RC India

So far, I have seen tons of discussion and various threads on this forum about building quad-rotors. But people do not seem to follow up here, and post the results of their work.  So here goes my attempt to build one, based on the design in this post.

http://www.rcindia.org/self-designed-diy-and-college-projects/quad-rotor/msg317/#msg317

This is a very simple quad rotor design (as it does not use micro-controllers, accelerometers, software etc).  It is expected to be a bit challenging to fly, but hopefully my heli flying skills would compensate for that.

Due to the nature of my work/routine, it may take a while to finish this... I hope it is short enough !

The parts list is as follows.

1.  4 x TowerPro Motor/ESC combos (25A)
2.  2 x Normal and 2 x Counter rotating 3-blade props
3.  3 x HK401B gyros
4.  3 x V-Tail mixers.

There are still many decisions to be made, like what battery to use (or rather, how many to use).  My plan is to use a 7 channel receiver, so that I can control the gain of all the different gyros from the TX itself.

The first step is to build a basic frame, it was done with balsa.

Wow that looks pretty good!!! Actually I find your design using vtail mixers with gyros a lil complex as oppossed to acceleros and gyros only :P...... What props are those? I think I have the same ones....

The counter rotating props are these : http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=5249

BTW, this is absolutely not MY design, it is from someone at rcgroups.com, posted here by Sai.

What a mess ;)

Update :

1 >  The motors were mounted with just cable ties.  Didn't feel comfortable with 3 screws going to the balsa frame, did not want to spend time making another mount plate using thin ply.  This seems to work OK for now.

2 >  Since the first step is only to see if the whole thing works and not build quality, the quad now has "legs" which are just blocks of sponge affixed to the 4 arms of the quad using just fiber tape :) Planning to change it to something more complicated later on. 

3 >  In testing just one motor (one of the elevator ones), it became apparent that all channels need to work like throttle channels.  On Futaba, the first impact of this is that all channels need to be reversed.  The second impact of this is that other than throttle, all channels need to have a "V" shaped curve so that the quadrotor will have a true "idle".  By default, each channel other than throttle sends out a signal to the receiver that is 50% of its maximum range (so that servos are centered, when the sticks are in their middle positions).  In this case, what we want is that the output should be 0 at middle stick (so the motor does not spin at mid stick for non-throttle channels).  These should then increase to full power on the motors as the sticks (aileron, elevator, rudder) are moved to either side.  This is why a "V" curve is needed on these channels.  On the Futaba 12FG, this is easily done using the "AFR" menu, and choosing a "POINT" curve (instead of an exponential curve).

@ Anwar,

The pics look nice.. It is coming up really well. Though I do not have much experience with helis, but I am sure your heli skills will definately play an important role here.

I guess you would have made one of the arms as master / front, which will guide you to decide the ailerons and elevator during the flight. I suggest you put an high intensity LED to it for demarkation.

How are you doing the CG of this model? I am sure you will take care of it :)

All the best  :thumbsup: and keep us posted.  :salute:

Ok, got it into a stage where I can just get it to lift off.  But there are significant issues which I am working through by tweaking the setup, before it can really hover !  I will post details of what has been done so far in a little bit.

way to go anwar....
looks awsome

Watching this thread carefully , When a heli pro like Anwar does this I guess it makes life for us much easier . once he  gets it to fly well I am going to take all his guidance  to make mine .

Anwar ,
I have supplied a lot of equipment for quads :  but till date have seen successful  completion of so few of them that I am not surprised that the are so many incomplete threads on this  subject.

With you  doing it I think  this could be the first one  that will reach its logical conslusion.

Sai

Sai, you took the words out of my mouth. This is going to prove to be the mother of all Quadrotor threads. Anwar Sir, please keep your communication on this thread idiot proof!

I have waited a long time for this to happen.

All the best!

VC

Wow, it looks awesome. Pretty sure that anwar uncle will get it hovering in the air soon.

Update so far.

4.  Forget everything I said in [3] above ;)  It sounded like a good idea at first while testing on a single motor, but realized later on that this would totally mess up the vtail mixing when multiple motors are in play.  So now we have plain / linear / default response set on all the four channels.   

