M. Nielbock; 13-Nov-2007
Index
Contents
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 |