UL electronic computer engineers are testing purpose-built robots which will be used to carry out an underwater study of Lough Derg, writes Anna Nolan.
Lough Derg is the scene for unusual vehicular activity this week as an autonomous robot is put through its underwater paces by researchers from the University of Limerick. Robots encounter far more difficulties in the water than they do on dry land, says Daniel Toal, director, of the mobile and marine robotics research group in the department of electronic and computer engineering at UL.
Conditions are more cluttered with rocks, plants, living creatures and sometimes wrecks. Visibility is generally clouded, and the electronic systems have to work while submersed for long periods in the water.
The UL-built robot, Tethra, is an experimental autonomous underwater vehicle (AUV). Its main purpose is for mapping and filming, but while under development it is also providing data for student researchers.
A key feature is that once released, Tethra has to be able to make its own decisions about where to go and what to do, carrying its own on-board computers to achieve this.
The task of integrating sensors that tell it where it is going, actuators that cause devices to operate, software giving rules of behaviour under a range of circumstances, and various electronic controllers and communication devices is a complex one, and so "real-life" testing is essential, says Toal.
This week's trials started from the marina in Killaloe, Co Clare, checking equipment on a pontoon first of all, and then testing in the water. "We are criss-crossing the lake in zigzag patterns," says Toal. "The lake is a good test bed, and we are mapping two areas in better detail than it has been done before. We can see stones 10cm across and ripples in the sand and mud."
The lake trials test the robot's ability to take care of itself once released, but also provide data for PhD candidate researchers involved in the project. One is focusing on control aspects of AUVs. A second is investigating issues of precision navigation requirements for high-resolution imaging and mosaicing (travelling up and back in a lawnmower fashion).
A third researcher is looking at the design of proximal object detection sensors (sonars), explained Dr Toal.
The navigation/positioning problem becomes much more acute for underwater vehicles than for surface vehicles with radio and global positioning systems reception.
"These lake tests will also provide us with a unique opportunity to evaluate and compare the imaging sonars," he said. Following the pontoon tests, the group is now deploying Tethra with its integrated precision navigation instruments at depths of 5m to 15m. A monitoring/control line providing a means of overriding the autonomous controller is being put through its paces.