The Core Applications of Fiber Optic Strapdown Inertial Navigation Systems in Marine Field

The Fiber Optical Strapdown Inertial Navigation System (FOG-SINS) uses fiber optic gyroscopes (FOGs) and accelerometers to form a solid-state inertial measurement unit (IMU), which calculates the motion parameters of the carrier in real time through a strapdown algorithm. Due to its significant technological advantages, FOG-SINS has become the core of the new generation of navigation systems in the field of ocean ships.

The application of FOG-SINS in the field of ocean ships is mainly reflected in ship navigation, underwater vehicle control, and multi beam measurement. Its core advantages are high precision, high reliability, strong anti-interference ability, autonomous navigation, excellent dynamic performance, and good environmental adaptability.

Ship Navigation

FOG-SINS can provide continuous and autonomous ship position, heading, attitude (roll, pitch), velocity, and acceleration information for navigation.

FOG-SINS is integrated with GNSS (GPS, Beidou, etc.), odometry (Doppler/electromagnetic), compass (magnetic/electric compass), etc. (usually through Kalman filtering) to form a high-precision and high reliability integrated navigation system. FOG SINS provides critical navigation capabilities in the event of GNSS signal interference, obstruction, or failure (such as in canyons, under bridges, electronic warfare environments).

FOG-SINS can also provides high-precision attitude reference information for shipborne weapon.

The Technical Advantages of FOG-SINS in Ship Navigation :

⚪  High precision and stability: The zero bias stability of modern high-precision FOGs can reach the order of 0.01°/h or even higher, and the angle random walk can reach the order of 0.001°/√h, which can support long-term, high-precision inertial navigation requirements and significantly reduce the accumulation speed of position errors.

⚪  Quick start and response, wide dynamic range: Short start time (much shorter preheating time than mechanical gyroscopes), fast dynamic response, and accurate capture of the ship's rapid maneuvering (such as emergency steering and collision avoidance). Capable of measuring various ship movements from extremely low to high speeds.

⚪  Strong environmental adaptability and resistance to impact and vibration: relatively insensitive to changes in marine environmental factors such as temperature, humidity, and salt spray (especially after good design and compensation), with high reliability. The all solid state structure (without mechanical rotating parts) provides strong immunity to the inherent impacts and vibrations during ship operation, with stable performance and long lifespan.

Underwater Vehicle (AUV/UUV) Control

FOG SINS, as the core component of the underwater submersible control system, is the core sensor for AUVs to achieve long-term and high-precision autonomous navigation in the absence of GNSS signals underwater. Provide position, attitude, velocity, and acceleration information.

The combination of FOG SINS, Doppler log (DVL), depth meter, magnetometer (heading assist), ultra short baseline/long baseline acoustic positioning system (USBL/LBL), gravity/geomagnetic matching navigation, etc., forms an underwater integrated navigation system, greatly improving navigation accuracy and reliability. FOG SINS is the core and foundation of integrated navigation.

FOG SINS provides high-precision real-time attitude and heading feedback for the control system of AUVs (such as rudder, thruster, attitude adjustment mechanism), achieving precise depth, height, directional navigation, and complex maneuvers (such as hovering and bottom mounted navigation). Provide a stable attitude reference for task payloads such as sonar (side scan, front view), cameras, and robotic arms to ensure data quality and operational accuracy.

The Technical Advantages of FOG SINS in Underwater Submersible Control System :

⚪  Complete autonomy: not relying on external signals, is the key to achieving true autonomous navigation underwater.

⚪  High precision (especially important underwater): High precision attitude and heading information is crucial for underwater obstacle avoidance, terrain tracking, and precise operations. Good zero bias stability can prolong the pure inertial navigation time underwater.

⚪  Anti magnetic field interference: Fiber optic gyroscopes are based on optical principles and are not affected by the complex magnetic field environment underwater (while magnetic compasses are affected).

Multi Beam Measurement System

The FOG SINS can provide motion compensation for multi beam measurement systems, which is the most core application of FOG SINS in multi beam depth measurement. Accurately measure and compensate in real-time for the attitude changes (roll, pitch, yaw) and heave movements of the measuring vessel/platform at the moment of measurement.

FOG SINS can provide accurate heading angle and position information for multi beam measurement system (usually tightly coupled with GNSS), used to determine the precise position and direction of sonar array in the geodetic coordinate system.

FOG SINS can provide accurate time reference for the entire measurement system (multibeam sonar, GNSS, motion sensors, sound speed profiler, etc.).

The Technical Advantages of FOG SINS in Multi Beam Measurement System:

⚪ Ultra high dynamic performance and bandwidth: capable of accurately and quickly measuring and responding to high-frequency movements of ships/platforms (especially heave and sway caused by short period waves), which is the key to obtaining high-quality seabed terrain data. Its dynamic response capability far exceeds traditional vertical reference units (VRUs).

⚪  High attitude accuracy: The accuracy of attitude (especially roll and pitch) directly affects the compensation accuracy of beam angle. FOG SINS can provide sub angular (<0.01 °) level attitude measurement accuracy, ensuring the accuracy of beam pointing and seabed footprint position calculation.

⚪ Tight integration and time synchronization: FOG SINS are typically designed as highly integrated measurement units (often referred to as POS MV or INS), with internal sensors (gyroscopes, accelerometers) having extremely high synchronization accuracy and the ability to achieve microsecond level time synchronization with other external sensors (GNSS, sonar), ensuring strict alignment of all data in time.

Key Products & Technical Specifications

Conclusion

Fiber optic strapdown inertial navigation system has become an indispensable core technology in modern ship high-precision navigation, autonomous operation of underwater vehicles, and high-resolution seabed terrain mapping due to its advantages of all solid state high reliability, dynamic accuracy, and multi-sensor fusion capability.

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