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User Manual
Quanser Qbot
Quanser Qbot: User Manual
Table of Contents
1. Introduction..........................................................................................................................1
2. Prerequisites.........................................................................................................................2
3. References............................................................................................................................2
4. System Hardware Description.............................................................................................3
4.1. Qbot Ground Vehicle....................................................................................................3
4.1.1. The iRobot Create®.............................................................................................3
4.1.2. The Printed Circuit Board (PCB).........................................................................4
4.1.2.1. Digital Input/Output Pins (DIO #)................................................................5
4.1.2.2. Gumstix IR Serial Pins.................................................................................5
4.1.2.3. SW/nSW and INT/EXT Jumpers..................................................................6
4.2. Detailed Description of Qbot Components..................................................................6
4.2.1. Qbot DAC............................................................................................................6
4.2.2. USB Camera.........................................................................................................6
4.2.3. Gumstix................................................................................................................7
4.2.4. Battery..................................................................................................................7
4.2.5. Infrared Sensors....................................................................................................8
4.2.6. Sonar Sensors.......................................................................................................9
4.3. System Specifications and Model Parameters.............................................................9
5. System Setup........................................................................................................................9
5.1. Setting up the Qbot....................................................................................................10
5.2. Establishing Wireless Connection..............................................................................10
5.3. QUARC – Quanser Real-Time Control.....................................................................10
5.4. Using the on-board camera........................................................................................17
6. Troubleshooting Guide.....................................................................................................18
6.1. Qbot Drive or Direct Drive commands aren't responding or are causing the robot to
move incorrectly, or the Qbot bump sensor inputs are not functioning............................18
6.2. The model fails to build/connect or the QUARC console does not successfully open..
19
6.3. The Qbot sensors are not being read correctly or they are stuck at some constant
value..................................................................................................................................20
6.4. The Qbot magnetometer values drift while the Qbot is moving in a straight line.....20
6.5. The Simulink model appears to run slowly (i.e., the simulation time runs slower than
actual time), or the console displays the message “Sampling rate is too fast for base rate”.
...........................................................................................................................................21
6.6. Trying to start the Qbot model results in the error “Unable to locate the dynamic link
library or shared object.”...................................................................................................21
6.7. The LEDs QBOT POWER and GUMSTIX POWER do not illuminate when the
Qbot robot is powered on..................................................................................................22
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6.8. Building a model fails with the error “Not enough system resources are available to
perform the operation.” The hard disk is full on the Gumstix computer..........................22
6.9. The Display Image block is not showing any image..................................................22
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Quanser Qbot: User Manual
1. Introduction
The Quanser Qbot (Figure 1) is an innovative autonomous ground robot system
incorporating a robust educational ground vehicle with the Quanser Controller Module
(QCM). The vehicle is comprised of a iRobot Create® robotic platform, an array of optional
infrared and sonar sensors, and a Logitech Quickcam Pro 9000 USB camera. The QCM is
an embedded system mounted on the vehicle, which uses the Gumstix computer [2] to run
QUARC, Quanser's real-time control software, and the Qbot data acquisition card (DAC).
Figure 1: The Quanser Qbot - top view
The interface to the QCM is MATLAB Simulink with QUARC. The Qbot is accessible
through three different block sets: the Roomba block set to drive the vehicle, the HIL block
set to read from sensors and/or write to servo outputs, and finally the OpenCV block set to
access the camera. The controllers are developed in Simulink with QUARC on the host
computer, and these models are downloaded and compiled into executables on the target
(Gumstix [2]) seamlessly. A diagram of this configuration is shown in Figure 2.
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Figure 2: Communication Hierarchy
Section 2 goes through the laboratory requirements, and Section 3 lists various documents
that are referenced in this manual. The general system description, component
nomenclature, specifications, and model parameters are all given in Section 4. Section 5
goes into detail on how to setup the Qbot. Lastly, Section 6 contains a troubleshooting
guide.
2. Prerequisites
To successfully operate the Qbot, the prerequisites are:
i) To be familiar with the components of the Qbot.
ii) To have QUARC version 2.2 or later installed (NOTE: You must install the beta
components by selecting them during installation, since some blocks used with
the Qbot are found in the QUARC beta library) and properly licensed.
iii) To be familiar with using QUARC to control and monitor the vehicle in real-time,
and in designing a controller through Simulink. See Reference [2] for more details.
