Cluster Flight Research Articles

Distributed adaptive prescribed-time orbit containment control for satellite cluster flight

The distributed prescribed-time orbit containment control for the satellite cluster flight with multiple dynamic leaders is investigated. The directed information communication topology between followers is taken into account in the overall paper. When the satellite mass is assumed to be constant, a distributed prescribed-time orbit containment controller is, firstly, presented to drive the followers into the dynamic convex hull produced by multiple leaders. Then, the parameter uncertainty is considered, and a prescribed-time sliding mode estimator is introduced to estimate the desired velocity of each follower. Based on the estimated state, a novel distributed adaptive prescribed-time orbit containment control scheme is proposed. The Lyapunov stability theory is utilized to prove the prescribed-time stability of the closed-loop system. Finally, several numerical simulations and comparison of different control methods are provided to verify the effectiveness and superiority of the proposed control method.

Obstacle-Avoidance Distributed Reinforcement Learning Optimal Control for Spacecraft Cluster Flight

Obstacle-Avoidance Distributed Reinforcement Learning Optimal Control for Spacecraft Cluster Flight

Factors Influencing the Quality of Online Teaching: Application of DEMATEL and Cluster Technology

With the informationization of higher education, colleges and universities can fully apply online teaching mode to education and teaching. Therefore, analysis of factors affecting teaching quality of college teachers in online teaching can effectively make evaluation object (teachers) have a sense of achievement and pride, so as to mobilize enthusiasm of evaluation object and to stimulate the consciousness of honor and shame and consciousness of competition. This study adopts application of DEMATEL and Cluster technology, conducts a questionnaire survey on 5 colleges and universities in Henan Province, analyzes and identifies the teachers’ factors among factors affecting teaching quality of E-commerce courses, and analyzes comprehensive influence index of teachers’ factors, namely impact degree, affected degree, cause degree and centrality degree. A cluster flight is carried out on evaluation results of students. Results show that X2-2, X2-4, X2-5, and X4-3 represent high degree of centrality and high degree of cause, that is high importance of factor and the cause factor. The results of teacher evaluation can be divided into three groups by the K-means clustering method, and the clustering group shows significant significance for all research items (p < 0.05). The weights of X2-2, X2-4, X2-5, and X4-3 in cluster analysis also rank the top four, which is highly consistent with the results of DEMATEL’s research, demonstrating that application of DEMATEL and Cluster technology proposed is very maneuverable and scientific. Research results have important reference value for improving online teaching strategy, improving the quality of online teaching, and regulating teaching activities as a whole through the use of online teaching quality evaluation.

Pure Azimuth Passive Positioning Model for UAV Formations

In recent years, with the rapid development of the UAV industry, the traditional positioning equipment has been unable to carry out effective control processing. This paper mainly studies the pure azimuth passive positioning in the attempted formation flight of UAV. On the basis of in-depth analysis of the signals received by the passive receiving signal UAV, assuming that the deviation of the UAV position at the receiving point is under the controllable error range, analyzing the relationship between the known number and the size of the circular angle, obtaining the passive receiving point positioning model, and checking the results by the least squares method, the results show that the model sought in this paper The results show that the model is of good accuracy. This paper is of great importance for the position positioning and adjustment of UAV cluster flight by pure azimuthal passive positioning method.

A quantitative approach to density-based clustering of flight trajectories for efficient air traffic noise simulations

The continuous growth of air traffic and increased availability of open source data has enabled the application of data-driven approaches for the prediction of noise contours around airports. Aiming at efficient noise simulations, this contribution proposes a framework for the probabilistic description of the air traffic around an airport. The methodology is based on using the density-based clustering algorithm OPTICS to cluster flight trajectories. The clustered trajectories serve as a basis for the creation of backbone and dispersion tracks, which, together with a prescribed number of flight operations per aircraft type, provide a probabilistic description of the air traffic to the noise simulations. A major focus is given to quantitatively assess the sensitivity of the OPTICS algorithm to different hyper-parameters to reduce the dimensionality of the problem. This framework is demonstrated utilizing a dataset of ADS-B trajectory data associated with flights approaching Hannover airport. Noise simulations based on the ECAC Doc. 29 best-practice method are conducted using SoundPLAN. A good agreement between noise contours is obtained when comparing simulations performed using the proposed framework and the full dataset while the computational time required decreased. Furthermore, this approach identifies most of the trajectory patterns with the least amount of outliers.

