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RFX-mod Programme Workshop 2011 – Padova, February 7 th 2011

RFX-mod Programme Workshop 2011 – Padova, February 7 th 2011. RFX-mod Programme Workshop 2011 RFX-mod Feedback Control System Upgrade G. Manduchi, A. Barbalace. MHD Mode Control. Plasma Position Control. Toroidal Field Control. Current Control System Architecture.

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RFX-mod Programme Workshop 2011 – Padova, February 7 th 2011

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  1. RFX-mod Programme Workshop 2011 – Padova, February 7th 2011 RFX-mod Programme Workshop 2011 RFX-mod Feedback Control System Upgrade G. Manduchi, A. Barbalace

  2. MHD Mode Control Plasma Position Control Toroidal Field Control Current Control System Architecture

  3. Main Features of the Current System

  4. Critical Factors

  5. from Distributedprocessing.. processor switch switch New Control System Design ..to Centralized processing There is no latency due to datadistribution over a network

  6. New Control System Architecture

  7. Evaluated Hardware Details We have evaluated National Instruments PXI-6723; a 13bit multi Digital to Analog converter with 32 analog outputs. Each reference generation node is made up with a PXI rack hosting 3 PXI-6723 boards. Every output is used. Data generation completes after 60us (Intel QPI bus) or after 120us (Intel FSB bus). Data transfer is governed by the processing core via Programmed I/O. We have evaluated National Instruments PXI-6255; a non simultaneous sampling multiplexed 16bit ADC with 80 analog inputs. Each acquisition node is made up with a PXI rack hosting 3 PXI-6255 boards. Every board is setup to scan 64 channels periodically. A scan completes in 90us and data is ready to the central processing after few microseconds. Data transfer is mastered by the devices via Direct Memory Access (DMA). Data Acquisition Waveform Generation

  8. Non Simultaneous Sampling Is it possible to realign the samples? Yes, because channels are sampled at known instants. In Real-Time • The reconstruction will lead to a quasi exact low-frequency signal and a less precise high frequency signal. • The acquisition downgrade to 14bit. • Data is filtered via a Fractional Delay FIR implementing Lagrangian interpolation • After the Pulse (offline) • The reconstruction will lead to a theoretically exact signal. • All 16bit could be restored. • Data is convolved with a sinc function. ..but multiplexing introduces also settling time issues due to switching between different channels Frequency spectrum of a sample DFLU signal

  9. Simultaneous Sampling Solutions alternative to evaluated hardware National Instruments IST-IPFN • Data busPXI Express(PCIe) in PXI rack; • PXIe-635816 input channelboards, 16bit; • Each 192-channel acquisition node may be implemented with a PXIe-1075 chassis with12 (18 available) PXIe-6348boards. • Data busPCI Expressin ATCA rack; • Custom devel32 input channelboards,24bit; • Each 192-channel acquisition node may be housed in an ATCA shelf with6custom developed ATCA-MIMO-ISOL boards. Both focus on high data throughput IPFN solution is designed for high availability (five nines)

  10. What about the previous Framework? The software framework developed and currently used in RFX did a good job. However, it has been developed with a well-defined architecture in mind, so it is not so easily portable to new architectures and platforms. New Software Framework Joint efforts in fusion community gave rise to.. • General frameworks for real-time control, notably PCS and MARTe. • PCS has been developed at DIII-D and is used in a few machines (e.g. DIII-D , MAST, EAST). • MARTe has been developed at JET (by the PPCC group in collaboration also with RFX) and is also used in few machines (e.g. JET, FTU, ISTTOK, COMPASS). • MARTe has been chosen!

  11. The current system usesWind River VxWorks Rugged real-time operating system; Some important bugs in TCP/IP communication; Very expensive. Linux is becoming an interesting candidate for the new system Soft real-time system; Real-time extensions of Linux make it a hard real-time low-latency operating system; Linux’s official RT patches are good enough to make it hard real-time OS. We have chosen Linux with its officially released RT patches New Operating System http://www.windriver.com http://www.rtai.org http://www.xenomai.org http://www.kernel.org http://rt.wiki.kernel.org

  12. Pipelined Multicore Execution Real time computation for MHD control is carried out in a pipelined organization with three stages: Data Acquisition, Control Computation, and Reference Waveform Generation. New cores can be added to provide additional computation in the case it can be performed in parallel.

  13. Realtime Performance 8kHz data acquisition Clock Frequency Prototype running: • A simple two stage pipelined I/O cycle developed in MARTe; • RedHat Enterprise Linux 5.5 with RT patches from CERN (Scientific Linux Distribution) kernel 2.6.24.7-149.el5rt; • Multicore Intel Xeon processor E5500 @ 2GHz (4 HT cores x86 64bit) QPI bus; Measured Overall latency 150us (average) 200us (WCET) Prototype setup: • A PXI input rack hosting two NI PXI-6255 acquiring 64*2 input channels; • A PXI output rack hosting two NI PXI-6723 generating 32*2 output references.

  14. Costs Comparison NI Prototype Cost Old System Cost

  15. Mailstone 1 - Deadline 30 March 2011 - Test of NI Prototype in RFX Experimental Campaign Objectives This installation will assess the usability of the evaluated hardware for data acquisition (checking cross-talk and cross-channel switching problems). Investigate the possibility of numerical integration (both integrated and non integrated signals will be acquired). Procedure A first prototype system is being installed for acquiring poloidal field values Requirements Front-end duplication Costs All the computing and acquisition components are available in house. The support computer is recycled (there are no real-time computing to implement on) The IO boards were used in the prototype Front end boards (i.e. signal splitters) must be designed and made. Commissioning Plan (1 of 2)

  16. Mailstone 2 - Deadline TO BE DEFINED - MHD Feedback System Commissioning Objectives Run the new MHD Control System in parallel with the current System. The new system will not interfere with RFX operations. Procedure The new system will be installed in parallel to the current one using signal splitters. Requirements Multicore server; IO boards, cabling and racks; Development of few software components. Costs Multicore server; IO boards, cabling and racks; Front end boards (i.e. signal splitters). Commissioning Plan (2 of 2)

  17. The new Feedback Control System of RFX proposes an innovative hardware architecture in Fusion Devices; distributed nodes communicating via a real-time network (ATM, Ethernet, Reflective Memory) moved to multiprocessor cores and communication is achieved on the same RAM via shared memory. COTS solutions for computing (multicore servers) ADC and DAC (PXI-based solutions with bus extenders) proved cost-effective and reliable. Linux is becoming a very good candidate for real-time feedback control systems in fusion devices. MARTe proved to be an extremely flexible environment to develop Hard Real-Time Control Systems. processor switch switch Conclusions

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