect. This allows the star sensor to use longer exposure times for improved signal-to-noise ratio without suffering from rotation-induced blurring, as the compensation effectively 'freezes' the star images.
3Speed
If the rotation angular velocity of the carrier is increased, then the dynamic navigation capability is improved, but the star image blurring becomes more severe
Solution Approach 1:
The gyro serves as an intermediary that independently measures carrier rotation at high speeds. By using the gyro's angular velocity data as compensation information, the system can maintain accurate attitude measurement even at high rotation rates. The gyro's fast response capability allows it to track rapid carrier motion, providing real-time compensation that enables the star sensor to maintain image quality regardless of the carrier's rotation speed.
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
This method effectively suppresses dynamic errors and noise, enabling high-precision dynamic attitude measurement of the motion carrier, achieving precision comparable to static conditions by correlating multiple frames and reducing errors by √2 times with each frame correlation, thus meeting the requirements for high-precision navigation under dynamic conditions.
Implementation Method 1
A gyro is an inertial measurement device capable of measuring a rotation angular velocity of a motion carrier relative to an inertial space
Implementation Method 2
a star sensor (hereinafter referred to as: SS) is a device for the navigation-positioning of a motion carrier through fixed stars
Implementation Method 3
extracting centric coordinates of the star points with the centroid extraction algorithm
Data Source
AI summary
The disclosure discloses a dynamic attitude measurement method of a star sensor based on gyro's precise angular correlation. On the basis that a dynamic compensation is performed on each of the measurement exposure frames of the star sensor and a fixed star matching vector matrix having dynamic error and noise influence is obtained in a prior art, a transform matrix between every two adjacent measurement frames of the star sensor is precisely measured by a unit including three gyros fixedly coupled with the star sensor. The transform matrix correlates the matched vector matrixes of the adjacent measurement frames of the star sensor. Finally, a correlated measurement equation is established with a series of correlated measurement frames, which is corresponding to processing a series of measurement frames as a single measurement frame.