Most of the wheeled robots in ROS use move_base to move the robot. move_base geometry model is based on differential drive which basically transforms a velocity command (twist message) into a command for rotating the left and the right wheels at a different speed which enable the car to turn into the right or left or goes straight.
I was looking for a car robot model with such geometry so I can test it in gazebo and ROS. I didn't find what I was looking for but I found several packages and with some adaptations, I managed to build and control a car with Ackermann steering geometry with a joystick.
As you can see in the following graph, I'm reading my joystick data and translate them into twist messages (The topic is cmd_vel). Then I translate these messages into Ackermann messages (The topic is ackermann_cmd).
Click to enlarge the image.
The robot in the video downloaded from here with some modifications for this work.