Connecting the Physical Twin with a Digital Shadow

In this example, we demonstrate how the PiCar-X can be connected to a digital shadow. For this purpose, we created a special Docker container that contains a ROS node, which does not send any commands to the physical twin.

Start the Digital Shadow

We assume at this point that the digital shadow runs on a X64 Linux system (e.g. a server).

# Build and execute the Docker Containers
docker compose -f docker-compose-core.yml build 
docker compose -f docker-compose-ds.yml build 
docker compose -f docker-compose-ds.yml up

Start the Phyiscal Twin

• arm32v7 (RPi3)
• arm64v8 (RPi4)

# First copy all content to the RaspberryPi4
scp -r ./ <user>@<picarx-ip>:~/

# Login to the RaspberryPi via ssh
ssh <user>@<picarx-ip>

# Build and execute the Docker Containers
TAG=latest ARCH=arm32v7 docker compose -f docker-compose-core.yml build 
TAG=latest ARCH=arm32v7 docker compose -f docker-compose-pt.yml build 
TAG=latest ARCH=arm32v7 docker compose -f docker-compose-pt.yml up  

# First copy all content to the RaspberryPi4
scp -r ./ <user>@<picarx-ip>:~/

# Login to the RaspberryPi via ssh
ssh <user>@<picarx-ip>

# Build and execute the Docker Containers
TAG=latest ARCH=arm64v8 docker compose -f docker-compose-core.yml build 
TAG=latest ARCH=arm64v8 docker compose -f docker-compose-pt.yml build 
TAG=latest ARCH=arm64v8 docker compose -f docker-compose-pt.yml up  

Execute Commands on the Physical Twin

# Connect to the RaspberryPi
ssh <user>@<picarx-ip>

# SWITCH INTO THE CONTAINER
docker exec -it picar-x-ackermann_skill-pt-1 /bin/bash

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

# PUBLISH A MESSAGE TO TURN RIGHT WITH 50 percent motor speed
rostopic pub /picarx/drive/command picarx_msgs/Drive "{speed: 50, angle: 20}"