user guide 35

Control Station User Guide Copyright 2002 by Douglas J. Cooper

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Doug Cooper

User GuideControl Station 3.5 for Windows

ControlStationSoftware For Process ControlAnalysis, Tuning & Training

ControlStationSoftware For Process ControlAnalysis, Tuning & Training

ControlStationControlStationSoftware For Process ControlAnalysis, Tuning & Training


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1. Installing Control Station

Install on Individual Computer Running Windows: 1. Quit all running applications 2. Insert the Control Station CD-ROM 3. If the install does not start sutomatically, click Window’s Start button (lower left of screen) and choose Run 4. A Run box will open. Click Browse; choose your CD-ROM drive then select SETUP.EXE 5. With SETUP.EXE showing as your Run selection, click OK 6. Follow the directions of the Control Station setup utility If You Have Install Problems Send a detailed message including the specific error message to: [email protected] Network Installation The setup program is a standard MSI install application and is compatible with windows based networks. Manual installation may be required for other networks. For manual installation, some of the Control Station files belong on the central network server while the rest belong in the C:\Windows\System subdirectory of each computer on the network. The latest information is available in Readme.txt on the CD-ROM

The files we provide that go into the C:\Windows\System or C:\Windows\System32 directory may already exist on your computer. Only overwrite your existing files if our versions are newer.

These files are provided by Microsoft and are backward compatible with existing applications. We did not create or modify them in any way.

• Files that can be installed in the main server application directory:

csdmc.dll, brwst.htm, cstation.url, cshelp3.hlp, csmimo.dll, csrecord.dll, csrigdis.dll, cstation.exe, cstools.dll, keycode.003, readme.txt • Files that go in the C:\Windows\System or C:\Windows\System32 directory of each computer on the network.

Asycfilt.dll Comcat.dll Comdlg32.ocx Ctl3d32.dll Dao2535.tlb Dao350.dll Mfc40.dll Mfc42.dll

Mfcans32.dll Msflxgrd.ocx Msimg32.dll Msjet35.dll Msjint35.dll Msjter35.dll Msrd2x35.dll Msrepl35.dll

Msvbvm60.dll Msvcrt.dll Msvcrt20.dll Msvcrt40.dll Msxbse35.dll Oc30.dll Oleaut32.dll Olepro32.dll

Pego32a.ocx Pegrp32a.dll Pepco32a.ocx Pepso32a.ocx Pesgo32a.ocx Slider.ocx Spin32.ocx Stdole2.tlb

Tabctl32.ocx Threed20.ocx Threed32.ocx Vb5db.dll Vbajet32.dll Vbar332.dll


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Installing From a Web Download As long as your license is current, you can update and install Control Station from a web download. Visit: http://www.controlstation.com/update.html and follow the instructions to download and install the software.

About Keycode.003 Your CD-ROM contains a file called Keycode.003. This file must be located in the same directory as Cstation.exe for the software to operate correctly. Do not edit or change this file in any way or your software may not run properly. You will know you have problems related to this file if you see “Keycode Failure – License Invalid” displayed on the main screen of Control Station. If a ”Keycode Failure” occurs, please copy the original Keycode.003 file from your Control Station CD-ROM to the same directory as file Cstation.exe on your hard drive. If problems still persist, send a detailed message to: [email protected] 2. License Agreement All users of the Control Station software program are bound by the agreement written below. By installing the software, you accept all terms and conditions of this agreement.

1. Douglas J. Cooper and Control Station Technologies grant the LICENSEE a nonexclusive and nontransferable license to use the Control Station software program. 2. The LICENSEE acknowledges that the Control Station software program is a tool still in development and that it is being supplied "as is." 3. Douglas J. Cooper and Control Station Technologies make no representations or warranties, expressed or implied. By way of example, but not limitation, Douglas J. Cooper and Control Station Technologies make no representations or warranties of merchantability or fitness of the Control Station software program for any particular use or purpose. Douglas J. Cooper and Control Station Technologies shall not be held liable or assume liability for any direct, indirect or consequential damages with respect to any claim by LICENSEE or any third party on account of or arising from this Agreement or use of the Control Station software program. 4. The LICENSEE agrees not to modify, decompile, decode, reverse engineer or otherwise discover the information, methods and technologies contained in the Control Station software program and/or file Keycode.003. 5. Title to copyright to the Control Station software program and to any material associated therewith shall at all times remain with Douglas J. Cooper and LICENSEE agrees to preserve same. 6. If any part of this agreement is found to be void and unenforceable according to its terms, it will not affect the validity of the balance of the agreement, which shall remain valid and enforceable according to its terms.


