Inspecting the condition of dykes and other sea defence 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, perform tests and communicate the results for six hours a day, they use a lot of energy. Introducing charging stations are not a very realistic scenario. Douwe Dresscher did research on making the robot as autonomous as possible. He does that by charging mechanical energy and by introducing an innovative automatic gear box: it is a modern version of the ‘variomatic’ - Du ‘pientere pookje’ - used in Dutch DAF automobilies. Instead of a belt drive, like in the variomatic, two metal hemispheres are used.
Electromotors are primarily responsible for this high level of energy consumption. They perform best at high revolution speeds and low torques, but in the walking movement, they often work at low revs and high torques in stead. By storing energy not in an electrical but in a mechanical way, the electromotors can do their job in the best operation regimen, and mechanical energy can be reused. This is what Dresscher calls Controlled Passive Actuation.