Spacecraft Magnetic Pointing Control Without Interference Torque
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Solution Overview
Problem
Conventional single-axis pointing magnetic control algorithms for spacecraft face inefficiencies due to interference torques generated by the geomagnetic field, leading to controller stop states and increased control system complexity, especially when the desired control torque direction is not perpendicular to the geomagnetic field.
Innovation Solution
A single-axis pointing pure magnetic control algorithm based on geometrical analysis, which calculates an optimal control rotation axis and adjusts control coefficients to ensure the magnetic control torque is within the geomagnetic field's normal plane, using affine transformations and PD control methods to generate rotation and damped angular accelerations, thereby overcoming the limitations of traditional methods.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional magnetic control algorithm is used, then control torque is generated to rotate the spacecraft, but interference torque is generated when the magnetic field vector is not perpendicular to the desired control torque
Solution Approach 1:
Instead of projecting the desired control torque onto the normal plane of the magnetic field (conventional approach), the patent inverts the approach by constructing the control torque directly within the normal plane using two orthogonal basis vectors. This inversion eliminates the interference torque component that arises from projection, as the control torque is now inherently aligned with the magnetorquer's capabilities.
Solution Approach 2:
The patent introduces a new dimensional framework by defining two orthogonal basis vectors (e1 and e2) in the normal plane of the magnetic field. The control torque is expressed as a linear combination of these basis vectors, transforming the control problem from a 3D projection operation into a 2D plane operation, which eliminates the interference torque issue.
2Reliability
If control threshold is set to ensure effectiveness (T>Td or angle<45°), then control reliability is improved, but controller enters stop state when threshold is not met
Solution Approach 1:
The patent converts the limitation of the magnetic field direction into a benefit by directly utilizing the normal plane of the magnetic field as the control torque plane. What was previously a constraint (magnetic field direction limiting control torque direction) becomes the foundation for a new control approach that eliminates interference torque and removes the need for control thresholds.
Solution Approach 2:
The patent fundamentally changes the parameter representation of control torque. Instead of using the magnitude and direction of the projected torque with threshold checks, the patent represents control torque as a linear combination of two basis vectors with continuous control coefficients, enabling continuous control without stop states.
3Measurement precision
If single-axis PD control is used with optimal torque direction along OB×OA, then control precision is improved, but system complexity increases due to rotational inertia and angular velocity considerations
Solution Approach 1:
The patent substitutes the conventional PD control mechanism (which requires complex calculations of rotational inertia, angular velocity, and torque projections) with a simplified magnetic field-based control mechanism. By expressing control torque directly in terms of magnetic field vectors and basis vectors, the patent eliminates the need for complex mechanical parameter calculations while maintaining control precision.
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
The algorithm enables efficient single-axis pointing control by minimizing interference torques and ensuring effective control torque generation, simplifying the control system and enabling safe and specific control modes for spacecraft, as demonstrated by simulation results.
Implementation Method 1
generate a magnetic torque by a magnetorquer and then the magnetic torque interacts with a geomagnetic field to generate a control torque T
Data Source
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AI summary
Provided is a single-axis pointing pure magnetic control algorithm for a spacecraft based on geometrical analysis to realize single-axis pointing control of the spacecraft through the pure magnetic control algorithm in which a magnetic torque is only output by a magnetorquer to interact with a geomagnetic field to generate a control torque. The algorithm uses a spatial geometry method to obtain an optimally controlled magnetic torque direction, thereby designing a PD controller. The problem that the traditional magnetic control method is low in efficiency and even cannot be controlled is overcome. The algorithm is simple and easy, can be used in the attitude control field of spacecrafts, and achieves the pointing control in point-to-sun of a solar array and point-to-ground of antennae.