Robotics Inventions


                The Orientation Ratchet

This was a peculiar invention inspired by the way that a cat turns when it falls -- it is able to land on its feet

 without ever having a nonzero net angular momentum.  Details to be included as I get around to it!

There is a link here at Drury University.

 The project has also garnered attention from around the world, including tech-news website Slashdot, Robot Haven,

 Space Daily and EE TimesThe physics of its motion is described in this document, including

its behavior when attached to a torsional pendulum (a long, strong section of fishing line).  The project

was submitted as a proposal to the NASA Reduced Gravity Student Flight Opportunities Program a few years

 ago, and it flew on the Weightless Wonder in the Spring of 2004.









            A one-degree-of-freedom robotic arm actuated by two simulated muscles

Our one-degree of freedom arm is alive and well, on its own platform.  By actuating its two opposing muscles with sinusoidal contractions, we obtained chaotic behavior, just as predicted theoretically.  More about that when time permits.








            A two-degree of freedom robotic arm actuated by six simulated muscles

Shortly after the beginning of my recent work with colleagues Nicholas Hatsopoulos of the University of Chicago,  the idea of building a robotic arm actuated by simulated, servo-driven muscles became irresistable to me.  The problem of how the brain controls the arm is complicated and fascinating.  For example, our human arms, if you exclude the hand, has six degrees of freedom, yet these degrees of freedom are actuated by well over a dozen muscles.  How does the brain choose to contract the muscles to effect a desired motion, when there are many more muscles than degrees of freedom?  I have found that you cannot build something complex without understanding all of the steps involved in its construction, and it is easy to think you understand something when in fact, you don't even know what you don't know!  My first idea was a bit over-ambitious: the idea was to add 12 muscles to a model skeleton, which would have four degrees of freedom.  The initial idea is described here.

Below, left, is a diagram of the newest two-degree-of-freedom arm, currently near completion, built with the help of robotics consultant Joshua Petitt and many Drury students.  It is currently in its second incarnation, with a website of its own.  The first version (lower right) was built from odds and ends by Drury students, led by Jared Durden, who is now working on his doctorate in Florida.  He and Adam Scott, Ben Taylor, and Drew Dejarnette flew the experiment on NASA's Weightless Wonder aircraft in the Spring of 2007.   Videos of its motion in action to be added soon....




            A four-degree of freedom robotic arm actuated by twelve simulated muscles

The original idea was to actuate the arm of a human skeleton model with 12 simulated muscles composed of hobby servos and elastic components as described in more detail here.  In order to visualize the motion of this arm, the Drury University Holodeck was created (on my laptop using Matlab).