Butz, M.V., Goldberg, D.E., Lanzi, P.L., & Sastry, K. (2007). Problem Solution Sustenance in XCS: Markov Chain Analysis of Niche Support Distributions and Consequent Computational Complexity. Genetic Programming and Evolvable Machines, 8, 5-37.
Kiryazov, K., Petkov, G., Grinberg, M. , Kokinov, B., and Balkenius, C. (2007). The Interplay of Analogy-Making with Active Vision and Motor Control in Anticipatory Robots. In Butz, M. et al. (Ed.) Anticipatory Behavior in Adaptive Learning Systems: From Brains to Individual and Social Behavior. LNAI, 4520, Springer-Verlag
Caligiore D., Ferrauto T., Parisi D., Accornero N., Capozza M., Baldassarre G. (2008). Using motor babbling and Hebb rules for modeling the development of reaching with obstacles and grasping. In Dillmann Rüdiger, Maloney Colette, Sandini Giulio, Asfour Tamim, Cheng Gordon, Metta Giorgio, Ude Ales (orgs.), International Conference on Cognitive Systems (CogSys2008) (In electronic format). (University of Karlsruhe, Karlsruhe, Germany, 2-4 April 2008)
To a robot designer like Sangbae Kim, the animal kingdom is full of inspiration.
"I always look at animals and ask why they are the way they are," says Kim, an assistant professor of mechanical engineering at MIT. "As an engineer, looking at them and speculating is fascinating."
While a graduate student at Stanford, Kim drew inspiration from the gecko to build a climbing robot, and he is now designing a running robot that mimics the movements of a cheetah. Such agile, fast-moving robots could perform military surveillance and search-and-rescue missions deemed too dangerous for humans to undertake.
His Biomimetic Robotics Lab is one of several at MIT pursuing biologically inspired engineering. A team of mechanical engineers has built robotic fish, and materials scientists have designed moisture-collecting materials that mimic a beetle's shell.
Evolution has produced finely tuned adaptations over millions of years, so it only makes sense to turn to nature for design ideas. However, while Kim seeks inspiration in nature, he's not trying to produce exact robotic copies of a particular animal. Such copying would be difficult to achieve and not necessarily the most effective design strategy.
"There are millions of things that animals have to adapt for, and it is almost impossible to compare evolution to our engineering/mathematical optimization process," says Kim. "And you have to be careful about copying other features that may not be related to the particular function you want to achieve. Therefore, extracting scientific principle is extremely important for designers like me."
Stickybot
When Kim and his colleagues at Stanford set out to build a climbing robot, at first they figured they needed to make the robot's feet sticky. However, they soon realized that very sticky feet can't detach very easily.
Their approach shifted dramatically with the 2006 discovery, by Lewis and Clark College biologist Kellar Autumn, that geckos use a phenomenon called directional adhesion to stick to walls.
"The gecko gave us a completely new perspective. Stickiness does not necessarily come from chemical composition; it can come from mechanical properties and geometry," says Kim. "The geometry enables strange phenomena such as directional adhesion, which sticks in only one direction."
The pads of a gecko's feet are covered with a forest of tiny hairs called setae, some of which are one-twentieth the width of a human hair. The setae, in turn, branch into hundreds of tiny smaller hairs called spatulae, which are about one-thousandth the width of a human hair. These hairs cling to surfaces using tiny molecular interactions known as van der Waals forces. Collectively, the forces are strong enough to support the gecko's weight as it scrambles up a vertical surface.
To demonstrate, Kim rummages around in a desk drawer in his office and pulls out a small rectangle of the gecko-inspired adhesive material, which resembles a tiny patch of blue Astroturf. A compact disc gently held against the horizontal surface attaches securely in one direction and then easily detaches in the opposite direction.
The adhesive is covered with hairs made of rubber silicone, which are thicker than those on a gecko's paw (about four times thicker than a human hair). Because thicker hairs require smoother surfaces for adhesion, Stickybot can only climb extremely smooth surfaces like glass.
Kim and his colleagues, led by Stanford professor Mark Cutkosky, first demonstrated Stickybot in 2006, and Time magazine named it one of that year's best inventions. The paper describing the robot also won the 2008 Best Paper Award for the IEEE Transactions on Robotics.
