Design Requirements of Planar Four-Bar Linkages

Abstract

Generally, a mechanism is a device that transforms motion and force, while a machine typically contains one or more mechanisms that are designed to provide significant forces and transmit significant power [1]. A mechanical system, or machine, generally consists of a power source and a mechanism for the controlled use of this power [2]. Mechanical design is a complex process, requiring many skills. It is an iterative process with many interactive phases [3]. In general, mechanical design often starts from mechanism design. In the design process, there is no clear-cut dividing line between mechanisms and machines. A number of links connected in sequence via joints form a kinematic chain. It is called a mechanism when the kinematic chain has definite motion under one or more actuations. Among the mechanisms, planar linkages play a very important role in mechanical engineering. Simply the best has become the nowadays design principle. Planar four-bar linkages as the simplest closed-chain mechanism are widely used from mechanical engineering to civil engineering and aerospace engineering. This book therefore focuses on some special planar mechanisms which typically consist of a number of four-bar linkages and discusses the position design, kinematic synthesis, workspace and singularity of planar parallel linkages, stiffness of the linkage structure, kinetostatics, and structural dynamics. Possible applications of these special planar linkages in mechanical engineering and civil engineering are illustrated via examples.