5.  The next challenge was getting the ESCs to initialize and set the max throttle range.  Because of the gyros and vtail mixers, there was some output signal value being fed to the ESCs all the time when the entire setup is wired up, so one or more ESCs would refuse to arm. After trying various things, including setting up a different "flight condition" on the 12FG which would simulate the controls being pulled to the extremes just for initializing the motors, I finally settled on just setting up each ESC separately, including its throttle range.  One of the ESCs on the elevator still refuses to arm, unless I apply some elevator trim.

6.  The big challenge now is that even though the quad starts off stable, any tilt beyond say 20 degrees seems to get amplified and then it goes into a wild rocking motion which gets progressively worse.  This is regardless of any gain setting for the gyros, any amount of delay and no delay, and any amount of ATV/endpoint settings of the 3 gyro channels.  I also tried another set of props of different size.  I was about to try longer arms, when I came upon this post, which seems to describe the exact situation I am in now.

http://www.rcgroups.com/forums/showpost.php?p=14802789&postcount=31

So the primary suspect now is delay introduced by the V-Tail mixers. Options now are to try getting better v-tail mixers, or go for a slightly different design that avoids the vtail mixers entirely (where the gyros drive the ESCs directly).  It sounds more fun to get the vtail mixer based version to work (the design is so simple), so that is the direction I am going to take, and the hunt for better quality mixers is on.

I wonder how Sahil's mixers would work ! 

And I wish I had better testing tools, at least something like this :

http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=10572

Another guy who has run into the same issue.

http://www.rcgroups.com/forums/showpost.php?p=14055152&postcount=49

He seems to have ditched the project, and went for a mC based one.

I have been chipping away at this as time permits.

7.  Got the ESC arming issues solved by powering up the ESCs and rest of electronics separately.  For  now, just added another receiver battery to power the electronics first, then power up the ESCs later on using a big lipo. The converse also seems to work (ie, arm the ESCs first, then power up the receiver etc).

8.  The hunt for a better mixer is still on. Our local mixer king Sahil :) confirmed that his mixers are also low res.  Further investigation has lead me to this thread http://www.rcgroups.com/forums/showthread.php?t=1218835 .  So I have ordered 3 Digimix IIs.  They are sort of expensive at $60 for all 3 including shipping, and could have got a mC based setup working for similar prices.  But there is certain challenge in getting the simple design to work, so I am pushing it.  Plus, our club (Qatar Scientic Club) has expressed interest in the quad if I can get it working well, so I may just sell it to them when I am done.

9.  Some people have suggested moving the gyros after the mixers (the above thread has got that working on a tricopter), but I don't see how it can work on the quad design being used by me.  Comments ? 

10.  I can always cheat the design by getting rid of the vtail mixers and just going with 5 gyros and 1 or 2 servos to tilt the motors that serve as "rudder".  But then I have to prove Sai's version as viable ;)

Apparently, people who have attempted this have run into similar trouble before, as yet another thread reveals.

http://www.rcgroups.com/forums/showthread.php?t=1203378

This particular post from the above thread is very telling about the mixer quality issue : http://www.rcgroups.com/forums/showpost.php?p=14585139&postcount=6

Anwar ,
This not my version , this is what some one tried on RCG , I wonder  how he got the video of it functioning I have not tried it as well hence  no way my version.
The way I think this should be looked at is  as a platform to start from then  what ever is needed  to get it working with your expertise is what  should be added or deleted  so that  you can finally have a quad design on a low budget.


sai

Sai - It is clear that it is from RCG, I only meant that you publicized it here :)

Getting a working version is not a problem, as long as you use the right components.

I am tempted to try this, as time permits : 

http://www.embedds.com/mixer-of-two-servo-signals-for-v-tailed-airplanes/
http://www.gadgetparadise.com/121901/vtailmixer.pdf
http://www.gadgetparadise.com/121901/VTailMixer.asm

Rich Smith from RCG who confirmed that he has it working with a $1 AVR chip responded saying that he will forward the code when he is back from his present situation that is keeping from away from home. He said that he tweaked one of the commonly available mixer codes for the Tiny13s. This would keep the cost to a minimum, at the expense of added effort.

