非仿射非线性多智能体系统迭代学习一致跟踪

为了解决非仿射非线性多智能体系统在给定时间区间上一致性完全跟踪问题,基于迭代学习控制方法设计一种分布式一致性跟踪控制算法.首先,由引入的虚拟领导者与所有跟随者组成多智能体系统的通信拓扑,其中虚拟领导者的作用是提供期望轨迹.然后,在只有部分跟随者能够获得领导者信息的条件下,利用每个跟随者及其邻居的跟踪误差构造每个跟随者的迭代学习一致性跟踪控制器.同时采用中值定理将非仿射非线性多智能体系统转化仿射形式,并基于压缩映射方法证明所提算法的收敛性,给出算法的收敛条件.理论分析表明,在智能体的非线性函数未知情况下,利用所提算法可以使非仿射非线性多智能体系统在给定时间区间上随迭代次数增加逐次实现一致性完全跟踪.最后,通过仿真算例进一步验证所提算法的有效性.     

具有通信时延的二阶多智能体系统有限时间一致性跟踪控制

针对具有通信时延的二阶多智能体系统的有限时间一致性控制问题,分别研究了具有固定拓扑和切换拓扑网络结构情形下的二阶多智能体系统的有限时间一致性。为使多智能体系统能在有限时间内可以达到一致,引入一致性控制增益矩阵并设计了相应的基于相对位置和相对速度的时延状态误差有限时间一致性控制算法,利用系统模型转换,泛函微分方程稳定性理论和有限时间Lyapunov稳定性定理得到了使系统在有限时间内达到一致跟踪的最大时延上界值。最后,仿真实验结果验证了所得理论的正确性和有效性。     

基于观测器的线性时变时滞多智能体系统一致性

针对系统状态不可测和具有通信时延的线性多智能体系统,提出一种基于观测器的一致性控制算法.设计观测器用于解决智能体状态不可测的问题,在观测器的基础上,提出一种控制协议来实现带时变时延的线性多智能体系统一致性.利用模型转换的方式将原系统转换为新的模型系统,在此基础上,构造Lyapunov-Krasovskii函数并分析系统稳定性,通过求解线性矩阵不等式获取控制器系数矩阵.最后通过Matlab数值仿真验证所提出方法的有效性.     

含时延约束的多智能体系统二分一致性

针对多智能体系统中信息交互存在通信时延这一约束,在无向符号图拓扑结构下分别研究了含固定时延和时变时延的一阶多智能体系统二分一致性问题。通过设计相应的控制协议,使得该系统收敛到两个模值相同但符号不同的状态。在稳定性分析中,利用广义Nyquist准则的方法,得到含固定时延多智能体系统实现二分一致性的充分条件;对含时变时延系统构造包含三重积分项的Lyapunov函数,利用积分不等式和线性矩阵不等式理论,并结合自由矩阵的方法得到含时变时延多智能体系统实现二分一致性的充分条件。最后,数值仿真验证了所得结论的有效性和正确性。     

具有随机通信时延的二阶多智能体系统的一致性控制

研究了具有随机通信时延的二阶多智能体系统的一致性控制问题.分别讨论了具有固定拓扑结构和变化拓扑结构两种情形下二阶多智能体系统在具有随机通信时延情况下的一致性问题.通过构造Lyapunov函数的方法得到多智能体系统的时延依赖稳定判据,并以线性矩阵不等式(LMI)的形式给出了系统稳定的条件.最后,仿真和实验结果验证了研究所得结论的正确性和有效性.     

