LabVIEW Simulation Interface Toolkit

LABVIEW™ SIMULATION INTERFACE TOOLKIT
The LabVIEW Simulation Interface Toolkit provides two features for using
LabVIEW with the software of The MathWorks, Inc. known as Simulink
and Real-Time Workshop. One feature is the NI Sinks and Source
palette, which you can use to graphically configure “Sinks” and “Sources”
blocks in a simulation model in Simulink. With the second feature, you can
use Real-Time Workshop to build files to run simulation models within the
LabVIEW environment.
Simulink, an add-on toolkit for The MathWorks MATLAB software,
provides a graphical environment for the design and interactive execution
of dynamic system models. You can create models in Simulink using
customizable blocks. Using graphical wires to connect the blocks, you can
specify data flow.
Real-Time Workshop is an add-on package for Simulink that generates
C code from Simulink models. Real-Time Workshop then compiles the
code into dynamic link libraries (DLLs). You can use these DLLs for
simulation or use them on various hardware targets in real-time control
applications.
LabVIEW is a graphical programming language that uses icons instead of
lines of text to create applications. LabVIEW applications often are called
virtual instruments, or VIs, because their appearance and operation often
imitate physical instruments, such as oscilloscopes and multimeters.
The LabVIEW Simulation Interface Toolkit integrates Simulink and
Real-Time Workshop with LabVIEW in a way that allows you to develop
and test control systems first developed in the Simulink simulation
environment. Refer to the LabVIEW Bookshelf for information about
LabVIEW and to access the LabVIEW help resources. Access the
LabVIEW Bookshelf by selecting Start»Programs»National
Instruments»LabVIEW»Search the LabVIEW Bookshelf.
LabVIEW™, National Instruments™, NI™, and ni.com™ are trademarks of National Instruments Corporation. Simulink,
Real-Time Workshop, and MATLAB are registered trademarks of The MathWorks, Inc. Further, product and company
names mentioned herein are trademarks, registered trademarks, or trade names of their respective companies. For
patents covering National Instruments products, refer to the appropriate location: Help»Patents in the software, the
patents.txt file on your CD, or ni.com/patents. You are only permitted to use this product in accordance with
the accompanying license agreement. All rights not expressly granted to you in the license agreement accompanying the
product are reserved to NI. Further, and without limiting the foregoing, no license or any right of any kind (whether by
express license, implied license, the doctrine of exhaustion or otherwise) is granted under any NI patents or other
intellectual property right of NI with respect to any other product(s) of NI or of anyone else (including without limitation,
the Simulink and the Real-Time Workshop products of The MathWorks, Inc.), including without limitation, the right to
use any of these other products.
ni.com
© 2002 National Instruments Corp. All rights reserved.
October 2002
370420A-01
Contents
Installation ...............................................................................................2
Configuring NI Sinks and Sources Blocks in Simulink ..........................2
Using a Model DLL for Simulation in LabVIEW...................................4
Building a Model DLL Using Simulink
and Real-Time Workshop..............................................................4
Understanding the Model DLL ........................................................6
Downloading the Model DLL to a Remote Target ...................6
Exchanging Data with the Model DLL ............................................7
Creating a LabVIEW VI to Call the Model DLL.............................8
Creating a Real-Time Model-Based Control....................................9
Installation
To use the LabVIEW Simulation Interface Toolkit, you must be a properly
licensed user of and have the following software installed on the
development system.
•
The MathWorks MATLAB version 6.0 or later
•
The MathWorks Simulink 4.0 or later
•
The MathWorks Real-Time Workshop 4.0 or later
•
Microsoft Visual C++ 5.0 or later
•
National Instruments LabVIEW 6.1 or later
Complete the following steps to install the LabVIEW Simulation Interface
Toolkit.
1.
Insert the LabVIEW Simulation Interface Toolkit CD.
2.
Run the setup.exe program.
3.
Follow the instructions that appear on the screen.
Configuring NI Sinks and Sources Blocks in Simulink
The blocks located in the NI Sinks and Sources palette in the Simulink
Library Browser provide the Simulink user two types of functionality. The
display-oriented blocks—Scope, XY Graph, and Display—are linked to a
LabVIEW user interface that displays values and signals generated in
Simulink. These blocks use a LabVIEW waveform chart to display the
values and signals. The following figure is an example of the LabVIEW
user interface linked to a Scope block.
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Figure 1. Scope Block
The waveform chart used in this Scope block has the following features:
Use the Scale Lock button, shown at left, to toggle autoscaling for
each scale, the visibility of scales, scale labels, and plots, and to format
scale labels, grids, grid lines, and grid colors.
Use the Autoscale button, shown at left, to automatically adjust the
horizontal and vertical scales to reflect the data you wire to them.
Use the Operating tool to click the Scale Format button, shown at left,
to configure the format, precision, and mapping mode.
Use the Panning tool, shown at left, to pick up the plot and move it
around on the display.
Use the Zoom button, shown at left, to zoom in and out of the display.
Use the Cursor Movement tool, shown at left, to move the cursor on the
graph.
Refer to Chapter 11, Graphs and Charts, of the LabVIEW User Manual for
information about the waveform chart.
The other blocks on the NI Sinks and Sources palette are built-in Simulink
blocks whose parameter dialog boxes are provided by a LabVIEW VI. The
parameters in these blocks are used to set the parameters in the Simulink
built-in blocks.
Refer to the Simulink documentation for information about the blocks.
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LabVIEW Simulation Interface Toolkit
Using a Model DLL for Simulation in LabVIEW
Real-Time Workshop creates a DLL, called a model DLL, based on a
Simulink model. The LabVIEW Simulation Interface Toolkit places a set
of Simulation Interface VIs in the labview\vi.lib\addons\
Simulation Interface folder. These VIs help you call the model DLL
from LabVIEW.
Refer to the LabVIEW Simulation Interface Toolkit Help for information
about the Simulation Interface VIs. Access the LabVIEW Simulation
Interface Toolkit Help by selecting Help»LabVIEW Simulation
Interface Toolkit Help in LabVIEW.
The model DLL contains all aspects of the Simulink model but is independent of the
Simulink model.
Note
Building a Model DLL Using Simulink and Real-Time Workshop
Complete the following steps to build a model DLL that LabVIEW can use
to run a simulation model.
If you are using the LabVIEW Real-Time (RT) Module, select a local system as the
target platform in LabVIEW before building a model DLL. Real-Time Workshop cannot
build a model DLL if you select a remote device.
Note
1.
Open the Simulink model for which you want to build a model DLL.
2.
Select View»Show Library Browser to access the NI Sinks and
Sources library.
3.
Place generic inport and outport blocks from the NI Sinks and
Sources library on the Simulink model. The inport and outport blocks
correspond to the inputs and the outputs of the model DLL.
LabVIEW uses these blocks to send data to and receive data from the
model DLL. Refer to the Exchanging Data with the Model DLL
section for information about sending and receiving data.
If the Simulink model already contains inport and outport blocks, continue to the
next step.
Note
4.
Select Simulation»Simulation Parameters to display the Simulation
Parameters dialog box.
5.
Click the Solver tab. Set the Type option to Fixed-step in the Solver
Options section.
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6.
Click the Real-Time Workshop tab. Enter nidll.tlc in the System
target file box.
You also can click Browse to open the System Target File Browser
dialog box. Select nidll.tlc—LabVIEW DLL Target from the listbox
and click the OK button to continue.
7.
Click the Build button in the Category section to begin building the
model DLL.
The Command Window on the MATLAB desktop displays the status
of the Real-Time Workshop as it builds the model DLL.
8.
Select a target IP address from the Select target IP address (for DLL
download) dialog box that appears.
Note After the LabVIEW Simulation Interface Toolkit builds a model DLL, it places the
model DLL into a project folder on the computer. You have the option of downloading the
new model DLL to a remote target.
Complete one of the following three steps to select a target IP address:
•
Select the IP address from the list of previously used targets in the
Target IP Address pull-down menu. Click the DOWNLOAD
button to continue.
•
Select other remote target from the Target IP Address
pull-down menu to enter a new IP address. Click the
DOWNLOAD button to continue.
•
Click the SKIP DOWNLOAD button if you do not want to
transfer the model DLL to a remote target. Click the SKIP
DOWNLOAD button again to continue.
If you choose not to transfer the model DLL file to the remote target when prompted,
you can use the ftpToTarget library located in the model project folder to transfer the
file later. You also can use FTP to directly transfer the file to the c:\ni-rt\system folder
on the remote target.
Note
The following message in the MATLAB desktop Command Window
indicates that Real-Time Workshop has completed building the
model DLL.
### Successful completion of Real-Time Workshop build
procedure for model: ModelName.
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Understanding the Model DLL
To create a model DLL, Real-Time Workshop converts the Simulink
model and any of its submodels into C code and compiles them into a
model DLL named ModelName.dll, where ModelName is the name of the
Simulink model. Real-Time Workshop then places the model DLL into a
new model project folder, ModelName_nidll_rtw, in the current
working directory of MATLAB.
The name of the model DLL must conform to the 8.3 file naming convention so the
model DLL can run on a remote LabVIEW RT target.
Note
To call a model DLL from LabVIEW, use the Simulation Interface VIs that
LabVIEW Simulation Interface Toolkit provides. The Simulation Interface
VIs, located in the labview\vi.lib\addons\Simulation
Interface folder, allow initialization, finalization, single-step execution,
and manipulation of the internal parameters of the model DLL.
In addition, LabVIEW creates two example VIs and places them in the
model project folder. The first example VI, ModelName_daq_driver.vi,
is a data acquisition (DAQ) application that reads input values from a DAQ
board, sends the values as inputs to the SIT Step Model VI, retrieves the
outputs from the SIT Step Model VI, and writes the outputs to the DAQ
board. The second example VI, ModelName_driver.vi, is a version of
the same VI, with the DAQ calls replaced by controls and indicators.
