Saturday, August 9, 2014

ROBOTS: KMel’s Quadrotors: Flocks of Small Flying Drones

7 August 2014

            Everyone has a wish list and so, apparently, do branches of the military.  What’s on the United States Air Force’s wish list?  Well, it’s not exactly your typical Christmas list.  Instead of “visions of” dancing “sugarplums,” the Air Force dreams of “flocks.”  Flocks of small flying drones.  At least, this is what’s on the Air Force’s “wish list” according to TechNewsDaily.com.


            And if this remarkable (and “must-see”) video is any indication, the U.S. Air Force is a few steps closer to getting its wish with one of the latest developments of the University of Pennsylvania’s GRASP Lab.


            The small drones in the video are called “nano” drones because they are small.  But, specifically, these are called nano “quadrotors.” 

            What’s a quadrotor?

            Well, first of all, a quadrotor is also called a “quadrocopter” – a name that gives you more of “feel” for what the drone looks like and how it operates.  Maybe the best solution is to call these things “nano quadrotor helicopters.”

            Anyway, quadrotors of all sizes are helicopters “lifted and propelled” by four rotors (or four sets of spinning blades).  The four sets of blades offer some real advantages.  Quadrotors have two sets of identical propellers.  Two rotate clockwise and the other two rotate counter-clockwise.  Lift and motion are controlled through changes in the speed of each individual set of blades. 

            Surprisingly, quadrotors aren’t a new idea.  In fact, in the history of heaver-than-air flight, quadrotors are a very old idea.   And the “quad’s” got off the drawing board and off the ground.  In the 1920’s and 30’s quadrotors became some of the first successful vertical take-off and landing vehicles. 

            And that was the problem. 

            They were great at vertical take-offs and landings, but impossible to maneuver in any other way.  Well, maybe, not impossible.  Just impossible for any human pilot.   The physical, moment to moment, individual manipulation of each of the four rotors was impossibly complicated.

            The recent re-emergence of quadrotors resulted from (1) sophisticated on-board sensors and (2) computers.  With the ability to precisely track the quadrotors position in relation to the ground and computers to just as precisely manipulate the rotor speed, the UAV (unmanned aerial vehicle) version of the quadrotors has become not just practical, but popular.  The amazing stability provided by the four rotor design is so good, that you can even fly mini (nano) versions of the quadrotor indoors.

            But back to the swarm of quadrotors.  Let’s start with the University of Pennsylvania and peal back a few layers of the “development onion.”

            The University operates the GRASP Lab.  GRASP stands for General Robotics, Automation, Sensing and Perception (Laboratory).  The lab integrates computer science, electrical engineering and mechanical engineering.   GRASP is staffed by the University’s students, researchers and faculty.  

            The Lab’s “Scalable Swarms of Autonomous Robots and Mobile Sensors” Project was explained by U of P Professor Vijay Kumar as an effort to describe the swarming habits found in nature and reproduce these “habits” in “networked groups of autonomously functioning vehicles.”

            But let’s peal back yet another layer.

            In 2007, two U of P graduate students, Alex Kushleyev and Daniel Mellinger met and both worked in the GRASP Lab.  After graduating, they continued their collaboration and focus on quadrotors.  In late 2011, they founded KMel Robotics and rented office space from the University.  For now, KMel continues to develop swarming robot technology.  Both Kushleyey and Mellinger, still, work with the GRASP Lab and the University on particular projects. 

            But KMel is self-supporting -- without producing a regular line of products.  And they’re not planning to jump into the mass-produced drone market.  KMel is well ahead of the curve in Nano UAV technology, and they both market and sell “their lead.”  KMel designs and builds custom quadrotor hardware (and software) for other researchers who don’t have the time or the expertise to do so on their own.   

            But to the point.  How does the “swarm” work?  The secret of the swarm is in the use CGI technology borrowed from Hollywood.  Each of KMel’s quadrotor carries a small mirror-like sphere which is tracked by motion-capture cameras.  In Hollywood film-making, a computer uses the tracked positions of these spheres on film to create and insert computer generated motion graphics.  But with KMel’s system, each quadrotor’s position is fed into a laptop which, in turn, commands each quadrotor to move in coordination with the group.  And, viewing the video, the resulting precision movements of that group are impressive.

 Quadrotors Hollywood Style

            KMel is more than a few steps ahead of the curve in “quad-swarm” technology. But another step will have to be taken before the U.S. Air Force gets its wish.  KMel’s precision flying quadrotors, still, are not a “true swarm.”  Each quadrotor is controlled from a remote laptop.  The laptop’s transmitted commands to each quadrotor cause the group to imitate the behavior of swarm.  And that’s the problem.  The individual quadrotors aren’t doing what swarming creatures do – in nature.

            To be a swarm, each quadrotor would have to individually sense the position and movement of the quadrotors around it, directly, and respond to their movements.  Instead, the current technology uses a camera to remotely observe the group.  The camera’s images are read by a computer.  Then, the computer transmits commands that choreograph the quads into predefined patterns of group position and movement.       Can quadrotors be developed to operate together as a “true swarm?”  Although such technology doesn’t exist, KMel is working on it -- as I write.

            Someday, soon, the U. S. Air Force will get its wish.  And, I can’t wait to see that video.  A swarm of flying drones would really be cool to see – as long as it’s not chasing me.

Vijay Kumar: Robots that fly ... and cooperate

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