Page 357 - Sensing, Intelligence, Motion : How Robots and Humans Move in an Unstructured World

332 HUMAN PERFORMANCE IN MOTION PLANNING

sensor. Other conditions may be more subtle: For instance, how do we make
sure that in the same scene the robot and the human have access to exactly the
same information? While one can never be absolutely sure that the conditions
under which human and robot performance are compared are indeed equal, every
effort has been made to ascertain this in our study.
To formulate the right questions, we will start in the next section with obser-
vations from a few experiments, and then move in the following sections to a
consistent study with more representative tests and statistics. Most of those lim-
ited experiments have been done by the author in the late 1980s while at Yale
University. 1
The surprising, sometimes seemingly bizarre results from these experiments
helped prompt discussion and sharpen our questions, but also indicated a need
for a more consistent study. The larger, better designed, and much more consis-
tent studies discussed in Sections 7.4 and 7.5 were undertaken in the mid-1990s
at the University of Wisconsin—Madison, within a joint project between two
groups: on the robotics side, by the author and graduate student Fei Liu, and on
the cognitive science side, by Dr. Sheena Rogers and graduate student Jeffrey
Watson, both from the University of Wisconsin Psychology Department’s Center
for Human Performance in Complex Systems.

7.2 PRELIMINARY OBSERVATIONS

We will start with a task that is relatively intuitive for a human—walking in a
labyrinth (a maze)—and will then proceed to the less intuitive task of moving
a simple planar two-link arm manipulator, of the kind that we considered in
Section 5.2 (see Figures 5.2 and 5.15). It is important to realize that in some
formal sense, both tasks are of the same difficulty: Moving in a maze amounts
to controlling a combination of two variables, x and y (horizontal and vertical
displacement), and moving a two-link arm also requires control of two variables,
representing angular displacement (call these angles θ 1 and θ 2 ).

7.2.1 Moving in a Maze

Many of us have tried to walk in a labyrinth (a maze). Some medieval monasteries
and churches have had labyrinths on the premises, or even indoors, to entertain its
visitors. Today labyrinths appear in public and amusement parks. The labyrinth
corridors are often made of live bushes cut neatly to make straight-line and
curved walls. The wall may be low, to allow one to see the surrounding walls;
in a more challenging labyrinth the walls are tall, so that at any given moment

1 Much of the software for this first stage and many tests were produced by my graduate students,
especially by Timothy Skewis. The human subjects used were whoever passed through the Yale
Robotics Laboratory—graduate students, secretaries, unsuspecting scientists coming to Yale for a
seminar, and even faculty’s children.