Preliminary Version of a Two-Dimensional
Technical Specification for Softwalls

J. Adam Cataldo, Edward A. Lee, and Xiaojun Liu

Technical Memorandum UCB/ERL M02/9
University of California,
Berkeley, CA 94720, April 17, 2002.



The terrorist attacks of September 11, 2001 proved that airplanes make deadly weapons. In response to this attack-by-aircraft threat, Edward A. Lee proposed Soft Walls, a flight control system that prevents aircrafts from entering no-fly zones. These are restricted airspaces, such as those near major cities, government centers, military installations, chemical factories, and nuclear-power plants. The major objective of this control scheme is to minimize the control imposed on pilots while protecting the no-fly zones. This control scheme uses a map from the aircraft database together with position, velocity, and orientation information from onboard sensors to prevent no-fly zone entry.

This document describes our first approach at a Soft Walls control algorithm. We assume the aircraft travels in a horizontal plane at a constant velocity and can only turn. In this first approach, the no-fly zone is bounded by a line in the horizontal plane. While these approximations are unrealistic, we chose a simple model, which we will later refine for accuracy.