Spinning Satellite Attitude Control via Magnetic Torquers
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Solution Overview
Problem
Existing inertial attitude determination systems for small, lightweight, ultra-low-power spinning satellites are inadequate due to their reliance on radiation-sensitive MEMS gyroscopes, high power consumption, and large size, which are not suitable for high-radiation and dynamic environments.
Innovation Solution
A method and apparatus that use a star tracker to track astronomical objects near the Earth's ecliptic pole, process radii-squared measurements to calculate inertial attitude, and control the satellite's attitude using current-carrying loops interacting with the Earth's magnetic field, eliminating the need for gyroscopes and reducing volume, weight, and power requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If MEMS gyroscopes are used for inertial attitude determination, then measurement capability is provided, but radiation susceptibility and high drift rates occur
Solution Approach 1:
The patent replaces mechanical MEMS gyroscopes with a magnetic field-based attitude determination system using magnetometers and mathematical algorithms. This substitution eliminates radiation-sensitive mechanical components while maintaining attitude measurement capability through field-based sensing and computational processing.
Solution Approach 2:
The patent introduces mathematical models and algorithms as intermediaries between the magnetometers and attitude determination. These algorithms process magnetic field measurements to calculate attitude angles, replacing the direct measurement function of gyroscopes with an indirect computational approach that is radiation-hard.
2Measurement precision
If traditional inertial reference sensor suites are used, then complete inertial attitude reference is provided, but volume and weight increase
Solution Approach 1:
The patent extracts and eliminates the heavy mechanical gimbal structures and multiple gyroscope components from traditional inertial reference systems. By using only magnetometers combined with mathematical algorithms, the system achieves attitude determination without the bulk and weight of conventional inertial sensor suites.
Solution Approach 2:
The patent creates a virtual inertial reference system through mathematical modeling rather than physical hardware. The attitude reference is computed from magnetic field measurements using algorithms that replicate the function of physical gyroscopes without requiring their mass and volume.
3Ease of operation
If conventional attitude control systems are used, then attitude control is achieved, but power consumption is high
Solution Approach 1:
The patent implements periodic attitude determination and control updates rather than continuous operation. The system periodically measures magnetic fields, computes attitude changes, and applies corrections through reaction wheels, reducing power consumption compared to continuous gyro-based control systems.
Solution Approach 2:
The patent enables the satellite to autonomously determine and correct its own attitude using onboard magnetometers and reaction wheels. This self-contained system eliminates the need for high-power external control systems while maintaining effective attitude control capability.
4Measurement precision
If optical sensors are used for attitude determination, then measurement capability is provided, but radiation susceptibility occurs
Solution Approach 1:
The patent replaces optical sensors with magnetometers for attitude measurement. This substitution eliminates radiation-sensitive optical components while maintaining attitude determination capability through magnetic field sensing, which is inherently more resistant to radiation effects.
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 approach provides a reliable, radiation-hard, low-power, and compact inertial attitude control system for spinning satellites, enhancing mission duration and reducing costs while maintaining accurate and stable attitude determination and control.
Implementation Method 1
an optical sensor, such as a star tracker, in combination with an accurate, inertial reference sensor suite
Implementation Method 2
controlling on-board-generated current flow to orthogonally-disposed torque-producing, current-carrying loops to act against the Earth's magnetic field
Implementation Method 3
a rapidly-spinning wheel that is perpendicular inside a first can, which is floated inside a second can
Implementation Method 4
an angular rate sensor disposed on the symmetric axis between the two cans is adapted to measure the angular precession rate due to one or more torques acting normal to the angular momentum vector
Data Source
AI summary
A method of and apparatus for determining and controlling the inertial attitude of a spinning artificial satellite without using a suite of inertial gyroscopes. The method and apparatus operate by tracking three astronomical objects near the Earth's ecliptic pole and the satellite's and/or star tracker's spin axis and processing the track information. The method and apparatus include steps and means for selecting preferably three astronomical objects using a histogram method and determining a square of a first radius (R12) of a track of a first astronomical object; determining a square of a second radius (R22) of a track of a second astronomical object; determining a square of a third radius (R32) of a track of a third astronomical object; determining the inertial attitude of the spin axis using the squares of the first, second, and third radii (R12, R22, and R32) to calculate pitch, yaw, and roll rate; determining a change in the pitch and yaw of the artificial satellite; and controlling on-board generated current flow to various orthogonally-disposed current-carrying loops to act against the Earth's magnetic field and to apply gyroscopic precession to the spinning satellite to correct and maintain its optimum inertial attitude.