MEMS attitude and heading reference systems are the core component in marine exploration and navigation

Underwater navigation is essentially a systems engineering challenge involving combating errors and uncertainties. Under multiple constraints such as GNSS denial, curved trajectories, error accumulation, and intermittent sensor failures, no single navigation method can meet the requirements for long-term, high-precision, and highly reliable operation. Multi-sensor fusion is not an option, but the only feasible technological path.

Challenges of Underwater Navigation:

1. Complexity of underwater sound propagation. The speed of sound in seawater is affected by temperature, salinity, and depth, resulting in sound ray bending effects that cause significant errors in traditional positioning methods that assume straight-line propagation.

2. GNSS signal failure. The absence of GNSS signals underwater means that navigation systems must rely on inertial or other alternative solutions. Underwater GNSS requires seabed base stations and acoustic communication, establishing a complex and expensive infrastructure network that is difficult to maintain.

3. Accumulation of inertial navigation errors. Inertial navigation systems (INS) have high short-term accuracy, but errors increase exponentially over time, limiting long-term positioning accuracy and requiring real-time correction through external sensors.

4. Real-time challenges of acoustic communication. Underwater acoustic communication faces problems such as high latency, narrow bandwidth, and high error rates, limiting the real-time transmission of positioning data. Even short-distance communication can experience delays of hundreds of seconds, affecting navigation accuracy in dynamic scenarios.

5. Limitations of Doppler Velocity Log (DVL). DVL relies on seabed topography and is prone to failure in high-current environments or turbid waters, leading to navigation terminal failure. Studies show that tightly coupled navigation systems can provide high-precision positioning when more than one beam of the DVL returns valid information, while loosely coupled systems require at least three valid beams.

6. Environmental adaptability requirements pose a severe challenge to underwater navigation equipment. Underwater equipment needs to withstand harsh environments such as high pressure, salt spray corrosion, and wide temperature variations.

Application of MEMS attitude and heading reference systems in underwater vehicles

When navigating in complex marine environments, underwater vehicles require precise attitude control and heading reference to ensure accurate mission execution. High-precision attitude and heading data provide the underwater vehicle's control system with stable and reliable attitude information, enabling it to maintain stable operation under various maneuvering conditions.

Taking the HTS-AHRS-74 attitude and heading reference system as an example, the product is typically installed on the main structure of the underwater vehicle.  Through multi-sensor data fusion algorithms, it provides real-time attitude and heading angle data of the vehicle. The processed attitude and heading data are input into the control system to adjust the thrusters or rudders, maintaining the underwater vehicle's stable navigation state. Especially when the underwater vehicle performs high-precision tasks, such as seabed terrain mapping and underwater target recognition, the high-precision attitude and heading data from the HTS-AHRS-74 significantly improves the accuracy and reliability of mission execution.

Furthermore, the high-pressure adaptability of the HTS-AHRS-74 enables it to support underwater vehicle operations in deep-sea areas. In deep-sea environments, the water pressure is extremely high, making it difficult for ordinary electronic equipment to function properly. However, the HTS-AHRS-74, through special packaging technology and internal structural design, can maintain stable operation in a high-pressure environment of 8.9 MPa, providing continuous and reliable attitude and heading reference for the underwater vehicle. The HTS-AHRS-74 also supports integration with other navigation devices such as DVL and USBL, forming a combined navigation system. This integration effectively suppresses the error accumulation of a single sensor, improving overall navigation accuracy. For example, in long-duration underwater vehicle missions, the combination of the HTS-AHRS-74 attitude and heading reference system and DVL can keep positioning errors at a low level, meeting the navigation needs of the underwater vehicle.

In fields such as marine exploration, underwater unmanned platforms, and national defense security, navigation systems are evolving from "functional modules" to "intelligent sensing cores." High-performance, high-precision MEMS attitude and heading reference systems provide a stable, accurate, and reliable attitude reference. This enables the engineering implementation of complex multi-source tightly coupled fusion algorithms, thereby empowering various platforms with continuous, reliable, and precise spatiotemporal perception capabilities in uncertain underwater environments.