Feedback linearization is a systematic approach often applied to the dynamic model of mobile robots and ground vehicles. It transforms a nonlinear system into a (fully or partially) linear system, and then uses the well-known linear design techniques to complete the control design. This transformation divides the model dynamics into two parts: a) the external dynamics which is to be transformed into a linear system and b) the internal dynamics which becomes unobservable by the transformation. Nonholonomic systems have an internal dynamics with a dimension equal to the number of independent nonholonomic constraints. One of the main subjects in the vehicle’s motion control is trajectory tracking. To stabilize the vehicle around a trajectory, both external and internal dynamics of the system must be stable. Since feedback linearization only treats the external dynamics of the system, internal dynamics has to be examined separately.
In this paper, the internal dynamics of a four-wheel vehicle is investigated and it’s stability is analyzed. It is shown that the internal dynamics of the vehicle is stable when the vehicle is moving forward.