Subject: Re: [sloan-25mlog 2034] 2.5m obslog 20141223 (SJD 57015) From: Joseph Huehnerhoff Date: Wed, 24 Dec 2014 02:02:02 -0800 --Apple-Mail=_D191ECD3-1AF9-4AF1-86BC-C9C67B7ECD3B Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset=us-ascii I mainly see the rotator initialize to a non-zero value if an e-stop is = not in, or there is some built up error. The rotator does not have a brake, that is why it can move when a = cartridge bumps it. Joe > On Dec 24, 2014, at 1:56 PM, Daniel Oravetz = wrote: >=20 > Thanks, Dan. We've seen this happen on occasion within the last month = or > two, particularly on at least two separate occasions during afternoon > checkout. I don't remember it taking two attempts at zeroing the = rotator > to get things to work like it did early this morning, though. Is it > possible that the cold weather degraded the efficacy of the axis brake > sufficiently enough such that the small torque during instrument = change > was enough to more consistently result in movements greater than 1.5'? = And > do you have any insight as to why the rotator would have initialized = to > 000:05:22 twice? >=20 > Thanks, > Dan >=20 >=20 >=20 >=20 >=20 >=20 >=20 >> The rotator can be moved a little by the process of cartridge change = when >> the lift plate and its alignment system apply a small torque to the >> rotator. The interlocks allow the lift to go down if the rotator is >> slightly out of position, but will not allow it to go up, which would >> explain what was seen last night. >>=20 >> It is unfortunate that the tolerance for the spectrograph opening is = tight >> enough to require a +/- 1.5 arc minute range, and that occasionally = it is >> possible to make the rotator move that much during a swap, but such = is the >> design of the system. >>=20 >> Another aspect of the rotator position interlock is that if it is out = of >> position, it will not grant a latch permit, which is why cartridge 11 >> would not latch until the rotator position was zeroed. >>=20 >> Note that if you have determined that the reason you cannot latch is = due >> to the rotator being a couple arc minutes out of position, the best >> course of action at that point is to switch the latch control panel = to >> manual and finish latching. Again, this assumes that is the only = reason >> for the lack of permit (e.g. the ID, height, force, etc all are = okay). >>=20 >> -Dan >>=20 >>=20 >> On Dec 24, 2014, at 5:31 AM, doravetz@apo.nmsu.edu wrote: >>=20 >>>=20 >>> APACHE POINT OBSERVATORY SDSS 2.5M >>>=20 >>> OBSERVING LOG >>> Tuesday December 23, 2014 >>>=20 >>> (SJD 57015) >>>=20 >>> ---- Observing Team ---- >>>=20 >>> Viktor Malanushenko >>> Daniel Oravetz >>>=20 >>>=20 >>=20 >>=20 >>=20 >>> * We had some problems with the cartridge change before we called it = a >>> night >>> involving sticky cartridge latches and odd rotator positions. See = the >>> end of the >>> Log body for details. >>>=20 >>=20 >>=20 >>=20 >>> Mounted cart. 11 for tomorrow. Initiated morning calibration = sequence. >>> Shut >>> things down for the night. >>>=20 >>> We had problems during the cartridge change (~11:45Z - 12:05Z). = First >>> off, after >>> cart. 6 was dismounted and the Linde cart moved into position to = mount >>> cart. 11, >>> the lift would not go up. We found the lift_up_enable logic was >>> red/false >>> because the rot_inst_chg_a bit was red/false. We checked the rotator >>> position >>> and saw it was at 1.7 arc minutes. How/why did the rotator move from = an >>> acceptable position to actuate the lift and remove cart. 6 to an >>> unacceptable >>> position when subsequently attempting to mount cart. 11? >>>=20 >>> When we initialized the rotator before sending it to 0, the rotator >>> position >>> read 000:05:22. (again, we aren't sure what to attribute this = seemingly >>> random >>> position to). We sent the rotator to 0 and then the lift worked = fine. >>> When we >>> tried to latch cart. 11, however, the latches would not actuate. We >>> lowered the >>> lift, backed out the Linde cart and inspected the latches. The = latches >>> on the >>> cartridge were quite sticky and the W latch had a tension wire that >>> looked out >>> of position. We were able to jostle the sticky latch and get the = tension >>> wire to >>> its appropriate position (which we figured out by looking at the = other >>> latches). >>> When we pushed the Linde cart back into position, the lift wouldn't = work >>> again. >>> We check the MCP and again the rotator was at 1.7 arc minutes. When = we >>> initialized, it again showed the rotator at 000:05:22 and we = visually >>> confirmed >>> the rotator had moved (albeit an almost indiscernible amount as = measured >>> by-eye) >>> by looking at the rotator position needle underneath the Instrument >>> Latch >>> Controller. Once we sent the rotator