ROBOTS: A "Hex-a-What”?! Hexacopters! When 4 Rotor Blades Just Aren’t Enough!

21 August 2014



Quadrotor
 

            I was amused when quadrotors (or quadcopters) made a comeback a few years ago.  Suddenly, the media seemed to be filled with images of these rather strange looking mini-UAV’s (unmanned aerial vehicles) with four “helicopter-type” blades instead of one. 

            I said, “made a comeback,” because quadrotors have been around for a long, long time.  The reason why they never made it to the “first string” in aircraft design wasn’t their mechanical complexity.  Instead, it was the difficulty of piloting these vehicles.  Older designs required a pilot to manipulate the blades, either angle or speed, individually.  This translated into a lot of distractions which, for the pilot, were a nightmare.

            But with the introduction of complex guidance mechanisms and, then, computers to coordinate the rotor angles and speed, the piloting issues vanished.  And the quadrotor was back!  But why would anyone want four rotors anyway.  The simple helicopter only had one, and it does ok.  Doesn’t it? 

            Actually, the familiar helicopter has always had a lot of problems.  The “one” bladed helicopter was a derivative developed from early quadrotor designs.  And, the helicopter has more than one rotor – there’s that little one on its tail.  Small as it is, that little rotor is extremely important because it allows the helicopter to maneuver horizontally.  The problem is that, with the reduced number of blades, helicopters are difficult to maneuver and tend to drift too easily.    

            So, what’s so great about a quadrotor?  Two things: (1) stability in the air, and (2) maneuverability – you can safely operate a mini quadrotor indoors!  So, with the addition of computers to coordinate the pitch and/or speed of the rotors, you have an ideal UAV. 

            Still, foolishly, I thought four blades would be enough.  But when computers started coordinating the four rotors, someone realized that computers could coordinate almost any number of rotors.  So, why not add a few more rotors?  After all, too much is never enough.
 

Hexacopter

 

            And the hexacopters are here!

Hexacopter: Reconnaissance, Surveillance or . . . Amateur Photography?

            Concerns have been raised about the use of UAV’s, particularly mini UAV’s, for certain purposes.  To use a mini-UAV for reconnaissance in a combat situation is one thing, but use by law enforcement or even private security firms for surveillance purposes could, in some contexts, be a real danger to individual privacy rights. 

            But as the debates rage, many other uses for mini-UAV’s seem to popping up.  Among others, photographers were delighted with the possibilities offered by the quadrotors.  The applications are almost limitless.       Consider nature photography, as one example.  With a relatively silent approach from above, you may observe and photograph wildlife at distances that would never be possible on foot.  And, from the air, you can capture angles that also would be impossible -- without an aerial vehicle.      Photography of many difficult to access locations with picturesque geographical features have become, not only possible to photograph, but easy with a quadrotor. 

            Of course, if you’re familiar with photography, you know that stability is extremely important to good photos.  In other words, the camera has to stay still when snapping the picture.  Some of the steady camera issues can be compensated for with high shutter speeds that catch images so quickly that the camera has less time to move. 

            But is a quadrotor stable enough to allow clear photography?  Well, sometimes, yes, and, sometimes, no.  No aerial vehicle can be perfectly stable under all conditions, but the quadrotor does an amazing job.  Again, a mini-UAV version of a quadrotor can be so precisely controlled that it can be flown in-doors without breaking anything. 

            Stability and precision are the quadrotor’s strengths.  So, when the quadrotor is used, it yields good photographic results more often than not.  But what if it could be made even better?

            Yes, better.  A more stable vehicle, in the air, would yield an even greater percentage of good photographs.  But what could make a mini-UAV more stable? 

            More rotors.

            Enter the hexacopter.  More stable in the air than its ancestor the quadrotor, the hexacopter can produce more high quality photos.
 

Hexacopter for Professional Aerial Filming

 

            And even greater stability is a real boost for another new group of mini-UAV users – filmmakers.  Mini-UAV’s offer an inexpensive and, even, easy way for filmmakers to get aerial camera angles without building expensive scaffolding or loading cameramen and equipment onto even more expensive cranes to be lifted into elevated positions to capture aerial angle shots. 

            When you need to capture motion, stability becomes even more important and, again, the hexacopter becomes not just a welcome, but valued, addition to the family of mini-UAV’s.

