Page 40 - Practical Control Engineering a Guide for Engineers, Managers, and Practitioners

Qualitative Concepts in Control Engineering 15

Finally, if the main challenge is trying to maintain a process output
satisfactorily near a set point in the face of persistent stochastic dis-
turbances then the best approach probably should be the formation
of a problem-solving team to deal with both the process and the
environment.

1-8 What Is a Control Engineer?
So far we have implied that a control engineer designs control algo-
rithms. In fact, the title of control engineer can mean many things.
The following list, in no particular order, covers many of these
"things":
1. Installer of control/ instrumentation equipment (sometimes
called an "instrumentation engineer"): In my experience this
is the most prevalent description of a control engineer's
activities. In this case, the actual design of the control
algorithm is usually quite straightforward. The engineer
usually purchases an off-the-shelf controller, installs it in an
instrumentation panel, probably of her design, and then
proceeds to make the controller work and get the process
under control. This often is not trivial. There may be control
input sensor problems. For example, the input signal may
come from a thermocouple in an electrically heated bath of
some kind and there may be serious common and normal
mode voltages riding on the millivolt signal representing the
thermocouple value. There may be control output actuator
problems. There may be challenging process dynamics
problems, which require careful controller tuning. In many
ways, instrumentation engineering can be the most
challenging aspect of control engineering.
2. Control algorithm designer: When off-the-shelf controllers
will not do the job, the scene is often set for the control
algorithm designer. The vehicle may be a microprocessor
with a higher-level language like BASIC or a lower-level
language like assembly language. It may even require
firmware. Many control/instrumentation engineers fantasize
about opportunities like this. They have to be careful to avoid
exotic custom undocumented algorithms and keep it simple.
3. Process improvement team member: Although this person is
trained in control engineering, success, as we shall see in
Chap. 2, may result from solving process problems rather
than installing new control algorithms.
4. Process problem solver: This is just a different name for the
previous category although it may be used when the team
members have developed a track record of successes.