Distributed learning and cooperative control for multi-agent systems

This paper presents an algorithm and analysis of distributed learning and cooperative control for a multi-agent system so that a global goal of the overall system can be achieved by locally acting agents. We consider a resource-constrained multi-agent system, in which each agent has limited capabilities in terms of sensing, computation, and communication. The proposed algorithm is executed by each agent independently to estimate an unknown field of interest from noisy measurements and to coordinate multiple agents in a distributed manner to discover peaks of the unknown field. Each mobile agent maintains its own local estimate of the field and updates the estimate using collective measurements from itself and nearby agents. Each agent then moves towards peaks of the field using the gradient of its estimated field while avoiding collision and maintaining communication connectivity. The proposed algorithm is based on a recursive spatial estimation of an unknown field. We show that the closed-loop dynamics of the proposed multi-agent system can be transformed into a form of a stochastic approximation algorithm and prove its convergence using Ljung’s ordinary differential equation (ODE) approach. We also present extensive simulation results supporting our theoretical results.     

Observer design for wired linear networked control systems using matrix inequalities

We design an observer-protocol pair to asymptotically reconstruct the states of a linear time-invariant (LTI) plant under communication constraints induced by the network. We parameterize a class of observers and protocols, and for a given network transmission interval, we derive sufficient conditions in terms of matrix inequalities for the existence of an observer-protocol pair in the considered class that asymptotically reconstructs the plant states.     

Architectures and coder design for networked control systems

In networked control systems (NCSs) achievable performance is limited by the communication links employed to transmit signals in the loop. In the present work, we characterise LTI coding systems which optimise performance for various NCS architectures. We study NCSs where the communication link is situated between plant output and controller, and NCSs where the communication link is located between controller and actuator. Furthermore, we present a novel NCS architecture, which is based upon the Youla parameterisation. We show that, which of these architectures gives best performance depends, inter alia, upon characteristics of a related non-networked design, plant disturbances and reference signal. A key aspect of our work, resides in the utilisation of fixed signal-to-noise ratio channel models which give rise to parsimonious designs, where channel utilisation is kept low. The results are verified with simulations utilising bit-rate limited channels.     

Fault tolerant cooperative control for a class of nonlinear multi-agent systems

This paper studies the target aggregation problem for a class of nonlinear multi-agent systems with the time varying interconnection topology. The general neighboring rule-based linear cooperative protocol is developed and a sufficient aggregation condition is derived. Moreover, it is shown that in the presence of agent faults, the target point is still reached by adjusting some weights of the cooperative protocol without changing the structure of the topology. An unmanned aerial vehicle team example illustrates the efficiency of the proposed approach.     

New approach to stochastic stability and controller design for networked control systems

This paper addresses the random time-delays and packet losses issues of networked control systems （NCS） within the framework of jump linear systems with mode-dependent time-delays. A new delay-dependent condition on the stochastic stability is proposed by a new stochastic Lyapunov-Krasovskii functional. The condition is formulated as a set of coupled linear matrix inequalities （LMIs）. As an example to verify the proposed method, an inverted-pendulum system with network is considered. The simulation results demonstrate the effectiveness of the method.     

Exponential stabilization of networked control systems and design of switching controller

1 Introduction Networked control systems (NCS) are feedback control systems whose feedback paths are implemented by a real- time network. This type of systems has advantages of more ?exibility with respect to traditional control systems. It also allows for reduced wiring, as well as a lower installation cost. Examples of such systems can be seen in remote sur- vey [1], telerobotics [2], unmanned aerial vehicles [3] and remote control laboratory [4,5]. Most of the times, sensors will transmit…     

Quadratic stabilization of linear networked control systems via simultaneous protocol and controller design

We derive conditions for quadratic stabilizability of linear networked control systems by dynamic output feedback and communication protocols. These conditions are used to develop a simultaneous design of controllers and protocols in terms of matrix inequalities. The obtained protocols do not require knowledge of controller and plant states but only of the discrepancies between current and the most recently transmitted values of nodes’ signals, and are implementable on controller area networks. We demonstrate on a batch reactor example that our design guarantees quadratic stability with a significantly smaller network throughput than previously available designs.     

