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

in the 1990s [135]. These included our own work on whole-sensitive robot
manipulators, as well as joint projects with industry and government labora-
tories (in particular, with Hitachi Corp. [136]—an attempt to develop sensitive-
skin-clad robot toys—and with Sandia National Laboratory, US Department of
Energy—work on large sensitive-skin based robot manipulators for cleaning
chemical and nuclear waste dumps).
The first Sensitive Skin Workshop, convened in November 1999 in Wash-
ington, DC under the aegis of the National Science Foundation (NSF) and the
Defense Advanced Research Projects Agency (DARPA), brought together about
60 researchers from academia, industry, and government agencies. One surprise
at the Workshop was the interest to sensitive-skin-based devices in a number of
large Fortune 500 companies. The Workshop created a community of like-minded
people, along with an opportunity for discussions and joint work. Details about
the Workshop, along with information about some ongoing work by its members,
can be found in the book called Sensitive Skin [137].
The following years saw an increased activity in this area. Specifically, we
should mention works on development of suitable materials for the skin base.
While some of this work is lacking explicit references to robotics, its relevance
to systems discussed in this book is obvious. In recent years the annual meetings
of the Materials Research Society have featured one or more sessions devoted
to “smart skins,” “smart textiles,” and similar topics of obvious relevance to the
robot sensitive skin. Interesting works have been reported on stretchable materials
(see the discussion on this in the next section) capable of holding (stretchable)
wires, and on sensitive skin electronics [138, 139].
An overall diagram of the flow of information in a robot system equipped with
the sensitive skin is shown in Figure 8.1; in the figure, software blocks are shown
by straight rectangles, and hardware items are shown by curved rectangles. As the
robot moves in the course of executing its task, it is expected to avoid obstacles on
its way. It is the sensitive skin covering its body that will be informing the robot
of the approaching obstacles. (Which is not to say that other sensing means, such
as vision, would not be of use in this process.) To secure this information, the
robot control system continuously interrogates the whole array of skin sensors. 1
The sensor sampling rate and the corresponding hardware are designed so as to
fit comfortably within the update rate of the robot actuators—which for the robot
system described in this chapter is 50 position points, or sampling cycles, per
second, or 50 Hz. (This figure is quite typical for today’s complex robots.)
A position point is a set of n numbers that describe increments in the robot
actuators (motors, degrees of freedom) that have to be executed in order for
the robot to arrive at the desired position at the next step. For our robot, n = 6
(which is, again, a rather typical number in today’s arm manipulators). As the
robot simultaneously executes those six increments, a step motion along the robot
path is generated, and so on, 50 steps per second, producing a continuous motion.

1 This is not unlike the human control system, which monitors the sensing information from the
skin sensors.