Observing Operations | Reviews | Survey Management

SDSS Interlock Motion Interlock System Test Report
John Anderson, Jr.
August 19, 2003

The telescope motion control interlock system was tested on July 30 - 31, 2003. The system was tested by intentionally causing a known system violation and monitoring for the correct response. The test results reference the MCP encoder values converted to fractional degrees.  The following is a list of the interlock items tested and the actual trip point observed.

E-Stop Switches

The following e-stop switches were tested to ensure the telescope and windbaffle Azimuth, Altitude, and Rotator amplifiers all trip off inhibiting all motions.

Control Room
North Lower Level
South Lower Level
East Lower Level
West Lower Level
North Rail
South Rail
East Rail
North Windbaffle
South Windbaffle
East Side North Fork
West Side North Fork

Altitude Motion Interlocks

Down Limits
Stow Position < 6.6 degrees
Azimuth in stow position.
     Soft limit 1.4 degrees, hard limit 1.1 degrees
15 Degree stop extended.
     Soft limit 15.1 degrees
Building off, not at stow.
     Soft limit 21.7 degrees, hard limit 17.5 degrees.
Building on (azimuth > 110 and < 130, but not at azimuth stow)
     Soft limit 83 degrees, hard limit 82.6 degrees
Flat Field Screens open at stow position
     Soft limit 5.5 degrees

Up limits
     Soft limit 91.2 degrees, hard limit 92.0 degrees

15 Degree stop extends at 18 degrees and retracts at 17.5 degrees

Azimuth Motion Interlocks

Stow A Position Not verified
Stow B Position Not verified
Stow Center Switch Position Not verified
Building Clear or Alt > 83 degrees
     CCW soft limit 402 degrees, hard limit 412 degrees
     CW soft limit -161 degrees, hard limit -170 degrees
Building On alt > 21.7 degrees and < 83 degrees
     CCW soft limit 110 degrees, hard limit 109 degrees
     CW soft limit 131 degrees, hard limit 132 degrees

Rotator Motion Interlocks

Instrument Change Position +/- 5.0 arc minutes
CCW soft limit 369 degrees, hard limit 379 degrees
CW soft limit -190 degrees, hard limit -200 degrees

Untested Items

The azimuth, altitude, and rotator motor over temperature interlocks were unable to be tested. The over temperature interlock is a calculation internal to the PLC to determine the resistance of each motor based on the motor voltage and current values. A change in motor resistance below 2 ohms indicates an over heated motor. There was no obvious way to generate I and V values from the amplifiers to generate an over-temp trip.

The slip detection interlocks were not tested. However, we found that the slip detection system would also trip with most hard limit trips.

Each individual flat field screen was not tested to the summation point as the windscreen was not installed on the telescope. The summation output from the flat field screens was tested with the altitude motion interlock tests.

The Azimuth stow position was not verified.

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