  A disturbance decoupling problem for a $n$-link chain pendulum on a cart is
considered. A model of the cart developed in a coordinate-free framework and
the linearized equations of this system are considered from [1]. It is shown
that it is possible to design a suitable state feedback such that the angular
position or velocity of the $n^{th}$-link can always be decoupled from the
disturbance coming at the cart.