Answering a related question from another thread : http://www.rcindia.org/radios-and-receivers/gyro-output-digital-mode-and-escs/msg21977/#msg21977

Yes, I tried different soft start settings.  I was planning to try different timing settings too.  It was while testing the soft-start settings that I tried hooking up two servos to the output, and that is when I noticed the big delay in response to gyro induced movements (the delays on the gyros were set to minimum, and limits and gain were set to maximum).  So I started reading up on delays introduced by mixers, and did not get back to testing various ESC timing settings.  Will test them out anyways, but I seriously doubt if they will help.  Now that I am waiting for the new mixers, I have some time to play with !

Since our club is interested in a quad build, I have ordered this also :

https://store.diydrones.com/ProductDetails.asp?ProductCode=KT-ArduIMU-20

Basically, this has everything one needs to build a quad.  It is more fun to assemble such a board together with individual gyro components, accelerometers, play with some code etc; but I know myself too well to go that route now. Life is fairly busy, soldering skills are sub-optimal, etc etc ;)  The software part can still be tweaked, so a lot of  fun still remains.  

This board is very cost effective too, for the amount of stuff that is on there.

The plan is to get the basic system working with better mixers, but this is a side effort to get the quad stable at the earliest.

http://diydrones.com/profiles/blogs/arduimu-quadcopter

http://www.diydrones.com/photo/arduimu-quadcopter-2?

http://www.youtube.com/watch?v=A3FyJZbtSBk

http://www.youtube.com/watch?v=keAyWKbTzK8

Hey Anwar I have almost the exact same setup.... Its just my Arduino is separate, and the IMU board is separate... Do you know Arduino [rogramming? I'd recommend you look up www.Arduino.cc if you dont..

If your quad is flying, please post pictures/videos :)

Oh havent assembled it yet too busy with the software part, will do so ASAP...

I have the ardu imu board  can you point me to the codes  for using it as a quad

The ardu-imu codebase is here : http://code.google.com/p/ardu-imu/downloads/list

One quad specific version is here : http://diydrones.com/profiles/blogs/arduimu-quadcopter (look for a download link named "Quad1_15.zip")

hi guys.
not into electronics............so what is the 'ardu-imu '??
a complete software package that talks to esc,gyro etc ?
regards
don

Ardu-IMU has an arduino processing core with an "Inertial Measuring Unit".  This link has a list of what all functionality is included in it.

https://store.diydrones.com/ProductDetails.asp?ProductCode=KT-ArduIMU-20

There are two versions of it. The V2 one above has all the gyro + accelerometer stuff built in.  Another V1 version lacks all the gyro stuff, and you have to get them separately and interface it.

http://store.diydrones.com/product_p/br-arduimu-01.htm

The software is open source in any case.

Arduino is a platform based on the atmel brand of micro-controllers. IMU - Inertial Measurement Unit consists of a collection of gyroscopes and accelerometers. The complete codebase has been provided as above by anwar

An Awsome guide to the basics of an IMU board.
http://www.starlino.com/imu_guide.html

hi guys.
ok .......that WAY above my head there :)
so basicly................. is it a board you hook the motors and rx up to and it does its 'helicomand' type thing ?
regards
don

I realized that there is one more component I will need (unless I hack up one of my receivers).  Basically, the above board works on a single PPM signal from the receiver, as opposed to a bunch of individual PWM signals (one for each channel).  So I will need a PWM to PPM converter (unless I can figure out how to tap PPM signal on a dirt cheap receiver, some people have tapped Corona receivers for this purpose).

With something like this : http://store.diydrones.com/product_p/br-ppme.htm , one can take 8 PWM channels (basically 8 servo outputs) from a reciever, and encode them all into a single PPM signal. So only one input pin is needed on the arduino side.

If anyone is going with diydrones.com stuff and minimal DIY, it is better to wait for their ArduPilot Mega product, which seems to have this also built in. It is supposed to be just connections and no programming. On the flip side, it has way too much functionality, and not sure about the price either.

