| WP 5 Safety in Automation Systems | ||||||||||||||||||||||||||
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The objective of this Work Package has been the definition and implementation of mechanisms to make safe data transfer over wired and wireless networks in industrial environments possible, especially over heterogeneous networks.
To specify safety requirements for transmission systems it has been essential to carry out an analysis of the safety functions which have to be performed by a control and transmission system in the machine or plant. The safety function of a network system usually is only a part of the entire safety functions. A programmable electronic system normally performs the processing of the safety relevant data that it gets from inputs and distributes to outputs. In a network system the input and output information are not directly connected to the control systems, but the network devices and also the controlling devices are distributed in the field. Therefore a network system for the transmission of safety relevant messages recommends techniques and measures for controlling all possible failures in the transmission process. It has been in the scope of this work package to specify the functional and safety requirements of parts that are involved in performing a safety function of a machine. The functional and safety requirements of the network nodes have to be described completely. The transmission system itself has to be modelled and a formal verification has to be done. A network system usually consists of processing units - the sources and sinks of information - as well as a transmission system that is made up of a transmission medium (e.g. electrical lines, fibre optical lines, etc.) and the interface between message source/sink and network electronics (protocol ASICs, transceivers, transmission stacks etc.). Therefore, several structure models have to be considered which differ concerning their error tolerance. One of them has been selected in this Work Package. Achievements and Results The work package has been structured in the following tasks:
The scope of the work package has been defined within the first task. It was agreed to focus on the functional safe communication over the heterogeneous network, not on the implementation of the overall safety function. The evaluation phase gave information about the existing technologies; none of them is useful for heterogonous communication without extensions. During the requirement specification the team formulated all known requirements. In this phase the team already came to the conclusion that the specification of a new safety communication layer will exceed the available time frame and resources. Therefore the team in the design phase checked which of the investigated technologies fulfills most of the requirements and how they need to be extended to work in heterogeneous networks environments. The architectural design was made in close contact with the TechPCC during the prototyping phase. The technical solution considers PROFISafe as communication layer, which is transported via an OpenVPN tunnel through a heterogeneous network. The prototype has been implemented and tested. Tests were made with UMTS and DSL connections.
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