Investigate the behavior of a process under closed loop control.

It needs to be done on loop pro software. Do not worry about the data. I just want you to do the memo report and write about the topic and analyze based on the instructions.
Laboratory 4
For this laboratory we will investigate the behavior of a process under closed loop control. We will work with a system that exhibits second order plus dead time. The attached instructions and worksheets describe in detail the procedures used to set up the model system. After setting up the model, you will attempt to tune the control by trial and error.
The process simulated shows several features of processes encountered in real plants. There is realistic noise on the process signals. In addition, the simulation shows common non- linarites likely to be encountered in a second order plus dead time (SOPDT) system.
When you complete the lab, you will submit a memo report to Beach Board. As for the previous memo reports, the introduction should state the problem being considered. The objective, purpose, and scope of the report should be clearly described.
The body of the report will summarize the theory and background of the system described on the following pages. Your results should include plots of the data obtained from the simulations along with a discussion of the process behavior. You summary and conclusions should discuss the non-linear nature of this system.
As with other memo reports, supporting data should be included in a separate ZIP file uploaded to Beach Board. You can include a scan of your worksheets in the ZIP file or hand them in separately.
Workshop 4: The Hazard of Tuning PI Controllers by Trial and Error
Objective: To build intuition about PI controller performance and tuning when the control objective is disturbance rejection. Also, to experience the drawbacks of trial and error tuning.
Reference: Practical Process Control Chapters 6-9
1) Here we explore the tuning of a PI controller by trial and error when disturbance rejection is the control objective. The process will be an ideal linear simulation designed using Custom Process. Start by clicking the Custom Process button on Loop Pros main screen and then choose Single Loop Process from the list.
When the simulation starts, notice that the graphic to the right of the scrolling plots is comprised of a Process button, Disturb(ance) button and Controller button (the C in the white circle).
To create the simulation, click the Process button on the graphic. This opens a Construct Process and Disturbance Models form. First specify the controller output to measured process variable dynamic behavior. Click the Process Model tab (it should already be active if you have not done any exploring) and select from the list of models available, the:
– Overdamped Linear Model
– Self Regulating (Stable) Process.
Enter the process gain, three time constants and dead time that define the controller output to measured process variable dynamic behavior of this overdamped linear third order plus dead time model:
Process Gain, KP
First Time Constant, P1 Second Time Constant, P2 Third Time Constant, P3 Lead Time, PL
Dead Time, P
= 1.0 = 10.0 = 1.0 = 1.0 = 0 = 1.0
Next specify the behavior of the disturbance to measured process variable dynamics. Click the Disturbance tab at the top of the form, ensure that Overdamped Linear Model is selected, and enter:
Disturbance Gain, KD
First Time Constant, D1 Second Time Constant, D2 Third Time Constant, D3 Lead Time, DL
Dead Time, D
= 1.2 = 12.0 = 1.2 = 1.2 = 0 = 1.2
Click Done at the bottom of the form to start the simulation.
2) Controller output and disturbance variable changes differ in their impact on the measured process variable because the dynamic models defined above are different. Verify this by stepping the controller output from its default value of 50% up to 60% and when the response is substantially complete, step it back to 50%. Next, step the disturbance variable from its default value of 50% up to 60% and when the response is substantially complete, step it back to 50%.
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Hands-on Workshop Series by Douglas J. Cooper Copyright 2005 by Control Station, Inc.
All Rights Reserved
Workshop 4: Tuning PI Controllers by Trial and Error (cont.)
Compare the two responses side by side (you may need to use the Change Strip Chart History icon on the toolbar to see both responses). Does a step in the disturbance variable show a larger but slightly slower response associated with a larger gain and longer overall time constant?
3) Click the Controller icon on the graphic and select PID from the controller design menu. Specify a very conservative (sluggish) PI controller by entering the tuning values:
Set Point Controller Gain Reset Time
= 50 = 1.0 = 50
Be sure the Integral Action is On, and to ensure you are using PI control, set the Derivative Action to Off. Click Done to put the controller in automatic.
4) Trial and error tuning can use up significant production time and create expensive off-spec product. To track how inefficient a trial and error approach can be, zero the simulation clock by clicking on the Clock icon (upper left of screen on tool bar) and then Reset Simulation Clock to Zero. From this point forward, do not reset the clock or pause process execution until instructed to do so.
5) Start tuning for disturbance rejection by considering the current performance of the controller. Click the white Disturbance, D box on the graphic, step the disturbance variable from 50% up to 60% and after the response, step it back to 50%.
Now try and improve controller performance by adjusting KC and/or I on the controller design menu. The PI controller tuning map in Chapter 8 of the Practical Process Control book is for set point tracking but may assist your thought process as you search for your best tuning values. Test your new values by again stepping the disturbance from 50% up to 60% and back again. Repeat this procedure as necessary to arrive at best tuning values for disturbance rejection. Use your own experience and opinion to define best.
When you have determined best tuning values for disturbance rejection, pause the simulation and record them below. Also record the elapsed time displayed on the process clock at the lower left of the screen.
KC = I = Elapsed Time = minutes
(optional)
6) Repeat the above exercise with the objective of controller tuning for set point tracking. Start with your best disturbance rejection tuning values above and determine by trial and error whether they are best when the control objective is tracking set point steps from 50% up to 60% and back again. Record your results:
KC = I = Elapsed Time = minutes Is your best tuning for set point tracking the same as your best tuning for disturbance rejection?