Use Case:  Close Enclosure On Bad Meteo Conditions

Description:  This is a monitor function that checks the Meteo Conditions (Wind/Humidity/Temp dew point etc...) against given limits and accordingly closes the AT Enclosure
On Wind Speed > 18m/s, AMOS PLC handles automatically the closing of the enclosure.
This UC uses Close Enclosure

Role(s)/Actor(s): 
Secondary: ASM,Axis,Enclosure

Priority: Critical.

Performance: 2 minutes

Frequency: At any time.

Package Assignment:  Enclosure Subsystem.

Preconditions: 

• Enclosure sub-system is ready to receive commands

Basic Course: 

• ATCS queries Meteo Conditions from ASM but local wind speed
  Exception Course: Command failed
  Postcondition: Meteo Conditions available
• ATCS queries local wind speed from AT anemometer
  (see UC Monitor Enclosure Anemometer)
  Exception Course: Command failed
  Postcondition: local wind speed available
• ATCS checks Meteo Conditions against limits
  Exception Course: Meteo OK
• ATCS Closes Enclosure
  Exception Course: Command failed
  Postcondition: Enclosure closed
• ATCS Stops Telescope Motion
  Exception Course: Command failed
  Postcondition: Telescope is standstill, brakes released, control loops are closed

Exception Course: Meteo OK

• No action
  

Exception Course: Command failed

• ATCS raises an alarm
• ATCS returns ERROR reply
  Postconditions:
  • Query Failure : Meteo data not available
  • Close Failure : Enclosure is not or partially closed
  • Telescope Failure : Telescope error

Postconditions: 

• Enclosure is closed
• Enclosure seals are inflated
• Telescope is standstill, brakes released, control loops are closed

Issues to be Determined or Resolved: 

Notes: In order to avoid racing conditions, ATCS wind speed limit shall be lower than the AMOS PLC limit value (e.g. 15m/s). This would garanty that ATCS first sends the command to close the enclosure before the PLC does it. One could align on wind speed limit as of UT1.

Last modified: Thu Jun 28 13:10:44 UTC 2001