© 2003 by Davi GeigerBuilding Robots January 2003 L1.1 Robot Behavior Shortest Path Behavior

© 2003 by Davi GeigerBuilding Robots January 2003 L1.2 Learn how to go from point A to point B How the A* algorithm works How to integrate A* with Robot Sensor- Reaction. Learn how to compose and coordinate behaviors Objectives

© 2003 by Davi GeigerBuilding Robots January 2003 L1.3 Learn how to go from point A to point B New Objects can be present at the time of performance A B Plan of the room is provided Costs to move can vary spatially

© 2003 by Davi GeigerBuilding Robots January 2003 L1.4 A* Algorithm Dijkstra’s Algorithm (see postscript) Extension to add lower bound estimate to the goal so that the search is faster. If a minimum distance from any position v to the goal g is quickly estimated, we can add that to the cost of transition w(u,v). For example D(v,g) = |g-v| is a minimun distance from u to g.

© 2003 by Davi GeigerBuilding Robots January 2003 L1.5 How to integrate A* with Robot Sensor-Reaction. If new objects are present at the time of performance, only through sensor this information will be obtained. One needs an architecture that will respond to sensors and obstacle avoidance to move around new objects while still moving toward the goal. A* will need to be rerun from that new location as the source location (unless such solution already exists, e.g., all solutions from goal to any location may have already been computed.