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FEZ QuadCopter startup


#1

Hi All,

Perhaps Im a bit off-topic, so please forgive me. I’m a professional C# programmer and a noob on hardware. Just started with the FEZ Panda 2 and love working with it. I finished my robot project and would now really love to see a creation that can actually fly. So for the upcoming winter I’ll set my focus to a quad copter.

I’ve got an idea, but perhaps someone can already point out some stupid mistakes.

For instance, I’d like to create my own remote control, and the quad copter has to be driven by the FEZ Panda 2. To do so I just ordered 2 XBee series 2 professional’s. I already have 2 FEZ Panda’s. I intend to create the remote with one FEZ / XBee and the quad logic / receiver with the other one. It has more than a mile “line of sight” distance and should be fast enough to process the commands.

I know there are a lot of concerns about the FEZ using the GC and messing up the timing, not being real time etc… but that’s the challenge i’d like to try and solve (could be that I fail, but trying is half the fun).

First challenge would be a quad that simply flies stable. I’m thinking about the WII Motionplus remote. It has all the gyro’s etc. aboard to see if it’s “stable” and I intent to correct this if it’s not. I know there is a WII Motioncontroller library available to use and possibly to alter for WII motionplus.

I’d like to have this project running within my lifetime so will buy the frame from HobbyKing (http://www.hobbyking.com/hobbycity/store/__16583__HobbyKing_Quadcopter_Frame_V1.html). Hope they deliver in Holland where I live (therefore also my apologies for this bad English writing as it it not my native language).

I’ve read some about Turnigy and hope 4 Turnigy D3542/5 1250KV Brushless Outrunner Motor’s will do the job of lifting the frame, FEZ, WII controller and battery packs.

I already have a Li-Poly balancer / loader and need to study some more on the battery packs needed to sustain some minutes of flight.

I don’t know anything about propellers yet either, except that I should have 2 turn in the opposite direction.

Now I drive my robot with a engine controller using 2 PWM’s. I probably need an engine controller for the 4 turnegy engines as well. I see controllers like the http://www.hobbyking.com/hobbycity/store/_17537__HobbyKing_Quadcopter_Control_Board.html but that already has all the stabilizing logic in it. I want my FEZ / WII controller to do that.

So actually I’m looking for a “dumb” board I could simply specify the power output for on 4 engines using the FEZ’s PWM.’

With my robot I had a lot of trouble with noise coming from the DC engines. Learned about grounding both engine battery and FEZ battery to the same ground and adding a capacitor on the engines to filter noise.

Would that be something to take into account using brushless engines as well? Should I use shielded wires everywhere? Take more measurements to prevent noise?

Another thing that I don’t get is how a Quad could maintain it’s altitude. I guess GPS would be a option, but I see a lot of Quad’s without an GPS module. A simple distance sensor in the bottom seems to amateuristic, but might work, but what if an obstacle crawled under the quad, would it jump up?

Any help, tips, info, etc would be very appreciated. I know I don’t get 90% I need to know to get this working, but I hope to learn and get it to work.


#2

Yes but I do not know why!! NETMF runs your own application and so you can control what GC needs to do. So I do nto see GC being a problem. Also, GHI’s FEZ boards run RLP which includes real-time tasking. Another reason on why a quadcooper is very much possible on FEZ.


#3

Hi Gus,

Thanks for your reaction. I completely share your thought. And maybe I don’t get what Im getting myself into, but would the timing really be that crucial? I could program a class to see from the wii motion sensors where Im getting out of balance. Wouldn’t it be just a increase on the right engine (or decrease on others) to correct that? So maybe It’s not responding within a microsecond but I can’t imagine that it should. Otherwise I hope to correct that with a bit of AI.

I don’t know anything about RLP programming yet but know a lot about C# (okay, a lot less about the compact framework). Think I can also get the GC to wait until it’s allowed to do it’s job. So I do hope I can get everything to work with native FEZ Panda 2 code. The processor is extremely quick, it proved itself to me on my robot where it had to process 2 motor controllers, 2 line readers, piezo and IR commands moving fast! So I can’t imagine it fails in stabilizing the quad (ok, Im still far away from spins, rolls, loops, etc.).


