Cms Dcs Design Concepts

CMS uses PVSSII [1] and the Joint Controls Project (JCOP) framework [2] to develop the Detector Control System (DCS) of its experiment. PVSSII is a commercial SCADA system and the JCOP framework is an in-house software project of CERN. These tools enable developers to create control applications for a supported set of hardware devices. In addition, other commercial and CERN-made hardware/software solutions are used where necessary. The JCOP framework contains a Finite State Machine (FSM) toolkit. Sub-detector and service experts use this toolkit to build control trees based on FSMs. CMS has put policies into place to ensure a homogeneous and coherent use of its DCS. The different control systems of the experiment have been integrated into a single control tree, whose top node is referred to as the CMS DCS Supervisor. This supervisor manages the control systems of all sub-detectors and support services. These control systems are distributed among different machines and run on different operating systems and platforms. CMS developed new software and concepts in order to integrate its DCS. A plug-in system was developed to facilitate the load balancing of control processes across DCS PCs. Software maintenance was eased through the introduction of a central software repository. A monitoring system was written to provide a 3D view of the experiment that shows errors and their geometric correlations. A rack control and monitoring application was also developed for the experiment, and this application has been included in the JCOP framework to be used by all LHC experiments.