基于SO(3)的多四旋翼无人机编队协同控制

针对多四旋翼无人机系统的编队飞行问题,提出了基于特殊正交群SO(3)的协同控制设计方法.在给出编队空间队形和通信拓扑描述后,建立了多四旋翼无人机系统SO(3)控制模型.由于SO(3)与传统俯仰/偏航/滚转三通道模型具有不同的结构,文中进一步研究了SO(3)中无人机之间相对误差的表示方法,设计了适用于多飞行器的SO(3)控制器实现对编队和姿态的协同控制.推力控制器用于调节无人机的位置与速度,并在此基础上构造旋转矩阵形式的姿态协同指令.文中相应设计了SO(3)姿态控制器用于实现指令跟踪,最后从理论上对协同稳定性进行了分析.提出的控制方法能够使得多四旋翼无人机形成期望的队形,并且保持姿态一致进行稳定飞行.仿真结果验证了本文方法的有效性.     

分布式多无人机的时变编队非线性控制设计

研究了基于分布式通信网络的多无人机时变编队控制问题,考虑到外界扰动对多无人机协同编队系统的影响,提出一种新的连续非线性鲁棒编队控制方法.首先基于一致性方法构造了分布式无人机编队误差系统,降低了编队控制器对全局编队信息的要求;然后采用一种基于误差符号函数积分的鲁棒控制算法补偿未知外界扰动的影响,提高了无人机编队系统的鲁棒性,并基于Lyapunov分析的方法,证明了多无人机编队误差的半全局渐进收敛性;最后在四旋翼无人机编队实验平台上进行了多无人机时变编队的实时实验验证,实验结果表明,所提出的分布式编队控制算法可以实现多无人机时变编队控制,且具有较好的协同性能和抗干扰能力.     

基于Dubins曲线的一致性编队集结控制

针对无人机编队系统如何快速有效组建编队并完成集结的问题,提出一种基于Dubins曲线的一致性编队集结控制算法.首先综合考虑编队集结的具体要求,为不同初始位姿的无人机设计Dubins集结路径,提出一种基于定点集结和伴航集结相结合的控制策略,通过一致性控制协议,形成松散编队;然后通过精准航迹一致性控制协议,调整机间距离,压缩队形,形成紧密编队,实现完整的编队集结控制.仿真结果表明,上述算法能够快速有效地实现多无人机编队的组建编队、完成集结.     

基于一致性的小型四旋翼机群自主编队分布式运动规划

设计一种小型四旋翼无人机群起飞后自主形成正多边形编队的分布式运动规划方法.在四旋翼无人机的串级控制系统框架下,分布式编队控制器以简化agent模型为基础,同时采用平均一致性算法和有领导一致性算法,共同产生各无人机位置与偏航角的期望轨迹.讨论了达成最终协调目标队形的拓扑条件,并给出一种基于有向Hamilton环的通信拓扑设计方案.最后通过数值仿真验证了所提出算法的有效性.     

无人机吊挂飞行的非线性控制方法设计

针对四旋翼无人机吊挂飞行系统,本文设计了一种新型控制策略.本文首先建立了四旋翼无人机吊挂系统的数学模型.其中负载被看作由刚性绳悬挂在四旋翼无人机重心位置的质点.之后本文通过能量分析的方法设计了针对此系统的非线性控制器.本文提出的控制方法可以在抑制吊挂负载摆动的同时将四旋翼无人机移动到目标位置.本文运用李雅普诺夫稳定性分析和拉塞尔不变性原理对闭环系统的稳定性进行了证明.最后,通过数值仿真,分别将本控制器镇定控制和调节控制的控制效果与线性二次调节器(linear-quadratic regulator,LQR)控制器进行了对比.     

一种可倾斜六旋翼无人机容错控制方法

常规六旋翼无人机在单个旋翼完全失效后, 存在姿态与高度不完全可控的情况, 此时采取降级控制策略会 使无人机失去静态悬停能力. 针对此问题, 本文提出了一种可倾斜旋翼的容错控制方法, 在经典旋翼结构布局的基 础之上, 将其中一个旋翼设计成可倾斜结构, 通过倾斜角度的改变与控制分配重构, 无人机在任意单个旋翼完全失 效后均能保持力与力矩的平衡. 利用线性规划方法得到无人机的可达力矩集, 同时对电机饱和度进行分析, 确定了 不同旋翼失效后的最优倾斜角. 搭建飞行测试平台进行对比验证, 实验结果表明, 本文提出的方法具有良好的容错 效果与鲁棒性, 能够保证六旋翼无人机在故障后的稳定飞行与平稳降落.     

