The kinematic model for skid-steering mobile robot (4 wheeled mobile robot) is
where state vector is $q = (x,y,\theta)$, and $\eta = (v,w)$ is the linear and angular velocity of the robot, and $x_{ICR}$ is the x-coordinate of ICR in local frame $oxy$. If this model is right thern:
In which cases, $x_{ICR}$ has a value (and how it can be calculated?) and in which has no value? What if the center of mass CoM is located at the geometric center of the robot and what if not?
Actually I have looked to the follwoing question but there were no answers to my questions. In Kinematics of a 4 wheeled differential drive robots
