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When we use ROS Navigation Stack for Path Planning, then in which launch file we insert the kinematic model mathematical equations??

asked 2021-07-15 01:12:47 -0500

SAURABH gravatar image

Hi everyone, Actually I am very new to ROS. I am using Ubuntu 18.04 and ROS Melodic. I am working on path planning of a three wheeled omnidirectional mobile robot. For that I am first learning the path planning of TurtleBot3 robot from ROBOTIS e-Manual and The Construct series of ROS NAVIGATION IN 5 DAYS.

So when we use ROS Navigation Stack for path planning...I am not able to understand in which launch file i have to insert the kinematic model equations of the robot.

Can anyone give me some clarification??

Thanks in advance!!

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answered 2021-07-15 19:55:55 -0500

Always keep tuned in the package wiki ( http://wiki.ros.org/navigation )

ROS Navigation - MoveBase image description

As you can see the only thing that ros navigation is taking care of is what is inside the white box. The velocities commands are exposed as /cmd_vel | geometry_msgs/Twist. Twist has the following struct: Twist

Usually, a wheeled robot just cares about linear.x and angular.z, so YOU should subscribe to this topic and create your personal kinematic model.

However, there are some already builds alternatives ( Differential Driver )

To create your own method you can use Hardware Interface, but this is your choice.

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First of all thank you very much for your valuable response...

SAURABH gravatar image SAURABH  ( 2021-07-16 08:58:09 -0500 )edit

Yes, I have idea about Twist message and also i have the kinematic model for my omni-wheeled robot.

SAURABH gravatar image SAURABH  ( 2021-07-16 08:59:40 -0500 )edit

To convert the Twist message (velocity command) into corresponding wheel velocities of the robot. i think we have to use kinematic model.

SAURABH gravatar image SAURABH  ( 2021-07-16 09:01:44 -0500 )edit

But the main problem i am facing is that i am not able to get in which launch file (either in teleop or in other navigation file.......or in ros_planar_move plugin) i have to insert these kinematic equations??

SAURABH gravatar image SAURABH  ( 2021-07-16 09:04:40 -0500 )edit

May be that's the reason my omni-wheeled robot slides in Gazebo as well as in RViz during teleop (the base velocities of the robot are not transferred to the wheels......i haven't inserted the kinematic model yet because i have no idea where to put these equations code.)

SAURABH gravatar image SAURABH  ( 2021-07-16 09:14:18 -0500 )edit

And also can you let me know the TurtleBot3 file name in which they have used their kinematic model equations code?

Thanks in advance!!

SAURABH gravatar image SAURABH  ( 2021-07-16 09:16:18 -0500 )edit

And I have one issue that....i am not able to send all the content above as a single message by selecting add comment tab.

SAURABH gravatar image SAURABH  ( 2021-07-16 09:21:40 -0500 )edit

Okk....now I got the idea that kinematic equations are inbuilt in the controller plugin. Actually I am using 3 omni-wheeled robot platform for path planning. The available controller plugin is planar_move_plugin for such robots. This plugin is not working properly in my case so I want to insert my kinematic relations in plugin but in this plugin (.cpp file) there is no such code related to kinematics which I can replace with my kinematics. Kindly anyone suggest me some idea about custom plugin for 3 omni-wheeled robot platform??

SAURABH gravatar image SAURABH  ( 2021-07-25 02:42:37 -0500 )edit

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Asked: 2021-07-15 01:12:47 -0500

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Last updated: Jul 15 '21