# How to find kinematics of a system with 2 differential drives attached together?

I have a system like shown in the diagram where 2 robots having differential drive are physically constrained together. Traditionally for a single robot, we find the Instantaneous center of curvature (ICC) by equating the “omega” for both wheels. That would work since there are 2 equations (the relationship between the wheel velocities and angular velocity) and 2 unknowns (the distance of ICC from the center of the wheels and the angular velocity). However, in my system, there will be 4 equations and 2 unknowns. So should I solve it as an over-determined system? Or should I only consider the extreme cases ie. left most wheel speed for the left robot and rightmost wheel speed for the right robot?

@Nightph0emnox Welcome to the RobotShop Community. Your last hypothesis seems correct. If there’s no slipping of the outer wheels, they alone can be used to determine everything, including the rpm of the two wheels in the center.