3. References
[1] Gumstix:
http://gumstix.com/
[2] QUARC User Manual (type doc quarc in Matlab to access)
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[3] iRobot Create Open Interface Specification Sheet
[4] iRobot Create Owner's Guide
[5] SHARP 2Y0A02 IR Range Sensor.pdf
[6] LV-MaxSonar-EZ0-Datasheet.pdf
4. System Hardware Description
4.1. Qbot Ground Vehicle
4.1.1. The iRobot Create®
The Qbot uses an iRobot Create® frame (Figure 3). The Qbot follows the Quanser standard
for body frame axes, where the x-axis is in the forward direction, the y-axis is to the left, and
Figure 3: Anatomy of the Qbot, showing various components and body axes
the z-axis is up. The diameter of the vehicle is 34 cm, and its height (without camera attachment) is 7 cm. and it is driven by two differential drive wheels. The iRobot Create® comes
with a bumper sensor and an omni-directional infrared receiver. The QCM can access data
from these sensors.
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The Qbot is turned on by pressing the power button (more on Section 5.1). Figure 4 below
shows the buttons that are used to operate the iRobot Create®. The Play and Advance but tons are for built-in demos for the vehicle, and are not necessary for Qbot purposes.
Figure 4: Buttons on the Qbot Frame
4.1.2. The Printed Circuit Board (PCB)
The printed circuit board (PCB) contains the wiring and circuitry for the Qbot. It also acts as
a cover for the DAC and Gumstix, and mounts for infrared sensors, sonar sensors, and webcam. Figure 5 shows the accessible pins for the user. In particular, the DIO, PWM output,
and analog input pins have been labeled for clarity.
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Figure 5: Qbot PCB showing available pins for the PWM output, Digital Input/Output
and Analog Input pins, serial pins, and jumpers for INT/EXT power
4.1.2.1. Digital Input/Output Pins (DIO #)
The DIO channels (0 to 6) are set as inputs by default. The DIO channels need to be configured as either inputs (or outputs, but not both) using the HIL Initialize block. Also, if an
output needs to be in a known state on power up, it is recommended that a 10k resistor is
put from the I/O to 5V or GND as needed.
There is a final digital channel (7) that is a fixed output, and it is represented by an LED
labeled DIO7.
4.1.2.2. Gumstix IR Serial Pins
The Qbot provides a TTL serial connection to the Gumstix IR serial port (port number 2).
The serial port consists of ground (GND), receive (GUMSTIX IR RXD), transmit (GUMSTIX IR TXD), and power (+3.3V or +5.0V) pins. The serial port is accessed through the
QUARC Stream blockset or Stream API. For more information on accessing serial data see
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the QUARC help QUARC Targets/User's Guide/Communications.
4.1.2.3. SW/nSW and INT/EXT Jumpers
The INT/EXT jumper switches the Qbot from internal power from the iRobot Create battery
(INT) and an external battery power supply (EXT). Note that no external battery is supplied
with the Qbot, so this jumper should be left in the INT position to power the Qbot. When
the power source jumper is in the INT position, the SW/nSW jumper indicates whether the
iRobot Create must be switched on (SW) for the Qbot to receive power, or whether the Qbot
should always draw power even when the iRobot Create is off (nSW).
4.2. Detailed Description of Qbot Components
4.2.1. Qbot DAC
The Qbot DAC is a data acquisition board, capable of receiving analog inputs and other inputs (for sonar sensors). It is also capable of writing PWM outputs for possible servo actuators. It is located underneath the black cover of the Qbot, and it is not intended for it to be
physically accessed.
4.2.2. USB Camera
The Logitech Quickcam Pro 9000 USB camera is mounted on top of the Qbot (Figure 6).
The QUARC block set that uses the Open Source Computer Vision library (in Section 5.3)
allows the user to capture and display images in real time, process them, and save them in a
disk for future analysis.
Figure 6: Camera
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4.2.3. Gumstix
The Gumstix is a small-scale, fully functional, open source computer. With QUARC installed, code generated from MATLAB is downloaded, compiled, and executed directly on
the Gumstix.
The Gumstix motherboard is connected directly to the Qbot DAC. The Gumstix also comes
with the Wifi attachment board to allow wireless connection between the target Gumstix
and the host computer and/or other vehicles.
The IP of the Gumstix will be provided.