基于鸽群行为机制的多无人机自主编队

受启发于无人机(unmanned aerial vehicle,UAV)编队飞行与生物群体社会性行为的相似性,本文提出了一种基于鸽群行为机制的多无人机自主编队控制方法.首先通过模仿鸽群特有的层级行为,建立了鸽群行为机制模型.该模型在已有群集模型基础上,采用有向图和人工势场理论对鸽群中的拓扑结构和领导机制进行建模.在深入分析无人机自主编队飞行仿生机理的基础上,设计了一种基于鸽群行为机制的无人机自主编队控制器.该控制器以鸽群行为机制模型为核心,还包含两个辅助环节,即控制指令解算器和状态转换器.最后,通过系列仿真实验验证了无人机群可在本文所设计的无人机自主编队控制器作用下形成预期的编队队形,并可在复杂长机运动条件下保持队形.     

多无人机编队递归非奇异终端滑模容错控制

为解决四旋翼无人机编队飞行过程中易受到外部干扰、空气阻力、执行器故障等不确定因素影响的问题,提出了一种基于补偿函数观测器(CFO)的递归非奇异终端滑模控制(RNTSMC)方法来提高四旋翼无人机编队系统性能。首先,引入具有高精度估计的补偿函数观测器,实时估计外部干扰、执行器故障等信息,通过设计递归积分终端滑模面改进非奇异终端滑模面等效控制器对估计信息进行补偿控制,并给定滑模面初始值,保证两滑模面依次连续到达平衡点,确保跟踪误差在有限的时间内快速收敛到0。其次,根据长机-僚机法建立编队模型,基于滑模控制理论,设计编队协同控制器,保证无人机编队完成飞行任务。最后,通过对比仿真结果表明,该方法对四旋翼无人机编队具有良好的容错性能。     

四旋翼无人机PDF控制系统设计和抗干扰分析

针对传统的PID控制方法在对四旋翼无人机进行控制时动态响应差,抗干扰能力低等局限性,不能够满足高精度要求的四旋翼无人机应用场合的问题。本文以四旋翼无人机的姿态控制为研究对象,通过采用基于伪微分反馈(PDF)控制策略来设计其飞行控制器,以提高动态响应性能和抗干扰能力。在对四旋翼无人机数学建模的基础上,将PDF控制策略引入到四旋翼姿态控制中,提出基于四旋翼无人机对象的PDF控制设计方法,并分别完成PID、PDF控制器的设计和动态仿真。通过对仿真结果比较、分析表明PDF控制与PID姿态控制器相比,系统超调量小,具有更好的鲁棒性和抗干扰能力。     

基于方位信息的无人机编队控制设计与验证

本文主要研究了无人机编队的抗扰跟踪控制设计. 针对各无人机只能获取邻机方位信息的情况, 文章设计了一种新的非线性控制器以完成多无人机系统的编队形成与跟踪任务. 考虑到无人机系统易受外界扰动影响的特性, 采用Leader-Follower式编队方法, 通过引入Leader位置信息来矫正基于方位信息的无人机编队系统的位置漂移.将反步法设计结合自适应设计与鲁棒控制设计, 来补偿未知参数与未知外界扰动对多无人机编队系统造成的影响,提高了多无人机方位编队系统的鲁棒性. 然后, 基于Lyapunov分析方法证明了系统的稳定性. 最后, 搭建了四旋翼无人机编队实验平台, 进行了基于方位信息的编队形成与跟踪飞行实验, 并与PD控制器进行了对比实验. 飞行实验结果验证了算法的有效性与实用性.     

Aerial cooperative transporting and assembling control using multiple quadrotor–manipulator systems

In this paper, a fully distributed control scheme for aerial cooperative transporting and assembling is proposed using multiple quadrotor–manipulator systems with each quadrotor equipped with a robotic manipulator. First, the kinematic and dynamic models of a quadrotor with multi-Degree of Freedom (DOF) robotic manipulator are established together using Euler–Lagrange equations. Based on the aggregated dynamic model, the control scheme consisting of position controller, attitude controller and manipulator controller is presented. Regarding cooperative transporting and assembling, multiple quadrotor–manipulator systems should be able to form a desired formation without collision among quadrotors from any initial position. The desired formation is achieved by the distributed position controller and attitude controller, while the collision avoidance is guaranteed by an artificial potential function method. Then, the transporting and assembling tasks request the manipulators to reach the desired angles cooperatively, which is achieved by the distributed manipulator controller. The overall stability of the closed-loop system is proven by a Lyapunov method and Matrosov's theorem. In the end, the proposed control scheme is simplified for the real application and then validated by two formation flying missions of four quadrotors with 2-DOF manipulators.     

Min–max time consensus tracking on a multi-quadrotor testbed

In this work, min–max time consensus tracking is implemented on a multi-quadrotor testbed. The trajectory of a leader quadrotor is generated manually. The remaining quadrotors converge onto this reference trajectory in min–max time using a local feedback control strategy which is known to be globally optimal. Further, the effect of finite communication/measurement rate on consensus tracking is analysed. The bounds on the deviations of the trajectories due to finite communication/measurement rate are characterized. The theoretical claims made are verified through experiments.     

