PACS PV Phase Plan by theleopardus

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									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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