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Real Time System Design
Lab 4: Multi-core Real-Time
Suspension Controller using
LabVIEW RTOS
TA: Aws Abu-Khudhair
(aabukhud@uoguelph.ca)
Due: Week of Nov. 30th
Aws Abu-Khudhair
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Today’s Activities
 Lab 4 Introduction.
 Lab 3 Demos.
 Start work on Lab 4.
Aws Abu-Khudhair
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Lab 4 Development Environment




Host PC (HP)
Target Quad-Core PC (Dell)
NI PCI-6229 DAQ
LabVIEW 2009 software
 Standard Module.
 Real-Time Development Module
 Trace Execution Toolkit
Aws Abu-Khudhair
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Lab 4 Requirements
 The final goal of lab 4 is to implement
a half-car vehicle suspension system
model using the quarter-car
suspension implemented in lab 2.
 The implementation is divided into
two main components:
 RT Target PC: LQR control system
 Host PC: Half-Car suspension system
plant model.
Aws Abu-Khudhair
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Lab 4 Architecture
Aws Abu-Khudhair
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Half-Car Suspension Model
Host PC Implementation
Road Disturbance
Half-Car Suspension system
System States
Front Quarter-Car
Suspension
Rear Quarter-Car
Suspension
Communication and
Synchronization Task
Damping
Coefficients
DAQmx
Host PC Implementation
 Two quarter-car models representing the
front and rear suspension systems.
 Road profile input
 Generated using a time-delayed sine wave.
Assume that the rear suspension is 2 samples
behind the front suspension.
 The ride quality of the half-car body must
be calculated using equation 2.27 in the lab
manual.
Real-Time Target PC
Implementation
Real-Time Target PC
Implementation
 Implement two separate LQR controllers
using the equation 2.14 of the manual.
 Each of the LQR controller must execute on
a dedicated CPU.
 The communication and synchronization
task must have it’s own dedicated CPU.
 Communication between the various tasks
must be implemented using Real-Time
FIFOs.
Host/Target Communication
 You have the following channels for use in your
implementation:
 Host PC:
 2 Analog Outputs
 2 Analog Inputs
 1 Digital Output
 Target PC:
 2 Analog Outputs
 2 Analog Inputs
 1 Digital Input
 Note: You’ll need to handle timing to try and
make sure your transmissions are not delayed
and data sets are not separated.
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Lab 4 – Requirements/Steps
 Step 1: Configure your target computer in
NIMax (slide 22)
 Step 2: Setup your project file (slide 25)
 Step 3: On the Host PC implement the halfcar suspension system by duplicating your
quarter-car suspension model from Lab 2.
Lab 4 – Requirements/Steps cont.
 Step 4: Review the DAQmx examples in LabVIEW.
 Step 5: Build the synchronization and communication
process between the plant system and controller
using the DAQmx interface.
 Communication must be implemented using the two
connection blocks.
 Task communication must be performed using queues
on the host PC, and Real-Time FIFOs on the RT target
PC
 Step 6: On the target PC implement two LQR
controllers each occupying a dedicated CPU (one for
each suspension system)
Lab 4 – Requirements/Steps cont.
 Step 7: Test the correctness of your designs
operation using:
 Expected SASS response.
 The Performance Profiler (slide 42).
 RT System Manager (slide 44).
 The Execution Trace Toolkit (slide 48).
 Step 8: Experiment with changing parameters
such as: Loop priority, Timing, processor
allocation, and SubVI priority, and observe the
behavior of your design using the RTSM and the
RTETT.
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Lab 4 Demo Requirements
 For the demo the following are some of the
aspects that will be examined:
 Model Response (both with and without semiactive control)
 Communication between the host and target
 Understanding of the implementation layout in
LabVIEW.
 Understanding of the Execution Trace Toolkit
figures.
 LabVIEW RT Concepts
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Lab 4 Report Requirements
1.
Introduction:


2.
Briefly describe the problem (i.e. what system are you
implementing, why is control required, difference from
implementation in lab 2, etc…)
System Requirements.
Implementation:



Equipment used.
Short overview of the benefits of using the LV RTOS.
Present your designed control strategy, discuss the
number of cores used, and which tasks will be
allocated on which core. Also, present your proposed
communication method.
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Lab 4 Report Requirements cont.
2. Implementation Cont.