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3. About Control Station Control Station is software used by academic and industrial practitioners world-wide for: - hands-on process control training - control system simulation - loop analysis and tuning - performance and capability studies Control Station is a point-and-click environment compatible with Windows 95, 98, Me, NT, 2000 and most computer networks. This powerful software package is visually appealing, easy-to use and popular with students and practitioners alike. Control Station is divided into three modules: Case Studies, Custom Process and Design Tools. The Case Studies module provides real-world experience in modern methods and practices of process control. The Case Studies available for study include level control of a tank, temperature control of a heat exchanger, concentration control of a reactor and purity control of a distillation column. The basic controllers available include P-Only, PI, PD and PID controllers. Advanced strategies include cascade, feed forward, multivariable decoupling, model predictive (Smith predictor), dynamic matrix control, and discrete sampled data control. The Custom Process module is a block oriented environment that lets you construct a process and controller architecture to your own specifications for a wide range of custom control analyses. You can investigate the benefits and drawbacks of different control architectures, tunings sensitivities, loop performance capabilities, and a host of other issues important to the practitioner. The Design Tools module is used to fit linear dynamic models to process data and to compute PID controller tuning values. The models from Design Tools can also be used to construct advanced control strategies which use process models internal to the controller architecture. Because the data can be imported from real operating processes, Design Tools can solve your challenging problems for controller design, analysis and tuning. The Control Station Modules

The Case Studies module has been developed specifically for training in the modern methods and practices of automatic process control. Case Studies accomplishes this by giving you hands-on experience through a collection of interesting and industrially relevant control simulations. Thus, you "learn by doing" as you tackle each real-world challenge. The process simulations,

animated in color-graphic display, are easy to use and visually appealing. The list of simulations available for exploration and study include: Gravity drained tanks Pumped tank Heat exchanger Jacketed stirred reactor Furnace Multi-tank process Distillation column


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For each process, you can manipulate process variables in open loop to obtain step, pulse, sinusoidal, ramped or PRBS (pseudo-random binary sequence) test data. Process data can be recorded as printer plots or disk files for process modeling and controller tuning studies. The Design Tools module discussed later is well-suited for this modeling and tuning task. The controllers available to the Case Studies and Custom Process modules enable the exploration and study of increasingly challenging concepts in an orderly fashion. Early concepts include studying basic dynamic behaviors such as process gain, time constant and dead time. Intermediate concepts include the tuning and performance capabilities of the complete range of PID controllers. Advanced concepts include a number of advanced conventional and model based algorithms including: P-Only, PI, PD and PID PID Cascade Control Feed Forward Control with PID Feedback Trim Multivariable Decoupling Control Model Predictive Control (Smith Predictor, DMC) Discrete Sampled Data Control

The Custom Process module is a block oriented environment that enables you to implement a process and controller architecture to your own specification. The simulations enable a wide range of custom control investigations for single loop and multiloop processes. Transfer function models are entered to describe the controller output to measured process

variable dynamics, the disturbance to measured process variable dynamics of a selected process disturbance, and for multiloop simulations, to describe the control loop interaction behavior. The transfer function models can be linear or nonlinear and overdamped or underdamped in form. Such custom processes permit a host of process dynamics and control studies. For example, you can explore which model form best describes the behavior of your plant; investigate different controller architectures, tuning values and control modes in "what if" scenarios; study how plant-model mismatch impacts closed loop performance in model based architectures; isolate and explore the impact of noise in the measured variable on closed loop performance; and a host of other simulation and control analyses. All you need to do is enter the appropriate process models for your application. The models are entered with user friendly dialog boxes. Design Tools is well-suited for fitting models to process data from your plant or lab to create a custom process simulation.

