Only the Digital Twin Prototype starts a simulation

If you want to develop new features for the PiCar-X and monitor the communication between the PiCar-X’s digital twin prototype and its digital twin, you can start the digital twin prototype and a reduced digital twin, which does not include the GAZEBO simulation. In that case, you can just use inside a Docker container of the digital twin the echo function provided by ROS on the topic you want to monitor.

Adjust the environment files

There are three environment files with relevant variables:

  • picarx.env (for the DTP)
  • picarx-dt.env
  • simulation.env
  • simulation-dt.env

Start the Digital Twin without GAZEBO 

# Build Docker Containers if not previously done
docker compose -f docker-compose-core.yml build 
docker compose -f docker-compose-dt.yml build 

# Start the DT
docker compose -f docker-compose-dt.yml up

Start the Digital Twin Prototype with GAZEBO 

# Start the DTP
docker compose -f docker-compose-dtp.yml up

To subscribe to any topic and get the content, you need to switch into one of the Docker containers:

docker exec -it picar-x-ackermann_skill-dt-1 /bin/bash

# INSIDE CONTAINER
source /root/catkin_ws/devel/picarx_ackermann_drive/setup.bash

There you can list all topics via:

rostopic list

Afterwards, you can subscribe to one of the topics, e.g. the status topic that receives all status changes from the PiCar-X:

rostopic echo /drive/status

# The console should now print all incoming messages with the corresponding status from the DTP.

Operate the Digital twin Prototype

To operate the digital twin prototype, you need to switch into the container:

docker exec -it picar-x-ackermann_skill-dtp-1 /bin/bash

# INSIDE CONTAINER
source /root/catkin_ws/devel/picarx_ackermann_drive/setup.bash

Inside the container you can publish a command message:

rostopic pub /picarx/drive/command picarx_msgs/Drive "{speed: 50, angle: 20}"

# The status should be sent automatically to the DT and the DT prints all incoming messages.