The robot's drive train, including the dual-hemisphere system. (Image: University of Twente)

Inspecting the condition of dikes 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 dikes, perform tests, and communicate the results for six hours a day, they use a lot of energy.

A new method of storing energy in a mechanical, rather than electrical way, was developed. This controlled passive actuation incorporates an automatic gearbox that uses two metal hemispheres instead of a belt drive. Electromotors join in only to compensate for mechanical losses. By doing so, they can work within the high-rev/low-torque regime. The new powertrain was specifically designed for future dike inspection robots, but improving the energy efficiency of existing robots and robot arms is an attractive application as well.