Potential applications for the stickybot technology include exterior repair of underwater oil pipelines and window washing. Kim also plans to start designing climbing equipment for humans using the directional adhesion technology.
Need for speed
Kim, who arrived at MIT as an assistant professor in June, is now turning his attention to a speedier robot, inspired by the cheetah. Four graduate students have just begun working on the cheetah project, and within the next two years Kim hopes to have a prototype that can run 35 miles per hour.
Though his design incorporates principles from a variety of running animals, including horses and dogs, Kim zeroed in on the cheetah because of its special adaptations for speed. One feature he plans to mimic is the flexibility of the cheetah's backbone, which gives extra speed or force to its running motion.
To demonstrate how extra joints can add force and speed, Kim leans back in his chair and mimics throwing a baseball, in slow motion — first the shoulder, then the elbow, then the wrist bend. The force imparted by each of those joints adds up, allowing a pitcher to throw a faster pitch. In the same way, the joints of the cheetah's leg — hip, knee and ankle — are aided by the extra speed generated by its bending backbone, which is much more flexible than that of other running mammals.
Kim and his students plan to start building and testing prototypes within the next 18 months, after using a computer model to calculate the optimal limb length and weight, gait and torque of the hip and knee joints.
He expects that the biggest challenge will be getting enough power out of the motor to furnish the desired speed. To that end, he plans to build the robot out of lightweight carbon fiber-foam composite, so less power is needed to propel it.
Another difficult problem is coordinating the control of three joints in four legs. Those 12 joints each have to move in concert with the others, and they need to be able to react smoothly to disturbances in the gait, such as tripping over a rock, and regain balance.
Kim believes his robots could be a significant improvement over current wheeled robots used for scouting and search and rescue, which are efficient but slow. "It's going to be very exciting to see how fast we can go and how rough a terrain we can navigate."
By combining origami and electrical engineering, researchers at MIT and Harvard are working to develop the ultimate reconfigurable robot — one that can turn into absolutely anything. The researchers have developed algorithms that, given a three-dimensional shape, can determine how to reproduce it by folding a sheet of semi-rigid material with a distinctive pattern of flexible creases. To test out their theories, they built a prototype that can automatically assume the shape of either an origami boat or a paper airplane when it receives different electrical signals. The researchers reported their results in the July 13 issue of the Proceedings of the National Academy of Sciences.
As director of the Distributed Robotics Laboratory at the Computer Science and Artificial Intelligence Laboratory (CSAIL), Professor Daniela Rus researches systems of robots that can work together to tackle complicated tasks. One of the big research areas in distributed robotics is what’s called “programmable matter,” the idea that small, uniform robots could snap together like intelligent Legos to create larger, more versatile robots.
The U.S. Defense Department’s Defense Advanced Research Projects Agency (DARPA) has a Programmable Matter project that funds a good deal of research in the field and specifies “particles … which can reversibly assemble into complex 3D objects.” But that approach turns out to have drawbacks, Rus says. “Most people are looking at separate modules, and they’re really worried about how these separate modules aggregate themselves and find other modules to connect with to create the shape that they’re supposed to create,” Rus says. But, she adds, “actively gathering modules to build up a shape bottom-up, from scratch, is just really hard given the current state of the art in our hardware.”
A new wrinkle
So Rus has been investigating alternative approaches, which don’t require separate modules to locate and connect to each other before beginning to assemble more complex shapes. Fortunately, also at CSAIL is Erik Demaine, who joined the MIT faculty at age 20 in 2001, becoming the youngest professor in MIT history. One of Demaine’s research areas is the mathematics of origami, and he and Rus hatched the idea of a flat sheet of material with tiny robotic muscles, or actuators, which could fold itself into useful objects. In principle, flat sheets with flat actuators should be much easier to fabricate than three-dimensional robots with enough intelligence that they can locate and attach to each other.
Erik Demaine describes how the prototype robot can automatically fold itself into an airplane or an origami boat. Video: Melanie Gonick; original footage: E. Hawkes/B. An/N.M. Benbernou/H. Tanaka/S. Kim/E.D. Demaine/D. Rus/R.J. Wood
About a year ago, Demaine and several colleagues — including his dad, who’s a visiting scientist at CSAIL, master’s student Aviv Ovadya, and Nadia Benbernou, a PhD student in applied mathematics who’s a coauthor on the new paper — proved that a large enough sheet creased in what’s called the “box pleat pattern” could be folded into a close approximation of any possible three-dimensional shape. The box pleat pattern divides the sheet into squares, each of which has a diagonal crease across it; but if two squares share an edge, their diagonal creases are mirror images. This paper marked the first time that the universality of a crease pattern had been shown, although Demaine and his collaborators have since proved that other crease patterns are universal as well.
Based on this result, Demaine, Rus, Harvard’s Robert Wood, and others developed algorithms that, given an arbitrary three-dimensional shape, could generate a sequence of folds that would produce it from a box-pleated sheet.
But as yet, no robotic system existed that could execute that sequence of folds automatically. In principle, a universal origami robot would have actuators on both sides of every crease, so that the sheet could fold in either direction at any point. But a system that complex is difficult to build, and before undertaking it, the researchers hoped to demonstrate the viability of their approach.
Theory into practice
So they designed yet another set of algorithms that, given sequences of folds for several different shapes, would determine the minimum number of actuators necessary to produce all of them. Then they set about building a robot that could actually assume multiple origami shapes. Their prototype, made from glass-fiber and hydrocarbon materials, with an elastic plastic at the creases, is divided into 16 squares about a centimeter across, each of which is further divided into two triangles. The actuators consist of a shape-memory alloy — a metal that changes shape when electricity is applied to it. Each triangle also has a magnet in it, so that it can attach to its neighbors once the right folds have been performed.
The sheet is too small — or, depending on your perspective, the triangles are too big — to do anything very useful yet. But, in principle, it’s possible to build either a similar sheet with much smaller moving parts, or a larger sheet with similar-sized moving parts. With a finer-grained sheet, “you could imagine downloading the new iPhone,” Demaine says. “In the same way that you download the latest CD from your favorite artist totally electronically, you could imagine downloading shapes electronically, and programming hardware the same way you program software.” Larger sheets could enable “a tent that can adapt its shape according to the wind so that it doesn’t blow over,” Demaine says, or “a solar cell that can adjust its shape to the sun and the cloud patterns and whatnot.”
“It’s a very nice merger of the abstract mathematical theory and the practical world,” says Joseph O’Rourke, the chair of the computer science department at Smith College, who was one of the referees for the PNAS paper. “It may be appropriate to say it’s some type of breakthrough.” O’Rourke points out, however, that Demaine’s universality proof relied on the assumption that the triangles in the box-pleated material were themselves somewhat flexible, which may not be the case with, for instance, tiny sheets of material carved out of silicon.
Demaine agrees but says that he and his group are approaching the problem from two directions. On one hand, they’re trying to mathematically model the flexibility of the triangles, so that the folding algorithms can take that into account. On the other, they’re taking some tentative first steps toward a theory of origami with rigid materials. “We are sorely lacking in rigid-origami theory, as Joe points out and I'd be quick to agree,” Demaine says.
R. Rojas, A. Gloye Förster: Holonomic Control of a robot with an
omnidirectional drive, KI - Künstliche Intelligenz, vol. 20, nr. 2,
BöttcherIT Verlag, 2006.
Anticipatory Cognitive Science is a research field that ensembles artificial intelligence,
biology, psychology, neurology, engineering and philosophy in order to build anticipatory cognitive systems that
are able to face human tasks with the same anticipatory capabilities and performance. In deep:
Cognitive science is the interdisciplinary study of mind and intelligence, embracing philosophy, psychology,
artificial intelligence, neuroscience, linguistics, and anthropology. Its intellectual origins are in the mid-1950s
when researchers in several fields began to develop theories of mind based on complex representations and
computational procedures. Its organizational origins are in the mid-1970s when the Cognitive Science Society
was formed and the journal Cognitive Science began. Since then, more than sixty universities in North America, Europe, Asia,
and Australia have established cognitive science programs, and many others have instituted courses in cognitive science.
