FIBRE-OPTIC, MULTI-ACCESS NETWORK FOR INTRACAR AND MANUFACTURING ENVIRONMENTS

The Controller Area Network (CAN) is a CSMA-CD protocol with priority access and was designed for Intra Car Communication. The purpose of this network is to connect the various functions within a vehicle and allow communication between them using only one serial data line instead of conventional cable trees. Interference from electromagnetic discharges, for example in the engine compartment, leads to occasional transient, or soft, errors. Recovery from soft errors is provided for by the CAN protocol. In case of hard faults, for instance a short circuit between the transmission line and the board power supply, hardware components can be destroyed and recovery is not possible. Whereas other work has attempted to solve the problem by sophisticated interfaces for solid media, this research focuses on how to use fibre optics for interconnection and therefore avoid both problems, electromagnetical interference and hard faults. From seven investigated optical transmission structures the optical rmg was chosen for implementation. Since the CAN protocol was originally defined for working with a bus, using it over a ring requires a means of obtaining compatibility with a bus. This is achieved using interfacing hardware between access controller and optical ring. Two-way transmission around the ring is provided in order to increase the level of fault-tolerance. An additional feature of the interface is its ability to locate open failures on the ring and to isolate them by organizing detour paths within the redundant structure, without impairment of data transmission. Unlike other approaches, this fault-tolerant optical double ring does not require additional optical components. Further improvement of the system performance is gained by modification of the access mechanism. When moving from a globally to a locally operating access mechanism, both the bit­rate and the physical size of the network can be more than 100 times larger than can be supported by the un-modified CAN protocol. This modification results in a new protocol which satisfies most of the requirements for modern industrial fieldbuses. In order to obtain the same hierarchical independence of the priority access scheme as obtained with the un-modified CAN protocol, the new protocol should work over an unidirectional bus. One optional unidirectional bus structure is the folded bus topology. When the upstream and the downstream ends of the folded bus are connected, the network again forms a double ring. This is done to provide redundancy for the modified protocol and to allow for media disconnection failures. Thus, the folded bus must be logically configured within the physical double ring during cold- tart. This is done by means of a distributed configuration mechanism.

Name dc:type.qualificationname

PhD

Level dc:type.qualificationlevel

Doctoral

Grantor dc:publisher.institution

De Montfort University

Year dc:date.issued

1994

Author dc:creator

• Mores, Robert

Licence

• https://dora.dmu.ac.uk/bitstreams/3ce0c1ea-ee1d-4760-837c-19afe9744770/download