The Design Tools module offers tools for controller design and analysis. One tool automatically fits dynamic models to process data. Design Tools can import data from Control Station's Case Studies and Custom Process module, data from other software packages, and perhaps most important, data from real processes in the lab or plant.

To fit models to data, Design Tools requires that the data be columns of text (ASCII) with entries of each column separated by tabs, commas or spaces. Every line in a column must have a number; there can be no blank entries. Then, with just a few clicks of the mouse, you mark which data column


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contains the manipulated variable data, which contains the measured process variable data, and which contains the time stamp data. The linear models available in the Design Tools model library include: First Order Plus Dead Time Second Order Plus Dead Time Overdamped Second Order Plus Dead Time Overdamped with Lead Time

First Order Plus Dead Time Integrator Second Order Plus Dead Time Integrator

Second Order Plus Dead Time Underdamped Design Tools fits a model to data by systematically searching for the model parameters that minimize the sum of squared errors (SSE) between the response contained in the measured data and the response predicted by the model when using the actual manipulated variable process data contained in the file. For you to obtain a meaningful fit, it is essential to recognize these limitations: Requirements for a Successful Model Fit

• the process must be at steady state before collection of dynamic data begins, • the first data point in the file must equal this initial steady state value. If these conditions are not met, the model fit will be incorrect and of little value for tuning, model based controller designs or simulation studies. In modern control installations, the dynamic models fit by Design Tools can be used directly in advanced controller architectures ranging from a simple Smith predictor up through the full model predictive control (MPC) algorithms. Design Tools can also be used to design feed forward elements. For feed forward designs, it is the disturbance variable which should be stepped, pulsed or otherwise perturbed. This disturbance data then becomes the manipulated variable when regressing the disturbance-to-measured process variable dynamic model. The second feature of Design Tools is the controller tuning tool. Using the results of a successful model FOPDT fit, tuning values for P-Only, PI and PID controllers are computed. The library of popular tuning correlations include internal model control (IMC) and integral of time-weighted absolute error (ITAE).


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4. Quick Start – Case Studies & Design Tools The next two chapters provide a guided tour of Control Station and many of its features. If you work through these chapters, you will be skilled at the software basics. Don’t be afraid to click your mouse and see what happens. That is the only way you can become a true Control Station power user. To begin, launch Control Station from Windows and the main screen shown below should appear. In this chapter we focus on the gravity drained tanks case study. Follow the instructions below to start the gravity drained tanks process.

To start the gravity drained tanks case study: - Click on Modules on the menu list, then Case Studies, and then Gravity Drained Tanks or..... - Click the Case Studies icon, and then Gravity Drained Tanks or..... - Use right mouse button, then Case Studies, and then Gravity Drained Tanks

Once the simulation has begun, note that the screen is comprised of a process graphic, moving strip charts, a menu list and a tool bar. The upper strip chart tracks the measured process variable, which for the gravity drained tanks is the liquid level in the lower tank. The lower strip chart tracks the controller output, which in this case manipulates the inlet flow rate feeding the top tank. Move the mouse arrow across the icons on the tool bar and read the different functions. There are icons for handling the simulation clock functions, re-sizing the strip charts, viewing and printing plots, saving and editing process data, stopping and starting the simulation, navigating to other Control Station modules, and obtaining access to the Control Guru Help program. The process graphic also has features that can be activated with a mouse click. These include items that have a button appearance or include a white input box. The gravity drained tanks graphic on the next page shows white input boxes for the controller output and pumped flow disturbance, and a level controller button (the circle with the LC in it attached to the lower tank). Most everything you need to do can be accessed two or three different ways: 1) with a click on an icon or white area on the graphic, or 2) from the menu list, or 3) by using the right mouse button. Try all three and determine the method most comfortable for you.


