Inspecting the condition of dykes and other sea defense structures is typically a task for robots, working in a team and in a highly autonomous way. But if they move around across the dykes, performing tests and communicating the results for six hours a day, they use a lot of energy. University of Twente researcher Douwe Dresscher has worked on making the robot as autonomous as possible. He does this by charging mechanical energy and by introducing an innovative automatic gear box - it's a modern version of the ‘variomatic’ used in Dutch automobiles. Instead of a belt drive, like in the variomatic, two metal hemispheres are used.