Thanks...I might be able to use the stuff in art_pilot. I'll let you know. ~Deepak "Jack O'Quin" Sent by: ros-users-bounces@code.ros.org 12/09/2010 02:20 PM Please respond to User discussions To User discussions cc ros-users-bounces@code.ros.org Subject Re: [ros-users] controllers for car-like robots On Thu, Dec 9, 2010 at 2:08 PM, wrote: Eitan, Tully, Jack, Thanks for your help. I looked through the ART code, and it seems to me they have divided up the code into task specific controllers for e.g. following lane, u-turn etc. rather than using a single control algorithm like DWA. It seems that most of the Urban Challenge teams did this... is there a reason why? Is it that generic controllers aren't good enough for Ackerman drives? I don't know about other teams, but one of the DARPA Urban Challenge requirements was to obey the California Drivers' Handbook when interacting with other traffic [1]. For that, we found an hierarchical state machine very helpful. None of it was motivated by Ackermann steering constraints. As we re-implement our navigation using ROS, we will probably retain the state machine, but migrate it to smach. Our navigation package was written in a hurry for the competition. It is mainly reactive control for following lanes and obeying the rules of the road. The main "planning" is a simple A* to discover a route through the road network (in the commander node). The ROS version is not a complete port of our 2007 code. It still lacks obstacle avoidance (we are reimplementing that using ROS messages), but it does work well on our car. As mentioned before, art_nav is probably not what you want, but you're welcome to any parts that seem useful. The Ackermann steering and servo controls are mostly implemented in the art_pilot and art_servo classes. Maybe some of those interfaces are worth looking at. Our "zone" controller, written by Patrick Beeson, deals with navigating in unstructured parking lots. It does some planning using Voronoi graphs and other techniques. It is not yet ported to ROS, but the code is there if you want to look at it. That may be more relevant, depending on your needs and goals. [1] http://www.jopha.net/index.php/jopha/article/view/14 -- joq _______________________________________________ ros-users mailing list ros-users@code.ros.org https://code.ros.org/mailman/listinfo/ros-users