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[DPRG] Autonomous Flying Robots

Subject: [DPRG] Autonomous Flying Robots
From: Dean Hall dwhall256 at gmail.com
Date: Thu Sep 20 18:02:47 CDT 2007

I have never seen that unique aircraft before, thanks for sharing.   
Do the fans articulate independently?  (I imagine that would be  
needed for hovering yaw control, assuming hovering is a capability.)

!!Dean

On Sep 20, 2007, at 17:26 , Ed Okerson wrote:

> The one I am building is a 1/5th scale model of this aircraft:
>
> http://en.wikipedia.org/wiki/Trek_Aerospace_Dragonfly
>
> It is nearly complete, and hopefully will be flying soon.
>
> Ed Okerson
>
>> Saw this today:
>> http://blog.wired.com/defense/2007/09/british-polices.html
>>
>> There's a whole sub-industry out there building these things.  I'd  
>> be up
>> for trying one as well.  Silicon Sensing has a nice IMU out that  
>> looks
>> promising for stability control.
>>
>> Though, I've long thought of doing it something like this:
>> http://en.wikipedia.org/wiki/Avrocar_(aircraft) or this:
>> http://en.wikipedia.org/wiki/M200G_Volantor
>>
>>
>> -----Original Message-----
>> From: dpa [mailto:dpa at io.isem.smu.edu]
>> Sent: Sunday, September 09, 2007 1:38 PM
>> To: dprglist at dprg.org
>> Subject: [DPRG] Autonomous Flying Robots
>>
>> Howdy,
>>
>> Last March I bought my oldest son Stephen a small R/C helicopter  
>> for his
>> birthday.  It is a Blade CX, which features a pair of counter- 
>> rotating
>> blades that cancel out the torque on the airframe:
>>
>> <http://www.e-fliterc.com/Products/Default.aspx?ProdID=EFLH1200>
>>
>> and we had a lot of fun learning to fly it.  Then he went back to
>> college
>> and took it with him, so I bought one for myself and flew it  
>> around the
>> hallways at SMU for a few months.
>>
>> The counter-rotating coaxial blades make the heli very stable, but  
>> that
>> turns out to be a disadvantage once you learn how to fly, as it  
>> greatly
>> limits maneuverability.
>>
>> So last June I bought a TREX-450 for my own birthday, with a Spektrum
>> DX7
>> 2.4 GHz radio, and have spent the summer learning how to fly it:
>>
>> <http://www.rcuniverse.com/magazine/article_display.cfm? 
>> article_id=572>
>>
>> There are several interesting pieces of technology for robot builders
>> here.
>> It uses a brushless DC motor and speed controller with 2200 mAh 11.1v
>> Lipo
>> batteries.  These are extremely powerful motors with speed  
>> controllers
>> that
>> are somewhat like stepper controllers, some of which also have  
>> built in
>> "governors" and some of which can also be reversed (see the ones  
>> used by
>> the
>> R/C boat people).  The governors evidently measure the motor's  
>> back EMF
>> in
>> order to maintain constant RPMs.  Nice.
>>
>> The 2.4 GHz radio is also very nice, little stumpy antenna and up  
>> to 40
>> R/C
>> devices can operate simultaneously, each using a pair of  
>> frequencies for
>> data redundancy.  The radio actually has two receivers that are  
>> mounted
>> orthogonally a few inches apart, each with two antennae.  (Which  
>> means
>> no
>> more "frequency pins," for those R/C'ers among us.)
>>
>> Another interesting feature is the use of the motor itself for audio
>> feedback
>> during the programming sequence of the speed controller.  The normal
>> high-
>> frequency PWM signal is modulated down in the audio range, around 200
>> Hz,
>> to produce beeps and melodic sequences without a speaker or piezo
>> buzzer,
>> using the motor itself as the "speaker."  Very clever.
>>
>> The heli uses 3 microprocessors, one in the speed controller, one for
>> mixing the
>> R/C signals, and one for the gyro that controls the tail rotor  
>> pitch --
>> which they
>> call a "heading hold" gyro -- that sits between the R/C receiver  
>> and the
>> tail
>> rotor servo.
>>
>> Here's a video of me learning to hover last June:
>>
>> <http://www.geology.smu.edu/~dpa-www/heli/ 
>> first_hover_outdoors_m1.mpg>
>>
>> I'm a lot better than that now, and the "training gear" has come off
>> since
>> then.  Turns out that the hard part is learning to hover, to hold the
>> heli
>> in one place, and to do that in all orienations (especially "nose in"
>> hovering
>> with the nose of the heli pointed toward you --- I've gotten quite  
>> good
>> at that this summer ;)
>>
>> Which brings me to the point of this post.  It appears that  
>> hovering the
>> helicopter is very much analogous to the problem of balancing a
>> two-wheel
>> robot like nbot:
>>
>> <http://geology.heroy.smu.edu/~dpa-www/robo/nbot/>
>>
>> except in 3D, rather than 2D.  Here's the alogorithm for nBot's 2D
>> balance:
>>
>> <http://geology.heroy.smu.edu/~dpa-www/robo/nbot/bal2.txt>
>>
>> Doing the same for an autonomous helicopter will require a 3D sensor
>> rather
>> than the sensor that nBot uses:
>>
>> <http://www.microstrain.com/fas-g.aspx>
>>
>> more like the 3D IMU that jBot uses for it's navigation:
>>
>> <http://www.microstrain.com/3dm-gx1.aspx>
>>
>> and the balance algorithm needs to be expanded to include 3 axis.
>>
>> For those familiar with the sourceforge autopilot project, this  
>> was the
>> goal of
>> that autonomous robot project and their home-brew IMU.  Those people
>> went off and
>> founded Rotomotion LLC, and now have several working prototypes.  Ed
>> Okerson has some
>> friends who also have developed a home-brew multi-axis IMU which they
>> are currently
>> flying on an experimental autonomous helicopter at Stanford, and have
>> agreed to share
>> the design and data with us if we will do the same for them.
>>
>> Here is one of Rotomotion's helis flying autonomously:
>>
>> <http://www.geology.smu.edu/~dpa-www/heli/SR20_R34_small.mov>
>>
>> The $16,000 seems a bit steep, but maybe I am underestimating the
>> difficulty of the
>> project (again!).  If my skill level continues to improve then  
>> maybe by
>> Spring
>> I'll feel confident enough to begin thinking about throwing a  
>> switch on
>> the
>> transmitter and letting the heli fly itself, confident that I can
>> "catch" it
>> when the software doesn't work.  That will be a little harder than it
>> was with
>> nBot, and a few rubber bumpers like on nBot will not be much use in a
>> crash.  Still,
>> I think I can do it... :)
>>
>> As you may remember, our friends out in Seattle (Larry Barello) have
>> done some
>> interesting work on autonomous flight with autonomous guided para  
>> sails:
>>
>> <http://www.paraflite.com/>
>>
>> which must solve some of the same problems, but not the specific
>> hovering/balance
>> problem.  There are also some infrared devices that attempt to  
>> balance
>> the heli
>> my measuring the differential radiation from the ground and the  
>> sky, but
>> these
>> suffer from a number of problems for a more general purpose robot.
>>
>> So, is anybody else in this debating society <grin> working on a  
>> flying
>> robot,
>> or interested in doing so?
>>
>> cheers,
>> dpa
>>
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