Operating the VELO Motion System while being under vacuum

Make sure the PVSS-project "VEDCS_VacMot" is running under "velo_user" on "vedcs02w". If not, start it. If "gedi" is not running yet, start it. Then start via "Vision" the panel G:\velo\pvss\VELO_VacuumMotion\panels\VeloMotionUI_Main.pnl


A number of conditions has to be satisfied in order to be able to move the VELO-detectors.

  • the red emergency mushroom button of the stepping motors in rack C3B03 on platform C3 have to be pulled to the out-position,
  • all 3 coordinates of the system have to be in "Referenced"-mode, as depicted in the panel above, (if not the system first has to be referenced, but since this is a non-standard procedure an expert should be contacted first),
  • the motion-PLC has to be in "remote" mode (can be seen on the panel with details, see below),
  • there should be no interlock from the vacuum system (can be seen on the panel with details, see below),
  • LHC should be in the state "Movable devices Allowed", otherwise the beam will get dumped when moving away from the "out"-position.

The VELO closing procedure, which requires a password at each step, has be followed till further notice.

Detailed information about the state of the motion system can be obtained by clicking the button "Motion Control Status". A panel like shown below will pop up.

Here a short explanation of the most important parameters and status bits is given:

  • the readings of the 3 resolvers (XA, XC and Y)
  • the readings of the 3 stepper motors (XA, XC and Y)
  • the readings of the 3, 3 and 4 potmeters of XA, XC and Y
  • a button to initiate the referencing procedure. Take care: this should only (!!) be done if the system has come into an unreferenced state. First find out why this happened and only press this button after consulting an expert, because the detectors will move to the outside until they hit their reference switch. For XA (XC) this is located at 29.8 (-29.8) mm . The one for Y is at +4.9 mm. But in order to be able to reference Y, first XA (XC) is moved to the position 15 (-15) mm.
  • Wanted Position: the by the user given next destination for XA, XC and Y
  • ResolverPosition: the present value of the resolver of XA, XC and Y
  • StepperPosition: the present value of the stepper motor of XA, XC and Y
  • All the bits with the word "Error" identify a specific error condition
  • Referencing: if a bit is on it means that axis is presently being referenced (see above)
  • IsReferenced: if a bit is on it means this axis has been referenced
  • Moving: if a bit is on it means this axis is presently moving
  • Local/PVSS: if this bit is on it means the PLC is in Local/PVSS mode
  • ExpertMode_On: if this bit is on someone is working in expert mode at the PLC-screen on platform C3
  • VacOK_MoveAllowed: if this bit is on it means the vacuum conditions are such that moving the detectors is allowed
  • Vent_Allowed: if this bit is on it means the detectors are in a position (XA=

The actual readings and a lot more can be seen at the Motion pages on the PLC-screen in rack C3B05 on platform C3. However, access to these pages is password protected.

-- EddyJans - 31 Jul 2008

Topic attachments
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JPEGjpg pvss.motionscreen.jpg r1 manage 102.6 K 2008-07-31 - 15:23 EddyJans  

This topic: LHCb > WebHome > LHCbVELO > VELOOperatingManuals > Motion
Topic revision: r3 - 2008-08-05 - EddyJans
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