The Cye Personal Robot Path Planner


Robust mobile robot navigation in real world environments is a long standing problem in robotics. In this paper, we describe research in navigation and path generation using the Probotics Cye robot. Cye is a 2-wheeled differential drive robot, whose primary mode of navigation is ded-reckoning. The only sensors are wheel encoders - there are no other active or passive sensing modes. The accuracy of the ded-reckoning is sufficient for indoor navigation, through the use of carefully designed wheels and a set of known calibration surfaces, or "check points". An (inaccurate, incomplete) map of the world is interactively constructed using Cye, in which known free space, known obstacle areas, and unexplored areas are all marked. Path generation in such an environment has the following challenges:

We solve these problems using a novel approach to the potential field method. In the first stage, a standard potential field describing the distance of any given world point to the nearest obstacle is created. In this field, unexplored areas are marked with a predetermined "pseudo-distance". This pseudo-distance is key to allowing the use of unexplored areas when necessary. In the second stage, a potential field is created in which each world point is the distance to the goal, non-linearly weighted by that point's distance to the nearest obstacle. The weighing is done such that points very close to an obstacle or points in unexplored areas avoided if at all possible. However, if a complete path cannot be generated in "safe" areas, then the path will use these potentially unsafe areas. After an initial path is found using this method, the next step is to search for checkpoints. This is done by growing out a field from the complete path, to measure the distance from known checkpoints to the path. A search is then done which minimizes the robot's deviation, while finding checkpoints which are necessary to reduce error. After an appropriate set of checkpoints are found, the system plans paths to these checkpoints using the above method.

This planner has been operating in the real world now for about 4 months, and is being used by robotics hobbyists and researchers. The robot is capable of navigating distances of over a 1/10th of a mile indoors, through narrow corridors and doorways, completing its path without getting lost.


The Cye Robot:
The CyeSR

Path Planner:


Batavia, P. H., Nourbakhsh, I., Path Planning for the Cye Robot,, Submitted to the IEEE International Conference on Robots and Systems, 2000.

Parag Batavia, The Robotics Institute, Carnegie Mellon University
Last modified: Thu Apr 13 10:17:21 EDT 2000