Linear Control Systems LABORATORY

Transcription

1 Islamic University Of Gaza Faculty of Engineering Electrical Engineering Department Linear Control Systems LABORATORY Prepared By: Eng. Adham Maher Abu Shamla Under Supervision: Dr. Basil Hamed

2 Experiments #2 Introduction To LabView Objectives: In this lab we would have an introduction to LabView, especially the basic component you will use during this laboratory. 1) Introduction: LabView is a graphical programming language that uses icons instead of lines of text to create applications. In contrast to text-based programming languages, where instructions determine program execution, LabView uses dataflow programming, where the flow of data determines execution. In LabView, you build a user interface with a set of tools and objects (Control & indicator), the user interface is known as the front panel. You then add code using graphical representations of functions to control the front panel objects. The block diagram contains this code, in some ways, the block diagram resembles a flowchart. LabView empowers you to build your own solutions for scientific and engineering systems. LabView gives you the flexibility and performance of a powerful programming language without the associated difficulty and complexity. LabView gives thousands of successful users a faster way to program instrumentation, data acquisition, and control systems. LabView contains a comprehensive set of tools for acquiring, analyzing, displaying, and storing data, as well as tools to help you troubleshoot your code. Page 1 of 12

3 2) Virtual Instruments (VIs): LabView programs are called virtual instruments, or VIs, because their appearance and operation imitate physical instruments, such as Oscilloscopes and Multi-meters. Every VI uses functions that manipulate input from the user interface or other sources and display that information or move it to other files or other computers. A VI contains the following three components: - Front panel: Serves as the user interface. - Block diagram: Contains the graphical source code that defines the functionality of the VI. - Icon and connector pane: Identifies the VI so that you can use the VI in another VI, a VI within another VI is called a sub-vi. A sub-vi corresponds to a subroutine in text-based programming languages. 2.1) Front Panel: The front panel is the user interface of the VI, you build the front panel with controls and indicators, which are the interactive input and output terminals of the VI, respectively. Controls are knobs, pushbuttons, dials, and other input devices. Indicators are graphs, LEDs, and other displays. Controls simulate instrument input devices and supply data to the block diagram of the VI, Indicators simulate instrument output devices and display data the block diagram acquires or generates. Page 2 of 12

4 2.2) Block Diagram: After you build the front panel, you add code using graphical representations of functions to control the front panel objects. The block diagram contains this graphical source code, and front panel objects appear as terminals on the block diagram. Additionally, the block diagram contains functions and structures from built-in LabView VI libraries. Wires connect each of the nodes on the block diagram, including control and indicator terminals, functions, and structures. 2.3) Icon and connector pane: A connector pane defines VI inputs (controls) and outputs (indicators). One can change the number of inputs and outputs by using different connector pane patterns. A VI icon is shown at the top right corner of the front panel. Page 3 of 12

5 The main different between Express VIs, VIs and Functions: - Express VIs: interactive VIs with configurable dialog page. - Standard VIs: modularized VIs customized by wiring. - Functions: fundamental operating elements of LabView. Express Function Standard Function 3) Graphical Environment: The LabView palettes give you the options you need to create and edit the front panel and block diagram. 3.1) Tools palette: The Tools palette is available on the front panel and the block diagram. A tool is a special operating mode of the mouse cursor, when you select a tool, the cursor icon changes to the tool icon, we use the tools to operate and modify front panel and block diagram objects. Select view Tools Palette to display the Tools palette. You can place the Tools palette anywhere on the screen. If automatic tool selection is enabled and you move the cursor over objects on the front panel or block diagram, LabView automatically selects the corresponding tool from the Tools palette. Automatic Selection Tool Page 4 of 12

6 Operating Tool Positioning/Resizing Tool Labeling Tool Wiring Tool Shortcut Menu Tool Scrolling Tool Breakpoint Tool Probe Tool Color Copy Tool Coloring Tool 3.2) Control palette: The Controls palette is available only on the front panel, it contains the controls and indicators you use to create the front panel. Select view Controls Palette or right-click the front panel workspace to display the Controls palette, you can place it at anywhere on the screen. 3.3) Function palette: The Functions palette is available only on the block diagram, it contains the VIs and functions you use to build the block diagram. Select view Functions Palette or right-click the block diagram workspace to display the Functions palette. You can place it at anywhere on the screen. Page 5 of 12

7 Status Toolbar: Run Button Continuous Run Button Abort Execution Pause/Continue Button Text Settings Distribute Objects Resize front panel objects Execution Highlighting Button Step Into Button Step Over Button Step Out Button Align Objects Reorder 4) Building a Virtual Instrument: In the following exercises, you will build a VI that generates a signal and displays that signal in a graph. 4.1) Opening a New VI from a Template: LabView provides templates containing information from which you can build your VI. These templates help you get started with LabView. Complete the following steps to create a VI that generates a signal and displays it on the front panel. 1. Launch LabView program. 2. In the LabView getting started window, shown in Figure below, click the Blank-VI button to create new VI program. Page 6 of 12

