Visually-Guided Obstacle Avoidance in Unstructured Environments

This research has been performed by Liana Lorigo, advised by Professors Rodney A. Brooks and W. Eric L. Grimson. Funding is provided by Jet Propulsion Laboratories and an NSF graduate fellowship.

The current objective is two-fold. The direct application is a system suitable for a Mars Rover robot, which would move autonomously upon the rocky, crater-full Martian surface, gathering soil and atmospheric samples and images. At its mission's completion, the Rover would return to its lander/spacecraft for its journey back to Earth. The general computational goal is to push the limits of existing vision technology, as applied to this problem, thus determining the modifications, assumptions, and simplifications necessary for a complete visually-guided robotic system in this real-time, real-world environment.

A Modular Obstacle Avoidance System (click for algorithm description)
This work addresses the problem of designing a mobile robot to avoid obstacles while traveling in unstructured environments, that is, environments for which no knowledge of the appearance of the ground or the locations or appearance of the obstacles is available. An autonomous obstacle avoidance system has been designed and implemented. With this system, Pebbles can travel around various cluttered environments safely. The only sensor used is a single uncalibrated camera at the front of the robot.

Image of Mars surface from Viking 2 lander.
One goal of this research is the development of a robotic system to explore the Martian surface by using visual cues to avoid rocks and craters too large to traverse. Some of the settings in which the system was tested -- rough outdoor areas and an indoor room of rocks and gravel -- were motivated by this surface. The system was also tested in several other indoor settings, such as lounges, corridors, and offices.

The system is housed in the Pebbles III Robot, designed and built by IS Robotics, Inc.
Pebbles is equipped with a Motorola 68332 processor and a Chinon 3mm camera positioned at the front of the robot 10.5 inches off the ground. Furthermore, the system uses a visual-processing hardware system, the CVM (Cheap Vision Machine), designed by Ian Horswill and Chris Barnhart. The processor is a Texas Instruments C30 DSP. The vision software is written in C and runs on the CVM. The system runs a smaller control program, written in L (a subset of LISP written by Professor Brooks) on the 68332.


Throughout development, the obstacle avoidance system has been tested cumulatively for over 100 hours and successfully avoids obstacles in a variety of environments including various carpeted rooms and a rough simulated Martian surface. Obstacles include rocks, furniture, walls, and people. Preliminary outdoor trials have also been performed.(Click on the pictures below for full-size pictures.)

MPEG Video Clips

  • Pebbles traveling in a cluttered environment. (BEWARE: 1053K MPEG)
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    Liana M. Lorigo <>
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    Last modified: Sat Apr 6 17:44:35 1996