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Network Design Consideration for Distributed Control Systems
... No entanto, o não determinismo inerente ao protocolo CSMA/CD pode levar ao não cumprimento dos limites temporais das aplicações críticas. O não cumprimento dos prazos pode ocasionar perda na qualidade do controle realizado, ou ainda resultar em um controle ineficiente (instável) [19], o que , por sua vez, pode trazer conseqüências desastrosas para aplicações críticas de controle. Em [6] define-se o conceito de margem de jitter para avaliar a implementação de sistemas de controle de tempo real sujeitos a atrasos de entrada e saída provocado pela politica de escalonamento de tarefas. ...
... No projeto de sistemas de controle de tempo real precisa-se lidar com incertezas inerentes a plataforma de computacão [6,5] e de comunicação [18,19]. Tais incertezas estão relacionadasàs variações no tempo de execução das tarefas (atraso de computação) e no envio e entrega das mensagens pelo subsistema de comunicação (atraso de comunicação). ...
O presente artigo avalia o desempenho de um detector de defeitos adaptável, baseado em redes neurais artificiais, quando aplicado a um Sistema de Controle Distribuído de tempo real sobre uma rede Ethernet. Simulações realizadas sobre um sistema simples de controle replicado, evidenciam as vantagens da referida proposta quando contraposta com as principais abordagens adaptativas existentes. Adicionalmente, constatou-se que, sobre certas condições, a sobrecarga causada pelo uso de detectores de defeitos não prejudica o desempenho de algoritmos de controle convencionais, como PID.
... Model predictive control is according to the running state of the system over the past time and present moment, more accurate forecasting system desired output value in the future moment, calculated control value of the system should be added according to output value desired depending on certain optimization algorithm adaptive computer control of online solving control value [7][8][9][10]. Visible, model predictive control algorithm is an adaptive control method based on the future state of controlled object or dynamic predictive value of output and online solving current control [8][9][10][11][12][13]. Model predictive control is a newer computer control algorithm developed in the late 1970s; the algorithm actually encompasses three steps: prediction model, rolling optimization and feedback correction [9][10][11][12][13][14][15][16]. ...
... Visible, model predictive control algorithm is an adaptive control method based on the future state of controlled object or dynamic predictive value of output and online solving current control [8][9][10][11][12][13]. Model predictive control is a newer computer control algorithm developed in the late 1970s; the algorithm actually encompasses three steps: prediction model, rolling optimization and feedback correction [9][10][11][12][13][14][15][16]. ...
Aiming at the issues of random delay and delay uncertainty in both the before channel and feedback channel for network control system, the root causes of random delay influence closed-loop control system by case is analysis, and the predictive control method based on neural network to solve the feasibility of existence network random delay in control system closed-loop control has provided. Simulation results show that the method can reflect and predict the delay characteristics of between measurement data represents the network path, and can effectively substitute for the actual network in the design of closed-loop control system based on Internet to research; the method used fast and accurate can be used for online learning network model and forecast the network delay value, provides a new way to remote closed-loop control based on Internet.
... There are various ways of exchanging information among distributed generators (DGs) such as wireless network, satellite based communication, Ethernet network, and internet. Conventional controllers consider the communication among DGs are continuous in nature, which leads to high communication traffic [3]. ...
... To better understand cyberattacks against ICS and PLCs, several honeypots have been proposed [19,9,3,27,51,18]. [26], Operational Technology (OT) [16], and Cyber-Physical Systems (CPS) [44]. ...
Industrial Control Systems (ICSs) provide management and control capabilities for mission-critical utilities such as the nuclear, power, water, and transportation grids. Within ICS, Programmable Logic Controllers (PLCs) play a key role as they serve as a convenient bridge between the cyber and the physical worlds, e.g., controlling centrifuge machines in nuclear power plants. Recently, ICS and PLCs have been the target of sophisticated cyberattacks designed to disrupt their operation. In this context, honeypots have been shown to be highly valuable tools for collecting real data, e.g., malware payload, to better understand the many different strategies that attackers use. However, existing state-of-the-art honeypots for PLCs lack sophisticated service simulations that are required to obtain valuable data and cannot adapt, while malware keeps evolving. This chapter presents HoneyPLC, a high-interaction, extensible, and malware-collecting honeypot supporting a broad spectrum of PLC models and vendors. Experimental results show that HoneyPLC exhibits a high level of camouflaging: it is identified as real devices by multiple widely used reconnaissance tools, and it is also able to record a large amount of interesting interactions over the Internet, showing that HoneyPLC can effectively engage and deceive attackers while collecting data samples for future analysis.
... A similar inference was made in [25] where Antsaklis et al stressed on incorporating efficient communication amongst controllers, system sensors, actuators etc. Considering the implementation of WNCS Willig et al [26] found that there the predominant issues influencing overall network performance and controllability are time delays, packet losses while during transmission [27]. With this motive, the authors recommended better network protocols, transmission scheduling [28] congestion control [29] and estimation [30] for both wired and wireless control systems. In a few kinds of literature it is found that there is an inevitable need to augment communication scheduling to retain the stability of controller [31]. ...
The exponential rise in the demands for reliable and fault resilient communication over Wireless Network Control Systems (WNCS) across industrial monitoring and control ecosystems has alarmed academia-industries to develop more efficient wireless transmission solutions. On the other hand, the emergence of cloud-assisted Internet-of-Things (IoT) also has broadened the demands for reliable WNCS systems. To cope up with such irreplaceable needs, WNCS has exploited different wireless communication paradigms including IPv6 Routing Protocol for Low Power Lossy Networks (RPL) based WSN that enables reliable communication across the industrial setup to make optimal real-time process decision. However, being dynamic in nature WNCS with often undergo link-outage due to dynamic topology, node death, congestion etc. Though, a few researchers have addressed the routing problem in WNCS; however, integrating RPL with mobility to enable optimal communication has remained untouched. Additionally, no significant research addressed fault-resilient routing decision over WNCS setup, which motivates us to develop a highly robust Fault-Tolerant and Reliable mobile-RPL Routing Protocol for W-NCS (FTmRP-NCS). Unlike classical WNCS models, FTmRP-NCS employs dual objective-based routing decision by considering the Received Signal Strength Indicator (RSSI) and the number of control packets required (ETX). Here, the inclusion of RSSI ensures forwarding path formation with most reliable link condition, while ETX objective function helps maintaining low control packets and hence low energy exhaustion, low redundancy and high efficiency. FTmRP-NCS applies link-sensitive mobile node movement for data gathering across WNCS, which makes overall communication more reliable as well as time-efficient. Furthermore, fault-sensitive routing decision strengthens our proposed FTmRP-NCS protocol helps WNCS to yield optimal performance. FTmRP-NCS has been applied over standard IEEE 802.15.4 protocol stack and functions in parallel to the link and network layer, which retains backward compatibility with native RPL and hence assures easy implementation with real-time WNCS environment.
... We use an integrated absolute error (IAE) as a metric to evaluate the recovery performance [25], [27]. IAE is defined as an integral of the absolute value of an error between the DC motor angle θ(t) and reference angle θ r (t). ...
