Department of Electronics and Communication Engineering
#LabVIEW: Introduction Features of LabVIEW Getting started with LabVIEW
# PCI- 6014 DAQ Card # Lab Experiments: 1.
Digital Storage Oscilloscope
2.
PID Controller
3.
Robotic Arm
4.
Lissajious Pattern
5.
Implementation of Boolean Expression
Introduction: LabVIEW (Laboratory Virtual Instrumentation Engineering Workbench) is a platform and development environment for a visual programming language. The graphical language is named ‘G’. LabVIEW is commonly used for simulation, data acquisition, instrument control, measurement analysis, and data presentation. The programming language used in LabVIEW, called "G", is a dataflow language. Execution is determined by the structure of a graphical block diagram (the LV-source code) on which the programmer connects different function-nodes by drawing wires. These wires propagate variables and any node can execute as soon as all its input data become available. Since this might be the case for multiple nodes simultaneously, G is inherently capable of parallel execution LabVIEW ties the creation of user interfaces (called front panels) into the development cycle. LabVIEW programs/subroutines are called virtual instruments (VIs) because their appearance & operation imitate as physical instruments. Each VI has three components: a block diagram, a front panel and a connector pane. The latter may represent the VI as a subVI in block diagrams of calling VIs. Controls and indicators on the front panel allow an operator to input data into or extract data from a running virtual instrument. However, the front panel can also serve as a programmatic interface. Thus a virtual instrument can either be run as a program, with the front panel serving as a user interface, or, when dropped as a node onto the block diagram, the front panel defines the inputs and outputs for the given node through the connector pane. This implies each VI can be easily tested before being embedded as a subroutine into a larger program. Features of LabVIEW: The graphical approach also allows non-programmers to build programs by simply dragging and dropping virtual representations of the lab equipment with which they are already familiar. The LabVIEW programming environment, with the included examples and the documentation, makes it simpler to create small applications. Programmers with a background in conventional programming often show a certain reluctance to adopt the LabVIEW dataflow scheme, claiming that LabVIEW is prone to race conditions. In reality, this stems from a misunderstanding of the data-flow paradigm. The aforementioned data-flow
(which can be "forced", typically by linking inputs and outputs of nodes) completely defines the execution sequence, and that can be fully controlled by the programmer. Thus, the execution sequence of the LabVIEW graphical syntax is as well-defined as with any textually coded language such as C, Visual BASIC etc. Furthermore, LabVIEW does not require type definition of the variables; the wire type is defined by the data-supplying node. LabVIEW supports Polymorphism in that wires automatically adjust to various types of data. Getting Started with LabVIEW Virtual Instruments: LabVIEW programs are called virtual instruments, or VIs, because their appearance and operation imitate physical instruments, such as oscilloscopes and multimeters. LabVIEW contains a comprehensive set of tools for acquiring, analyzing, displaying, and storing data, as we ll as tools to help you troubleshoot your code. In LabVIEW, you build a user interface, or front panel, with controls and indicators. Controls are knobs, push buttons, dials, and other input devices. Indicators are graphs, LEDs, and other displays. After you build the user interface, you add code using VIs and structures to control the front panel objects. The block diagram contains this code. Use LabVIEW to communicate with hardware such as data acquisition, vision, and motion control devices and GPIB, PXI, VXI, RS232, and RS-485 instruments. Building a Virtual Instrument In the following exercises, you will build a VI that generates a signal and displays that signal in a graph. When you complete the exercises, the front panel of the VI will look similar to the front panel shown in the below figure.
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. 2. In the LabVIEW dialog box, shown in Figure, click the New button to display the New dialog box.
3. Select VI from Template»Tutorial (Getting Started)»Generate and Display in the Create new list. This template VI generates and displays a signal.
Notice that previews of the template VI appear in the Front panel preview and the Block Diagram preview sections. Figure below shows the New dialog box and the Generate and Display template VI.
