Crewless ships instead of the romantic notion of a sailor? Initiatives for autonomous ships are driving this development. However, the path from the engine room, which can currently operate for a maximum of 24 hours without direct intervention, to an autonomous ship, which should be able to operate for up to six weeks without human intervention, is still long. WAGO’s redundancy concept for controllers is shortening this path and offers a solution for compensating for faults occurring in the automation systems and for ensuring the continued operation of technical systems.
The greatest challenge over the course of increased automation in shipping remains establishing onboard systems that are so reliable that outside interventions are unnecessary. This can be achieved by using a larger proportion of standardized components on board, while maintaining high availability of security relevant systems through redundancy. In order to guarantee the automation systems’ reliability, the voltage supply and the communication medium (e.g. ETHERNET), in addition to the PLC, must satisfy the technical system’s uptime requirements. WAGO provides a simple and economic solution for its maritime customers that uses an application-based redundancy concept for controllers.
WAGO’s e!COCKPIT engineering software tool is used as the programming environment for the controllers. The multi-node programming environment can easily transmit the PLC program to both PLCs. In order to use the application-based controller redundancy, a software library with the necessary synchronization functions must be integrated into the master PLCs. The library offers the potential to redundantly link subnodes using a dual-LAN. The subnodes, also known as smart couplers, do not have to be programmed; they can be simply booted from an SD card and then configured using an integrated webserver. The analog input/output modules and digital input/output modules are detected automatically by the smart coupler; process mapping is likewise automatically made available to the higher-level Master PLC. The master PLC can communicate with higher-level SCADA systems via the Modbus-TCP protocol. The redundant connection is carried out over two separate networks.
The solution design corresponds to an SPOF-tolerant system (single point of failure), which means that any occurring fault – like a voltage supply failure, the LAN connection, switches, or controller – can always be compensated for. Doubling the ETHERNET topology and the redundant message transmissions enable instantaneous switching during a network fault. Typical switching times after the failure of a PLC are easily below the requirements of DNV GL when used in traditional alarm and monitoring systems.
Text: Norman Suedekum,
Photo: WAGO