Page 433 - Sensing, Intelligence, Motion : How Robots and Humans Move in an Unstructured World

408 SENSITIVE SKIN—DESIGNING AN ALL-SENSITIVE ROBOT ARM MANIPULATOR

system equipped with it was the first whole-body motion planning system. It is a
custom-built skin, designed specifically for the robot shown. The skin consists of
three large sections covering the second and third link of the robot arm—which
are by far the robot’s biggest links, so covering them effectively takes care of all
robot parts that are subject to collision. (Motion planning still has to be done for
the whole robot major linkage, in three-dimensional space.) Common components
and simple soldering was used to produce the skin; its most protruding parts,
LEDs, make the skin rather thick, about 6 mm.
The robot arm “under the skin” is a General Electric industrial arm manipu-
lator. The skin resolution (distance between neighboring sensors on the skin) is
about 5 cm, resulting in slightly more than 500 sensors total on the skin. The
cuts in the front part of the skin were necessary to cover the robot’s roundish
endpoint. Note also that no hand or other end effector appears in the figure. As
discussed in prior chapters, motion planning for the end effector (that is, the
robot’s minor linkage) is treated as a separate task, which is usually much easier
due to the hand’s small size.
A more advanced version of the sensitive skin system (built in 1993–1996) is
shown in Figure 8.7. The skin consists of standardized sensor modules (they can
be seen in the figure), each about 20 by 20 cm in size and including 8 × 8 = 64
sensors and necessary local control electronics. Module dimensions are chosen
so that the distance between border sensors of two neighboring modules is equal
to the normal between-sensor distance within a single module. This, along with

Figure 8.7 This robot is equipped with the 1993–1996 skin version. The skin is made of
standardized sensor modules, each 23 by 23 cm in size and includes about 1200 infrared
proximity sensors.