Gimbaled Thruster Control for Spacecraft Station Keeping
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Solution Overview
Problem
Current methods for concurrent station keeping, attitude control, and momentum management of spacecraft using a single set of thrusters face challenges due to restrictions on thruster placement, limited computational resources, and the need for efficient fuel management, while maintaining precise orbit and orientation.
Innovation Solution
A model predictive control (MPC) system is implemented with a receding horizon approach, optimizing a cost function that considers thruster constraints, momentum unloading, and station keeping objectives, using a dual-loop control system with an inner-loop feedback controller and an outer-loop MPC to manage thruster inputs and momentum exchange devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If thrusters are placed to avoid plume impingement on antennas and solar panels, then deployment safety is improved, but the ability to provide pure torques without applying net force deteriorates
Solution Approach 1:
The system dynamically adjusts thruster firing sequences and combinations based on real-time spacecraft state (position, velocity, attitude, momentum) to simultaneously achieve plume avoidance, pure torque generation, and station keeping. The MPC controller optimizes thruster activation patterns that account for plume impingement constraints while maintaining control authority.
Solution Approach 2:
The system changes operational parameters including thruster firing duration, magnitude, and sequencing to generate pure torques without net force. By carefully controlling the timing and duration of thruster pulses, the system achieves attitude control objectives while canceling out translational effects through coordinated multi-thruster operations.
2Measurement precision
If model predictive control is implemented for autonomous spacecraft operation, then control precision is improved, but computational resource requirements increase
Solution Approach 1:
The MPC implementation is segmented into manageable computational tasks: prediction of future states, evaluation of cost function, optimization of control inputs, and application of commands. The receding horizon approach divides the control problem into discrete time steps, allowing the limited onboard processor to solve smaller sub-problems sequentially rather than tackling the entire horizon at once, thus reducing computational energy consumption while maintaining control accuracy.
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 solution enables precise and efficient station keeping, attitude control, and momentum management, improving fuel economy and maintaining spacecraft orientation within specified limits, while avoiding thruster plume impingement and preventing momentum device saturation.
Implementation Method 1
spacecraft are generally equipped with thrusters for station keeping maneuvers
Implementation Method 2
spacecraft can be disturbed by external torques that are generally absorbed by onboard momentum exchange devices, such as reaction wheels or control moment gyroscopes
Implementation Method 3
the stored angular momentum is periodically unloaded via the onboard thrusters
Data Source
Figure 1A
Figure 1B
Figure 1C
AI summary
A spacecraft including a spacecraft bus and a set of thrusters for changing a pose of the spacecraft. Wherein at least two thrusters are mounted on a gimbaled boom assembly connecting the two thrusters with the spacecraft bus, such that the two thrusters are coupled thrusters sharing the same gimbal angle. A model predictive controller to produce a solution for controlling thrusters of the spacecraft by optimizing a cost function over multiple receding horizons. The cost function is composed of a cost accumulated over the multiple receding horizons, including a cost accumulated over a first horizon using a dynamics governing a north-south position of the spacecraft, and a cost accumulated over a second horizon using a model of dynamics of the spacecraft governing an east-west position. A thruster controller to operate the thrusters according to their corresponding signals.