Changes between Version 2 and Version 3 of TOManual/SAMS


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Timestamp:
Jul 26, 2018 4:02:03 AM (6 years ago)
Author:
ebevins
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  • TOManual/SAMS

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    7 SAMS (Segment Alignment Maintenance System) provides information about the relative positions of mirror segments with respect to each other through the use of edge sensors. It calculates the corrections needed to maintain or restore an alignment that was saved in a previous reference, preferably a stacked-mirror reference.
     7           '''SAMS (Segment Alignment Maintenance System)''' provides information about the relative positions of mirror segments with respect to each other through the use of edge sensors. It calculates the corrections needed to maintain or restore an alignment that was saved in a previous reference, preferably a stacked-mirror reference.
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    10 SAMS is made up of 480 edge sensor pairs (an active and a passive) located on the segment edges. Each sensor pair measures mirror (relative) positions, in terms of vertical shear heights and gap widths. There are up to six active sensors on each of the 91 segments, and these (up to) six values are carried to an ADC / DSP board package located on the back of the mirror segment. The 91 segments are grouped into three “hubs”, each containing 30 or 31 segments. A hub collects all of the data from the ADC/DSP packages in its group.  This information is then carried to “the Brick” and the SAMS computer which are both located in the UER (Upper Electrical Room).  SAMS is then able to calculate mirror corrections required based on current sensor positions.
     10            SAMS is made up of 480 edge sensor pairs (an active and a passive) located on the segment edges. Each sensor pair measures mirror (relative) positions, in terms of vertical shear heights and gap widths. There are up to six active sensors on each of the 91 segments, and these (up to) six values are carried to an ADC / DSP board package located on the back of the mirror segment. The 91 segments are grouped into three “hubs”, each containing 30 or 31 segments. A hub collects all of the data from the ADC/DSP packages in its group.  This information is then carried to “the Brick” and the SAMS computer which are both located in the UER (Upper Electrical Room).  SAMS is then able to calculate mirror corrections required based on current sensor positions.
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    24 '''SCS and Sensors lights''' - These lights are shown in the upper-right, just beneath the Errors Encountered log. They are intuitive, Green is “good”, Red is “BAD”, and yellow is “be cautious”. SCS light only turns green when SAMS is talking directly to SCS, which happens once every 34 seconds or so when the two programs are in closed loop. See Common SAMS problems for more information about what to do when Sensors light turns yellow or red.
     24             '''SCS and Sensors lights''' - These lights are shown in the upper-right, just beneath the Errors Encountered log. They are intuitive, Green is “good”, Red is “BAD”, and yellow is “be cautious”. SCS light only turns green when SAMS is talking directly to SCS, which happens once every 34 seconds or so when the two programs are in closed loop. See Common SAMS problems for more information about what to do when Sensors light turns yellow or red.
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    27 '''Commands Received Log''' - This log shows various communications SAMS has with other software (e.g. getttp is request from SCS for tip, tilt, piston corrections) and changes the user makes to SAMS (e.g. if you remove a sensor, it will log it here; if you set/save a new reference, it will log it here). While stacking, there will be a setreloff command logged during every array correction.
     27             '''Commands Received Log''' - This log shows various communications SAMS has with other software (e.g. getttp is request from SCS for tip, tilt, piston corrections) and changes the user makes to SAMS (e.g. if you remove a sensor, it will log it here; if you set/save a new reference, it will log it here). While stacking, there will be a setreloff command logged during every array correction.
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    30 '''Errors Encountered Log''' - This log shows… errors encountered. If there is a sensor with a relatively high TSE (while there is a global TRSE, target residual square error, plotted in the history tab, each sensor has its own TSE, target sensor error), it will be logged here. There are a variety of rare errors that can appear here as well. While the TO cannot monitor this log all night, it is a good place to start investigating if the sensor light turns yellow or red, or SAMS behaves oddly.
     30             '''Errors Encountered Log''' - This log shows… errors encountered. If there is a sensor with a relatively high TSE (while there is a global TRSE, target residual square error, plotted in the history tab, each sensor has its own TSE, target sensor error), it will be logged here. There are a variety of rare errors that can appear here as well. While the TO cannot monitor this log all night, it is a good place to start investigating if the sensor light turns yellow or red, or SAMS behaves oddly.
