Volume 3, Issue 5 June/July 2003

2003
2002
2001

A Force Field for No-Fly Zones by David Pescovitz Printer-friendly version Professor Edward A. Lee is co-author with Berkeley colleague Pravin Varaya of the book Structure and Interpretation of Signals and Systems (Addison Wesley, 2003) Cordell Green photo Imagine if on September 11, 2001, New York City was surrounded by a force field. When the terrorists flying toward the World Trade Center began their descent, they would have encountered a phenomenon not unlike a vortex that pushed the plane to the left or right. As they fought toward their target, the resistance could have increased until the plane was automatically diverted from lower Manhattan. This kind of virtual bubble around "forbidden zones" of airspace is the aim of Soft Walls, a project underway within UC Berkeley's Center for Hybrid and Embedded Software Systems (CHESS), part of the Center for Information Technology Research in the Interest of Society (CITRIS). "We're trying to solve the problem that aircraft can be used as weapons," says Professor Edward A. Lee of the Department of Electrical Engineering and Computer Sciences (EECS). Lee is collaborating on the project with EECS chair Shankar Sastry, graduate students Adam Cataldo, and postdoctoral researcher Ian Mitchell. The Soft Walls system would be embedded in new aircraft and does not depend on any air traffic control infrastructure or networking technology. The approach takes advantage of modern aircrafts' "fly-by-wire" system that translates a pilot's commands into the computer instructions that actually control the aircraft. The Soft Walls software, Lee explains, contains a database of "no-fly zones." Using a plane's existing gyroscope-based inertial navigation system and Global Positioning System (GPS) technology, the on-board computer checks the plane's location against the database. This diagram depicts several responses of the Soft Walls system on a plane about to enter a no-fly zone. Courtesy Adam Cataldo "The idea is to constrain the airspace within which an aircraft can fly while maintaining the maximum amount of pilot authority," Lee says. If the plane is heading into a forbidden zone, the pilot will first be notified visually and resistance will build. If the pilot does not cooperate and change the flight path, "the controls will eventually saturate and the aircraft will be diverted," Lee explains. Even at that point, Lee adds, the pilot will maintain fine-grain control of the aircraft to avoid dangers like a mid-air collision with another aircraft that may be in the no-fly zone. "We have viable control algorithms and a strategy for figuring out how to blend the pilot's input with the control system," he says. "But there's a lot more work to ensure that the solution is robust." Soft Walls: science fiction or homeland security? We want to hear from you... For example, the security of such a system is a huge concern. Jamming the aircraft's GPS so it can't calculate its location or "spoofing" the system into thinking it's somewhere else would be catastrophic, Lee says. The researchers are currently collaborating with experts in flight navigation systems to identify and block any potential security flaws. Once the technical challenges are ironed out, will Soft Walls fly? Boeing and Honeywell are interested, Lee says. Meanwhile, NASA is leading a project to build consensus in the entire aviation industry about the most effective and acceptable method to prevent airplanes from becoming missiles. The toughest sell on Soft Walls, Lee says, are pilots. "There's a 2,000 year-old tradition of a ship's captain that gives a pilot tremendous authority on board a craft," he says. "There's a lot of suspicion in aviation of any technique that attempts to limit that authority in any way." The Soft Walls Project 'Soft walls' will keep hijacked planes at bay (NewScientist.com - July 2, 2003) Edward A. Lee's Home Page Center for Hybrid and Embedded Software Systems (CHESS) Center for Information Technology Research in the Interest of Society (CITRIS) Lab Notes is published online by the Public Affairs Office of the UC Berkeley College of Engineering. The Lab Notes mission is to illuminate groundbreaking research underway today at the College of Engineering that will dramatically change our lives tomorrow. Editor, Director of Public Affairs: Teresa Moore Writer, Researcher: David Pescovitz Designer: Robyn Altman Subscribe or send comments to the Engineering Public Affairs Office: lab-notes@coe.berkeley.edu. © 2003 UC Regents. Updated 5/30/03.