Research of Risk Identification and Prevention of Underground Pressure Pipelines Damage Caused by External Disturbance

External disturbance is an important cause of underground pressure pipeline damage,which leads to accidents,and it is crucial to study the risk of damage caused by external disturbance and come up with proper prevention and control measures.We reviewed literature on risk identification of underground pressure pipelines damage due to external disturbance was conducted,and a list of risk factors was formed.Based on the list of risk factors,fault tree analysis was carried out on underground pressure pipelines damage caused by external disturbances,and risk prevention and control measures were proposed through the calculation of minimum cut sets,minimum path sets,and structural importance,in hopes of providing reference for the normal operation of underground pressure pipelines.

PD-type iterative learning control for nonlinear time-delay system with external disturbance

The PD-type iterative learning control design of a class of affine nonlinear time-delay systems with external disturbances is considered. Sufficient conditions guaranteeing the convergence of the n-norm of the tracking error are derived. It is shown that the system outputs can be guaranteed to converge to desired trajectories in the absence of external disturbances and output measurement noises. And in the presence of state disturbances and measurement noises, the tracking error will be bounded uniformly. A numerical simulation example is presented to validate the effectiveness of the proposed scheme.

Circular Formation Flight Control for Unmanned Aerial Vehicles With Directed Network and External Disturbance

This paper proposes a new distributed formation flight protocol for unmanned aerial vehicles(UAVs)to perform coordinated circular tracking around a set of circles on a target sphere.Different from the previous results limited in bidirectional networks and disturbance-free motions,this paper handles the circular formation flight control problem with both directed network and spatiotemporal disturbance with the knowledge of its upper bound.Distinguishing from the design of a common Lyapunov fiunction for bidirectional cases,we separately design the control for the circular tracking subsystem and the formation keeping subsystem with the circular tracking error as input.Then the whole control system is regarded as a cascade connection of these two subsystems,which is proved to be stable by input-tostate stability(ISS)theory.For the purpose of encountering the external disturbance,the backstepping technology is introduced to design the control inputs of each UAV pointing to North and Down along the special sphere(say,the circular tracking control algorithm)with the help of the switching function.Meanwhile,the distributed linear consensus protocol integrated with anther switching anti-interference item is developed to construct the control input of each UAV pointing to east along the special sphere(say,the formation keeping control law)for formation keeping.The validity of the proposed control law is proved both in the rigorous theory and through numerical simulations.

Terminal sliding mode control for coordinated motion of a space rigid manipulator with external disturbance

The control problem of coordinated motion of a free-floating space rigid manipulator with external disturbance is discussed. By combining linear momentum conversion and the Lagrangian approach, the full-control dynamic equation and the Jacobian relation of a free-floating space rigid manipulator are established and then inverted to the state equation for control design. Based on the terminal sliding mode control （SMC） technique, a mathematical expression of the terminal sliding surface is proposed. The terminal SMC scheme is then developed for coordinated motion between the base＇s attitude and the end-effector of the free-floating space manipulator with external disturbance. This proposed control scheme not only guarantees the existence of the sliding phase of the closed-loop system, but also ensures that the output tracking error converges to zero in finite time. In addition, because the initial system state is always at the terminal sliding surface, the control scheme can eliminate reaching phase of the SMC and guarantee global robustness and stability of the closed-loop system. A planar free-floating space rigid manipulator is simulated to verify the feasibility of the proposed control scheme.

Distributed Secondary Control of AC Microgrids With External Disturbances and Directed Communication Topologies:A Full-Order Sliding-Mode Approach

This paper addresses the problem of distributed secondary control for islanded AC microgrids with external disturbances.By using a full-order sliding-mode(FOSM)approach,voltage regulation and frequency restoration are achieved in finite time.For voltage regulation,a distributed observer is proposed for each distributed generator(DG)to estimate a reference voltage level.Different from some conventional observers,the reference voltage level in this paper is accurately estimated under directed communication topologies.Based on the observer,a new nonlinear controller is designed in a backstepping manner such that an FOSM surface is reached in finite time.On the surface,the voltages of DGs are regulated to the reference level in finite time.For frequency restoration,a distributed controller is further proposed such that a constructed FOSM surface is reached in finite time,on which the frequencies of DGs are restored to a reference level in finite time under directed communication topologies.Finally,case studies on a modified IEEE 37-bus test system are conducted to demonstrate the effectiveness,the robustness against load changes,and the plug-and-play capability of the proposed controllers.

