How to drive Clearpath Jackal via ROS2 messages in Isaac Sim?

[longylian]

Hi everyone,

According to ROS 2 Tutorials: 7.2.2. Driving TurtleBot via ROS2 messages, I can drive turtlebot3 via ROS2 topic.

NVIDIA Isaac Sim supports serval Differential Drive Robot, such as carter, JetBot and Clearpath. I can control cater_v2_3 and Jetbot easily with the help of the above tutorial, which these differential drive chassis have two drive-wheel.

But how can I drive a differential drive chassis with four drive-wheel, such as Clearpath Jackal? I try to add two Articulator controllers in Action Graph, one of them control the front two wheels, the other control the back two wheels, is this the right way to do it?

[rchadha]

hi @longylian , can you try using 2 differential controllers for the front and rear wheels which are then connected to a single articulation controller for the robot? (just 1 articulation controller and 2 differential controllers). This might not be the best solution but should help you get started

[longylian]

Hi @rchadha , I try 4 different methods, but each method has the same bug. I use carter_ v2_3 for comparison, given an angular velocity of 1.0 rad/s, Jackal rotates much slower than carter_v2_3.

My USD file is here:
carter_jackal_.zip (356.6 KB)

Robot	Wheel Radius (m)	Wheel Separation (m)
carter_v2_3	0.14	0.4132
Jackal	0.095	0.37558

1. one differential controller + one articulation controller
   

   
   
   

2. one differential controller + two articulation controller
   

   
   
   

3. two differential controller + one articulation controller
   

   
   
   

4. two differential controller + two articulation controller
   

   
   
   

I found some links related to my issuse:

• Articulation of a 4-wheeled robot using ROS2
• Wheel robot with 4 joints can't move by Differential Controller using Action Graph and ROS

[longylian]

Hi all, I had solved this.

My USD file is here:
carter_jackal.zip (84.3 KB)

Robot	Wheel Radius (m)	Wheel Separation (m)
carter_v2_3	0.14	0.4132
Jackal	0.098	0.37558

I use 1 differential controller and 2 articulation controllers. In Jackal differential controller, I set wheelDistance to 4.2 rather than 0.37558.

According to section “2.1. Kinematical Analogy of Skid-Steering with Differential Drive” on paper “Analysis and Experimental Kinematics of a Skid-Steering Wheeled Robot Based on a Laser Scanner Sensor”, SSMR is equivalent to ideal differential drive robot with longger wheelDistance than actual config.

Control Jackal and carter_v2_3 with linear v=0 and angular w=1.0 rad/s:

Control Jackal and carter_v2_3 with linear v=0.5 m/s and angular w=0.5 rad/s: