"For our research, we utilize an underwater robot about the size of a beer crate. Equipped with eight electric jet thrusters, it can assume various orientations and positions in the water. Additionally, it features an underwater camera and four LED floodlights, enabling the robot to perceive its surroundings even in dark or murky waters. Furthermore, it can be expanded with sensors and devices, rendering it an intriguing experimental platform for our research. Underwater conditions differ significantly from those on land: communication via radio and navigation using GNSS satellites do not function underwater. Thus, the robot navigates and communicates acoustically through ultrasound. At our institute, we developed an open-source acoustic modem called 'ahoi,' which converts digital data like temperature or oxygen levels into acoustic signals, i.e., sound waves, for underwater data transmission.

Unfortunately, acoustic underwater communication is as slow as analog internet modems were in the past. Hence, high-resolution images are locally stored on the robot and retrieved after deployment. Instead, the robot transmits real-time position, sensor, and status data to a control station and receives destination coordinates from it.

Another challenge is the robot's power supply required for propulsion. Only a few hours of operation are achievable with a single battery charge. Charging stations—similar to those used for lawn or vacuum cleaner robots—could be deployed in buoys already used by the robot for navigation. My team has already developed an initial prototype of a buoy, albeit without a charging function. These buoys currently serve as a communication interface between the above-water and underwater worlds. For the first prototype without a charging function, we utilize a small buoy with a screw cap, similar to those used for canoeing to store valuables waterproofly. Unlike the robot, the rest of the technology is averse to water."

Further Information

Read the complete article and more in the current Spektrum (in German).

Institute for Autonomous Cyber-Physical Systems