基于一致性算法的卫星编队姿轨耦合的协同控制

针对卫星编队一主多从结构的相对轨迹、姿态的协同控制问题,提出了一种基于Lyapunov方法的编队飞行协同控制策略。该控制策略将分布式控制思想引入卫星编队飞行的相对轨迹、姿态的动力学系统中,使各从星保持编队构型的同时沿期望轨迹相对主星绕飞。从理论上证明了系统的渐近稳定以及对外部干扰的抑制,并基于一致性算法理论定量地分析了通信拓扑结构为有向图情况下控制器参数的选择范围。此外,利用星星间的相对位置信息确定各从星的期望姿态和角速度,以确保对卫星编队进行姿态协同控制,达到跟踪同步的目的。最后将提出的算法应用于卫星三角形编队飞行的协同控制,仿真结果表明该方法的可行性与有效性,具有潜在的应用前景。     

Finite Time Consensus Problem for Multiple Non-Holonomic Agents with Communication Delay

In this paper, finite time consensus problem is discussed for multiple non-holonomic mobile agents with constant communication delay. The objective is to design non-smooth distributed control laws such that multiple non-holonomic mobile agents can be all in agreement within any given finite time larger than communication delay. The authors propose a novel switching control strategy with the help of Lyapunov-based method and graph theory.     

Data-Driven Leader-Follower Output Synchronization for Networked Non-Linear Multi-Agent Systems with Switching Topology and Time-Varying Delays

This paper studies the output synchronization problem for a class of networked non-linear multi-agent systems with switching topology and time-varying delays. To synchronize the outputs, a leader is introduced whose connectivity to the followers varies with time, and a novel data-driven consensus protocol based on model free adaptive control is proposed, where the reference input of each follower is designed to be the time-varying average of the neighboring agents’ outputs. Both the case when the leader is with a prescribed reference input and the case otherwise are considered. The proposed protocol allows for time-varying delays, switching topology, and does not use the agent structure or the dynamics information implicitly or explicitly. Sufficient conditions are derived to guarantee the closed-loop stability, and conditions for consensus convergence are obtained, where only a joint spanning tree is required. Numerical simulations and practical experiments are conducted to demonstrate the effectiveness of the proposed protocol.     

Observer-based event-triggered tracking control of leader-follower systems with time delay

This paper studies the tracking control of general linear multi-agent systems with or without time delays. The observer-based event-triggered control schemes will be considered. For the conventional distributed tracking protocol, the authors will not update the relative state in continuous time, i.e., the relative state will be updated by some events which happened in discrete time. A completely decentralized event-trigger will be designed for leader-follower systems. It is shown that all followers can track the leader asymptotically by the proposed protocol, if the feedback gain matrices are designed appropriately. Numerical simulations are also provided and the results show highly consistent with the theoretical results.     

Adaptive Numerical Approach for Optimal Control of a Single Train

This paper considers the optimal control problem of a single train, which is formulated as an optimal control problem of nonlinear systems with switching controller. The switching sequence and the switching time are decision variables to be chosen optimally. Generally speaking, it is very difficult to solve this problem analytically due to its nonlinear nature, the complexity of the controller,and the existence of system state and control input constraints. To obtain the numerical solution, by introducing binary functions for every value of the control input, relaxing the binary functions, and imposing a penalty function on the relaxation, the problem is transformed into a parameter optimization problem, which can be efficiently solved by using any gradient-based numerical approach. Then, the authors propose an adaptive numerical approach to solve this problem. Convergence results indicate that any optimal solution of the parameter optimization problem is also an optimal solution of the original problem. Finally, an optimal control problem of a single train illustrates that the adaptive numerical approach proposed by us is less time-consuming and obtains a better cost function value than the existing approaches.     

Consensus of Single Integrator Multi-Agent Systems with Unbounded Transmission Delays

This paper investigates the consensus problem of single integrator multi-agent systems with unbounded time-varying transmission delays and fixed directed topology. A distributed controller is proposed taking into consideration the unbounded transmission delays. It is shown that the consensus problem can be solved via the proposed controller under the spanning tree assumption and the nocycle assumption. The authors characterize the no-cycle assumption and prove the consensus of the concerned multi-agent system with an induction procedure. Two simulation examples are provided,one to illustrate the effectiveness of our result and the other to show the necessity of the no-cycle assumption.     

