Time-varying fault-tolerant formation tracking based cooperative control and guidance for multiple cruise missile systems under actuator failures and directed topologies

This paper studies time-varying fault-tolerant formation tracking problems for the multiple cruise missile system under directed topologies subjected to actuator failures. Firstly, the timevarying fault-tolerant formation tracking process for the multiple cruise missile system is divided into the guidance loop and the control loop. Then protocols are constructed to accomplish distributed fault-tolerant formation tracking in the guidance loop with the adaptive updating mechanism, in the condition where neither the knowledge about actuator malfunctions nor any global information of the communication topology remains available. Moreover, sufficient conditions to accomplish formation tracking are presented, and it is shown that the multiple cruise missile system can carry on the predefined time-varying fault-tolerant control (FTC) formation tracking through the active disturbances rejection controller (ADRC) and the proportion integration (PI) controller by the way of the fault-tolerant protocol utilizing the designed strategies, in the event of actuator failures. At last, numerical analysis and simulation are designed to verify the theoretical results.

Robust attitude control for rapid multi-target tracking in spacecraft formation flying

A robust attitude tracking control scheme for spacecraft formation flying is presented. The leader spacecraft with a rapid mobile antenna and a camera is modeled. While the camera is tracking the ground target, the antenna is tracking the follower spacecraft. By an angular velocity constraint and an angular constraint, two methods are proposed to compute the reference attitude profiles of the camera and antenna, respectively. To simplify the control design problem, this paper first derives the desired inverse system （DIS）, which can convert the attitude tracking problem of 3D space into the regulator problem. Based on DIS and sliding mode control （SMC）, a robust attitude tracking controller is developed in the presence of mass parameter uncertainties and external disturbance. By Lyapunov stability theory, the closed loop system stability can be achieved. The numerical simulations show that the proposed robust control scheme exhibits significant advantages for the multi-target attitude tracking of a two-spacecraft formation.

STK simulation design for satellite formation tracking mission with bidirectional communication

The problem of satellite formation tracking control is studied by using the tool, the satellite tool kit （STK ） software.To fight against gravitational perturbation rejection, a sliding mode controller for each satellite is proposed to accomplish the orbit trace and is then verified by the STK.For the purpose of accomplishing the formation tracking mission with bidirectional communication in STK,a time-share orderly calling plug-in is designed by C ＋＋,which gives solutions to the problems of the monopolization of computing resource and no return of the satellite identifier in the calculation center. The effectiveness of the decoupling approach is tested and verified by the STK.The simulation results obtained by the STK are more meaningful than those obtained by Matlab.

Bipartite Formation Tracking for Multi-Agent Systems Using Fully Distributed Dynamic Edge-Event-Triggered Protocol

In this study,the bipartite time-varying output formation tracking problem for heterogeneous multi-agent systems(MASs)with multiple leaders and switching commu-nication networks is considered.Note that the switching communication networks may be connected or disconnected.To address this problem,a novel reduced-dimensional observer-based fully distributed asynchronous dynamic edge-event-triggered output feedback control protocol is developed,and the Zeno behavior is ruled out.The theoretical analysis gives the admissible switching frequency and switching width under the proposed control protocol.Different from the existing works,the control protocol reduces the dimension of information to be transmitted between neighboring agents.Moreover,since an additional positive internal dynamic variable is introduced into the triggering functions,the control protocol can guarantee a larger inter-event time interval compared with previous results.Finally,a simulation example is given to verify the effectiveness and performance of the theoretical result.