Adaptive prescribed time control for quadrotor formation with stochastic links failure

The formation control for multiple quadrotors subject to maintaining the formation configuration and collision avoidance in the situation of stochastic links failure is investigated in this paper. First, the distributed formation controller is designed, the position controller is developed to manage the desired formation of position, and the attitude controller is developed to control the translation and rotation movements of the quadrotor. Then, in order to avoid the collisions between multiple quadrotors and the obstacles, a potential energy function method is introduced into the quadrotor formation control combined with the nest adaptive control. Inspired by the design of event trigger controller, a communication compensation controller is designed to ensure the stability of quadrotor formation under the condition of random communication interruption and recovery. Moreover, a prescribed time function is designed, which means the convergence time of the formation system can be set in advance. The prescribed time stability of the formation control system is proved by Lyapunov theory. Finally, the simulation results verify the effectiveness and superiority of this method.     

Outdoor cooperative flight using decentralized consensus algorithm and a guaranteed real-time communication protocol

This paper describes the implementation of a decentralized consensus law with theoretically provable convergence properties on a multi-agent testbed comprising of quadrotors. It is shown that for small roll and pitch angles and well-tuned control loops, the quadrotor dynamics can be approximated as a pair of double integrators. Several experiments are carried out in an outdoor environment for validation of the consensus law which is based on double integrator dynamics. For any arbitrary initial positions of the quadrotors, the consensus law is able to drive them to an autonomously decided common point, given that the communication graph is connected at each instant of time. The resulting experimental trajectories and the consensus point matches with theoretical predictions. For guaranteeing real-time reliability required for such coordinated motion, a novel synchronized, time-slotted, scalable and fully airborne communication protocol is proposed. The protocol avoids data collisions and ensures real-time, reliable communication between agents. It can also address changing communication graph topologies, temporary link-breaks and additions. Using this underlying protocol, the quadrotors attain consensus for static and dynamic communication graphs. Experiments to observe the effect of communication rate on consensus performance are also conducted.     

Robust Fault Diagnosis for Quadrotor UAVs Using Adaptive Thau Observer

A robust Fault Diagnosis (FD) scheme for a real quadrotor Unmanned Aerial Vehicle (UAV) is proposed in this paper. Firstly, a novel Adaptive Thau observer (ATO) is developed to estimate the quadrotor system states and build a set of offset residuals to indicate actuators’ faults. Based on these residuals, some rules of Fault Diagnosis (FD) are designed to detect and isolate the faults as well as estimate the fault offset parameters. Secondly, a synthetic robust optimization scheme is presented to improve Fault Estimation (FE) accuracies, three key issues include modeling uncertainties, and magnitude order unbalances as well as noises are addressed. Finally, a typical fault of rotors is simulated and injected into one of four rotors of the quadrotor, and experiments for the FD scheme have been carried out. Unlike former research works on the FD schemes for quadrotors, our proposed FD scheme based on the ATO can not only detect and isolate the failed actuators, but also estimate the fault severities. Regardless of roughness of the real flying data, the FD results still have sufficient FE accuracies.     

基于ARM的多传感器四旋翼飞行器控制系统设计

为改变以传统嵌入式处理器的四翼飞行器的控制方式,基于四旋翼飞行器的工作原理和性能特点,提出了一种基于ARM Cortex-M7的嵌入式处理器的飞行控制系统的设计和实现方案.阐述了四旋翼飞行器的物理结构与飞行原理,给出了硬件系统总体方案;在整合各功能模块的基础上,对系统硬件电路进行设计,并进行了模拟仿真运行和实验验证.仿真与实验表明:设计能够保证系统的高稳定性,能满足飞行器起飞、悬停、侧飞等飞行模态的控制要求.     

Distributed finite‐time formation control for multiple quadrotors via local communications

This paper investigates finite‐time formation tracking control problem for multiple quadrotors with external disturbance. The states of the virtual leader are not available to all the followers and the network topology is described by a directed graph. The model of each quadrotor is divided into position subsystem and attitude subsystem. Firstly, novel distributed finite‐time state observers are designed to estimate the relative state errors between followers and the virtual leader. Secondly, the values of these observers are used to design controllers that achieve finite‐time robust coordinated tracking in the position subsystem. Thirdly, the terminal sliding mode disturbance observers and finite‐time attitude tracking controllers are proposed, respectively, in the attitude subsystem to estimate the external disturbance and achieve attitude tracking control. The finite‐time stability analysis of the control algorithms is carried out using the Lyapunov theory and the homogeneous technique. Finally, the efficiency of the proposed algorithm is illustrated by numerical simulations.     

具有执行器故障的四旋翼无人机自适应预定性能控制

针对具有执行器故障的四旋翼无人机,提出一种自适应预定性能控制方案.首先,基于内环姿态控制及外环位置控制的双闭环控制策略,将无人机系统解耦为位置子系统和姿态子系统;其次,设计自适应控制方案,对存在的执行器故障参数进行自适应估计,有效地解决了执行器故障下无人机稳定控制问题;然后,提出一种预定性能控制策略,保证系统的暂稳态性能满足预先给定的性能指标;最后,通过仿真实例验证所提出方法的有效性.