Using servers to enhance control system capability

Many traditional control systems include a distributed collection of front end machines to control hardware. Back end tools are used to view, modify and record the signals generated by these front end machines. Software servers, which are a middleware layer between the front and back ends, can improve a control system in several ways. Servers can enable on-line processing of raw data, and consolidation of functionality. In many cases, data retrieved from the front end must be processed in order to convert the raw data into useful information. These calculations are often redundantly performed by different programs, frequently offline. Servers can monitor the raw data and rapidly perform calculations, producing new signals which can be treated like any other control system signal, and can be used by any back end application. Algorithms can be incorporated to actively modify signal values in the control system based upon changes of other signals, essentially producing feedback in a control system. Servers thus increase the flexibility of a control system. Lastly, servers running on inexpensive UNIX workstations can relay or cache frequently needed information, reducing the load on front end hardware by functioning as concentrators. Rather than many back end tools connecting directly to the front end machines, increasing the work load of these machines, they instead connect to the server. Servers like those discussed above have been used successfully at the Thomas Jefferson National Accelerator Facility to provide functionality such as beam steering, fault monitoring, storage of machine parameters, and on-line data processing. The authors discuss the potential uses of such servers, and share the results of work performed to date