  The Chaplygin sleigh is a classic example of a nonholonomically constrained
mechanical system. The sleigh's motion always converges to a straight line
whose slope is entirely determined by the initial configuration and velocity of
the sleigh. We consider the motion of a modified Chaplygin sleigh that contains
a passive internal rotor. We show that the presence of even a rotor with small
inertia modifies motion of the sleigh dramatically. A generic trajectory of the
sleigh in a reduced velocity space exhibits two distinct transient phases
before converging to a chaotic attractor. We demonstrate this through numerics.
In recent work the dynamics of the Chaplygin sleigh have also been shown to be
similar to that of a fish like body in an inviscid fluid. The influence of a
passive degree of freedom on the motion of the Chaplygin sleigh points to
several possible applications in controlling the motion of the nonholonomically
constrained terrestrial and aquatic robots.
