Page 151 - Anatomy of a Robot

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136 CHAPTER FOUR
COMPARABLE SYSTEMS
During the design of the robot, look for comparable designs. Others have already
designed many of the subsystems in one fashion or another. If the design of the robot
is a significant departure from standard designs, then conduct more reviews of the
design. With luck, new ground is being broken. Without luck, a disaster might be in the
making.

ACID TEST
When I was at college at Cornell, a rumor was going around, the very sort of thing
spread by young college kids with little experience. To this day, I’m not sure if it’s true
or not. It seems I have gained little sense since! The campus has two deep gorges, one
spanned by a tiny suspension bridge that wobbles as it’s crossed. It was said that the
architecture school conducted a design contest for the bridge. The student with the win-
ning design, returned and was surprised to see his design spanning the gorge, and
refused to cross the bridge!
We must be willing to be cradled in the metal arms of our creation. If we tremble at
the thought, we should review our designs!

PLAN ON FAILING

Face it; nothing works as planned. Unforeseen circumstances always take place in life
and in projects. The prudent thing to do is to plan for recovery while standing amid the
ashes of failure. A couple of precautions can be taken.

Watchdog

Most complex computerized systems will just plain fail now and then. The reasons may
never even be discovered. It is often helpful to design a “watchdog” circuit that can reset
the computer system or restart the robot if it fails to regularly interrogate the watchdog.
The existence of a watchdog circuit generally increases the availability of the robot and
only rarely interferes unnecessarily.

Backup Plans
We might as well plan for portions of the robot to fail. If the robot is to be autonomous,
or in a position where it cannot be repaired, then special attention should be paid to
backup systems. We already talked about N 1 redundant systems, but other options