Robust Adaptive Gain Higher Order Sliding Mode Observer Based Control-constrained Nonlinear Model Predictive Control for Spacecraft Formation Flying

This work deals with the development of a decentralized optimal control algorithm, along with a robust observer,for the relative motion control of spacecraft in leader-follower based formation. An adaptive gain higher order sliding mode observer has been proposed to estimate the velocity as well as unmeasured disturbances from the noisy position measurements.A differentiator structure containing the Lipschitz constant and Lebesgue measurable control input, is utilized for obtaining the estimates. Adaptive tuning algorithms are derived based on Lyapunov stability theory, for updating the observer gains,which will give enough flexibility in the choice of initial estimates.Moreover, it may help to cope with unexpected state jerks. The trajectory tracking problem is formulated as a finite horizon optimal control problem, which is solved online. The control constraints are incorporated by using a nonquadratic performance functional. An adaptive update law has been derived for tuning the step size in the optimization algorithm, which may help to improve the convergence speed. Moreover, it is an attractive alternative to the heuristic choice of step size for diverse operating conditions. The disturbance as well as state estimates from the higher order sliding mode observer are utilized by the plant output prediction model, which will improve the overall performance of the controller. The nonlinear dynamics defined in leader fixed Euler-Hill frame has been considered for the present work and the reference trajectories are generated using Hill-Clohessy-Wiltshire equations of unperturbed motion. The simulation results based on rigorous perturbation analysis are presented to confirm the robustness of the proposed approach.

Toward Coordination Control of Multiple Fish-Like Robots:Real-Time Vision-Based Pose Estimation and Tracking via Deep Neural Networks

Controlling multiple multi-joint fish-like robots has long captivated the attention of engineers and biologists,for which a fundamental but challenging topic is to robustly track the postures of the individuals in real time.This requires detecting multiple robots,estimating multi-joint postures,and tracking identities,as well as processing fast in real time.To the best of our knowledge,this challenge has not been tackled in the previous studies.In this paper,to precisely track the planar postures of multiple swimming multi-joint fish-like robots in real time,we propose a novel deep neural network-based method,named TAB-IOL.Its TAB part fuses the top-down and bottom-up approaches for vision-based pose estimation,while the IOL part with long short-term memory considers the motion constraints among joints for precise pose tracking.The satisfying performance of our TAB-IOL is verified by testing on a group of freely swimming fish-like robots in various scenarios with strong disturbances and by a deed comparison of accuracy,speed,and robustness with most state-of-the-art algorithms.Further,based on the precise pose estimation and tracking realized by our TAB-IOL,several formation control experiments are conducted for the group of fish-like robots.The results clearly demonstrate that our TAB-IOL lays a solid foundation for the coordination control of multiple fish-like robots in a real working environment.We believe our proposed method will facilitate the growth and development of related fields.

Design of Fighter Flight Formation for Aerial Refueling Racetrack Mission with Drogue-Hose Configuration

The flying of aircraft information necessitates the extension of the theory of formation flight control to allow for three dimensional formation maneuvers. A leader and wingman formation is considered. A rotating reference frame attached to the wingman is used and special attention is given to the motion of the leader relative to the wingman. A thirteen state, three inputs, and three disturbances signal control system which models the dynamics of a two aircraft formation in three dimensional spaces is developed. The theory of formation control was applied to KC-130J tanker and F-16 receiver configuration to study the availability of performing such mission on a large scale. Three formation flight control concepts are investigated. A proportional, integral, and derivative automatic control system to maintain the wing aircraft in the specified formation geometry despite the leader＇s maneuvers is designed, and its performance is examined in simulation experiments. By adding special compensation to each control law to maintain the design damping ratio and gain margin, it is possible to reach the desired performance satisfying the predefined relative distances boundaries.

Distributed velocity-free formation tracking control for clustered UAVs under virtual leader-follower framework