4.2.4. Battery
The Qbot is powered by the Advanced Power System (APS) Battery (Figure 7) provided by
iRobot. The battery fits underneath the Qbot (Figure 8), and can last continuously for about
2 hours after a full charge. The Qbot's power light indicates the power level of the battery.
The light is green when the batteries are fresh, then gradually turns red as the battery
discharges. The battery takes less than 3 hours to charge. While charging, the power light
pulses slowly with an orange colour. A battery charger will be provided.
Figure 7: The Qbot Battery, the Advanced Power System
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Figure 8: Bottom view of the Qbot, highlighted with battery location
4.2.5. Infrared Sensors
The SHARP 2Y0A02 [5] is a low cost infrared range sensor (20-150 cm). There are five of
these sensors included with the Qbot. The sensors are connected to the analog input channels of the Qbot DAC, which can then be read using the HIL Read Write block (Section
5.3).
Figure 9: SHARP GP2D12 IR
Sensor
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4.2.6. Sonar Sensors
Figure 10: LV-MaxSonar-EZ0
Sonar Range Finder
The MaxSonar-EZ0 [6] is a very short to long-range detection and ranging sonar sensor
(Figure 10). The MaxSonar-EZ0 detects objects from 0-inches to 254-inches (6.45-meters)
and provides sonar range information from 6-inches out to 254-inches with 1-inch resolution. Objects between 0-inches and 6-inches range as 6-inches. There are three of these
sensors included with the Qbot. The sensors are connected to the other input channels of the
Qbot DAC, which can then be read using the HIL Read Write block (Section 5.3).
4.3. System Specifications and Model Parameters
Table 1 below lists the main parameters associated with the Quanser Qbot.
Symbol Description Value Unit
d Diameter of the Qbot
h Height of the Qbot (with camera
0.34
0.19
m
m
attachment)
v
max
Maximum speed of the Qbot
m Total mass of the Qbot
Table 1 Qbot Model Parameters and System Specifications
0.5
2.92
m/s
kg
5. System Setup
In Section 5.1, instruction is given on how to assemble the vehicle. Section 5.2 walks
through setting up a wireless connection with Windows. Finally, Section 5.3 explains how
to properly setup the QUARC-Simulink interface so that the user can communicate with the
Gumstix.
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5.1. Setting up the Qbot
Follow these steps to setup the Quanser Qbot:
1. Insert the battery underneath the Qbot.
2. Press power button shown in Figure 4. This turns on both vehicle and Qbot
DAC/Gumstix.
5.2. Establishing Wireless Connection
In order to establish wireless communications between the host PC and the Gumstix embedded computers, a wireless ad-hoc (peer-to-peer) network is used. Each Gumstix target is assigned a unique IP address between 182.168.1.20 and 182.168.1.254. A wireless adapter is
provided with the system for the host PC. The IP address of this wireless adapter must also
be a unique IP address that is not already used by any Gumstix computer or another host PC.
The host PC wireless IP address should be set to an unused value between 182.168.1.10 and
182.168.1.19. If you are setting up only one host PC, set the wireless IP address to
182.168.1.10. For additional host PCs, set their IP addresses by incrementing the last digit,
e.g., 182.168.1.11, then 182.168.1.12, etc.
1. Windows should detect a network called GSAH, an “Unsecured Computer-to-Computer
Network”. Connect to it.
2. Open the Status of the wireless network, then click on Properties.
3. Under “This connection uses the following items:”, scroll down to Internet Protocol
(TCP/IP), then double click on it.
4. Instead of obtaining an IP address of the computer automatically, enter the following:
IP address: 182.168.1.xxx (any unused number)
Subnet mask: 255.255.255.0
Default gateway: 182.168.1.xxx (same as IP)
5. The Gumstix can be pinged by typing “ping {IP of Gumstix}” in the Run box in Windows. If the connection is successful you will see the ping replies in the command win dow. Note: you may need to disable Windows firewall to establish a connection.
5.3. QUARC – Quanser Real-Time Control
Simulink should have a new menu item called QUARC once QUARC has been installed.
Note: QUARC should be installed with beta library components selected since the
Qbot uses some QUARC components that are found in the beta library.
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The following steps are required to setup QUARC for the Qbot:
1. Create a new Simulink model, or open an existing model to be run on the Gumstix.
2. Click on the QUARC menu, then select Options.
3. The System target file under Real-Time Workshop should be quarc_linux_verdex.tlc.
Browse through the system target list to locate the proper file if necessary.
