DeltaV Tune can be used on various processes that operate over a wide dynamic range. This section describes how the default settings associated with trend scaling, testing amplitude, and duration can be changed to compensate for the process range or operating conditions. Following the information in this section ensures that the best possible tuning is achieved for all operating conditions. The Expert selections available in tuning and the options available for saving or printing block tuning are discussed as well. Also included is detailed information about the offline simulation capability that is provided with this product to support DeltaV Tune training.
Modifying the DeltaV Tune Trend Display Area
In the top of the DeltaV Tune window, a trend of the block PV, output, SP, and actual mode is shown. You can adjust the time frame displayed for the parameters shown in the Trend display area using the following selections shown in the toolbar:
The span of the PV, SP, and Output are initially displayed in full range. You can modify the trend range to show values over a smaller or larger range than the default value. In the Controller panel, right-click the box associated with the parameter (SP, OUT, or PV) whose trend range is to be modified.
Scroll Back - Shifts the trend information back in time
by one screen.
Small Back - Shifts the trend information back one unit
in time.
Small Forward - Shifts the trend information forward
one unit in time.
Scroll Forward - Shifts the trend information forward
in time by one screen.
Decrease time span - Decreases the time represented
by the Trend display area by approximately 25 percent.
Increase time span - Increases the time represented by
Then, click Set Y Scale and select either Manual or Auto Scale.
Select either the Compress range or Expand range button provided in the toolbar:
Expert Feature
The Expert feature allows you to retain all Normal selections and select your specific tuning rule to use with the loop response in calculating the best tuning of a PID block. When you click Options | Expert, the available tuning methods for the PID are displayed in the Control Panel area, as shown in the following figures. The figure on the left shows the tuning method selections for non-integrating process and the figure on the right shows the selections for integrating processes. Enable this option by selecting the Integrating process checkbox in the Test Process area.
Compress range - Reduces the span of the selected
trend range by approximately 10 percent.
Expand range - Increases the span of the selected trend
Note: If you are using the Expert feature you should have expert knowledge of the process you are tuning. You must use the Expert feature
with care and always check that the time constant DeltaV Tune calculates represents the actual process time constant. Because the Normal tuning rules give good results in most cases, we recommend the use of the Normal selection for most applications.
Some of the tuning rules provided in advanced tuning are very specialized. For PID and PI loops, use Lambda or IMC tuning rules first. These settings should be satisfactory in most cases. If you have a thorough understanding of loop tuning, you can use some of the alternate tuning rules. If the tuning results are not satisfactory, you can change the rule selection.
For non-integrating processes, the Expert selection provides the following tuning rules:
Ziegler-Nichols - PI - This tuning rule provides the basic rules for calculating controller settings from ultimate gain and ultimate period.
Lambda - PI - This tuning rule allows the desired ratio of closed loop time constant to open loop time constant to be specified through the Lambda factor.
Lambda - Smith predictor - This tuning rule should be used with the PID_DEADTIME Module Template.
Internal Model Control - PID - This tuning rule provides proportional, integral, and derivative control and assumes a first order process with a time delay. During tuning, the model is identified and the tuning values are calculated. The procedure for identifying the model is a patented Fisher-Rosemount Systems technique.
For integrating processes, the Expert selection provides:
Lambda - Averaging Level - PI - This tuning rule is similar to the Lambda tuning rule, but it works for integrating level loops. The IMC tuning rule is especially useful when a process deadtime is longer than half of the process time constant. The process deadtime and the process time constant are shown in the Process Test panel.
when using the Normal selection.
When a process deadtime is equal to or greater than the process time constant, it is beneficial to apply Smith Predictor. For more information regarding application and tuning details, refer to the PID_DEADTIME Module Template topic.
To change the Expert setting, you do not have to retune the loop. Once DeltaV Tune has obtained the process dynamics for a loop, DeltaV Tune can calculate new controller settings for different Expert selections.
Saving and Printing Block Tuning
When tuning a block, you can save the current test data to a file by clicking File | Save File. The parameter values used in the tuning process are saved in the DeltaV Tune folder under DVData. By clicking File | Save File As, you can specify the folder. When you have finished tuning and are closing DeltaV Tune, you are also given an opportunity to save. When initiating DeltaV Tune, it is possible to start the tuning process using previously saved values.
After tuning a block, you can obtain a hard copy of the tuning parameters and selections made in DeltaV Tune. You can initiate this request either by selecting the Print option under File or selecting the print icon in the toolbar. In response, a single page summary of the parameters used in tuning is printed on the user-specified printer.
The Simulator Configuration
As part of DeltaV Tune, two modules containing simulated PID and FLC blocks are provided with your DeltaV system. These modules can be used as a training tool that allows you to become familiar with the tuning procedure before applying it to the actual process.
The simulator modules contain function blocks that simulate a heater process. In order for these modules to be referenced by DeltaV Tune, you only need to download the simulator modules to a DeltaV controller.
The following module templates found in the DeltaV library for the process simulator are provided in the Simulate folder:
DeltaV Tune Simulator Modules
Description Tag Comments
PID Loop and Process Simulation
SIM_SR_PID PID test loop with process simulation
Note You only need to download the simulator modules to one DeltaV controller.
You can view the simulation modules with an interface created by special simulation Dynamos. When you select the detail display from the faceplates for these Dynamos, a representation of the simulated process is shown. These simulator modules do not use real I/O; therefore, they will not interrupt any other module's operation currently running in the controller.