Azimuth-only passive positioning technology of UAV based on triangulation and iteration

In recent years, the strategic position of bearing-only passive positioning technology has been continuously improved with the increasing application of UAV cluster flight in military and civil fields.This technology uses as few UAV signals as possible to adjust the position of the UAV formation, so as to achieve the purpose of improving the stealth of the UAV cluster and reducing the external interference.In this paper, the theory and application of the method are described in detail. There are four combinations of UAVs that abstract the demand for de-transmitting signals, and one of them is discussed in detail.

Constraint on Bounded Relative Distance for Robust MME Detection in Spaceborne Cluster Flight Netted Radar

In this paper, we investigate the robust maximum-minimum eigenvalue (MME) detection problem caused by this uncertainty of geometric configuration. Firstly, according to the proposed novel concept of spaceborne cluster flight netted radar (SCFNR) integrated cluster flight spacecraft with netted radar recently, we define the robust detector for the uncertainty of geometric configuration due to the mobility in SCFNR and give the condition about robust MME detector. Using the channel gain matrix in one CPI, the closed-form of the lower bound on the test statistic under the presence of target return, and the upper bound under the absence of target return are given respectively. Secondly, using the mobility model about transmitter-receiver pairs in SCFNR, we give the constraint on the bounded relative distance for robust MME detector in SCFNR. Finally, the effectiveness of the proposed constraint is validated through numerical calculations. The results show also that controlling the orbit elements about the transmitter and receiver platforms in SCFNR can make sure the robustness of MME and the relative distance bounded.

Optical Tracking System for Multi-UAV Clustering

This paper proposes an optical tracking system to realize the clustering of multiple unmanned aerial vehicles (UAVs). The system uses a laser spot as a visual recognition target to realize cluster flight operations in a complex environment. To reduce the interference of sunlight in the optical visual navigation and obtain the optimal combination of laser receiving devices, we selected lasers in a variety of spectrum bands and filter films with different light transmittances to conduct a comprehensive test. By performing a fluid simulation of the UAVs with the related modules mounted in different positions, the optimal installation position was selected to enhance the effect of the UAV wind field. An online learning tracking framework based on the multi-feature extraction of convolutional networks was developed to realize robust long-term visual tracking. In the tracking process, the tracking algorithm could train the detector online according to the status of the target and adaptively initialize the target. Finally, to verify the practical application performance of the clustering system, a group of UAVs was tested in flight. We verified that the proposed method and device exhibit a high feasibility and reliability.

Optimization of Transmitter-Receiver Pairing of Spaceborne Cluster Flight Netted Radar for Area Coverage and Target Detection

In this paper, we investigate the optimization problem of the transmitter-receiver pairing of spaceborne cluster flight netted radar (SCFNR) for area coverage and target detection. First of all, we propose the novel concept of SCFNR integrated cluster flight spacecraft with netted radar, the mobility model for bistatic radar pair with twin-satellite mode, and formulate the radar-target distance distribution function and radar-target distance product distribution function with geometric probability method. Secondly, by dividing surveillance region into grids, we define the 0-1 grid coverage matrix for bistatic radar and the transmitter-receiver pairing matrix for SCFNR with using radar equation and the radar-target distance distribution function, and we describe the optimal problem of transmitter-receiver pairing of SCFNR for area coverage and target detection by defining K-grid coverage matrix. Thirdly, we propose a new algorithm integrated particle swarm optimization with Hungarian algorithm (PSO-HA) to address the optimal problem, which is actually one-to-one pairing problem. Finally, we validate the effectiveness and reasonability of the proposed algorithm through numerical analysis.

