A motorized leg up: this robot changes its limb length to suit the terrain

Jointed legs allow a quadrupedal machine to shape-shift for optimal energy use.

An adaptable robot will be the envy of anyone who has struggled to reach a too-high shelf or to get comfortable in a cramped aeroplane. The machine, developed by Tønnes Nygaard of the University of Oslo and his colleagues, can autonomously extend and contract its limbs in response to its environment.

The researchers first trained this shape-shifting quadruped in the laboratory by having it walk over patches of concrete, sand and gravel. These exercises allowed the team to model how the energy the robot needed to walk was affected by the terrain and by changes in the length of the robot’s ‘leg bones’. When the robot was ultimately turned loose outside on a mix of grass and concrete, it used this model to improve its efficiency by changing its leg length on the fly.

Other demonstrations of morphing robots have relied in part on simulation. But this research was done entirely on hardware, meaning it is “guaranteed to work in reality”, the group says, and could further the development of adaptable robots capable of performing useful tasks.