Without GPS Navigation unit for unmanned aerial vehicles (UAVs)

Fraunhofer researchers have developed a compact navigation unit for unmanned aerial vehicles. This allows the position to be determined with an accuracy of less than 10 cm without GPS.

As part of the IMUcompact research project, the Fraunhofer Institute for Reliability and Microintegration IZM has developed a compact and lightweight navigation unit for unmanned aerial vehicles (UAV). The system's Inertial Measurement Unit (IMU) is essentially based on three gyroscope axes and three acceleration sensors, which enable centimeter-accurate positioning for navigation and terrain surveying without a GPS signal.

The IMU is based on an interferometric fiber optic miniature gyroscope (IFOG) developed at Fraunhofer IZM. The IFOG is characterized by high accuracy and robustness against environmental influences. It is also very compact and lightweight, making it ideal for use in UAVs.

The IMUcompact was specially developed for the needs of civil aviation. It is easy to integrate and can be used in various UAV platforms. It enables precise and reliable navigation even in difficult environments such as indoors or in poor visibility.

Absolute accuracy of less than 10 centimeters

Thanks to a newly developed assembly method, the electronic and optical components of the IMU can be arranged in such a way that a high degree of miniaturization is achieved without sacrificing accuracy. Conventional IMUs only have a resolution of 25 to 30 cm. The gyroscope developed at Fraunhofer IZM now enables an absolute accuracy of less than 10 cm. The special arrangement of the measuring components on a 3D-printed optical bench also enables high mechanical strength for industrial applications with very low weight. In addition, an application-specific circuit board was developed that is very robust and compact at the same time thanks to its design.

One of the first practical applications of the IMU is photogrammetry with UAVs. Photogrammetry is the measurement and determination of physical objects using a combination of 2D images and 3D measurement methods such as lidar. The IMU must not weigh more than one kilogram and the entire measuring system with IMU, lidar, cameras, data logger, PC and battery power supply must weigh less than five kilograms.

Drone photogrammetry for automated surveying

Possible applications of drone photogrammetry include the automated surveying of factory buildings, the technical monitoring of offshore wind turbines or automated stocktaking in agriculture and livestock farming. Drone-based photogrammetry can also make an important contribution to damage assessment in disaster areas, especially when large areas are affected by unexpected environmental events. Providers of online map services also use photogrammetric methods to create digital 3D map material, although this often still requires the cost-intensive use of aircraft or gyrocopters with appropriate measurement technology.

"As experts in the assembly and connection technology of optical fibers, Fraunhofer IZM was able to develop a demonstrator together with project partners in which the IMU was combined with a GPS system and a powerful integrated circuit to create a complete, integrated solution. This prototype is now to be optimized in a further step in order to further advance the civilian use of autonomous drone systems," say project manager Dr. Alethea Vanessa Zamora Gómez and developer Christian Janeczka, summing up the end of the project with satisfaction.

It could also be used in other carrier systems such as ships, aerospace, autonomous vehicles and even AI-based logistics networks that enable a higher degree of automation.