UCOS Redundant Options

UCOS supports optional redundancy at every level of the architecture.

You can have a redundant network, redundant Operator Workstations, redundant controllers, redundant data servers, and even individual I/O points can be redundant.

Details

Redundant Operator Workstations

Normally, each Operator Workstation (OWS) in a UCOS system monitors and controls only a portion of the whole project. However, more than one Operator Workstation can monitor and control the same portion of the project. If your system includes a master Operator Workstation, you can duplicate that functionality on other Operator Workstations.

Those workstations can all be on the same LAN, or they can be widely dispersed geographically.

This allows remote workstations to securely take over monitoring and control if the primary location becomes inoperable.

Redundant Controllers and Data Servers

(Redundancy for Field Control Units (FCU), microFCUs, Field Data Servers (FDS), and SCADA Data Servers works in a similar manner. So this discussion will refer to all of these components as "controllers".)

There is no single point of failure in a UCOS system.

In a redundant UCOS configuration, either the primary or secondary controller can control the process independent of each other. When both controllers are online and functioning normally, both controllers receive inputs from the field I/O and scan the control logic independently. However, only the controller acting in the primary role writes outputs to the field I/O and updates data to the Operator Workstations.

When both FCUs are online, the primary FCU will synchronize its database with the secondary FCU every scan (on a dedicated LAN) to ensure the backup is in the proper state to take control should the primary FCU fail. Since the hardware is completely independent, a single point of failure will not adversely impact the process.

Control logic can monitor a "health" tag in the controllers and generate an alarm which can appears in the Alarm Viewer, can be logged onto an alarm or event printer, or can even be used to page maintenance personnel.

All display applications (graphic screens, command windows, group displays, trends, etc.) and reports (such as the Alarm Viewer Report Manager) obtain data from whichever controller is currently fulfilling the primary role.

Redundant LAN

UCOS supports single or redundant Ethernet and fiber optic LAN technologies.

On a redundant LAN, an Operator Workstation will communicate on what is configured to be the primary LAN. If for any reason the node suffers a communication failure, it will fail over to the secondary LAN and reconnect with all of the data points it needs.

Redundant I/O Points

Depending on the I/O subsystem that is selected, critical I/O points can be wired to different points on different I/O modules and based on the I/O level diagnostics, UCOS will read or write to the operable module should a hardware failure occur.

Larger Image (19K)

Configuring backup points in UCOS is very easy. A backup module is assigned to a primary module. Once the first assignment is made to a backup module, any points added to the associated primary module are automatically made to the backup module.

Redundant Data Historian

In a redundant data historian configuration, both nodes continuously receive data updates from the Field Control Units. The first node makes all entries into the historical database and the backup node buffers the data for a user-configurable time, so that data is not lost in the event of primary node failure.

If a problem occurs on the primary, the secondary takes over and writes all buffered data to the database to ensure no data is lost.