Satellite Attitude Steering to Avoid Singularity Command Spikes
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Solution Overview
Problem
Existing attitude steering laws for satellites generate undesirable command dynamics due to singularity conditions when the primary and secondary vectors become collinear, leading to infinite rate commands that exceed the satellite's maneuvering capabilities.
Innovation Solution
The satellite controller calculates alternate vectors during singularity events, blending them with nominal vectors to smooth maneuvers and avoid unplanned jerks or rotations, by projecting vectors onto a two-dimensional plane and determining a normal vector to minimize command dynamics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional attitude steering laws are used to control satellite orientation, then the satellite can maintain its orbit and point to targets, but singularity conditions occur when primary and secondary vectors become collinear, generating infinite rate commands that exceed maneuvering capabilities
Solution Approach 1:
The system performs preliminary detection of singularity conditions by monitoring the angular separation between primary and secondary vectors. Before the vectors become collinear (singularity point), the system proactively switches to an alternate vector configuration, preventing the occurrence of infinite rate commands and ensuring continuous stable operation
Solution Approach 2:
An alternate vector configuration serves as an intermediary solution when the primary vector configuration approaches singularity. The system calculates alternate vectors that maintain the required attitude control functionality while avoiding the collinear condition, effectively mediating between the conflicting requirements of maintaining orbit and avoiding singularities
2Ease of operation
If the satellite uses nominal vectors for attitude control, then the control system operates normally, but during singularity events the commands become discontinuous causing unplanned jerks or rotations
Solution Approach 1:
The system dynamically adjusts the vector configuration based on the operational state. When operating normally, it uses simple nominal vectors for ease of operation. When approaching singularity, it transitions to alternate vectors, creating a dynamic control system that adapts to maintain command continuity and prevent discontinuities
Solution Approach 2:
The system changes the parameters of the vector configuration by calculating and using alternate vectors with different angular relationships. This parameter change allows the control system to maintain simplicity while avoiding the singularity condition that causes command discontinuities and unplanned maneuvers
Data Source
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Figure 3A~3C
AI summary
Methods, apparatus, and articles of manufacture to minimize command dynamics of a satellite are disclosed. An example apparatus includes a steering law module to calculate a first set of vectors to maneuver a space vehicle, and calculate a second set of vectors based on projecting the first set of vectors onto a fixed plane. The apparatus further includes an attitude controller to generate an attitude command based on the first and the second sets of vectors to prevent an unplanned rotation by the space vehicle.