Application of industrial standard process control equipment in neutron scattering experiments

Based on thorough experiences with distributed experiment control systems a nd fieldbus applications we are developing a control system especially targ eted at neutron scattering experiments. Main characteristic is that frontend equipment and control machine are coup led by the industrial fieldbus standard PROFIBUS (DIN 19245, EN 50170). Thi s significantly reduces the amount of cabling necessary. Further, it provid es the proven error recovery and diagnostic features of an industrial field bus to the experiment control area. Frontend equipment comprises industrially available components like SIEMENS "ET200" peripheral devices, PLCs and encoders (Heidenhain). For cost-sensi tive stepper motor control a low-end motor controller from University of Go ttingen is being interfaced directly to PROFIBUS. Widely available SIEMENS- SMP equipment can be coupled by a PROFIBUS-SMP interface developed at our i nstitute. The controlling master is an Intel PC running a diskless Linux version, equ ipped with a home-made PROFIBUS controller in CompactPCI formfactor. As sof tware interface to control applications the TACO framework developed at ESR F is employed. "Device servers" in terms of the TACO client-server architec ture have been created, allowing access to the functions of the control sys tem at different levels, from raw PROFIBUS accesses up to complete motor co ntrol with position encoder feedback.