Obstacle Avoidance and Navigation in the Real World by a Seeing Robot Rover, Hans Moravec, 1980
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Appendix 3: Overview

The following eleven pages contain pictures of some of the obstacle avoider's internal state from step to step in a successful run.

Each diagram is a plan view of the world at a stopping position. The grid cells are two meter squares, conceptually on the floor.

The cart's own position is indicated by the small square that moves from diagram to diagram. The third component of its position, namely its height, is shown by the graph, calibrated in centimeters, to the left of grid. Since the cart never actually leaves or penetrates the floor, this graph provides an indication of the overall accuracy of the system.

The irregular, tick marked, line behind the cart's position is the past itinerary of the cart (as deduced by the program). Each tick mark represents a stopping place.

The picture at top of the diagrams is the view seen by the TV camera at the various positions. The two rays projecting forward from the cart position show the horizontal boundaries of the camera's field of view (as deduced by the camera calibration program).

The numbered circles in the plan view are features located and tracked by the program. The centers of the circles are the vertical projections of the feature positions onto the ground. The size of each circle is the uncertainty (caused by finite camera resolution) in the feature's position. The length of the 45° line projecting to the upper right, and terminated by an identifying number, is the height of the feature above the ground, to the same scale as the floor grid.

The features are also marked in the camera view, in the guise of numbered boxes. The thin line projecting from each box to a lower blob is a stalk which just reaches the ground, in the spirit of the 45° lines in the plan view.

The irregular line radiating forwards from the cart is the planned future path. This changes from stop to stop, as the cart fails to obey instructions properly, and as new obstacles are detected. The small ellipse a short distance ahead of the cart along the planned path is the planned position of the next stop.




Figure A3.1: The initial position. Requested destination is 16 meters ahead




Figure A3.2: The second stop. Three obstacles to avoid




Figure A3.3: The third pause. Avoiding the chair




Figure A3.4: The fourth stop




Figure A3.5: The fifth stop




Figure A3.6: The sixth stop




Figure A3.7: The seventh stop. Now to get around the icosahedron




Figure A3.8: The eighth stop




Figure A3.9: The ninth stop. The world model is drifting




Figure A3.10: The tenth stop




Figure A3.11: The eleventh stop. Time to skirt the fake tree


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