Jan Endresen

Unplugged but connected [Design and implementation of a truly wireless real-time sensor/actuator interface]

A truly wireless S/A interface with wireless power and wireless communication for real-time factory operation has been presented. WISA uses IEEE 802.15.1 radio transceivers, but adds an optimized TDMA protocol to support a high number (120) of S/As per BS as well as short cycle times (2,048 μs).

Design and implementation of a real-time wireless sensor/actuator communication system

For industrial automation applications using production machines and robotic installations, truly wireless systems offer advantages in terms of cost and flexibility. Requirements on power supply and real time communication for such applications are highly demanding, and cannot be satisfied with todays off-the-shelf systems. A novel factory communication system, called WISA (wireless interface for sensors and actuators), has thus been developed which provides both wireless communication and wireless power supply. The power supply is based on magnetic coupling while real time wireless communication uses a new TDMA protocol combined with frequency hopping. The TDMA protocol uses optimized parameters for reliable and low delay transmission for a high number of active nodes. The frequency hopping sequences are optimized to mitigate effects of multi-path propagation, interference from other systems operating in the 2.4 GHz ISM band, and self-interference. The new design re-uses existing RF transceivers. The paper explains design concepts of the WISA communication system, and describes practical experience gained with its deployment in industrial environments

The Future of Train Signaling

Producing the source code for a railway interlocking system based on the description of a station has traditionally been a multistage manual process. We show how this process can be automated and made less error-prone by introducing model-driven development (MDD). This paper addresses the experience of developing a Domain Specific Language (DSL) to describe railway stations, Train Control Language (TCL), and tools to support this language. In the railroad domain where there are extreme safety requirements, it is essential to show that consistency and completeness can be assured. We address how the model is used to generate several different representations for different purposes. We look at advantages and challenges with our approach, and we discuss improvements to existing technologies to support our case better.

A Technique for Agile and Automatic Interaction Testing for Product Lines

Product line developers must ensure that existing and new features work in all products. Adding to or changing a product line might break some of its features. In this paper, we present a technique for automatic and agile interaction testing for product lines. The technique enables developers to know if features work together with other features in a product line, and it blends well into a process of continuous integration. The technique is evaluated with two industrial applications, testing a product line of safety devices and the Eclipse IDEs. The first case shows how existing test suites are applied to the products of a 2-wise covering array to identify two interaction faults. The second case shows how over 400,000 test executions are performed on the products of a 2-wise covering array using over 40,000 existing automatic tests to identify potential interactions faults.

Formalizing Train Control Language: Automating Analysis of Train Stations

The Train Control Language (TCL) is a domain-specific language that allows automation of the production of interlocking source code. From a graphical editor a model of a train station is created. This model can then be transformed to other representations, e.g. an interlocking table and functional blocks, keeping the representations internally consistent. Formal methods are mathematical techniques for precisely expressing a system, contributing to the reliability and robustness of the system through analysis. Traditionally, applying formal methods involves a high cost. This paper presents a formalization of TCL, including its behavior expressed in the constraint solving language Alloy. We show how analysis of station models can be performed automatically. Analysis, such as simulation of a station, searching for dangerous train movements and deadlocks, is used to illustrate the approach.

Train Control Language – Teaching Computers Interlocking

This paper describes how computer specialists are rarely trained in the world of tracks and trains, while signaling experts are rarely computer specialists. This paper is about bridging the gap between trains and computers with a specially designed language that enables the signaling experts to create consistent train interlocking systems. The language is supported by tailored tools created with open source technology on the development platform Eclipse. From the formal definition of the language in the form of a metamodel, a graphical editor is generated. The systems created with that graphic editor are then transformed for several purposes that are internally consistent. The editor makes sure that the systems conform to the language, and the language makes sure that the systems conform to the way interlockings are designed. The transformations then produce interlocking tables and even actual code automatically from the graphically created model.

On the significance of fault tree analysis in practice

With increasing system complexity and extensive use of computerized control of industrial processes and plants, it is essential to have a systematic approach for identifying failures that can expose people and environment for unacceptable risks. With focus on a drive system used to control a linear motor, the fault tree analysis method is utilized to reveal design weaknesses and to find mitigations that can improve the system safety characteristics. Starting with a set of top level hazards, elements with high risk impact are identified, and appropriate mitigations are suggested.

A Pragmatic Approach on Combined Safety and Security Risk Analysis

In this paper we discuss the issue of balancing safety and security requirements in industrial automation and control systems. This is an area that requires careful attention. We propose a methodology/framework for addressing both safety and security for safety critical systems in industrial automation and control systems. Our concern is analyzing those vulnerabilities that when a threat agent is enacted on them, result in hazards such as damage to equipment or property or hazards resulting in personal injury or death.

Maximizing diversity in CPUs: Using GPUs as coprocessors to achieve safety integrity

Modern System-on-Chip (SOC) architectures offer much for a relatively small price, but often industrial machine builders only use a fraction of the functionality. Their main interest is the performance boost by using multiple cores. For safety devices, the on-chip redundancy is beneficially to achieve higher reliability, but since most platforms are homogenous, there is a need to get systematic and common cause failures under control. Graphics Processing Units (GPU`s) are more and more available in modern SOCs, but their utilization in industrial products is still marginal. This paper proposes a concept how GPUs can improve the overall safety integrity with additional diversity in hardware and software.