Moog Crossbow VG700MB Series - Manual (Page 11)

VG700M User’s Manual
Doc.# 7430-0280-01 Rev. F Page 5
3 DMU Details
3.1 DMU Coordinate System
The DMU will have a label on one face illustrating the DMU coordinate
system. With the connector facing you, and the mounting plate down, the
axes are defined as:
X-axis – from face with connector through the DMU.
Y-axis – along the face with connector from left to right.
Z-axis – along the face with the connector from top to bottom.
The axes form an orthogonal right-handed coordinate system. Acceleration
is positive when it is oriented towards the positive side of the coordinate
axis. For example, with the DMU sitting on a level table, it will measure
zero g along the x- and y-axes and +1 g along the z-axis. Gravitational
acceleration is directed downward, and this is defined as positive for the
DMU z-axis. In a typical installation, this will require the system to mount
with the connector facing aft.
The angular rate sensors are aligned with these same axes. The rate sensors
measure angular rotation rate around a given axis. The rate measurements
are labeled by the appropriate axis. The direction of a positive rotation is
defined by the right-hand rule. With the thumb of your right hand pointing
along the axis in a positive direction, your fingers curl around in the
positive rotation direction. For example, if the DMU is sitting on a level
surface and you rotate it clockwise on that surface, this will be a positive
rotation around the z-axis. The x- and y-axis rate sensors would measure
zero angular rate, and the z-axis sensor would measure a positive angular
rate.
Pitch is defined positive for a positive rotation around the y-axis (pitch up).
Roll is defined as positive for a positive rotation around the x-axis (roll
right).
The angles are defined as standard Euler angles using a 3-2-1 system. To
rotate from the body frame to an earth-level frame, roll first, then pitch,
then yaw.
3.2 Connections
The VG700M has a male 22-pin circular connector. The signals are as
shown in Table 1.