Event-Triggered Adaptive Sliding Mode Attitude Containment Control for Microsatellite Cluster under Directed Graph

In order to investigate the attitude containment control problem for a microsatellite cluster, an event-triggered adaptive sliding mode attitude containment control algorithm is proposed for the satellite cluster flight system under directed topology, so that attitude of followers asymptotically converges to the convex hull formed by the leaders’ orientations. At first, the event-triggered control strategy is introduced into the attitude containment control problem for the microsatellite cluster. The triggering condition consisting of state-dependent and time-dependent function is designed to adjust control period and avoid the Zeno behaviour. When the function value meets the triggering condition, the event is triggered, state information is sampled, control law is computed, and actuators are updated, while the control action performed in nontriggering time is the same as the previous triggering instant. Then, in the presence of model uncertainties and external disturbances, an event-triggered adaptive sliding mode attitude containment control algorithm is presented under directed topology, and sufficient and necessary conditions for the followers to enter into the target area formed by the leaders are given. Furthermore, cell partitions from graph theory are employed to investigate the influence of information topology on steady states of followers, which provides theoretical basis for orientation design of cluster satellites. Finally, simulation results show that the proposed control strategy could reduce control execution frequency, as well as ensure the similar control performance with the time-triggered one, and followers belonging to the same cell have the same steady states.

Research on Transmission Capacity Characteristics of the Cluster Flight Spacecraft Network

In order to analyze the transmission capacity performance of the cluster flight spacecraft network, there are two different types of outage performance theory which are derived in this paper. First of all, by applying the mean value theorem of integrals, the expression of the outage probability of decode-and-forward relaying is derived. Subsequently, according to the Macdonald random variable form, the expression of the outage probability of amplify-and-forward is derived. By simulating the transmission capacity of decode-and-forward, the transmission capacity characteristics of a single hop and dual hops are analyzed. The simulation results showed that transmission capacity performance changes with the change of the time slot in the orbital hyperperiod, and the transmission capacity of a dual-hop relay has better performance than a single-hop transmission in the cluster flight spacecraft network.

Nodal distance distributions in cluster flight spacecraft network

The high‐speed flight of cluster flight spacecraft modules increases the uncertainty of network topology. In order to better design the orbital of the cluster flight spacecraft and improve the performance of cluster flight spacecraft network (CFSN), this paper studies the nodal distance distributions (NDDs). First, based on twin‐satellites mode, the mobility model of nodes is established. And then by adopting empirical statistical method and curve fitting method, the solution of the nodal distance density function in the CFSN is obtained. Second, the probability density function is applied to the model distance‐dependent path loss, and the probability density of path loss under the model is analyzed. Finally, the distributions of maximum and minimum distance among multiple nodes and the threshold range of nodal connection distance are derived, and the probabilistic connectivity matrix of any time slot in the orbital hyper‐period and spatial–temporal evolution graphs under different thresholds is obtained. The analytical results verify the feasibility of the model and the approximate solution of the NDDs in this paper. This method also provides a theoretical reference for the nodal connection in irregular wireless networks.

Decentralized fault-tolerant control for multiple electric sail relative motion at artificial Lagrange points

This paper establishes a distributed fault-tolerant control framework for E-sail relative motion at Sun-Earth artificial Lagrange points, capable of accounting for unexpected E-sail actuator fault like effectiveness loss and bias error. The E-sail relative motion problem is formulated on the linearized dynamics, and the steering control is conducted by suitably adjusting the sail attitude and sail lightness number. The proposed control strategy facilitates the E-sail relative distances to evolve within a bounded range and to synchronously converge to the desired values, while collision avoidance of the relative motion is ensured as well. In particular, the locally shared information among the E-sails is assumed to be characterized by their relative distances only, thus extending the existing results where the inter-sail communication capability is static. The concept of distributing multiple E-sails in cluster flight is useful for the deep-space formation missions such as the DARWIN mission, in which a multi-point measurement of the space environment is required. Illustrative examples show the validity of the proposed method in a typical mission scenario.