Pinning Synchronization Between Two General Fractional Complex Dynamical Networks With External Disturbances

In this paper, the pinning synchronization between two fractional complex dynamical networks with nonlinear coupling, time delays and external disturbances is investigated. A Lyapunov-like theorem for the fractional system with time delays is obtained. A class of novel controllers is designed for the pinning synchronization of fractional complex networks with disturbances. By using this technique, fractional calculus theory and linear matrix inequalities, all nodes of the fractional complex networks reach complete synchronization. In the above framework, the coupling-configuration matrix and the innercoupling matrix are not necessarily symmetric. All involved numerical simulations verify the effectiveness of the proposed scheme. © 2017 Chinese Association of Automation.

Disturbance observer based time-varying sliding mode control for uncertain mechanical system

It is now well known that the time-varying sliding mode control （TVSMC） is characterized by its global robustness against matched model uncertainties and disturbances. The accurate tracking problem of the mechanical system in the presence of the parametric uncertainty and external disturbance is addressed in the TVSMC framework. Firstly, an exponential TVSMC algorithm is designed and the main features are analyzed. Especially, the control parameter is obtained by solving an optimal problem. Subsequently, the global chattering problem in TVSMC is considered. To reduce the static error resulting from the continuous TVSMC algorithm, a disturbance observer based time-varying sliding mode control （DOTVSMC） algorithm is presented. The detailed design principle and the stability of the closed-loop system under the composite controller are provided. Simulation results verify the effectiveness of the proposed algorithm.

A novel stabilization approach for small signal disturbance of power system with time-varying delay

Small signal instability may cause severe accidents for power system if it can not be dear correctly and timely. How to maintain power system stable under small signal disturbance is a big challenge for power system operators and dispatchers. Time delay existing in signal transmission process makes the problem more complex. Conventional eigenvalue analysis method neglects time delay influence and can not precisely describe power system dynamic behaviors. In this work, a modified small signal stability model considering time varying delay influence was constructed and a new time delay controller was proposed to stabilize power system under disturbance. By Lyapunov-Krasovskii function, the control law in the form of nonlinear matrix inequality （NLMI） was derived. Considering synthesis method limitation for time delay controller at present, both parameter adjustment method by using linear matrix inequality （LMI） solver and iteration searching method by solving nonlinear minimization problem were suggested to design the controller. Simulation tests were carried out on synchronous-machine infinite-bus power system. Satisfactory test results verify the correctness of the proposed model and the feasibility of the stabilization approach.

Feedforward and feedback optimal control for linear time-varying systems with persistent disturbances

The optimal control problem for linear time-varying systems affected by external persistent disturbances with known dynamic characteristics but unknown initial conditions is consider and a design procedure of a feedforward and feedbaek optimal controller is presented. The condition of existence and uniqueness of the control law is given. The disturbanee observer is proposed to make the feedforward control law realizable physically. Simulation results demonstrate that the feedforward and feedbaek optimal control law is more effective and robust than the elassical state feedbaek control law with respect to external disturbanees.

Feedforward and feedback optimal control for linear time-varying systems with persistent disturbances

The optimal control problem was studied for linear time-varying systems,which was affected by external persistent disturbances with known dynamic characteristics but unknown initial conditions. To damp the effect of disturbances in an optimal fashion,we obtained a new feedforward and feedback optimal control law and gave the control algorithm by solving a Riccati differential equation and a matrix differential equation. Simulation results showed that the achieved optimal control law was realizable,efficient and robust to reject the external disturbances.