Present your LabVIEW implementation of the
system. Similar to the lab three report, you do
not need to document the theory behind your
implementation. You should, however, note
where each major component is in your
implementation (i.e. what’s located on the host,
what’s on the target, etc.). Make sure you
document how communication is being
performed.
Fully document your LabVIEW code, include
screen shots of the implementation when
explaining the various components.
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Lab 4 Report Requirements cont.
3. Simulation/Results

Simulation results – document your system’s
performance under various configurations.
Timing and CPU usage can be obtained using
the performance analyzer, the RTSM and the
RTETT. Experiment with changing the periods of
the loops, processor allocation, and assigned VI
and loop priorities. Use figures where
appropriate to document the results (e.g. RTSM
usage graph, and VI/Thread execution graphs
from the RTETT).
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Lab 4 Report Requirements cont.
3. Simulation/Results cont.
 Discuss any changes that need to be made
to your design to obtain a better system
performance in terms of the memory
consumption, CPU performance, Core
allocation, etc.
 Replace the Timed loops in the
implementation with standard while loops
and comment of any change in
performance (use figures from the RTETT).
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Lab 4 Report Requirements cont.
4. Conclusion:

Provide a brief concluding statements on the lab
based upon your implementation and the
observed effects of varying parameters. This
section should be clear and concise.
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Deadlines and Marking
 Lab 2 is worth 12%.
 6% for the report, and 6% for the demo
 The Demo is due Nov. 30th, 2010 in the
Lab.
 The Report is due Nov. 30th, 2010 in the
Lab.
 A signed group evaluation sheet must be
submitted with the lab report
 QUESTIONS?
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Target Configuration
 Step 1: Open NI- Measurement and Automation
(NIMax) on the host computer and expand the remote
systems tab. Find your un-configured target.
 Step 2: Go to the network settings to configure the
target name and IP address.
 Step 3: Enter a valid Target Name under the target
identification.
 Step 4: Choose ‘Obtain an IP address automatically’
under the IP settings.
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Target Configuration cont.
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Target Configuration cont.
 Step 5: Click “Apply” and choose to restart
the target.
 Step 6: After allowing the target to reboot,
look for the name you chose for your target
under ‘Remote Systems’ in NIMax.
At this point your target PC should have
rebooted into LabVIEW RT and is ready to
be added as a target PC to your project.
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Creating a LabVIEW RT Project
 Step 1: Create a
Real-Time Project.
 Step 2: Select the
‘Continuous
communication
architecture’
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Creating a LabVIEW RT Project
cont.
 Step 3: Add your
configured target PC
to your project.
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Project Organization
 You can experiment with the organization
of your project to find what you feel works
best.
 Note that priorities can be set at the VI
level (I.E. “Time-Critical”, “Normal”, etc..)
and in timed loops running within a VI.
 Group similar tasks together.
 Start off making use of three cores and
change the allocations later as you see fit.
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Useful Tools
 SubVIs: used to build frequently used
functions that can later be added to
the main VI.
 Global and Shared Variables: used to
move data between loops and VIs.
 DAQmx channels and tasks for
connected devices: used to move
data between the host and target
PCs.
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Useful Tools
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Creating SubVI
 SubVIs can be created as functions to be used in the
main VI.
 These subVIs can have their own priorities predefined
(default priority is ‘Normal’).
 To create your own VI:
 Build you function on the block diagram.
 Right click the VI icon on the top left corner of the
front panel.
 From here you can define the terminal the VI needs,
and the shape of the icon.
 Drag your newly created subVI onto your main block
diagram.
 Remember that by default the VIs are not set for
reentrant execution.
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Creating SubVI cont.
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Right click icon
to get VI related
options
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VI Properties
 VI properties can be set by going to “File””VI
Properties”. You can set then enable debugging (active
by default) and set them as normal or time-critical.
Most needed options can be found under “execution”