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    34 '''RSE/TRSE''' - Watching the relationship between RSE and Target RSE is important when operating the SAMS Server. The global RSE/TRSE values are plotted under the History tab. RSE (Residual Square Error) is the current real error across the array; successful SAMS corrections will bring this value down closer to the Target RSE (TRSE) which is the targeted or lowest possible error the system can achieve.  Low RSE and TRSE (<200nm) are ideal, but acceptable TRSE up to 500nm is possible depending on the science and time available in the night.  High TRSE indicates either a significant temperature change since the last reference or a problem.
     34             '''RSE / TRSE''' - Watching the relationship between RSE and Target RSE is important when operating the SAMS Server. The global RSE/TRSE values are plotted under the History tab. RSE (Residual Square Error) is the current real error across the array; successful SAMS corrections will bring this value down closer to the Target RSE (TRSE) which is the targeted or lowest possible error the system can achieve.  Low RSE and TRSE (<200nm) are ideal, but acceptable TRSE up to 500nm is possible depending on the science and time available in the night.  High TRSE indicates either a significant temperature change since the last reference or a problem.
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    36 Depending on the TO, they will use Tip/Tilt Error, Tip/Tilt Scale, or both as their metric for how the primary mirror is maintaining the stack.
     36Depending on the TO, they will use Tip / Tilt Error, Tip / Tilt Scale, or both as their metric for how the primary mirror is maintaining the stack.
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    40 '''Tip/Tilt Error''' - This value is shown directly above the plot for RSE/TRSE in the history tab and as noted is the FWHM (full-width half max) of the tip/tilt errors of all of the mirrors. This is a statistical value, of which the definition will not be explained here. Suffice to say, less the 0.1 is ideal for the mirror while in closed loop, maintaining a stack.
     40             '''Tip / Tilt Error''' - This value is shown directly above the plot for RSE/TRSE in the history tab and as noted is the FWHM (full-width half max) of the tip/tilt errors of all of the mirrors. This is a statistical value, of which the definition will not be explained here. Suffice to say, less the 0.1 is ideal for the mirror while in closed loop, maintaining a stack.
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    43 '''Tip/Tilt Scale''' - This value is shown in the upper-right of the TTP’s tab, showing the color-coded array. This graphic is normally left in auto-scale mode, so the T/T scale is the length of a vector from the center of a segment to its edge. It can more easily be thought of as a maximum T/T error of a single segment. The ideal value for this metric is <0.2.
     43             '''Tip / Tilt Scale''' - This value is shown in the upper-right of the TTP’s tab, showing the color-coded array. This graphic is normally left in auto-scale mode, so the T/T scale is the length of a vector from the center of a segment to its edge. It can more easily be thought of as a maximum T/T error of a single segment. The ideal value for this metric is <0.2.
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    46 '''Segment Data''' - This tab shows detailed information about individual sensors and the tip, tilt and piston corrections needed for a single segment.
     46             '''Segment Data''' - This tab shows detailed information about individual sensors and the tip, tilt and piston corrections needed for a single segment.
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    49 '''Configuration''' - This tab is where the user can disable or enable sensors and segments in the array. The selection of changes can be made while the Server is in Operate mode, but must be put into Standby before the changes will actually occur. If done quickly enough between SCS moves, these changes can be made while SAMS is in closed loop with SCS.
     49             '''Configuration''' - This tab is where the user can disable or enable sensors and segments in the array. The selection of changes can be made while the Server is in Operate mode, but must be put into Standby before the changes will actually occur. If done quickly enough between SCS moves, these changes can be made while SAMS is in closed loop with SCS.
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    52 '''Operation Control''' -  In general, this tab should be ignored. The only change the TOs should make in this tab is to change the max TRSE value (but no higher than 1500).
     52             '''Operation Control''' -  In general, this tab should be ignored. The only change the TOs should make in this tab is to change the max TRSE value (but no higher than 1500).
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    55 '''Shear/Gap/and Temperature Tabs''' - These tabs show colored array graphics of the corresponding values; e.g. unser shear, the shear values for all sensors are scaled relative to each other. Similar, to the TTPs tab, these are normally left in auto-scale mode.
     55             '''Shear / Gap / and Temperature Tabs''' - These tabs show colored array graphics of the corresponding values; e.g. unser shear, the shear values for all sensors are scaled relative to each other. Similar, to the TTPs tab, these are normally left in auto-scale mode.
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    5959== Common SAMS Problems ==
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    61 '''High Target RSE:'''
     61             '''High Target RSE:'''
    6262High TRSE is anything above 1000nm in the SAMS Server.  Large change in temperature since the last SAMS reference can cause high TRSE, but if temperature change has not occurred since the previous night, high TRSE alerts the TO there could be a hardware problem.  Changing the Operation Control above 1500nm should only be done if the cause is understood. If not understood by the TO, contact a member of the mirror team otherwise rather than lowering the error, it will most likely only be distributed across the array.  High TRSE could be caused by a failing sensor, bad segments or segment positions, a bad SAMS reference, or other system failures.  Because the cause could be a number of things, the solution depends on the problem.  Removing sensors or segments, loading a SAMS reference closer to the current temp, re-loading the last SCS position file, or applying GRoC to the mirror are all potential solutions to HIGH TRSE. Please don’t guess at a solution and call another TO or mirror team member to help instead.
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    65 '''Bad sensor''' (poor sensor alignment, faulty electronics, broken cables, broken sensor mount, etc):
     65            '''Bad sensor''' (poor sensor alignment, faulty electronics, broken cables, broken sensor mount, etc):
    6666When a sensor fails, it will report in the SAMS Server with either a warning (yellow light) or a failure (red light).  SAMS will continue to operate through warnings though they can increase TRSE; the offending sensor may need to be removed.  SAMS will not operate through a failure; the sensor must be removed.  Typically, reported LTSEs (Large Target Sensor Error) are associated with yellow light warnings and +/- 384s are associated with red light failures.  If sensor failure extends across SAMS “Hub” groups, it is indicative of a larger comm problem.
    6767Note: For how to remove a sensor for any of the above cases, please refer to ‘Removing sensors from SAMS’ on page 23.
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    70 '''Bad segment''' (no active sensor values, comm problems, ADC/DSP connection failure, etc):
     70           '''Bad segment''' (no active sensor values, comm problems, ADC/DSP connection failure, etc):
    7171When a segment fails to report information, all active sensors on the segment will read +/- 384.  The red failure light will be displayed.  The segment must be removed.  This problem is typically associated with poor hardware connections. If all twelve sensors read +/- 384, a very rare event (very hopefully avoided) could be due to the segment being pistoned above or below sphere.
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    74 '''Bad segment(s''') (not moving in one axis, not moving at all, not applying SAMS corrections):
    75 When a segment stops moving, the array will not be able to correct to the reference.  The RSE and TRSE will increase and the SAMS Server will display the problem as a segment(s) developing larger vectors in Tip/Tilt and error in Piston. You will see the Tip/Tilt Scale increase.  The segment must be removed and quickly because the rest of the array will move to accommodate its position.  If this failure extends across many segments in SAMS or SCS control groups, it could be indicative of a larger comm or power failure.  Restart may resolve the issue, but a call to the mirror team is likely necessary. 
     74          '''Bad segment(s''') (not moving in one axis, not moving at all, not applying SAMS corrections):When a segment stops moving, the array will not be able to correct to the reference.  The RSE and TRSE will increase and the SAMS Server will display the problem as a segment(s) developing larger vectors in Tip / Tilt and error in Piston. You will see the Tip/Tilt Scale increase.  The segment must be removed and quickly because the rest of the array will move to accommodate its position.  If this failure extends across many segments in SAMS or SCS control groups, it could be indicative of a larger comm or power failure.  Restart may resolve the issue, but a call to the mirror team is likely necessary. 
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    83 SCS (Segment Control System) is the system that moves the 91 segments. SCS is made up 273 linear actuators (3 actuators per mirror segment). While the 3 actuators can be moved individually, normally they are used to tip (rotate about the horizontal axis), tilt (rotate about the vertical axis) or piston (move up or down) the mirrors.
     82          '''SCS (Segment Control System)''' is the system that moves the 91 segments. SCS is made up 273 linear actuators (3 actuators per mirror segment). While the 3 actuators can be moved individually, normally they are used to tip (rotate about the horizontal axis), tilt (rotate about the vertical axis) or piston (move up or down) the mirrors.
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