具有时延和切换拓扑的高阶离散时间多智能体系统鲁棒保性能一致性

研究存在参数不确定性的高阶离散时间多智能体系统在时延和联合连通切换通信拓扑条件下的鲁棒保性能一致性问题,给出一种线性一致性协议的设计方法.1）引入高阶离散时间不确定多智能体系统的鲁棒保性能一致性问题,定义基于智能体邻居状态误差和控制输入的保性能函数;2）通过构造合适的Lyapunov函数并利用离散时间系统稳定性理论,推导出一个使高阶离散时间不确定多智能体系统在该条件下获得保性能一致性的线性矩阵不等式（Linear matrix inequality,LMI）充分条件,并给出相应的保性能上界;3）以一致性序列的形式给出参数不确定条件下的高阶离散时间多智能体系统的一致性收敛结果;4）数值仿真验证了本文理论的正确性和有效性.     

具有领航者的时延多智能体系统的群集运动

计算机技术、网络技术和通信技术的飞速发展,推动着无人驾驶飞行器的编队控制、传感器网络的分布控制、卫星的姿态控制等多智能体系统的建模与应用的逐步深入,也吸引了越来越多的研究者致力于多智能体系统的动态编队控制的研究.研究了具有不同的通信时延和不同的输入时延的移动多智能体算法的群集运动.假设多智能体系统由n个智能体和1个Leader组成,网络连接拓扑是静态有向连通图,智能体Leader为拓扑图的全局可达节点.应用频率域的广义Nyquist判据分析了具有不同的通信时延和不同的输入时延的移动多智能体算法,应用Greshgorin圆盘定理和曲线的曲率理论研究了具有领航者的多智能体算法的群集运动,得到保证系统一致性的收敛条件.该一致性条件是一个应用节点局部信息的分散式条件,只与输入时延有关,而与通信时延无关.最后,通过计算机仿真验证了本文结论的有效性.     

时延多智能体系统领导跟随一致性研究

为符合实际情形,针对不确定与随机发生非线性的多智能体系统,研究了有时延且网络拓扑切换时系统的领导跟随一致性。传统协议通常保守的假设邻接个体间通信时延与个体和领导者间通信时延大小相同,新协议中上述时延可以大小不同。相比于传统方法,新颖的将复杂网络同步问题研究领域对时延的处理方法引入到多智能体系统一致性问题的研究中,利用一类推广的Halanay不等式,给出系统实现领导跟随一致性需满足的两个与时延无关的充分条件,即时延在相关参数满足定理条件的前提下不影响系统最终实现一致性。相比其他方法得到的含有时延的判定条件,本研究结果保守性更低,实例仿真验证了新协议的可行性。     

非对称输入饱和下的非仿射不确定系统自抗扰反演控制

针对一类具有内部动态和外部扰动未知以及非对称输入饱和约束的非仿射系统,提出一种自抗扰反演控制方法.首先基于自抗扰控制思想,通过直接从非仿射项中提取线性控制项,将非仿射系统转化为仿射非线性形式.在此基础上, 在每一步反演控制器设计中,引入扩张状态观测器对系统总的不确定项进行估计,引入跟踪微分器解决虚拟导数的“计算膨胀”问题.在设计真实控制律时,利用双曲正切函数设计一种辅助补偿系统,用来处理输入饱和引起的控制量偏差.基于Lyapunov稳定性定理证明了闭环系统的所有信号有界且跟踪误差可渐近收敛到原点的任意小邻域内.仿真比较结果验证了所提出方法的有效性,体现了一定的工程应用价值.     

执行器饱和多智能体系统的自适应学习一致性算法

针对一类受到执行器饱和高阶多智能体系统在有限时间区间[0,T]上的精确一致性问题,利用自适应迭代学习控制的方法,设计了具有全饱和差分型自适应更新律的时变增益.通过构造适当的复合能量函数,严格证明了一致性误差向量随着迭代次数趋于无穷而一致趋于零,得到了不依赖于网络通信拓扑矩阵特征值的自适应学习一致性算法.最后,给出一个仿真例子,仿真结果说明了所提算法的有效性.     