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Useful Structures - Communication
 In order to send and receive data, you’ll
need to setup NI-DAQmx tasks.
 To do this, right click on the desired PC
(host or target) and go to “New DAQmx
task”. Configuration is then performed in
the same fashion as using a DAQ assistant.
 You can then drag the configured channel
or task on to the block diagram.
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Useful Structures - Communication
 Right-clicking on the channel or task
will give you the option to access the
DAQmx pallet where you can find the
blocks for both reading and writing.
The configured channel/task can then
be connected as shown below.
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Useful Structures – Timed Loops
 Within a VI, timed loops can be
placed. The loops can be configured
to have different priorities, execution
periods, and processor allocations.
Double click the left terminal to
get the configuration window
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Useful Structures – Timed Loops
Useful Link:
http://www.ni.com/swf/presentation/us/labview/timeloop/
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Passing Data Between Threads
 Data should be passed between tasks
and timed loops using one of the
following methods:
 Global Variables  Good
 Functional global Variables  Better
 RT FIFO VIs Best method.
**See the LabVIEW RT Manual pg. 3-34**
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Global Variables (GVs)
 Shared resource  can cause jitter
 Global variables may be written to many
times before being read.
 Using GVs in time-critical tasks can
compromise determinism.
 If one task accesses the variable, no other task
can access it until the first task releases the
variable, hence the second task will be forced to
wait, therefore introducing jitter.
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Functional Global Variables (FGVs)
 Avoid shared resource problems by using
FGVs.
 Can have several inputs and outputs.
 Allows for a ‘skip if busy’ function.
 Functional global variables can be a lossy
form of communication, if a VI overwrites
the shift register data before another VI
reads the data.
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Real-Time FIFO (RT-FIFO)
 Best method of communication.
 Ensures determinism of time-critical
tasks.
 Uses fixed buffer size.
 An RT-FIFO can be a lossy
communication method. When the FIFO
gets full, the system starts to overwrite
the old data.
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Performance Analysis
 LabVIEW Real-Time has several tools that
can be used to evaluate the performance and
response of your system.
 Performance Profiler
 Real-Time Systems Manager
 Real-Time Execution Trace Toolkit
 Note that your application needs to be
running on the target for any performance
metrics to be recorded.
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Performance Profiler
 Can be used to track the timing
statistics of both main and sub VIs.
 The performance profiler can also be
used to track the memory usage of a
given part of the application.
 It can be opened by going to “Tools
 Profile  Performance and
Memory”
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Performance Profiler
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Real-Time Systems Manager
(RTSM)
 The RTSM can be used to track the
proportional CPU usage of each processor.
 It can also be used to start and stop toplevel VIs during execution on the target to
evaluate the effects on CPU load.
 The RTSM runs on the host computer and
receives information from the target during
operation.
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Real-Time Systems Manager
(RTSM) cont.
 The RTSM can be found under “Tools 
Real-Time Module  System Manager”.
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RTSM configuration
 In order to use the RTSM, you need to
configure TCP/IP communication between
the target and host computers.
 Under the properties of the target computer,
make sure that TCP/IP is enabled in the “VI
Server: Configuration” menu.
 Add the host’s IP address (this can be
checked using “ipconfig/all”) to the list of
permitted machines under the “VI Server:
Machine Access” menu.
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RTSM configuration
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Real-Time Execution Toolkit
 Use the Execution Trace Toolkit to capture
the timing and execution data of VIs and
thread events for your implementation.
 In LabVIEW select “Tools  Real-Time
Execution Trace Toolkit”.
 Before you use the toolkit to observe your
application performance, go through the
toolkit examples in “Help  Open Example
Session” in the RTETT window.
 For examples on how to use the toolkit see the
context help of the toolkit Vis (search Execution
Trace in the LabVIEW function pallet)
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Real-Time Execution Toolkit
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