#4

Great project! I am working on a VTOL airplane and a friend of mine is working on à netduino powered quad, hopefully we can share experiences! i would suggest an IMU plus GPS , look at sparkfun.com for imu’s. IMU + gps will give you much greater stability. You’d need a good algorithm for sensors though, à kalman filter so filter out noise. im not sure about your motor control, but R/c ESC’s for each motor, controlled by pwm is a great solution.


#5

Hi mammaplank,

Phew - a lot to get through, but seeing that I’m on exactly the same journey I’ll try and summarize…

Have a look at this thread… http://www.tinyclr.com/forum/1/881

Half the camp reckons it can be done with .Net alone and the other 3 quarters say you’ll need RLP. There’s no correct answer - yet - a bunch of us are trying different things.

“Simply” creating stable flight is the entire problem. You will need fast PID loops to balance the quad. Exactly how fast isn’t really known at the moment, but I do know that a regular RC rig demands a minimum of 30ms response time over 8 channels, so it is pretty fast. My experiments have shown a simple polling loop can run at about 10kHz under managed code. Not near the 400kHz some people are working with, but maybe workable.

To power the motors you’ll need 4 brushless speed controllers. A lot of people are using the Plush 25 Amp from Hobbyking. You can connect 1 per PWM channel.

Propellers and motors should be matched to give the best thrust at the lowest RPM and lowest current draw combination. I couldn’t find any magic formula for this, but there are tons of suggested combinations on the Aeroquad forums etc. 2 Propellers are “normal” and two are “reverse”. Search Hobbyking for “Counter Rotate”

Shielding is always a good idea - especially the signal cables. Try and run them far away from the battery cables and especially the 3 wires running to the brushless motor.

Regarding altitude… There are a number of ways people are doing it:

  • GPS (very course - can be meters off)
  • Barometric pressure sensor (measures altitude above sea level). Seems to be the most popular.
  • Ultrasonic distance to ground (yes, it will probably jump if something walked under it!)
  • Optical distance to ground (Those Sharp modules used in robots - but only good for 30cm or so)

I’m using this “IMU” in my design. No idea if it will work yet… http://diydrones.com/xn/detail/705844:Comment:627539?xg_source=activity

I’m really hoping to spend some time over December on this. It is a pretty big project but you are certainly not the only one that wants to see a Fez fly :slight_smile:


#6

Hi C0ax, Realiser,

Thank’s so much for taking the time to help me out. You guys are so far ahead of me on this journey, It’s really great to read all this info.

I’ll probably spend all night studying some of these terms. Did not hear of the IMU yet, the flash movie on http://www.varesano.net/projects/hardware/FreeIMU#v0.3.5_MS is exactly what I was trying to do using the WII motion controller, but the IMU would also have the height measurement on it so seems like the best way to go.

The FEZ Panda 2 is running at 72Mhz, I’ve read about people running quads with way slower microprocessors, though I start to think that they “offload” the balancing to a specific board. ThePlush 25 Amp is exactly what I was looking for.

I read that brussless engines had a lot less noise than DC engines, but better be safe than sorry (had a lot of noise problems with my driving robot, interrupt ports triggering wildly. processor on halt, etc. don’t want that to happen in the air).

The first version(s) would probably be very simple without an GPS module in it. I don’t want to keep replaceing them after each crash. After it’s stable I hope to add more fun to it and hopefully someday a camera as well.

Do I also need to worry about LI-Poly packs exploding after a crash? (because that would probably happen the first couple of runs). I read that they could explode quite easilly but hope that I don’t need to build a bunker to place them in.

Would it also be a good idea to use the XBee modules for remote communications?

Thanks a lot again and good luck with your projects!


#7

Yes, you are not alone. It sounds like we have nearly identical projects in the works. realizer did a good job summing up the basics. You can follow my progress here:

http://blog.ianlee.info/search/label/Omnicopter

I’ve been very busy lately with work and some classes I’m taking and my ability to find time to update my progress is lacking. I’ll try to correct that this week. I’m just now at the point where I’m about to start writing my balancing code. That should start this weekend.

