Mertens, V

Neu, G

Raupp, G

Treutterer, W

Zasche, D

Zehetbauer, T

CERN Document Server

CONFIGURATION ENVIRONMENT FOR THE ASDEX UPGRADECONTROL SYSTEMG. Neu, V. Mertens, G. Raupp, W. Treutterer, D. Zasche, T. Zehetbauer, and ASDEX UpgradeTeam, Max-Planck-Institute for Plasma Physics, Euratom Association, Garching, GermanyAbstractASDEX Upgrade is a tokamak fusion device controlledby a network of real-time control computers. Magneticfield coils, fuelling and heating systems may be operatedfeedforward or used in various feedback control loops. Thereal-time control system is parameterized by a dischargeprogram, i.e. a set of time varying value trajectories tochoose among control algorithms, to define feedforwardand feedback references and set control flow conditions.An environment to configure such a system has to bebased on control and monitoring processes implementedin the currently installed discharge control software and onactually connected I/O hardware. A process oriented userinterface for the input of reference values facilitates thephysicist’s orientation while assembling a dischargeprogram.1. INTRODUCTIONA fully digital discharge control system (DCS), such asthat of ASDEX Upgrade, offers the advantage tocontinuously extend control options to flexibly fine tunecontrol scenarios according to the envisaged dischargegoal. However, this comes hand in hand with anincreasing complexity of the control system structure andthus implies an increasing potential for errors in theconfiguration process.After an overview of the discharge control system, thispaper will focus on configuration issues, indicatepotential sources for inconsistencies and show how acarefully designed configuration environment can help toavoid these.2  THE DISCHARGE CONTROLSYSTEM2.1. TasksThe main tasks of the DCS are:- Physics control, comprising position and shapecontrol tasks and plasma performance controltasks, and- Supervision control responsible for the overallcoordination of the physics control tasksPosition and shape control computes a selected set ofplasma equilibrium parameters from current and fluxmeasurements and controls a selected subset of theseparameters using the tokamak’s vertical field coil system.Although there is a sound theoretical base formultivariable control of the distant coils, the power andcurrent limits and the mutual coupling make this a highlycomplex task. As a result stable feedback control for agiven machine setup is only possible for specific subsetsof shape parameters and by applying precisely calculatedcontrol parameters, gains and feedforward references [1].Performance control accesses the various fuelling andheating systems to concurrently control parameters ofplasma bulk, surface and divertor. The involvedelementary single-variable feedback control processes andgain parameters are based on heuristic knowledge.Meaningful combinations of simultaneously operatingsingle-variable processes are combined into a recipe [2],avoiding mismatch of actuators or control variables.Supervision control tracks the overall system state,collecting the results of physical and technical monitoringprocesses. These range from simple threshold checks tocomplex detection of plasma states or instabilities. In caseof alarms, instabilities, severe deviations from theschedule, or plasma states attained, alternate program segments may be activated. As a reaction,specific sets of control processes or reference trajectoriesare applied to optimize discharge control performance [3].2.2. Structure The structure of the DCS closely reflects the abovedescribed task decomposition [Fig 1]:performance diagnosticsmagnetic measurementsequilibriummonitoring resultsplasma regime& stability infoAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAMonitoring & SupervisionAAAAPerformance controlAAPos. & Shape controlAAcoil & vessel diagnostics vertical field coilscoil systemmonitoring resultsCoil System MonitoringPerformance ControllerPos. & Shape ControllerSupervision Controllerheating fuellingnew segmentFigure 1: Discharge Control SystemInternational Conference on Accelerator and Large Experimental Physics Control Systems428International Conference  Accel rator and L rge Experim ntal Physics Control Systems, 1999, Trieste, Italy- The supervision controller performs simplemonitoring tasks, collects results from these andfrom external monitoring processes in a bit-vector and compares it to active branchingconditions- The position and shape controller computes,controls, and monitors equilibrium parameters- The performance controller performs controltasks involving fueling and heating, andevaluates plasma state and stability- The coil system controllers perform the morecomplex monitoring of thermal, mechanical, andelectrical stress of the toroidal and poloidalmagnetic field coil systems3  CONFIGURATION The DCS is configured via the (executable) dischargeprogram (DP) and private parameter files which aredownloaded into the controllers prior to a discharge. Allquantities in the DP have a unique identifier (QID)through which they are accessed by the DCS and theconfiguration environment. A record with attributes foreach quantity is held in the quantity descriptor (QTD)database3.1. Discharge ProgramThe DP is assembled in two steps: [Fig 2]First, the experiment leader has to edit the physicalshot program (PSP) – which embodies his/her idea of theevolution of a discharge - using the shot program editor(SPE). The SPE’s graphical user interface is used to insertor modify the values of quantities that govern the physicalaspects of the experiment to be performed. These are:- Switches for the dynamic activation of processesand for the selection of control or monitoringparameters (recipes).- Waveforms and constants required for theexecution of activated control and monitoringprocesses (reference values, gain factors,thresholds...)In a second step the PSP is linked with the followingadditional data:- Technical parameters (constants) reflecting thecurrent settings of the machine control system- Machine limits, which are fixed and reflect theengineering design parameters of the experiment(max. coil currents, etc.)