March 14 '08

Dertouzos Lecturer Series: Robert J Full

March 15, 2007 - Professor Robert J. Full of the University of California at Berkeley gave Dertouzos Lecturer Series Talk titled "Bipedal Bugs, Galloping Ghosts and Gripping Geckos: Neuromechanical Systems Biology" Abstract: The challenge of neuromechanical integration demands an interdisciplinary effort to match data systematically across mathematical models, numerical simulations, physical models, as well as biological experiments. Locomotion results from high-dimensional, dynamically coupled interactions between an organism and its environment. Fortunately, simple models we call templates can resolve the redundancy of multiple legs, joints and muscles. A template is the simplest dynamical system model that exhibits a targeted behavior. Extraordinarily diverse animals show the same dynamics - legged animals appear to bounce like people on pogo sticks. Force patterns produced by six-legged insects are the same as those produced by trotting eight-legged crabs, four-legged dogs and even running humans. These diverse species that differ in leg number and posture run in a stable manner like sagittal- and horizontal-plane spring-mass systems. Mathematical models show that these designs self-stabilize to perturbations without neural feedback. Templates must be grounded in more detailed models to ask questions about multiple legs, the joint torques that actuate them, the recruitment of muscles that produce those torques and the neural networks that activate the ensemble. We term these more elaborate models anchors. Since mechanisms require controls, anchors incorporate hypotheses concerning the manner in which unnecessary motion or energy from legs, joints and muscles is removed, leaving behind the behavior of the body in the low-degree of freedom template. Guided by direct experiments on many-legged animals, mathematical models and physical models (robots), we postulate a hierarchical family of control loops that necessarily include constraints of the body's mechanics. At the lowest end of this neuromechanical hierarchy, we hypothesize the primacy of mechanical feedback - neural clock excited tuned muscles acting through chosen skeletal postures. Control algorithms appear embedded in the form and skeleton of the animal itself. Muscles tune the system by acting as motors, springs, struts and shocks all in one. On top of this physical layer, we hypothesize sensory feedback driven reflexes that increase an animal's stability further and, at the highest level, environmental sensing that operates on a stride-to-stride timescale to direct the animal's body. Finally, locomotion requires an effective interaction with the environment. Amazing feet permit creatures such as geckos to climb up walls at over meter per second without using claws, glue or suction - just molecular forces using hairy toes. These fundamental principles of animal locomotion have inspired the design of new control circuits, tuned structured, artificial muscles, self-clearing dry adhesives, and autonomous legged robots such as the Ariel, Mecho-gecko, Sprawl, RHex, RiSE and Stickybot that can aid in search and rescue, inspection, detection and exploration. Biography: Professor Full directs the Poly-PEDAL Laboratory, which studies the Performance, Energetics and Dynamics of Animal Locomotion (PEDAL) in many-footed creatures (Poly). His research program in comparative physiology and biomechanics has shown how examining a diversity of animals can lead to the discovery of general principles of locomotion. His programmatic theme is Diversity Enables Discovery. Professor Full has led an effort to demonstrate the value of integrative biology and biological inspiration by the formation of fourteen interdisciplinary collaborations and five new design teams composed of biologists, engineers, mathematicians and computer scientists from academia and industry. His fundamental discoveries in animal locomotion have inspired the design of novel neural control circuits, artificial muscles, eight autonomous legged robots and the first self-cleaning dry adhesive. Professor Full has authored over two hundred contributions and has delivered an equal number of national and international presentations. To further his efforts, Professor Full has just created a new center at Berkeley called CIBER, the Center for Interdisciplinary Bio-inspiration in Education and Research focused on training the next generation of scientists and engineers to collaborate in mutually beneficial relationships. Publications:

Holmes, P., Full, R.J., Koditschek, D. and Guckenheimer, J. 2006. The dynamics of legged locomotion: Models, analyses, and challenges. SIAM Review 48 (2) 207-304.

Goldman, D.I., Chen T.S., Dudek, D.M. and R.J. Full. 2006. Dynamics of rapid vertical climbing in cockroaches reveals a template. The Journal of Experimental Biology, 209 (15) 2990-3000.

Cowan, N.J., Lee, J. and R.J. Full. 2006. Task-level control of rapid wall following in the American cockroach. The Journal of Experimental Biology, 209 (9) 1617-1629.

Koditschek, D.E., Full, R.J. and Buehler, M. 2004. Mechanical aspects of legged locomotion control. Arthropod Structure & Development. vol. 33 (3) 251-272.

Dickinson, M.H. Farley, C.T., Full, R.J., Koehl, M. A. R., Kram, R., and Lehman, S. 2000. How animals move: An integrative view. Science 288, 100-106.

Autumn, K., Liang, Y., Hsieh, T, Zesch, W., Chan, W.-P., T. Kenny, Fearing, R., and Full, R.J.. 2000. Adhesive force of a single gecko foot-hair. Nature. 405,681-685.