One piece of advice… You will probably order most of your RC parts from HobbyKing. Don’t know about where you live but in the U.S. it takes about a month to get parts delivered or longer if they don’t have what you need in stock. One of my ESCs only lived about 5 minutes… So, my advice is when ordering from them order an extra ESC (or two) and maybe an extra motor if you have the means. Most other parts you can scrounge up from other places that deliver more quickly if you get in a pinch. I’m still waiting for my replacement ESC that was ordered about 3 weeks ago.

I’m using this IMU…
http://store.ckdevices.com/products/Mongoose-9DoF-IMU-with-Barometric-Pressure-Sensor-.html

What attacted me to it is that it is actually an arduino board that runs software that handles all the raw data and just sends me the data (already filtered) that I need. This way I can offload all those calculations and let the IMU run in a faster loop that my program code actually needs and hopefully get me a better filtered result when I use it. They are also planning to come out with a GPS add-on for the board in the future. Hopefully before I’m ready for it.

It’s a fun project. Welcome to the community and keep us posted on your progress!


#8

Yes they do. I have ordered LIPO batteries before.
The thing with lipo batteries is though that they only ship to a certain amount of mA.

If you need more power, you can order from their German warehouse (if in stock). The price is a little more expensive, but not gigantic :slight_smile:


#9

@ IanLee74, Thanks for your reply and thanks a lot for summing up all your work on your website. Just started reading and it will help me a lot (complements on the writing as well, it’s fun to read!). Can’t wait to read your updates. Seems like you are almost at the point to get it flying, very exciting. I noticed 8 power plugs on one of the images, so thought you started a octocopter, but now I see it’s also a quad.

I start to think people abandoned these kind of projects and there are no more electicians left. Had a lot of trouble getting my hands on some capacitors, took about 2 weeks to get here. So I can wait some time for parts, but thanks for the tip, i’ll start ordering and order replacements too (just got the XBee modules, so can start on the remote part first, just like you did). Does mean that I need to figure out what engines and propellors to use, but I think I’ll just follow your example :slight_smile:

@ Robert Jacobs, tnx! That gives me some new hope of actually receiving my order :-). We can order some lipo’s here as well but they have about half the capacity compared to the ones that HobbyKing has to offer at twice the price.


#10

Good eye. Currently, it is a quadcopter but my development frame allows it to fly with anything from 3 to 8 motors. This is why I call it the Omnicopter and not a quadcopter. The wing arms slide in & out of the arm sockets and allow me to try any number of combinations. However, the first goal is to make it fly as a quad. Unfortunately, this design has also created a lot of extra weight. Once I’m fairly happy with it’s flight, I’ll start work on a more permanent body design and reduce the weight down. I have several fun new ideas there that I’m looking forward to implementing but first things first…

My engine choices were far from scientific. I basically looked around at what others were doing then compared that to what was in stock at HobbyKing and went with it. I suspect that before this thing is all over I’ll probably try several different motor/propeller combinations but the motors I have now seem to have more than enough lift to get it off the ground. Since you mentioned you bought a frame instead of building your own, you’ll want to take into account it’s dimensions to make sure your props don’t overlap. My total copter is about 2ft x 2ft, so it’s rather large for a quad. I made it this way with the plans of it being able to expand out to a hex or octo at some point.


#11

[double posted]


#12

That’s a smart idea. I am ordering the frame from hobbyking because I allready have a lot to learn about hardware and the .NET framework. Did not want to get into metal - frame building as well. But if I do have to wait weeks for everything to arrive I might just try building my own frame as well. Your frame got me thinking :-). And if I learn how to build a frame without too much weight I could better customize it as well (the hobbyking frame seems a bit small and I was allready wondering if the Fez and LiPo packs would fit.


#13

To do this you really have to go with carbon fibre. The raw materials for this are very expensive which is another reason I started out with a heavy aluminum frame. This will spare me some extra time to carefully plan out the final design before I make the investment in the carbon fibre materials. This recently got me thinking…

Does anyone know if it’s possible to have PCBs made on carbon fiber instead of fiberglass? Source?