- I/O information from the QTD database requiredfor the correct de- and encoding of peripheralsignals (actuator and sensor scaling, multiplexaddresses, bit-positions...) The DP is organized in segments representing distinctphases of a discharge. The segments are concatenatedthrough execution conditions, which are evaluated in real-time against the current state of the experiment bysupervision control. A flag in the QTD record of each parameter indicates ifthe values for this parameter are to be created by editing orin the linking process A detailed description of the DP data structure can befound in reference [4].3.2. RequirementsTo deliver the expected results a DP must fulfil severalrequirements. It should be- Compatible with the currently installed softwareand peripheral hardware.- Complete in that all activated processes shouldbe fully parameterized.- Free of internal contradictions (no two processeswith conflicting objectives should be active)The following examples illustrate these requirements:- When an execution condition is used forsupervision control all involved monitoringprocesses must be activated and correctlyconfigured.- When a performance control recipe is active, allparticipating elementary control processes mustbe correctly configured. (This usually impliesthat all actuators that are used by these processesmust be made available to them).- Position and shape control parameters monitoredby some range-check process must be in the setof computed equilibrium parameters- Reference values for controlled quantities whichalso serve as inputs for some monitoring Machine LimitsPhysical Shot ProgramTemplatesQuantityDescriptor DatabaseExecutable Discharge ProgramLinkerProcess and ImplementationDatabaseCurrent. settings ofMachine ControlsystemPhysical Shot ProgramEditor  Figure 2: Assembly of a Discharge Program.429process should (normally) not exceed themonitoring processes thresholdsAnother issue is the compatibility of the settings ofmachine control system with the requirements of thePSP. See reference [5] for an extensive treatment of thissubject.4 ENVIRONMENT4.1. Process and Implementation DatabasesTo assist the experiment leader in editing a PSP thatfulfils the above consistence and completenessrequirements the editor must be „aware“ of the softwareversion the PSP is being edited for.This is be achieved by defining a process and animplementation database. Each process record contains- The Process ID (PID), a unique identifier for theprocess.- A process type identifier- QIDs for all quantities used by the process- A string describing the role of each parameterwithin the process (e.g. threshold, referencevalue, clipping value). Implementation records contain:- The release number of a controller software- A list of the PIDs of the processes itimplements- Activation conditions (possibly “none” forprocesses which are always active) for each ofthe listed processes.4.2. Editor ConfigurationWhenever the editor is started, it is passed the releasenumber of the current software. It can use this as a key toaccess the installation database and obtain a list of PIDsand activation conditions of all processes implemented bythe software. The PIDs are used to retrieve QIDs andrelated signal information from the process database.Finally the QIDs are used to obtain signal descriptorsfrom the QTD database.4.3. Editor Features Additional features for the editor support theexperimentalist:- It offers a process-oriented view of theconfiguration parameters.- It offers a view oriented on actuator systems(Coil systems, heating systems, fuellingsystems)- It provides navigation facilities, e.g. from aprocess to an actuator feedforward signal- It permits the generation of waveforms (e.g.creating limits of a range check monitoringprocess by specifying a reference waveform and amaximum deviation around it)- It allows importing of waveforms from externalsources. (This is be very useful for parameterscomputed by simulation )- It warns when conflicts are recognized.5  CONCLUSIONThe complexity of the control tasks an theirinterdependence makes building a discharge program forthe ASDEX Upgrade tokamak DCS a demanding task.The introduction of process and implementationdatabases into the configuration environment helps toensure that a discharge program is compatible with thecurrent control software and the connected peripheralhardware.An improved user interface for the PSP Editor helps toguide the experiment leader through the configurationprocess.The described configuration environment both reducesconfiguration time in the experiment cycle and increasesthe likelihood of a successful discharge execution.6 REFERENCES[1] W. Treutterer, J. Gernhardt, O. Gruber, P. McCarthy,G. Raupp, U. Seidel, and ASDEX Upgrade Team,"Plasma Shape Control Design in ASDEX Upgrade",Proc. 19th Symposium on Fusion Technology,Lisbon (P), 1996, p. 933[2] V. Mertens, C. Aubanel, O. Gruber, G. Neu, G.Raupp, H. Richter, W. Treutterer, T. Zehetbauer, D.Zasche, ASDEX Upgrade Team, NBI Team, ICRHTeam, "Plasma Performance Optimization onASDEX Upgrade", Fusion Technology 32, p. 459[3] G. Raupp, O. Gruber, A. Kallenbach, V. Mertens, G.Neu, W. Treutterer, T.Zehetbauer, D. Zasche,"Discharge Supervision Control on ASDEXUpgrade", Fusion Technology 32, p.444[4] D. Zasche, K. Förster, R. Huber, A. Jülich, G. Neu,G. Raupp, H. Richter, U. Schneider, "TokamakDischarge Description at ASDEX Upgrade", 8thConference on Real-Time Computer Applications inNuclear, Particle and Plasma Physics, Vancouver,(CDN), 1993, p. 264[5] D. Zasche, K. Behler, G. Neu, G. Raupp, W.Treutterer, T. Zehetbauer and ASDEX Upgrade Team,"Automatic Setting of Machine Control with PhysicsOperation Parameters ", IAEA Workshop on DataAcquisition and Management for Fusion Research,Lisbon (P), July, 1999430

Configuration Environment for the ASDEX Upgrade Control System

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