Mixed-State Dynamics Control for Spacecraft Fuel Sloshing
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The challenge in controlling systems with mixed-state matter, such as spacecraft or robots, is the difficulty in modeling and mitigating the impact of liquid sloshing, which affects the stability and performance due to the mutual coupling between solid-state and liquid-state dynamics, making it hard to design effective controllers.
Innovation Solution
A heterogeneous model is developed that couples the dynamics of solid-state and liquid-state matter by estimating the shape and center of mass of the fluid within the container, using Computational Fluid Dynamics (CFD) to determine the fluid shape and incorporating this information into the control system to adjust the state of the system accordingly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If thrust vector correction methods are used to correct nutation in spacecraft, then control accuracy is improved, but control effectiveness deteriorates when high magnitudes of fuel sloshing forces overpower the corrections
Solution Approach 1:
The control system performs preliminary action by predicting future sloshing forces and their effects on spacecraft attitude before they fully manifest. The heterogeneous model anticipates the coupled dynamics between fuel sloshing and spacecraft motion, allowing the controller to prepare compensatory actions in advance, thus maintaining control effectiveness even when sloshing forces become large.
Solution Approach 2:
The system implements feedback by continuously monitoring spacecraft attitude and fuel sloshing state, then using this information to adjust control commands. The heterogeneous model provides real-time predictions of sloshing effects, enabling the controller to adapt thrust vector corrections dynamically, ensuring control accuracy is maintained despite varying sloshing conditions.
2Device complexity
If a traditional control model ignoring liquid sloshing is used, then device complexity is reduced, but stability deteriorates due to unaccounted sloshing effects
Solution Approach 1:
The patent introduces an intermediary heterogeneous model that acts as a mediator between the simple control architecture and the complex sloshing physics. This model captures the essential coupled dynamics between fuel sloshing and spacecraft attitude without requiring full computational fluid dynamics, thus maintaining relative simplicity while significantly improving stability predictions and control performance.
Solution Approach 2:
The system changes parameters by incorporating sloshing-related state variables (such as fuel wave amplitude and frequency) into the control model. These parameter changes allow the controller to account for sloshing effects dynamically, improving stability without requiring a complete redesign of the control architecture, thus balancing complexity and performance.
3Stability of the object's composition
If a heterogeneous model considering mutual coupling between solid-state and liquid-state dynamics is used, then stability is improved, but device complexity increases due to difficulty in modeling
Solution Approach 1:
The heterogeneous model is segmented into distinct but coupled components: a solid-state dynamics model for the spacecraft structure and a liquid-state dynamics model for the fuel sloshing. Each component is modeled separately using appropriate physics, then coupled through interaction terms. This segmentation allows the complex coupled system to be managed through modular modeling approaches, reducing overall complexity while maintaining accuracy.
Solution Approach 2:
The model applies local quality by using different levels of modeling fidelity in different parts of the system. The spacecraft rigid body dynamics are modeled with high precision using standard equations of motion, while the fuel sloshing is modeled using simplified potential flow theory or empirical sloshing models. This localized approach to modeling quality optimizes the balance between accuracy and complexity for each subsystem.
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 allows for precise control of systems by considering the sloshing dynamics, improving stability and performance by accurately accounting for the mutual coupling between solid-state and liquid-state matter, enabling effective control commands to be issued based on real-time feedback.
Implementation Method 1
using Computational Fluid Dynamics (CFD) to determine the fluid shape
Implementation Method 2
change in the shape of the volume of the fluid changes a location of a center of mass of the volume of fluid
Implementation Method 3
dynamics of the mixed-state matters are mutually coupled, i.e., the dynamics of the solid-state matter (e.g., container) and liquid-state matter (fluid) affect each other
Data Source
AI summary
The present disclosure discloses a system and a method for controlling a system with mixed-state matter including a solid-state matter with parts forming a container including a volume of fluid. The method includes collecting a feedback signal indicative of a state of the system and determining a control command to an actuator of the system at a current control step by solving an optimal control problem changing the state of the system according to a control objective subject to a heterogenous model of dynamics of the system, including a model of dynamics of the solid-state matter mutually coupled with a model of dynamics of the volume of fluid in the container. The method further includes submitting the control command to the actuator of the system to change the state of the system.