4. Click the OK button to open the template. You also can double-click the name of the template VI in the Create new list to open the template. 5. Examine the front panel of the VI. The user interface, or front panel, appears with a gray background and includes controls and indicators. The title bar of the front panel indicates that this window is the front panel for the Generate and Display VI. Note If the front panel is not visible, you can display the front panel by selecting Window»Show Front Panel. 6. Examine the block diagram of the VI. The block diagram appears with a white background and includes VIs and structures that control the front panel objects. The title bar of the block diagram indicates that this window is the block diagram for the Generate and Display VI. Note If the block diagram is not visible, you can display the block diagram by selecting Window»Show Block Diagram. 7. In the front panel toolbar, click the Run button, shown at left. Notice that a sine wave appears on the graph. 8. Stop the VI by clicking the STOP button, shown at left, on the front panel.
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. 1. If the Controls palette, shown in Figure below, is not visible on the front panel, select Window»Show Controls Palette or right-click the front panel workspace to display it.
2. Move the cursor over the icons on the Controls palette to locate the Numeric Controls palette. Notice that when you move the cursor over icons on the Controls palette, the name of that subpalette appears in the gray space above all the icons on the palette. When you idle the cursor over any icon on any palette, the full name of the subpalette, control, or indicator appears. 3. Click the Numeric Controls icon to access the Numeric Controls palette. 4. Select the knob control on the Numeric Controls palette and place it on the front panel to the left of the waveform graph. You will use this knob in a later exercise to control the amplitude of a signal. 5. Select File»Save As and save this VI as Acquiring a Signal.vi to an easily accessible location. Controls Palette: The Controls palette is available only on the front panel. The Controls palette contains the controls and indicators you use to create the front panel. The controls and indicators are located on subpalettes based on the types of controls and indicators.
Functions Palette The Functions palette is available only on the block diagram. The Functions palette contains the VIs and functions you use to build the block diagram. The VIs and functions are located on subpalettes based on the types of VIs and functions.Select Window»Show Functions Palette or right-click the block diagram workspace to display the Functions palette. Context Help Window: The Context Help window displays basic information about LabVIEW objects when you move the cursor over each object. Objects with context help information include VIs, functions, constants, structures, palettes, properties, methods, events, and dialog box components. You also can use the Context Help window to determine exactly where to connect wires to a VI or function.
Virtual Instruments: LabVIEW programs are called virtual instruments, or VIs, because their appearance and operation imitate physical instruments, such as oscilloscopes and multimeters. 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 subVI. A subVI corresponds to a subroutine in text-based programming languages.
The VI in Figure shows several primary block diagram objects—terminals, functions, and wires.
Figure: - Example of a Block Diagram and Corresponding Front Panel Terminals The terminals represent the data type of the control or indicator. You can configure front panel controls or indicators to appear as icon or data type terminals on the block diagram. By default, front panel objects appear as icon terminals. For example, a knob icon terminal shown at left represents a knob on the front panel. The DBL at the bottom of the terminal represents a data type of double-precision, floating-point numeric. A DBL terminal, shown at left, represents a double-precision, floating-point numeric control or indicator. Terminals are entry and exit ports that exchange information between the front panel and block diagram. Data you enter into the front panel controls (a and b in Figure) enter the block diagram through the control terminals. The data then enter the Add and Subtract functions. When the Add and Subtract functions complete their internal calculations, they produce new data values. The data flow to the indicator terminals, where they exit the block diagram, reenter the front panel, and appear in front panel indicators (a+b and a-b in Figure).
Nodes: Nodes are objects on the block diagram that have inputs and/or outputs and perform operations when a VI runs. They are analogous to statements, operators, functions, and subroutines in text-based programming languages. The Add and Subtract functions in Figure are nodes. Wires You transfer data among block diagram objects through wires. In Figure, wires connect the control and indicator terminals to the Add and Subtract functions. Each wire has a single data source, but you can wire it to many VIs and functions that read the data. Wires are different colors, styles, and thickness, depending on their data types. A broken wire appears as a dashed black line with a red X in the middle. Structures Structures are graphical representations of the loops and case statements of text-based programming languages. Use structures on the block diagram to repeat blocks of code and to execute code conditionally or in a specific order.
PCI-6014 DAQ CARD:
AIM: Design and testing of LabVIEW for two input channels.
Digital
Storage
Oscilloscope
using
APPARATUS: 1.LabVIEW software 2. DAQ Card 3. Power Supply 4. Function Generator
PROCEDURE: 1.Make the connections as per the connection diagram shown below . 2. Connect the Function Generator output to the PCI- pin slots according to
the diagram given. 3. Create an VI program for Dual Channel Oscilloscope. 4. Run the Program by clicking the => (run) button on the Front Panel. 5. Observe the waveforms displayed on the Front Panel window & store the following parameters DC voltage, AC voltage, amplitude, frequency.