4. Next, choose Interface on the left hand pane. Under the MEX-file arguments, type '-w
-d /tmp -uri %u', 'tcpip://{IP of Gumstix}:17001'. Include the single quotation marks
(Figure 11). Replace {IP of Gumstix} with the IP of your Gumstix, e.g.
'tcpip://182.168.1.200:17001'.
Figure 11: Configuring MEX-file Arguments
5. In the Simulink Library Browser, navigate down QUARC Targets → Devices → ThirdParty → iRobot → Roomba → Interfacing. The Roomba Initialize block is required for
the Gumstix to communicate with the Qbot. Change the URI to “serial://localhost:1?
baud=57600,word=8,parity=none,stop=1” (Local host is 2 by default). Use default send
receive bytes.
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6. In the Simulink Library Browser, navigate down QUARC Targets → Data Acquisition →
Generic → Configuration. The HIL Initialize block is required to communicate with the
Qbot DAC. Choose a Board name. Select the board type "qbot" to target the Qbot when
running the model.
7. Add the HIL Read Write block from QUARC Targets → Data Acquisition → Generic →
Immediate I/O to read infrared sensor (analog) and sonar measurements from the vehicle.
The Qbot DAC also supports PWM write channels [0:3].
8. For image processing using the on-board camera, use the blocks in QUARC Targets Beta
→ Image Processing → Open Source Computer Vision.
9. Select “External” for simulation mode, instead of “Normal”, which indicates that the
model is to be run on the target machine (Gumstix) rather than simulating the model on
the host machine. Table 2 and Table 4 list the block sets supported by the Quanser Qbot,
and Table 3 highlights the more important Qbot blocks.
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Block set Description
Interface
(Figure 12)
This block set implements the basic application program interfaces (APIs) provided by
iRobot Create®. The APIs can be broadly categorized based on the following
functionalities:
● serial connection configuration between the high level controller (e.g., PC or
Gumstix) and Qbot,
● setting operation mode of Qbot,
● accessing Qbot's sensory information,
● other hardware configuration (e.g., setting digital and analog I/O ports, and
changing LED colours.
Application
(Figure 13)
Image Processing
(Figure 14)
Table 2: Description of the Relevant Qbot Block Sets for the Qbot in QUARC
Block Description
This block set allows a user to implement navigation algorithms using available sensory
information. The present blocks use only wheel encoder data and bump sensors for
navigation and obstacle avoidance.
This block set implements image acquisition and processing functionalities using the
OpenCV library. The image processing block set allows to capture images from a USB
camera, to process it on-line, and to save it to a disk for further analysis.
This block is required to establish a serial connection to a Qbot.
A Qbot is identified by a Universal Resource Identifier (URI), such as
serial://localhost:1baud=57600,word=8,parity=none,stop=1,
where communication port 1 of the target is connected to the Qbot serial port
with the specified parameters.
Note: The “rmb” output of this block must be connected to the “rmb” input of
the blocks in the Roomba block set in order to access the Roomba.
This block drives the Qbot with two inputs: velocity and radius. To drive
straight, the radius input takes 32768 or 32767. This is a special case, and refer
to the MATLAB Help page for a more complete list of possible commands.
Table 3: Important Qbot Blocks
This block retrieves various sensor data from the Qbot. The pack_id input
ranges from 7 to 42, and each input will display a value from the pack output.
See the MATLAB Help page for a full description for each of the packet IDs.
Notable pack_id values:
8 = wall (0 = no wall, 1 = wall seen)
19 = distance (The distance that the Qbot has traveled in millimeters)
20 = angle (The angle in degrees that the Qbot has turned)
22 = voltage (Voltage of the Qbot's battery in millivolts)
23 = current (Current in milliamps flowing into or out of the Qbot's
battery)
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Figure 12: Interface Block Set
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Figure 13: Application Block Set
Figure 14: Image Processing Block Set
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Block Description
Initialization block required in all QUARC models using a HIL card.
Note: only one HIL Initialize block is needed in the model to setup one
vehicle. The HIL Read Write block must reference this block to determine
the board being used.
The current version of the Qbot DAC can read from analog channels (for the
infrared sensors), and sonar channels. PWM channels are supported for
write operations.
