Tuesday, March 30, 2004
430-438 Soda Hall, Wozniak Lounge
2:00-3:00 p.m.

Professor Claire Tomlin

Department of Aeronautic and Astronautics & Electrical Engineering,
Stanford University

Computational Methods for Analyzing and Controlling Hybrid Systems

Abstract:

Hybrid systems are a suitable model for representing systems that can transition between different behaviors. Many engineered systems are designed to be hybrid in order to simplify function and maintain flexibility in operation. For example, air traffic control systems involve transitions between simple flight modes for multiple aircraft. Hybrid systems are also a good framework for modeling natural systems: in cell biology, the dynamics that govern the spatial and temporal increase or decrease of protein concentration inside a single cell are continuous differential equations derived from biochemistry, yet their activation or deactivation is triggered by transitions which encode protein concentrations reaching given thresholds.

In this talk, methods that we have designed to analyze, verify, and control hybrid systems will be presented. The methods use tools from game theory, fast wavefront propagation, and symbolic predicate abstraction. Our algorithms rely on an iterative refinement procedure which computes, either exactly or approximately, regions of the system's operating space in which desired behavior is guaranteed. In engineered systems, controllers are designed to keep the system in these regions. In biological systems, knowledge of the actual operating space is used, in conjunction with our algorithm, to help hypothesize possible models and `reverse engineer' the system. We will focus on two examples: the design and implementation of real time collision avoidance schemes for aircraft (with NASA and Boeing), and the development of a model of a planar cell polarity mechanism in fly wings (with the Stanford University School of Medicine).

Claire Tomlin received the Ph.D. degree in Electrical Engineering from the University of California, Berkeley, in 1998. Since September 1998 she has been an Assistant Professor in the Department of Aeronautics and Astronautics at Stanford University, with a courtesy appointment in Electrical Engineering. She has held visiting research positions at NASA Ames and Honeywell Labs. She is a recipient of the Eckman Award of the American Automatic Control Council (2003), MIT Technology Review's Top 100 Young Innovators Award (2003), AIAA Outstanding Teacher Award (Stanford, 2001), NSF Career Award (1999), Terman Fellowship Stanford, 1998), and the Bernard Friedman Memorial Prize in Applied Mathematics (Berkeley, 1998).