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To start and stop saving data to file: - Click File on the menu list, and then Save Data to File or..... - Click the Save Data icon on the tool bar Once data saving has begun: -The Save Data icon on the tool bar is replaced by a Stop Saving Data icon

The first step in designing a controller is generating and collecting dynamic data. Shown above are two ways to begin saving process data to file. The same commands used to start saving data are also used to stop data collection after the experiment is completed. Go ahead and start saving data to a file called “demo.dat.” Use the default Storage Rate and Zero Clock options when prompted.

To change a variable such as controller output: - Click on Tasks on the menu list, and then Change Controller Output or..... - Click or double click the white input box on the process graphic or..... - Use the right mouse button, and choose Change Controller Output

Once data collection has begun (note the file name in the lower right of the screen above), change the controller output to force process dynamics. Use any of the three methods mentioned above to change the controller output value from 70% up to 75%, then down to 65%, and finally back to 70%. Click the Stop Saving Data icon when the experiment is complete.


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To fit a model to data and to tune a controller, you must Navigate to Design Tools: - Click File on the menu list, and then Navigate, and then Design Tools or..... - Click the Navigate icon on the tool bar, and choose Design Tools To pause the simulation before navigating to Design Tools: - Click the Pause icon on the tool bar

With dynamic process data stored in file “demo.dat,” the next steps in controller design are to fit a FOPDT (first order plus dead time) model to the data and then use the model parameters in a correlation to compute initial controller tuning values.

As shown above, navigate to Design Tools to perform this modeling and tuning task. To help the model fitting proceed quickly, you may want to first Pause the simulation (click the Pause icon on the tool bar, or click Run and choose Pause from the menu list).

When you gain more experience, you may choose to perform several process experiments and collect the results in different files before navigating to Design Tools.

To read a file of process data into Design Tools: - Click File on the menu list, and choose Open Data File or..... - Click the Open Data File icon on the tool bar

The Design Tools main screen, shown above, can be launched from a Case Study or Custom Process simulation using Navigate. By navigating to Design Tools directly from Case Studies or Custom Process, the state of the process simulation remains unchanged during the modeling and tuning task.


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Before fitting a model, the Time, Manipulated Variable and Process Variable data columns must be labeled To do this click on one of the labels, drag it to the proper column and release the mouse key The data in the file can also be viewed and edited from this screen using the Edit Data button After opening a file, the data is

presented for labeling as shown above. Three columns of data must be labeled for a proper fit. Click on a column label and drag and drop it at the top of the proper column. (Note: the manipulated variable is typically the controller output data, but may, for example, be the disturbance variable data if a feed forward element is being constructed).

Design Tools can also be run in a stand-alone mode from Control Station’s main screen. The stand-alone mode of Design Tools is useful when modeling data generated by a process in the lab or plant, or even by another computer program. The data columns can be processed in any order – they need not be presented in the order as shown below. If you are creating a data file outside of Control Station, the file must be in text (ASCII) format and include at least three columns of data. Entries for each column should be separated by tabs, commas or spaces. Every line in a column must have a number; there can be no blank entries. To obtain a meaningful fit, it is essential to recognize that:

• the process must be at steady state before data collection begins, • the first data point in the file must equal this initial steady state value. If these conditions are not met, the model fit will not describe the dynamics of the process and thus of little value for tuning, model based controller designs or simulation studies. For simple PID controller designs from Control Station’s Case Studies and Custom Process data files, the columns are already properly labeled as shown above. Thus, simply click the OK button to proceed to the model fit options. For advanced Case Studies designs, including cascade, feed forward or multivariable architectures, care must be taken to properly label the columns of data. If the data file being processed was created by Control Station, you can verify the proper data column labels by editing the data file using the Edit Data button and reading the information contained at the top of the file.


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To choose a dynamic model from the library: - Click Tasks on the menu list, and then Select Model, and choose a model from the model library or..... - Click the Select Model icon on the tool bar, and choose a model from the model library

With the data columns properly labeled, choose the FOPDT model from the library of linear dynamic models. For convenience, the Laplace and time domain forms of each model are displayed at the bottom of the screen.