Hexacopter: A Political Leveler?

            But there is still a lot of controversy and debate about the possible misuse of mini-UAV’s in government and industry with resulting violations of individual privacy rights.  But, at least, one seller sees the hexacopter mini-UAV as a great “leveler.”  In other words, besieged with potential privacy violations by government and commercial enterprises, now, a private person can afford their own small fleet of mini-UAV’s.  With these, the citizen may be able to better “watch the watchers” -- so to speak. 

The Hexacopter and Flower Power                 

            But I know every reader is asking a key question: Sure, you can use a hexacopter for reconnaissance and surveillance . . . and . . . for photography . . .  and . . . in the dramatic arts like film production, but . . . where’s the romance?

            At least one manufacturer, India’s OM UAV Systems, markets their “Pushpak hexacopter” for more than aerial photography.  Their list of “Civilian applications” include “Flower dropping.”  What is “flower dropping?”
 

OM Pushpak Hexacopter

 

            A group of remote controlled hexcopters carrying a payload of flower petals are carefully maneuvered into position at the special event of your choice.  At a selected moment, the hexacopters release flower petals onto the area below.  The release is a gradual one with petals falling like snowflakes and continuing over a short but substantial period of time.

The Hexacopter: Absolutely the Last Word in Mult-Rotor UAV’s

            And so, six engines have solved all the possible issues that could ever come up with this type of mini UAV.  Now, we can rest assured that there would be no reason to add any more rotors to our mini-UAV’s. 

            But wait.  There’s the octocopter.  Yes, you guessed it -- eight rotors. 

Octacopter from OFM
 

            The German made “E-Volo” is the first electrically powered vehicle to achieve manned flight.  And it has . . . (gulp) . . . 16 rotors.
 

"E-volo erstflug" by Johnescalade

 

            A “hexadecarotor”?!

            And . . . , and . . .

            Where will it all end?!

No Post Next Week.  Next Post: September 6, 2014

Thursday 21 August 2014

GCLM5444HOxenia

ROBOTS: Mini UAV Quadrotors for Everyone?

14 August 2014



OM’s Curiosity Quadcopter UAV

            Robotic technology is advancing in all directions.  All you need to do is look at DARPA’s website and, then, the website of one of DARPA’s primary contractors, Boston Dynamics, to get your head spinning with so many, and such a variety of, exotically new and different projects.   But, before we go, let’s get some terminology out of the way.

            UAV’s come in all sizes.  When they’re small, they are often, logically, called “mini” UAV’s.  Although I’ve never seen a UAV as small as a nano particle, for some reason, the prefix “nano” is being used more and more to describe small UAV’s.  So, a small surveillance drone designed to fly like and hummingbird and camouflaged to, also, look like a hummingbird, is called the “Nano Air Vehicle.”  Now, any small UAV may be called a “nano” UAV. 

            Then, we have quadrotors.  These are those UAV’s, mini or quite large, that sport 4 helicopter type rotor blades.  Again, quadrotors have another name, “quadrocopter” or “quadcopter” and, then, a catch-all name, “quadrotor helicopter.”   

            When I first saw a quadrotor, I found it “different” in a quaint sort of way.  I love aircraft from the early days of aviation because of the diversity and, yet, simplicity of the designs.  Somehow, I get that same feeling when I watch quadrotors in flight.  And my instinctive association of the quadrotor design with the designs of early aviation was, surprisingly, accurate.

            Aircraft designing pioneer, Etienne Oehmichen, designed and built 6 helicopters in the 1920’s.  The second of the 6 was a quadrotor.  Named “Oehmichen No. 2,” this first quadrotor demonstrated remarkable stability and logged more than a thousand flights.  These fights were only tests because, in spite of its relative “success,” the Oehmichen No. 2 could only remain airborne for a few minutes at a time and achieved a range of just a bit over a half-mile.

"De Bothezat Quadrotor" by National Park Service

            Another quadrotor, the de Bothezat helicopter, was built by the U.S. Air Service in 1922.  It sported the, now, characteristic X-structure with the each rotor at the far end of the one of the X’s four legs.  It flew no higher than 5 meters.  Although the de Bothezat quadrotor’s performance was thought to be good enough to demonstrate feasibility, this quadrotor suffered from several problems that would haunt all quadrotors for decades.

