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RELIABILITY, SAFETY, AND COMPLIANCE 145
components can be single components or entire robots. The statistics and math
behind the statistics are difficult. Some of the techniques are described at www.
asnt.org/home.htm.
PERFORMANCE TESTS

Most robots will have specific tasks they should be able to carry out. Some of these
tasks will be measured qualitatively and some will be measured quantitatively. Test
engineers make a full test regimen and then execute it to determine if the robot passes
muster and meets specifications. Each aspect of the robot’s performance can be meas-
ured, and the quantitative performance statistics can be gathered. Some performance
tests are as follows:

Full test The entire test is executed and may take days to complete. The goal is
to get a complete read on how well the robot performs a baseline.
Regression test This is a subset of the entire test and may be executed many
times. The test is short because it must be inexpensive to execute, since it’s per-
formed so often. The test is executed every time the robot is changed in any sig-
nificant way. The goal of the test is to have a reasonable chance of uncovering any
errors that were introduced during the changes. Periodically, to gain further assur-
ance, the full test can be executed instead.
Unit tests Some software engineers segment the software programs into distinct
subsections. Each subsection has a specific function, which can be individually
tested. Along with writing a function, the software engineers sometimes write a
unit test for the function. When the software is compiled, the unit tests are all exe-
cuted to see if they still work. If the programmers accidentally changed the way
the function operates, the unit test for that function will likely fail and alert the
engineers of the problem.
Use tests Designs are not human and can’t be confounded by many “what ifs.”
What if the robot is turned on and somebody forgets to connect a connector? What
if buttons are pressed in the wrong sequence? What if the battery wears all the way
down? What if the wheels lock up, will the motor burn out?

All these sorts of events should be tried at least once to observe the results. If any-
thing untoward happens, then either the manual should be rewritten to prevent the event
or the design should be changed.
Reliability, safety, and compliance are areas where experience counts. When in doubt,
seek experienced help and advice. Many technically good designs fail to pass muster
when these topics are considered. Plan your approach well in advance.