Flexible Spacecraft Attitude Control via Friction and Vibration Estimation
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Solution Overview
Problem
Flexible spacecraft appendages cause vibration interference that affects attitude control, and flywheel friction issues, particularly at low speeds, complicate precise attitude control due to friction moment generation and chattering.
Innovation Solution
A method for attitude control using finite time friction estimation, which involves constructing a flywheel friction disturbance estimator and a flexible appendage vibration disturbance observer to estimate and compensate for friction and vibration disturbances, combining these with a nominal controller to form a compound controller that compensates for flywheel friction and appendage vibrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If flexible appendages are used to reduce weight and meet launch requirements, then the spacecraft can be launched to predetermined orbit with lower cost, but vibration during motion of the spacecraft body affects the accuracy of spacecraft attitude control
Solution Approach 1:
The patent implements a vibration disturbance observer that continuously monitors and estimates the vibration disturbances caused by flexible appendages. The estimated vibration signals are fed back to the compound controller, which compensates for these disturbances in real-time, thereby maintaining attitude control accuracy despite the presence of flexible structures
Solution Approach 2:
The patent introduces a vibration disturbance observer as an intermediary component between the flexible appendages and the attitude control system. This observer acts as a mediator that estimates the vibration disturbances and provides compensation signals to the controller, effectively isolating the impact of flexible appendage vibrations on attitude control
2Duration of action of stationary object
If flywheels are used as main execution component for stable output and long service life, then the spacecraft achieves long-life and high-precision attitude control, but friction moment is generated when the speed of the flywheel is low and crosses zero, affecting the spacecraft attitude control system
Solution Approach 1:
The patent implements a friction disturbance observer that continuously monitors the flywheel's rotational speed and estimates the friction moment, particularly when the speed is low or crossing zero. The estimated friction signals are fed back to the compound controller for real-time compensation, maintaining attitude control precision throughout the flywheel's operational life
Solution Approach 2:
The patent replaces direct mechanical friction compensation with an observer-based estimation approach. Instead of using complex mechanical mechanisms to compensate for friction, the system uses the friction disturbance observer to estimate friction moments and applies software-based compensation through the compound controller
3Device complexity
If traditional attitude control methods are used without friction estimation, then the control system is simpler, but the impact of flywheel friction and flexible appendage vibrations cannot be overcome, making it more difficult to stabilize the spacecraft system
Solution Approach 1:
The patent segments the attitude control problem into distinct components: a nominal controller for basic attitude control, a friction disturbance observer for flywheel friction compensation, and a vibration disturbance observer for flexible appendage vibration compensation. This segmentation allows each component to be designed and tuned independently while working together to achieve reliable spacecraft stabilization
Data Source
AI summary
The present invention provides a method for attitude control based on finite time friction estimation for a flexible spacecraft. The control method includes the following steps: a. introducing spacecraft flywheel friction disturbance into a spacecraft dynamics system, and establishing a flexible spacecraft dynamics system with flywheel friction disturbance; b. converting the flexible spacecraft dynamics system with flywheel friction disturbance into a state-space form; c. constructing a flywheel friction disturbance estimator; d. constructing a flexible appendage vibration disturbance observer; and e. combining the flywheel friction disturbance estimator in the step c and the flexible appendage vibration disturbance observer in the step d with a nominal controller to obtain a compound controller; the compound controller compensating for flywheel friction according to an estimated value of a flywheel friction moment; and the compound controller compensating for flexible appendage vibration disturbance according to an estimated value of flexible appendage vibration disturbance.