            All helicopters, including the quadrotor, are relatively complex machines.  Their complicated designs and mechanisms made them much more susceptible to problems than their “winged” counterpart, the typical airplane. 

            The pilot was required to manipulate four rotors in order to maneuver the quadrotor.  Since navigation required continual adjustment of the direction of each of the four rotors at the same time, it was impossible for the human pilot to do much of anything else.  In other words, the piloting of a quadrotor was a nightmare. 

            With all these problems, you might wonder why the quadrotor design would be revisited again and again.  The reason was that, in spite of the complexity of both the mechanics and operation, the quadrotor was an amazingly stable helicopter.  The four rotor design gave the quadrotor a remarkable ability to maneuver with great precision – a precision that put the conventional helicopter to shame. 

            In fact, the conventional helicopter is a kind of watered-down version of the quadrotor.  For mechanical and operational simplicity, the four rotors were reduced to only one.  This made piloting much easier.  Horizontal maneuvers were accomplished though a second, much smaller rotor mounted on the tail. 

            These modifications increased reliability and made piloting the conventional helicopter a manageable task.   But these same “improvements” came at a cost by creating stability and drift issues that remain with the conventional helicopter to this day.

            Because of its potential advantages, quadrotors continued to appear as prototypes into the 1950’s.  But the 4 rotor design would only “take off,” figuratively and literally, when computers assumed the burden of navigation.  Computer manipulation of the individual rotors took the seemingly impossible task of piloting the quadrotor substantially off the shoulders of the pilot.  Then, computers moved into the pilot’s seat. 

            Sophisticated military quadrotors (and most all UAV’s) only require two instructions.  The first instruction directs the quadrotor to the coordinates of the target.  The second instruction directs it to the coordinates of the location to which it will return.   

            The mini (or sometimes “nano”) version of modern UAV quadrotor has an amazing number of military applications.  Ideal for surveillance and reconnaissance, the mini versions of these vehicles can be controlled so precisely that they can be safely operated indoors.  The quadrotor’s potential uses in search and rescue operations brought it the attention of law enforcement. 

            A perfect fit for a variety of industrial and commercial applications the quadrotor quickly jumped into the private sector.  In agriculture, for example, a quadrotor can examine conditions in many specific locations scattered over vast tracks of cultivated land -- without the cost, in terms of time and money, of physically sending a human being to each location. 

            And, finally, could you or I own one? 

            Yes, we could.  For some readers, one question comes to mind.  How much would one of those defense contractors charge for a quadrotor?  But many readers already know that you don’t have to go to a defense contractor to find a good quadrotor.   

            Now, dozens of manufactures are producing and marketing quadrotors.  Some offer entire packages.  Others even offer packages that can be packaged or packed into luggage and carried by any traveler – one who likes to keep their quadrotor handy. 

            So, you can even take your quadrotor to India with you.  Or if you find yourself in India without a quadrotor, you can buy one from a local manufacturer – one like OM UAV Systems of Delhi, India. 

            OM’s Curiosity Quadcopter UAV is designed to be portable as well as inexpensive to buy and use.  With on-board still and video cameras, it can be instructed to “visit” and photograph up to 80 locations (“way points”) on a single trip. 

            The “Curiosity” allows the operator to “manually override” the programmed instructions at any time in a particular “mission.”  But if the operator chooses not to interfere, the Curiosity will operate automatically: taking off, flying to its waypoints, and landing – all by itself.  

            But don’t let the technical specifications fool you into believing quadrotors aren’t . . . romantic.  OM Curiosity’s manufacturer offers a unique service in which several quadrotors are remotely controlled by specially trained pilots to produce a . . . “Flower Shower.”

            Loaded with flower petals – yes, I said flower petals – these quadrotors are precisely positioned to release their botanical “payload” at a just the right moment.  But no one has to worry about being bombarded with a load of petals because the release is a gradual one with petals gently wafting down around the guests at . . . whatever the special occasion . . . over a period a period of time – like a gentle snowfall.

            To assure the proper ambiance, the petal-dropping quad’s are equipped with quiet electric motors.  Then, the speed of the motors is slowed to make their operation even quieter. 

            Many of us may not need any flower petal dropping services in the near future but, certainly, there are those times when many of us could use a quadrotor.  And, in the future, many of us may own one.

Thursday 14 August 2014

GCLM5444HOxenia

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