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cornell_logo Cornell Ranger, 2011-2012
4-legged bipedal robot

Ranger walks non-stop 65.2 km (40.5) mile ultra-Marathon on May 1-2, 2011

By improving the controls algorithm and the electronics, Ranger's energy use was reduced by 43% from July 2010 when Ranger walked 14.3 miles. Before that the record was held by Boston Dynamics' BigDog, an all-terrain gas-powered quadruped, which trotted 12.8 miles without refueling. In contrast, in February 2011, in Osaka Japan at the first robot marathon, the robots repeatedly refreshed their batteries. On this 40.5 mile walk Ranger was never recharged or even touched by a person.

Ranger was steered with a model-plane remote control that controlled a small motor which twisted the inner pair of legs. The coordination of the walking was by the 6 onboard microprocessors. Unlike many bipedal robots which have large flat feet, Ranger has small rounded feet and cannot stand upright. At each step it falls and catches itself in a controlled manner. The challenge met here is to have a robot robust enough to take 186,076 steps while only using 5 cents worth of electricity.

Journal paper, appendices and detailed documentation of Ranger design

Old Ranger Webpages:    2010     2008     2006

Proposed Rules for Legged Robot Distance Record

Pictures:  (Pictures with thumbnails and captions)
(Zipped collection, 171MB)

Video: (downloads HD-253MB High-44MB  Medium-23MB  Low-1.2MB)

(click title below for youtube streaming video)
Note: This video is basically about a robot walking in circles for over 30 hours, all through the night. The video starts with a practice at a cancer fundraiser. Part way through you can hear Ranger play the Cornell theme song ("High above Cayuga's waters..."), which it did every kilometer. At the end you see it coming to an abrupt stop when the batteries died.

1-2 May 2011 Walk Statistics:

Total steps                           186,076, starting at 2:11 PM May 1, ending at 9 PM on May 2         
Total time                            110,942 seconds (= 30 hrs 49 min 02 seconds)
Number of laps                   307.75
Lap distance                        212 meters (= 0.132 miles)
Total distance                      65,243 meters (= 65.24 km = 40.54 miles)
Average time per step          0.6 seconds
Average distance per step    0.35 meters = 13.78 in
Average speed                     0.59 meter/second (= 2.12 km/h = 1.32 mph)
Power                                  16.0 watts total (11.3 W to motors, 4.7 W to computers and sensors)                                                Less than a laptop computer.
                                           About a penny's worth every 8 miles or every 6 hours.
Energy                                 493 watt-hours (about 5 cents worth)
Battery                                 25.9V Lithium-ion, 2.8 kg (6.3 lb)
Total Robot mass                  9.91 kg (= 21.85 lb)
Cost of transport (COT)       0.28,  COT = Energy/(weight * distance).                                    
                                            Includes energy to run the motors and all electronics                                                                           Comparisons:
                                                  Toyota Prius COT = about 0.15
                                                  Human COT = about   0.2 (a bit better than Ranger)
                                                  Asimo   COT = about   2    (54 kg@ 1.5 m/s, 1.8 kW)
                                                  BigDog COT = about 15    (12.8 miles, 4 gal gas, 110 kg)
                                                    (Asimo and BigDog are both much more capable than Ranger                                                                in all ways but for energy effectiveness.)
Computers                           One ARM9 and five ARM7 processors running about 10,000 lines
                                            of code executed every 2 miliseconds. Microstrain IMU. CAN bus.

The Team:

Principal Investigator:
Andy Ruina
Lab Manager: Jason Cortell
Visiting students: DaniŽl Karssen, Bram Hendriksen, S. Javad Hasaneini, Feng Shuai, Pulkit Kapur, Kang An.
Graduate students: Pranav Bhounsule, Leticia Rojas-Camargo, Rohit Hippalgaonkar, Ko Ihara, Sam Hsiang Lee, Gregg Stiesberg, Andrey Turovsky, Kevin Tang, Nan Xiao, Anoop Grewal, Petr Zaytsev, Atif Chaudhry.
Undergraduates: Carlos Arango, Steve Bagg, Megan Berry, John Buzzi, Amy Chen, Alexis Collins, Stephane Constantin, James Doehring, Gregory Falco, Hajime Furukawa, Alex Gates, Matt Haberland, Avtar Khalsa, Andrew LeClaire, Emily Seong-hee Lee, Reubens Lee, Alexander Mora, Andrew Mui, Nicole Rodia, Andrew Spielberg, Yingyi Tan, Chen Kiang Tang, Kevin Ullmann, Max Wasserman, Denise Wong, Joshua Petersen, Matt Coryea, Jehhal Liu, Ming-Da Lei, Dapong Boon-Long, Kirill Kalinichev, Saurav Bhatia, Thomas Craig, Phillip Johnson, Katie Hartl, Andrew Nassau, Brian Clementi, Kevin Boyd, Emily McAdams, Satyam Satyarthi, Sergio Biagioni, Nicolas Williamson, David Bjanes, Violeta Crow, Mike Digman, John Kuriloff, Hellen Lopez, Lauren Min.
Visiting scholars: Chandana Paul, Li Peng Yuan, Amur Salim, Dong Chun.
High school student: Ben Oswald
(please let Andy know of any accidental omissions here)


NTDTV - Cornell Students' Walking Robot Sets World Record 1 min 31 sec (link) (youtube)
Reuters - Walking robot sets record 1min 12 sec (link

Dailymail - Marathon robot: 'Ranger' sets a world record by walking 40.5 miles non-stop on a single battery charge (link) (cached)
MSNBC - Robot walks 40.5 miles non-stop (link) (cached)
Engadget - Cornell's Ranger robot walks 40.5 miles on a single charge, doesn't even break a sweat (link) (cached)
Cornell Chronicle - Robot walks a 40.5-mile ultramarathon without recharge (link) (cached)
Gizmag - Ranger robot breaks its own endurance record (link) (cached)
Popsci - Ranger robot sets a new distance record, walking 40 miles on a single charge (link) (cached)
Ubergizmo - Robot Ranger walks 40.5 miles on solitary battery charge, setting a new world record in the process (link) (cached)
Tecca - Ranger robot trots 40 miles straight on 5 cents worth of electricity (link) (cached)


NSF Robust Intelligence; and some supplemental undergraduate support from Cornell's College of Engineering.

Thanks also to the following companies, for free samples and product discounts:
Keil Software Inc., MicroMo Electronics, CadSoft Computer, Freescale Semiconductor, Maxim Integrated Products, Inc., Infineon Technologies, Analog Devices, Inc., GMW Associates, Tyco Electronics, Molex Inc.