With the release of v0.25, it is now possible to attach robots to dynamic rigid bodies (such as physics-driven vehicles). All you need to do is add the Robot Grounded Link component to the base link for the robot.
The example above shows a SO-101 robotic arm attached to the chassis of a wheeled robot. Since the first link of the robot is jointed to the chassis (i.e. the chassis is the base for the first joint), we added a Robot Grounded Link component to the chassis. This is all the information that the robot controller needs in order to solve the inverse kinematics for the robotic arm.