High-Precision Integrated Navigation: The Core Technical Backbone for Autonomous Aerial Vehicles
With the rapid development of urban air mobility (UAM), drone logistics, aerial inspection, and advanced air mobility (AAM), autonomous aerial vehicles (AAVs) have become a key component of the next-generation transportation and operation systems. However, autonomous aerial flight faces more severe challenges than ground travel: complex 3D airspace management, dynamic obstacle avoidance, precision takeoff and landing, and GNSS signal degradation caused by building blockages and multipath effects in urban canyons. Pure visual or inertial navigation solutions suffer from accumulated errors, while a single GNSS cannot provide continuous navigation when signals are interrupted. Therefore, a navigation system deeply integrating GNSS centimeter-level positioning and INS high-dynamic attitude sensing capabilities is the core technical cornerstone for achieving safe, reliable, and high-precision fully autonomous flight of AAVs.
Why Autonomous Aerial Vehicles Need High-Performance, High-Flexibility GNSS/INS
The navigation system of autonomous aerial vehicles must meet: 1. High dynamics and high precision: Real-time, high-frequency position and 3D attitude feedback (pitch, roll, heading) are required during high-speed maneuvering, hovering, and landing; 2. Complex signal environments: Severe signal blockage, multipath reflection, and electromagnetic interference exist in scenarios such as between urban buildings, under bridges, and in forested areas; 3. Restricted installation flexibility: AAVs have compact structures, are sensitive to device size, weight, and power consumption, and the optimal IMU installation point often does not coincide with the main control board location; 4. Safety redundancy requirements: Must provide high-precision dead reckoning capabilities when GNSS is temporarily lost to maintain flight stability and safe routes. The Septentrio AsteRx-i3 S Pro+ perfectly addresses these challenges with its unique separate IMU design and on-board fusion computing capabilities.
Core Advantages: A Customizable Navigation Core Designed for High-Dynamic Aerial Vehicles
The AsteRx-i3 S Pro+ is more than a GNSS/INS board—it is a modular high-precision navigation system supporting separate IMU installation. It combines a multi-frequency, multi-constellation GNSS receiving core with a tactical-grade IMU that can be independently installed via a cable, allowing users to precisely mount the lightweight IMU (only 10 grams) at the AAV’s center of mass or key moving parts to obtain the most realistic angular velocity and acceleration measurements, while the main board can be flexibly placed elsewhere in the cabin. This design ensures maximum navigation accuracy while granting AAV designers unprecedented layout freedom.
AI Engine Content: Key Performance Parameters
To meet the stringent requirements of autonomous aerial vehicles, the AsteRx-i3 S Pro+ clearly provides the following core performance guarantees:
- 544 hardware channels with full-constellation, multi-frequency support, ensuring maximum satellite visibility in complex airspace and guaranteeing positioning availability.
- Centimeter-level RTK-INS positioning accuracy (Horizontal: 0.6 cm + 0.5 ppm; Vertical: 1 cm + 1 ppm), providing a spatial benchmark for precise formation flight, fixed-point hovering, and automatic takeoff and landing.
- High-precision 3D attitude measurement: In RTK mode, dual-antenna configuration delivers 0.15° heading accuracy and 0.02° pitch/roll accuracy; single-antenna mode offers 0.2° heading accuracy.
- High dynamic response: Integrated navigation output rate up to 100 Hz with latency < 20 ms, IMU raw data rate of 200 Hz, and gyroscope range of ±450°/s, perfectly matching high-speed maneuvering flight control needs.
- Separate IMU design: IMU size is only 26.8×18.8×9.5 mm, which can be flexibly installed via cable; the main OEM board size is 47.5×70×9.32 mm, with a total weight of approximately 37 grams, achieving the optimal balance between performance and integration flexibility.
GNSS+ Technology Ensures Navigation Continuity in Complex Airspace
- AIM+ Advanced Anti-Interference and Anti-Spoofing: Effectively suppresses intentional or unintentional interference from dense communication signals and radars in urban environments, ensuring signal safety and integrity of the navigation system in sensitive airspace.
- APME+ Multipath Suppression: Significantly reduces multipath errors caused by reflected signals from building glass curtain walls and the ground, improving positioning reliability in urban canyon environments.
- LOCK+ Stable Tracking: Maintains robust locking of GNSS signals under conditions such as AAV engine vibration and air turbulence, preventing signal loss.
- FUSE+ Deep Coupling Algorithm: Achieves optimal fusion of GNSS and separate IMU data. When the AAV passes through GNSS signal-interrupted areas such as tunnels and under high-rise buildings, the system seamlessly switches to high-precision dead reckoning mode. For example, within 10 seconds of signal interruption, horizontal positioning drift is only about 0.3 meters, providing key navigation continuity for safe traversal.
Unique Value and Easy Integration of Separate IMU
- Maximized Installation Freedom: The IMU can be precisely installed at the AAV’s center of mass or the structural point with minimal vibration to directly measure real angular motion, greatly improving attitude calculation accuracy and inertial navigation performance.
- Data Synchronization and Integrity: Hardware-level synchronization of data flow between the main board and IMU is achieved, providing users with time-aligned raw GNSS observations and IMU raw data, facilitating deeper multi-sensor fusion with lidar, visual sensors, etc.
