The Overbot: An Off-Road Autonomous Ground Vehicle Testbed

The Overbot, originally designed to run the DARPA Grand Challenge, has been retasked as an off-road autonomous vehicle testbed. The base chassis is a Polaris Ranger 6x6 gasoline powered off-road vehicle. It has a single cylinder 30 HP engine capable of propelling the vehicle to over 40 mph. In addition to the chassis, the Overbot is equipped with a SiCK LiDAR on a custom gimbaled mount, a color firewire camera in a waterproof housing, a Crossbow AHRS, a Novatel differential GPS system and several modified 802.11.b wireless hubs. In terms of actuation, there are five Galil Motion Controllers which drive servomotors that handle shifting (H-L-N-R), braking, throttle, steering and the vision angle. Software which performs obstacle detection, path planning and low-level control is implemented in a Real Time Operating System (RTOS) on a standard Pentium class PC. The original incarnation of the Overbot was selected to run in the National Qualifying Events (NQE) of the Grand Challenge in both 2004 and 2005, but failed to proceed to actual competition. The Overbot is a very agile off-road platform, capable of passing over obstacles as high as 15 inches. Demonstration of new path following control shows crosstrack errors that are less than 1 meter and a new heading correction implementation is discussed.