A few questions after the first flight

[Count]

Hi,

yesterday I flew my X-Quad for the first time. I converted it from a KK-Board to a Crius Multiwii SE Board. I calibrated the ACC (also it looked good from the start, 0;0;509) and did not touch Mag calibration then. My two Aux switches are set for Baro and the other one for Level and Level+Mag. I edited config.h to use my Graupner Gr-12 ppm sum receiver.
I took off in acro mode and it flew really smooth and it needed only a little bit off trim (the KK-Board needed almost all of it on all axes, strange).
Then I got daring and switched to stable/level mode, applied throttle and... it landed on its back before even really lifting off. Luckily no props where harmed during this incident, because it is my last set.
To help you better understand my dumb questions, I also have a Tricopter with an Openpilot CopterControl (6dof).

1. What might have caused the flip?
I checked all sensor directions according to the FAQs (Mag seems strange). I checked the reaction of all motors in all modes in the Multiwiiconf GUI. Everything seems to be ok. Left back motor runs a little faster and front right motor a little slower, than the other two, but that might be the i-term while hand held.

2. As far as I understand, stable mode on multiwii means, self leveling with neutral stick input, otherwise rate mode, or am I wrong?

3. Is Mag mode only affecting the yaw axis? Does it make sense to put it on the AUX switch, the way I did?

4. What is the Mag sensor orientation for the Crius Board, it seems roll reacts on pitch, pitch reacts on yaw etc.

Thanks for your patience,

Count

[KeesvR]

I think your sensor orientations are not right, check this: http://www.multiwii.com/faq#How_should_ ... directions
You can change the sensor directions at the bottom of the config.H

//if you want to change to orientation of individual sensor
//#define ACC_ORIENTATION(X, Y, Z)  {accADC[ROLL]  =  Y; accADC[PITCH]  = -X; accADC[YAW]  = Z;}
//#define GYRO_ORIENTATION(X, Y, Z) {gyroADC[ROLL] = -Y; gyroADC[PITCH] =  X; gyroADC[YAW] = Z;}
//#define MAG_ORIENTATION(X, Y, Z)  {magADC[ROLL]  = X; magADC[PITCH]  = Y; magADC[YAW]  = Z;}

You can also download the latest Dev version, with this you can define the Crius Se and all sensor are selected the right way.
One note Dev versions can have bugs, so try on your own risk.

[Count]

Thanks for your reply,

I just found this link in another forum, I hope it is alright to post it here, perhaps it helps someone else.

http://www.quadframes.co.uk/MultiWii_1_9_Crius1.zip

Multiwii version 1.9 with definitions for Crius SE and Lite.

Just uploaded it and Mag looks much more reasonable now.

Count

[bill516]

You still need to trim acc, this is done by stick input. Motors dis-armed left stick to top left, right stick to forward, left, right, or back as needed. You can use the GUI to see what the motors are doing in acc mode, remove props to do this test. If you have got this right there should be very little difference in the motor rpms as you flick between gyro and acc mode.

http://multiwii.googlecode.com/svn/bran ... -57721.pdf

[m00se]

im having the same thing. on take off the rear motor doesnt spin as fast and it wants to flip.

[m00se]

i was reading some docs from another project the other night, and they said to make sure the handset is set to acrobatic mode, not heli.

i changed it and now my quad can almost take off without flipping and without accs. i havent tried stable mode yet, but the gyro only mode is hard to control, i crashed a few times.

even though in the display section of the handset i coudlnt see any mixes affecting channels it did seem to help it

[Dellow]

Have you calibrated the Mag as well as the accelerometer?
I found with the Crius SE board I had to calibrate the Mag two or three times to get it to read correctly.

[m00se]

i calibrated the mag several times, but i suspect that it isnt working,
when i do the stick combo out of the gui the arduino flashes as if it is saving something,

but if i do it inthe gui then nothing happens, i cant see anything on the gui ,

[bill516]

Have you tried it with the muliwiiwingui. I have tried my new imu in there and the readings are more stable than with the multiwii gui. If your mags not working you will see it as wingui as it has a nice compass on the screen.

[bill516]

Moose try a lower the rc rate than the .95 it defaults at makes it less sensitve.

[m00se]

bill, i meant to say that i claibrated gyro, not mag, i dont have a mag yet.
i will reduce the rc expo and see if it helps.

i suspect that the lipo isnt good enough, i am going to order a new lipo and some new props and try again.
the problem with the props is that it is my first rc model, and they have a hexagonal hole , the motor has a round hole so i had to drill the props, now they arent too well balanced and the motors vibrate. so maybe that is killing the gyro.... who knows

[bill516]

Right you meant calibrated the acc, gyros are calibrated at power on. When you calibrate acc you should see the traces drop to the centre line for about 5 secs then jump up to their default settings about 200 for z and 0 for x,y. After you calibrate acc, any trim settings you may have had for stable mode will be lost and will will need to re-trim for stable mode.

