Photos: Robots battle to tackle the aftermath of a nuclear meltdown

Here a ground robot moves towards a building called Torre del Sale, which was playing the role of a damaged nuclear reactor in the recent euRathlon Challenge in Piombino, Italy.

In the competition autonomous and semi-autonomous machines battle and cooperate in activities such as surveying and mapping an area, locating and identifying targets, performing tasks like closing leaking valves.

Several teams from all over Europe competed in a scenario that simulated a Fukushima-like catastrophe. Giant waves had just damaged a nuclear reactor, radioactive material was leaking into the air and into the sea, while some of the plant's workers were missing.

This flying robot has been designed by team ICARUS, an EU-funded project with partners from Belgium, Germany, Poland, Portugal and Spain.

Flying robots tend to be very fragile but some teams participating in euRathlon - organized by the NATO's Centre for maritime research and experimentation located in La Spezia, Italy – coped well with flying in high winds.

The goal of the euRathlon Challenge is to advance progress towards robots that could be deployed in place of humans in dangerous situations like the one that hit Japan in 2011. For that reason - unlike similar events, such as the famous DARPA Challenge - participating teams have to perform in three different domains: in the air, water and on the ground.

A SPARUS underwater autonomous vehicle is seen here in competition. These robots were developed by Spain's University of Girona's team. One of the main features of SPARUS, which weights about 50kg (110lb), is that it is easily reconfigurable.

The teams taking part to euRathlon - which were assembled by university labs and private companies - could compete in single-domain contests but could also measure themselves against one another in the final multi-domain competition, the Grand Challenge.

For that purpose they could partner with other participants, so machines designed for different environments could cooperate with shared goals.

The building called Torre del Sale, or Salt Tower, acted as the damaged nuclear reactor. Robots had to enter the building and close some leaking valves. Underwater vehicles had to perform the same task under the sea, sometimes in coordination with their ground counterparts.

"One of the main aims of the challenge is to foster cooperation between different kinds of robots," euRathlon Grand Challenge technical director Gabriele Ferri said. "As the Fukushima disaster showed, you need a platform with humans and robots specialized in different fields and able to act autonomously and to collaborate."

Here is one of the ground robots brought to Piombino by team ICARUS, which was one of the few teams to design robots for air, water and ground.

ICARUS's drones received a special award for their autonomy. The robots participating in euRathlon displayed various level of autonomy, because the competition rules allowed the teams to decide how much control humans could exert over the machines.

"Teams were free to choose whether to tele-operate but would receive more points if the let the robots act by themselves," euRathlon Grand Challenge technical director Gabriele Ferri said.

This flying robot was assembled by ISEP/INESC TEC, one of the teams that won the euRathlon Grand Challenge by linking up with team Cobham of Germany for ground vehicles and University of Girona from Spain for underwater vehicles.

"Our coordination was done using radio between the different control stations. It was mainly talk between the partners to let the others know how far you are on with the exploration of your area, as well as to inform them of what you have found so far," University of Girona's Alberto Palomer said.

Before the beginning of the challenge, the teams were allowed to test their underwater robots in a pool. Perception and localization are the two fundamental issues that robots have to overcome to be autonomous underwater.

Unlike most teams, team ICARUS brought several kinds of robots, each capable of working in different fields. Here's one designed for the ground. The mechanical arm was used to close the valves that in the simulated scenario were supposed to leak radioactive materials.

Here you see engineers from the UK's Team Nessie - the Ocean Systems Laboratory and Heriot Watt University - working with an underwater autonomous vehicle.

A joystick used to control the robots. One of the aims of euRathlon is to promote more autonomous vehicles. But teams were allowed to use controllers for certain tasks at the cost of some points.

The underwater autonomous vehicles taking part to euRathlon were equipped with engines. In this case the vehicle used two small propellers.

Water conditions can affect the robots' performance and forced some teams to adjust on the fly. For instance, underwater vehicles that relied on cameras for vision were in trouble since visibility on site was less than one meter.

Here, the teams test their vehicles in a pool before the beginning of the challenge.

Localization underwater is difficult because technologies such as GPS are not available. Plus, underwater sensors are not as precise as ground ones. If visibility is poor, the robot has to rely mainly on sonar.

This is a mechanical arm used by a ground robot. Arms were generally used to complete tasks such as closing leaking valves but could be adopted for different goals.

For instance, the ground robot designed by team Bebot from the University of Bern, Switzerland, overcame the communication problem in a complex environment by building its own network on the fly.

While on its way to the reactor, the machine used its mechanical arm to deploy antennas along the route so its engineers could operate the robot and get feedback even without a direct line of sight.

The multi-domain euRathlon Grand Challenge competition was won by team Cobham in the grey and red shirts, ISEP/INESC TEC in green and the University of Girona in blue. The three groups teamed up just before the beginning of the race and cooperated to accomplish the required task.

"The aerial [ISEP/INESC TEC aerial team] and land [Cobham] partners were really fast at informing us of the leaking pipe and also the missing worker," University of Girona's Alberto Palomer said.

"In our case, we had to tell Cobham which pipe was leaking to close the appropriate valve in the machine room. Once both vehicles were on the correct spot, the valves where closed synchronously."