Unified Mechanism Synthesis of Four-bar Linkage for Function Generation and Rigid Body Guidance using Block Model

Several synthesis methods, graphical, analytical and computer-aided technique, have been proposed for selecting and scaling mechanical devices. The objective is to guide a rigid body through a specified position, or to force a point on a linkage to trace out the desired trajectory curve, or to perform a specific input/output relationship. This paper is based on the function generation and rigid body guidance, although the proposed method can be applied to any of them. Extensive research has been given to the synthesis of mechanisms for the purpose of function generation based on candidate mechanism layout. However, in the initial design stage, the designer has to synthesize a combination of linkage topology and type of joints which may be best suited for a particular task. This problem may be solved by means of experience, intuition of designers. So, the systematic determination of the optimal topology and dimension of mechanisms is very important in the mechanism design process. In this paper, unified mechanism synthesis which covered the problem of type and dimensional synthesis of planar mechanisms with respect to the functional requirement of output motion is proposed. To perform the unified synthesis for function generation, a planar linkage is modeled as a set of size-variable three rigid blocks connected by zero-length translational springs with variable stiffness. The values of spring stiffness and size of rigid blocks yielding a desired functional requirement related to input motion are found by using an optimization method