Networks on the cyber-physical systems (CPSs) configure feedback control loops between physical systems in the real world and control software in the cyber world. Malicious behaviors on the networks can increase network delays by exhausting limited network resources and security vulnerabilities to destabilize CPSs, which are entitled the network delay attack. In this paper, we focus on the problem of how to guarantee the stability of CPS under the network delay attack. We propose a real-time controller reconfiguration to ensure the resiliency of the physical systems against the network delay attack. Our controller reconfiguration consists of two algorithms: controller gain tuning and access point (AP) handover, which give a delay tolerance and an attack avoidance, respectively. Depending on the network delays, the computing system adopts one of these two algorithms and mitigates the physical impacts of the network delay attack. We validate that the proposed controller reconfiguration can ensure the resiliency of CPS against the network delay attack by implementing a testbed with wireless networks.
... In a WSN, sensor nodes are the basic unit for sensing and collecting external information and the coverage rate of all nodes can reflect the monitoring and tracking of information in the region, which is an essential embodiment of WSN service quality [43][44][45]. Hence, this paper takes the coverage rate as the evaluation index of coverage optimization and focuses on the maximization of coverage rate in monitoring areas. ...
Burgeoning swarm intelligence techniques have been creating a feasible theoretical computational method for the modeling, simulation, and optimization of complex systems. This study aims to increase the coverage of a wireless sensor network (WSN) and puts forward an enhanced version of the sparrow search algorithm (SSA) as a processing tool to achieve this optimization. The enhancement of the algorithm covers three aspects. Firstly, the Latin hypercube sampling technique is utilized to generate the initial population to obtain a more uniform distribution in the search space. Secondly, a sine cosine algorithm with adaptive adjustment and the Lévy flight strategy are introduced as new optimization equations to enhance the convergence efficiency of the algorithm. Finally, to optimize the individuals with poor fitness in the population, a novel mutation disturbance mechanism is introduced at the end of each iteration. Through numerical tests of 13 benchmark functions, the experimental results show that the proposed enhanced algorithm can converge to the optimum faster and has a more stable average value, reflecting its advantages in convergence speed, robustness, and anti-local extremum ability. For the WSN coverage problem, this paper established a current optimization framework based on the swarm intelligence algorithms, and further investigated the performance of nine algorithms applied to the process. The simulation results indicate that the proposed method achieves the highest coverage rate of 97.66% (on average) among the nine algorithms in the calculation cases, which is increased by 13.00% compared with the original sparrow search algorithm and outperforms other methods by 1.47% to 15.34%.
... In many existing works such as [27]- [29], an interval time-varying delay is considered where only the bounded information of delay are involved in stability analysis. In fact, under certain communication protocols such as the Internet Protocol (IP) and the IEEE 802.11, transmission delay can be characterized by its probability density function [30], which can be obtained via some statistical approach. In light of this idea, a delay-distribution method is used to study the event-triggered guaranteed cost control issue for Markov jump discrete-time NNs [31] and the synchronization problem of stochastic memristor-based NNs [32], where the time delay is categorized as short delay and long delay through the introduction of a Bernoulli variable. ...
This article studies the design of fuzzy synchronization controller of Takagi—Sugeno (T-S) fuzzy neural networks with distributed time-varying delay and probabilistic network communication delay. Compared with the existing model of neural networks with distributed time-varying delay without kernel, a more general model containing a distributed delay kernel is considered. By utilizing the probability distribution of random communication delays, a distributed but deterministic delay model is established. In this model, the delay probability density function is treated as the distributed delay kernel. By developing a new Lyapunov-Krasovskii functional (LKF) related to the distributed delay kernels and using an integral inequality, new sufficient conditions for the existence of a synchronization controller are presented. Finally, a numerical simulation and an application of encrypting the image are carried out to illustrate the effectiveness of the developed strategy.
... El desarrollo y aplicación de robots modulares ofrecen ventajas tales como la re-utilización de los módulos, el procesamiento descentralizado o la abstracción del bajo nivel. No obstante, al igual que cualquier otro Sistema de Control Distribuido (DCS), deben cumplirse unos requisitos de tiempo real en las comunicaciones [10]. El uso de sistemas modulares basados en ROS ofrece amplias ventajas como la estandarización de módulos, la reutilización de los algoritmos o la opimización de la ejecución de los mismos [16]. ...
Actualmente, las plataformas para robots que implementan ROS son ampliamente usadas en investigación. Éstas han probado ofrecer una solución fiable para reutilizar algoritmos. No obstante, estos cuentan con ciertos inconvenientes. Aunque la arquitectura ROS ha sido diseñada con la posibilidad de trabajar de forma distribuida, este diseño presenta algunos problemas al gestionar un gran número de dispositivos los cuales requieren de un flujo de datos en tiempo real. En este trabajo se presenta una arquitectura de comunicaciones para solucionar este problema. Además se valida dicha arquitectura por medio de un robot modular a partir de dispositivos totalmente desacoplados. Un robot modular puede presentarse como un Sistema de Control Distribuido (DCS, por sus iniciales en inglés), donde las tasas de transmisión y el flujo de datos debe ser acotado para poder garantizar una correcta ejecución. Por lo tanto, se detalla como solucionar el problema de comunicación distribuida entre nodos ROS posibilita el intercambio de datos de forma fácil y segura. Como consecuencia se propicia el desarrollo de sistemas modulares basados en ROS. Por último se realiza una comparación entre el desempeño del sistema obtenido cuando se implementa una distribución ROS clásica, y el obtenido cuando se utiliza la arquitectura de comunicaciones propuesta.
... In smart cities, due to the uncertainly of the users' behavior, and the multiple inputs and outputs to manage, the eventbased control is a convenient approach instead of the periodic sampling control approach. When the control is event-based and distributed, measure the optimal action is difficult due to the result depends on the multiple outputs [13]. For example, to diagnose lighting needs on the street, it is necessary to know the light intensity at different points, the street users' needs at these points, and how they expect to evolve as time goes by. ...
Intelligent control of public lighting is nowadays one of the most challenging issues in smart city deployment. Lighting optimization entails a compromise between comfort, safety, and power consumption, affecting both vehicles and pedestrians. Smart solutions must estimate their characteristics to trade-off users’ needs and energy requirements. This paper proposes an intelligent street lighting control system and the Receiver Operating Characteristic (ROC) curve method to evaluate the best number of street lamps to achieve a balance between public road user comfort and system power consumption. The control system is based on the detection of users, mainly pedestrians, using presence sensors. From the detection of a pedestrian by two or more consecutive street lamps it is possible to determine their speed. Knowing the pedestrian speed, allows the system to anticipate and adjust the light intensity of the remaining street lamps, and provide a comfortable view of the street. Using the ROC curve, we evaluate the control algorithm in terms of the number of previous street lamps used. We have tested the system and the method in a model of pedestrians walking down a street. The obtained results show that ROC analysis used to control street lighting allows measuring the whole control system’s efficiency by providing a concrete number of previous street lamps.
... In our case, the domain gateway was a necessary design element, but given how crucial its role turns out to be in the design of the fallback strategy, the use of such a gateway as a principle of centralized E/E architecture design will be investigated further. Some other elements to consider are discussed by Lian et al. [13]. ...
... Moreover, we discuss thoroughly the derived numerical results and provide useful insights into the actual real-time requirements of the control system when seen in relation to the specific application that the aforementioned system has to serve. We conclude that, with this model, the response time of any control system can be accurately calculated, under distinct operating conditions and programmed settings, unlike the models at hand that consider only traditional fieldbuses without real-time functionality [3,7]. ...
