Abstract: This work presents a dynamic model a of a mobile robot, that can be used in order to determine the robot trajectory and the behaviour of some dynamic entities during the motion, as well as a basis to implement a control system. The mobile robot is modeled as a single rigid body moving in a three-dimensional space. This avoids the excessive complexity of a multi-body approach; however, the proposed model is more accurate than many single-body dynamic models found in the literature. The proposed model is based on Newton's and Euler's dynamic equations, and the forces and torques appearing in the equations are due to the friction acting at the robot wheels. Important features of the model are its modularity and its flexibility, as it can be easily adapted to whatever type of mobile robot with more than two wheels. The model has been tested through simulation in the Matlab-Simulink environment; the most significant results are presented.