Transmit Power Allocation with Connectivity Probability for Multi-QoS in Cluster Flight Spacecraft Network

In this paper, we investigate the transmit power allocation problem to minimize the average packet error rate at the access point in the cluster flight spacecraft network, which adopts the CSMA/CA channel access mechanism. First, the node mobility, nodal distance distribution, and probabilistic adjacency matrix were formulated for cluster flight spacecraft network based on twin-satellite mode. Then, the optimization-theoretic model described the optimized transmit power allocation strategy and its implementation algorithm was proposed. And the problem of minimizing the packet error rate of the cluster flight spacecraft network system can be converted into maximizing the expectation of the binary probabilistic adjacency matrix, i.e., maximizing the sum of the nondiagonal elements in the probabilistic adjacency matrix. Due to discreteness of nodal distance distribution, Monte Carlo method was applied to solve the transmit power allocation problem. Yet importantly, the influence of node transmit power on the QoS performance of cluster flight spacecraft network was simulated and analyzed under the assumption of finite overall network transmit power and low traffic load. Finally, the results show that the pocket error rate increases with the provided traffic load, but the pocket error rate hardly changes with the same traffic load in different sequential time slots of any orbital hyperperiod or in the same time slot of different orbital hyperperiods, and by maximizing the sum of the nondiagonal elements in the probabilistic adjacency matrix, the pocket error rate minimum is achieved for a given total network transmit power at any time slot for cluster flight spacecraft network.

A distributed flocking control strategy for UAV groups

To ensure the information security of UAV groups, maximize the detection range of the UAV group and minimize the communication range, this paper improves Olfati–Saber’s flocking algorithm using virtual leader and integrates the multiple UAVs with real environment. The improved swarm control algorithm can help to make all agents accurately track the speed of virtual leaders. Then, we introduce the conception of virtual communication circle to control the communication power of each UAV, and the moving function of the target position is improved to meet the limited conditions of given communication distance, to ensure the non-collision and stable communication of the UAV during the moving process. All UAVs in the group system will keep converging, avoiding collision and the speed is the same as that of the virtual pilot. Therefore, multiple UAVs can track the virtual pilot for cluster flight and a distributed cooperative control strategy can be acquired. The simulation results show that the strategy proposed in this paper makes a better communication performance among UAVs in real time, and the UAV groups achieve the information more timely, which is proved to be an effective way to ensure the security communication among multiple UAVs.

Bounded motion design in the Earth zonal problem using differential algebra based normal form methods

Establishing long-term relative bounded motion between orbits in perturbed dynamics is a key challenge in astrodynamics to enable cluster flight with minimum propellant expenditure. In this work, we present an approach that allows for the design of long-term relative bounded motion considering a zonal gravitational model. Entire sets of orbits are obtained via high-order Taylor expansions of Poincare return maps about reference fixed points. The high-order normal form algorithm is used to determine a change in expansion variables of the map into normal form space, in which the phase space behavior is circular and can be easily parameterized by action–angle coordinates. The action–angle representation of the normal form coordinates is then used to parameterize the original Poincare return map and average it over a full phase space revolution by a path integral along the angle parameterization. As a result, the averaged nodal period and drift in the ascending node are obtained, for which the bounded motion conditions are straightforwardly imposed. Sets of highly accurate bounded orbits are obtained, extending over several thousand kilometers, and valid for decades.

