MPIA CPMechChop PACS Chopper control loop optimisation PACS Commissioning and PV Phase Plan Review 21st – 22nd January 2009, MPE Garching Markus Nielbock, Ulrich Klaas (MPIA) Instrumental background • chopper serves two main purposes M. Nielbock, U. Klaas – CPMechChop – differentiated signal for background subtraction – deflection mirror • uncontrolled power supply causes oscillations • PID control loop modulates drive current to achieve stable chopper plateaus • up to 12 parameters to tune (7 + 5 for oscillation suppression filter) Commissioning programme • four commissioning blocks via real time manual commanding M. Nielbock, U. Klaas – CPMechChop ACT_ID Task Name Duration H_COP_PAC_CHP1_01 PACS Chopper Stability Verification 1 hour H_COP_PAC_CHP2_01 PACS Chopper Dynamic Behaviour Verification 4 hours H_COP_PAC_CHP3_01 PACS Chopper Dynamic Behaviour Verification 4 hours H_COP_PAC_CHP4_01 PACS Chopper Dynamic Behaviour Verification 4 hours • one commissioning block via MTL ACT_ID Task Name Duration H_COP_PAC_CHP5_01 PACS Chopper PID Optimisation Loop & Fine Tuning 10 hours • results provide an updated calibration uplink (CALU) table Stability verification • FM-ILT: amplification of previously unknown resonances M. Nielbock, U. Klaas – CPMechChop • feedback to control loop produces potentially dangerous instabilities • electronic passband filter needs tuning (2 input parameters) Stability verification • verify stability of chopper position in several steps M. Nielbock, U. Klaas – CPMechChop – enable controller for one second without moving chopper – software limits help preventing fatal reactions – enable controller for five minutes without moving chopper – enable controller for five minutes and keep chopper at a few degrees • once established only minor modifications may be necessary • parameter tuning supported by MATLAB modelling • QLA available for on-line check • detailed real time off-line analysis possible within a few minutes • MOIS procedures tested during SOVT-2 at MOC Dynamic behaviour verification • verify proper chopper performance (transition time and pattern) M. Nielbock, U. Klaas – CPMechChop • if unsatisfactory, PID tuning necessary (5 parameters) • set of manual procedures available and tested during FM-ILT and FM-IST • parameter tuning benefits from experience • may be supported by MATLAB modelling • only little modifications are expected during commissioning PID tuning procedure initial set of chopping record M. Nielbock, U. Klaas – CPMechChop parameters input measurement movement generate input analyse adjust MATLAB Model parameter(s) bad good final set of parameters PID tuning procedure • QLA available for on-line check M. Nielbock, U. Klaas – CPMechChop • analysis provides visual and numerical data for evaluation Chopper angle (digital units) stability corridor movement stimulus • best value so far: 19 ms for transition within PACS sky FOV • PID parameters of best performance provide new CALU table PID parameter fine tuning (PICC-MA-TN-002) • automated sequence probing permutations of four PID parameters M. Nielbock, U. Klaas – CPMechChop • modifying one or more parameters can compensate for another • maximum variation by 2% of initial parameter value (from manual tuning) • combinations of two to four parameter variations • in total 159 valid sets available (CALU table) • table produced by automated script with default parameters as input • restriction to subsets possible • translated into CUS and engineering AOT MTL scheduling PID parameter fine tuning (PICC-MA-TN-002) • measurement like manual tuning M. Nielbock, U. Klaas – CPMechChop – 10 chopping cycles @ 0.5 Hz between ± 4° in focal plane • off-line analysis in principle like manual version • identification of parameter sets by setting BBIDs PACS Number of BB (set to zero) Counter used for controller parameter coding Kp Ki KiCurr Kf 2 bits 14 bits sign value sign value sign value sign value 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 x x x x x x x x x x x x x x x x • estimated time required for one full loop: 2.7 h • measurement may be repeated using new set of parameters • PID parameters of best performance provide new CALU table Summary • Commissioning plan for chopper verification and tuning fully defined and M. Nielbock, U. Klaas – CPMechChop implemented. • Separated into four real time manual commanding blocks and one automated MTL block. • All procedures already tested during FM-ILT, FM-IST, SOVT-2. • Off-line analysis is available and thoroughly tested. • requested observation time in total: 23 h (less may be sufficient) • Optional additional refinery can be easily planned and executed.
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