近空间飞行器鲁棒自适应Backstepping控制

针对变体近空间飞行器(near space vehiele, NSV)大包络、多模态的特性,研究其姿态的鲁棒自适应跟踪控制问题。首先,提出标称变体NSV切换非线性系统的单一且光滑主控制器设计方法,以解决因飞行模态切换引起的主控制舵面跳变。其次,针对切换瞬间复合干扰存在不连续的问题,给出一组同步切换的改进干扰观测器设计方法。将改进干扰观测器的输出与光滑的主控制律相结合组成不确定变体NSV切换非线性系统的复合控制器。采用平均驻留时间分析法证明所提出的控制方法可以保证闭环不确定变体NSV切换非线性系统的稳定性。最后,仿真结果验证了所提方法的有效性。     

空天飞行器再入姿态模糊切换多模型控制

针对多模型切换控制在切换边界处的不平滑性,提出了一种模糊切换多模型控制。将其输入空间划分为若干个模糊区域以使区域边界模糊化,在各区域内设计局部T-S模型和控制器。根据所选定的变量将相应的区域控制器切换为全局控制器,由于控制器切换是在模糊了的区域边界处进行的,故保证了切换过程中系统状态轨迹的平滑性。利用该控制方案为空天飞行器设计了再入姿态飞行控制系统,高超声速飞行条件下的仿真实验证明了方法的有效性。     

基于聚类方法和神经网络的非线性系统多模型自适应控制

针对具有参数跳变的非线性系统,联合聚类算法和神经网络提出新的多模型自适应控制方法。首先对系统的输入输出数据进行模糊聚类,然后基于递推最小二乘法建立多个固定模型。为提高系统的暂态性能,同时建立两个自适应模型,并在此基础上设计鲁棒自适应控制器。此外,为了补偿系统的非线性部分,建立非线性预测模型,并设计非线性神经网络自适应控制器。所提方法可使控制切换系统具有稳定性保证。最后,通过性能指标对控制器进行平滑切换。仿真结果表明,所提方法能够保证系统具有良好的控制性能。     

水下超高速航行体双模态控制研究

水下航行体在高速运动时,其全部或大部分表面被空泡包裹.由于水动力和周围环境扰动使航行体尾部与空泡壁相互作用产生滑行力,滑行力的存在使系统具有较强的非线性并导致不稳定的航行状态.针对航行体纵向运动数学模型可以描述为无滑行力的线性模型和存在滑行力的非线性模型,设计了基于状态的切换控制策略并设计了双模态控制器,对于线性模型采用状态反馈控制,对于非线性模型采用基于微分几何的反馈线性化方法.仿真结果表明,基于状态切换的双模态控制器减小了滑行力,对于初始状态扰动具有鲁棒性.     

Distributed Nonsmooth Convex Optimization over Markovian Switching Random Networks with Two Step-Sizes

This paper investigates the distributed convex optimization problem over a multi-agent system with Markovian switching communication networks. The objective function is the sum of each agent's local nonsmooth objective function, which cannot be known by other agents. The communication network is assumed to switch over a set of weight-balanced directed graphs with a Markovian property. The authors propose a consensus sub-gradient algorithm with two time-scale step-sizes to handle the Markovian switching topologies and the absence of global gradient information. With proper selection of step-sizes, the authors prove the almost sure convergence of all agents' local estimates to the same optimal solution when the union graph of the Markovian network' states is strongly connected and the Markovian chain is irreducible. The convergence rate analysis is also given for specific cases.Simulations are given to demonstrate the results.     

Input-to-State Stability of Switched Nonlinear Delay Systems Based on a Novel Lyapunov-Krasovskii Functional Method

In this paper, the input-to-state stability (ISS) analysis is addressed for switched nonlinear delay systems. By introducing a novel Lyapunov-Krasovskii functional with indefinite derivative and the merging switching signal techniques, some new criteria are established for switched nonlinear delay systems under asynchronous switching, which extends the existing results to the nonlinear systems with switching rules and delays. The ISS problem is also considered under synchronous switching for switched nonlinear systems by employing the similar techniques. Finally, a nonlinear delay model is provided to show the effectiveness of the proposed results.     

Asynchronous Dissipative Control and Robust Exponential Mean Square Stabilization for Uncertain Fuzzy Neutral Markov Jump Systems

This paper researches the strict dissipative control problem for uncertain fuzzy neutral Markov jump systems by Takagi-Sugeno fuzzy rules. The asynchronous phenomenon is considered between the uncertain fuzzy neutral Markov jump systems modes and asynchronous fuzzy P-D feedback controller modes, which is described by a hidden Markov model. Via using linear matrix inequalities, the desired asynchronous fuzzy P-D feedback controller is obtained, which can ensure that the closed-loop uncertain fuzzy neutral Markov jump systems satisfies robustly exponential mean square stabilization with strict dissipativity. A numerical example and a single-link robot arm are utilized to demonstrate the effectiveness of the method.

