On computing flat outputs through Goursat normal form

This paper is devoted to computation of flat outputs by means of the Goursat normal form of the Pfaffian system associated to any control system in state space form. The algorithm explained here consists in three steps: i) Transformation of the system into its Pfaffian equivalent. ii) Computation of the Goursat normal form for the Pfaffian system. iii) Rewriting of the state space equations in the new variables. At this stage, a feedback law simplifies the equations and, therefore, the flat outputs can be easily computed. As an example, the algorithm is applied to a system consisting in a car with expanding wheels. Point to point trajectories are obtained thanks to the property of differential flatness. The paper also includes a control law that minimizes errors in the initial conditions.