The collective formation control problem of a cluster of rotorcraft unmanned aerial vehicles(UAVs)is investigated in this article.The consensus tracking towards formation centroid with following UAVs forming a predefined configuration around the leader is considered as the objective.Unlike prior studies,the information of the central reference trajectory,which is deemed as a virtual leader in the leader-follower topology,is not directly accessible for partial nodes through the communication network.Therefore,a novel distributed formation tracking control scheme is promoted.Besides,a decentralized saturation observer is employed to estimate the reference acceleration signal of the virtual leader.In the absence of linear velocity measurement,two sliding manifolds are proposed by introducing the relative discrepancy terms of position and velocity.Then a smooth saturation operator in the form of a sigmoid function is applied to generate the command force input.Moreover,under the dilemma of constrained capabilities of the airborne sensors equipped on the rotorcrafts,the angular velocity is difficult to acquire.Two cascaded auxiliary attitude error systems are established on each rotorcraft system to synthesize the rotating torque with no need to require the angular velocity measurement.Due to the strong coupling and nonlinearity of the rotorcraft UAV system,the command angular velocity and the derivatives of command input are hard to obtain.Then a continuous nonlinear differentiator is proposed to work with the difficulties in deriving the explicit expression of system derivatives.Thereafter,a detailed stability analysis is conducted progressively on the angular control loop,reference trajectory observer loop,and the position control loop.A simulation scheme for a cluster of four rotorcraft UAVs tracking sinusoidal trajectory are presented and the formation control results are proven advantageous in comparison with the control protocol in previous literature.

Formation tracking control for time-delayed multi-agent systems with second-order dynamics

In this paper, formation tracking control problems for second-order multi-agent systems（MASs） with time-varying delays are studied, specifically those where the position and velocity of followers are designed to form a time-varying formation while tracking those of the leader. A neighboring relative state information based formation tracking protocol with an unknown gain matrix and time-varying delays is presented. The formation tracking problems are then transformed into asymptotically stable problems. Based on the Lyapunov-Krasovskii functional approach, conditions sufficient for second-order MASs with time-varying delays to realize formation tracking are examined. An approach to obtain the unknown gain matrix is given and, since neighboring relative velocity information is difficult to measure in practical applications, a formation tracking protocol with time-varying delays using only neighboring relative position information is introduced. The proposed results can be used on target enclosing problems for MASs with second-order dynamics and time-varying delays. An application for target enclosing by multiple unmanned aerial vehicles（UAVs） is given to demonstrate the feasibility of theoretical results.

Fully distributed time-varying formation tracking control for multiple quadrotor vehicles via finite-time convergent extended state observer

This paper investigates a time-varying anti-disturbance formation problem for a group of quadrotor aircrafts with time-varying uncertainties and a directed interaction topology.A novel Finite-Time Convergent Extended State Observer(FTCESO)based fully-distributed formation control scheme is proposed to enhance the disturbance rejection and the formation tracking performances for networked quadrotors.By adopting the hierarchical control strategy,the multiquadrotor system is separated into two subsystems:the outer-loop cooperative subsystem and the inner-loop attitude subsystem.In the outer-loop subsystem,with the estimation of disturbing forces and uncertain dynamics from FTCESOs,an adaptive consensus theory based cooperative controller is exploited to ensure the multiple quadrotors form and maintain a time-varying pattern relying only on the positions of the neighboring aircrafts.In the inner-loop subsystem,the desired attitude generated by the cooperative control law is stably tracked under a FTCESO-based attitude controller in a finite time.Based on a detailed algorithm to specify the cooperative control protocol,the feasibility condition to achieve the time-varying anti-disturbance formation tracking is derived and the rigorous analysis of the whole closed-loop multi-quadrotor system is given.Some numerical examples are conducted to intuitively demonstrate the effectiveness and the improvements of the proposed control framework.

Behavior-based Autonomous Navigation and Formation Control of Mobile Robots in Unknown Cluttered Dynamic Environments with Dynamic Target Tracking

