R. Ors

New challenges in wireless sensor networks: fault tolerance and real time

The wireless communications field is in continuous growth and revolution. The current trend toward the use of distributed wireless systems is due to these systems have demonstrated to be a good option due to its flexibility and power. In this line, nowadays there is an enormous demand of wireless connectivity for any industrial control applications, included critical systems. In this paper we discuss the possibilities and necessary developments to set up wireless communication for industrial applications in general and critical systems in particular. Furthermore, an abstract definition of a layered architecture for the development of intelligent and distributed control systems based on wireless sensor networks is proposed

Industrial applications of wireless networks: a bridge crane distributed control system based on Bluetooth

This paper shows the possibility to use Bluetooth for wireless short range communication in an industrial environment. In this line a distributed control system based on Bluetooth has been proposed for a bridge crane system. Its configuration is mainly based on the use of distributed nodes connected by means of Bluetooth. Traditionally many types of devices have been delivered as mechanical devices and more or less all or the intelligence and control has been added. Nowadays there is a growing trend towards a higher level of built-in intelligence in the devices, constituting the intelligent nodes. This type of systems allows the implementation of highly flexible control systems capable of adapting themselves to different situations. With the introduction of Bluetooth, another dimension is aggregated, the possibility to wirelessly connect to the devices. The technology makes it possible to easily access the built-in user interfaces through portable devices but also to access the device data without the need for a physical connection. Bluetooth is one of the most promising personal wireless network technologies. The automation industry is showing interest in using Bluetooth for many industrial applications.

Distributed and mobile systems based on wireless networks: definition of a generic control architecture

The tendency toward the use of distributed systems is due to these systems have demonstrated to be a good option for the industrial control systems implementation, because of their flexibility and power, which can be increased with the application of artificial intelligence techniques. In this line, our research group has developed several distributed systems applied to chemical analysis and industrial automation. For these implementations the CAN network was used. Nowadays there is a market for technical tasks like distributed control, monitoring or data acquisition where there is a need for wireless connectivity. Thus, in this paper we want to discuss possibilities and necessary developments to set up wireless communication for industrial applications. Also, an abstract definition of a new layered architecture for the implementation of intelligent and distributed systems interconnected by means of wireless networks is proposed. Several techniques of discrete control may be used, from Petri nets to an expert system based on rule nets, while continuous control loops may be implemented by means of from traditional PID devices to distributed neural network approaches. Finally, for the communication layer implementation, a wireless network such as Bluetooth or ZigBee could be used.

An advanced and distributed control architecture based on intelligent agents and neural networks

A new layered architecture for the implementation of intelligent distributed control systems is proposed. The proposed architecture distinguishes four layers in a distributed control system. Upper layer consists of a digital control layer, where high level decisions are taken. This level is implemented by means of intelligent agents that carry out the discrete control functions, system supervision as well as diagnosis and fault tolerance. Third layer deals with numeric values, performs analog operations and implement analog control loops. It is also in carry of the conversion from numerical variables values to evaluated expressions. This layer has been implemented by means of neural networks. Communications network appears in the second layer. Selected network was CAN (controller area network) because of its particular characteristics. Finally, every node should implement a hardware interface with the process to control. Some interesting characteristics provided by this architecture are its low-cost implementation, easy distribution through a communication network, distributed execution in virtual generic nodes-with no hardware dependency-, bounded response time and fault tolerance mechanisms

A comparative analysis of the reliability of simple and two-level checkpointing techniques in two different distributed industrial control system architectures

In Distributed industrial control systems it is necessary to guarantee certain reliability level. In this sense, Checkpointing and Rollback techniques offer interesting possibilities to achieve fault tolerance without appreciable cost and complexity increment. Several Checkpointing techniques have been proposed. Most of them suppose the presence of stable storage in the system. But distributed industrial control systems usually do not dispose of this kind of storage. So, another storage strategy has to be employed. If Checkpoints were locally stored (Simple Checkpointing), the system tolerates only transient faults. If Checkpoints were locally, at the same node, and, additionally, at another/s node/s of the system stored (Two-level Checkpointing), the system can recover from some permanent faults too. In this article the results of a study of the reliability of these two different Checkpoint storage strategies were presented in order to evaluate if the reliability increase of the Two-level method justifies its greater complexity. In order to accomplish this study, two distributed industrial control systems were presented. Each of them are based on a different node architecture which will have an important effect upon the results of the study.