ArduPilot Mega is receiver ready :

http://diydrones.com/profiles/blogs/ardupilot-mega-home-page?xg_source=activity

Anwar ,
Looks like the codes will be released around early July  from Chris's replies

Got the equipment to try both setups (using better vtail mixers, and using the complicated microcontroller based version) !

Tests using the vtail mixer based one is simple, just replace the mixer, tweak and test.

But the one using the microcontroller involves some delicate soldering and playing with software. Haven't done ISR level C coding since degree project involving decoding viruses in assembly and writing vaccines for them in C the early 90s (wonder if anyone remembers the MichaelAngelo virus ;D), so this would be a good journey back in time. The only concern is time ! 

I used to have a collection with full source of those DOS era viruses.. Must be somewhere in my study back in India.

At that time, I was particularly amazed by the virus "Happy birthday Joshi"... whoever wrote that had a true command of the computer architecture.. Was quite a learning for me and picked up some neat way of performing multiplication/divisions of large number.

Ah, I was hoping/expecting someone who had interest in those areas (and from that era) to respond :)

I even got the LBBV (http://vxheavens.com/lib/vml00.html) ordered from the US through a friend, to see more samples of code (back in 91!).

BTW, the board I ordered (with 3 axis gyro and 3 axis accelerometer) comes with code, but original design has an extra magnetometer and related code too.  And I will be forced to tinker with the code to remove the magnetometer code, and see what additional stability can be derived using the other sensors.

If you have the interest and time, try the Giant black book by the same author. He covers most of the security threats including modern day worms.

Nope, moved on to other things (business apps, scalability etc) ;)  But those days were fun.  Just using "DEBUG" that comes with DOS, it is fun to disassemble the virus code, and then writing a vaccine in C (including neutralizing it in memory first... the magic of "cli()" and "sti()").

Now this Quad project should be fun.  I had not come across the use of a magnetometer for stabilization until a few weeks ago. That was a whole new dimension to the problem.

Tried one more brand of mixer, did not have much success.  In fact, it messed up the outputs so bad, that just getting the ESCs to arm became pretty much impossible.

So moving on to the microcontroller based design.  Got the ArduIMU+ and magnetometer soldered up.  That itself was interesting.  I hadn't done any precision soldering for a long time (over 15 years), so had to get everything fresh (low wattage iron with fine tip, thin solder, wick, etc).  Downloaded the Arduino software development environment, and the code that is specific to this board.  Changed some settings, and uploaded the code to the board.  Then used their testing software that would dump out the values from various sensors, and show an airplane that moves as one tilts or moves the sensor board.

Here is a video of that testing.

http://www.youtube.com/watch?v=bFtO0ScbYS8

Wow!! Way to go for myself!! just as Vinay was telling that flying might become boring after a while, I guess there are lots of things to do!!

keep up posted Mr Moderator!! this looks pretty exiting!!

Nice work Anwar !!!  :salute:

Keep us posted. BTW, what is this magnetometer used for ?

Cheers!!!
Saurabh.

I am also quite new to magnetometers, especially in such applications.  Usually in UAV type of applications, a GPS is used to figure out if the aircraft has drifted away from where it was before.  But for short distances and indoor applications, this does not work, and that is where the magnetometer comes in.  It helps determine positional drift in the yaw axis.

gud work anwar bhai....

Here is a nice write up on how gyros, accelerometers and magnetometers all come together (and GPS too).

http://diydrones.com/profiles/blog/show?id=705844:BlogPost:41145

Anwar, any update on your quadrotor....?

all,

i started a thread in the forum called quad rotor.. in that many asked me for the video .. just before i made a setup for a student with my controller .. pls comment on my video ..  first flight of my controller with out any tuning .. she will be rock solid in the air with fine tuning ..

happy diwali


http://www.youtube.com/watch?v=sFMXRfPuz2o (http://www.youtube.com/watch?v=sFMXRfPuz2o)

im making 8 rotors .. with dslr ... for aerial photography ...  videos soon  ;)

Haven't worked on it since I went on some long trips. 

And after coming back, all RC/free time these days is spent on the forum, and training others.

In fact there are a bunch of things to be built, including a Trex 700 heli !

