Ranger, a bipedal robot built by engineers at Cornell’s University sets a new world record by walking 40.5 miles on a single battery charge without stopping. The previous record was 14.3 miles, set by the same r0bot last year.
Ranger set the record last week after completing 308 laps around university’s Barton Hall running track — took 30 hours, 49 minutes and 2 seconds of nonstop walking.
According to the development team:
Their robot’s stamina has a lot to do with its energy efficiency.
While most legged robots achieve stability by carefully controlling all of the joint angles in their bodies, Ranger achieves its low energy use by, as much as possible, letting the legs swing as they will. Also, most bipedal robots stand on flat feet. Ranger can’t stand upright at all; instead, it balances by falling and catching itself at each step. The trick is to make the catch at the right time and place.
Ranger’s total weight is 22 pounds, of which 6 pounds are the lithium-ion batteries that power the electronics and the motors. One of these motors extends the outer ankles, another extends the inner ankles and a third swings the legs. A fourth smaller motor twists the inner legs for steering. The motors consume an additional 11.3 watts. At 16 watts total, the specific cost of transport (COT, energy per unit weight per unit distance) was a relatively stingy 0.28 joules per newton-meter. Most robots use much more energy (with a typical COT of 1.5 or more). Ranger still isn’t as efficient as a typical human, who walks with a COT of about 0.2.
Ranger has six small on-board computers executing about 10,000 lines of computer code. The programs run in a repeating loop every 1/500th of a second. The robot also has dozens of electrical and mechanical sensors. The electronics used 4.7 watts.
Engineers feel that their robot can still do better than 40.5 miles and they will incorporate automatic steering into its gait, next time they try for another record.
I think we can still do better. Our challenge is to lower the energy use while still maintaining balance. The achievement is to have gone 186,076 steps on 5 cents worth of electricity, and without falling down. … If we try for another record, it will be with automatic steering.