A distributed control system for citric fruits conservation and maturation based on CAN and Internet networks

In citric fruits conservation and maturation systems it is very important to have precise information about parameters that indicate the citric fruit state. This information allows computing the appropriate control actions in order to achieve an optimum controlled citric fruit conservation and maturation. Last technological advances must be also used in this agriculture field to forget the rudimentary control systems that are being used at the present time. This paper describes a new distributed control system devoted to control citric fruits cold chambers that applies the last computer and electronics techniques. It is structured over different communication networks, making possible a remote pursuit and control in real-time over Internet networks and offers an improved features of flexibility and reliability. In each cold chamber, there are a strategically distributed set of sensors and actuators that are interconnected by means of a C.A.N network. In each cold chamber, one control node centralizes the chamber information and calculates the control actions. The control node information is also overturned on a backbone C.A.N network that interconnects all cold chambers with a personal computer. This computer is in charge of carrying out a second treatment and storage of the information and its diffusion to Internet. Finally, each user can be connected to his plant via an Internet connection or using a GPRS or WAP mobile telephone, to see the process evolution or to modify the parameters of each cold chamber.

A CAN Fieldbus Based Architecture for Distributed Control Systems Implementation

Abstract The application of distributed systems theory to the implementation of industrial control systems is one of the best options to develop simple, scalable and physically distributed control systems. Following this line, our group has proposed a new architecture based on Rule Nets (RN) as an HLP over CAN fieldbus for the implementation of Distributed Systems. This architecture has been applied to several control applications, obtaining excellent results. The most outstanding feature of the architecture was its simplicity in the control systems design, without any efficiency loss. New capabilities have been added to improve its features and develop new analysis tools, in order to increase its power and simplicity. In this work these new architecture features are presented.

Enabling ubiquitous wireless sensor networks: A new fault tolerant RF architecture with perpetual electrical power based on 802.15.4 and RFID

The wireless communications field is in continuous growth and revolution. The current trend toward the use of distributed wireless systems is due to these systems have demonstrated to be a good option due to its flexibility and power. In this line, nowadays there is an enormous demand of wireless connectivity for any industrial control applications, included critical systems. In this paper, we want to discuss possibilities and necessary developments to set up wireless communication for industrial applications in general and critical systems in particular. Furthermore, an abstract definition of a layered architecture for the development of intelligent and distributed control systems based on wireless sensor networks is proposed.

A New Web Interface for Distributed Control Systems: Application to the Chemical Monitoring of a Wort Fermentation Process

A new Web interface for rule net-based distributed control systems is proposed. It is applied to the monitoring of a chemical analysis system coupled with a wort fermentation process. A complete description of both the chemical and the informatics system is presented. This interface offers the possibility of accessing the process from any Internet-connected device (PC, PDA, etc.), using a standard browser as the only software required. The evolution of the results obtained in the FIA monitoring (and consequently of the process) can be analyzed by means of this interface; on the other hand, the process itself can be directly controlled through the modification of the different working parameters, even from a remote location.

A new distributed control system for conservation and maturation of bananas based on CAN and Internet networks

In the conservation and maturation systems of fruits it is very important to have faithful information about certain parameters that indicate the fruit state, and that allow to take the appropriate proofreaders actions in order to achieve an optimum controlled fruit maturation. In front of the rudimentary control systems that are being used at the present time, the Fault Tolerant Systems Group of the Polytechnic University of Valencia together with POLARIS TECHNOLOGY S.L company, have developed a new distributed control system based on CAN and Internet networks that allows a remote pursuit and control in real time of these processes. In each cold store, there are a strategically distributed set of sensors and actuators that are interconnected by means of a CAN network. One node centralizes the information, so that after its filtrate and storage is overturned on a backbone CAN network that interconnects all cold stores with a PC in charge of carrying out a second treatment and storage of the information and its diffusion to Internet. This system is completely operative and it has been already installed in different companies of several countries, obtaining very interesting results.