Application of industrial standard process control equipment in neutron scattering experiments

Based on thorough experiences with distributed experiment control systems and fieldbus applications we are developing a control system especially targeted at neutron scattering experiments. Main characteristic is that front-end equipment and control machine are coupled by the industrial fieldbus standard PROFIBUS (DIN 19245, EN 50170). This significantly reduces the amount of cabling necessary. Further, it provides the proven error recovery and diagnostic features of an industrial fieldbus to the experiment control area. Front-end equipment comprises industrially available components like SIEMENS "ET200" peripheral devices, PLCs and encoders (Heidenhain). For cost-sensitive stepper motor control a low-end motor controller from University of Gottingen is being interfaced directly to PROFIBUS. Widely available SIEMENS-SMP equipment can be coupled by a PROFIBUS-SMP interface developed at our institute. The controlling master is an Intel PC running a diskless Linux version, equipped with a home-made PROFIBUS controller in CompactPCI formfactor. As software interface to control applications the TACO framework developed at ESRF is employed. "Device servers" in terms of the TACO client-server architecture have been created, allowing access to the functions of the control system at different levels, from raw PROFIBUS accesses up to complete motor control with position encoder feedback.