Vehicle navigation is an integral component of the vehicle control system and is implemented through openINS and various openSEA device interfaces. openINS provides a complete software implementation of an aided Inertial Navigation System (INS) suited primarily for unmanned underwater vehicles. The software package runs on Greensea's proprietary technology, openSEA, and is part of the foundation the Balefire control and navigation system is built upon.
openINS is the core computational engine, the true muscle, behind both commercially packaged and vehicle-integrated navigation systems. It offers a robust and scalable computational platform that utilizes the device library in openSEA to support more than 600 different devices, many of which are navigation sensors.
openINS provides a robust multi-state Kalman filter that fuses inertial measurements from the IMU with data from aiding sensors to create an accurate final solution of the vehicle's state. All vehicle state information is the result of fusing independent state measurements with inertial process samples with the exception of reference-state information such as altitude.
The following table provides a summary of the contributions to the overall navigation estimate from each sensor.
Low update rate
| Sensor | DOF Data | Limits | Units | Orientation |
|---|---|---|---|---|
| GPS | X,Y,Z | Surface Only | lat, lon | TB |
| USBL | X,Y,Z | Large Errors Low Update rate |
lat, lon | TB usbl |
| Depth | Z | High-frequency noise | m | TB dpt |
| Altimeter | Zref | High-frequency noise | m | xTB dpt |
| AHRS Compass |
Φ, θ, Ψ Φ, θ, Ψ |
Magnetometer-based | rad rad/sec |
Rb AHRS |
| IMU/Gyro | x, y, z ϕ, ϴ, ψ |
High drift Entirely dependent on initial conditions |
m/sec2 rad/sec |
Rb imu, TB< imu |
| DVL |
x dot, y dot, z dot |
Requires bottom lock Requires stable platform |
m/s m/s m |
TB dvl |