Abstract Large‐scale infrastructure and industrial projects face schedule delays, cost overruns and performance shortfalls. One cause is the late delivery of their control systems that end up being complex and unsuited. To overcome this problem, an innovative industrial control system is proposed that can be commissioned almost effortlessly and delivered on time without functional defects in most large‐scale industrial and infrastructure construction projects, while offering high capacity (>25,000 filed devices scanning >100,000 signals) and straightforward scalability, upgradability and maintainability. Designed with a central controller and distributed sensing and actuating devices, and equipped with a cluster of servers and an Ethernet network transporting video, voice and data (>300 video and >750 voice streams), it integrates plant automation technologies with data communication techniques, allowing industrial and information technology applications to coexist and cooperate. While being tolerant to faults and fast in its response, it provides high safety integrity level (>SIL 2) and real‐time automatic reaction in repetitive stimuli or occasional events (programmable from 5 to 250 ms). In this paper, with the provided system blueprint and engineering guidelines, this novel system architecture can be built with off‐the‐shelf components seamlessly integrated in the context of Cyber Physical Systems.
... In distributed control framework, control task is assigned to various connected distributed units based on the resource availability and urgency. This control hierarchy constitutes primary, secondary and tertiary levels of resources [3], [4]. ...
Cyber-physical systems are becoming core of the most modern systems consisting control, data sharing and real-time monitoring. While centralized control technique has been implemented in the past, recent innovation in distributed control schemes makes it attractive due to various reasons. One of them is the use of state-of-the-art communication protocols that makes the system more robust toward extreme conditions and ensures observability. Thus, as an application of cyber-physical systems, distributed control architectures are prone to various cyber-vulnerability which makes cybersecurity research critical in this application domain. This paper reviews recent researches of distributed control architectures, their cyber-vulnerabilities, and reported mitigation schemes. Finally, some research needs are addressed.
... Scheduling method was also proposed in other to solve the problem of delay in networked control system. Kim et al. (D. S. Kim, D. H. Choi, 2009) proposed obtaining a maximum allowable delay bound for the scheduling of networked discrete control systems. Also Lian et al. (F. L. Lian, J.Moyne, 2002) who studied the key components of time delay to provide guidelines for obtaining the optimal working range of sampling times. Walsh et al. (G.C.Walsh, H.Ye, 2002) introduced a novel control network protocol, try-once-discard (TOD), for multiple-input-multiple-output NCSs. But these works did not consider the use of switched Ethernet in ...
One of the major concerns in networked control system is networked-induced delay. The real-time industrial network, often referred to as fieldbus, is an important element for building automated manufacturing systems. Thus, in order to satisfy the real-time requirements fieldbus protocols were developed. These fieldbus protocols have an important advantage over the widely used Ethernet in terms of their deterministic behavior. However, the application of fieldbuses has been limited because of the high cost of hardware and the difficulty in interfacing them with multivendor products, as a result led to further improvement of Ethernet to switched Ethernet. The use of the 100M Switched Ethernet technology is more efficient when the real-time process shares the same medium with other applications due to its large bandwidth. This research work is focused on delay compensation in 100M switched Ethernet using a fuzzy adaptive Proportional Integral Derivative (PID) controller for Networked control system, with the aim of making it more deterministic. The result obtained from this simulation of fuzzy adaptive PID controller was compared to PID and Fuzzy_PID controllers. MATLAB/Simulink was employed in the system implementation of the model. The result however, showed that the signal of Fuzzy adaptive PID had no overshoot and lesser settling time, which indicates more stability.
... Mitochondria perform unique roles in diverse tissues but together, by communicating among each other, safeguard the effective integration, sensing and signalling of metabolic information. This multi-site stress modulation of metabolism shows distributed control networks, renowned for improving the function of complex systems 10 . This fascinating set of mitochondrial functions, from cellular to behavioural, leads us to contemplate the possible association of these multifunctional organelles as a connection between metabolic dysregulation and psychopathology 11 . ...
... The proposed fallback strategy relies on a number of research results, including synchronization and distributed control algorithms [41]. It is also necessary to determine whether the performance of such a strategy can be sufficient to take over control in a domaincentralized setting. ...
... In addition, much effort has been devoted over the past few years (e.g., [4][5][6][7][8][9][10][11][12][13]). e research enthusiasm of network-induced problems in NCSs reveals the contradiction between QoP (Quality of Performance) and QoS (Quality of Service), i.e., the continuous improvement of QoP demand and the practical constraints of QoS guarantee [14]. To solve such a contradiction, researchers of this area focused on active network scheduling and collaborative control and achieved much progress. ...
Specific to the NCSs where sensor signals can be processed centrally, a collaborative design scheme of dynamic game scheduling and advanced control theory was proposed in the present study. Firstly, by using the Jordan standard state space equation of the research object, the three elements of state noncooperative game were built, and the existence and uniqueness of Nash equilibrium solution were verified. In addition, the iterative equation of the scheduling matrix was derived by complying with the designed utility function. Secondly, refer to the number of restricted states the order of sliding mode was determined. And based on it, the corresponding sliding surface was designed. Subsequently, the quadratic optimization theory was adopted to regulate the control value following the implementation of the scheduling strategy to ensure that the control quality was further enhanced in the limited network service. Lastly, a TrueTime simulation example is established to verify the effectiveness of the proposed scheme.
... Networked control system (NCS) is a control system where the closed control loop includes communication network [1,2]. The developments in wired and wireless communication networks have given rise to the NCS due to its advantages in cost, installation, and maintenance. ...
Networked control systems are widely spread, which is composed of numerous sensor and control nodes through communication channel. In this paper, an event-triggered H ∞ memory output feedback control (EMOFC) is investigated for networked control linear systems in discrete form. The memory control employing memorized past information is exploited to enhance the triggering intervals under event-triggered condition. Moreover, novel summation type event-triggering condition is newly proposed by utilizing buffer memory element. Based upon memory control and novel triggering conditions, the control design methodology is constructed for transformed input-delay model in forms of linear matrix inequalities (LMIs) adopting generalized free-weighting matrix summation inequality. As a result, the proposed scheme shows off the reduction of average signal transmission frequency and reliability while covering standard condition. Throughout numerical examples, the effectiveness is shown and the effect of memory element is analyzed.
... There should be ability in actuator to crack information's from network medium and send it to the physical devices. For further explanation of performance evaluation of network study [11]. ...
The Spectrum sharing is an important topic in Cognitive Radio Sensor Networks (CRSNs). Bio-inspired consensus-based schemes can provide lightweight and efficient solutions to ensure spectrum sharing fairness in CRSNs. This paper studies the consensus performance of traffic management system in Cognitive Radio Networks (CRNs). Research focused on significant topics of spectrum management in scalable CR ad hoc networks such as mobility, sharing, and allocation driven by local control. First of all, CRN is analyzed and is considered as a network of multiagent systems with a directed graph. Secondly, this multiagent problem is transformed into the multi-input and multi-output model of cognitive radio users in the frequency domain. Thirdly, the consensus condition of CR users is proposed based on their information sharing in the network. Moreover, the communication delay is also considered and a delay margin criterion is derived to guarantee the performance of information sharing for CR users. From simulation results, the use of proposed schemes shows low complexity and effectiveness for spectrum sharing processes in randomly deployed CRSNs also shows the effectiveness of the proposed method.
... Time delay estimation techniques have been used in various branches of physical science and technology [20,21,22]. Traditionally these are used in the area of signal processing for communication [20] and controlled processes [23,24,25]. In many real processes, the time delay is a priori unknown or time varying, in some circumstance, process parameters may be time-varying also, therefore real time delay and parameter estimation approaches are necessary. ...
