PID Loop Analyzer is a software tool designed to help you optimally tune your control loops with very little process disruption. You perform an open loop bump test on your production loop and provide the test data to PID Loop Analyzer, and it models your process and suggests PID tuning parameters based on Lambda tuning rules. It allows you to select safe settings from aggressive to conservative. You may also select "Trial and Error" and tune it by trial and error. The first and most difficult step is getting process data out of your control system and into PID Loop Analyzer.
First you must perform an open loop bump test; document a few parameters, and key them into PID Loop Analyzer.
With the controller in manual and the process at steady state around its normal process target, step change the controller's output.
Make no other changes until the process returns to steady state. The output step must be large enough to noticeably change the
process variable, even in the presence of process noise. You may conduct multiple and bi-directional output steps.
Closely observe and document the following parameters while performing an open loop bump test. Note that you can document the first five parameters before performing the step test.
Click the FOPDT button in the bottom of the application window. You will be presented with the following dialog box.
Enter data into the appropriate fields and click "OK." You will be presented with a model of your process, recommended PID tuning parameters, and a trend showing how your controller will respond to a set point step change. An example follows.
The left trend area is your process model. The yellow trace is the model, and the white trace is the controller output. You can tweak the model by adjusting your original input data and clicking OK. You are now ready to analyze your PID loop and experiment with different PID tuning settings without experimenting with your production process. Moving the slider to the left makes the PID settings more aggressive. Moving it to the right makes them more conservative. Selecting Trial and Error allows you to change the PID settings and observe how your process will respond to the new settings.
Perform an open loop bump test. The test will produce a process response characteristic of an integrating process; the process variable will be changing at one rate before the step change and a different rate after the step change. An example follows:
Determine and document the following values. Most trend packages have tools such as scooters that will facilitate data gathering.
After you collect the data, click the Integrating button in the lower portion of the application window. You will be presented with a dialog box. Following is an example of a bump test with example date, a dialog box with the example data inserted, and the resulting model.
Enter data into the appropriate fields and click "OK." You will be presented with a model of your process, recommended PID tuning parameters, and a trend showing how your controller will respond to a set point step change. An example follows.
The left trend area is your process model. The yellow trace is the model, and the white trace is the controller output. You can tweak the model by adjusting your original input data and clicking OK. You are now ready to analyze your PID loop and experiment with different PID tuning settings without experimenting with your production process. Moving the slider to the left makes the PID settings more aggressive. Moving it to the right makes them more conservative. Selecting Trial and Error allows you to change the PID settings and observe how your process will respond to the new settings.