Dynamic behavior analysis of four-bar linkage mechanisms with joints' clearance

In the dynamic behavior analysis of different mechanisms, in order to simplify the investigations, some of the involved parameters are usually ignored. As a result, there is a notable discrepancy between the actual behavior and the results obtained via numerical simulations. One such parameter is the phenomenon of joints' clearance which is normally the result of the allowed tolerances during manufacturing and assembly, and has attracted considerable attention in recent years. Presence of clearance in joints results in additional degrees of freedom in the system, and the mechanism experiences sudden impacts causing undesirable vibrations, lower accuracy, and chaotic dynamic behavior. Therefore, through analysis of mechanisms taking the phenomenon of joints' clearance into consideration, more accurate information can be obtained allowing the design of superior mechanisms. The majority of research works in this field revolves around dynamic behavior of crank-slider mechanism. However, in the current study, rigid four-bar mechanism is analyzed which has been less addressed. Moreover, the contact force model of Lankarani-Nikravesh was used in order to obtain more accurate results despite additional complexities introduced by the model. Nonlinear dynamics of system are analyzed, using Poincare maps Also, the effect of crank velocity and clearance size was separately investigated in order to demonstrate the importance of these parameters on system behavior.