Four-legged robots are being touted as a useful tool for search-and-rescue missions, but until now they've been limited to load carrying or observation.

This is the Italian Institute of Technology's flagship quadruped robot, the HyQ. A hydraulically actuated arm has been attached to it, which can knock obstacles out of its path. Eventually they want two remotely controlled arms, creating a Centaur-like robot.

"And with the two arms the robot can be deployed to the real area where it needs to do any maintenance work or turn a valve in a rescue scenario or pick up a sample in a contaminated area or just clean up radioactive materials; there's a lot of potential future applications where manipulation is really important," said Claudio Semini, the head of the dynamic legged systems lab in the advanced robotics department at the Italian Institute of Technology.

The arm itself was designed to add dexterity, but also aid stability. "You can use it as a counter force if you apply an external force on the body of the robot. You can use the arm as a tail as well to counter the external forces," he said.

These external forces as well as the extra weight of the arm led the team to develop algorithms to stop the robot losing balance. When the algorithm is switched on the robot ignores the external disturbances and remains steady. Other institutions have developed quadruped robots, such as Spot the dog robot developed by Google's Boston Dynamics, but these are often limited in their versatility, according to the HyQ team.

"Compared to other teams in China and the US we have focused a lot on the versatility. So this platform can do many different motions ranging from very fast motions like a run or a jump. But it can also do the more careful navigation on rough terrain where we need to plan really one foothold after the next... We don't want to be the fastest or the best climber, but we want to have a machine that can do many of these motions; as in the real world, the machine will need to have many different skills."