M. Nielbock; 13-Nov-2007

Index

1. IST Chopper Day at Astrium (2007-11-15)

According to Sect. 11 of the PACS IST Procedure Document (PACS-ME-TP-021, Issue 2.5), we will verify the functionality of the PACS chopper during an especially dedicated "Chopper Day" during FM-IST at Astrium. This includes three steps for both the nominal and redundant operations. The CUS scripts are the same for both parts; we will adjust the suitable chopper control parameters by editing and uploading the referring CALU table.

1.1. Chopper Zero-Point Offset Nulling

The mechanical zero point can shift depending on the orientation of the chopper with respect to the gravitational vector. Variations may occur in the range of a few hundred ROUs. The zero point offset can be determined by measuring the HK parameter DMC_CHOP_CUR_POS without applying any drive current to the chopper coils. In this case, it is included in the open-loop measurement.

The command sequence is:

CUS script

Description

1.

PACS_GeGa_SFT_Init_Cold_OBS

parameter initialisation for He-I condition

or

PACS_GeGa_SFT_Init_Cold_He2_OBS_Shell

parameter initialisation for He-II condition

2.

PACS_Chopper_SFT_Cold_OpenLoop_OBS

performs open loop sequence

3.

CONF_chopper_ast_OBS_Shell

uploads chopper parameters after editing zero point offset

1.2. Verify Stability of the Chopper

Experience from FM-ILT shows that the chopper system is susceptible to high-frequency oscillations which are suppressed by an electronic elliptical filter introduced into the DECMEC software. In order to avoid a damage to the chopper, the correct filter setting must be verified. The dedicated test scripts enable the chopper controller for some time and monitor its stability. If unexpected oscillations appear, the filter settings will have to be adjusted and tested with another script execution before advancing to the next step in the command sequence. For safety reasons, scripts allowing to disable the chopper controller during the measurements should be prepared for execution, if the chopper runs into oscillations.

The command sequence is:

CUS script

Description

1.

WriteOBSID_ast_OBS

writes the OBS-ID

2.

CONF_chopper_ast_OBS_Shell

uploads the current chopper control parameters

3.

PACS_Chopper_EnDis_Test_ast1_OBS_Shell

enables chopper controller for one second

4.

CONF_chopper_ast_OBS_Shell

uploads the current chopper control parameters

5.

PACS_Chopper_EnDis_Test_ast300_OBS_Shell

enables chopper controller for five minutes

6.

CONF_chopper_ast_OBS_Shell

uploads the current chopper control parameters

7.

PACS_Chopper_EnDis_PlateauTest_ast_OBS_Shell

enables chopper controller for five minutes while chopper is deflected statically

8.

WriteENDID_ast_OBS

resets the OBS-ID

Emergency scripts ready for execution, if oscillations are excited:

CUS script

Description

Chop_1

PACS_SwOn_chopper_ast_OBS_Shell

switches on chopper

Chop_2

PACS_SwOff_chopper_ast_OBS_Shell

switches off chopper

Chop_3

PACS_En_chopper_ast_OBS_Shell

enables chopper controller

Chop_4

PACS_Dis_chopper_ast_OBS_Shell

disables chopper controller

1.3. Chopper Controller Optimisation

This task is a highly interactive process. The chopper performance during a chopping sequence will be analysed in order to evaluate its performance. The chopper control parameters must be adjusted accordingly and uploaded to the control system. Afterwards, the changes will be verified again by a chopping sequence (repeat steps 3 and 4). We provide four different CUS scripts, each performing a sequence of ten chop cycles at a frequency of 1 Hz and different chopper angles between one and eight degrees.

The command sequence is:

CUS script

Description

1.

WriteOBSID_ast_OBS

writes the OBS-ID

2.

PACS_SwOn_chopper_ast_OBS_Shell

switches on chopper system

3.

CONF_chopper_ast_OBS_Shell

uploads the current chopper control parameters

4.

PACS_Chopper_uk_move_3000_ast_OBS_Shell

performs non-synchronised 1 Hz chopping between +/- 3000 ROU (+/- 1 deg)

PACS_Chopper_uk_move_12000_ast_OBS_Shell

performs non-synchronised 1 Hz chopping between +/- 12000 ROU (+/- 4 deg)

PACS_Chopper_uk_move_18000_ast_OBS_Shell

performs non-synchronised 1 Hz chopping between +/- 18000 ROU (+/- 6 deg)

PACS_Chopper_uk_move_21000_ast_OBS_Shell

performs non-synchronised 1 Hz chopping between +/- 21000 ROU (+/- 8 deg)

5.

WriteENDID_ast_OBS

resets the OBS-ID

2. Further IST Procedures

Further FM IST Procedures

Herschel: PACS/FM_IST_Procedures/MPIAprocedures (last edited 2009-07-15 14:32:38 by localhost)