It is quite challenging to identify in one step a nonlinear model with time delay due to the nonlinear relationship between the time delay and the other model parameters. Therefore, a two step procedure for estimating the system parameters and the time delay is proposed in this paper: The first step is to estimate the parameter vector using the gradient approach. Assuming that the lower and upper bounds of the time delay are known in advance, the Variable Regression Estimation technique is applied as the second step to identify the time delay. The convergence analysis of the proposed algorithm indicates that the parameter estimation errors converge to zero under persistent excitation conditions. Simulation results are presented to illustrate the performance of the proposed method.
... However, due to the vast application of communication links consisting of WiFi, WiMax, Internet, and Ethernet in the smart grid, microgrid, and power controllers, the signals between these units may be delayed during their transmission [73][74][75][76][77]. The characteristics of network-induced time delays are random, bounded, and constant, which depend on the internal performance of the communication system [78]. In addition to time delay, the operation of controllers in microgrids can be affected by the sampling rate of these communication systems. ...
The objectives of this paper are to review and compare the distributed control methods in AC microgrids and also to identify the impact of communication failure on this type of the controller. The current AC microgrids are distinguished from the traditional power system topologies because of the high penetration of advanced control methods, measurements, sensors, power electronic devices, and communication links. Also, because of the increasing integration of renewable energy sources, control strategy for congestion management, frequency control, and optimal dispatch of microgrids has become more complicated. This paper explains the characteristics and features of distributed control systems and discusses the challenges of these approaches. In addition, a comprehensive review of the advantages and disadvantages of these techniques are explained in detail. On the other hand, the possible challenges, related to communication failure, noise, delay, and packet dropout on the operation of the distributed controller are presented, and several techniques, which reduce the impact of communication failure of the distributed controller, are compared. This comprehensive study on distributed control systems reveals the challenges in and future possible studies on this issue.
... The existing transmission periods for NCSs are mainly predefined. Data transmission is time-triggered, and several previous studies [1,12,13,14] provide promising guidelines for offline transmission period decisions in time invariant linear systems. Theoretically, an NCS network could also be better designed by selecting an acceptable transmission period range. ...
Physically distributed/networked control systems often feature larger signal transmission time delays than traditional field wire-connected control systems, which cna strain limited network bandwidth. Because the maximum ideal data transmission period varies during hte control process, it is essential to determine the data transmission period dynamically, online. Taking these issues into consideration, this paper will study the varying input networked/distributed control systems and present an innovative design for automating dynamic data transmission period decisions. This design's effectiveness is demonstrated by means of a simulated distributed control system.
To break the dilemma of data island, a distributed framework for trustable control is proposed toward information security and data privacy in large-scale cyber-physical systems. The federated control system consists of distinct blockchains, as such information security and data privacy are technologically guaranteed. Moreover, data are divided into private and nonprivate data. Only nonprivate data can be exchanged for a better global system performance, where the interblockchain communication is ensured by cross-blockchain technologies. Federated control framework establishes a trustable environment where each subsystem is willing to share data for optimal performance. The architecture, structure, and implementation process of federated control are discussed, together with the potential applications to smart buildings.
Time has become an essential aspect of many computing systems where temporal correctness is as important as functional correctness. Autonomous vehicles, Industry 4.0, and smart grids are a few examples of time-sensitive systems. As time-sensitive applications become large, complex, and distributed, traditional methods fall short of achieving the desired orchestration among components. In this vision article, we first propose a standard to maintain an accurate notion of time among all components of the system, i.e., sensors, computing platforms, and actuators. Then, we propose explicit-time state estimation and closed-loop control algorithms that can tolerate large delays while achieving reasonable performance, and an integrated fail-safe mechanism that achieves a high level of robustness when timing failures happen.
In this paper, the problem of adaptive bipartite tracking control for nonlinear multi-agent systems with unmatched disturbances and backlash-like hysteresis is investigated. Cooperative and competitive relationships in multi-agent systems are taken into account, which represents a frequently occurring situation. To decrease unnecessary data transmissions, an innovative distributed adaptive self-triggered control protocol is proposed. In contrast to the traditional self-triggered control strategy, the scheme designed in this paper can adaptively adjust the trigger intervals according to system performances. Furthermore, a command filter is introduced into the design process to solve the problem of complexity explosion. The effect of backlash-like hysteresis is successfully compensated by the designed controller. Finally, a practical example is implemented to demonstrate the effectiveness of the proposed scheme.
Transport infrastructure projects -more often than not- face program delivery delays, budget overage and performance deficiencies. One of the root causes is the belated delivery of their data acquisition and control systems that turn out to be complicated and unable to provide the intended functions. To avoid this problem in Doha Metro, Qatar Rail designed and built an innovative building automation and control system (BACS) that was tested and commissioned easily, delivered without delays and functional defects and made possible the authorized start-up of revenue operations. Engineered with one central controller, one cluster of servers, one switched optical ring and multiple sensing and actuating devices on copper rings, BACS amalgamated automation technologies and data networking techniques over one common communication platform, offering seamless plant integration, undemanding scalability and straightforward maintainability. Implemented with hardware and software redundancies and fault recovery techniques, BACS was able to achieve safety integrity level (SIL) above 2, providing fire-life-safety (FLS) and mission critical functions. Hence, BACS was qualified by the Authority Having Jurisdiction, the Qatar Civil Defence Department of the Ministry of Interior, to initiate the required by the fire code effects in the detected by the fire alarm system causes (cause and effect functionality), in addition to the supply of daily control and supervision services with real-time automatic responses in Doha Metro.
This paper presents a comprehensive solution to mitigate network congestion in T-S fuzzy networked control systems (NCSs) caused by denial-of-service (DoS) attacks and quality-of-service (QoS) queuing mechanisms. We develop a novel data compression mechanism to alleviate network congestion and use a mini-batch descent gradient algorithm to optimize trigger thresholds, thereby reducing bandwidth usage. Additionally, we introduce asymmetric Lyapunov-Krasovskii functions (LKFs) to decrease the number of decision variables, which improves the reliability and robustness of the control algorithm. Finally, we propose an intelligent event-triggered controller (IETC) supervised by mini-batch machine learning and validate it on the joint CarSim-Simulink platform. Experimental results demonstrate that our approach reduces the sensitivity of autonomous vehicle (AV) systems to network fluctuations while ensuring system stability under network congestion caused by DoS attacks.
The existing containment control has been widely developed for several years, but ignores the case for large-scale cooperation. The strong coupling of large-scale networks will increase the costs of system detection and maintenance. Therefore, this paper is concerned with an extensional containment control issue, hierarchical containment control. It aims to enable a multitude of followers achieving a novel cooperation in the convex hull shaped by multiple leaders. Firstly, by constructing the three-layer topology, large-scale networks are decoupled. Then, under the condition of directed spanning group-tree, a class of dynamic hierarchical containment control protocol is designed such that the novel group-consensus behavior in the convex hull can be realized. Moreover, the definitions of coupling strength coefficients and the group-consensus parameter in the proposed dynamic hierarchical control protocol enhance the adjustability of systems. Compared with the existing containment control strategy, the proposed hierarchical containment control strategy improves dynamic control performance. Finally, numerical simulations are presented to demonstrate the effectiveness of the proposed hierarchical control protocol.
