Page 53 - Practical Control Engineering a Guide for Engineers, Managers, and Practitioners

28 Chapter Two

Pay me Now ... or ... ePay me Later
FIGURE 2-7 The old Fram oil filter phrase.

How often does this happen? Rarely. It is difficult to convince
a project manager to authorize the extra money to design-in the
necessary ports. However, it is another example of "pay me now
or pay me later" (a phrase from the perhaps famous Pram oil filter
advertisements sometimes seen in the 1950s; Fig. 2-7). The money
lost in designing the extra ports will pail in comparison to the
costs of the engineering time required to diagnose and solve the
problem.

Problem Solving with Bundling
The key to problem solving is having access to both the so-called pro-
cess and the controller. H ports are in place then problem solving can
be divided immediately into verifying that the process and the con-
troller are performing properly. Without these ports problem solving
becomes a guessing game (see Fig. 2-8).
There are ancillary benefits to having the extra ports. During
product development, the ability to monitor the process and con-
troller separately can allow for parallel beneficial development (see
Fig. 2-9). H the learning about the process and controller are concur-
rent and interactive, their development can be also be interactive-
leading to a synergism and a better final product.

Test control
separately
Tune
1----- Success ~
,
,-

Failure
Bundle process and • O Try SMILH
control then Tune J, r
Crisis mode

FIGURE 2-8 Bundling process and control as part of a saleable product-
testing the process and the algorithm separately.