Spacecraft Slew Guidance Minimizing Energy and Time
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Solution Overview
Problem
Current methods for slewing a spacecraft or similar bodies from an initial state to a desired state profile are inefficient in terms of time and energy usage, often resulting in lag, oscillation, or instability, which affects maneuver performance and energy efficiency.
Innovation Solution
A method that involves obtaining a time profile of desired future states, sequentially searching for the earliest achievable state, calculating minimum-energy slews, and executing the chosen slew while adhering to angular rate and acceleration limits, using a processor to generate attitude commands and an attitude control system to implement the slew.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If traditional slew methods are used, then the spacecraft can reach the desired state, but the time and energy usage are excessive
Solution Approach 1:
The method performs preliminary calculations to determine the earliest achievable state and minimum-energy slew path before execution. By pre-computing the optimal trajectory that satisfies angular rate and acceleration limits, the system avoids suboptimal paths during actual slewing, thereby reducing both time and energy consumption simultaneously
Solution Approach 2:
The invention dynamically adjusts the slew profile by searching through multiple possible future states and selecting the optimal path. The system continuously evaluates different trajectory options and adapts the commanded attitude profile to achieve the earliest achievable state with minimum energy, rather than following a fixed predetermined path
2Loss of time
If aggressive slew commands are issued to reduce time, then the slew time decreases, but the spacecraft becomes unstable and oscillates
Solution Approach 1:
The method incorporates feedback by continuously monitoring the spacecraft's actual attitude and comparing it with the commanded profile. The system adjusts the slew commands based on the spacecraft's response, ensuring that angular rate and acceleration limits are not exceeded, thereby maintaining stability while achieving fast slewing
Solution Approach 2:
Before issuing slew commands, the system pre-calculates the optimal trajectory that inherently satisfies stability constraints. By determining the earliest achievable state through preliminary analysis of angular rate and acceleration limits, the system generates commands that are both fast and stable without requiring aggressive corrections during execution
3Ease of operation
If simple slew commands are used, then the system is easy to operate, but the maneuver performance and accuracy are poor
Solution Approach 1:
The system performs self-optimization by automatically calculating the minimum-energy slew path and earliest achievable state without requiring manual intervention. The processor autonomously evaluates multiple trajectory options and selects the optimal command profile, achieving high maneuver accuracy while maintaining ease of operation through automated decision-making
Solution Approach 2:
The method pre-computes the optimal slew trajectory including all necessary attitude adjustments and timing information before execution. This preliminary calculation ensures high maneuver accuracy by accounting for spacecraft dynamics and constraints, while the automated nature of the calculation maintains ease of operation
Data Source
AI summary
A method is adapted for slewing a body from an initial state to merge with a desired state profile. In an embodiment, the method includes the steps of (a) obtaining data indicative of a time profile of desired future states for the body; (b) searching sequentially through the time profile of desired future states; (c) calculating several slews for the body from the initial state to each of the desired future states; (d) determining the earliest future state to which the body can actually slew; (e) choosing the minimum-energy slew to that state; and (f) causing the body to perform that chosen slew.