Channel
Type
IR Input
(Analog
Read)
Analog In-
put
(Read)
Sonar Input
(Other
Read)
PWM
(Write)
Table 4: Description of the Relevant HIL Blocks for the Qbot in QUARC
Valid Channel
Ranges
[0:4] Reads infrared sensor measurements
[0:6]
[1:3] Reads sonar sensor measurements
[0:7] Gives duty cycle commands as a percent-
age (0 to 1) of a 20ms period, where values range from 0.025 to 0.125.
Description
At this point, the model is ready to be compiled and executed on the target.
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5.4. Using the on-board camera
The Qbot is equipped with a Logitech QuickCam Pro 9000 USB camera. When connected
to the on-board Gumstix Verdex computer, this camera is capable of capturing up to 9
frames per second (fps). In order to acquire and display images on the host computer during
execution some additional blocks are required. Figure 15 shows an example model where
images are acquired and displayed.
Figure 15: Capturing and displaying images in QUARC.
The Vision Capture Image block is used to capture image data from the camera. The Vision
Get Iplimage Data block simply takes the image and outputs the image data as a matrix. For
the Qbot camera, color images are output as 3-dimensional matrices (3 x ImageWidth x ImageHeight) with each pixel represented by a 3-vector of [Blue, Green, Red] values between
0 and 255.
The Display Image block is used to display images on the host. This block acts like a scope
and will not delay the execution of the real-time model. The images displayed in the Display
Image block may be delayed compared to the actual image data being acquired and used in
the real-time model. The Image Convert block is used to convert the image format from the
Qbot camera (BGR8) to a format that can be displayed in MATLAB.
Note: since displaying images on the host requires a large amount of bandwidth, it is
recommended that the Display Image block be run with a sample time of 0.1 seconds or
slower. If the error “Warning: Not enough memory on the target to process the packet:
EXT_SELECT_SIGNALS” is displayed in the MATLAB Command window or data on
Scopes and the Display Image block are not displayed during model execution, the size of
the external mode buffer is too large. The Display Image block acts like a Scope and
uploads its signal (the image signal) to the host for display through Simulink's external
mode buffers. In order to resolve this issue so that images and data will be displayed the
buffer size should be reduced. To reduce the size of the buffer, either increase the model's
base rate so that it is faster or reduce the number of base rate samples used in the model's
external mode buffer by decreasing the Duration (recommended 1 to 10) in the Signal &
Triggering menu under Tools > External Mode Control Panel > Signal & Triggering.
Because the vision blocks require OpenCV2.2, models using these vision blocks must be
configured for code generation in C++. To set this parameter select the menu option
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QUARC > Options and navigate to the Code Generation page and select C++ under
Language. The LLVM-GCC cross-compiler (default compiler for the quarc_linux_verdex
target type) will not compile models using the vision blocks. The compiler can be changed
under the QUARC > Options window on the Code Generation > QUARC page. Selecting
Native GCC will use the compiler on the Verdex, which is slower than the cross-compiler
since it downloads the generated code and compiles natively on the Gumstix. To utilize a
cross-compiler, the CodeSourcery Lite cross-compiler can be used. Use of the
CodeSourcery Lite cross-compiler results in much faster compilations, but requires that the
CodeSourcery Lite cross-compiler be installed (see the Installing CodeSourcery help page in
the MATLAB help for details on downloading and installing CodeSourcery).
6. Troubleshooting Guide
For any issue, the first and easiest troubleshooting solution on any electronic device is to reboot the device. Turn off the Qbot, then turn it back on again. For troubleshooting any problem with the Qbot, it is always a good idea to open the QUARC console in case additional
information is printed to the console by going to the QUARC menu and clicking on “Console for all…”. The console must be opened after the Qbot has booted and established a wifi
connection. If the console is opened successfully it establishes a connection to the target and
the console window has the title “QUARC Console for * at tcpip://182.168.1.xxx:17000”,
where xxx corresponds to the IP address of the Qbot.
If you are still unable to resolve the issue after reading through this section, contact
tech@quanser.com for further assistance.
6.1. Qbot Drive or Direct Drive commands aren't
responding or are causing the robot to move incorrectly,
or the Qbot bump sensor inputs are not functioning.
1. Check that the Qbot wheels are retracted fully into the wheel bays. If any wheel is out of
its bay, then the Qbot will stop driving for safety reasons. Makes sure to operate the Qbot
on a hard, flat surface.
