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MechGen FG App Makes Design Calculations Easy

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The MechGen iPad App helps you design a link that connects an input crank to the coordinated rotation of an output crank. Locate the two cranks and define their input and output angles and let MechGen FG design linkages for you. The design data and an animation of your linkage is easily distributed by email.

The use of linkages for calculation dates back to Charles Babbage’s “difference machine” from the mid 19th century. One hundred years later, Svoboda designed mechanical computers to direct artillery by fitting the input-output properties of linkages to a desired function.  In 1954, Freudenstein used the newly developed digital computer to find a simple linkage that computed complex functions. This introduced computer-aided design by numerical solution of polynomial synthesis equations derived from linkage loop equations.

Today the design algorithms for six and eight bar function generators push the limits of computational ability.

MechGen FG helps the designer because it repeatedly makes routine calculations that would otherwise be very difficult, and it creates many candidate designs, which is where computational power comes into play.

mechgen design problem-trashcan-lid

An example design that the MechGen app will solve for you is that of a trashcan lid connected by a link to a foot pedal designed to open it. You want the lid to open 100 degrees so that it creates a large opening for you to put trash in it without the lid getting in the way of the entrance (because that is an annoying thing for people to deal with and this is a concern with this product) and being over 90 degrees will allow it to rest or stay open instead of falling back down and closing, but you also don’t want a person to have to move the pedal over too big a distance; you want the pedal to only move 20 degrees so it’s easy for a person to do.

This is a nice design problem.  How do you get a lid to swing 100 degrees when you move a pedal 20 degrees?  Well, you can start with the MechGen FG App.

mechgen-fg-design-app

Find out more on iTunes. This app is a collaboration of Kaustubh Sonawale and Jeffrey Glabe.

Shape Changing Linkage

Shape Changing Mechanisms Solve Design Problems

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A design problem that engineers frequently encounter is a curve that changes shape. For instance, take a spoiler on a high performance car. To get optimal performance, the downward force should be increased as the car takes a turn. An ideal way to achieve this is to allow the spoiler to change shape. This is no simple design task because an engineer wants the spoiler to remain a spoiler and do its job at every intermediary stage as it changes shape. To use another example, you don’t ever want a wing to stop being a wing. But you might want to enable a wing to change its shape during flight.

Professor Andrew Murray, Associate Professor Dave Myszka, and Dave Perkins (all of University of Dayton), along with Associate Professor Jim Schmiedeler (of Notre Dame) and the students at University of Dayton’s Design of Innovative Machines Lab (DIMLab) are working on new technology to tackle these problems. Their work focuses on the theory and design of “morphing or adaptive structures” that can essentially change shape and still perform their function “through a wider range of operating conditions.” Design applications of this research include wings, extrusion dies, deformable mirrors for adaptive optics systems, morphing architectural structures, active aperture antennas, and (to come back down to Earth for a moment), pasta makers.

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Shape-Changing Wing with Internal Structure

Die design is an interesting manufacturing application of this research. A die is used in a manufacturing process where melted plastic or other such material, like pasta dough, is forced through a die in order to “form a long part of uniform cross-section” like tubes, pipes, molding — and fusilli. Professor Murray and his colleagues and students have applied their research to designing a die that can change shape as material is fed through it, enabling manufacturers to create new innovative products at low cost compared to other currently available technology like molding.

For more information on this research, visit DIMLab.  See video demonstrations of this technology here.  For reference material, see Persinger, J., Shmeideler, J., Murray, A., 2009, “Synthesis of Planar Rigid-Body Mechanisms Approximating Shape Changes Defined by Closed Curves.”  The spoiler and compliant wing featured in the videos in this article were engineered by Seb Krut.

Demining Training Aids

3D Printed Demining Training Aids

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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.

aotm


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.

For more information please visit eodtrainingaids.com, Professor Gim Song Soh’s homepage, and an article written by Allen Tan.

This animation prepared by Prof. Soh and his students illustrates the components of the SOTS-M2A1 trigger mechanism.

