Design and Tuning Recipe Must Consider Nonlinear Process Behavior
ABSTRACT: Processes with streams comprised of gases, liquids, powders, slurries and melts tend to exhibit variations in behavior as operating level changes. This, in fact, is the very nature of a nonlinear process. For this reason, our recipe for controller design and tuning begins by specifying our design level of operation.
A Controller's "Process" Goes From Wire Out to Wire In
ABSTRACT: A controller seeks to maintain the measured process variable (PV) at set point (SP) in spite of unplanned and unmeasured disturbances. Since e(t) = SP - PV, this is equivalent to saying that a controller seeks to maintain controller error, e(t), equal to zero.
The Normal or Standard PID Algorithm
ABSTRACT: The question arises quite often, "What is the normal or standard form of the PID (proportional-integral-derivative) algorithm?" The answer is both simple and complex. Any of the algorithms can deliver the same performance as any of the others. There is no control benefit from choosing one form over another. They are all standard or normal in that sense.