To start model fitting: - Click Tasks on the menu list, and choose Start Fitting or..... - Click the Start Fitting icon on the tool bar

Begin fitting the chosen model by clicking the Start Fitting icon on the tool bar. A counter will display the sum of squared errors (SSE), which should decrease if the fit is proceeding properly. If it is not, you may stop the routine by clicking the Stop Fitting icon (which replaces the Start Fitting icon during the fitting operation).


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If the model fit is successful, a plot will be displayed Your judgment is required to determine the goodness of this fit For a good fit, the model (in yellow) should overlay the process data (in white) A poor fit is of little value for modeling and tuning tasks

If a model converges, a plot will display showing the model fit (in yellow) overlaying the process data (in white).

Note: The model fit should reasonably approximate the actual process data (the yellow model fit line should substantially overlay the data). Sometimes a fit may look good but the model parameters make no sense, such as if the computed time constant is longer than the total time span used in the experiment for data collection. If the fit is not reasonable, the model and tuning values are of little value for process control. Your judgment is required to assess and approve a model fit.

There are many options available on this screen to make the plot of more value to you. You may:

- print the plot with the Print icon on the tool bar, or Copy and Export the plot to a clipboard for pasting into Word, Power Point or other program with a graphical cut and paste capability,

- enter different values for the model parameters in the white boxes at the top of the plot screen, press enter, and see how the model fit changes,

- change plot labels, titles, grid displays, max/minimum axis values, tick mark frequency, and more by clicking the Plot Options icon on the tool bar, or clicking Customize and then Plot Options on the menu list,

- zoom for close up views of portions of the plot by holding down the left mouse key and drawing a box around the data of interest (the mouse arrow must be within the plot borders),

- use the X-Y pointer display in the upper corner of the plot to easily read the plot values pointed to by the mouse arrow (the mouse arrow must be within the plot borders).

After customizing the plot to your needs and exporting it if desired, return to the Design Tools main screen by closing the window, or by clicking File and then Exit.


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To obtain controller tuning values: - Click the tabs on the Controller Tuning chart to view P-Only, PI or PID controller tuning values To exit Design Tools and return to the gravity drained tanks: - Close the window or..... - Click File on the menu list, and choose Exit

As shown above, the Design Tools main screen now displays values for the model parameters in a chart to the left and controller tuning values in a chart to the right. Both standard and conservative tuning values are available for P-Only, PI, PID and PID w/ Filter controllers. From your chart, write down the standard PI tuning values KC and τI displayed touse when implementing your controller.

Note: The units for model time constants and dead time, and controller reset time and derivative time are in the units of the time stamp used when saving data to file. For Case Studies, this time unit is minutes. If you save data from the plant or lab, you must be aware of the time units you used as well as that required by your controller.

When you have recorded the PI tuning parameters, exit Design Tools be clicking on File on the menu list and then choosing Exit, or by closing the window.

To open the controller menu: - Click Tasks on the menu list, and then Change Controller/Tuning or..... - Click the controller icon on the process graphic or..... - Use a right mouse click, and then Change Controller/Tuning


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Choose one of the above methods to open the Controller Design Menu. You will notice a question mark button as shown below. Click on these buttons, located throughout Control Station, to access Control Guru Help and learn about theory and technology issues associated with a selection.

To access Control Guru and learn more about theory and technology issues for a selection: - Click a question mark ? anywhere it is displayed

To implement a controller, click Manual Mode at the top of the design menu and choose PID from the list. Halfway down the menu, enter the PI controller tuning KC and τI you just computed in Design Tools (or enter the numbers shown in this example). Click Done at the bottom of the controller menu to put your controller in automatic.

