Design of Spherical 4R Mechanisms: Function Generation for the Entire Motion Cycle

[+] Author and Article Information
K. Farhang, Y. S. Zargar

Department of Mechanical Engineering, Southern Illinois University at Carbondale, Carbondale, IL 62901

J. Mech. Des 121(4), 521-528 (Dec 01, 1999) (8 pages) doi:10.1115/1.2829492 History: Received March 01, 1998; Revised August 01, 1999; Online December 11, 2007


Spherical 4R mechanisms are studied for which the crank is relatively smaller than the remaining links. The theory of small-crank mechanisms is applied to obtain approximate descriptions for the follower angular displacement in terms of the input crank angle. The follower angle is presumed to comprise a mean and a perturbational motion. This results in an approximate expression in which the follower displacement is given as a linear combination of simple harmonic functions of the first and second harmonics of the crank angle. The approximate equations are utilized for synthesis of spherical 4R mechanisms for function generation. In contrast to the conventional design procedures, the use of the approximate equations allows the synthesis of spherical mechanisms in which a prescribed function is satisfied for the entire motion of the mechanism. In addition to design examples, sample error charts are provided to assist the designer in ascertaining feasible ranges for design and corresponding orders of error.

Copyright © 1999 by The American Society of Mechanical Engineers
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