Introduccion a labview

Introduction to LabVIEW for Control Design & Simulation
Ricardo Dunia (NI), Eric Dean (NI), and Dr. Thomas Edgar (UT) Reference Text : Process Dynamics and Control 2nd edition, by Seborg, Edgar, Mellichamp, Wiley 2004 LabVIEW, which stands for Laboratory Virtual Instrumentation Engineering Workbench, is a graphical computing environment for instrumentation, system design, and signal processing.The Control Design and Simulation (CDSim ) module for LabVIEW can be used to simulate dynamic systems. To facilitate model definition, CDSim adds functions to the LabVIEW environment that resemble those found in SIMULINK. There is also the ability to use m-file syntax directly in LabVIEW through the new MathScript node. The purpose of this tutorial is to introduce you to LabVIEW and give youexperience simulating dynamic systems. .    In the first section, you will build a model of the open-loop system for the second 2e  s order plus time delay process G( s)   and determine the unit set-point and unit (10s  1)(5s  1) disturbance responses. In the second section, you will build a closed-loop model of the same process. After the closed-loop model is constructed, you should simulate theunit disturbance response and the unit set-point response for two different PID controller tuning methods, ITAE (set-point) and ITAE (disturbance), in Table 12.3 (SEM). Log onto a PC computer. Click Start->National Instruments->LabVIEW . Open LabVIEW. (Note : as of LabVIEW 8.6, the Control Design & Simulation module is also supported for Mac )

Start a new program (VI)

Browse example VIsFigure1. Initial LabVIEW Screen

To start a new program ( called VI for Virtual Instrument ), click “Blank VI”

Block Diagram (programming window) Front Panel (user interface)

Figure 2. LabVIEW new VI Click in the block diagram to view the area where graphical programs are written. Right-click inside the block diagram to view the palette of functions used in creating programs. Select theControl Design & Simulation->Simulation palette to view the library of simulation functions.

Figure 3. Simulation functions sub-pallette In Control Design & Simulation pallette

In the next section, you will build a model of the open-loop system for the process mentioned earlier and determine the unit set-point and unit disturbance responses. The following steps will guide you through thediscussed tasks. Construction of an Open-Loop Block Diagram (Chapters 4, 5, 6, and 7) 1. Open a new VI by selecting File->NewVI. The new window will be titled untitled. You will build your closed-loop model in the block diagram. Save the empty model by choosing File>Save . Name the model, examplesim. From this point on, the model will be referred to as examplesim. Click on the block diagram, thenright-click to bring up the functions palette. From the Simulation sub-pallette, click-and-drag a simulation loop on the block diagram.

2.

Click-and-drag to create Simulation loop

3.

Place the Transfer Function and Transport Delay blocks from the “Continuous” pallette, respectively, to Examplesim. Connect the output of the Transfer Function block to the input of the Transport Delay block.Click on the “Transfer Function” label and rename to “Process TF”. This block represents the process. Note that in this problem, the process is G(s) = GvGpGm, not Gp.

Open the dialog box of Process TF by double clicking on it. Specify Numerator as [2] and Denominator as [1 15 50]. This indicates the transfer function 2/(50s2 + 15s + 1). The Transfer Function block allows specification ofvectors for the numerator and denominator from either a configuration dialog box, or a terminal from the block diagram. The vector elements are treated as the coefficients of ascending powers of s in the polynomials representing the numerator and denominator of the transfer function. To see the denominator polynomial of s completely displayed in the block’s icon, you may have to resize the block’s...