Did you find anybody who manage to fly it without using microcontroller board and just by using mixers and gyros...?

My research led me to two options.

1.  There is a way you can build a mixer that can handle signals that arrive out of sync (as is the case here, where there are gyros feeding into mixers).  But I could not find the code for it online, and did not have the time to work on it at the code level.  Might try it someday, it is in the back-burner now.  I have posted some RCG threads about this earlier in this same topic.

2.  People say a mixer called "Digimix III" will work, but they are expensive.  Might as well get a mC based one, which is what I did.

The diydrones.com guys now have a new board that is ready for quads out of the box.  It came out after I got my stuff.  With that, there is no need for separate PPM encoder etc, it is just an Arduino board and a sensor board tightly couple as an integrated unit.

hiii
anwer
i was searching quad rotor helicopter procedure from last 3 months. i want to make my own
after i saw your thread finally i believe that i can make it and i am starting from today
so can u please help me out for throwout the project?
because i am beginner to make any kind of robot i think i have to face many problems
but i think u can help me out.

As you can see, I have to get mine completed.  Another member of the forum, "vulture", seems to have done it, and has more information.

I can help with what I have learnt, but it is not much yet :)

i guess the resolution may not be causing the problem ,,, it will be the sequence (asynchronous in the cheap mixers) fro the rx ...as in pwm signal it comes in sequence .... if that attiny can take asynchronous inputs it will work ... i ran into same problems which are not yet solved ... 8-)

keep us updated sir :salute:

Well, it does fly.  But I have cheated so much that it is not even worth mentioning (other than "getting it done and out of the way", without any passion whatsoever!).  All the DIY fun is gone, and the software is closed source :(

Basically I found a brand new quad controller for sale on the US forums, which was a new product from a small company. 

http://shop.fyetech.com/product_info.php?products_id=41

A bit of research showed that it is pretty good, and the price was great (as it was being sold by someone who bought but abandoned the project, so it was marked down significantly).  So I got it, mounted it on my frame, and it flies well.

There is some tweaking to do, but my frame did take off into the air !

I will get back to the other one (using ArduIMU) at the earliest where all the DIY fun resides. This one will be given (sold) to the club, as they are looking for a controller that can handle a variety of speed controllers, and they have some jumbo plans for the same !

http://www.youtube.com/watch?v=LH4Q8kfztTw

Flew it at the field today, in quite windy conditions.  It flew great !  So this is a good quad controller for anyone with a custom frame and want to use commonly available power combos.

Forgot to take videos though :(

Here is an outdoor flight clip on a very windy day. Still in hover (full stabilization) mode, which is not the best option for aerobatic flight but would help with the wind.

http://www.youtube.com/watch?v=qvSRKX4iRNE

very nice Anwar.
Very simple to wire up.
Last one month i was reading a lot on Arduino +M+ and Nunchuck type of Quad.
i bought all parts. Assembled a board/ made and wired the frame.
Still lot to do on setting up etc...
So much of work.... to get it fully done and working. Will post some pics.
Seeing this, i am not so sure, what i have been doing is worth all that.
regards
ashta

Great to hear about that project :thumbsup:   Looking forward to a proper "Quad Rotor Build Thread 2" soon :)

The DIY fun is always much more, plus any software tweaks (if you are inclined), PID tuning etc all should be lot of fun. If you are following any particular build (like you did for the tricopter), please do post a link. 

What you are doing is the one that is "worth" anything !

Sold the Quad to the Qatar Scientific Club.  They have big plans for that platform, trying to build a self powering system using solar panels (not sure if this will work, but they are going to try!).

Got the HK Quad controller board, so quickly built another frame.  The CD Rom case is a little too tall, but that was all that I could find at home.

The setup is fairly easy, although I am still playing with gain values. 

I have a second board, will make a tri-copter with it after flashing it.