While different species in nature have safely solved the problem of navigation in a dynamic environment, this remains a challenging task for researchers around the world. The paper addresses the problem of autonomous navigation in an unknown dynamic environment for a single and a group of three wheeled omnidirectional mobile robots(TWOMRs). The robot has to track a dynamic target while avoiding dynamic obstacles and dynamic walls in an unknown and very dense environment. It adopts a behavior-based controller that consists of four behaviors: "target tracking", "obstacle avoidance", "dynamic wall following" and "avoid robots". The paper considers the problem of kinematic saturation. In addition, it introduces a strategy for predicting the velocity of dynamic obstacles based on two successive measurements of the ultrasonic sensors to calculate the velocity of the obstacle expressed in the sensor frame. Furthermore, the paper proposes a strategy to deal with dynamic walls even when they have U-like or V-like shapes. The approach can also deal with the formation control of a group of robots based on the leader-follower structure and the behavior-based control, where the robots have to get together and maintain a given formation while navigating toward the target, avoiding obstacles and walls in a dynamic environment. The effectiveness of the proposed approaches is demonstrated via simulation.

Time-varying formation finite-time tracking control for multi-UAV systems under jointly connected topologies

Purpose–The purpose of this paper is to investigate the time-varying finite-time formation tracking control problem for multiple unmanned aerial vehicle systems under switching topologies,where the states of the unmanned aerial vehicles need to form desired time-varying formations while tracking the trajectory of the virtual leader in finite time under jointly connected topologies.Design/methodology/approach–A consensus-based formation control protocol is constructed to achieve the desired formation.In this paper,the time-varying formation is specified by a piecewise continuously differentiable vector,while the finite-time convergence is guaranteed by utilizing a non-linear function.Based on the graph theory,the finite-time stability of the close-loop system with the proposed control protocol under jointly connected topologies is proven by applying LaSalle’s invariance principle and the theory of homogeneity with dilation.Findings–The effectiveness of the proposed protocol is verified by numerical simulations.Consequently,the proposed protocol can successfully achieve the predefined time-varying formation in finite time under jointly connected topologies while tracking the trajectory generated by the leader.Originality/value–This paper proposes a solution to simultaneously solve the control problems of time-varying formation tracking,finite-time convergence,and switching topologies.

Output formation tracking for networked systems with limited energy and aperiodic silence

For leader-following networked systems with the topology switching and the aperiodic silence,limited-energy output formation tracking problems are investigated.Firstly,a new output formation tracking control protocol is proposed,which contains two components associated with the communication interactions between the leader and tracking intelligent agents and the communication interactions among tracking intelligent agents,respectively,and the aperiodic silence,the topology switching and the energy constraint index is introduced properly.Then,a two-step transformation method is presented to separate the whole dynamics of a networked system into the relative dynamics between the leader and tracking intelligent agents and the dynamics of the leader,and sufficient conditions for limited-energy output formation tracking for networked systems with limited energy and aperiodic silence are presented,which are extended into networked systems without the aperiodic silence.Especially,a partition checking algorithm is presented to check limitedenergy output formation tracking design criteria.Finally,a numerical example is illustrated to demonstrate the validness of theoretical results.

双无人机对地快速移动目标跟踪的构型设计与控制方法

为实现对地面快速移动目标的探测跟踪,基于无人机侦察载荷的误差模型,设计了双无人机编队跟踪目标的构型与跟踪控制律。面向持续跟踪的典型应用场景,设计了基于Leader-Follower的双机编队构型,并基于相机误差模型建立了双无人机探测叠加区域的误差分布模型,以此确定了目标与无人机编队的位置关系。之后,基于无人机与目标的视觉关系定义长机的矢量前置角和与目标之间的距离为跟踪误差,设计了基于李雅普诺夫方法的跟踪控制律,并证明跟踪控制的渐近稳定性。设计了僚机相对于长机的编队控制律,以保持双机平行编队的构型。仿真结果表明,目标机动运动时,双无人机系统能够在较短时间内收敛,实现对目标的持续稳定跟踪。

异构多智能体的数据驱动输出一致性跟踪控制

针对一类异构多智能体编队一致性跟踪控制问题,考虑到实际系统中控制输入和输出均基于离散采样数据,且部分状态信息无法通过传感器获取,提出一种数据驱动的异构多智能体一致性输出跟踪控制方案。该方案利用数字采样控制方法和离散时间输入-输出采样数据,设计了包含无人机和无人车的异构多智能体一致性跟踪控制策略。通过状态观测器,利用降维输出信息实现了对全维状态信息的一致性跟踪控制。采用基于收缩映射原理的稳定性分析,验证了所提出的一致性跟踪控制方案对于每个闭环信号的有界性。同时,通过数值仿真验证了理论分析结果以及无人机和无人车的一致性跟踪控制性能。

