Differential mechanisms are widely studied in literature, from a theoretical viewpoint and for applicative reasons. A differential mechanism is a mechanical system with one or more output motions resulting from the combination of different input motions acting on the same degree of freedom. In this work, we point the attention on planar differential systems (a monoaxis and a Cartesian device) composed by belts and pulleys. Particularly the Vernier effect is used to realize high-speed and highaccuracy devices with low-cost components. Simplified models of these two systems are presented to show the main kinematic and dynamic features. An advanced model is then realized for the Cartesian device with the aid of the Dymola software and simulation results are compared with the expected ones from the simplified model. The control of the system is realized with three PI systems (proportionalintegrative) optimized via an adaptive logic. Finally early experimental results are presented only for the monoaxis system