Rc rate is like a trainer pro setting to nearer to 1 the more pro you are, .6 is a good stable-ish setting.

Vibration is no good for a stable machine your gyros and acc cant keep up with it. By hexagonal hole do you mean it went all the way through as an hexagon or it was hexagonal on two sides with a smaller hole through the centre. If the latter, and the hole through the middle is the same size as your motor shaft then a prop saver fitting will take care of the hexagonal hole. When you get new props you should check them for balance anyway, I had some I had to do a great deal of scrapping on the rear of them to get them to balance.

[m00se]

the props are totally wrong, it is the latter of the two you mentioned, but the motors i have, have about 2mm of shaft and two screws comingout of them, and a rubber band to hold the prop on,

i just tried a little hop tied to the ground after lowering the value for STABLE, and it looks like its almost there,
but when full power is sent to the motors the front one still turns off, i am going to investigate the links above and see if i can program them without having to desolder them from the arduino again,

what doesnt make sense though is that only one motor turns off, and all were calibrated to the same levels, hmmm

[m00se]

ok after a few test hops,

i think that:

one motor cuts out on full power, so maybe the pwm signal is out of the range i calibrated the esc to, i will look into that,

very soon after starting to hover the front and left motors lose power, but dont turn off, this looks like the lipo, if i power off motors and start again a few seconds later once the lipo recovers, i get another 20 seconds of hover before the problem returns,

i have set all values to 2.2 in the gui and it looks ok with a .5 rc expo
progress is being made

[bill516]

Two screws and a rubber band sounds like a prop saver. Has the block with the screws got a tapered cone on it and can you move the block that the screws are in down towards the motor can to give a bit more shaft sticking out. This will help the motor/prop alignment better, or would have if you hadn't drilled them out, so long as the shaft is in that hole it will be centre or as close as the hole is to centre. If you find when you fit the prop that it is sticking up a bit push hard on the prop while twisting it on the saver block. Take it off and have a look at the prop you should see some wear where it has been rubbing on the block, you can use a countersink bit or a big drill to remove some of that material to get the prop to sit flush with the saver block. If you have too much shaft sticking out of the block you defeat the idea of a prop saver, just so the shaft is about level with the top of the hole in the centre of the prop is about right. You should find that if you grab one prop blade and lift it up the prop will come off the saver and hang to one side unless your rubber band has come off.

Swop the suspect motor for one of the other ones, if the fault moves with the motor the motor is suspect, if not there might be a problem with the esc. If your only getting 20 seconds of hover then either the battery is not big enough or as you suspect its had its day.

What do you mean you have set all values to 2.2 in GUI. Do you mean the PID settings, if so you have wasted your time as you are not ready to use the PID settings yet, just leave them set to default. You have to get your copter flying and trimmed in gyro only mode to start with, acc off, trying to do it any other way will not be successful. The guide by Shikra in the FAQ is a good guide to start with, although the steps are a little dis-jointed, read through it, it works.

[m00se]

i will try modding the other props i have to see if i can get them to fit better, i have modded the others so that sit as low as possible, i thought that it looked ropey when they fell off to the side,

i have tried moving the motor esc combo from front to back and the fault moves with it. so i guess that one of them is the problem

although im not reay to rule out the sensors yet, because i have noticed that when i pull back on the pitch, the rear and the right motors slow down, as if the cuad is in X mode although i have it in P.

also when i turn off the accs the quad takes a very fast and violent dip forwards. but with a lot of power. if i put the acc back on then the cuad tries to level out again.
i wonder if there are some problems with the nk and wmp, although i used the with my wii for at least a year with no probs

[bill516]

Spot on one of them has a fault, now you need to separate them and see which one.

When you turn the acc off you are then flying on the Tx trim, that is why I said you need to set that up first, you can fly without acc but not with an untrimmed machine. Setting the Tx trim takes into account any discrepancies there may be in your build or material composition. Properly trimmed there should be no change in attitude of your machine when you turn acc on or off. The GUI will show you if you are are in the correct model quad or X when you tilt it, alternatively rotate the sensor 45 deg.

[m00se]

the gui shows a traditional cuad. and it tilts right with the sensors, so orientation must be okay.
i cant play right now because a wire came off last night and i have to take it back to work to solder. but, when holding it in my hand loosely, every 15 seconds or so it has some really violent and random direction changes,

i genuinely think that i have a combination of motor esc and sensor issues.
i guess the solution is to order another couple of motors, and to test the code on the ardupilot board i have.

although i really am only making the cuad because i want to say to people, yeh i put motors on a wii controller, which might be what it ends up being housed in, all the elecs back in the wii controller case, hahaha

[m00se]

Spot on one of them has a fault, now you need to separate them and see which one.