针对时间距离约束的网络化控制系统带宽调度策略

网络化控制系统是一种具有时间距离约束的硬实时系统.根据该特点,在深入分析网络化控制系统时间距离约束关系的基础上,提出一种针对时间距离约束的网络化控制系统带宽调度策略.该策略能够更有效地与网络化控制系统的控制算法相配合,同时兼顾控制系统控制性能和网络服务质量,优化系统总体性能.最后通过仿真实例说明了该策略的有效性.     

Output feedback strict passivity of discrete-time nonlinear systems and adaptive control system design with a PFC

In this paper, a passivity-based adaptive output feedback control for discrete-time nonlinear systems is considered. Output Feedback Strictly Passive (OFSP) conditions in order to design a stable adaptive output control system will be established. Further, a design scheme of a parallel feedforward compensator (PFC), which is introduced in order to realize an OFSP controlled system, will be provided and an adaptive output feedback control system design scheme with a PFC will be proposed.     

The scenario approach for systems and control design

The ‘scenario approach’ is an innovative technology that has been introduced to solve convex optimization problems with an infinite number of constraints, a class of problems which often occurs when dealing with uncertainty. This technology relies on random sampling of constraints, and provides a powerful means for solving a variety of design problems in systems and control. The objective of this paper is to illustrate the scenario approach at a tutorial level, focusing mainly on algorithmic aspects. Its versatility and virtues will be pointed out through a number of examples in model reduction, robust and optimal control.     

Separation of estimation and control for decentralized stochastic control systems

A sufficient condition is given for a separation of estimation and control in decentralized discrete-time stochastic control systems. It is shown that the one-step delay sharing system is a special case satisfying this condition. A counterexample is given, however, to the conjecture that the separation will hold for the more-than-one-step delay sharing systems.     

A modelling framework for complementary design of production planning and control systems

In a business era characterized by a dazzling rate of change, the improvement of production planning and control begins to be a main objective for manufacturing industries. This paper postulates four main statements to be considered for the design of production planning and control systems (PPC-systems) comprising human and technical sub-systems. The first is that production models required for the design of PPC-systems (i.e. design models) cannot be identical to production models required for planning and control of production systems (i.e. regulatory models). The design of PPC-systems must primarily focus on the quality of interaction between the regulatory models. This insight supports the second statement, which postulates that the design of PPC-systems requires a complementary design approach. Complementary design means to take explicitly into account that human and technical sub-systems- based on the differences in strengths and weaknesses of both- can achieve through their interaction a new quality, possible neither to human nor technical sub-systems alone. The third statement is that a complementary design of PPC-systems will only be possible if a fundamental change of mind from a static to a dynamic as well as from a technical to a socio-technical perception (i.e. a complete perception) of production systems takes place. Without a complete perception of production systems, designed PPC-systems will not be sufficiently reliable, maintainable and flexible, will be difficult to comprehend, and their elements will not be re-usable for further applications. The fourth statement is that the integral support of the design process requires a dual modelling framework comprising a meta- and an object-model. Considering these fundamental insights that were confirmed by a practical case study, a dual modelling framework for the design of PPC-systems which incorporates criteria for complementary design is outlined.     

无线网络控制系统研究现状及方向

从基于无线传感器网络理论的无线网络控制系统的工业应用、控制方法设计、调度策略和通信协议的设计以及控制与调度协同设计等方面阐述了目前无线网络控制系统的主要研究内容和研究现状,并讨论了今后无线网络控制系统的研究方向。     

Computer-aided design method for the components made of heterogeneous materials

With rapid developments of high-tech in various fields, there appear more critical requirements for special functions of components/products, which can be satisfied only by using heterogeneous materials: composite materials, functionally graded materials, or heterogeneous materials with a periodic microstructure. However, currently there exists no systematic and effective method for designing components made of these heterogeneous materials. This paper develops such a computer-aided design method, under the guide of Axiomatic Design, which can apply the functions of current CAD/CAE software. With the design method, all the information about both configuration and materials of a heterogeneous component, needed for creating its CAD model, can be obtained.     

