02/3mar06 td12 encoder trouble
On 02mar06 about 23:36, tiedown
12 released. The plots show what
the tiedowns did (.ps) (.pdf):
The tiedown position was reported incorrectly starting
at 23.6 hours (23:36). The jump from 14 inches to 24 inches took 1 second
so it was an error in the encoders, not an actual movement of the tiedowns.
The feedback loop tried to bring the tiedown back down but the encoder
reading was not changing. You can see occasional position values where
the encoder reading was correct. Eventually the tiedown got to 2 inches
(fully extended) where it hit a limit switch and was stopped (23.65).
Eventually the encoder reading corrected itself (about 23.66). It sat there
till 23.72 (23:42) when it started to move back to the default position
(this is when the operator commanded the tiedown to move back).
top: tiedown position versus time. The black trace is td12.
2nd: the velocity feedback of the D/A.
3rd : the amplifier speed monitor
4th the drive status
bottom: the drive current
Page 2 is a blowup of when the problem occurred.
The platform was tilted from 23:36 thru 23:45.
On 03mar06 around 12:34 pm td12
again jumped to 24 inches (.ps) (.pdf):