2. Turn off the Qbot and iRobot Create power and remove the jumper on the INT/EXT battery header on the Qbot. Turn on the iRobot Create and run the built-in demos and
troubleshooting steps found in the iRobot Create Owner's Guide supplied with your
Qbot. If the troubleshooting steps in the iRobot Create Owner's Guide show that the robot is working, then replace the INT/EXT battery jumper on the Qbot and continue. If the
iRobot Create demos do not work as expected, please contact iRobot technical support.
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3. Turn on the Qbot and open the VAL Read Sensors block in one of the supplied Simulink
models. In the VAL Read Sensors parameters under the “Other” channels, select the
bump sensors by typing [13000:13002]. Attach a scope or display block to the VAL Read
Sensors “Other” channels output and compile and run the model. Verify that the bump
sensors can be read by the Qbot computer by pressing the Qbot bumper and watch the
bump sensors signals go from 0 to 1 when pressed. If these signals do not change, then
open the Qbot lid by removing the four lid screws shown in Figure 16 and verify that the
Qbot computer is connected to the robot. Make sure the DB-25 connector is firmly in
place, replace and secure the Qbot lid, and retry the bump sensor test.
Figure 16: The Four Qbot Lid Screws
6.2. The model fails to build/connect or the QUARC
console does not successfully open.
1. Turn on the Qbot and look through the square window located on the lower right of the
Qbot lid. When the Qbot powers up, you will see an orange LED come on in the inner
cargo bay of the robot. After approximately 30 seconds, a blue LED will flash to indicate
the Qbot wifi is powering on, and is attempting to connect to another computer on the
ad-hoc wifi network. If the blue LED flashes and remains on, then the wifi module is
functioning and is able to find another node on the ad-hoc wireless network. If the blue
LED flashes and then turn off, the Qbot is not able to detect other nodes (e.g., the host
PC) on the ad-hoc wireless network. Check that the wifi adapter is inserted properly in
the host PC and is configured according to the network configuration procedure outlined
in this manual (System Setup\Establishing Wireless Connection). Verify that the host PC
is connected to the wireless ad-hoc (GSAH) network and try to successfully ping the
Qbot by going to the Windows Start → Run and typing “ping 182.168.1.xxx” (without
quotation marks), where xxx corresponds to the IP address of your Qbot. If the blue LED
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never flashes, the wireless antenna or wireless module may be disconnected. Turn off the
Qbot power and open the Qbot lid by removing the four lid screws shown in Figure 16
and verify that the Gumstix wireless module and antenna are properly connected. The
wireless module shown in Figure 17 is located on the bottom side of the green Gumstix
computer inside the Qbot cargo bay. Make sure the wireless module and antenna are securely connected and retry the above steps to establish a wireless connection.
Figure 17: Wifi Module
6.3. The Qbot sensors are not being read correctly or they
are stuck at some constant value.
1. Using the VAL Read Sensors block, output all possible channels. Check these outputs us-
ing scopes and displays, and determine if the problem lies with a particular sensor, or set of
sensors, or if the issue is global across all sensors.
2. Create a new Simulink model and add a HIL Initialize and HIL Write block. Select the
“qbot” board type in the HIL Initialize block. Open the HIL Write block and select only digital output channel 7. Connect either a square wave going from 0 to 1, or a constant block
to the input of the HIL Write block. Compile and run the model. Verify that the LED leveled
DIO7 on the Qbot lid turns on and off when the input to the HIL Write block goes from 1 to
0, respectively. If the DIO7 LED does not turn on, there is a communication failure between
the Gumstix and the Qbot computer.
6.4. The Qbot magnetometer values drift while the Qbot is
moving in a straight line.
1. The magnetometer detects the Earth's magnetic fields as wells as external magnetic
fields. Metal underneath the floor or in surrounding structures will affect the direction of the
magnetic fields, thus affecting the Qbot magnetometer measurements. This is a fundamental
limitation of any magnetometer device.
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6.5. The Simulink model appears to run slowly (i.e., the
simulation time runs slower than actual time), or the
console displays the message “Sampling rate is too fast
for base rate”.
1. The maximum sample rate recommended for the Qbot is 500 Hz (0.002 s). However, if
there are complex calculations (such as image processing) performed within the model, then
this could potentially limit the sample rate of the model. Try reducing the model sample rate
in the menu QUARC\Options\Solver by increasing the “Fixed-step size (fundamental
sample time)” parameter.
