Jun
03
Before tuning calculations are applied in a control loop, it is good to consider how much the process gain and deadtime can change before the loop becomes unstable. In the DeltaV control system, this information is provided using a robustness plot that shows gain margin and phase margin as illustrated below. Information on this type …
May
27
When the control objective is to maintain the controlled parameter of an integrating process at setpoint under all operating conditions, then using PI (proportional-integral or proportional plus reset) controller, it is possible to automatically compensate for changes in disturbance inputs and maintain the controlled parameter at setpoint. However, the application of PI control to an …
May
20
Intermediate liquid storage tanks (surge tanks) are commonly installed between processing areas of the plant. Under normal operating conditions, these storage buffers allow each process area to be operated independently of the other process areas. Any imbalance in the area production rates within a plant will be reflected by a change in level of the …
May
13
Older control systems may not include tools that allow the PID tuning to be automatically established. In such cases, the following procedure outlined in Chapter 12 of Control Loop Foundation – Batch and Continuous Processes may be quickly applied to determine the tuning of a self-regulating process for PI control. In Chapter 4 of Advanced …
May
06
Control system manufacturers have adopted different technologies to implement on-demand tuning. Because these tools are designed to work in a noisy process measurement environment, the tuning results are usually better than those achieved through manual tuning techniques. To illustrate the features that may be included in on-demand tuning capability, the on-demand tuning capability of the …
Apr
22
When the on-demand tuning application resides in a DCS workstation, communications between the controller and the workstation can introduce variable delay and jitter in the observed process response. As addressed in Chapter 4 of Advanced Control Foundation – Tools, Techniques, and Applications, the process may be more accurately identified by distributing the on-demand tuning functionality …
Apr
15
During the commissioning of feedback control based on the PID algorithm, the PID tuning parameters (that is, the proportional, integral, and derivative gain) must be set to specific values to achieve the best controller response to setpoint and disturbance input changes. To minimize process variations and the response time to setpoint and disturbance input changes …
Apr
01
In some cases, the manipulated parameter of one control loop can impact the controlled parameter of another control loop as illustrated below. To allow both loops to operate in automatic mode, loop interaction is most often addressed by simply detuning one of the control loops by reducing the proportional gain. The valve (or another final …
Mar
04
A Loop tuning has a significant impact on control loop utilization and performance. Controller tuning parameters can be easily changed over a wide range to adjust loop operation for various process requirements. However, some expertise in tuning is required even when advanced control tools are used, and there is a chance that the behavior of …
Dec
17
Professor Åström is well known throughout the world for his work in process control. The book he co-authored with Tore Hägglund, Advanced PID Control, is one of the most comprehensive texts on this topic. In the early 1990’s Professor Åström was a consultant to the Emerson team that did the basic research for the development …
