AHRS400 Series User’s Manual
Doc# 7430-0004-01 Rev. A Page 5
3 AHRS Details
3.1 AHRS Coordinate System
The AHRS 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. An
acceleration is positive when it is oriented towards the positive side of the
coordinate axis. For example, with the AHRS 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.
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 AHRS 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 rates, and the z-axis sensor would measure a positive angular
rate.
The magnetic sensors are aligned with the same axes definitions and sign as
the linear accelerometers.
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). Yaw is defined as positive for a positive rotation around the z-axis
(turn 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, and
then yaw.
3.2 Connections
The AHRS400CA has a female DB-15 connector, whereas AHRS400CB
and AHRS400CC have a male DB-15 connector. The signals are as shown
in Table 1.
SUNSTAR传感与控制 http://www.sensor-ic.com/ TEL:0755-83376549 FAX:0755-83376182 E-MAIL:szss20@163.com
SUNSTAR自动化 http://www.sensor-ic.com/ TEL: 0755-83376489 FAX:0755-83376182 E-MAIL:szss20@163.com
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