Page 432 - Sensing, Intelligence, Motion : How Robots and Humans Move in an Unstructured World

EXAMPLES 407

Figure 8.6 The first sensitive skin (mid-1980s). Skin sheets have been custom designed
to fit this specific General Electric robot arm. The system has over 500 infrared proximity
sensors.

Switch S1 selects the operating frequency of a particular sensor module. By
selecting the output of IC5b, the circuit operates at 67.5 kHz, or one-half the
frequency of the signal (modulation frequency) from the sensor interface circuit.
The lower frequency (67.5 kHz) is used for the link l 2 skin section, and the
higher frequency (135 kHz) is used on the skin of link l 3 . Note that from the
standpoint of motion planning these two links comprise practically the whole
arm (Figure 8.6).
The Skin. The skin base is manufactured from a plastic material called Kapton,
by Dupont Corporation, and is 0.26 mm (0.0085 in.) thick. (See Section 8.2 for
considerations affecting the choice of base material for the skin.) Both sides of
the material are copper-clad, resembling the (much thicker) inflexible material
commonly used for regular printed circuits. After processing, the board pro-
vides both the necessary structural support and electrical interconnection for
electronic components.
Once the skin design concept has been finalized based on preliminary exper-
iments, skin sections have been designed using common CAD-CAM software.
The actual production was done in a shop that had expertise in producing com-
plete circuit boards on flexible materials like Kapton; a number of such shops
have appeared in the United States in recent years.

8.4 EXAMPLES

The skin that covers the industrial robot arm shown in Figure 8.6 was built in
1985–1987. It is the first robot sensitive skin system ever built, and the robot