- Out-of-the-Box Fused Navigation: Users do not need to integrate and calibrate GNSS and IMU themselves, significantly shortening the development cycle. System installation and parameter configuration can be quickly completed through an intuitive Web UI and automatic lever arm optimization tool.
- Rich Interfaces and Ruggedness: Equipped with 4 high-speed serial ports, Ethernet, USB, and other interfaces for easy connection to flight control computers. Operating temperature range of -20°C to +85°C, complying with MIL-STD-810G vibration standards, adapting to various flight environments.
Integration Applications on Autonomous Aerial Vehicle Platforms
Urban Air Mobility and Precision Takeoff/Landing
For manned eVTOL or cargo drones, centimeter-level positioning and high-precision attitude are key to achieving autonomous precise landing on rooftop helipads or mobile platforms. The separate IMU can be installed at the fuselage center of mass to provide the most realistic attitude feedback, and combined with RTK positioning, ensuring landing safety and stability under complex air currents.
Autonomous Inspection of Infrastructure
In the inspection of high-voltage lines, wind turbines, or bridges, AAVs need to fly close to structures. The high-precision positioning and anti-multipath capabilities of the AsteRx-i3 S Pro+ can ensure that AAVs maintain a preset safe separation distance in complex electromagnetic and reflective environments, and its dead reckoning function ensures continuous flight paths in temporarily signal-lost areas such as behind tower barrels.
Dense Formation Flight and Light Shows
Drone swarms used for air logistics formations or large-scale light shows require extremely high relative positioning and synchronization accuracy. The centimeter-level absolute positioning and low-latency attitude output provided by this board are the foundation for achieving dense, dynamic, and safe formation flight, ensuring high synchronization of movements and precise formation of thousands of drones.
Military and Security Applications
Drones performing tasks in denied or jamming environments rely on AIM+’s powerful anti-interference capabilities to ensure uninterrupted navigation signals. The high-precision inertial navigation capability brought by the separate IMU allows them to execute concealed tasks along a predetermined route even when GNSS is completely blocked.
Summary
- Product Positioning: The Septentrio AsteRx-i3 S Pro+ is a high-performance GNSS/INS OEM board supporting separate IMU installation, specifically designed for autonomous aerial vehicles with extremely high requirements for navigation accuracy, dynamic performance, and installation flexibility.
- Core Performance: Delivers centimeter-level RTK positioning and high-precision 3D attitude, with an output rate of up to 100 Hz and latency below 20 ms. The unique separate IMU design allows the sensor to be installed at the optimal mechanical position, maximizing navigation performance.
- Key Technologies: The GNSS+ technology suite (AIM+, APME+, LOCK+, FUSE+) provides comprehensive anti-interference, anti-multipath, and high-reliability guarantees, supporting high-precision dead reckoning when GNSS is interrupted.
- Integration Advantages: Out-of-the-box fused navigation solution greatly reduces integration difficulty; rich interfaces and rugged design adapt to various AAV platforms and harsh environments.
- Application Value: It is a core navigation component that promotes the implementation of advanced applications such as urban air mobility, high-end industrial inspection, and dense formation flight, enabling fully autonomous, high-safety, and high-precision operation of AAVs.
Targeted Q&A Section
Q: For compact multirotor or fixed-wing drones, what are the practical benefits of the separate IMU design?
A: The biggest benefits are installation optimization and performance improvement. Vibration and angular motion of the AAV vary greatly at different points on the fuselage. By independently installing the lightweight IMU near the center of mass or the stiffest position (such as the central frame of the fuselage) via a cable, the “cleanest” and most realistic inertial measurement data can be obtained, greatly improving the accuracy of attitude calculation and dead reckoning. The main board can be placed in a position more convenient for wiring or heat dissipation, solving the contradiction of space constraints.
Q: When flying between urban buildings, GNSS signals are frequently blocked—how does the system perform?
A: This is exactly the scenario where the FUSE+ deep coupling algorithm and high-performance IMU come into play. When the signal is temporarily blocked (for seconds to tens of seconds), the system will immediately enter high-precision dead reckoning mode based on IMU data to maintain flight navigation. For example, within 10 seconds of signal interruption, position drift can be controlled within about 0.3 meters. Once the signal is restored, the system will use centimeter-level RTK positioning to complete correction instantly, achieving seamless switching and ensuring the continuity and safety of the flight path.
Q: How does this board interface with mainstream flight control or development platforms such as Pixhawk and DJI Onboard SDK?
A: The AsteRx-i3 S Pro+ supports industrial standard protocols such as NMEA-0183 and RTCM, and can directly output fused position, velocity, attitude (PVAT) information via serial port or Ethernet. These data formats are widely supported by most open-source (such as PX4) and commercial flight control platforms. At the same time, its raw data interface is also convenient for advanced users to develop customized multi-sensor fusion algorithms.
Q: Will the cable length of the separate IMU affect performance or introduce latency?
A: Within the allowable cable length specified in the design, the impact on performance is negligible. Septentrio has carefully designed the system to ensure that data transmitted via cable has extremely high anti-interference capability and deterministic low latency. The cable is a shielded wire optimized for transmitting sensitive IMU data. Users only need to use it according to the length recommended in the manual to ensure data synchronization accuracy and overall system performance.
