- 1 iKart hardware description
- 2 iKart Software
- 3 Using the iKart (quick start guide)
- 4 iKart (re)installation
- 5 iKart and ROS
- 6 iKart dimensions
- 7 Important things to remember
iKart hardware description
Motor control boards
The three idle wheels of the iKart platform are equipped with a suspension mechanism. The preload of the suspensions can be individually tuned through a screw that is located on the top of the mechanism, inside the iKart. During the iKart assembly, the preload is tuned in order to take in account the weight of the battery and of the whole iCub placed on the top of the platform.
CAN to USB converter
A CAN-USB2 converter is used to communicate with the motor control boards. The interface is located under the front plate, on the right side. Technical information about the CAN-USB2 converter can be found on the manufacturer website: http://www.esd.eu/esd2004/german/PDF-file/CAN/Englisch/can-usb2_e.pdf
Internal power supply
The iKart in equipped with three internal power supply modules:
- An ATX power supply (input: 48V) which provides power to the iKart motherboard.
- A 48V-to-12V DC/DC converter, which provides power to the laser rangefinder.
- A 48V-to-5V DC/DC converter, which provides power supply to the wireless switch.
An UTM-30LX Laser Range finder (Hokuyo Ltd) is mounted in front of the iKart. It is powered by the iKart 48-to-12V DC/DC converter, while the data are transmitted on through a separated USB cable. The range finder is able to detect obstacles up to 30m, with a scan angle of 270 degrees. The maximum refresh rate is 40Hz.
The joystick receiver is a standard XBox 360 wireless receiver. It is placed on the of the battery and is connected to an internal USB connector. The wireless range is about 10 meters.
External power supply (read carefully!)
iKart uses the same external power supply of iCub (please refer to: http://eris.liralab.it/wiki/Power_supply) although with different settings. The external power supply must be in fact configured in order to provide a voltage of 52.5V with a current limit of 18A. Using these settings is extremely important:
- Since the iKart battery has a nominal voltage of 52V, the external power supply voltage must be always higher then the battery voltage, in order to prevent an undesired battery discharge when the iKart power supply switch is set to battery (blue led on).
- A current limit of 18A, instead, is required in order to prevent accidental brownouts due to to the high inrush-current when the iKart motor switch is turned on. Since an unexpected reset during a write operation on the disk may compromise the integrity of the saved data, it is extremely important to increase the current limit of the power supply to 18A.
In this section the core modules required to run the iKart are described. A diagram describing how these module are interconnected is presented below (click to enlarge).
iKart uses the same iCubInterface application used by the iCub to communicate with the motor control boards. The system configuration is specified in the files iKart.ini and ikart_wheels.ini, which are located in the $IKART_ROOT\app\iKart\conf folder and installed by the make install command in the folder $ICUB_ROOT\app. The robot configuration is extremely simple, since a single CANbus line is used. This results in a single Yarp device driver which is used to control the robot analogously to the way in which iCub is controlled. The only difference between the two is that instead of having multiple robot parts such as head, left_arm, right_leg, etc. iKart has one only robot part, called wheels.
The joystickCtrl module allows to take the input from a joystick and send it on a yarp port (by default: /joystickCtrl:o). The module takes in input a .ini file in which the user can specify the configuration of the joystick, including axis remapping, different scaling factors, deadbands, etc. A complete list of the available configuration options is reported in the module documentation.
Below is reported the default joystick configuration to control the iKart. The joystick configuration is specified in the file: $ICUB_ROOT/app/joystickCtrl/iKart.ini
The laserScannerGUI provides a simple graphical interface in order to visualize the measurements performed by the frontal laser rangefinder. The module receives the measurements from the iKartCtrl module through the /ikart/laser:o yarp port. A list of all the available options (e.g. zoom, refresh rate etc.) is displayed by pressing the key 'h'.
The iKartBattteryManager is the module responsible of verifying the status of charge (SoC) of the battery. The module is automatically started from the script /etc/rc.local during the boot sequence (see also ...) and periodically reads the from the /dev/ttyUSB0 serial port the SoC of the battery. The default update rate is 10 seconds. In order to preserve the robot sensible components from dangerous brownouts, the module takes the following actions if the battery is low:
- The user will be notified with a wall message if the charge of the battery level is lower than 10%.
- If the battery reaches a critical level (below 5%), the module will start an emergency shutdown procedure, by stopping the iCub and iKart motor interfaces, and turning off the machine, with a two minutes advance notice.
The module executes independently if the yarp server is running or not. If yes, infomation about the SoC of the battery is sent through the /ikart/battery:o port. You can also ask the module to save a timestamped logfile of the performed battery measurements, by specifying the option --logToFile into the startup script (default: off).
The iKartBatteryDisplay is a graphical tool which displays the current SoC of the battery. The module receives the battery info from the iKartBatteryManager module through the /ikart/battery:o yarp port. Since the iKart obviously doesn't have a graphical output, this module will not run on the iKart machine. Instead, the iKartBatteryDisplay is thought to be executed by the user on all the machines remotely connected to the iKart. The provided always-on-top window will remember to the user the remaining autonomy of the robot, so it's a good idea to execute to keep an iKartBatteryDisplay instance always running on each user machine connected to the iKart.
Starting the iKart with the joystick
There are cases in which you may want to start moving the iKart just after the boot, without connecting to the robot in ssh, starting all the application etc. This joystick start-up is particularly useful if, for example, you turned on the iKart in a room where there is no wireless connection, and you want to move it to another room. In order to command the iKart to perform a joystick start-up, you have to follow the procedure:
- Turn on the the iKart (with the motor switch on and the fault button unpressed).
- Turn on your joystick by pressing the central joystick button.