8 A) Adding a Control to the Front Panel: Controls on the front panel simulate the input devices on a physical instrument and supply data to the block diagram of the VI. Many physical instruments have knobs you can turn to change an input value. Complete the following steps to add a knob control to the front panel: a. If the Controls palette, shown in Figure 2, is not visible on the front panel, select view Controls Palette to display it. b. Move the cursor over the icons on the Controls palette to locate the Numeric Controls palette. c. Click the Numeric Controls icon to access the Numeric Controls palette. d. Select the knob control on the Numeric Controls palette and place it on the front panel to the left of the waveform graph. Page 7 of 12

9 B) Changing the Signal Type: The block diagram has a blue icon labeled Simulate Signal. This icon represents the Simulate Signal Express VI. The Simulate Signal Express VI simulates a sine wave by default. Complete the following steps to change this signal to a square wave: a. Display the block diagram by selecting Window Show Block Diagram or by click Ctrl+E. Notice the Simulate Signal Express VI, shown at left. An Express VI is a component of the block diagram that you can configure to perform common measurement tasks. The Simulate Signal Express VI simulates a signal based on the configuration that you specify. b. Right-click the Simulate Signal Express VI and select Properties from the shortcut menu to display the Configure Simulate Signal dialog box or double click on it. c. Select square from the Signal type pull-down menu, the Configure Simulate Signal dialog box shown in the following figure. Page 8 of 12

10 d. Click the OK button to apply the current configuration and close the Configure Simulate Signal dialog box. e. Move the cursor over the down arrows at the bottom of the Simulate Signal Express VI. In the previous figure, notice how Amplitude is an option in the Configure Simulate Signal dialog box. When inputs, such as Amplitude, appear on the block diagram and in the configuration dialog box, you can configure the inputs in either location. C) Wiring Objects on the Block Diagram: To use the knob control to change the amplitude of the signal, you must connect the two objects on the block diagram. D) Modifying the Signal: Complete the following steps to add scaling to the signal and display the results in the graph on the front panel: a. Select the Scaling and Mapping Express VI, shown below, on the Arithmetic & Comparison palette and place it on the block diagram inside the loop between the Simulate Signal Express VI and the Waveform Graph terminal. If there is no room between the Express VI and the terminal, move the Waveform Graph terminal to the right. Notice that the Configure Scaling and Mapping dialog box automatically opens when you place the Express VI on the block diagram. b. Define the value of the scaling factor by entering 3 in the Slope (m) text box, the Configure Scaling and Mapping dialog box should appear similar to below Figure. Page 9 of 12

11 c. Click the OK button to apply the current configuration and close the Configure Scaling and Mapping dialog box. d. Move the cursor over the arrow on the triangle output of the Simulate Signal Express VI. e. When the Wiring tool appears, click the arrow and then click the arrow on the Signals input of the Scaling and Mapping Express VI, shown at left, to wire the two objects together. f. Using the Wiring tool, wire the Scaled Signals output of the Scaling and Mapping Express VI to the Waveform Graph terminal. Notice the wires connecting the Express VIs and terminals. The arrows on the Express VIs and terminals indicate the direction that the data flows along these wires. The block diagram should appear similar to below Figure Page 10 of 12

12 Figure: Block Diagram for the generate and display Signal VI E) Displaying Two Signals on the Graph: To compare the signal generated by the Simulate Signal Express VI and the signal modified by the Scaling and Mapping Express VI on the same graph, use the Merge Signals function. Complete the following steps to display two signals on the same graph: a. Move the cursor over the arrow on the square output of the Simulate Signal Express VI. b. Using the Wiring tool, wire the square output to the Waveform Graph terminal, the Merge Signals function, shown below, appears where the two wires connect this function takes the two separate signals and combines them so that both can be displayed on the same graph. c. Select File Save to save this VI. You also can press the <Ctrl-S> keys to save a VI. d. Return to the front panel, run the VI, and turn the knob control, notice that the graph plots the square wave and the scaled signal. e. Click the STOP button. Page 11 of 12

13 Exercise: 1. Create a new VI that generate cos wave with varying Amplitude and Frequency. (Notice that the Amplitude start from zero). 2. Add toggle switch on the front panel to add or remove noise into the cosine signal with varying amplitude for noise and its type uniform white noise. 3. Add an indicator (Led) to indicate if the amplitude of the noise was exceed the half of amplitude of cosine signal. 4. If the last condition satisfy the program will be display to user text message that tell him An Error Occur, now after the user received this message will click on ok button and the program will be stop. END Page 12 of 12