#14

I’m prototyping an airframe made of fiberglass, reinforced with carbon fibre rods. i make triangular tubes and they are quite sturdy. and base made of fibreglass, it’s lighter than aluminium but heavier than carbon fibre. the good thing i can shape it the way i want it! the polyester resin is very toxic though so allways wear a mask with filter for these kind of fumes if you try it. i worked with fibreglass 5 days ago and it still stinks of polyester resin in the garage. so dont try this in your livingroom :wink:

@ ianlee74 im certainly not an expert on pcb making but i think most of the weight comes from the resin. with CF you’d probably be able to make thinner pcb’s though.


#15

Where do you get your material?


#16

from here: http://www.biltema.se/sv/Bat/Kemikalier/Polyester-och-Epoxi/Polyester/

but i guess it means nothing to you since it’s a swedish site :wink: , they have a store 25 kilometers from home so it’s easy to get my hands on. they also have fibreglass. there’s a local hobbyist shop around which carries CF rods, lots of indoor flyers in my town


#17

I’ve worked with fiberglass in the past and I know what you mean. However, I’m not sure that laying my own material and resin is the ideal way to build a quadcopter frame. It lends itself very naturally to a design using pre-formed tubes and cut fiber sheets. If you know a place to get similar pre-made materials in fiberglass then that might be worth persuing. I’ve never seen it though. A fab house that can laser cut either materials would be nice too.


#18

well i like making my own stuff, it’s fast, easy and cheap. there’s no standard parts i can use for the vectored thrust units on the VTOL airplane so that falls naturally to manufacture by myself. but for a quad, four tubes and a plate and it’s done. not much to fabricate unless you want it to look cool :smiley:


#19

Lol, tnx for the replies. A friend of my will recieve his 3D printer next week, I’d like to see how sturdy / heavy that material is. Perhaps I can design and print the frame.

I thought I’d have to worry a lot about earodynamics, vibrations, weight, etc. Considering that I’m a hardware and material noob that would be a potential extra obstacle, but since I still have to wait some time for parts to arrive I changed my mind and try and build the frame as well.

Could anyone review my potential order at hobbyking?

4x Master Airscrew propeller 12x6
4x Master Airscrew propeller 12x6 Pusher

(2x normal, 2x pusher and a spare set)

6x NTM Prop Drive Series 28-30A 750kv / 140w

(2 spare engines)

6x NTM Prop Drive 28 Series Accessory Pack

(think I need those on the engines to mount the propellers)

2x ZIPPY Flightmax 5000mAh 3S1P 40C lipo pack

(Lot of capacity and I think enough to power all 4 engines.
Hope that I get enough lift to add another pack to increase flight duration).

6x HobbyKing 40A BlueSeries Brushless Speed Controller

(2 spare in case I kill one or two, accepts a 2 to 6 cell lipo pack )

I allready have a separate lipo for the fez board. Intend to control the speed controllers from FEZ’s PWM. Just got an MotionPlus from someone and first want to try and use that as a IMU. Don’t have anything yet to sensor the altitude yet, but for version 1 I’m now considering a simple distance sensor and don’t need hobbyking for that.

I’m not going to use propsavers as I have a spare set. I do have lipo connectors available allready. I’m a bit worried about the engine choice because it’s a real cheap engine.


#20

I don’t have a flying quad, so don’t take any of this as real advice - just my opinion :slight_smile:

The battery pack is huge. It’s no use flying for 20 minutes 0 inches off the ground because it is too heavy… You can always add more battery packs, but you can’t carve half off an existing one.

Motors look fine - same ones I got from advice on other forums. They seem to be popular because they are indeed cheap for a 750kv motor. Again, I haven’t even started mine up yet, so I really don’t know.

40A ESC’s are overkill. At 140w, the motor will draw 12 Amps at 11.1V - so a 25A is plenty. It’s great if you plan to go bigger later and can afford the extra weight, but otherwise why bother? Also watch the specs of those ESC’s. The reason the Plush is popular is because it responds very fast to PWM changes - where some other controllers don’t. Don’t know the specs of the HK one.

Prop sizes I can’t comment on. I’m still trying to get into the black art of motor and prop matching.