     

不确定时滞系统的二次稳定无记忆变结构控制

根据变结构控制 ( VSC)方法及 Lyapunov稳定性理论研究一类不确定性时滞系统的无记忆变结构控制问题 ,所得的变结构控制器保证了切换函数的二次稳定性 ,并避免控制信息号颤振 .此外 ,还推出了一种具有不确定性范数上界自适应估计器的自适应变结构控制器 .仿真结果验证了所得结果的有效性和合理性.     

Group consensus for multiple networked Euler-Lagrange systems with parametric uncertainties

In this paper,a group consensus problem is investigated for multiple networked agents with parametric uncertainties where all the agents are governed by the Euler-Lagrange system with uncertain parameters.In the group consensus problem,the agents asymptotically reach several different states rather than one consistent state.A novel group consensus protocol and a time-varying estimator of the uncertain parameters are proposed for each agent in order to solve the couple-group consensus problem.It is shown that the group consensus is reachable even when the system contains the uncertain parameters.Furthermore,the multi-group consensus is discussed as an extension of the couple-group consensus,and then the group consensus with switching topology is considered.Simulation results are finally provided to validate the effectiveness of the theoretical analysis.     

Optimal Switching Integrity Attacks on Sensors in Industrial Control Systems

In this article, an optimal switching integrity attack problem is investigated to study the response of feedback control systems under attack. The authors model the malicious attacks on sensors as additive norm bounded signals. The authors consider an attacker who is only capable of launching attacks to limited number of sensors once a time and changing the combinations of attacked sensors all over the time. The objective of this paper is to find the optimal switching sequence of these combinations and the optimal attack input. The authors solve this problem by transforming it into a traditional optimal control problem with new control variables vary continuously in the range [0, 1]. The optimal solutions of the new control variables are of bang-bang-type. Therefore, an algebraic switching condition and an optimal attack input can be obtained. Finally, numerical results are provided to illustrate the effectiveness of the methods.     

非齐次马尔可夫LPV系统的H∞异步控制

针对存在外界干扰的情况,对一类离散时间非齐次马尔可夫线性变参数(linear parameter-varying, LPV)系统的H_∞异步控制问题进行了研究。由于实际非齐次马尔可夫系统的系统模态难以直接获得,考虑了控制器模态和系统模态不一致的异步问题,并用一个非齐次隐马尔可夫模型建模。非齐次马尔可夫系统和非齐次隐马尔可夫链的时变特性分别由分段齐次状态转移概率矩阵和分段齐次条件概率矩阵描述,且受同一个高层齐次马尔可夫链支配。针对上述问题,完成了对闭环非齐次马尔可夫LPV系统的稳定性分析、H_∞性能分析和H_∞异步控制器设计,使系统在受到外界干扰和控制器模态与系统模态存在异步现象的情况下满足给定的H_∞性能指标。最后通过对直流电机的仿真实验验证了利用非齐次信息得到理论的有效性和优越性。     

含非线性输入的非线性系统自适应模糊控制

讨论一类含非线性输入的非线性系统的自适应模糊控制问题。首先运用隐函数存在定理证明系统的理想控制器的存在性,利用I型模糊逻辑系统对该理想控制器进行在线逼近,提出了一种具有监督器的自适应模糊滑模控制器设计的新方案。该方案通过直接自适应模糊控制器与监督控制器的适当切换,保证了闭环系统的稳定性,由此确定出建模的有界区域,而且通过引入最优逼近误差的自适应补偿项,保证跟踪误差收敛到零。仿真结果表明了该方法的有效性。     

基于SVPWM的直接转矩控制新方案

针对传统的直接转矩控制(DTC)转矩脉动大、开关频率不恒定等问题,提出了一种基于空间电压矢量脉宽调制(SVPWM)技术的直接转矩控制系统新方案.该系统采用经遗传算法优化后的模糊控制器代替常规的磁链和转矩控制器,以获得任意相位的空间电压矢量,然后利用SVPWM技术来合成该矢量.仿真结果表明该方案能有效减小磁链和转矩脉动,改善系统的性能.     

Consensus control design for multi-agent systems using relative output feedback

This paper studies the consensus problem of multi-agent systems in which all agents are modeled by a general linear system. The authors consider the case where only the relative output feedback between the neighboring agents can be measured. To solve the consensus problem, the authors first construct a static relative output feedback control under some mild constraints on the system model. Then the authors use an observer based approach to design a dynamic relative output feedback control. If the adjacent graph of the system is undirected and connected or directed with a spanning tree, with the proposed control laws, the consensus can be achieved. The authors note that with the observer based approach, some information exchange between the agents is needed unless the associated adjacent graph is completely connected.