Submitted by Greg McMillan on Mon, 10/22/2018 - 22:36
In many publications on process control, the common metric you see is integrated absolute error for a step disturbance on the process output. In many tests for tuning, setpoint changes are made and the most important criteria becomes overshoot of setpoint.
Submitted by Greg McMillan on Mon, 08/24/2015 - 23:04
The automation profession suffers from the lack of a common understanding of the terms used and their units. By taking a closer look at key terms for plant dynamics, we can have more intelligent discussions and better recognition of the contributing factors so that we can find what part of...
Category: External Reset Feedback Dead Time Enhanced PID Feedforward Control Valve Position Control Tips
Submitted by Greg McMillan on Fri, 04/18/2014 - 16:59
The power of the PID largely remains underutilized. Most of the options and parameters other than scale ranges and tuning settings remain at their defaults. Here we look how to tap into the incredible capability of the PID to minimize batch cycle time and start-up time and to maximize production...
Submitted by Greg McMillan on Fri, 12/20/2013 - 18:14
We conclude our review of nonlinearities with an overview of applications and a detailed list of simple solutions to minimize the adverse effects of this everyday problem in nearly all control loops. It is impressive how setting lambda equal to 3x the largest deadtime value helps to solve most nonlinearity...
Category: Dead Time Process Dynamics PID Tuning Process Gain Time Constant Tips Bioreactor Control Valve Position Control Variable Speed Pumps
Submitted by Greg McMillan on Fri, 12/06/2013 - 16:39
Here we use the broader definition of linearity to mean constant dynamics. A linear control loop has a constant total loop dead time, constant primary and secondary time constants, and a constant open loop gain. This perspective reviews the sources of dynamics and causes of nonlinearity.
Submitted by Greg McMillan on Tue, 11/19/2013 - 13:25
The speedup of a plant’s response can cause loops to go from a smooth to an oscillatory response. In actual plants, the faster rate of change of a process variable important for product quality such a temperature or composition occurs for various changes in operating conditions.
Submitted by Greg McMillan on Fri, 06/14/2013 - 16:46
A significant part of the challenge in understanding process control is the proper use of terms to describe the dynamics in a control loop. Communication can be greatly improved by focusing on three key terms and adding a few words to more aptly describe the source of the term.