tiedown 4 loud noises oct11
Loud noises were heard on the tiedown audio
monitors on 27oct11 and again on 29oct11. The sounds were coming from
tiedown 4 (td4). Plots were made of the td4 status during the loud
- The data is sampled once a second.
- Colors: black:td12,red:td4,green:td8
- Top: tiedown position vs hour of day.
- 2nd: velocity feedback of voltage sent to the amps.
- pink: td4 commanded velocity
- 3rd: amplifier speed. read back from the amplifier.
- 4th: drive status: 0=off, 1=enabled,2=powered (but
- bottom: motor drive current.
- 27oct11 01:17 (1.234hrs) (.ps)
- The leftmost dashed vertical line is when the operator reported
the noise (this is not exact..).
- The rightmost vertical flags are when the operator stopped the
- Note how the red readings are jumping up and down rapidly (on
the order of 1 second).
- The pink commanded velocity (in frame two) is the requested
velocity. It is smooth since the pI loop has a long time constant.
This implies that the red readings jumping around are not
requested by the cpu.
- This could be a problem with the readback (interference) or
it could be real.
- look at the flagged region: 1.317 to 1.322:
- The velocity feedback continues to jump around
- the speedmonitor readback and torque readback is no longer
- This shows that the problem is not with the readback. When
the motors were turned off, the problem with the speed and torque
readback went away (as they should have if the motor was off). The
velocity feedback continued to jump (since it is set by the dac,signal
conditioning output board.
- 29oct11 05:21 (5.35 hrs)
- page 1: 0 to 6 hours. You can see the problem in the torques,
speed monitor around 5.35 hours.
- Page 2: blowup around the problem.
- The vertical flags show the time around the noises.
- The velocity feedback, spdmonitor,torques are jumping around
during this period.
- The requested velocity (frame 2 pink is smooth during this
- At 5.362 the operator turned off the motor.
- the amplifier speed and the torques started jumping around.
- the velocity feedback continued to jump around
- On 27oct11 and 29oct11 loud noises were heard from td 4.
- During the loud noises the velocity feedback, motor speed, and
motor torque were jumping around at the one second level.
- The requested velocity was smooth during this period.
- Once the motors were turned off the speed and torque stopped
jumping around. The velocity feedback continued to jump
- This is a problem with the dac or dac signal conditioning
board, or the little star.
- Td 4 may have problems with the jack screw, but the values
would not jump around at the one second level since the PI loop
has a long time constant..
- The speed monitor, torque readback jumping around stopped when
the motor was shut off so the problem is not rfi on the readback.
- These were the only two occurrence of this problem on these two
days so the problem is intermittent.