On certain methods of considering dry friction in dynamic analysis of planar open kinematic chains

The paper presents two different ways in which dry friction is taken into account in dynamic analysis of multibody systems considered as planar open kinematic chains with rotary joints (kinematic pairs). In both cases there are different methods of calculating reactions in kinematic pairs. The first method, based on constraint equations, is used mainly in dynamic analysis of systems with flexible links when the rigid finite element method is applied. Another method is used for analysis of chains with rigid links when the equations of motion are formulated using transformation matrices in accordance with the Denavit-IIartenberg notation. In this case unknown quantities are calculated from equations of dynamic equilibrium of a particular link. Both methods enable us to take into account the complex model of dry friction in pairs, i.e., consideration of not only kinetic friction (Coulomb friction) but also stiction phases. Numerical results obtained for both methods, in the case of analysis of the chain simplified with rigid links, are compared and good correlation between them proves the correctness of the methods used.