To change set point: - Click Tasks on the menu list, and then Change Set Point or..... - Click the white Set Point box on the process graphic To view or print a fixed plot: - Click File on the menu list, and choose View and Print Plot or..... - Click the Plot icon on the tool bar

Test your controller in tracking changes in set point. On the process graphic as shown above, click once on the white Set Point box, enter 5.0, and press enter. This should cause a response similar to that shown in the figure. Explore controller performance in rejecting disturbances by entering a new pumped flow rate in the white Disturbance box on the graphic and pressing enter. Click View and Print plot to obtain a fixed plot of your graph. There you can modify the plot display and print a copy as described at the bottom of Page 11.


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5. Quick Start – Custom Process Custom Process operates like Case Studies in every way except that you define the dynamic behavior of the simulation by entering a model. The models are entered as parameters of a transfer function using convenient menus. To review popular model forms, click through the model library in Design Tools. There, models are displayed as transfer functions in the Laplace domain and as (possibly more familiar) ordinary differential equations in the time domain. To start Custom Process from Control Station’s main menu: - click Modules on the menu list and then choose Custom Process, or - click the Custom Process icon, or - click the right mouse button and then choose Custom Process. You are then presented with a choice of running the Single Loop Process or Multi-Loop Process. Single Loop Process If you choose Single Loop Process, Custom Process launches as shown below. The left half of the screen shows the familiar menu list, tool bar and moving strip charts. The upper strip chart tracks the measured process variable while the lower strip chart tracks the controller output signal.

The right half of the screen shows the dynamic models used in the simulation expressed in the Laplace domain. Next to the models is a controller deviation bar display showing the current values of the controller output (CO), measured process variable (PV) and set point (SP). Below them is a process block diagram graphic.

To import a model previously constructed and saved to disk: - Click File on the menu list, and then Import Model Parameters from File or..... - Click the Import button below the process block diagram graphic

For a custom study, you must specify the controller output to measured process variable dynamic behavior with a process model. You may choose to specify one disturbance to measured variable dynamic behavior with a disturbance model (this model need be defined only if you are performing disturbance dynamics investigations or disturbance rejection control studies).

You can import a model previously constructed and saved to disk. As shown above, either click File on the menu list and choose Import Model Parameters from File, or click the Import icon below the process block diagram graphic. You may save a model to disk after creating or modifying it. Either click File on the menu list and then click Export Model Parameters to File, or click the Export icon below the process block diagram graphic.


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To construct a process model: - Click Tasks on the menu list, and then Construct Process Model or..... - Click the Process icon on the process block diagram graphic

As shown above, to construct a custom simulation, click Tasks on the menu list and then click Construct Process Model, or click the Process icon on the process block diagram graphic. This opens the Construct Process and Disturbance Model menu shown below. For both process and disturbance, the model forms available include: - Overdamped Linear Model - Overdamped Nonlinear Schedule Model - Underdamped Linear Model - Underdamped Nonlinear Schedule Model Use the tabs to select the Process Model or Disturbance Model. For the Overdamped Linear Model, enter your parameters using the input boxes as shown.

Click the appropriate tab to select the Process Model or Disturbance Model input form Enter the model parameters in the input boxes provided Click the Preview New Process Model icon to view your model

Tabs permit you to see your model both in the time domain and Laplace domain. You may also change the accuracy of the numerical solution method. The more accurate methods are slower as they


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use more computing resources. High accuracy is valuable when solving text book problems but of uncertain value whne solving problems in the highly uncertain real world. The input form for the nonlinear schedule model is shown below. The nonlinear schedule requires that you enter three linear models at each of three operating levels, or process variable basis values.

Click the model list to change model form The nonlinear model schedule requires entry of three linear models, each for a different operating level or process variable basis value

