mechanical design

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.

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.

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.

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.

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/

Tag Archive for: mechanical design

Shape Changing Mechanisms Solve Design Problems

Wearable Robotics Put Spring in Your Step