Method for fault-tolerant communication under strictly real-time conditions

A method for a reliable and fault-tolerant transmission of information with strictly real-time requirements in a local network, using an active fault detection and notification mechanism on the basis of a double bus architecture with redundant bus systems, which comprises:

• using a controller area network (CAN) transmission protocol on a double bus systems, by:
• a) transmitting all process data on a bus of one bus system as a process bus during fault-free operation, and transmitting status information of components and other information on a bus of another bus system during fault-free operation;
• b) notifying all network subscribers (network nodes) of faults with each bus serving as a watchdog bus, in the case of a fault in the other bus;
• b1) triggering a switch-over of all of the network nodes to the other bus system and continuing the transmission of the process data on the fault-free bus, upon the notification of faults in the case of a process bus fault;
• and
• b1.1) carrying out the switch-over in the case of a process bus fault, by;
• b1.1.1) setting fault latencies between the detection of a fault and a possible switch-over in most cases of faults so short that no loss of messages occurs;
• b1.1.2) setting a fault coverage value;
• and
• b1.1.3) restoring a consistent system state in the case of possible losses, falsifications or duplications of messages with recovery mechanisms;
• b2) triggering no switch-over upon a notification of faults in the case of a fault in the bus which is not the process bus;
• c) providing all of the network nodes with two complete bus connections including a communication CPU, a communication controller and a transceiver;
• c1) each communication CPU function monitoring another connection of its node and monitoring its connection component as a watchdog processor;
• and
• c2) a communication CPU initiating a transmission of a fault message through its bus, after a detection of a fault in another connection of its node.