Basic packages Version 3 - AutoModelCar/AutoModelCarWiki GitHub Wiki
The computer in the model car contains preinstalled packages which can help you to develop your own code. They consist of sensor- and actuator nodes.
Figure 1: Basic ROS Packages preinstalled in the car.
Updating the packages
To update to the newest version of the packages, download the debian package from: modelcar-basic-packages.deb
Copy the file to the model car and install it with:
$ dpkg -i modelcar-basic-packages.deb
Make sure in the .bashrc you are sourcing the correct setup.bash file (any catkin workspace in the /root/ directory has to source it before the first build):
source /opt/ros/modelcar/catkin_ws/install/setup.bash
The purpose of the packages should be apparent from their names. In the next sections we review each one of them.
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Rplidar_ros
rplidarNode is a driver for RPLIDAR. It reads RPLIDAR raw scan result using RPLIDAR's SDK and converts them to ROSLaserScan messages.
Published Topics
scan (sensor_msgs/LaserScan) it publishes scan topic from the laser
Services
stop_motor(std_srvs/Empty)
start_motor (std_srvs/Empty)
Parameters
serial_port (string,default: /dev/ttyLidar) serial port name used in your system.
serial_baudrate (int, default: 115200) serial port baud rate.
frame_id (string, default: laser) frame ID for the device
inverted (bool, default: false) indicates if the LIDAR is mounted inverted.
angle_compensate (bool, default: true) indicates if the driver needs to do angle compensation.
Device Settings
Once you have changed the USB port remap, you can change the launch file with the serial_port value.
<param name="serial_port" type="string" value="/dev/ttyLidar"/>
Launch File Examples
Start a rplidarNode and view the scan result in using “rostopic echo scan”.
$ roslaunch rplidar_ros rplidar.launch
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Serial
Serial is a cross-platform, simple to use library for using serial ports on computers. This library provides a C++, object oriented interface for interacting with RS-232 like devices on Linux and Windows.
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send_steering_light_speed
send_steering_light_speed Node sends desired steering angle and light and speed commands through serial port to Arduino. It reads the desired steering angle in integer and convert to string message.
It sends also specified strings through the serial port to the Arduino board in order to turn the lights on/off.
string Light
____________________________________________
le Blinking yellow left
ri Blinking yellow right
stop Turn on the three red tail lights (braking)
pa Turn on the two red back lights, and two white front lights
ta Turn on the two red back lights, and two white front lights
re Turn on the white lights at the back for going backwards.
fr Turn on the two white headlights for driving at night
diL Turnoff the lights
Subscribed Topics
manual_control/steering (std_msgs/Int16) .
manual_control/lights (std_msgs/String)
manual_control/speed (std_msgs/Int16)
manual_control/stop_start (std_msgs/Int16)
Parameters
serial_port (string,default: /dev/ttyArduino) serial port name used in your system.
serial_baudrate (int, default: 115200) serial port baud rate.
Device Settings
Once you have changed the USB port remap, you can change the launch file about the serial_port value and baud rate.
Launch File Examples
Start a steering node and change the car’s steering angle.
$ roslaunch send_steering_light_speed servo_light_odroid.launch
$ rostopic pub -r 1 /manual_control/steering std_msgs/Int16 '{data: 90}'
$ rostopic pub -r 1 /manual_control/speed std_msgs/Int16 '{data: 500}'
$ rostopic pub -r 1 /manual_control/lights std_msgs/String '{data: le}'
resolution of servo motor=?! resolution of speed motor=?
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head_twist_revolutions
This node used to read the yaw angle, delta_time between ticks of encoder, encoder counters through the serial port from Arduino and publish yaw angle, motor speed (rad/s) and motor revolutions.
Published Topics
model_car/yaw (std_msgs/Float32)
model_car/revolutions (std_msgs/Float32)
model_car/twist (geometry_msgs/Twist)
Parameters
serial_port (string,default: /dev/ttyArduino)
serial_baudrate (int, default: 115200)
Launch File Examples
Start a head_twist_revolutions node and subscribe to the yaw angle,twist,revolutions of the model car.
$ roslaunch head_twist_revolutions head_twist_revolutions_odroid.launch
$ rostopic echo /model_car/yaw
$ rostopic echo /model_car/twist
$ rostopic echo /model_car/revolutions
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usb_cam
The usb_cam_node interfaces with standard USB cameras (e.g. the fish-eye camera) using libusb_cam and publishes images as sensor_msgs::Image. Uses the image_transport library to allow compressed image transport.
Publisher Topics
usb_cam/image_raw
Parameters
The camera name. This must match the name in the camera calibration
~camera_name (string, default: head_camera)
You should use camera_calibration package of ROS to calibrate the camera for further use.
Launch File Examples
Start usb_cam node to publish the image_raw topic.
$ roslaunch usb_cam usb_cam-test.launch
Hints:
to use the usb_cam ,
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Put the usb_cam package inside your workspace
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Delete the remapping line in the launch file (usb_cam/launch/usb_cam-test.launch) :
<remap from="usb_cam/image_raw" to="app/camera/rgb/image_raw" /> -
Find the port of USB (/dev/video?) of fish eye camera and modify the launch file based on:
<param name="video_device" value="/dev/usb_cam" />
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Realsense_camera
This package contains launch files for using the Intel RealSense camera device.
Launch File Examples
Start realsense_sr300 node to start the intel sr300 camera.
$ roslaunch realsense_camera sr300_nodelet_rgbd_app.launch
make sure there is not any nodelet with the same name running on the odroid, to stop the nodelet you can find the id of nodelet using "pgrep nodelet" and then kill it "pkill nodelet" in the model car.
$ pkill nodelet
$ pkill rosmaster