Wednesday, November 10, 2010

CAMD Ring Control System Upgrades

In addition to the Linac control system currently in progress, CAMD has also upgraded several ring systems to PLC based systems. These include vacuum interlocks and monitoring, TSPs, and other digital control functions.

CAMD has recently upgraded its vacuum system. There are significantly more ion pump controllers and vacuum gauge controllers than in the older system. The decision was made to replace the old control system with a combination EBC/CPU PLC system. The system no consists of one identical rack per quadrant, each containing an EBC based PLC. These PLCs monitor the readbacks for each Ion pump controller and vacuum gauge controller in the quadrant. Contact closures from the vacuum gauge controllers are sent to a CPU based PLC, which contain the Ladder logic and digital outputs necessary to close various ring valves in cases of high pressure conditions.

The initial TSP system for the CAMD storage ring contained only one sublimation controller, had no indication of the success or failure of the firing operation, and provided no indication as to how much current was applied to each filament. An upgrade was planned to provide one sublimation controller per quadrant, routing its output via a PLC controlled multiplexer, and to provide a graphical user interface with logging capability for the firing operation.

When the CAMD control system upgrade project began in early 1997, CAMD was faced with the task of integrating two separate control systems, with no reliable communications method between the two. Although CAMD’s LINAC and storage ring were both procured from Maxwell Laboratories via a single, fixed process contact, early in the design phase the Linac was subcontracted to CGR-Mev.

At the end of commissioning, the ring’s control system was a VAX/VMS based system running Vista Control VSystem Software, utilizing CAMAC, GPIB, RS232, and Allen-Bradley remote I/O communications. The Linac control system, however, was a VME/OS/9 system using custom I/O cards. While Maxwell and CAMD had specified TCP/IP access to the control system computer, subsystem acceptance tests had shown that this type of communications was not possible. If the system was “ping”ed via TCP/IP, the watchdog timers expired, and the software interlocks shutdown the Linac.

The first control system to be upgraded was the storage ring control system. Initially, the VAX was replaced with a PC/Linux based system, preserving all existing hardware interfaces. Later phases of development were focused in two areas. The first was enhancing the controls capability, including adding additional control channels for a superconducting wiggler and additional corrector magnets, and increasing logging and operator automation. The second area was reducing the dependence on CAMAC and proprietary Allen Bradley protocols, and allowing remote data acquisition.

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