HOW TO CONMAND VEHICLE TO MOVE

[Tianyu Shi]

Firstly,I cannot launch the urdf model in rviz ,could you tell some steps ? Secondly.I want to write some code to let the vehicle to move in a circle or just go straight ,please tell me how to send this command to vehicle ! I am new to ROS ,Please help me!

[Alex Tyshka]

Hello Tianyu, If you haven't already checked out our setup guide, you can find it here. If you launch the joystick demo or dbw system and then launch Rviz from dbw_mkz_description, the vehicle model should come up. Regarding programming, a simple way to control the vehicle would be publishing to the "vehicle/cmd_vel" topic, which is a geometry_msgs/Twist message. In fact, controlling one of our vehicles is similar to controlling the turtle sim in the ROS Tutorials! A more extensive documentation of the ROS API can be found in the README.pdf of this repository. Best of luck and let us know if you have further questions!

[Tianyu Shi]

Thanks for your reply, I have looked through the ROS Tutorials, I think firstly we need to launch a node

rosrun turtlesim turtlesim_node

but since it's not turtlesim ,so which node in dbw_mkz should we launch? secondly , I think if we want our vehicle run in a circle we need to say:

rostopic pub -1 /vehicle/cmd_vel geometry_msgs/Twist -- '[2.0, 0.0, 0.0]' '[0.0, 0.0, 1.8]'

but I do not know how big a circle it will run,is it 2.0 represent 2m in reality? Finally ,if we want our vehicle to run at an ideal (commend)acceleration then run in a ideal(commend)deceleration how can I publish this two topic continuously,since in the tutorial we can only publish one topic one times. Your early reply will be very appretiated!

[Alex Tyshka]

Firstly, before diving in to our products I highly suggest you work on getting a better understanding of how ROS works. There's a lot of great documentation on the internet, especially on the ROS Wiki. That being said, for launching the node please follow the guide I linked in my first post for launching the drive by wire system. Regarding units for the twist message, they are meters per second and radians. This information and more can be found in the previously mentioned README.pdf file. Finally, for more complicated behavior you will need to write an actual program, not use the command line tools.