2. The HIL Read Write block and the VAL Read Sensors block should only be used once in
a diagram. These blocks perform large data transfers between the Qbot computer and the
controllers, so placing more than one of these blocks will cause multiple reads to be performed in the same sample instant, which is unnecessary. Use only one HIL Read Write or
VAL Read Sensors block for the entire model.
3. To determine the execution time of blocks or subsystems within the model, use the Com-
putation Time block found in the QUARC library\Sources\Time. This block outputs the
computation time of a function call subsystem, measured using an independent high-resolution time source. Blocks can be placed inside a function call subsystem and connected to the
Computation Time block to determine their execution time during each sample instant. This
helps identify the bottlenecks in the model (blocks/subsystems with the highest execution
time) and can identify blocks/subsystems whose computation time is greater than the sample
time of the model. Try increasing the sample time of those blocks whose computation time
is greater than the sample time of the model so that the blocks run in a slower rate thread.
6.6. Trying to start the Qbot model results in the error
“Unable to locate the dynamic link library or shared
object.”
1. This error indicates that the Qbot driver is not found on the target. Make sure that the
model target type is set to Linux Verdex by navigating to the QUARC menu QUARC\Options\Real-Time Workshop pane and changing the System target file to quarc_linux_verdex.tlc. Open a console through the QUARC menu QUARC\Console for all, and verify that
the console window displays the target IP of your Qbot in the window title.
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6.7. The LEDs QBOT POWER and GUMSTIX POWER do
not illuminate when the Qbot robot is powered on.
1. Verify that the jumper on the INT/EXT battery header on the Qbot lid is securely placed
in the INT position. This jumpber switches the Qbot power source from the robot's internal poewr (INT) or an external battery source (EXT). Note: an external battery to
power the Qbot is not provided with the system.
2. If the jumpers are securely in place and the power LEDs remain off when the iRobot Create is on, turn off the robot, open the Qbot lid by removing the four lid screws shown in
Figure 16, and verify that the DB-25 cable to the robot is securely connected. Replace the
lid and try to power on the Qbot.
6.8. Building a model fails with the error “Not enough
system resources are available to perform the operation.”
The hard disk is full on the Gumstix computer.
1. When several models are compiled, the disk space on the Gumstix may become full, and
you will no longer have space to build models. Using the clean option in the QUARC
menu under QUARC\Clean all will remove all generated code and compiled code for the
current model, but this will only free up the space used by the current model. Clearing all
models from the Gumstix hard disk must be done manually using PuTTY, or any ssh client. Using PuTTY, log into the Gumstix by connecting to it using the IP listed on the
Qbot, and use the user name “root”, and password “quanser” (without quotation marks).
Navigate to the /var/spool/quarc directory, which is where all generated code and compiled models reside. Use the “ls” command to list all contents of this directory to see all
models that have been downloaded to the Gumstix. Note: be careful executing any re-
move/delete command on your Gumstix, as incorrect usage could permanently
damage the file system, rendering the Qbot unusable. Individual models/code can be
manually removed from the /var/spool/quarc directory. To remove all generated code and
executable controllers, run the command “rm -rf /var/spool/quarc/*” (without quotation
marks). To confirm there are no longer any models on the Gumstix, execute the command “ls” and there should be nothing listed.
6.9. The Display Image block is not showing any image.
See Section 5.4 for an example using the camera acquisition and display blocks.
1. Ensure that the Vision Capture Image block is acquiring images by checking the “new”
output signal. If necessary, reduce the image resolution and output the image as matrix data.
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If the image is output as matrix data remove the Vision Get Iplimage Data block.
2. Check that the Image Convert block is set to convert the source image format BGR8 to
MATLAB RGB.
3. Set the Display Image sample time to 0.5 seconds.
4. If the error “Warning: Not enough memory on the target to process the packet:
EXT_SELECT_SIGNALS” is displayed in the MATLAB Command window or data on
Scopes and the Display Image block are not displayed during model execution, the size of
the external mode buffer is too large. The Display Image block acts like a Scope and
uploads its signal (the image signal) to the host for display through Simulink's external
mode buffers. In order to resolve this issue so that images and data will be displayed the
buffer size should be reduced. To reduce the size of the buffer, either increase the model's
base rate so that it is faster or reduce the number of base rate samples used in the model's
external mode buffer by decreasing the Duration in the Signal & Triggering menu under
Tools > External Mode Control Panel > Signal & Triggering.
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