SIMOTION & SINAMICS: Bumpless Media Redundancy with PROFINET IRT (MRPD)
To prevent failures (cable or device defect) in an automation system, the MRPD (Media Redundancy for Planned Duplication) functionality is available as of SIMOTION V4.3.
MRPD is a procedure for the bumpless media redundancy with PROFINET IRT. This functionality assumes that the part of the system to be protected against failures should be arranged in a ring topology.
The bumplessness is ensured by the provider (IO controller) sending the cyclic data in both directions in the ring with the consumers (IO devices) then receiving the data twice. The first received message frame is evaluated by the consumer; the second message frame is discarded.
If the ring is now interrupted at one location (e.g. through the failure of a ring node), the receiving of the cyclic data via the uninterrupted side of the ring is still guaranteed.
In this application example, the MRPD (Media Redundancy for Planned Duplication) functionality is displayed via PROFINET IRT.
The SIMOTION controller, the SCALANCE switch and the SINAMICS drive are arranged in a ring and connected with each other.
The SCALANCE switch acts as redundancy manager; the SIMOTION controller and the SINAMICS drive act as redundancy clients.
The SIMOTION controller sends its cyclical data (at setpoint speed) over both directions of the ring to the SINAMICS drive. It evaluates the first received message frame; the second received message frame is discarded.
If the ring is now interrupted somewhere, the drive continues to receive at the setpoint speed of the SIMOTION controller over the second connection that is still intact. If the connection is restored, message frames are sent again to the drive over both directions of the ring.
This mechanism ensures a bumpless media redundancy, i.e. no reconfiguration time is required after opening or closing the ring.
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Sample project + sources
The functions and solutions described in this article confine themselves to the realization of the automation task predominantly. Please take into account furthermore that corresponding protective measures have to be taken up in the context of Industrial Security when connecting your equipment to other parts of the plant, the enterprise network or the Internet. Further information can be found under the Entry-ID 50203404.
V1.1, 03/2013, Revised edition, documentation and code