One thing that caused me to lose some time was that the instructions are very specific about how to arm the controller.  The instructions in the HK manual for this board are taken verbatim from here :

http://www.kkmulticopter.com/index.php?option=com_content&view=article&id=55&Itemid=57

In the "Adjusting" part, it says move the left stick to the "right", when it is at the lowest.  Further the trims are to be adjusted again to the bottom and right, if it still fails to arm. 

http://www.kkmulticopter.com/index.php?option=com_content&view=article&id=136:how-do-i-arm-the-board&catid=36:kkmulticoper-basics-faq&Itemid=41

It turned out I had to reverse the rudder channel earlier in the setup, so that "right" side did not apply any more, and the controller is armed by moving the rudder stick to the left (in my case).  Figured it out after a few minutes of scratching my head on why the board failed to initialize / arm.

The maiden was smooth... video to follow.

Maiden.

http://www.youtube.com/watch?v=bPHd9BHBUpY

sir, pls tell me distece between motor to motor in your  HK Quad controller board air frame .

About 52cm from shaft to shaft.

really wonderful anwar bro.i saw your pics and all gyros are set to < 50% is it ok to let them to default position?

very nice build anwar sir.
sir im trying to build a tri-copter,i have the same board,but when i flashed with a new firmware its not arming,its arming when the board is flashed with a quad firmware.could you please help me to solve this problem? ans could you post a link where to download the tri-copter firmware?

Those blue pot positions were arrived at after some tuning.  It is a good strategy to start out with default positions, test fly, and adjust (slowly!) to get the performance/stability you are looking for.

I haven't tried this yet (it is on my to-do list!), but it seems you have to use the Tricopter v1.5 version.

http://www.kkmulticopter.com/downloads/firmware/TricopterV1_5.zip

Now depending on whether your yaw/rudder is reversed or not, it should arm with throttle at zero and rudder stick moved to one of the extremes.  Which extreme (left or right) depends on whether your yaw/rudder is reversed.  If you are mode 1, remember that throttle is on the right stick, and rudder is on the left stick.  So the right stick should be towards the bottom, and the left stick should be moved to the left or right (while it is still at the middle in terms of vertical position, ie at zero elevator input).

yeah as anwar said make sure whether throttle is reversed or not.and move trim to the extreme point.sometimes controller unable to detect 0 throttle due to trim position.

It is the rudder/yaw reversal that matters more.  You can see the arming stick positions in the image below :

For mode 1 (top left in the above image), it shows rudder stick moved to the right.  If your yaw is reversed, it should be moved to the left instead.

(http://www.kkmulticopter.com/images/stories/xxcontroller_kr_mode.png)

thanks anwar bro, useful info.i think you need to add thanks plugin =p

@anwar sir,

which setup you are use in your hkquad.
motor
esc
battery

http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=5354  (EMAX CF2822 motor)

http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=6548 (HobbyKing SS 18-20A ESC)

Turnigy NanoTech 3s 2200mAH  25-50C lipo

 sir, which prop you used

The ones in the picture are 7x4.  I do have more to experiment with.

sir what is the cost of it?

i want to make this project..

@ Anwar sir
How can you mount motor without screw/nut in useing hk board quad, i want some idea to fix motor.

While testing my HK board, I just used rubberbands to attach the motor, as the balsa arms of my quad were wide enough to almost cover the based of the motor.  But that was only for testing. 

For production/final use, see the method followed by Ashta bhai in his quad thread as one possibility.  Basically people attach small pieces of ply to the arm, just like you would do on any balsa build (with epoxy and/or screws, plus triangular pieces of balsa from the sides).  Then attach the motors to the ply sheets that have been cut to the right square/rectangular size to fit the base of the motor.

A Dremel is wonderful in such occasions !

Hey buddies,
I started to build a quadrotor using Arduino UNO. I am totally new to this RC field.
Got all the parts of quadrotor except IMU and tested well using Arduino UNO. But, now the problem is that I am not able to hover quadrotor without sensors. So, I am thinking of IMU for it.

So, anybody tell me which IMU is best suitable with Arduino UNO Controller..??
Guys, please do reply..!!

I am making a quadrotor setup of Arduino UNO+Zigbee..
Which IMU suites to this setup.?
Any Indian vendors delivering this ArduIMU.?
Suggestions please..!!

Look up robotics and project sites:

www.rhydolabz.com, www.tronixkart.com, etc.