Precision motion control for electro-hydraulic axis systems under unknown time-variant parameters and disturbances

This article focuses on asymptotic precision motion control for electro-hydraulic axis systems under unknown time-variant parameters,mismatched and matched disturbances.Different from the traditional adaptive results that are applied to dispose of unknown constant parameters only,the unique feature is that an adaptive-gain nonlinear term is introduced into the control design to handle unknown time-variant parameters.Concurrently both mismatched and matched disturbances existing in electro-hydraulic axis systems can also be addressed in this way.With skillful integration of the backstepping technique and the adaptive control,a synthesized controller framework is successfully developed for electro-hydraulic axis systems,in which the coupled interaction between parameter estimation and disturbance estimation is avoided.Accordingly,this designed controller has the capacity of low-computation costs and simpler parameter tuning when compared to the other ones that integrate the adaptive control and observer/estimator-based technique to dividually handle parameter uncertainties and disturbances.Also,a nonlinear filter is designed to eliminate the“explosion of complexity”issue existing in the classical back-stepping technique.The stability analysis uncovers that all the closed-loop signals are bounded and the asymptotic tracking performance is also assured.Finally,contrastive experiment results validate the superiority of the developed method as well.

Consensus Control of Leader-Following Multi-Agent Systems in Directed Topology With Heterogeneous Disturbances

This paper investigates the consensus problem for linear multi-agent systems with the heterogeneous disturbances generated by the Brown motion.Its main contribution is that a control scheme is designed to achieve the dynamic consensus for the multi-agent systems in directed topology interfered by stochastic noise.In traditional ways,the coupling weights depending on the communication structure are static.A new distributed controller is designed based on Riccati inequalities,while updating the coupling weights associated with the gain matrix by state errors between adjacent agents.By introducing time-varying coupling weights into this novel control law,the state errors between leader and followers asymptotically converge to the minimum value utilizing the local interaction.Through the Lyapunov directed method and It?formula,the stability of the closed-loop system with the proposed control law is analyzed.Two simulation results conducted by the new and traditional schemes are presented to demonstrate the effectiveness and advantage of the developed control method.

Disturbance observer based position tracking of electro-hydraulic actuator

A nonlinear controller based on an extended second-order disturbance observer is presented to track desired position for an electro-hydraulic single-rod actuator in the presence of both external disturbances and parameter uncertainties. The proposed extended second-order disturbance observer deals with not only the external perturbations, but also parameter uncertainties which are commonly regarded as lumped disturbances in previous researches. Besides, the outer position tracking loop is designed with cylinder load pressure as output; and the inner pressure control loop provides the hydraulic actuator the characteristic of a force generator. The stability of the closed-loop system is provided based on Lyapunov theory. The performance of the controller is verified through simulations and experiments. The results demonstrate that the proposed nonlinear position tracking controller, together with the extended second-order disturbance observer, gives an excellent tracking performance in the presence of parameter uncertainties and external disturbance.

Feedback Chaotic Synchronization with Disturbances

Based on Lyapunov stability theorem, a method is proposed for feedback synchronization with parameters perturbation and external disturbances. It is proved theoretically that if the perturbation and disturbances are bounded, the synchronization error can be ensured to approach to and stay within the pre-specified bound which can be arbitrarily small. Some typical chaotic systems with different types of nonlinearity, such as Lorenz system and the original Chua’s circuit, are used for detailed description. The simulation results show the feasibility of the method.