DAQ CARD Pins
SIGNAL M
SIGNAL
CH-1
CH-2
68
+ input
34
- input
67
AI GND
33
+ input
32
- input
66
AI GND
PC DISPLAY
Front Panel of Oscilloscope
Block Diagram of Oscilloscope
AIM: Simulation of PID controller schemes using LabVIEW. APPARATUS: LabVIEW software. THEORY: Introduction: Proportional, Integral, and Derivative controller or PID is a standard feedback loop component in industrial control applications. It measures an "output" of a process and controls an "input", with a goal of maintaining the output at a target value, which is called the "set point". An example of a PID application is the control of a process temperature, although it can be used to control any measurable variable, which can be affected by manipulating some other process variable. The Controller compares a measured value from a process (typically and industrial process) is as follows: The difference (or "error" signal) is then used to calculate a new value for a manipulatable input to the process that brings the process' measured value back to its desired set point. Unlike simpler control algorithm, the PID controller can adjust process outputs based on the history and rate of change of the error signal, which gives more accurate and stable control. (It can be shown mathematically that a PID loop will produce accurate, stable control in cases where a simple proportional control would either have a steady state error or would cause the process to oscillates). PID controllers do not require advanced mathematics to design and can be easily adjusted (or "tuned") to the desired application, unlike more complicated control algorithms based on optimal control theory. PROPORTONAL BAND The control algorithm that generates a linear control output proportional to deviation is called proportional action. In proportional action the amount of change in the measured valve (or deviation) is expressed in percent of span that is required to cause the control output to change from 0 to 100% is called the proportional band. P= Kp [SP-PV] + P0
INTEGRAL TIME With P action the measured valve will not necessarily become equal to the set the point, and a deviation will usually be present. The control algorithm that applies changes in output as long as a deviation exits, so as to bring the deviation to zero, is called integral action. When integral action is used, the parameter that determines how fast the output will change in correspondence to some amount of deviation is referred to as integral time,
and shorter the integral time, stronger the integral action (the greater the output rate of change). I action is usually used together with P action as P1 action, and due only to 1 became equal to that due only to P action. P=1/Ti [SP-PV] + Po
DERIVATIVE TIME: If the controlled object has a large time constant or dead time, with P or PI action alone there will be cases where the response will be slow, overshoot will occur, and the control system will be unstable. In order to achieve faster response and more stable operation cases one uses derivation action (D action) to apply an output component proportional to the input (deviation) rate of change. D action must always be used with P action time required with PD action. If a ramp input (constant rate of change input) is applied, for the output due to P action alone to become equal to that due to D action alone. The longer the derivation time, the stronger the derivation action. P=Td d/dt [SP-PV]+Po
This software is organized to explain all the control action available for the proportional control (P), proportional plus integral control (PI), proportional plus derivative control (PD) and proportional plus integral plus derivative control (P+I+D). Note: Temperature process is generally a very slow process compared to other process. Usually proportional integral and derivative control is preferred for temperature control. a. For ‘P’ Control: For controlling the ‘P’ Value, keep the ‘I’ and ‘D’ value ‘0’ (zero). b. For ‘PI’ Control: For controlling the ‘PI’ value, keep the ‘D’ value as ‘0’ (zero) c. For ‘PID’ control: For controlling the ‘PID’ value, SET all the values.
PROCEDURE: 1.Creat an VI program for PID Controller using LabVIEW. 2. Select the Set point 3.As per requirement set the Kp, Ki & Kd values for controlling. 4.Observe the graph & record the observe data.
Front Panel of PID Controller
Block Diagram of PID Controller.
AIM: Design & develop a Robotic Arm having three degree of freedom For pick and Place operation. SOFTWARE REQUIRED: LabVIEW. PROCEDURE: 1.Open the Robotic . VI program from “LabVIEW Experiments” folder. 2. Run the Program by clicking the => (run) button on the Front Panel. 3. Observe the 3-D movement of arm, claw, joints etc separately and than by combining all.
Fig: Front Panel of Robotic. VI
Fig: Block Diagram of Robotic. VI