When you turn the acc off you are then flying on the Tx trim, that is why I said you need to set that up first, you can fly without acc but not with an untrimmed machine. Setting the Tx trim takes into account any discrepancies there may be in your build or material composition. Properly trimmed there should be no change in attitude of your machine when you turn acc on or off. The GUI will show you if you are are in the correct model quad or X when you tilt it, alternatively rotate the sensor 45 deg.

bill, i changed a motor and now it looks like it has stopped cutting out,
fingers crossed,

[bill516]

I have read of motor doing that and it came down to an iffy connection under the heat shrink where all the wires come together, worth a look if it is and you can fix it you have a spare motor, if not then nothing lost as you couldnt use it anyway.

[m00se]

that will be on my list of things to do, hopefully i can get a spare,

it sounds feasible, it is the first motor that i used to test thrust , i had it on a set of scales with a heavy weight and at full power it came off , i shut it off almost instantly, but it could have been damaged,

if i cant repair it, i am going to hook it to my 12v bench supply at work with my spare esc and a servo tester and make a fun looking office fan

[bill516]

You can always re-wind the motor there are how to on the net. I've got some wire to do a motor but they are all working at the moment so I'm a bit reluctant to have a go, plus all the other things I have to do.

[m00se]

i have looked into that in the past, you just wind every third pole with the right amounts and then join one end of all three windings up, I havent had to rewind a motor in work yet, but im sure i will one day, so i can learn to do it while being paid:)

i thought about re winding them to change the torque and max rpm specs, considering they are so badly wound from the factory i might end up doing it,

but i have to make it fly first. flight without accs is very hard, i acheived a mas flight of about 5 seconds yesterday, and then ended upside down, Im thinking of defecting to the diydrones setup since i have it sat on my desk, but i would rather triumph with the Wmp and nunchuck just so i can tell people i modded the controller, it sounds cooler than having spent 300 euros on a premade bit of kit

[bill516]

You could always ditch the WMP and get one of those all in one IMU's, the one I have is so much easier on vibrations than the WMP setup, but if you crack the WMP setup you will know what your talking about.

[m00se]

well , i have a nice all in one IMU; and i might switch to it, but i couldnt resist taking the wmp setup out for a test flight, I have flown it a bit in the house and the drift is too much to handle in a small room, so i took it out to the field, and , , , ,, , after only about five mins in the air, one of the HK motors has broken down,

I had several undesired ladnings, but nothing heavy, they were all in long grass and i have some protection rods perturding out of the arms to protect the motors,

at first i thought it was wind making it always drift, but it got worse, and now i cant take off and im back to the same situation of one motor that cuts out under load,

stupid cheap pieces of hobby king crap

Does anyone know of any good motors that will work with 12A escs and dont cost a small fortune ? I have one more new HK motor, but im certain it will end up broken in no time,

the good news is that i had it in the air up to about 15m and managed a little bit of controlled flight with just the WMP, so if i change the motor and put the nice IMU in it then i might get some fun out of it

[bill516]

With HK motors its the luck of the draw, in fact anything from China is like that unless its been around for a while and all bugs have been ironed out, I have some 2213n motors that have been slammed into the ground a few times and they are still going. You must realise that these motors are made by women who sit around winding motors all day for a pittance the more they do the more they get paid, so they dont care what it looks like as long as it is what the have been told to do. The up side is that they are cheap and now HK have a UK warehouse you wont have as long to wait, well when they get all the stock in and postage rates sorted out.

You got it off the ground ad in the air for a while so your going in the right direction. Dont remember if we talked about bullet connectors before but you could always solder them to rule out any intermitant connections.

[tovrin]

bill is 100% correct, i removed my bullet connectors and the weird 'bounce' issue i was having was instantly gone. i will forever solder my connectors now, my next step will be to flash my ESC's the aeolian brand seem to have limited number of steps, making altitude hover near impossible.

[m00se]

the ones i have dont come with bullet connectors, so i have them directly soldered,

I was thinking about what happened, and the battery went low, the left motor must be set to turn off not slow down like the rest because it just stopped and i had a 45 degree slide down to earth,

after that i made one more flight with the new battery before the motor went, so i imagine that the slide landing is what did it, still the problem looks like it has been resolved,

i have given in to temptation and installed a full DIYDRONES setup, i had it knocking around and since it has gps and xbees it seems stupid not to use it,
i wanted to have to geek factor of using the wii hardware, but i cant keep breaking things, and the DIYDRONES took about an hour to instal calibrate and have almost perfect flight first time,

the quest now is to see if multiwii works with that hardware, although im not sure it ifs worth it because the mission planner from diy looks very promising