Psante De Ingenieria

Options of radio based industrial CAN communication
Lutz Rauchhaupt, ifak Magdeburg Mobile communication in industrial automation systems is an increasing field of interest. Radio based fieldbus extensions are investigated in several projects. Approaches for CAN are also known. Nevertheless, the known solutions are still far from becoming a standard. This paper provides an overview of thenecessary technical and economical preconditions of a radio based CAN standard. The standard can follow several objectives concerning the mobility, flexibility or network topology which are discussed. The technical problems of a radio based CAN standard are shown in this paper. Consequences for the level of specification as well as solutions which could be the basis of a future standard are alsointroduced. Introduction Technological developments open up new possibilities even in application fields which they were not developed for. The Controller Area Network (CAN), developed for car communication - used in industrial networks, is an excellent example of this. Today, radio technologies are in a state to be introduced into new fields of application, thus e.Êg. into industrial communication.However, the integration in applications and devices as well as the usage conditions follow special rules in industrial automation systems. First experiences show that modifications are necessary, since the radio technologies and standards are not made for the usage in industrial environments. The today known implementations of industrial radio systems solve special communication problems by adaptingselected radio solutions, but a common approach, covering a broad field of application, can not be seen. However, even if a specific radio solution for a communication task in an automation system may spare costs, the objective of a widely usable specification is suggested. The community of CAN in automation experienced the importance of standardised interfaces and behaviours with the CANApplication Layer specifications and their profiles. Especially for small and medium sized companies, standardisation is an important topic to save their investments. A common approach described in a specification document and ready for standardisation is necessary. Applications for different radio CAN solutions which can serve as a basis are known (/1/, /2/, /3/).

09-02

In this paper, theprerequisites and conditions for a common radio CAN approach are discussed. Several objectives are presented which have to be considered in a radio CAN standard. These objectives are discussed taking account of the current status of CAN and radio implementations. In the conclusion, suggestions for a first standardisation approach are made. Even if the first documents are specifications rather thanstandards, the term standard will be used in this paper. Another convention is that the term wireless is used as a synonym for radio in this paper. Other types of wireless communication such as infrared are out of the scope in this paper. Prerequisites and conditions for a radio CAN standardisation Before discussing standardisation details, the prerequisites and conditions for a radio CAN standard shallbe considered. Even if the interest in wireless communication in the automation is growing, the reasons, motivation and requirements are all very different. The most important requirement is the request for communication with mobile devices such as handheld or moving robots. Also options to obtain a greater flexibility or open up new application fields are possible reasons to look for a wirelesscommunication. Before starting specification activities, it is necessary to find interested parties who share a

common aim. Who could be interested in such an activity? No doubt that end users in any case would have advantages of a standardisation. On the other hand, end users do not normally participate in standardisation. Providers of radio technologies, such as chip manufacturers and radio...