Spacecraft Magnetic Pointing Control Under Geomagnetic Torque Limits
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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 control system complexity and often result in a stop state, especially when the inclined angle between the magnetic field and desired control torque is large, limiting the effectiveness of control.
Innovation Solution
A single-axis pointing pure magnetic control algorithm based on geometrical analysis, which involves acquiring specific vector coordinates, calculating an optimal control rotation axis, and adjusting control coefficients to generate a magnetic torque that interacts with the geomagnetic field, ensuring the torque is within the normal plane of the geomagnetic field, thereby minimizing interference and optimizing control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a single-axis PD control is used to generate desired control torque, then the control torque can be calculated according to T=Kpβ−Kd{dot over (β)}, but the torque direction is limited by the geomagnetic field and cannot point to any direction
Solution Approach 1:
The patent transforms the control problem from three-dimensional torque vector control to two-dimensional projection plane control. By projecting the desired control torque onto the normal plane of the geomagnetic field, the control system adapts to the magnetic field constraints while maintaining effectiveness in the controllable dimensions.
Solution Approach 2:
The patent changes the control parameters by introducing projection operations and adjusting torque components based on the geomagnetic field orientation. The control torque is recalculated as Tc = (T·n)×B where n is the normal vector of the geomagnetic field, transforming the torque parameters to match the magnetic field constraints.
2Productivity
If the magnetic field vector and desired control torque are projected onto the normal plane, then the control torque can be generated, but an interference torque component is generated in addition to the effective control torque
Solution Approach 1:
The patent converts the harmful interference torque into a beneficial control mechanism by deliberately introducing a virtual angular velocity component that generates a compensating torque. This virtual damping torque counteracts the interference torque, transforming the harmful effect into a useful control action that improves overall system performance.
Solution Approach 2:
The patent implements feedback control by calculating the interference torque based on the current magnetic field orientation and desired torque direction, then using this information to adjust the control torque components. The virtual damping term provides continuous feedback to suppress oscillations caused by interference torque.
3Reliability
If an effective control threshold is set (e.g., T>Td or inclined angle less than 45°), then control output can be generated when conditions are met, but the controller often enters a stop state when the threshold is not reached
Solution Approach 1:
The patent applies partial action by generating control torque components even when the desired torque cannot be fully realized due to magnetic field constraints. Instead of stopping control when thresholds are not met, the system generates the maximum possible torque within the constraints, ensuring continuous partial control action.
Solution Approach 2:
The patent ensures continuous control action by using the virtual angular velocity and damping mechanisms to maintain torque generation across all operating conditions. The control algorithm continuously calculates and applies torque components based on current state, eliminating stop states and ensuring uninterrupted control availability.
4Object-generated harmful factors
If the inclined angle between magnetic field vector and desired control torque is large, then the interference torque increases, but reducing the inclined angle limits the operational positions on spacecraft orbit
Solution Approach 1:
The patent makes the control system dynamic by continuously adapting the torque projection plane and virtual angular velocity based on the current orbital position and magnetic field orientation. This dynamic adaptation allows the system to maintain effective control across varying orbital conditions without being constrained by fixed geometric relationships.
Solution Approach 2:
The patent creates a universal control algorithm that functions across all orbital positions by using the virtual damping mechanism and adaptive projection. The same control framework handles both small and large inclined angles, making the system versatile for all spacecraft positions without requiring position-specific control modes.
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 simplifies the control system, enhances control efficiency, and allows for effective single-axis pointing, as demonstrated by simulation results showing reduced pointing error and controlled angular velocity, making it suitable for spacecraft operations.
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
Data Source
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.