MultiWii

mahowik

2Hz is enough? How you testing? I'm usually do the following tests, to assest dynamic: 1) Enter to alt. hold with vertical speed (better to do it with baro clamped to constant value) - go up - flick switch - should stop - go down - flick switch - should stop 2) Set a set point 2-3 meters higher tha...

mahowik

2Hz is enough? How you testing? I'm usually do the following tests, to assest dynamic: 1) Enter to alt. hold with vertical speed (better to do it with baro clamped to constant value) - go up - flick switch - should stop - go down - flick switch - should stop 2) Set a set point 2-3 meters higher tha...

mahowik

My config quadX:
- turnigy 2209 28turn 1050kv 15A Outrunner
- props HK 9x5
- plush 18a
- mega1280 + itg3205 + bma020(bw 190hz + LPF 2..3Hz) + hmc5883 + bmp085
- accum 3S 20C 2200mah or 2650mah

Total weight ~800..900g

https://picasaweb.google.com/lh/photo/G ... directlink

thx-
Alex

mahowik

With normal ACC bandwith (10-25 Hz)? Bandwidth 190 Hz but ACC LPF ~= 2..3Hz static float accTempF[3]; ....... #define lfpFactor 0.987f accTempF[axis] = accTempF[axis]*lfpFactor + accADC[axis]*(1.0f - lfpFactor); accSmooth[axis] = accTempF[axis]; Yes! I see what you wanna to say! It (190hz) was too ...

mahowik

ziss_dm wrote:Easiest way would be to upgrade to BMA180..
It is supposed to be compensated as well as ITG3200..

What about ITG3205?

After 2-3 min outside, it was required to recalibrate gyro again because it became unstable in ACRO also..

mahowik

Hi all, Now in winter it so actual!!! Usually I consume at least one battery pack to tune my quadrX stable when I go outside. I have measured the ACC Z value after calibration at home and outside. The diff is about 17..19% with temperatere diff 30C... i.e. if acc_1g=63, it calibrated at home to Z=63...

mahowik

Today I have found out one more point related to alt hold stability
viewtopic.php?f=7&t=363&p=6831#p6831
It works at least for my config...

mahowik

One more note about alt hold stability... At the beginning I got a good results and stable alt hold with using accSmooth instead of accADC in getEstimatedAltitude(). And today I tried to use original version (i.e. with accADC) and have found out that is not working for me... It became very unstable ...

mahowik

dramida wrote:What accelerometer and software version are you using? i'll test your settings tomorrow, thank you.

bma020(set to 8g range: acc_1g=63)
software 1.9

most of all you should keep high VEL D... then play with VEL P and ALT P

thx-
Alex

mahowik

As for me, I got very good results +/-0.5..1m when it's not windy outside

PID ALT: 3.0 - 0.015 - 0
PID VEL: 5.0 - 0.000 - 45

mahowik

- The head/front will be remembered when you turn on the engines. So it means that you can turn on/off the "simple/head free" mode during the flight... That explains why I got so confused earlier today when I tried it. I thought it "stored" the orientation when the mode was enab...

mahowik

The devisor /64 was used to mask 6 (5+1bit "new_data") "unused" bits in data registers. With divisor /32 you relaying on the contents of those bits, which is probably not a good idea as you never know what can appear there. Hi ziss_dm, Yes, I know that for 8g the resolution is 6...

mahowik

A magnetometer is required for head free mode, right? Hi all, I have updated the first post of the related thread http://www.multiwii.com/forum/viewtopic.php?f=7&t=925 pls. post your feedbacks or issues there to have it in one place... HOW TO: - At first you need to have a magnetometer and acce...

mahowik

BTW: I've tried the new head free mode, and it seems to work just fine.... however, once you're used to 'normal' quad flying, this new mode becomes highly confusing again ..... you're still trying to control, as if standing behind the model.... I think it is especially usefull in a situation where ...

mahowik

So the conclusion for me is: VIBRATIONS. This would be the same conclusion you discussed. But what is the solutioon for that? Hi jevermeister, As for me set range to 8g fix this issue. I still have a little drift (I think it because there is low ACC resolution 64 LSB/g for 8g range) but it's accept...

mahowik

@Alex I think the common P (gyroData[axis]*dynP8[axis]/10/8) and D terms used both in level and acro mode are probably the most important terms involved in stability. I think the freshness of the level PI parts are less important. But it's very intuitive and it could be wrong, there is no math behi...

mahowik

Hi Theelectronicguy,

As for now MW doesn't support the sonar. But here a lot of guys wanna to have this

So you can be first!