This paper addresses the state derivative feedback control problem for uncertain polytopic systems subject to an uncertain sampling period and network‐induced delay. The distinctive contribution relies on the direct design of a robust state derivative feedback controller employing an augmented discretized model derived in terms of the state derivative feedback such that network‐induced delay and uncertain sampling periods can be incorporated from the original continuous‐time state‐space representation into the discretized model. Two augmented models are provided to handle longer input time delays, as well as delays less or equal to the sampling period. In this work, all the uncertain parameters are modeled as a polytopic form whose resulting discrete‐time model has matrices with polynomial dependence on the uncertain parameters and an additive norm‐bounded term featuring the discretization residual error. Moreover, synthesis conditions are derived using a set of linear matrix inequalities (LMI) to solve the stabilization problem for this class of systems under different input time delays. Finally, numerical simulations are carried out to evaluate the effectiveness of the proposed method.
This paper proposes an improved security-based event-triggered fuzzy control (ETFC) method for studying the asymptotic stability (AS) problem of nonlinear networked control systems (NCSs) under denial-of-service (DoS) attacks. The nonlinear NCSs are linearized using the central mean fuzzy method to obtain T-S fuzzy NCSs. Lyapunov-Krasovskii functionals (LKFs) with nonlinear problems are constructed based on fuzzy membership functions (FMFs). A relaxed condition including nonlinear parameters is given, which considers the nonlinear optimization problem and reduces the positive definiteness constraint problem of LKFs. An improved doubleclosed delay correlation function is constructed to obtain more sampling information. Furthermore, a quadratic scaling method is used to obtain a tighter upper bound, making the criterion less conservative. A DoS attack causes the channel's throughput to drop and collapse. Thus, we design ETFC based on the improved descent gradient algorithm to ensure the communication security of the helicopter system (HS). Finally, the communication security and stability of HS are verified using the Simulink platform.
In this article, a distributed-delay-dependent method is proposed to deal with the stabilization for interval type-2 Takagi–Sugeno fuzzy systems subject to stochastic network delay and actuator saturation. To deal with the stochastic feature of network-induced delays, their probability density function is utilized to establish the distributed delay model, which is more practical than the traditional time-varying network delay model. Meanwhile, in order to enlarge the estimation of the domain of attraction, a polytopic strategy composed of a state vector and a distributed-delay-dependent vector is proposed to treat the saturation nonlinearity. By constructing a distributed-delay-dependent Lyapunov–Krasovskii functional, new and less conservative conditions are achieved to guarantee the stability of the established closed-loop system. Additionally, two simulation examples are carried out to illustrate the advantages of the proposed strategy.
Low-inertia operation of small-scale power systems, such as a microgrid or a portion of a long feeder, requires careful coordination of the controller performance of the constituting devices. This challenge is exacerbated in microgrids serving the functionalities of a conventional synchronous-based generation unit while comprised of smaller DERs operating mainly interfaced through power electronics converters. This paper builds on the idea of set point modulation and proposes a two-level control strategy that aims to achieve superior performance at the point of common coupling (PCC) of microgrids by combining a local control level with a distributed and coordinated level. Several case studies on both AC and DC systems, the CIGRE low-voltage benchmark system as the AC system and a test DC microgrid, validate the performance of the proposed approach. The real-world applicability of the approach is established via a high-fidelity power hardware-in-the-loop (PHIL) experimental setup and an application case study on grid frequency regulation. The proposed approach enables a microgrid to participate in ancillary service provisions where speed and quality of regulation are critical.
Time synchronization is an indispensable requirement for industrial networks. A prominent time synchronization protocol for industrial applications is based on the well-known IEEE 1588 standard. This letter investigates a bandwidth efficient clock skew estimation scheme for IEEE 1588 enhancement, which embeds skew estimation tasks into the network data traffic, to provide improved clock skew estimation without additional bandwidth overhead. A minimum conditional risk invariant estimator is derived that is capable of estimating the clock skew under arbitrary delay models. Simulation results demonstrate the effectiveness and performance enhancement of the proposed estimator.
Two methods for sparse control of decentralized systems are used in this paper. Firstly, a decentralized event-triggered transmission scheme is performed to sparse sampled signals before transmitting them to the controller. Secondly, the number of the decentralized controller-actuators channels is constrained, and is equivalently transformed to the number of non-zero rows in the controller gain matrix. The cardinality constraint problem is solved by using a mixed integer method. In addition, \(H_{\infty }\) stability analysis and controller design are performed for the proposed system using Lyapunov-Krasovskii functional method. Finally, the effectiveness of the proposed method is illustrated by a simulation example.
KeywordsSparse controlDecentralized controlEvent-triggered\(H_{\infty }\) Control
This paper focuses on the observer-based controller design issue for a class of discrete-time networked nonlinear systems. Due to the stochastic effects, the switching between subsystems occurs. The persistent dwell-time switching mechanism, which is more general than dwell-time switching and average dwell-time switching mechanisms, can well describe these switching cases with both fast and slow switchings. Furthermore, there is packet dropout during data transmission, which is described by Bernoulli white sequence, and a corresponding mechanism is used to compensate for the impact of packet dropout. Then based on the Lyapunov function approach, some sufficient conditions for mean-square exponentially stable and an expected H∞ performance are derived. Finally, an illustrative example that demonstrates the superiority and feasibility of the proposed method is given.
The task is closely related to networked semi- active suspension control system. It is suggested to use an identification approach for damping parameter calculation of each wheel (quarter car model), then make regulation of only one parameter- damping one- according to current situation. To do that closed loop to adjust damping parameter accordance with desired reference signal is formed. Full structure of networked semi active suspension system using CAN bus protocol is presented. An additional task related with estimation of network influence on the performance of the whole combined damping system is also carried out, that the consideration of the network influence as a pure delay is approximate and doesn’t take into account a lot of network functional features. Simulation of networked quarter car model together with feasible suspension control law, central processor and CAN physical model on the base of National Instruments equipment’s was fulfilled. Experiments carried out with mathematical and physical models showed the workability of suggested solutions.
Delay phenomena are commonly encountered in modeling population dynamics, transportation, propagation, and interactions between coupled dynamics through material, energy, and communication flows. Time-delay systems (TDSs) have been widely investigated in the past decade following the explosive growth of communications and network exchanges. It turns out that time-delays are ubiquitous in technologically-based control systems and possibly degrade the closed-loop system performance. To this end, this chapter addresses the role of delays and surveys major issues pertaining to stability and stabilization of time-delay control systems. In particular, the covered materials include the following:
•Fundamental analytical results are provided throughout as key lemmas to shed light on the contemporary development in stability of TD systems.
•The linear matrix inequality (LMI) framework is deployed in deriving delay-dependent stability and stabilization results.
•Particular emphases are placed on the conservatism and the computational complexity of the results.
•Several theorems are developed and supported by remarks to emphasize point-by-point technical results.
•Detailed technical design results are presented and concluded by an outlook of suggestions for future research directions.
