Ivan Cibrario Bertolotti

Evaluation of Response Times in Industrial WLANs

The adoption of wireless communication technologies in industrial environments for supporting (soft) real-time applications heavily depends on the ability to grant bounded response times for messages, at least from a probabilistic point of view. This aspect is particularly important in factory automation systems, where response times are considered much more significant than other performance indices, such as throughput, that are usually considered in different application areas. The ever-increasing availability on the market of products and solutions based on the IEEE 802.11 standard and the introduction of the 802.11e amendment for enhancing the quality of service (QoS) and prioritizing traffic make this kind of communication technology interesting also for adoption in (loosely coupled) distributed control systems. This paper reports on some experimental measures and the related analysis that have been carried out on real 802.11g/e networks for better understanding the statistical distribution of response times and can be of help in characterizing these solutions when used to support noncritical real-time traffic.

Evaluation of EtherCAT Distributed Clock Performance

EtherCAT is a real-time Ethernet protocol conceived explicitly for industrial applications. It is characterized by high communication efficiency, which permits control loops to be closed with short cycle times, and is provided with a suitable mechanism, known as distributed clock (DC), that enables synchronized operations to take place across the controlled system. These features can be profitably adopted, for instance, to support motion control applications. In this paper, the performance of the DC mechanism is evaluated by means of a thorough campaign of experimental measurements carried out on a real network setup. A number of factors have been taken into account that can affect accuracy and precision, and their effects studied in depth.

Performance of a Real-Time EtherCAT Master Under Linux

The adoption of open-source operating systems for the execution of real-time applications is gaining popularity, even in the networked control systems domain, due to cost and flexibility reasons. However, as opposed to their commercial counterparts, the actual performance level to be expected from them is still little known and may often depend on the kind of real-time extension being used, its configuration, and the overall software load of the system, including best-effort components. In this paper, an open-source EtherCAT master supported by a popular real-time extension for Linux, the RT Patch, is thoroughly evaluated with long-term measurements, which build confidence on the suitability of the proposed approach for real-world applications. Special attention is devoted to the unexpected, adverse effect that some best-effort components, for instance, graphics applications, may have on the overall real-time characteristics of the system. For reference, the proposed approach is also compared with RTAI, a more traditional and well-known real-time extension for Linux already in use for demanding applications.

Detecting Chains of Vulnerabilities in Industrial Networks

In modern factories, personal computers are starting to replace traditional programmable logic controllers, due to cost and flexibility reasons, and also because their operating systems now support programming environments even suitable for demanding real-time applications. These characteristics, as well as the ready availability of many software packages covering any kind of needs, have made the introduction of PC-based devices at the factory field level especially attractive. However, this approach has a profound influence on the extent of threats that a factory computing infrastructure shall be prepared to deal with. In fact, industrial personal computers share the same kinds of vulnerabilities with their office automation counterparts. Then, their introduction increases the risk of cyber-attacks. As the complexity of the network grows, the problem rapidly becomes hard to tackle by hand, due to the subtle and unforeseen interactions that may occur among apparently unrelated vulnerabilities, thus bearing the focus on the full automation of the analysis. Going into this direction, this paper presents a software tool that, given an accurate and machine-readable description of vulnerabilities, detects whether or not they are of concern and evaluates consequences in the context of a factory network.

On the accuracy of the distributed clock mechanism in EtherCAT

EtherCAT is a network protocol conceived for the use in factory automation environments, which relies on real-time Ethernet technology and is characterized by very high efficiency.

Industrial applications of IEEE 802.11e WLANs

Nowadays, wireless communication technologies are being employed in an ever increasing number of different application areas, including industrial environments. Unfortunately, because of several reasons, among which their random access technique, they are not usually considered suitable for connecting devices at the field level. In this paper, the performance that can be achieved by QoS-enabled WLANs (e.g., IEEE 802.11e networks) to support communication in industrial environments is analysed in depth. In particular, it is shown that they can be profitably adopted even at the shop-floor, provided that there are not critical safety requirements or tight timing constraints. Despite the lower determinism and reliability, the resulting performance resembles closely that achievable with fieldbuses.

Performance evaluation of an EtherCAT master using Linux and the RT Patch

This paper has the twofold goal of investigating the real-time performance of an EtherCAT master entirely built from open-source components (using Linux and the RT Patch at the operating system level) and assess its ability to support concurrent best-effort tasks without compromising the real-time ones, depending on kernel configuration. This is especially important for the successful adoption of the proposed approach in real-world applications. A hardware-based data acquisition system enables measurements to be taken for long periods of time, and with high resolution and precision. At the same time, this method guarantees that the measurement process does not influence the behavior of the system under test in any way.

Experimental evaluation of the Linux RT Patch for real-time applications

The possibility of using Linux as underlying operating system for real-time applications has received considerable attention by industry due to several definite advantages, such as the lack of royalties and the availability of rich and programmer-friendly software development frameworks. In addition, the real-time capabilities of the Linux kernel have recently been enhanced considerably through the development of the Linux RT Patch. This paper evaluates the real-time characteristics of the Linux kernel with the RT Patch installed, in order to help the designer understand what sort of real-time performance is to be expected, and decide whether it is adequate or not for a given class of applications.

A twofold model for the analysis of access control policies in industrial networked systems

Requirements concerning the specification and correct implementation of access control policies have become more and more popular in industrial networked systems during the last years. Unfortunately, the peculiar characteristics of industrial systems often prevent the designer from taking full advantage of technologies and techniques already developed and profitably employed in other application areas. In particular, the unavailability and/or impossibility of adopting hardware (h/w) and software (s/w) mechanisms able to automatically enforce the policies defined at a high level of abstraction, often results in checking the correctness of policy implementation in the real system manually. The first step towards carrying out this cumbersome task in an automated way is the development of a model able to capture both the high level policy specification as well as the details and low-level mechanisms characterizing the actual system implementation. This paper introduces a twofold model for the description of access control policies in industrial environments aimed at coping with this requirement and which can be profitably adopted in several kinds of automated analysis. A model to describe access control policies in industrial networked systems.The model allows the high level description of access control policies in RBAC.The model allows the detailed description of the real system low level mechanisms.The model allows automated analysis of the correctness of policy implementation.

Performance comparison of mechanisms to reduce bit stuffing jitters in controller area networks

Bit stuffing in CAN is likely to cause jitters on message reception that, in specific cases where timing accuracy is relevant, may worsen the quality of the control algorithm noticeably. Several solutions have appeared in the past years that are aimed to tackle this issue, which are based on a suitable encoding of the payload of the message carried out in s/w by the transmitting node. In this paper, two efficient approaches are considered, namely XOR masking and 8B9B encoding, and their performance evaluated by means of both theoretical analysis and experimental campaigns. In particular, jitter reduction capability and encoding efficiency were taken into account and compared to the case when plain CAN is adopted.