This work presents a novel self-organizing control method for mega constellations to meet the continuous Earth observation requirements. In order to decrease the TT&C pressure caused by numerous satellites, constellation satellites are not controlled according to the designed configurations but are controlled with respect to intersatellite constraints. By analyzing the street-of-coverage (SOC) of coplanar constellation satellites, the continuous coverage constraint of the mega constellation is transformed into constraints of the right ascension of ascending node (RAAN) and relative motion bound between every two adjacent coplanar satellites. The proposed continuous coverage constraint can be satisfied by most ongoing or planned mega constellations. Artificial potential functions (APFs) are used to realize self-organizing control. The scale-independent relative orbital elements (SIROEs) are innovatively presented as the self-organizing control variables. Using the Gaussian equations and Lyapunov’s theory, the stability of the APF control in quadratic form is proven, from which it can be concluded that the APF control variables of the controlled satellite should have the same time derivative as the target satellite states under two-body Keplerian motion condition, and SIROEs are ideal choices. The proposed controllers and self-organizing rules are verified in the sub-constellation of the GW-2 mega constellation by simulation. The results demonstrate the goodness in control effect and ground coverage performance.

The UAV industry has witnessed an unprecedented boom in recent years. Among various kinds of UAV platforms, the vertical take-off and landing (VTOL) aircraft with fixed-wing configurations has received more and more attention due to its flexibility and long-distance flying abilities. However, due to the fact that the advance ratio of regular propeller systems during the cruise phase is significantly higher than that during the VTOL phase, a variable-pitch propeller system is proposed and designed which can be applied without additional propulsion mechanisms during both flying stages. Thus, a VTOL aircraft platform is proposed based on the propulsion system constructed of variable-pitch propellers, and appropriate control manners are precisely analyzed, especially during its VTOL phase. As a basic propulsion system, a nonlinear model for variable-pitch propellers is constructed, and an optimization-based control allocation module is developed because of its multi-solution and high-order characteristics. Finally, the objective function is designed according to the stability and energy consumption requirements. Simulation experiments demonstrate that the proposed controller is able to lower energy consumption and maintain the stability of the aircraft while tracking aggressive trajectories for large-scale VTOLs with noises at the same time.

Traditional station-keeping methods of mega constellations require massive TT&C information of satellites and frequent maintenance control due to the ground centralized framework and the influence of the low-Earth-orbit perturbations. This article innovatively proposes the self-organizing maintenance method for mega Walker constellations. The expected minimum coverage multiplicity of the constellation can be achieved by intersatellite cooperation with very low control frequency and consumption. The analytical relationship between the minimum coverage multiplicity and the relative orbital elements between adjacent coplanar satellites is established based on the 2-D map theory. Based on that, the intersatellite motion constraint is derived under the minimum coverage multiplicity requirement. By analyzing the time derivatives of the intersatellite coverage constraint, the self-organizing maintenance rules by means of limit cycle control of semimajor axes are formulated. The self-organizing maintenance method is verified based on the GW-A59 constellation. The maintenance performance of the minimum coverage multiplicity, the average control frequency, and the average control consumption of the proposed method are much better than the relative station-keeping method. Except for the good performance in maintenance, the self-organizing method only requires relative motion states between adjacent satellites, that enables more distributed and robust missions for mega constellations.