Spacecraft Bi-Level Control for Autonomous Station Keeping
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Solution Overview
Problem
Current spacecraft control systems face challenges in concurrently managing station keeping, attitude control, and momentum management due to manual ground-controlled thruster operations, which are inefficient, prone to errors, and unsuitable for scaling with increasing spacecraft numbers, leading to limited precision and increased complexity and cost.
Innovation Solution
A bi-level control scheme using model predictive control (MPC) that coordinates thruster and momentum exchange device operations autonomously, optimizing fuel efficiency by decoupling inner-loop orientation control from outer-loop pose and momentum management, allowing for simultaneous station keeping and momentum unloading with a single set of thrusters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If manual ground control is used for thruster operations, then operational simplicity is maintained, but precision and scalability are limited
Solution Approach 1:
The spacecraft control system performs autonomous station keeping and momentum management without requiring manual ground control interventions. The onboard controller independently determines thruster firing sequences, calculates required impulses, and executes maneuvers based on sensor feedback and orbital mechanics models, enabling the system to serve itself
Solution Approach 2:
The system continuously monitors spacecraft position, velocity, and momentum storage state through onboard sensors, compares these measurements with desired target values, and automatically adjusts thruster operations to correct deviations. This closed-loop feedback mechanism enables high-precision positioning and adaptive momentum management
2Reliability
If separate thruster sets are used for station keeping and momentum unloading, then functional independence is achieved, but mass and system complexity increase
Solution Approach 1:
A single set of thrusters is designed to perform multiple functions: station keeping maneuvers, momentum unloading, and attitude control. The thruster system can be selectively activated for different operations based on real-time spacecraft state, eliminating the need for separate dedicated thruster sets while maintaining all required capabilities
Solution Approach 2:
The patent combines station keeping and momentum management operations into a unified control framework that coordinates both functions using the same thruster hardware. By merging these previously separate functions into one integrated system, the spacecraft reduces mass and simplifies the propulsion subsystem while achieving both objectives concurrently
3Object-affected harmful factors
If thrusters are restricted in placement to avoid plume impingement, then antenna and solar panel safety is ensured, but torque generation capability is reduced
Solution Approach 1:
The control system dynamically adjusts thruster firing sequences and impulse magnitudes based on the spacecraft's current momentum storage state and orbital position. By coordinating station keeping and momentum unloading operations in time and space, the system achieves effective torque generation while maintaining safe thruster placement configurations that avoid plume impingement on sensitive components
Data Source
Figure 1A
Figure 1B
Figure 1C
AI summary
An operation of a spacecraft is controlled using an inner-loop control determining first control inputs for momentum exchange devices to control an orientation of the spacecraft and an outer-loop control determining second control inputs for thrusters of the spacecraft to concurrently control a pose of the spacecraft and a momentum stored by the momentum exchange devices of the spacecraft. The outer-loop control determines the second control inputs using a model of dynamics of the spacecraft including dynamics of the inner-loop control, such that the outer-loop control accounts for effects of actuation of the momentum exchange devices according to the first control inputs determined by the inner-loop control. The thrusters and the momentum exchange devices are controlled according to at least a portion of the first and the second control inputs.