Differential-drive is a control mechanism that is being used in most situations requiring control of navigating robots, especially for indoor applications. For beginners as well, this is considered the best control mechanism to get started with robots. Most indoor navigating robots used in industries and homes use this very mechanism.

The concept of this mechanism is to use two separately driven motors coupled with the wheels of the robot, separated by a distance and placed on a fixed common horizontal axis. The base also includes one or multiple caster wheels or roller-ball wheels attached to it to maintain equilibrium.

Here is how it looks:

In the diagram, you can see two different configurations of differential-drive robots. The one on the left has two casters, while the other has just one. These two are one of the most commonly used differential-drive system configurations used. Both of them have different kinematics during navigation. If you want to look into...