- Wait for the beep coming from the iKart, indicating that the boot is finished.
- At this point you have for 5 seconds the chance, by pressing any button on the joystick (or moving the sticks) to initiate the joystick start-up procedure.
If a the joystick activity has been detected, the iKart will automatically initialize the following processes (and will make automatoically all the required connections):
- The Yarp server.
- The iCubInterface required to control the iKart motors.
- The iKartControl module.
- The joystickControl module.
You will be now able to move the iKart around usually the joystick as in normal operation.
How the joystick-startup procedure works
The script responsible for the joystick-startup procedure is ikart_start.sh which is originally located under $IKART_ROOT/app/iKart/ikart_boot and copied to $ICUB_BIN during the installation procedure. The scripts executes the joystickCheck module in order to verify if a joystick activity is detect, and executes initializes the yarp server and the control software if so. The ikart_start.sh script is automatically executed from the main boot script /etc/rc.local after the low-level drivers initialization.
Stopping/Restarting the joystick-startup
An analogous script ikart_stop.sh is provided in order to stop all the modules launched by the ikart_start.sh script, when controlling the iKart is no longer required. Currently, there is no way to execute this script using the joystick, so it has to be manually invoked through an ssh connection to iKart. Please also note the yarp server started by the ikart_start.sh script will be not stopped by the ikart_stop.sh script. Finally, remember that the joystick start-up procedure, which is particularly convenient during the boot, can be also manually invoked anytime, by launching the ikart_start.sh script from a console, or through an ssh connection.
In this section only the core iKart module have been described. Additional user modules, providing useful functionalities, such as reactive navigation, force control etc. are contained in the iKart repository. Please refer to the individual module documentation for a detailed description of their usage.
Using the iKart (quick start guide)
Additional information related to the installation/configuration of iKart software are reported in this section.
The two motor control boards use a firmware version which is different respect to the iCub. The firmware version is called 3.51 and the binary file can be found in $ICUB_ROOT\firmware\build\2BLL.iKart.out.S. The firmware of the boards can be upgraded using the canLoader application, as in iCub (see also: http://eris.liralab.it/wiki/CanLoader). The CAN interface must be set to socketCAN and the bus number to 0.
iKart uses an ESD CAN-USB2 interface to communicate with the motor control board. The driver of the CAN-USB2 interface is contained in the socketcan linux package (further documentation here: http://lxr.linux.no/linux+v2.6.36/Documentation/networking/can.txt). You should check the installation of the socketcan package from the the kernel module configuration menu (by launching make menuconfig from the /usr/src/linux directory). Please be sure that the following kernel modules/options are installed/enabled:
- networking support
- CAN bus subsystem support
- Raw CAN Protocol
- Broadcast Manager CAN Protocol
- CAN Device Drivers
- CAN bit-timing calculation
- CAN bus subsystem support
After compiling the kernel, you can check if the driver modules are correctly loaded by:
- typing dmesg and searching for a string similar to esd_usb2 2-1:1.0: device can0 registered.
- modprobing the modules can, can_raw, can_bcm.
Additionally to the kernel modules installation, the can-usb2 driver has to be initialized by the user before using it. This operation is automatically performed at the end of the iKart boot sequence, by a line contained in the /etc/rc.local script:
ip link set can0 up type can bitrate 1000000
iKart uses the xboxdrv userspace driver (further information can be found on: http://pingus.seul.org/~grumbel/xboxdrv). Since the driver runs in the user space, no additional kernel modules are required. Instead, it is highly recommended to blacklist the xpad kernel module (which is the Ubuntu default choice) since the two drivers can enter in conflict. This operation is performed by editing the file /etc/modprobe.d/blacklist.conf and adding a line:
The driver is automatically launched at the end of the iKart boot sequence by the following line of the etc/rc.local file:
The main iKart start-up scripts are stored in the $IKART_ROOT\app\iKart\ikart_boot directory. In particular:
- rc.local : It is the main script that initializes the hardware drivers. It is invoked by the operating system during the boot sequence. During the iKart installation, the script must be copied to the /etc directory. All the commands included in this file are executed with super-user privileges.
- ikart_start.sh : It is invoked by the /etc/rc.local script. The script checks if joystick activity is detected and, if so, automatically starts the yarp server and the iKart motor interface. The script must be copied to the $ICUB_BIN directory.
- ikart_stop.sh : It can be executed by the user to stop the modules previously launched by ikart_start.sh. The script must be copied to the $ICUB_BIN directory.
- .bashrc : This script configures the user environment variables. It includes the default search paths for the yarp/icub software. The script must be copied to the $HOME directory.
Yarp and iCub repositories
The yarp and iCub repositories are located under the folders /usr/local/src/robot/yarp2 and /usr/local/src/robot/iCub respectively.
When compiling the Yarp repository on the iKart, please check that the following mandatory cmake options are turned on:
CREATE_GUIS CREATE_LIB_MATH CREATE_DEVICE_LIBRARY_MODULES ENABLE_yarpmod_serial ENABLE_yarpmod_serialport ENABLE_yarpmod_laserHokuyo
When compiling the iCub repository on the iKart, please check that the following mandatory cmake options are turned on:
ENABLE_icubmod_canmotioncontrol ENABLE_icubmod_debugInterfaceClient ENABLE_icubmod_socketcan
iKart and ROS
Important things to remember
- The external power supply settings are different respect to the iCub. The supply voltage must be set to 52.5V ant the current limit to 18A.
- The iCub configuration file must be edited in order to disable the robot legs.
- When moving around the iKart, be sure that the arms are put in a safe position (i.e. not fully extended) in order to avoid collisions with the surrounding environment.
- Remember to replace the wireless joystick batteries regularly.