Wearable Robotics Put Spring in Your Step

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Wearable electronics or “wearables” are seen as the next great wave of technology and commerce. Much of the popular talk about these kinds of products revolves around things like fitness trackers, augmented reality devices, and other machines you can wear that interact with, track, or add on to your experience with the world around you. Thomas Sugar, a professor at Arizona State University Polytechnic Campus and a wearable robotics expert works on a different kind of wearable.

Along with his colleagues and students, he has developed a new generation of powered prosthetic devices that can be used for rehabilitation and as prosthetics for amputees. He works on spring-based robots that enhance human mobility based on lightweight energy storing springs that allow for a more responsive and therefore more functional human gait. His devices make position control calculations 1,000 times per second to make the prosthetics as human as possible.

springactive-odyssey
Sugar starts from a “human being first” research perspective since his devices must be wearable and efficient. In his devices, spring power and motor power combine to create a powered system that gives prosthetic ankles the “push off” and “toe pick up” they need in order to mimic the function of human ankles.

His idea of a robotic tendon is much more efficient than a direct drive system, which would require more electricity and larger, more powerful motors.   In fact, his innovation uses half the required energy of a direct drive system powered prosthetic ankle.

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In a different device attached to the ankle Sugar uses able-bodied movement to harvest energy from walking. His company SpringActive developed a boot attachment with the military in mind that turns walking into back up power for batteries with negligible metabolic cost.

The real world and commercial applications for this kind of research are far reaching.   For more on Thomas Sugar’s and his colleagues’ work, visit SpringActive.com and http://innovation.asu.edu/

Singular Designs is now on-line

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MechGen 3

MechGen 3

Please see our Singular Designs web-site. We look forward to providing our MechGen synthesis software to simplify your linkage design process in SolidWorks. Also see Mechanism Generator.

21st Century Kinematics

Workshop on 21st Century Kinematics

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21st Century Kinematics

21st Century Kinematics

The NSF Workshop on 21st Century Kinematics at the 2012 ASME IDETC Conference in Chicago, IL on August 11-12, 2012 consisted of a series of presentations and a book of supporting material prepared by the workshop contributors.

The book is now available at amazon.com: 21st Century Kinematics–The 2012 NSF Workshop.

And here are the seven primary presentations given at the workshop.

  1. Computer-Aided Invention of Mechanisms and Robots. J. Michael McCarthy, Professor, University of California, Irvine.
  2. Mechanism Synthesis for Modeling Human Movement. Vincenzo Parenti-Castelli, Professor, University of Bologna.
  3. Algebraic Geometry and Kinematic Synthesis. Manfred Husty, Professor, University of Innsbruck.
  4. Kinematic Synthesis of Compliant Mechanisms. Larry Howell, Professor, Brigham Young University.
  5. Kinematics and Numerical Algebraic Geometry. Charles Wampler, Technical Fellow, General Motors Research and Development.
  6. Kinematic Analysis of Cable Robotic Systems. Vijay Kumar, Professor, University of Pennsylvania.
  7. Protein Kinematics. Kazem Kazerounian, Professor, University of Connecticut.

Colleagues joined in with two additional presentations:

Many thanks to the contributors and the attendees for an outstanding workshop.

Update: The presentation links have been fixed.

Mechanism and Robotics Notes

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The server in our UCI Robotics and Automation Laboratory has been revived (thank you Kaustubh). This means the links to course notes and to Mathematica notebooks have been reestablished. Synthetica.eng.uci.edu now links to my web-page which needs work. A laboratory page that will replace this soon.

Rectilinear Suspension

Rectilinear eight-bar suspension

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This is a design concept for a rectilinear eight-bar suspension. It does not manage body roll but it does provide compact large travel.

Rectilinear Eight-bar

Rectilinear eight-bar linkage

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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.

Rectilinear Link

Six-bar linkage with rectilinear moving link

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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.

Rectilinear Linkage

Rectilinear Linkage