This chapter is an extended overview of the author's ideas and contributions to the spectrum-based tuning of controllers designed for linear time-invariant time-delay systems. Numerous control design methods and techniques yield an infinite-dimensional feedback control system. Then we have to deal with infinitely many feedback system poles. The rightmost (dominant) subset of the spectrum ought to be suitably placed to the stable (i.e., open left-half complex plane) region. However, there is a lack of reliable pole placement methods applicable in practice. Especially, time-delay systems of neutral type are difficult to be handled. Hence the author attempts to propose a procedure by adopting an algebraic approach via the ring of stable and proper quasipolynomial meromorphic functions. There are two controller parameters tuning principles used here. Namely, as first, a spectral abscissa minimizing is performed by applying the quasicontinuous shifting algorithm, followed by the use of direct-search optimization algorithms. As second, the reader is acquainted with the simultaneous placing of the dominant (i.e., the rightmost) poles and zeros of the eventual infinite-dimensional feedback control system. This procedure is done by matching the actual roots loci with the desired ones. The selection of desired zeros and poles loci is based on a simple finite-dimensional model and time responses of which are known. Meanwhile, the remaining parts of the spectra are shifted to the left to minimize the spectral abscissae. Although retarded systems are mostly considered, the reader is provided with some notes on the use of the proposed techniques to, more tricky, neutral-type systems. Theoretical ideas and algorithms are supported by simulation (numerical) examples that indicate advantages and drawbacks of the proposed methods. Eventually, open tasks and possible future research are concisely highlighted. For instance, we discuss advanced cost function selection or the transition from the system spectrum to its pseudospectrum to get better robustness.
Time-synchronization technology can provide a common notion of time among the participating nodes on a network. This is essential not only for protocol operation for time-critical services but also for the time stamp for information included in the message. Precise time information can be very crucial for such things as autonomous driving because there are various sensor measurements from multiple cameras, and radio detection and ranging (radar) and light detection and ranging (LiDAR) are used for perceiving the current situation via sensor fusion. A well-known synchronization method, IEEE 1588, denoted as the precision time protocol (PTP), can be used for various applications. For in-vehicle networks of autonomous cars, we have to consider that the network may be comprised of subnetworks based on different protocols such as controller area network (CAN) and Ethernet. However, implementing PTPs on such heterogeneous vehicle networks causes several problems. First, the PTP procedure must be modified to be implement on a CAN network. Second, to calculate the delay and offset for PTP, the processing delay that occurs during message conversion must be considered. In this paper, we propose a synchronization method for CAN–Ethernet networks to solve these problems. The performance of the proposed synchronization method is evaluated by experiments on a real CAN–Ethernet network.
Abstract—The dynamic response speed of the secondary control
(SC) in microgrids (MGs) is limited both by the communication
network time delays and the bandwidth (BW) of
the primary control (PC). By increasing the PC BW, which
depends on how to design and tune the PC, the time delay
issues will be multiplied due to the speed range of the
communication modules and technologies. This paper proposes
a communication compensation block (CCB) to enhance the
robustness of distributed SC against communication impairments
in the MGs operated at the higher BW. The proposed method
mitigate malicious time delays and communication non-ideality
in distributed networked controls employed in the secondary
layer of the MG by prediction, estimation and finally decision
on transmitted data. A comprehensive mathematical model of
the employed communication network is presented in details.
Then, a robust data prediction algorithm based on the temporal
and spatial correlation is applied into the SC to compensate for
time delays and data packet loss. Furthermore, the effect of the
number of stored packets and burst packet loss on the average
success rate of the communication block, and the small signal
stability analysis of the system in the presence of the CCB are
investigated. Power hardware-in-the-loop (PHiL) experimental
tests show the merits and applicability of the proposed method
Accurate and real-time position of preview point is significant to trajectory tracking control of vision-guided intelligent vehicle. The unavoidable delay of road automatic identification system weakens trajectory tracking control performance, and even deteriorates the vehicle stability. Therefore, a compensator for the delay of road automatic identification system was proposed which combines the current statistical model and adaptive Kalman predictor to estimate the state of preview point position. The trajectory tracking sliding mode controller of intelligent vehicle is established through a 2–degrees of freedom vehicle dynamic model and motion model by using MATLAB/Simulink and CarSim. The trajectory tracking performance under 20–100 ms delay is analyzed. The simulation results show that the trajectory tracking performance of intelligent vehicle will be affected by the delay of road automatic identification system, reducing tracking accuracy. And when the delay is too large, it will deteriorate the vehicle stability and safety. In addition, the simulation results also verify the effectiveness of current statistical–adaptive Kalman predictor compensator at different delays.
The dynamic response speed of the secondary control (SC) in microgrids (MGs) is limited both by the communication network time delays and the bandwidth (BW) of the primary control (PC). By increasing the PC BW, which depends on how to design and tune the PC, the time delay issues will be multiplied due to the speed range of the communication modules and technologies. This paper proposes a communication compensation block (CCB) to enhance the robustness of distributed SC against communication impairments in the MGs operated at the higher BW. The proposed method mitigate malicious time delays and communication non-ideality in distributed networked controls employed in the secondary layer of the MG by prediction, estimation and finally decision on transmitted data. A comprehensive mathematical model of the employed communication network is presented in details. Then, a robust data prediction algorithm based on the temporal and spatial correlation is applied into the SC to compensate for time delays and data packet loss. Furthermore, the small signal stability analysis of the system in the presence of the CCB is investigated. Power hardware-in-the-loop (PHiL) experimental tests show the merits and applicability of the proposed method.
The goal of this study is to introduce a new design approach of the EPCglobal network considering activities of actors in a supply chain via agent-based simulation (ABS). The EPCglobal network provides track and trace services of shipments for internal and external subscribers, based on electronic product code (EPC) data generated from radio frequency identification (RFID) tags. To maintain dependable mean response time and service failure of the network, the proposed approach consists of two modules: (1) ABS module with AnyLogic® simulation software involving transactions between actors (manufacturers, distributors, and retailers) and (2) Network partitioning module to find appropriate structure of the network based on responses given by the ABS module. Demonstration of the proposed approach will be conducted with data of an automotive supply chain in Republic of Korea. This preventive maintenance approach will help engineers avoid over-investment on implementation of the network for their efficient supply chain management.
Industrial Control Systems (ICSs) play an important role in today’s industry by providing process automation, distributed control, and process monitoring. ICS was designed to be used in an isolated area or connected to other systems via specialised communication mechanisms or protocols. This setup allows manufacturers to manage their production processes with great flexibility and safety. However, this design does not meet today’s business requirements to work with state-of-the-art technologies such as Internet-of-Things (IoT) and big data analytics. In order to fulfil industry requirements, many ICSs have been connected to enterprise networks that allow business users to access real-time data generated by power plants. At the same time, this new design opens up several cybersecurity challenges for ICSs.
We review possible cyber attacks on ICSs, identify typical threats and vulnerabilities, and we discuss unresolved security issues with existing ICS cybersecurity solutions. Then, we discuss how to secure ICSs (e.g., using risk assessment methodologies) and other protection measures. We also identify open security research challenges for ICSs, and we present a classification of existing security solutions along with their strengths and weaknesses. Finally, we provide future research directions in ICS security.
The paper presents the results of an ICCS analysis focusing on discrete-time control systems subject to time-varying delays. The present analytical technique is applicable to integrated dynamic systems such as those encountered in advanced aircraft, spacecraft, and the real-time control of robots and machine tools via a high-speed network within an autonomous manufacturing environment. The significance of data latency and missynchronization between individual system components in ICCS networks is discussed in view of the time-varying delays.