Characteristics of Dynamic Connection and Path Spatial-temporal Evolution in Cluster Flight Spacecraft Network

簇飞行航天器模块的高速飞行增加了网络拓扑的不确定性.为优化簇飞行航天器的轨道设计，提升簇飞行航天器网络性能，在簇飞行航天器节点动态连接的基础上，开展基于概率连接矩阵的簇飞行航天器网络动态连接和路径时空演进特性研究.基于航天器双星伴飞模式，建立了簇飞行航天器节点移动模型，运用经验统计和曲线拟合的分析方法，得到簇飞行航天器网络节点间的距离密度函数；利用簇飞行航天器网络节点间相对距离有界的约束，给出节点连接距离的阈值范围；利用STK生成的轨道数据，通过给出序贯路径定义和一种新的矩阵乘法运算，得到节点多跳序贯路径的概率连接矩阵，分析轨道超周期内节点动态连接和路径时空演进特性，为簇飞行航天器网络的设计和优化提供理论参考.

UAV swarm autonomous control based on Internet of Things and artificial intelligence algorithms

At present, the UAV swarm positioning solution has the problems of poor positioning accuracy and instability. Therefore, it is necessary to design a sliding mode formation controller to realize formation. This study analyzes the self-service control strategy of the UAV swarm and establishes the behavior-based formation control strategy as the main research point of this article. This paper combines the Internet of Things and artificial intelligence algorithms to build an autonomous control model for the UAV swarm and designs the UAV formation control law from the disturbed and undisturbed conditions respectively. With reference to the basic architecture of the Internet of Things, this study imitates ZigBee’s self-organizing network to propose an adaptive networking scheme based on the Internet of Things by using the AP+STA working mode of the Internet of Things module in the node device. The results of the experiment show that the positioning accuracy of the UAV is high, which can meet the needs of cluster flight. Based on the Z-axis coordinates of the UAV, the accuracy of the laser distance measurement and the barometer value is significantly improved, the root mean square error is reduced, and the positioning result is significantly better than the data of direct traditional positioning.

Multi UAV Cluster Control Method Based on Virtual Core in Improved Artificial Potential Field

In this paper, a method of multi UAV cluster control based on improved artificial potential field (APF) is proposed. The k-means method is used to integrate and optimize the attractive force between UAVs, and the concept of virtual core is introduced to realize the cluster control and adaptive formation flight of multiple UAVs. The attractive disturbance component of the target point is introduced and the backtracking-filling method is proposed to solve the local minimum problem in the APF. The repulsion force in the APF can realize obstacle avoidance and collision avoidance, and the virtual core can control the UAV cluster to fly to the target point under the attractive force of potential field, so as to realize the track planning and multi aircraft cooperative task. In the process of cluster flight when the UAV fails, merges or dispatches, the method can realize cluster reconfiguration and the cluster control effect and task execution success rate can be improved. The simulation experiments in virtual APF and urban environment APF show the effectiveness of this method.

Safe deployment of cluster-flying nano-satellites using relative E/I vector separation

Nano-satellites cluster flight has attracted an increasing interest in the domain of distributed spacecraft system in recent years. As the first phase of a cluster flight mission, on-orbit deployment process constitutes a great technical challenge, since not only safe relative trajectories, but also practical operational constraints must be considered. To deal with these issues, the concept of relative Eccentricity/Inclination (E/I) vector separation was utilized in the safety concept design and the sequent release parameters solving, as it provides direct insight into the safety characteristics of relative motion. Accordingly, a novel operational methodology for the safe deployment of cluster-flying nano-satellites is provided. It can deterministically generate deployment sequences that ensure safe relative trajectories between released satellite (RS) pairs, as well as that between the launch vehicle (LV) and RSs, for enough long time interval. Particularly, according to our methodology, no maneuver efforts are required for the LV and RSs either during the deployment process or after deployment. Moreover, the proposed methodology adheres to practical constraints from either the LV or ground station. A typical simulation scenario was setup for the deployment process of the pioneering cluster flight mission - Satellite Mission for Swarming and Geolocation (SAMSON). Results demonstrate the feasibility and efficiency of our methodology.