Moog Crossbow GNAV540 - Manual (Page 21)

GNAV540 User Manual
7430‐0808‐01 Rev. B Page 21
Chapter 2. GNfAV540 Functions
This chapter provides an overview of the hardware and software systems of the GNAV540 unit, and the functions
provided.
• GNAV540 System, page 21
•
ions Configuring GNAV540 Funct
•
, page 21
Software Structure, page 22
• dinate System GNAV540 Default Coor
•
, page 24
IMU Function, page 25
• Function Vertical Gyroscope (VG)
•
, page 26
AHRS Function, page 29
• NAV Function, page 31
GNAV540 System
GNAV540 is a compact MEMS based GPS/inertial navigation system. It delivers continuous GPS position, true
heading and vehicle attitude tracking information for ground tactical vehicles and other platform navigation
applications. The system integrates advanced MEMS inertial gyros and accelerometers, embedded or optional
remote 3‐axis magnetometer, a SAASM or C/A code GPS receiver, and 10/100 Ethernet interface in a fully sealed
enclosure for tactical vehicles operating in combat or homeland security environments.
Figure 1 on page 22 shows the GNAV540 system configuration block diagram. To maximize system performance
and reduce cost, the GNAV540 provides RS422 interfaces for an external magnetometer and a SAASM GPS receiver:
interface to pre‐existing equipment. The internal GPS receiver is the Rockwell Collins Polaris Link card.
Configuring GNAV540 Functions
Base on d the User Behavior settings, the GNAV540 can be configured to fulfill various functions.
1. Using only the calibrated sensor data, the GNAV540 functions as an Inertial Measurement Unit (IMU) to
output angular rates and accelerations.
2. Incorporating the gyroscope and accelerometer data with the EKF, the GNAV540 can output roll and pitch
attitude information, functioning as a Vertical Gyroscope (VG) unit.
3. Building on the VG function and combining magnetic field measurement, the GNAV540 can function as an
Attitude Heading Reference System (AHRS): provide a heading angle estimate in addition to the (VG) roll
and pitch. The GNAV540 is provided with an internal magnetometer; an external magnetometer can be
integrated with the unit and configured to override the internal magnetometer.
4. Combining GPS sensor data into the EKF, the GNAV540 can provide a complete attitude system, as well as
outputting 3D velocity and position measurements, thereby functioning as a Navigation unit (NAV). An
internal C/A code GPS receiver is provided; an external SAASM GPS receiver can be integrated with the unit
and configured to override the internal receiver.
he following sections provide details about the system level and functional operations of the GNAV540. T