The Real-Time Distributed Control of the Virgo Interferometric Detector of Gravitational Waves

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> The VIRGO experiment for the detection of gravitational waves is a big challenge both for physics and for technology. In particular, to satisfy the stringent requirements on the alignment and position of its suspended optical components to keep the detector at its point, a very complex distributed and supervised control system has been implemented. The current constraints are about <formula formulatype="inline"><tex>$10 ^{-10}~ {\hbox {m}}$</tex></formula> RMS for the longitudinal control (“Locking'') and <formula formulatype="inline"> <tex>$10 ^{-9}~{\hbox {rad}}$</tex></formula> RMS for the angular degrees of freedom (“Alignment''). These requirements are satisfied by means of a specially designed hierarchical architecture for the local control system. It is necessary for managing the hard task of filtering all the environmental noises that limit the sensitivity of the interferometer. On the other end, the interferometer is supervised by a distributed global control system to maintain the detector fully operational. In this paper we describe the status of the real-time distributed control system of the Virgo interferometric detector of Gravitational waves, its performances and planned improvements. </para>