Classical Designs

Abstract

In Chapter 1, the PID control structures and components have been examined. In this chapter, simple methods for tuning the controller, i.e., selection of K_c, T_i and T _d will be provided. These include a heuristical approach based on trial and error, and several classical systematic methods which involve conducting an experiment, determining a process model and using known tuning methods to determine the control gains instead of a trial and error basis. Systematic methods are worthwhile and necessary for certain cases:

• 1. Important loops where control performance is critical and important.

• 2. Difficult loops where trial and error methods, and the usual rules of thumb are not applicable or effective.

• 3. Slow loops which will take far too long time to test each new setting for trial and error methods to be feasible, in which case it is often worth calculating a setting using systematic approaches.