Select this link, Four-bar linkages, for a Geogebra book that illustrates linkages ranging from a lever to a crank-rocker that open a door. This includes the construction of a four-bar linkage that coordinates the open and closed positions with specific input crank angles, called a four-bar function generator. The iPad application, MechGen FG, computes four-bar function generators for five coordinated values of the input and output cranks.
Animations of linkage movement.
Mark Plecnik has applied his research on the design of six-bar linkage function generators to the challenge of a long travel independent suspension for an off-road vehicle. UCI race car engineering students built a 1/5 scale model of his latest design and compared its performance to his calculated design. For more detail see his video:
Please select this link to open the Geogebra Book containing constructions of a number of interesting linkages. This is an introduction to the useful movement available with articulated systems.
Mark Plecnik shows that six-bar function generators can be used to drive a serial chain and produce a realistic wing flapping gait. Using trajectories obtained through video analysis by researchers Bret W. Tobalske and Kenneth P. Dial, “Flight Kinematics of Black-billed Magpies and Pigeons Over A Wide Range of Speeds,” Mark constructed functions for the joints of the serial chain, designed the function generators, and animated the results. Select this link for more information on Mark Plecnik and his work.
Researchers at Disney Research Zurich provide yet an other design system with the goal of moving digital character design into physical form. This work by Vittorio Megaro (ETH Zurich) and Bernhard Thomaszewski (Disney Research Zürich) and their colleagues can be viewed as two-position synthesis of four-bar “joints” that connect bodies in a serial chain, which are then driven by a sequence of four-bar function generators. They 3D print the result to obtain a cartoon character that moves with the rotation of a crank. Select this link for more information.
Kaustubh Sonawale and Yang Liu worked together on this design study for a micro-mechanical motion amplifier. It is an interconnected set of three eight-bar linkages.
This animation was prepared by Yang Liu for a linkage designed by Kaustubh Sonawale. The eight-bar linkage guides the platform in the approximation to rectilinear motion.
[evp_embed_video url=”http://cast.oit.uci.edu/jmmccart/Rectilinear-Sixbar.mp4″ width=”500″ height=”350″]
This is an animation of a Watt I six-bar linkage with a translating link that does not rotate (select the video to begin the animation). This is obtained using GeoGebra to execute a construction described by E. A. Dijksman in his book Motion Geometry of Mechanisms.
Disney Research guides two degree-of-freedom open chains using the coupler curve of a geared five-bar linkage to obtain geared seven-bar and nine-bar linkages, which they use to move the front and rear legs of their Cyber Tiger. By connecting the driving gears of the four legs, they obtain a one degree-of-freedom system that animates the Cyber Tiger.
The computational design system uses an optimization routine to adjust the coupler curve of the five-bar linkage to approximate a given curve in order to guide the system in a desired movement. The results are terrific, and look a lot like the mechanical toys of the past. Select this link for more information.