动态事件触发脉冲机制下多智能体系统的拟一致性

考虑到多智能体系统在复杂环境中受到外部干扰和控制器受到恶意攻击等问题,本文旨在研究一类受扰非线性多智能体系统在事件触发机制和脉冲控制下的领导跟随拟一致性。不同于现有文献中需要事先指定最小事件触发间隔,本文所设计的动态事件触发机制通过其参数的选择加以保证,从而避免了芝诺行为的发生。基于此机制,进一步给出了系统实现拟一致性的一些充分条件以及相应误差上界的估量值。最后,通过数值仿真例子验证了结果的有效性。

基于改进模糊滑模控制的列车速度跟踪研究

列车运行过程具有强耦合、非线性等特征,且往往存在较大且不可观测的外界干扰,这些特性加大了列车运行控制的难度,针对列车运行速度跟踪控制问题,提出一种新的模糊滑模控制器设计方法。首先基于模糊滑模控制,引入全局快速终端滑模控制,使系统在有限时间内达到稳态;然后构造以李亚普洛夫函数导数的绝对值为补偿的自适应干扰估计项,对外界干扰进行准确估计,进而提出一种双层递阶指数趋近全局快速终端模糊滑模控制器,并且引入指数趋近率来调节滑模面的动态品质,该控制器能快速收敛到稳定状态,且有效地消除了控制器的抖振情况;最后通过仿真算例验证了所提方法的有效性,且提高了列车运行控制系统性能。

基于扰动观测器的双容液位系统RBF神经网络滑模控制

针对双容液位系统存在的外部扰动、模型参数不确定等问题,设计了一种基于非线性扰动观测器(nonlinear disturbance observer,NDOB)的径向基函数神经网络滑模控制(radial basis function neural network sliding mode control,RNNSMC)方法。建立双容液位系统数学模型,采用积分型滑模面来提高系统的鲁棒性,在常规积分滑模控制的基础上,通过RBF神经网络(RBF neural network,RNN)对系统的非线性函数进行逼近,并设计非线性扰动观测器估计外部扰动,选用Lyapunov稳定性判据证明了控制策略的闭环稳定性。仿真结果表明,所提控制策略与积分滑模控制(integral sliding mode control,ISMC)方法相比,不需要精确的数学模型,且控制精度更高,抗干扰能力更强。

基于延迟补偿的永磁同步电机并行自抗扰控制

为了解决永磁同步电机在多工况下转速易受到内外扰动的影响,提出一种基于延迟补偿的并行线性自抗扰控制策略。针对永磁同步电机可能受到信号处理、逆变器响应等因素从而引入的外部时滞效应的问题,引入Smith预估器与自抗扰控制相结合,使控制系统更加精确、快速地响应内部参数变化和外部扰动。同时,针对线性自抗扰控制器(LADRC)在有限带宽内其抗扰性能较差的问题,设计了并行线性自抗扰控制器,在保持其带宽不变与参数易于整定的同时,有效提高其抗扰动能力。最后,对自抗扰控制器的稳定性进行了分析,并在此基础上进行了参数设计与扰动性能分析。仿真与实验结果表明,所提算法相比LADRC在电机受到速度阶跃、负载扰动与内部参数变化时,在调整时间上分别提升了52.5%、49.5%与42.4%,从而验证了该控制策略能有效增强永磁同步电机在多工况下抗内外扰动与速度跟踪能力。

含不确定参数的智能网联汽车协同编队控制

为应对智能网联汽车协同编队控制中因自身条件以及外部攻击干扰引起的参数不确定变化问题,在智能网联汽车编队运行环境下提出了一种基于观测器的一致性控制协议设计方法。首先,通过设计观测器实现对系统状态、可测噪声和外部扰动等的有效估计。其次,设计适用的分布式一致性控制协议,利用Lyapunov泛函得到系统稳定的充分条件。再次,将观测器的增益矩阵转化为线性矩阵不等式的问题进行求解,利用线性矩阵不等式方法,获得观测器增益矩阵的具体取值,实现对系统状态和参数的准确估计。最后,利用Matlab对系统进行仿真,给定智能网联汽车编队系统各项具体参数,模拟系统存在外部干扰的情况以及参数中含有不确定的情况。仿真表明:在一致性控制后系统内部输入经过15个时间步后得到收敛,对于系统状态和外部干扰,观测器在含有不确定参数的干扰下分别经过17个和20个时间步之后能够进行有效的估计,从理论和仿真2个方面验证了所设计方法的正确性与可行性。