Integrated Communication and Control Systems (ICCS), recently introduced and analyzed in a series of papers are applicable to complex dynamical processes like advanced aircraft, spacecraft, automotive, and manufacturing processes. Time-division-multiplexed computer networks are employed in ICCS for exchange of information between spatially distributed plant components as well as for coordination of the diverse control and decision-making functions. Unfortunately, an ICCS network introduces randomly varying, distributed delays within the feedback loops in addition to the digital sampling and data processing delays. These network-induced delays degrade the system dynamic performance, and are a source of potential instability. This two-part paper presents the synthesis and performance evaluation of a stochastic optimal control law for ICCS. In this paper, which is the first of two parts, a state feedback control law for ICCS is formulated by using the dynamic programming and optimality principle on a finite-time horizon. The control law is derived on the basis of a stochastic model of the plant which is augmented in state space to take into account the effects of randomly varying delays in the feedback loop. The second part [see the paper reviewed below] presents numerical analysis of the control law and its performance evaluation by simulation of the flight dynamic model of an advanced aircraft.
This paper presents the results of an ongoing research project where the objectives are to evaluate medium access control (MAC) protocols in view of the requirements for distributed digital flight control systems (DDFCS) of advanced aircraft and to recommend a specific protocol for their prototype development. The selection of an appropriate MAC protocol is critical for the dynamic performance of an aircraft because the DDFCS, in addition to the sampling time delay, is subject to time-varying transport delays due to data latency of messages at different terminals of the control loop. The SAE linear token bus, SAE token ring and the conventional MIL-STD-1553B protocols have been analyzed using combined discrete-event and continuous-time simulation techniques. The impact of data latency on the dynamic performance of an advanced aircraft is illustrated by simulation of the closed loop DDFCS.
This well-respected work discusses the use of digital computers in the real-time control of dynamic systems. The emphasis is on the design of digital controls that achieve good dynamic response and small errors while using signals that are sampled in time and quantized in amplitude.
MATLAB statements and problems are thoroughly and carefully integrated throughout the book to offer readers a complete design picture. Many of the figures in the book were created by Matlab files, which are available to download at the link below for interested readers.
Asynchronous time-division multiplexed networks, used in Integrated Communication and Control Systems (ICCS), introduce time-varying and possibly stochastic delays in the feedback control loops. The objective of this on-going research is to develop a comprehensive methodology for the analysis and design of the above class of delayed control systems. In the first part of this two-part paper, we developed a discrete-time, finite-dimensional, time-varying model of the delayed control system; necessary and sufficient conditions for system stability have been established for periodically varying delays. This second part elucidates the significance of the above model relative to the system dynamic performance as well as addresses major criteria for and outlines alternative analytical approaches to ICCS design. Pertinent concepts are illustrated by simulation.
The adoption of integrated computer-based manufacturing and management
techniques by small, traditional engineering companies often represents
an unaffordable and high risk investment strategy in technology that is
often not well understood by its recipients. Paradoxically, the
opportunity for complete success in a small to medium-sized enterprise
(SME) is greater than in a large company which very often is incapable
of full integration due to the divisions and inertia implicit in a large
hierarchical organization. To derive full benefits from such an
investment the company must possess a meticulous understanding of its
market, fiscal environment, operations management, engineering and
technological skills, manufacturing facilities and product range. It
must adopt an appropriate implementation of CIM that does not debase
previous ad hoc investments in what are often termed
islands-of-automation or information technology. For success a
well-planned stepwise approach is vital. Reports on the approach adopted
by a small to medium-sized Scottish engineering company specializing in
the production of mechanical actuation systems. Over a three-year period
the company embarked on a low-cost, phased implementation of software
and hardware systems that exploit a database to integrate its design,
manufacturing the business operations. A major element in these systems
is the distributed Command, Communication and Control (C3) environment
which has transformed the effectiveness of operations. The company's
investments were based on a prudent assessment of its current and
planned product range, existing and planned manufacturing facilities,
the scale of its operations and business objectives.
Monitoring and control of machining systems has been shown to dramatically improve operation productivity and part quality; however, very little attention has been given to the coordination of multiple complex machining modules. The current practice is to design the module coordination and to debug the resulting computer code in an ad hoc manner. In this paper, the concept of supervisory machining control, in the context of machining module regulation, is presented. The structure of, and elements contained in, a supervisory controller are detailed, and a systematic design procedure for constructing these controllers is presented. The design procedure is utilized to construct a supervisory machining controller which is experimentally implemented in a face milling operation.
In this paper we introduce a novel control network protocol, Try-Once-Discard (TOD), for networked control systems (NCS), and provide, for the first time, an analytic proof of global exponential stability for both the new protocol and the commonly used statically scheduled access methods. Controllers are designed without regarding the presence of the network in the feedback loop, so consequently many controller design techniques may be employed. The performance of the new network protocol and the statically scheduled protocols are compared in simulations.
DIGITAL CONTROL OF DYNAMIC SYSTEMS By Gene F. Franklin, J. David Powell, and Michael Workman 3rd ed, 1998, Addison-Wesley, ISBN: 0-201-82054-4, acquired by Prentice-Hall, but they went out of print in 2006. Replaced by Ellis-Kagle Press: ISBN: 0-9791226-1-9 or ISBN13: 978-0-9791226-1-3 Ellis-Kagle Press was formed by Franklin and Powell in order to keep the book in print after 2006. However their book went out of print in 2021 and has been replaced by a PDF version which is available for download at: EllisKaglePress.com.
The current Ellis-Kagle Press eEdition-2 of the 3rd edition has all known errors corrected as of 2022 and EllisKaglePress.com has the link for downloading the associated Matlab files. If you have questions or suggestions, please send to: EllisKagle@gmail.com
We introduce a control network protocol, try-once-discard (TOD),
for networked control systems (NCS), and provide, for the first time, an
analytic proof of global exponential stability for both the new protocol
and the commonly used statically scheduled access methods. Controllers
are designed without regarding the presence of the network in the
feedback loop, so consequently many controller design techniques may be
employed. The performance of the new network protocol and the statically
scheduled protocols are compared in simulations
Many different network types have been promoted for use in control
systems. In this article, we compare three of them: the Ethernet bus,
with carrier sense multiple access with collision detection,
token-passing bus (e.g., ControlNet), and controller area network bus
(e.g., DeviceNet). We consider how each control network can be used as a
communication backbone for a networked control system connecting
sensors, actuators, and controllers. A detailed discussion of the medium
access control sublayer protocol for each network is provided. For each
protocol, we study the key parameters of the corresponding network when
used in a control situation, including network utilization, magnitude of
the expected time delay, and characteristics of time delays. Simulation
results are presented for several different scenarios, and the
advantages and disadvantages of each network are summarized
In this paper, we consider the combination of two di#erent types of auxiliary control modules applied to a two-axis machining system. It is known that a cross-coupling control algorithm can reduce the contour error of a two-axis system, and that friction compensation can reduce positioning errors in machining systems. Here, we address the question of how the overall performance of the system is a#ected when both types of control are applied at the same time. Preliminary results indicate that the performance improvement is multiplicative. That is, if the error is reduced by a factor of P cc for cross-coupling control, by a factor of Pfc for friction compensation, and by a factor of P cc,fc when both are applied simultaneously, then P cc,fc # Pcc Pfc. Simulation and experimental results are presented. INTRODUCTION In a conventional multi-axis machine tool system, each axis is controlled by a separate servo loop, which is designed to minimize the axial position error (Koren, 1983). E...
In this paper, we consider the combination of two different types of auxiliary control modules applied to a two-axis machining system. It is known that a cross-coupling control algorithm can reduce the contour error of a two-axis system, and that friction compensation can reduce positioning errors in machining systems. Here, we address the question of how the overall performance of the system is affected when both types of control are applied at the same time. Preliminary results indicate that the performance improvement is multiplicative. That is, if the error is reduced by a factor of Pcc for cross-coupling control, by a factor of Pfc for friction compensation, and by a factor of Pcc,fc when both are applied simultaneously, then Pcc,fc ≈ Pcc · Pfc. Simulation and experimental results are presented.
