The curved trajectory along which the Zumo Robot moves can be defined by the angle 'omega' at which the Zumo Robot is turning at an instant and the velocity 'v' at which the robot is moving forward.
Using simple kinematic equations, the mathematical relation is given by the following equations:
A subsystem is a collection of Simulink blocks and is a neat way to organize blocks for complex models. It is the block diagram equivalent of writing functions for your code.
The 'model command conversion' subsystem implements the math we just saw above in Simulink. To look at the implementation, double click on the subsystem block.