The PID controller is a time-tested and versatile controller in control theory. It has only three parameters - the proportional, integral and derivative gains and it guarantees robustness to constant disturbances in the system. For second order linear systems, the design of PID controller is straightforward and simple. All mechanical systems are intrinsically second order linear systems as according to Newton’s laws, the force vector is directly proportional to the acceleration vector which is the second derivative of position. However, since most mechanical systems evolve on non-linear spaces (smooth manifolds), there is no global coordinate system that is free of singularities. Also, when the equations of motions are written down in such local coordinates, they become highly non-linear and hence difficult to analyze. Therefore, the need for thinking geometrically regarding systems without any algebra of coordinates becomes imperative. In this talk, a geometric analog of the PID controller is presented for mechanical systems whose configuration spaces are Lie Groups and are subject to non-holonomic constraints on velocity. Applications abound as all mechanical systems are constrained interconnections of rigid bodies and the configuration space of a rigid body is a Lie group called the Special Euclidean Groupin three dimensions.