Hard Real-Time Networks for Fast Feedback and Timing
S.Hunt (AHB) A.Zagar, J.Dedic, K.Zagar*, P.Kolaric, R.Sabjan, R.Stefanic (Cosylab)
Large experimental physics facilities are frequently large, with components of the control system interconnected with cables that can be kilometers in length, making accurate time synchronization and closed feedback loop implementation a challenge. Feedback loops incorporate inputs from dozens of sensors, driving multiple actuators, at kHz rates. Such facilities include CERN's LHC, where the controlled equipment is placed along the 27km ring; the ITER experiment, where about 150 plant system will diagnose and actuate the plasma so that it does not harm the reactor's wall; and the ESO's proposed 42-meter E-ELT optical telescope, whose adaptive optics will need to cancel-out the effects of the atmosphere. We report on evaluation of hard real-time network technologies: 1) application of gigabit ethernet with high-end switches and real-time Linux operating system to achieve a deterministic 1kHz closed-loop; 2) IEEE 1588 compliant equipment to achieve sub-microsecond time synchronization; and 3) performance of low-latency solutions for hard real-time event propagation, in particular Micro-research Finland's timing system and CERN's proposed White Rabbit protocol.