Integral control of large-scale systems implies application of control and information exchange via communication networks in which random delays may exist. The design of such systems rely on conservative sufficient stability tests for systems with random, time-varying delays. In this report, necessary and sufficient conditions are found for zero-state mean-square exponential stability of the considered class of control systems. Numerical tests for zero-state stability are outlined and illustrated by a simple example. Finally, the results are also demonstrated on specific hardware, multiprocessor real-time control network which has been recently developed.
An abstract is not available.
Fieldbus communication networks aim at the interconnection of sensors, actuators and controllers within process control applications. Therefore, they constitute the basis upon which real-time distributed computer-controlled systems can be implemented. P-NET is a fieldbus industrial communication standard, which uses a virtual token passing medium access control mechanism. In this paper we establish pre--run-time schedulability conditions for supporting real-time traffic with P-NET networks. Essentially we provide formulae to evaluate the upper bound end-to-end communication delay of P-NET messages. Using this upper bound, a feasibility test is provided to check the timeliness requirements for accessing remote process variables. This paper also shows how P-NET network segmentation can significantly reduce the end-to-end communication delay of messages with stringent timing requirements.
We discuss modeling and analysis of real-time control systems
subject to random time delays in the communication network. A new method
for analysis of given control schemes is presented. The state of the
network is modeled by a Markov chain and Lyapunov equations for the
expected LQG performance are presented. An example that illustrates the
results is given
This paper analyzes the effect of control architectures and communication networks on a manufacturing system's performance in terms of part precision and productivity; the network bandwidth requirement for a distributed control system is also included. The objective is to design the system such that the control and communications (both hardware and software) would not be the limiting factors in system performance. For simplicity we analyze the performance of a machining center control system. The base-line for comparison is a conventional computerized numerical controlled (CNC) with discrete event management/adaptive system.
This paper presents statistical analysis of delays in Integrated Communication and Control System (ICCS) networks that are based on asynchronous time-division multiplexing. The models are obtained in closed form for analyzing control systems with randomly varying delays. The results of this research are applicable to ICCS design for complex dynamical processes like advanced aircraft and spacecraft, autonomous manufacturing plants, and chemical and processing plants.
Ethernet continues to be one of the most popular LAN technologies. Due to the low price and robustness resulting from its wide acceptance and deployment, there has been an attempt to build Ethernet-based real-time control networks for manufacturing automation. However, it is difficult to build a real-time control network using the standard UDP or TCP/IP and Ethernet, because the Ethernet MAC protocol, the 1-persistent CSMA/CD protocol has unpredictable delay characteristics. When both real-time (RT) and non-real-time packets are transported over an ordinary Ethernet, RT packets from a node may experience a large delay due to: contention with non-RT packets in the originating node; and collision with RT and non-RT packets from the other nodes. To resolve this problem, we designed, implemented, and evaluated adaptive traffic smoothing. Specifically, a traffic smoother is installed between the UDP or TCP/IP layer and the Ethernet MAC layer, and works as an interface between them. The traffic smoother first gives RT packets priority over non-RT packets in order to eliminate contention within each local node. Second, it smooths a non-RT stream so as to reduce collision with RT packets from the other nodes. This traffic smoothing can dramatically decrease the packet-collision ratio on the network
CAN and PROFIBUS-DP are two very popular fieldbuses, which can
also be profitably also as control networks for distributed systems
where a controller is connected to a number of simple devices. The use
of CAN and PROFIBUS-DP as a communication support for event driven
systems is considered and their performances are evaluated from this
point of view. Only those aspects of these two networks which are
relevant in the scenario of event driven automation systems are taken
into account and formulas are derived to evaluate the responsiveness and
throughput which can be achieved in a number of situations. The results
obtained with our analysis show that even though the performances of the
two kinds of fieldbuses are very similar, it is convenient to use CAN in
small size systems while PROFIBUS-DP is more suited to poll based
applications
One of the fastest growing market segments among control and
automation technologies is the introduction and development of control
network systems. Although fieldbus systems have been used for several
years in industrial automation, control network systems opened the
market to different application areas, such as home and building
automation. The current activities in both fieldbus and control network
systems are causing confusion amongst companies and consumers using
control equipment. The article shows the differences between fieldbus
and control network systems, considers the different application areas,
reviews the most popular control systems, and provides useful contact
addresses for further inquiries
Integrated communication and control systems (ICCS) consist of
several distributed control processes which share a network medium.
Performance of several feedback control loops in the ICCS is subject to
the network-induced delays from sensor to controller and from controller
to actuator. The network-induced delays are directly dependent upon the
data sampling times of the control components which share a network
medium. In this study, a scheduling algorithm of determining data
sampling times is developed using the window concept, where the sampled
data from the control components in the ICCS share a limited number of
windows, so that the performance requirement of each control loop is
satisfied as well as the utilization of network resources is
considerably increased. The scheduling algorithm is verified by
discrete-event/continuous-time simulation model of an example of ICCS
The introduction of field buses to replace the traditional wiring of sensors and actuator to programmable controllers is discussed. After a brief summary of the advantages presented by field buses, the features of the interconnected devices, and the requirements that these networks must fulfill are examined. A description is given of PHOEBUS, a prototype field bus developed for a machine tool. This implementation is compared to other proposals. An architecture based on the OSI reference model is presented with elements of services and protocols that match the requirements for a machine tool field bus. A series of problems that are introduced when several pieces of automation equipment share the same field bus is considered.< >
Control networks move small packets of data to a large set of nodes, so as to integrate and automate everything from home appliances to entire factories. This is due to the use of embedded microprocessors. The author discusses the control net architecture, network topology and the fast response of the network.< >
Contents Acknowledgments .......................... 7 1. Introduction ............................ 8 Outline of the Thesis and Publications .............. 9 2. Problem Formulation ....................... 13 2.1 Distributed Control ..................... 13 2.2 Networks ........................... 18 2.3 Clock Synchronization .................... 20 2.4 RelatedWork......................... 23 3. Modeling of Network Delays .................. 29 3.1 Network Modeled as Constant Delay ........... 29 3.2 Network Modeled as Delays Being Independent ..... 30 3.3 Network Modeled Using Markov Chain .......... 31 3.4 SamplingofSystemswithNetworkDelays........ 31 4. Experimental Delay Measurements .............. 35 4.1 CAN .............................. 35 4.2 EthernetNetwork ...................... 50 4.3 Summary ........................... 54 5. Analysis and Control with Independent Delays ...... 56 5.1 Cl
Networked Control Systems Toolkit: A Simulation Package for Analysis and Design of Control Systems With Network Communications
- F.-L Lian
- J R Moyne
- D M Tilbury
F.-L. Lian, J. R. Moyne, and D. M. Tilbury, " Networked Control Sys-tems Toolkit: A Simulation Package for Analysis and Design of Control Systems With Network Communications, ", Tech. Rep. UM-ME-01-04, 2001.
- G F Franklin
- J D Powell
- A Emami-Naeini
G. F. Franklin, J. D. Powell, and A. Emami-Naeini, Feedback Control of
Dynamic Systems, 3rd ed. Reading, MA: Addison-Wesley, 1994.