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2. The Vertical Motion Simulator
General Description
The Vertical Motion Simulator (VMS) (ref. 45) at NASA
Ames Research Center was used in all of the experiments
reported herein. It is the world’s largest flight simulator.
A cutaway view of the motion system and its position,
velocity, and acceleration limits are shown in figure 6. It
is an electrohydraulic servo system, with a payload of
140,000 lb. This payload is pneumatically counterweighted
with pressurized nitrogen. Both the vertical and
lateral translational degrees of freedom are driven with
separate electric motors in a rack-and-pinion arrangement.
The remaining degrees of freedom are hydraulic.
NASA
Ames
VMS Nominal Operational Motion Limits
Axis
Vertical
Longitudinal
Lateral
Roll
Pitch
Yaw
±30
±20
±4
±18
±18
±24
16
8
4
40
40
46
24
16
10
115
115
115
Displ Velocity Accel
All numbers, units ft, deg, sec
Figure 6. Vertical Motion Simulator.
Five interchangeable cockpits are available from which
to choose for each experiment. Each cockpit has a different
window layout and can have a different stick, instruments,
and visual system image generators. Thus, these
characteristics are described separately for each experiment.
Performance Characteristics
The dynamic performance of the VMS depends on the
axis. Using frequency-response testing techniques
(ref. 46), the dynamics of the yaw rotational, longitudinal,
lateral, and vertical translational axes were fitted
with equivalent time delays (that is, the phase response
was approximated as a pure time delay) as shown below.
Equations (2) and (3) are taken from previous work
(ref. 47).
˙˙
˙˙
( ) y .
y
sim
com
s » e-0 13s (1)
˙˙
˙˙
( ) . x
x
sim s e
com
» -0 17s (2)
˙˙
˙˙
( ) . y
y
sim s e
com
» -0 13s (3)
˙˙
˙˙ ( ) . h
h
sim s e
com
» -0 14s (4)
The subscript sim refers to the actual simulator
acceleration, and the subscript com refers to the
commanded simulator acceleration. Only these four
degrees of freedom are listed because the other two degrees
of freedom were not used in this work.
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3. Yaw Experiment
Background
Research in the yaw axis has been sparse and
inconclusive. Meiry, in the first detailed investigation into
the effects of yaw rotational motion, found that adding the
motion was beneficial (ref. 22). The study indicated a
reduction in pilot time delay of 100 msec, with a
concomitant improvement in performance. In contrast,
two studies that examined a pilot’s ability to perform
hovering flight tasks with a representative vehicle model
found little or no effect of yaw rotational platform motion
on pilot-vehicle performance or on pilot opinion
(refs. 48, 49).
In the latter studies, the variations in yaw rotational
platform motion ranged from no-motion to full-motion,
where full-motion refers to a platform that moves the
same amount that the math model moves. Pilots were
intentionally located at the vehicle’s center of rotation and
only experienced the rotational motion cues associated
with the vehicle yaw motion. Thus, the translational
accelerations typically produced by yaw motion, when the
pilot is displaced from the center-of-rotation, were absent
by design. The tasks were target tracking in the presence
of an atmospheric disturbance and heading captures. These
results suggested that the usefulness of the yaw degree of
freedom be explored further.
The purpose of the study described in this section is to
extend the previous research and, more specifically, to
determine if yaw platform motion has a significant effect
on pilot-vehicle performance and pilot opinion in situations
more representative of flight. If yaw platform
motion is unnecessary, then a savings might be realized
from a reduced level of complexity in the design, development,
and operation of flight simulators. In addition, the
actuator displacement usurped by the yaw degree of
freedom could be made available for more useful
displacements in other degrees of freedom.
First, the experimental setup is described, which includes
the three piloting tasks, the vehicle math model, the
simulator cueing systems, and the motion system
configurations that were evaluated. This description is
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