Study of Mechanisms with Allowance for Friction Forces in Kinematic Pairs

Friction forces emerge in kinematic pairs of mechanisms; in many cases, these forces significantly affect the movement of the links of the mechanisms and should be taken into account in force calculations. Introduction of friction forces leads to an increase in the number of unknown components of the reactions of the pair while the number of kinetostatic equations does not increase. In order for the problem of force analysis to remain solvable, it is necessary to introduce additional conditions, the number of which is equal to the number of additional unknowns. Usually, additional conditions are selected allowing for the design features of the elements of kinematic pairs, which allow making some a priori assumptions about the nature of the normal forces distribution. The paper considers the formation of such conditions, i.e., essentially, the examples of constructing computational models of kinematic pairs with friction. A force calculation of the mechanism with allowance for friction is shown, which is reduced to the joint solution of the kinetostatic equations and additional equations describing the models of kinematic pairs. It is also shown that for the given kinematic parameters of motion, the system of force calculation equations has one solution, several solutions, or no solution at all.