Refer to the Creating a LabVIEW VI to Call the Model DLL and the
Creating a Real-Time Model-Based Control sections for examples using
the Simulation Interface VIs in a LabVIEW VI. Refer to the LabVIEW
Simulation Interface Toolkit Help for information about the Simulation
Interface VIs.
The model project folder also contains a LabVIEW custom control,
ModelName modelParamEnum.ctl, that is an enumeration of all tunable
parameters of the model DLL. Refer to the example VIs in the model
project folder to see this control used with the SIT Set Model Parameters
VI to modify the model DLL.
Downloading the Model DLL to a Remote Target
Statically linked DLLs are downloaded automatically to an RT execution
target. However, to facilitate simultaneous handling of multiple model
DLLs, the SIT Initialize Model VI loads the model DLL dynamically. Then
the SIT Initialize Model VI sends a 32-bit signed integer reference to the
other Simulation Interface VIs to identify the model DLL.
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Because the model DLL loads dynamically, LabVIEW RT does not
automatically download the model DLL to an RT execution target along
with other LabVIEW VIs. So while building the model DLL, the LabVIEW
Simulation Interface Toolkit prompts you to transfer the model DLL to a
remote target.
Exchanging Data with the Model DLL
After you create a model DLL that LabVIEW can call, you can exchange
data with the model DLL from a LabVIEW VI. Every call to the SIT Step
Model VI takes one time step in the simulation model. To continuously
exchange data with the model DLL, use the Simulation Interface VIs with
a loop structure.
Any LabVIEW VI that you create can exchange data with the simulation
model through the inputs and outputs of the SIT Step Model VI. The data
inputs are values you want to send to the model DLL with each loop
iteration, and the data outputs are values you want to receive from the
model DLL after each loop iteration.
In Simulink, the inputs and outputs correspond to the generic inport and
outport blocks that you added to the block diagram. In LabVIEW, the inputs
and outputs of the model DLL correspond to arrays of double-precision
values transferred to and from the SIT Step Model VI. These inputs and
outputs of the model DLL accept scalar or array data.
When you connect an inport or outport block in Simulink to an array of data, the
elements of that array appear as consecutive elements in the corresponding LabVIEW
array. During the build process, the LabVIEW Simulation Interface Toolkit creates a
portsreadme.txt file in the model project folder. This file describes the mapping
between the LabVIEW arrays and Simulink inport and outport blocks.
Note
You also can exchange data with the model DLL through the inputs and
outputs of the SIT Set Model Parameters. The SIT Set Model Parameters
VI updates the model DLL with data from controls on the front panel.
It also sends data to the indicators on the front panel when the parameters
change.
© 2002 National Instruments Corporation
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LabVIEW Simulation Interface Toolkit
Creating a LabVIEW VI to Call the Model DLL
The example VI, ModelName_driver VI, in the following figure
communicates with the model DLL using a While Loop. Each loop
iteration in the VI corresponds to one time step of the Simulink model.
Figure 2. ModelName_driver VI
The SIT Initialize Model VI at the left of the block diagram prepares the
model DLL for execution, sets the final time for the model DLL, and
returns the following information about the model DLL: the time step,
number of inports, and number of outports.
The SIT Step Model VI takes one time step of the simulation model with
each iteration of the loop, accepting the input array and returning the output
array. SIT Step Model VI also indicates if this is the final time step of the
loop.
The loop terminates either when the user presses the Stop button on the
front panel or after the SIT Step Model VI indicates that the model DLL has
reached its specified stop time. The loop exits and the SIT Finalize Model
VI executes.
ModelName_driver VI uses the Simulation Interface VIs to update
parameters dynamically within the model DLL as it executes. The SIT Set
Model Parameters VI receives parameters from the controls on the front
panel and updates the model DLL when the parameters change.
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Creating a Real-Time Model-Based Control
By combining the Simulation Interface VIs with DAQ I/O, you can
implement real-time control systems or hardware-in-the-loop simulation.
By using the DAQ functions in LabVIEW RT applications, the VIs execute
simulation models in real time with real I/O. The following example VI,
ModelName_daq_driver VI, is an example block diagram of this type
of VI.
Figure 3. ModelName_daq_driver VI
The ModelName_daq_driver VI uses a continuous single-point analog
input operation to control the timing of the VI. The analog output is a
continuous single-point operation. The scan clock of the analog input
controls the time interval between scans of the analog output. Notice that
the number of analog input channels must equal the number of inports in
the simulation model, and the number of analog output channels must equal
the number of outports.
Refer to the DAQ examples located in \labview\examples
\daq\solution\control.llb and the LabVIEW RT examples located
in \labview\examples\rt\RT Control.llb for more examples of
real-time control using DAQ functions.
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