Adaptive neural control for multiagent systems with asymmetric time‐varying state constraints and input saturation

This article investigates the leader‐follower consensus problem of a class of non‐strict‐feedback nonlinear multiagent systems with asymmetric time‐varying state constraints (ATVSC) and input saturation, and an adaptive neural control scheme is developed. By introducing the distributed sliding‐mode estimator, each follower can obtain the estimation of leader's trajectory and track it directly. Then, with the help of time‐varying asymmetric barrier Lyapunov function and radial basis function neural networks, the controller is designed based on backstepping technique. Furthermore, the mean‐value theorem and Nussbaum function are utilized to address the problems of input saturation and unknown control direction. Moreover, the number of adaptive laws is equal to that of the followers, which reduces the computational complexity. It is proved that the leader‐follower consensus tracking control is achieved without violating the ATVSC, and all closed‐loop signals are semiglobally uniformly ultimately bounded. Finally, the simulation results are provided to verify the effectiveness of the control scheme.     

多自主水下航行器系统一致性编队跟踪控制

研究了自主水下航行器的编队路径跟踪问题.基于无源性理论与一致性跟踪理论,在仅有部分AUV获取编队速度信息情形下,设计一种分布式控制律,实现了集群AUV的一致性编队跟踪.控制律分为2个部分:一部分基于无源性同步原理,建立了协同误差到跟踪误差的无源性通道;另一部分为一致性协同跟踪控制器,保证每个AUV相对于虚拟领航者的不一致参考信息通过协商达到最终一致状态.文章应用Nested Matrosov定理证明了整个闭环系统的稳定性,仿真结果验证了上述方法的有效性和可行性.     

带有不连续动力学的非线性多智能体系统固定时间一致性EI北大核心CSCD

本文研究了一类带有不连续动力学和有界扰动的非线性多智能体系统领导跟随固定时间一致性问题.首先,在不对称的有向拓扑图下,本文设计了一种辅助信号,该辅助信号用于观测领导者状态,且该辅助信号不在通信信道中传输,可以有效地减少系统计算代价.随后,基于辅助信号,本文设计了一种不连续控制协议,以实现多智能体系统固定时间收敛.然后,利用非光滑分析、Lyapunov稳定性理论及代数图论等证明系统可在任意初始状态下达到固定时间一致.最后,仿真实例进一步验证了理论结果的有效性.     

Chaos control and synchronization via a novel chatter free sliding mode control strategy

In this paper, we propose a novel chatter free sliding mode control (SMC) strategy for chaos control and synchronization to the nonlinear uncertain chaotic systems. A new sort of dynamical sliding mode surface with both integral and differential operators is introduced to divert the discontinuous sign function switch term into the first derivative of the control input; hence a chatter free control input is obtained for the chaotic systems with uncertainties. Based on the Lyapunov stability theory and SMC technique, stability analysis is performed and a theorem serving as designing the chatter free sliding mode control input is also proposed. In the simulation part, first, the results regarding chaos control and synchronization are given to show that the proposed strategy can control the states of the uncertain chaotic systems to desired states with fast speed. In order to show the advantage of eliminating chatter in control input of our method, we give the simulation results performed by traditional SMC and the method proposed recently. Simulation results indicate that this novel chatter free sliding mode control strategy is very effective to chaos control and synchronization.     

Estimation of basins of attraction for controlled systems with input saturation and time-delays

Basins of attraction are instrumental to study the effect of input saturation in control systems, as these sets characterise the initial conditions for which the control strategy induces attraction to the desired state. In this paper, we describe these sets when the open-loop system is exponentially unstable and the system is controlled by actuators with both constant time-delays and saturation. Estimates of the basin of attraction are provided and the allowable time-delay in the control loop is determined with a novel piecewise quadratic Lyapunov–Krasovskii functional that exploits the piecewise affine nature of the system. As this approach leads to sufficient, but not to necessary conditions for attractivity, we present simulations for two examples to show the applicability of the results.     

