  In this paper a method of controlling nonholonomic systems within the
port-Hamiltonian (pH) framework is presented. It is well known that
nonholonomic systems can be represented as pH systems without Lagrange
multipliers by considering a reduced momentum space. Here, we revisit the
modelling of these systems for the purpose of identifying the role that
physical damping plays. Using this representation, a geometric structure
generalising the well known chained form is identified as \textit{chained
structure}. A discontinuous control law is then proposed for pH systems with
chained structure such that the configuration of the system asymptotically
approaches the origin. The proposed control law is robust against the damping
and inertial of the open-loop system. The results are then demonstrated
numerically on a car-like vehicle.
