Analysis of a four-bar linkage mechanism in its classical and compliant form - a comparison

Abstract

A four-bar linkage mechanism to accomplish different tasks. Those mechanisms is used in a vast number of application in different fields accomplish different tasks. Those mechanisms can have some theoretical and practical limitations, de-pending on their applications. From a theoretical standpoint, four-bar linkages mechanisms are modelled with rigid bodies with rotary joints, and, from a practi-cal standpoint, those joints require additional maintenance during operation and lubrication. On the other hand, compliant mechanisms do not have joints in a classical sense but the relative movement between linkages is accomplished through the deformation. Certain segments of the mechanism are thinned to achieve relatively localized large deformation, which will allow movement be-tween stiffer segments (linkages) of the mechanism. Compliant mechanisms have several advantages and disadvantages compared to classical mechanisms. Those mechanisms are essentially one part that doesn't require any lubrication and there is also no backslash between movable parts. Neverless, due to the mechanism de-sign principles, the strength of the overall structure and movement range can be very limited. Besides basic parametres, in the design process of complaint mech-anisms, the dimensions type of its “joints” has sn interesting part of overall per-formance. The stiffness of theese joints and their size will cause the relative movement of the rotary axis between linkages. The variable position of the rotary axis between adjacent linkages gives one more degree of freedom in the design process. This phenomenon opens up possibilities for fine-tuning, especially in cases where a classical mechanism is used as a design template for compliant mechanisms. An example of this process is a classical mechanism that produces approximately straight-line motion where the transition to a compliant mechanism can further improve straightness of its trajectory.