有翼飞行器初制导阶段两段式协同集结方法

针对多枚有翼飞行器初制导阶段跨大空域飞行的协同集结问题,将协同集结问题转化为初始部署点到编队协同飞行区域之间的时间与位置协同问题。将协同集结过程划分为两个阶段,第一阶段飞行器间无信息交互,设计了带有集结角度约束的第一阶段时间协同集结方法,为各枚飞行器指定共同的集结时间和集结角度,采用模糊逻辑实现航迹控制与速度控制的合理分配,在可靠建立通信拓扑且满足终端放宽判断条件后,转入第二阶段协同集结飞行。第二阶段飞行器利用相互间构建的通信拓扑交互信息,为跟随者飞行器设计了基于编队跟踪控制的协同集结方法,通过李雅普诺夫理论对闭环系统稳定性进行了证明。仿真算例验证了所提方法的有效性。

无动力飞行器分布式有限时间编队跟踪控制

针对无动力飞行器再入过程中的编队控制问题,基于虚拟领导者的二阶系统一致性控制理论,优化了协调变量并引入过渡环节,提出了一种集结时间可调的分布式编队保持与切换控制算法。该算法结合飞行能力和编队任务需求,允许无动力飞行器的高程在一定范围内变化,在线实现对多无动力飞行器相对横程和相对纵程的精确控制。仿真结果表明,该算法在编队形成与保持、编队构型切换和编队横向规避场景下,均可实现对期望编队构型的精确控制,并且仿真过程还加入了地球曲率和自转效应对再入动力学的影响。算法同时能够适应偏差随机的气动系数和大气密度的组合拉偏,具有良好的鲁棒性。

Cooperative Formation Control of Autonomous Underwater Vehicles:An Overview

Formation control is a cooperative control concept in which multiple autonomous underwater mobile robots are deployed for a group motion and/or control mission. This paper presents a brief review on various cooperative search and formation control strategies for multiple autonomous underwater vehicles （AUV） based on literature reported till date. Various cooperative and formation control schemes for collecting huge amount of data based on formation regulation control and formation tracking control are discussed. To address the challenge of detecting AUV failure in the fleet, communication issues, collision and obstacle avoidance are also taken into attention. Stability analysis of the feasible formation is also presented. This paper may be intended to serve as a convenient reference for the further research on formation control of multiple underwater mobile robots.

面向海洋勘测的多水下机器人编队跟踪控制研究

本文研究面向海洋勘测任务的多水下机器人系统编队跟踪控制分析和设计问题。首先,以有向图为工具,建立水下机器人之间的信息交互模型,并利用局部相邻个体的信息构建了基于一致性的协议。然后,提出多水下机器人系统实现编队跟踪控制的充分条件。通过分析证明,若期望的编队满足给定条件,则多水下机器人系统可实现预定义的编队队形。此外,通过将编队控制协议增益矩阵计算转化为代数黎卡提方程求解问题,给出了一种确定编队控制协议矩阵的新方法。最后,通过数值模拟验证了所提方法的有效性。

基于速度前馈的无人机编队控制

对旋翼无人机编队控制进行了研究,分析并简化了无人机模型;采用信息传递策略,提出了结合前馈与反馈的控制策略,前馈信息为长机实时速度;仿真测试显示,该策略在响应速度、稳定性和超调量上优于传统P控制器和PID控制器;通过构建两架四旋翼无人机系统,进行了编队飞行实验,实验结果证实了策略的有效性;该策略在工程应用中显示出价值和潜力,为旋翼类多无人机编队控制提供了解决方案。