Robot Special: Walk This Way From: New Scientist - 02/04/2006 - Vol. 189, No. 2537, P. 40 By: Philip Ball Only recently has the concept of passive walking robots - machines that can imitate a human's entire gait cycle by relying on leg motion and gravity rather than motors - gained prominence, and an important sign of the technology's increasing distinction was the unveiling of three passive walkers at an American Association for the Advancement of Science conference last February. A team led by Cornell University's Andy Ruina built a robot that mimics people's ability to pump their gait by pushing off their back foot at the beginning of each step by using a spring in each lower leg; a small motor stretches the spring, which causes the ankle joint to flex when released. Another robot, built by MIT researchers supervised by Russ Tedrake, can sense the tilt of its body and other factors in order to "learn" how to walk, using an on-board computer that adjusts command signals transmitted to electric motors that flex the ankles. The third robot was the product of the Delft University of Technology in the Netherlands: The device is driven by compressed-air actuators in the hips, and features an ankle design influenced by skateboard suspension principles that adds stability. All three machines represent a significant advance because they simplify leg design and control, and lower energy consumption. Passive walkers' inability to steer or avoid obstacles, as well as their difficulty in dealing with uneven or pliable surfaces, makes them inappropriate models for robust walking robots, according to Carnegie Mellon University roboticist Chris Atkeson. He believes the best solution will mix principles of both passive dynamic walkers and powered walkers, and expects practical robots will be driven by most if not all of their joints. Passive-walking robots are also inspiring research into advanced prosthetics that could perhaps reduce the energy cost to the wearer and amplify human performance. Read the article's preview at: http://www.newscientist.com/channel/mech-tech/mg18925371.900 Links: Andy L. Runia http://www.tam.cornell.edu/Ruina.html http://ruina.tam.cornell.edu/ Andy L. Ruina - Research http://ruina.tam.cornell.edu/research/ Andy L. Ruina - Locomotion and Robotics - Overview http://ruina.tam.cornell.edu/research/topics/locomotion_and_robotics/overview.htm Walking Robots http://www-personal.engin.umich.edu/~shc/robots.html The Mechanics of Foot Travel http://www.nsf.gov/news/news_summ.jsp?cntn_id=104454&org=NSF&from=news Dynamic Walking 2006 http://www.dynamicwalking.org/ Russ Tedrake http://groups.csail.mit.edu/locomotion/russt.html MIT Robot Locomotion Group http://groups.csail.mit.edu/locomotion/index.html Teams build robots that walk like humans http://web.mit.edu/newsoffice/2005/robotoddler.html Christopher G. Atkeson http://www.cs.cmu.edu/~cga/