In this class, we study two basic robot forms that accomplish two very different kinds of jobs. Mobile robots typically have wheels, which they use to locomote on the ground. Manipulator arms are usually bolted to a fixed surface and have a serial chain linkage which can change shape, as well as a hand or end-effector for manipulating objects. Note that a manipulator arm can also be mounted on a mobile robot, giving rise to the problem of mobile manipulation.Mobile robots come with a variety of drive mechanisms. Wheels may be drive wheels or free spinning. They may have a fixed axle, a steered axle, or a free axle. A free-spinning, free-axle wheel is a caster. Since some drive mechanisms need only two wheels, a caster is added to maintain stability on a flat surface