Asymptotic stability and disturbance attenuation properties for a class of networked control systems

In this paper, stability and disturbance attenuation issues for a class of Networked Control Systems (NCSs) under uncertain access delay and packet dropout effects are considered. Our aim is to find conditions on the delay and packet dropout rate, under which the system stability and H∞ disturbance attenuation properties are preserved to a desired level. The basic idea in this paper is to formulate such Networked Control System as a discrete-time switched system. Then the NCSs’ stability and performance problems can be reduced to the corresponding problems for switched systems, which have been studied for decades and for which a number of results are available in the literature. The techniques in this paper are based on recent progress in the discrete-time switched systems and piecewise Lyapunov functions.     

Group consensus control for heterogeneous multi-agent systems with fixed and switching topologies

In this paper, the group consensus problems of heterogeneous multi-agent systems with fixed and switching topologies are investigated. First, a class of distributed group consensus protocol is proposed for achieving the group consensus of heterogeneous multi-agent systems by using the neighbours’ information. Then, some corresponding sufficient conditions are obtained to guarantee the achievement of group consensus. Rigorous proofs are given by using graph theory, matrix theory and Lyapunov theory. Finally, numerical simulations are also given to verify the theoretical analysis.     

一类饱和不确定非线性系统静态抗饱和控制设计

研究一类执行器幅值与速率饱和的不确定非线性系统静态抗饱和控制问题.采用线性微分包含的方法处理系统模型中的非线性项.给出了抗饱和补偿器设计方法,该方法能同时保证闭环鲁棒稳定及鲁棒性能.给出了此类非线性系统代数环良定的充要条件,从而将抗饱和补偿器设计问题转化为线性矩阵不等式约束的凸优化问题.最后通过仿真算例说明了所提出方法的有效性.     

Refinement preserving approximations for the design and verification of heterogeneous systems

Embedded systems are electronic devices that function in the context of a real environment, by sensing and reacting to a set of stimuli. Because of their close interaction with the environment, and to simplify their design, different parts of an embedded system are best described using different notations and different techniques. In this case, we say that the system is heterogeneous. We informally refer to the notation and the rules that are used to specify and verify the elements of heterogeneous systems and their collective behavior as a model of computation. In this paper, we consider different classes of relationships between models of computation and discuss their preservation properties with respect to the model's refinement relation and composition operator. In particular, we focus on abstraction and refinement relationships in the form of abstract interpretations and introduce the notion of conservative approximation. We show that, unlike abstract interpretations, conservative approximations preserve refinement verification results from an abstract to a concrete model while avoiding false positives. We also characterize the relationship between abstract interpretations and conservative approximations, and derive necessary and sufficient conditions to obtain a conservative approximation from a pair of abstract interpretations. In addition, we use the inverse of a conservative approximation to identify components that can be used indifferently in several models, thus enabling reuse across models of computation. The concepts described in this paper are illustrated with examples from continuous time and discrete time models of computation.     

Benchmarking the performance of manufacturing control systems: design principles for a web-based simulated testbed

The paper reports the main research activities currently carried out for designing and developing a test-bench service. This service would act as the main reference point for establishing benchmarks on which research results can be compared. These benchmarks will be made available through web technology. The paper, after a first outline of the main features of the project and its overall vision, is particularly focused both on the design principles related to the construction of good benchmark cases and on the technological issues related to the provision of a web-based simulation environment for supporting interactivity between remote scheduling and control systems and a locally resident simulation system.