Hopping robots bounce into town

A hopping machine inspired by the seemingly random jumping of grasshoppers may soon give robots unprecedented mobility for exploring other planets, gathering war-fighting intelligence, and assisting police during stand-offs or surveillance operations.

The robot, developed by researchers at the US Department of Energy’s Sandia National Laboratories, uses a combustion-driven piston to make leaps as high as 20 feet.

Other mobile robots use wheels, treads like those on tanks, or insect-like legs to get over and around obstacles. Some are operated remotely by a person who can steer the robot clear of impediments. But reliable, autonomous mobility in difficult environments has eluded robot engineers and complicated planned planetary exploration missions.

The idea, however, has been tried before. Others had tried jumpers using electrically actuated springs and other methods, but the energy required for a leap that could at least clear the robot’s own height was too great, and batteries wouldn’t last long enough for long-range missions.

ISRC senior scientist, Barry Spletzer, suggested that because hydrocarbon fuels provide much greater energy densities than batteries, a small combustion-powered hopper could theoretically travel greater distances and clear larger obstacles.

The Sandia hopping robot is contained inside a grapefruit-sized plastic shell so the hopper rights itself after each jump — piston toward the ground but slightly askew.

A pre-programmed microprocessor inside the hopper reads an internal compass, and a gimbal mechanism rotates the offset-weighted internal workings so that the hopper rolls around until it is pointed in the desired direction.

The combustion chamber fires, the piston punches the ground, and the hopper leaps.

One hopper jumps about 3 feet in the air and 6 feet from its starting point on each jump and can last about 4,000 hops – which is the equivalent of around five miles – on a single tank of gas, which is about 20 grams of fuel. Each hopping cycle is about 5 seconds.

Another hopper developed by Sandia for DARPA – Defence Advanced Research Projects Agency – as an experimental mobile landmine platform jumps 10 to 20 feet in the air and can go about 100 hops on a tank of fuel. The researchers are working to create a self-healing minefield, with hopping mines that sense an adversary’s mine-clearing operations and cooperate with each other to fill any gaps.

The hoppers have been tested in a variety of conditions, and they performed reliably against obstacles, mud, sand, and rough terrain, said Spletzer.

Recalling his youthful experience launching tennis balls out of a tube using lighter fluid, Fischer first suggested that evaporated fuels might provide power needed for high hops.

At one point the Sandia research team had set a goal of simply achieving atmospheric combustion in a small piston chamber, but the first ‘jumps’ did nothing more than topple the robot.

Later the team tried maximising the power of the piston, ultimately achieving hops higher than 30 feet.

The research team now is working on a hopper that can be controlled remotely using a joystick, as well as hoppers with shock-absorbing rubber shells that can land on concrete.