ISAAC SIM: Stereo camera on a differential drive

 After spending some time online, I found a differential drive robot that comes with a preinstalled stereo camera and a 2D lidar. I do not wish to use the 2D lidar, but I will be using the stereo camera. 

Personal rant: Working with Isaac-sim is a test of patience. Have to wait after every other mouse click. Many times, I gave up on the idea of using Isaac-sim because of this reason. 

Alright, lets load up an environment (I used the warehouse) and add a jackal robot (Left Bottom: Isaac Sim Assets --> Robots --> Clearpath --> Jackal). 

Environment : Warehouse and Jackal Robot in Assets 

To control this robot, we will need a differential controller (Tools --> Robotics --> OmniGraph Controllers --> Differential Controller). Select the jackal robot in "Robot Prim" selection and insert values for wheel radius and wheel distance as (0.098, 4.2). These values are picked as per suggestion by a user in the nvidia forum. Don't forget to click on the checkbox for keyboard control.



Now we will modify the Action graph and add one more Articulation Unit. Open the Action Graph panel from menu (Window --> Graph Editors --> Action graph). Search for articulation controller in the search bar, and drag drop it on action graph panel. Now connect the "tick" signal generated by the On_Playback_Tick node to "exec in" and connect the "velocity command output" of differential_controller node to the "velocity_command" input of articulation_controller node.



Now, the two articulation units are to be configured to control the front wheel pair and the rear wheel pairs individually. This might seem weird but that's how it is. This setting is to be specified in the "Inputs" panel for the articulation controller node (see picture)


Also, at this point we can "deactivate" the 2D lidar from the jackal by selecting the appropriate component in Stage panel. If you wish to use the 2D lidar data, do not disable it.

Let's quickly summarise what was done. Sample environment loading, loading a jackal robot, adding differential controller, two articulation nodes, disabled the 2D lidar. To check if everything was set up correctly, press the play button and press "WSAD" keys to move the robot around. If the robot moves, all is set correctly.



In the next post I will describe how to receive the images from the left and right camera in ROS2.




























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