back to 0, the lift worked and = then >>> the >>> latches worked properly, too. >>>=20 >>=20 >>=20 >=20 >=20 > ____________________________________________________________ > Logs of Nightly APO Activities > = https://trac.sdss.org/tracmailman/browser/private/sloan-25mlog/index.html --Apple-Mail=_D191ECD3-1AF9-4AF1-86BC-C9C67B7ECD3B Content-Transfer-Encoding: quoted-printable Content-Type: text/html; charset=us-ascii I mainly see the rotator initialize to a non-zero value if an = e-stop is not in, or there is some built up error.The rotator does not have a brake, that = is why it can move when a cartridge bumps it. Joe On Dec 24, 2014, at 1:56 PM, Daniel Oravetz wrote:Thanks, Dan. We've = seen this happen on occasion within the last month ortwo, = particularly on at least two separate occasions during afternooncheckout. I don't remember it taking two attempts at zeroing = the rotatorto get things to work like it did early this = morning, though. Is itpossible that the cold weather = degraded the efficacy of the axis brakesufficiently = enough such that the small torque during instrument changewas enough to more consistently result in movements greater = than 1.5'? Anddo you have any insight as to why the = rotator would have initialized to000:05:22 twice?Thanks,DanThe = rotator can be moved a little by the process of cartridge change whenthe lift plate and its alignment system apply a small torque = to therotator. The interlocks allow the lift to go = down if the rotator isslightly out of position, but will = not allow it to go up, which wouldexplain what was seen = last night.It is unfortunate that the = tolerance for the spectrograph opening is tightenough to = require a +/- 1.5 arc minute range, and that occasionally it ispossible to make the rotator move that much during a swap, = but such is thedesign of the system.Another aspect of the rotator position interlock is that if = it is out ofposition, it will not grant a latch permit, = which is why cartridge 11would not latch until the = rotator position was zeroed.Note that if = you have determined that the reason you cannot latch is dueto the rotator being a couple arc minutes out of position, = the bestcourse of action at that point is to switch = the latch control panel tomanual and finish latching. = Again, this assumes that is the only reasonfor the = lack of permit (e.g. the ID, height, force, etc all are okay).-DanOn Dec 24, 2014, at 5:31 AM, doravetz@apo.nmsu.edu= wrote: = &n= bsp; APACHE POINT = OBSERVATORY SDSS 2.5M = &n= bsp; &nbs= p; OBSERVING LOG = &n= bsp; Tues= day December 23, 2014 = &n= bsp; &nbs= p; (SJD 57015)---- Observing Team ----Viktor MalanushenkoDaniel Oravetz* We had = some problems with the cartridge change before we called it anightinvolving sticky cartridge latches and = odd rotator positions. See theend of theLog = body for details.Mounted cart. 11 for tomorrow. Initiated morning calibration = sequence.Shutthings down for the night.We had problems during the cartridge change = (~11:45Z - 12:05Z). Firstoff, aftercart. 6 = was dismounted and the Linde cart moved into position to mountcart. 11,the lift would not go up. We found = the lift_up_enable logic wasred/falsebecause= the rot_inst_chg_a bit was red/false. We checked the rotatorpositionand saw it was at 1.7 arc minutes. = How/why did the rotator move from anacceptable position = to actuate the lift and remove cart. 6 to anunacceptableposition when subsequently attempting to mount cart. 11?When we initialized the rotator before sending = it to 0, the rotatorpositionread = 000:05:22. (again, we aren't sure what to attribute this seeminglyrandomposition to). We sent the rotator to 0 = and then the lift worked fine.When wetried = to latch cart. 11, however, the latches would not actuate. Welowered thelift, backed out the Linde cart and = inspected the latches. The latcheson thecartridge were quite sticky and the W latch had a tension = wire thatlooked outof position. We were = able to jostle the sticky latch and get the tensionwire = toits appropriate position (which we figured out by = looking at the otherlatches).When we = pushed the Linde cart back into position, the lift wouldn't workagain.We check the MCP and again the rotator = was at 1.7 arc minutes. When weinitialized, it again = showed the rotator at 000:05:22 and we visuallyconfirmedthe rotator had moved (albeit an almost indiscernible amount = as measuredby-eye)by looking at the = rotator position needle underneath the InstrumentLatchController. Once we sent the rotator back to 0, the lift = worked and thenthelatches worked properly, = too.____________________________________________________________Logs of Nightly APO Activities https://trac.sdss.org/tracmailman/browser/private/sloan-25mlog/= index.html= --Apple-Mail=_D191ECD3-1AF9-4AF1-86BC-C9C67B7ECD3B--