A novel classification of planar four-bar linkages and its application to the mechanical analysis of animal systems

Abstract

A novel classification of planar four-bar linkages is presented based on the systematical variation of one, two or three bar lengths and studying the transmission properties (input-output curves) of the linkages. This classification is better suited to the study of biological systems than the classical Grashof-classification used in engineering as it considers the change of structural elements, in evolution for example, instead of evaluating the possibilities for the rotation of a particular bar. The mechanical features of a wide range of planar linkages in vertebrates, described by various authors, have been included in this classification. Examples are: skull-levation and jaw-protrusion mechanisms in fishes, reptiles and birds, the coral crushing apparatus of parrotfishes, and catapult-mechanisms in feeding pipefishes. Four-bar replacement mechanisms, e.g., crank-slider mechanisms in feeding systems of fishes and cam-mechanisms in mammalian limb-joints, and more complex linkages than four-bar ones, e.g., six-bar linkages and interconnected four-bar linkages in fish feeding mechanisms are also discussed. In this way, an overview is obtained of the applicability of planar linkage theory in animal mechanics to mechanical functioning and the effect of possible variations of bar lengths and working ranges in evolution. Four-bar system analysis often provides a rigorous method of simplifying the study of complex biological mechanisms. The acceptable width-range of necessary and undesired hysteresis ('play') in biological linkages is also discussed.

Ligament versus bone cell identity in the zebrafish hyoid skeleton is regulated by mef2ca

“…Here, we report the new discovery that a major aspect of mispatterning in mef2ca b1086 mutants is a fate switch from ligament to bone. The newly identified ligament in question, which we named the operculohyoid, links the opercle bone to the ceratohyal cartilage, similar to the function performed in most adult teleosts by the interopercular bone as a component of the opercular four-bar lever system (Anker, 1974;Muller, 1996). This ligament has thus far escaped detection in any fish, probably owing to the absence of zebrafish ligament markers, until recently (Chen and Galloway, 2014).…”

Biomechanics of a convergently derived prey-processing mechanism in fishes: evidence from comparative tongue bite apparatus morphology and raking kinematics

“…Flaring clearly diverges from the 2-D motions that can be explained by conventional engineering four-bar linkage theory. However, the discrepancies in output link length required to alter basihyal motion from curvilinear (Sanford and Wainwright, 2002) to ellipsoid are theoretically restricted to the freedom of motion around the interhyal, which connects the ceratohyal output link to the suspensorial fixed link (De Visser and Barel, 1996;Muller, 1996).…”

Mechanics of snout expansion in suction feeding seahorses: musculoskeletal force transmission

“…Muller, 1987;Muller, 1996;Westneat, 1994;Waltzek and Wainwright, 2003;Roos et al, 2009a;Ferry-Graham and Konow, 2010), relatively little is known about the mechanics of lateral expansion. Lateral expansion occurs by abduction of the bony elements covering the sides of the head in actinopterygian fish.…”