Page 373 - Sensing, Intelligence, Motion : How Robots and Humans Move in an Unstructured World

348 HUMAN PERFORMANCE IN MOTION PLANNING

Obstacles
Handles

Links

Figure 7.10 The physical two-link arm used in the tests of human performance.

up more often than younger subjects before reaching the solution. (c) The level
of one’s education and professional orientation seems to play an insignificant
role: Secretaries do as well or as poorly as mechanical engineering PhDs or
professional pilots, who pride themselves in their spatial reasoning.

The Physical Arm Test Setup. This experimental system has been set up in
a special booth, with about 5 ft by 5 ft floor area, enough to accommodate a
table with the two-link arm and obstacles, and a standing subject. The inside
of the booth is painted black, to help with the “move in the dark” test. For a
valid comparison of subjects’ performance with the virtual environment test, the
physical arm and obstacles (Figure 7.10) are proportionally similar to those in
Figure 7.5. (Only two obstacles can be clearly seen in Figure 7.10; obstacle O 1
of Figure 7.5 was replaced for technical reasons by two stops; see Figure 7.10.)
For the subjects’ convenience the arm is positioned on a slightly slanted table.
Each arm link is about 2 ft long. A subject moves one or both arm links using the
handles shown. During the test the arm positions are sampled by potentiometers
mounted on the joint axes, and they are documented in the host computer for
further analysis, together with the corresponding timing information. 7
Special features have been added for testing the scene visibility factor. Opening
the booth doors and turning on its light produces the visible scene; closing the

7 The physical arm and the booth system, including hardware, electronics, and related software, have
been designed by Branimir Stankovic and Steve Seaney at the University of Wisconsin Robotics
Laboratory [120].