Date: Fri, 16 Jun 2000 09:58:26 -0400
Subject: update to HETG manual insertion duration

From: Keith A Havey

Rob -
the insertion angle was smaller than you calculated.  The following writeup
describes the telemetry to watch and the sequence of events (thanks Dave).

Several conditions are required for motion to take place.  Both the 5v and
28v converters must be enabled.  The direction relay, 4HDIRB (INSR or RETR)
must be set appropriately based on the current grating position.  Assuming
the Hardware Lockout, 4HLORBX, is ENAB, the 5v converter is ENAB, and the
direction relay is correct, the Logic Enable Status Monitor, 4HENLBX, will
be ENAB.  This state indicates that motion is POSSIBLE.  If motion is
possible and the execute relay is ENAB, motion will commence.  At the
instant the end of travel limit switch is reached (4HILSB), the logic
enable is no longer satisfied, 4HENLBX will change to DISA, and motion will
cease automatically by the MCE.  Note that the execute relay is still in
the execute state and will remain in that state until commanded to the DISA
state.  Thus the state of the execute relay alone can not be used as an
indication of motion.

The best indication of motion can be gained by monitoring the back EMF when
possible.  The next best telemetry points to monitor are the logic enable
4HENLBX and the execute relay 4HENLBX.  When BOTH are ENAB, the grating is
moving.  Motion will stop when one of these goes to DISA.  Normally 4HENLBX
goes to DISA first because an end of travel limit switch is reached.  The
same mode of operation is true for *all* other grating motions.

So here's what it means for for last nights move:

As shown in the table below, the duration was 3 VCDU x 0.256 seconds = 0.77
sec

               enable logic status execute relay   inert switches
VCDU           4HENLBX             4HEXRBX         4HILSA    4HILSB
6552707        ENAB                DISA            NINS           NINS
6552708   start     ENAB                 ENAB <<<       NINS           NINS
6552709        ENAB                ENAB            NINS           NINS
6552710        ENAB                ENAB            NINS           NINS
6552711   stop DISA <<<            ENAB            INSR           INSR

The OTG moves at 0.544 deg/second, indicated a maximum travel of 0.42
degrees.  However, since the leaf spring compresses ~0.010 over a 4" radius
after the OTG is at the stops, the OTG angle traveled is less than this by
atan(0.010/4) or 0.14 degrees.

So the most likely angle error was ~ 0.3 degrees.

It would be useful if someone could look at the yaw and pitch attitude
errors at this time to see if a disturbance was seen due to the yoke
starting and hitting the stop posts.


Keith (with input from Dave and Clyde)