The nonlinear simulation method exploits the fact that: - a linear model can accurately describe the behavior of a nonlinear process for a narrow range of

operation, and - nonlinear behavior can be simulated by averaging the dynamics of multiple linear models. During simulation, Control Station identifies the two linear models whose basis values bracket the current value of the measured process variable. The dynamic behavior of these two linear models are then interpolated to simulate the nonlinear behavior of the process. As would be expected, the closer the measured process variable is to a particular basis value, the more weight that linear model is given in the interpolation. If the current measured process variable is outside the bounds of the basis values, the dynamics of the two closest models are extrapolated. After entering your model parameters, click Done to start the simulation. The measured process variable, controller output and disturbance variable will all start up at 50 and will be limited in range to between 0 and 100 throughout the simulation. These are the default zero and span values. If you are interested in zeros and spans for a specific process, then these default values are inappropriate. The Zeros and Spans tab permits custom values to be entered. The form on the next page shows the maximum, minimum and start up values for a process where the initial or startup value of the measured process variable is 16.4, the initial or startup value of the controller output signal is 70, the startup value of the disturbance variable is 47, and all variables can assume a minimum value of 0 and a maximum value of 100. After entering appropriate values, click Done at the bottom of the form to start the simulation.


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Click the Zeros and Spans tab to enter custom min, max and initial startup values Click Done at the bottom of the form to start the simulation

Once the simulation has begun, all features discussed for Case Studies, including Design Tools, the controller library, and the graphing and printing utilities, are available as needed. For example, to implement a controller, click Tasks on the menu list and then choose Change Controller/Tuning, or click on the controller icon on the graphic, or use a right mouse click and then choose Change Controller/Tuning. As shown below, the controller design menu is identical to that used in the Case Studies processes.

To implement a controller: - Click on Tasks on the menu list and choose Change Controller/Tuning or..... - Click on the controller icon on the graphic or..... - Use a right mouse click and choose Change Controller/Tuning


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Multi-Loop Process If you choose Multi-Loop Process, Custom Process launches as shown below. The left half of the screen lists the six models that define a multi-loop simulation. Next to the model list are deviation bar displays for the two control loops. The right side of the screen shows a block diagram graphic of the multivariable custom process and the pathways that information travels among the models. A complete multi-loop simulation is comprised of six models - models for process 1 (CO1 to PV1) and process 2 (CO2 to PV2) - two interaction models (CO1 to PV2) and (CO2 to PV1) - two disturbance models (D1 to PV1) and (D2 to PV2) While it is only necessary to define the disturbance models if they are being used in the study, the process and interaction models must be entered to create a meaningful multivariable investigation.

To import a model previously saved to disk:

- Click File on the menu list, and choose Import Model Parameters from File

or.....

- Click the Import button below the deviation bars

To toggle between the two multi-loop display screens:

- Click Task on the menu list, choose Toggle

or.....

- Click the Toggle icon on the tool bar

Like the single loop custom process, you may import a previously saved multi-loop process simulation by clicking File on the menu list and choosing Import Model Parameters from File, or clicking the Import button located beneath the deviation bar displays. Saving a simulation you have created is achieved with the analogous Export selection. The multi-loop custom process actually has two displays. The edge of the second screen can just be seen in the figure above. To toggle to the other screen, click Task on the menu list and then click Toggle, click the Toggle icon on the tool bar, or click the edge of the screen currently in back. The back display is shown on the next page. The left half of the screen shows a menu list, a tool bar and four moving strip charts. The upper two strip chart track CO1 and PV1 and the lower strip charts track CO2 and PV2. The right side of the screen shows the same block diagram graphic of the multivariable custom process.


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To construct a model: - Click Tasks on the menu list, choose the model block of interest, and then Construct Model or..... - Click the appropriate model block icon on the block diagram graphic

Construction of a multi-loop simulation follows the procedure detailed for the single loop custom process. To input a model for a particular block, click Tasks on the menu list, choose the model block of interest and choose Construct Model, or click the appropriate model block icon on the block diagram graphic as shown above. This opens the Construct Process and Disturbance Model menu shown below.

Click the appropriate tab to call up a model input form Click the Model List below the Process tab to select the desired model form Enter the model parameters in the input boxes provided Use the Zeros and Spans tab to enter those values. Click Done to start the simulation

Choose the desired model form and enter the model values into the input boxes. Specify the zeros and spans using that tab. Click Done to start the simulation. Once the simulation has begun, all features previously discussed, including Design Tools, the controller library, and the graphing and printing utilities, are available as needed.

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