This is a case about a mechanical engineer working on a civil
engineering project in which the problem is an electrical device.
The case should convince students of the ecumenical nature of
engineering. The engineer, Bill Clemens, works for the Bureau of
Reclamation. His first project is to try and cure a hunting
problem with the "Little Man," a device which is used to sense the
level of the water behind an irrigation dam, and which controls
the operation of the spillway. The control under changing
conditions "overshoots" and "under-shoots" and causes oscillations
in the irrigation canals. The "Little Man" is an electrical
device which senses the level of the water and signals the
spillway control to either open or close.
The problem is not trivial. The details of the control and
Bill's eventual solution make it possible for students to
undertake the solution of the problem and to compare their
solution with Bill's. Although Bill produces a modification which
he thinks will cure the problem, it becomes obvious after
examination that it will not do so completely. Other changes are
needed to make the control operate satisfactorily.
This case has been used several times with mechanical
engineering students and always elicits a great deal of
excitement. The attempts to describe exactly what the problem is
and what causes it can lead to a greater appreciation of control
theory and dynamics. Considering the solution proposed by Clemens
can give students considerable insight into how some control
problems can be solved. Finally, the problem of how to design a
suitable control that will completely cure the problem is an
exercise in creativity.
