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.
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.
Training people to diffuse landmines and other live ordnance left behind in conflict areas has always been a difficult thing. Successfully training Explosive Ordnance Disposal (EOD) Technicians requires hands-on education that gives the technician a true understanding of how a triggering mechanism inside live ordnance actually functions. For this reason, this kind of education requires effective training aids. The traditional training aids–either replicas or inert ordnance–are fragile, difficult to make, too intricate to be understood fully, hard to obtain in the case of inert ordnance, and impossible to ship internationally. Allen Tan from Golden West Humanitarian Foundation in collaboration with Asst. Professor Gim Song Soh and his students at Singapore University of Technology and Design have come up with an innovative solution to the problems this type of education presents.
They have created training aids that are engineered for a better understanding of how ordnance trigger mechanisms work. The plastic training aids display exact replicas of trigger mechanisms in cross-section, which gives the future ordnance disposal technician a better view of the kinds of mechanisms they will find in a real mine field. The AOTM devices are also resilient enough for classroom teaching.
How are these devices delivered to the various regions around the world where they are needed? They’re not. They’re 3-D printed. This innovation not only defeats the impossibility of shipping this kind of item all over the world, it also centralizes the construction of the devices in the region where they will be used. Countries benefit from this development of “sustainable indigenous assets capable of dealing with these issues as they are discovered” rather than putting the training in the hands of a third party (quote from Advanced Ordnance Training Materials by Allen Tan). It is a more sustainable way to run this kind of program.
Better training materials and affordable ways of providing them will lead directly to more effective—and safer–ordnance disposal programs around the world. The work that Professor Soh and his students at Singapore University of Technology and Design are doing with advanced ordnance teaching materials combines design innovation, active learning practice, and a forward-thinking embrace of 3D printing.
This animation prepared by Prof. Soh and his students illustrates the components of the SOTS-M2A1 trigger mechanism.
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 is a design concept for a rectilinear eight-bar suspension. It does not manage body roll but it does provide compact large travel.
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.
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.