Vertical Steering Command With Autopilot Engaged - Honeywell SPZ-8000 Maintenance Manual

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power supply valid which monitors the internal power
supply voltages for proper operating levels.
3. B. (8) (i) ~ Vertical Steering Command With Autopilot Engaged
With the autopilot engaged, the selected flight director
vertical command is routed through the:
. Pitch Rate Limiter
Pitch Limiter
Acceleration Limiter
. Another Pitch Rate Limiter
The resultant signal is then summed with pitch rate. Pitch
rate is supplied by the IRS and is used as a damping term to
help control the speed at which the pitch maneuver will
occur. The vertical command is then pitch limited again and
then follows two paths.
The first path goes up through the activated AP ENG switch,
TCS switch, pitch bar bias switch, and then to the symbol
generator.
The second path routes the vertical command to a summing
point through a t8-degree position command limiter. The
signal is then gain adjusted and applied to a pulse width
command limiter and output servo amplifier.
The pulse width command limiter serves two functions.
First, it is the D/A converter for the servo amplifier.
Second, as a motor driver it issues a continuous string of
28 V dc pulses, at a rate of one pulse approximately every
two milliseconds. The pulse width of the pulses is
determined by the vertical command. The pulse-width command
limiter has its current limits established by a software
program contained in the "B" CPU.
The output of the servo amplifier is sent to the SM-600
elevator servo drive motor, the "A" processor current
monitor to check
for servo runaway current, and to the pitch
trim threshold sensor.
The SM-600 is a permanent magnet dc
motor that utilizes a dc tachometer for rate feedback. It
has but does not use a position feedback synchro. As the
servo motor drives to position the elevator, it also drives
the dc tach generator through mechanical coupling
(represented by a dotted line). The tach generator provides
a rate feedback signal that serves two functions.
First, it
acts as a damping term when summed with the vertical connnand
input to the pulse-width command limiter. This helps to
stabilize elevator position and minimize excessive elevator
travel.
22-14-00
Page 298.122
Aug 15/91
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