Just when you thought you had seen every type of robot locomotion possible, the Universidad Politécnica de Madrid comes along and shows you another one. This time it's a ball that rolls around the ground as if it had a hamster inside.

Likening ROSPHERE to a hamster ball is more than just a good headline. The mechanism by which it moves about really is like having a hamster move around inside. A heavy weight is suspended below the center of the ball and a motor uses it to turn an axle inside the sphere. It is a simple and completely self-contained propulsion system. It is capable of not only straight line motion, but by altering the angle of swing it can roll along a curved path.

The Robotics and Cybernetics Research Group from the Universidad Politécnica de Madrid is interested in creating a robot that can cope with uneven surfaces and even ploughed fields. ROSPHERE is designed essentially to roll in the dirt and gather data on the plants that are growing there. You can see that it is ideal for rolling along lines of plants - not so sure about it turning round at the other end of the line and moving up another row.

The team has plans to use it in other applications and has even run it in Parque del Retiro in Madrid to see what people make of it.

You can see it in action in this video: 

An even more convincing video shows ROSPHERE on the beach in Valencia:

Any similarities to the spherical guard in the classic/cult TV series "The Prisoner" are entirely spoiled by scale. 

Two final thoughts - we have to hope that people don't think that there really is a hamster inside and try to rescue it; and this would make a really good toy for humans.