JPL’s ATHLETE Rover Walks, Rolls, and Slides

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JPL’s ATHLETE Rover (image from paper cited below)

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.

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ATHLETE at work (image from paper cited below)

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.

Citations:

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

Mechanical Flapping Wing

Linkage Design for Wing Flapping

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.

Disney Prototyping System

Linkage Synthesis at Disney Research Zurich

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.

Lamina Emergent Mechanisms

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-mechanismsLamina 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.

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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.

Select here to see Professor Howell’s presentation on LEMs at the Workshop on 21st Century Kinematics.