Four-bar function generator: Open a door

Four-bar function generator

Four-bar function generator

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.

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Long-travel six-bar vehicle suspension

Long travel suspensions

Long travel suspensions

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:

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Rescue Robotics: Project Based Learning

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UCI, Vital Link and Orange County high schools and colleges are working together to organize a Rescue Robotics event in May of 2015. The Rescue Robotics challenge provides an opportunity for students in information and communication technology programs across Orange County to test their skills using ground and aerial robots to find and identify simulated human survivors.

Rescue Robotics Challenge Details

The Rescue Robotics competition has three main principles, each of which imposes difficult challenges on the student team which are important for the real world application of this kind of robot.

1 – Each robot must be safely autonomous. In other words, the robot needs to be programmed to do the work of finding survivors on its own without help from the student team.  This is an important need if robots are to help us search disaster areas.

2 – The robot must work in the natural environment on uneven terrain, with variable sunlight and wind. This is a challenge for most robot sensors, but important in a real disaster situation.

3 – The teams are allowed to use up to five robots which can be either ground or aerial robots. More robots makes it easier to find survivors, but increases complexity of programming the communication and coordination of the search.

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A speedy six-wheeled search robot that uses an Android phone as its processor. 

Rescue Robotics Workshop

At a recent Rescue Robotics Workshop teachers from across Orange County learned to build and program ground robots that use an Android phone as the processor and sensor system. They also learned how to build a quadcopter with an Arduino processor to search from the air.

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The quadcopter is a small and reliable aerial search robot. 
Screen Shot 2014-12-28 at 11.00.57 AMClose-up on Arduino microprocessor apparatus on aerial robot. 

Rescue Robotics is a project based learning program which is an extension of the Performance Engineering Program in the Department of Mechanical and Aerospace engineering at UCI, in which UCI students learn racecar engineering, build a racecar, and put it in competition against other schools.  The goal of both these classes is for students to learn engineering project skills and either take them to college or directly to industry.

Just like in UCI’s Racecar Engineering class, students create a useful product, which is just another goal of this educational program.  The crucial difference between the two classes is that Rescue Robotics is focused on information and communication technology rather than engineering and manufacturing.  Clearly the class involves engineering and manufacturing, but the spotlight is really on finding an effective and interesting way to teach students computer programming skills with real world application.  An overarching goal of this program is to strengthen industry in Orange County by enrolling 17,000 Orange County students in healthcare, engineering, and information technology career paths by 2017-18.

Freshman Project: Quadcopters

The Rescue Robotics program has strong connections to the UCI Freshman Project course Engr 7, where Learning by doing in a competitive team environment has been proven to be an engaging, exciting, and effective way to teach engineering to students.  Classes like this open up career and educational paths for students starting from a young age.

UCI’s freshman project class, Engineering 7, organized by Lily Wu, has over 200 new students building quadcopters.  The two videos below show some of their work.

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More about Rescue Robotics can be found at the Design News Blog.

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Kinematics Summer School

Profs. Carl Nelson and Anurag Purwar organized a Summer School on Kinematic Theory at the University at Buffalo, New York as part of the 2014 ASME Design Engineering Technical Conferences. Please select this link to get access to all of the talks: Kinematics Summer School.

Select this link for a YouTube playlist of the videos of each presentation.  

My lecture on the synthesis of six-bar and eight-bar linkages is the third item on the playlist.

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You can access a pdf of my talk at the link: Synthesis of Planar Six-bar and Eight-bar Linkages.

Among these is a nice presentation by Anurag Purwar on Quaternions and Clifford Algebras.

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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

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Linkage Design for Wing Flapping

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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.

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Linkage Synthesis at Disney Research Zurich

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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.

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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.

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