Submitted by Greg McMillan on Fri, 05/03/2013 - 15:43
A unified approach to tuning has been found that enables a common and simplified method for setting PID tuning parameters. Key features can be used to eliminate the need for retuning to deal with different dynamics and objectives.
Category: Tips PID Controllers External-reset Override Control PID Form PID Output Limits PID Migration PID Tuning
Submitted by Greg McMillan on Thu, 02/14/2013 - 12:45
Older Distributed Control Systems (DCS) and analog controllers tended to have different tuning setting units and methods of implementing integral and derivative action. A lack of understanding of the difference between the old and new PID features and tuning settings can lead to poor and even unstable control when migrating...
Category: Tips PID Controllers External-reset PID Options PID Structure Setpoint Filter Setpoint Rate Limits Overshoot Two Degrees Of Freedom PID Setpoint Lead-lag
Submitted by Greg McMillan on Wed, 11/28/2012 - 13:36
What are the relative merits of different PID structures, a setpoint (SP) filter, and analog output (AO) setpoint rate (velocity) limits? Should I seek a general solution I can use all the time and each knob fits a particular purpose, or a controller with fewer knobs that does exactly what...
Category: Tips PID Controllers External-reset PID Options PID Output Limits PID Structure Anti-reset Windup Overshoot Saturation Smart Reset
Submitted by Greg McMillan on Tue, 11/20/2012 - 17:38
Anti-reset windup (ARW) protection is a standard feature of industrial PID controllers. In some DCS, ARW limits are adjustable besides output limits. The ARW limits may not be at their best values. ARW default values may not match up with output limits as output scale and engineering units change.
Submitted by Greg McMillan on Fri, 08/24/2012 - 15:38
Cascade control is an effective way of providing better feedback and feedforward control. The peak error in the primary loop can be reduced by more than an order of magnitude for disturbances originating in the secondary loop.
Category: Surge Control Blending Cascade Control Deadtime Compensator Decoupling External-reset Feedforward Override Control Valve
Submitted by Greg McMillan on Thu, 04/26/2012 - 16:45
The value of a key PID feature is increasingly becoming apparent. I got a preview of the importance when I found the 1980s vintage DCS required a fix for override control that was inherently addressed in the next generation of DCS by this feature.