Page 128 - Designing Autonomous Mobile Robots : Inside the Mindo f an Intellegent Machine

Basic Navigation Philosophies

At the high end, cleaning robots have used sensor-based local navigation that pro-
vides efficient area coverage, but only within a contiguous and bounded area. If
these robots are not to enter a certain area, then physical barriers such as roadway
cones are used to accomplish this.

In none of these cases, however, has the robot been capable of understanding its glo-
bal position and going from one area to another to do things in a specific manner. To
do this, the robot must by very definition be programmed in some way.

Virtual path following vs. goal seeking

There are two basic philosophies about how a robot should find its way from one
place to another: virtual path following and goal seeking. Goal seeking has traditionally
been the favorite method of academia. In goal seeking the robot knows where it
wants to go in terms of coordinates and it plans the best route to achieve the goal. In
doing so, it may or may not be provided in advance with a map of known obstacles. In
any case, as it encounters new obstacles it will build a map of them.

Virtual path following

Virtual path following is essentially like physical path following except that the path
is defined in the programs of the robot and not by painting a stripe on the floor. A
virtual path-following robot will typically have a path program defined either graphi-
cally or as a text program or both.

Cybermotion robots, for example, execute pseudocode programs that require the
transmission of very little data. These programs are generated using a graphical
environment called PathCAD (Figure 7.3). In the PathCAD environment, graphi-
cal objects that are dropped onto the drawing have properties that are carried
invisibly with the drawing. These objects include nodes with names such as V1, V2,
and E3 on Figure 7.3.

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