Multiple UAV Formations for Cooperative Source Seeking and Contour Mapping of a Radiative Signal Field

In this paper, four scenarios are presented for cooperative source seeking and contour mapping of a radiative signal field by multiple UAV formations. A source seeking strategy is adopted with saturation, and then it is modified to achieve contour mapping of the signal field with the moving source situation considered. A formation controller used for consensus problem is simplified and applied in the scenarios to stabilize the multiple UAV formation flight during source detection. The contour mapping strategy and the formation control algorithm are combined to guarantee stable source seeking and contour mapping in both circular flight path and square flight path via multiple UAV formations.     

Group consensus of multi-agent systems in directed networks with noises and time delays

In this paper, group consensus problems in fixed directed networks of dynamic agents are investigated. Group consensus means that the agents in each group share a consistent value while there is no agreement between any two groups. Based on algebraic graph theory, sufficient conditions guaranteeing group consensus under the proposed control protocol in the presence of random noises and communication delays are derived. The analysis uses a stability result of Mao for stochastic differential delay equations, which ensures the consensus can be achieved almost surely and exponentially fast. Numerical examples are provided to demonstrate the availability of the obtained results as well as the effect of time delay/noise intensity.     

On the parameter convergence properties of a combined VS/adaptivecontrol scheme during sliding motion

The effects of the use of a variable structure control component within an adaptive control scheme, previously proposed by the authors (1992, 1995), are investigated in this paper. The discontinuous control action does not allow the explicit identification of the coefficients of the filters, but only the identification of the so-called equivalent control coinciding with the ideal control. By coupling the variable structure control strategy with a continuous parameter adjustment mechanism it is instead possible to obtain an equivalent control which, during the sliding motion, turns out to be equal to a suitably constructed prediction error. As long as the parameter adaptation is driven by both the tracking error (which vanishes in finite time) and the prediction error, then the controller parameters prove to be exponentially convergent to the ideal values, provided that the reference signal is sufficiently persistently exciting     

Adaptive Sliding-Mode Control of an Automotive Electronic Throttle in the Presence of Input Saturation Constraint

In modern vehicles, electronic throttle (ET) has been widely utilized to control the airflow into gasoline engine. To solve the control difficulties with an ET, such as strong nonlinearity, unknown model parameters and input saturation constraints, an adaptive sliding-mode tracking control strategy for an ET is presented. Compared with the existing control strategies for an ET, input saturation constraints and parameter uncertainties are adequately considered in the proposed control strategy. At first, the nonlinear dynamic model for control of an ET is described. According to the dynamical model, the nonlinear adaptive sliding-mode tracking control method is presented, where parameter adaptive laws and auxiliary design system are employed. Parameter adaptive law is given to estimate the unknown parameter with an ET. An auxiliary system is designed, and its state is utilized in the tracking control method to handle the input saturation. Stability proof and analysis of the adaptive sliding-mode control method is performed by using Lyapunov stability theory. Finally, the reliability and feasibility of the proposed control strategy are evaluated by computer simulation. Simulation research shows that the proposed sliding-mode control strategy can provide good control performance for an ET.      

Leader-following fixed-time output feedback consensus for second-order multi-agent systems with input saturation

This paper investigates the leader-following fixed-time output feedback consensus problem for second-order multi-agent systems with input saturation. By combing fixed-time control technique and bi-limit homogeneous systems theory, a class of bounded fixed-time consensus protocols are developed for leader-following multi-agent systems. The protocol design is divided into two parts. First, when all the state information of the followers are measurable, a state feedback consensus protocol is designed to achieve fixed-time consensus. Then, when the velocity information is unmeasurable, an observer-based fixed-time consensus protocol is proposed. With the help of Lyapunov stability theorem and the property of a homogeneous function, it is theoretically shown that the states of all followers can track that of the leader in fixed-time in the presence of input saturation. Finally, numerical simulation is carried out to illustrate the effectiveness of theoretical results.