Original URL: http://www.theregister.co.uk/2013/05/17/mit_battery_powered_robot_cheetah/

MIT takes battery-powered robot cheetah for a gallop

Biomimetic big cat needs no power cord, just a walker

By Iain Thomson

Posted in Hardware, 17th May 2013 19:55 GMT

Video Fast, agile robots for reconnaissance and rescue have been under development for half a decade or more, but they all have needed to be tethered to a power cable. Now MIT thinks it has cut the leash with a battery powered "cheetah" capable of outrunning a human.

The design, showed off at the International Conference on Robotics and Automation this month, borrows heavily in design from the animal kingdom. It's about the same size and weight as a regular cheetah, uses Kevlar tendons on its legs to make them 60 per cent more efficient, and has a spine controlled by the movement of the robot's legs.

Alternative running robot designs, such as the DARPA-funded Boston Dynamics cheetah, use hydraulics to power strides, but MIT decided that these were too heavy, and so developed a "three phase permanent magnet synchronous motor". This is more power-efficient and torquey than commercial electric systems, and uses regenerative motors to reuse power in a way similar to that used by hybrid cars.

The scientists say this design gives MIT's cheetah a cost of transport (COT) ratio (defined as power consumption divided by weight times velocity) of 0.52, which is about the ratio of a flesh-and-blood cat. By comparison Honda's Asimo robot has a COT of 2 and Boston Dynamics's petrol-powered Big Dog robot pack animal has a COT of 15.

This conservation of power means that the new design won't need an electrical cable to operate, and instead will use four 22.2-V lithium polymer batteries to maintain a pace of 5.2 mph (8.3 kph) for 1.23 hours, IEEE Spectrum reports, giving it a range of 6.2 miles (10km).

There's a cost for this design in terms of speed however – Boston Dynamics's machine can run at 28.3 mph (45.5kph) but MIT's effort can only manage 13.7 mph (22 kph). While that's only half as fast, it's still good enough to outpace most humans over its range.

Before you start having nightmares about being hunted down by robots, there's still work to be done. While MIT's robot is power-independent there's still a lot more to be done in terms of balancing itself in three dimensions – in testing, the robot has to be strung up in a walking frame in case it topples over.

There's also going to be extra power issues to sort out before the MIT cheetah becomes viable. A military robot in the field will need some kind of camera and communications system to relay data back to base, and if it's weaponized that will mean more weight.

In El Reg's opinion the designer should just stick a pair of titanium teeth on the robot and let it run – it would be enough to scare most soldiers back into their foxholes if a horde of these cheetahs sprinted towards them. ®