The control objective for the jacketed stirred reactor process is to minimize the impact on reactor operation when the temperature of the liquid entering the cooling jacket changes. We have previously established the performance capabilities of a PI controller in rejecting the impact of this disturbance.
The same tuning recipe we successfully demonstrated for PI control and PID controldesign and tuning can be used when a controller output (CO) filter is added to the heat exchanger process control loop. Here we explore PID with CO Filter control using the unified (controller with internal filter) form. We showed in this previous article […]
The derivative action of a PID controller can cause noise in the measured process variable (PV) to be amplified and reflected as “chatter” in the controller output (CO) signal. Signal filters, implemented as either analog hardware or digital software, offer a popular solution to this problem.
In our study of the derivative mode of a PID controller, we explored how noise or random error in the measured process variable (PV) can degrade controller performance. As discussed in that article, derivative action can cause the noise in the PV measurement to be reflected and amplified in the controller output (CO) signal, producing […]
We have explored disturbance rejection in the gravity drained tanks process using P-Only and then PI control. In the PI study, we confirmed the observations we had made in the PI control of the heat exchanger investigation. In particular, we learned that PI controllers: ▪ can eliminate the offset associated with P-Only control, ▪ have […]
At the start of a recent Practical Process Control workshop, I asked the attendees what the “D” in PID stood for. One fellow immediately shouted from the back of the room, “Disaster?” Another piped in, “How about Danger?” When the laughter died down, another emphatically stated, “D is for Do not use.” This one got […]
In recent articles, we investigated P-Only control and then PI control of a heat exchanger. Here we explore the benefits and challenges of derivative action with a PID control study of this process. Our focus is on basic design, implementation and performance issues.
The design and tuning of a three mode PID controller follows the proven recipe we have used with success for P-Only control (e.g., here and here) and PI Control (e.g., here,here and here). The decisions and procedures we established for steps 1-3 of the design and tuning recipe in these previous studies remain unchanged as […]
Like the PI controller, the Proportional-Integral-Derivative (PID) controller computes a controller output (CO) signal for the final control element every sample time T. The PID controller is a “three mode” controller. That is, its activity and performance is based on the values chosen for three tuning parameters, one each nominally associated with the proportional, integral […]
A valve cannot open more than all the way. A pump cannot go slower than stopped. Yet an improperly programmed control algorithm can issue such commands. Herein lies the problem of integral windup (also referred to as reset windup or integral saturation). It is a problem that has been around for decades and was solved […]