Modeling and simulation of elastic and friction forces in lubricated bearings for precise motion control

The study presents a dynamic model for the resistance forces to the rotation of a journal in a lubricated sleeve bearing at low speed. The resistance forces include the sliding friction as well as the presliding Dahl effect, namely, elastic force due to the compliance in the system before the force reaches the break-away magnitude when sliding initiates. Both the stiffness of the surface asperities and the elastic support of the bearing are considered for the presliding rotation of the journal. The model is based on the physical principles of hydrodynamic lubrication as well as the dynamics of the system. The model shows that the instantaneous friction is not only a function of the velocity at that instant, but also depends on the velocity history. The model predicts hysteresis-type friction curves for oscillating velocity, in agreement with previous experiments. The model may be useful to improve the precision of motion in feedback control systems with friction.