The CERN PS accelerator complex has been pro gressively converted to full computer controls without interrupting its full-time operation (more than 6000 hours per year with on average not more than 1% of the total down-time due to controls). The application soft ware amounts to 120 man-years and 45O*OOO instructions: it compares with other large software projects, also outside the accelerator world: e.g. Skylab's ground support software.1 This paper outlines the application software structure which takes into account technical requirements and constraints (resulting from the compl exity of the process and its operation) and economical and managerial ones. It presents the engineering and management techniques used to promote implementation, testing and commissioning within budget, manpower and time constraints and concludes with experience gained.
Current PS controls application software has a strong hierarchical structure of software modules which translate user-friendly commands into the intricacies of hardware devices. Starting from the most elementary hardware level, these are: (i) the "interface module" (IM), which hides the various CAMAC commands so as to provide a standard access to each type of CAMAC module ; (ii) the "equipment module" (EM) presents a simple standard software interface of each process equipment. There is one EM for each type of equipment and all process equipment is accessed through EMs via IMs; (iii) the "composite variable module" (CVM) provides control of abstract beam variables. It involves control of several and possibly different kinds of equipment. Setting a CVM results in appropriate setting of all relevant equipment through calls to their EMs.For the LEP Preinlector (LPI) a new generation of application software is being implemented based on the experiments with the current system and the technological evolution since its conception. The logical levels of IM, EM and CVM are kept, but their managerial and housekeeping functions are merged into a single module : the "General Module" (GM) .This paper represents the characteristics of the GM, its decomposition into housekeeping and management activities ones to supervise device specific controls, and its structuring into logic and data modules. This results m a unique frame for all modules in the application hierarchy. It is transparent to the programmes so that the development of specific IMs, EMs and CVMs reduces to editing appropriate data tables, developing specific codes or re-using existing ones . Thus new generation of application software follows modern ideas on conceptual modelling by data abstraction and object-oriented programming.
Computer assisted controls at the 28 GeV PS made their entry in 1967 and today around 80% of the processes are included in various styles. Beam intensity has since increased two orders of magnitude and interleaved cycles of different beam properties are now serving SPS, ISR and the 28 GeV experimental area. This came about by substantial additions to the accelerator equipment, the main one being the Booster and Linac. Plans up to the end of 1980 include: addition of the Antiproton Accumulation Ring, acceleration of antiprotons in the CPS, the concomitant beam transfer and switching, and multibatch filling of the SPS, requiring cycles times down to 0.65 sec. The improvement programme for controls aims to alleviate the operational and maintenance problems ensuing from this explosive expansion and to create a framework for further growth.2. Introduction The importance of efficient controls in the machine studies which led up to and accompanied the improvements and new projects, can hardly be overestimated. Machine studies and even routine operation indeed find themselves growingly impaired by shortcomings, diversity in presentation and underlying logic and by the disjointed nature of the controls that followed the expansion. The upkeep and improvement of hardware and software are scattered over a number of groups and are often only known to one single specialist, hence vulnerability and hard to a6ses total use of resources.Recent trends make a life cycle of another 10 to 15 years highly probable and further growth cannot be ruled out. It was thus decided to build an integrated and user-oriented control systeml that can cope with growth, taking the SPS philosophy2 as a starting point. Users aspects(i) Operators and machine experimenters wish to see a virtual machine, i.e. an apparent structure, following the actions on and the behaviour of the beam, hardware and control intricacies being hidden. As attributes they wish, efficiency, simultaneity, and flexibility for machine experiments, a trustworthy surveyand-alarm system for routine operation.The process is thus divided up so that operationally relevant subsets may be selected through a tree structure from the touch-panels. There are separate trees for different contexts, e.g. starting-up, settingup and machine study, normal operation, probably also a hardware tree and a controls specialist tree. Operations have further specified the applications programs, in particular interactions and displays and they have participated in the choice of console hardware and facilities. A structured naming scheme for process variables and interactions has been divisionally accepted.(ii) Process equipment engineers expect assistance for maintenance and improvements of their hardware. The main consoles being essentially reserved for operation, there is a need for local access through terminals at several levels and facilities for engineers, to develop, load and run their own detailed diagnostic programs for process-hardware off-line or on-line tests. Operators must be able to call fi...
The new CPS controls system1 was successfully put into operation on 19 November, 1980, when the 800 MeV Booster, after switching over to the new system, was started up for particle physics. A subset of the new system had already been installed on the Antiproton Accumulator in Spring 1980 and has reliably served several months of engineering run. The Booster machine and control of the CPS cycle generation are now routinely operated by the new system which is based on distributed processing, extensively applying microprocessors in the interface. The problems encountered in converting existing accelerator controls, the control switchover itself and operational experience gained up to the date of the conference are described.
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