A compact underwater robot providing a safer alternative for underwater inspection, search and maintenance
Divers can face difficult and dangerous conditions when performing essential underwater inspection, search and maintenance.
Tethys Robotics’ underwater drone in Lake Zurich during a harbor inspection.
There are several technical challenges to operating an underwater robot in a lake or river, or offshore in areas of strong tides: the water is often cloudy or murky, making visibility poor, often with leaves and other objects floating or in suspension. The water can be fast flowing, and the bottom can be moving, with sediment, or small stones dragged along by the current.
Jonas Wüst, now CEO at Tethys Robotics, set out to meet these challenges following a student research project at Eidgenössische Technische Hochschule Zürich (ETH Zurich), a public university in Switzerland.
Goal was to build an autonomous underwater robot capable of being deployed in rough water with currents of up to 2 m/s. It would need to be capable of high-accuracy positioning and inspection of its immediate environment in near-zero visibility. This required a very accurate underwater navigation solution.
To meet these positioning and navigation needs for their ROV, Wüst and his team equipped their small ROV with a Nortek DVL that meets their specific requirements for achieving bottom tracking and current measurements in the most difficult conditions, securing navigational accuracy.
The DVL, or Doppler Velocity Log, is an acoustic sensor that estimates velocity in water relative to the bottom, using a long pulse along a minimum of three acoustic beams, each pointing in a different direction.
“We are now aiming for applications where we can replace divers, especially in dangerous situations. We recently had our first test with a hydroelectric plant, where the underwater robot had to hold its position relative to the ground in a river flowing at up to 1.2 m/s. It was quite a milestone to see it used in this application, and how easy it is to do inspections if you have good localization and mapping,” Jonas Wüst says.
“Wherever you have submerged infrastructure, good reliable inspection is key.”
