Truman Pollard’s wheelchair seat design which repurposes race car seating is an inspiration. The engineering effort needed for our racecar project spans so many different activities any one of which can be the foundation for a business. Find more information at the link Truman Studio
An outcome of Mark Plecnik’s research on the kinematic synthesis of six-bar linkages is a variety of designs for the leg mechanisms of small walking machines.
We hope to build this walker over the summer. It has one drive motor on each side:
This is my favorite because it couples the legs on one side with a pantograph linkage. The leg joints are living hinges. and it seems this the entire leg system can be cut from a single sheet of plastic:
This is a design study for a walker with eight legs on one side, 16 total:
MechGen Suspension is our latest iPad app. It is an ambitious design system for an independent suspension. The designer specifies the vehicle geometry, lower control arm, the wheel movement and camber gain. The system designs the upper control arm. If this is of interest, please contact me.
MechGen FG is now on the iPhone, thanks to the excellent work by Jeff Glabe and Kaustubh Sonawale.
This port closure tool curls back on itself to provide internal stitches to close a trocar port used for non-invasive surgery. This is the result of a collaboration between Kaustubh Sonawale and Jon Stokes.
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:
The ATHLETE Rover is a mixture of a wheeled rover and a walking robot, or better a walking truck, created by engineers at Jet Propulsion Laboratory to be used for manned and unmanned missions to the moon. ATHLETE, which stands for All-Terrain Hex-Limbed Extra-Terrestrial Explorer, is a six-legged walker that is taller than a person. The walker also rolls since it has powered wheels at the end of each limb. This allows the ATHLETE great mobility over changing terrain.
An innovation that comes from the leg-wheel combo is the Sliding Gait, which is a mode of transport more efficient than walking that can be used over loose or steep terrain where driving is impossible. Sliding Gait uses some of the articulated legs as anchors while others do the walking or sliding, like skating. This allows for quicker more responsive movement of the robot. The ATHLETE is to be remote controlled from earth or by astronauts on the moon, so the many different ways the machine can travel give more options to a remote user to navigate tricky terrain.
Motion planning is critical to the operation of ATHLETE because it is both a walker, a rover and something in between, so it takes some work to plan out each step. Footfall is the software that assists the remote driver in planning each step. It uses “telemetry from the robot, such as joint angles and stereo camera image pairs, and generates 3D terrain map,” computes a sequence of movement commands and presents an animated preview to the driver. Footfall makes it possible for this big robot to really move.
“FootFall: A Ground Based Operations Toolset Enabling Walking for the ATHLETE Rover,” by Vytas SunSpiral, Daniel Chavez-Clemente, Michael Broxton, Leslie Keely, Patrick Mihelich, David Mittman, and Curtis Collins.
“Sliding Gait for Athlete Mobility,” NASA Techbrief, This work was done by Julie A. Townsend, Curtis L. Collins, and Jeffrey J. Biesiadecki of Caltech for NASA’s Jet Propulsion Laboratory.
Read more about the ATHLETE Rover at JPL’s Website
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.
BYU Professor Larry Howell studies lamina emergent mechanisms, in other words, machines that emerge from flat pieces of material. If you think about the subtly complex movement of a children’s pop-up book, the way a page elegantly untucks itself to display a scene and then tucks itself back in, you wouldn’t be too far off. The interesting thing about lamina emergent mechanisms is that they are compliant mechanisms that come out of a plane—out of a flat surface—which allows for a low cost of manufacturing. The trick is that designing something like this is challenging, and indeed “design of lamina emergent mechanisms that have not previously been possible” is the big challenge this research pushes up against.
Lamina emergent mechanisms, or LEMs, can perform sophisticated tasks with simple topology. The cost efficiency of this type of mechanism starting from a flat initial state means that there is the potential for very affordable manufacturing. Since these mechanisms “pop out” of flat materials, manufacturing them in large quantities is cost effective since the associated manufacturing processes for replicating sheet materials are relatively simple and therefore low cost.
Lamina emergent mechanisms are notable because they save space. They emerge from a flat initial state so they can be used in applications that have limited space, which is oftentimes a design challenge. From a business perspective, these mechanisms are attractive because they can be made compact for shipping and then later deployed in their designed function at the desired location when they need to be. Reductions in handling, shipping, and storing, particularly in high volume, can lead to significant cost savings.
Another thing to note is that these mechanisms can interact with one another in interesting, useful ways, as seen in this image.
The word that comes to mind with lamina emergent mechanisms is efficiency. We’ve talked about efficiency in manufacturing, but now let’s talk about efficiency at the machine level. The creation of controlled motion without bearings leads to opportunities for increased precision because of the elimination of backlash and wear, reduction of friction between rubbing parts, and the lack of a need for assembly since the devices are single-piece constructions. There are a lot of wins with LEMs, which means they have a bright future.
A key to the continued advancement of LEMs and their applications is the development of actuation approaches to allow them to move. – BYU Compliant Mechanisms Research Website
Professor Craig Lusk (University of South Florida) works in the same field and designs shape shifting mechanisms that could be used for statically balanced body armor that could take the form of a collapsible shield or provide full body coverage.