Optimal Compliant Design of a Planar Linkage for Decreasing the Undesirable Effects of Joint Clearance

In practice، clearances in the joints are inevitable due to tolerances and defects arising from design and manufacturing. It is well-known that in the presence of clearance at one joint، the linkage gains an additional uncontrollable degree of freedom which is the source of error. Moreover، these joints undergo wear and backlash، resulting in poor accuracy and repeatability، and so cannot be used in precision mechanisms. The model of continuous contact is used for clearance model. Therefore، joint clearance was modeled as a small link with the length equals to the clearance. In this paper، a method is proposed to alleviate the undesirable effects of joints clearances. This improvement implemented using compliant joints. The compliances are introduced locally in the form of flexural hinges at the two oscillating revolute joints of a four-bar crank-rocker linkage. pseudo-rigid body model is used for modeling the flexures. An optimum design of the flexural hinge for minimum objective function is deduced and used to modify the conventional mechanism. The PSO method is used for optimization process. An example is included in which we show that introduction of compliance will modify the dynamics performances of the linkage.