Distributed Attitude Control for Joined Spacecraft Entities
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Solution Overview
Problem
Current attitude control systems (ACS) in space architectures lack the ability to distribute control functions among multiple joined entities, leading to unstable modes and constraints on actuator capacities and inertia properties.
Innovation Solution
A distributed ACS is designed by implementing a controller in each joined entity, determining intermediate design parameters for proportional and derivative gains, and selecting stiffness and damping coefficients for interfaces, allowing for iterative optimization of control performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single centralized ACS is used for reconfigurable joined entities, then the system structure is simple, but the actuator capacities and inertia properties are constrained
Solution Approach 1:
The centralized ACS is segmented into distributed ACS units, with each joined entity having its own ACS controller. This segmentation allows each unit to independently control its attitude while participating in the formation, thereby increasing actuator capacity flexibility and inertia property adaptability without requiring a complex centralized system.
Solution Approach 2:
The system transitions from a single-dimension centralized control architecture to a multi-dimension distributed control architecture. Each entity operates in its own control dimension while maintaining coordination through inter-entity communication, enabling greater adaptability in actuator capacities and inertia properties while keeping individual ACS units relatively simple.
2Object-affected harmful factors
If passive dampers are used for payload mounting, then mechanical isolation is achieved, but unstable modes are introduced
Solution Approach 1:
An active control system is introduced as an intermediary between the payload and the passive dampers. This active ACS compensates for the unstable modes introduced by passive dampers through real-time control actions, while maintaining the mechanical isolation benefits of the passive damping system.
Solution Approach 2:
The system dynamically adjusts control parameters to counteract the unstable modes generated by passive dampers. By changing control gains and damping coefficients in real-time, the system maintains stability while preserving the mechanical isolation provided by the passive damper mounting.
3Stability of the object's composition
If modular subsystems are permanently attached, then structural stability is maintained, but reconfigurability is limited
Solution Approach 1:
The attachment configuration of modular subsystems is made dynamic rather than static. Joined entities can be permanently or temporarily attached based on mission requirements, allowing the system to reconfigure its structure while maintaining stability through the distributed ACS control that adapts to changing configurations.
4Weight of moving object
If distributed ACS is implemented among multiple joined entities, then actuator miniaturization is enabled, but control system complexity increases
Solution Approach 1:
Each joined entity's ACS controller independently manages its own attitude control and contributes to formation control. This self-service approach allows actuators to be miniaturized since each unit only needs to provide control authority for its own entity, while the distributed coordination emerges from individual self-controlled units working together.
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 enables stable and efficient attitude control by distributing torque requirements, allowing for miniaturization and scaling of attitude actuators, and relaxing the power and torque constraints on individual entities, facilitating larger and more complex space structures.
Implementation Method 1
The compliant interface includes a spring-damper system between the first and second joined entities
Implementation Method 2
damping coefficients, Ks and Cd respectively of all the interfaces
Data Source
AI summary
A process to design an attitude control system (ACS) controller in each of a plurality of joined entities includes identifying a worst case configuration as a design-to configuration as one or more configurations in a given set S of configurations required for a spacecraft. For the design-to configuration, the process includes deriving one or more system equations in a functional form of equations to determine intermediate design parameters that represent effective proportional and derivative gains of the combined controller, Kp and Kd, respectively. The process also includes determining the design parameters of the ACS controller, namely, gains Kq and Kω and stiffness and damping coefficients, Ks and Cd respectively of all the interfaces between each of the plurality of joined entities, from the intermediate design parameters Kp and Kd. The process further includes programming the ACS controller with selected values of the design parameters for matrices Kq and Kω and selecting springs with stiffness Ks and dampers with damping coefficient Cd for all interfaces between each of the plurality of joined entities. The process includes iterating the computer-implemented process after incrementing a convergence requirement parameter σthreshold when the control performance is not acceptable and until the system achieves acceptable performance, and programming the ACS controller for each of the plurality of joined entities.