Anisotropic Weighted Gradient Method for CMG Singularity Avoidance
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing attitude control methods for spacecraft using Control Moment Gyro (CMG) systems face challenges in avoiding singularity, particularly 'impassable singularity,' which results in insufficient torque output, especially during high-speed attitude changes, and require complex off-line path planning.
Innovation Solution
The 'anisotropic weighted gradient method' (AWGM) generates weighted input-output gains to prioritize torque output in the main direction, allowing real-time calculation of angular and angular velocity profiles for each gimbal, enabling efficient torque output even near singularity by applying these weights to the gradient method.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional gradient method or singularity avoidance methods are used, then singularity can be avoided to some extent, but torque output becomes insufficient especially during high-speed attitude changes
Solution Approach 1:
The patent transforms the fixed isotropic gradient method into an adaptive anisotropic method by dynamically changing the weighting parameters based on the required torque direction. The weighting matrix W is adjusted according to the main torque direction, allowing the system to prioritize torque output in critical directions while maintaining singularity avoidance capabilities.
Solution Approach 2:
The patent introduces dynamic adaptation by continuously updating the weighting parameters based on real-time attitude change requirements. The system transitions from a static gradient method to a dynamic anisotropic weighted gradient method that adapts its characteristics according to the operational demands, particularly during high-speed attitude changes.
2Reliability
If off-line path planning is performed to avoid singularity, then singularity can be avoided, but calculation complexity increases
Solution Approach 1:
The patent enables the CMG system to automatically adjust its own control parameters in real-time based on its current state and operational requirements. The anisotropic weighted gradient method self-adapts the weighting matrix according to the main torque direction, eliminating the need for complex off-line path planning while maintaining singularity avoidance.
Solution Approach 2:
The patent simplifies the control approach by dynamically changing the weighting parameters during operation rather than performing complex off-line calculations. The weighting matrix is adjusted in real-time based on the required torque direction, reducing computational complexity while maintaining effectiveness.
3Reliability
If isotropic gradient method is used to maintain input-output gain, then singularity is avoided, but torque output in specific direction becomes insufficient
Solution Approach 1:
The patent introduces asymmetry into the gradient method by applying different weighting factors to different directions. The weighting matrix W reflects the anisotropic nature of the torque requirements, with higher weights assigned to the main torque direction and lower weights to other directions, creating an asymmetric control strategy that prioritizes critical torque output.
Solution Approach 2:
The patent applies local quality enhancement by focusing the control effort specifically on the main torque direction where it is most needed. The anisotropic weighting allows the system to concentrate its torque output capability in the critical direction while maintaining adequate performance in other directions, rather than treating all directions equally.
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 increases the amplification ratio of input-output gains in the main torque direction, allowing for sufficient torque output during attitude changes and maintaining attitude control, avoiding singularity issues while reducing calculation complexity and energy requirements.
Implementation Method 1
a plurality of CMGs (control moment gyros) as actuators for controlling attitude of the space craft
Data Source
AI summary
Disclosed is an attitude change control system that is designed to efficiently output a torque for attitude change of a space craft using CMGs and realizes a real time CMG driving rule. A CMG gimbal steering law 15 generates target profiles for setting angle and angular velocity for each gimbal by applying an anisotropic weighted gradient method based upon the necessary torque calculated by a feed back controller 13 and a feed forward controller 14 from the angle and angular velocity in the target direction from the attitude navigator 12 and the current angle and angular velocity of the space craft estimated by the attitude estimator 11 as well as the current condition of each gimbal from the CMG 40, thereby controlling the CMG 40 for changing the attitude of the space craft dynamics 50 to the target direction.