Just FYI: As I know it's already work great in megapirateng project... you can look the details here http://code.google.com/p/megapirateng/downloads/list

thx-
Alex

mahowik

This is initialization for BMA: #if defined(BMA020) void ACC_init(){ i2c_writeReg(0x70,0x15,0x80); uint8_t control = i2c_readReg(0x70, 0x14); control = control & 0xE0; // control = control | (0x00 << 3); //Range 2G control = control | (0x03 << 3); //Range 8G control = control | 0x06; //Bandwidt...

mahowik

Hi, I did this, because I think it's more important to feed the PID loop with the freshest data. Doing this mod will feed the freshest data to the angle calculation function and not to the PID loop. If it's more stable, it's however interesting to understand why. Yes, for the rate PID controller it...

mahowik

I have found out small issue in computeIMU(). It seems that getEstimatedAttitude() uses "old" (not fresh) gyro values to calculate inclinations. Current code: .... if (ACC) { ACC_getADC(); getEstimatedAttitude(); if (BARO) getEstimatedAltitude(); } if (GYRO) Gyro_getADC(); else WMP_getRawA...

mahowik

Hi ziss_dm, Yes it's a good idea to avoid increasing of calculation time, but in case of current implementation the cycle time was not changed because the calculation inside of the annexCode() function, which is called from computeIMU() with constant delay... timeInterleave=micros(); annexCode(); wh...

mahowik

Alexinparis wrote:I've just included it in the last dev

Cool!!!

mahowik

@to all: Also I'm just wanna to promote new mode if not all aware about this.

It's already initially tested by some guys and have a good feedbacks.

viewtopic.php?f=7&t=925

russian version: http://forum.rcdesign.ru/f123/thread221 ... ost2970794

mahowik

Please tell me if this changes I made, make sence! As I'm also Alex and I have posted that changes. So I will reply to you You increased the LPF factor and increased the GYRO value for complimentary filter... And yes, these changes helps to reduce the drift but not resolve this issues at all unfort...

mahowik

that i will try to explore and post the results here. Problem sounds like this: i can read the x/y inclination (input variables) and i want to hold them in a limit value (desired position) by adjusting the output (motors throttle). Is working similar to PID control but is easier to process and unde...

mahowik

Hi matbogdan, Are you going to use Artificial Neural Nnetwork (ANN) for this? How you are going to "train" the copter? What will be the input data for this and how you will say to system that is correct behavior for that inputs? I mean that you should be verrryyyy good pilot to train ANN o...

mahowik

Hi guys!

Good news! Many thanks for your help!
I agree when it works it can be very usefull.
So I hope AlexInParis will not ignore to include this to sketch

thx-
Alex

mahowik

Small values - usually small inclinations. I agree but you know that ACC more sensitive for vibrations and this noise will be registered to small inclinations for IMU... then integrated etc... Can you explain again how incorrect transfer function of filter (due acumulative round-off errors) can red...

mahowik

Yes! For this Simple mode the declination not a problem because it uses the diff of heading and simpleModeHold angles. float radDiff = (heading - simpleModeHold) * 0.0174533f; // where PI/180 ~= 0.0174533 So you can try to fly with it p.s. I have updated the first post of this thread for "How t...

mahowik

Ok I forgot about this. But I think we can ignore small values. We need to setup correct filter, then we can use even small values because this values will show correct quad position. But what for that cases when you have a vibrations on board/PCB?! In this case small values it's noise... Just to b...

mahowik

Hmm why we should reduce precision? Maybe I miss something but I don't read all post about drift - most of new topics here is about drift and ACC the answer is in my first post of this thread http://www.multiwii.com/forum/viewtopic.php?f=7&t=926#p5843 But I'm happy now with my quads and just ma...

mahowik

hmmmm... and now I'm fully confused first theory - we should reduce the precision second one - we should increase the precision BTW I have tried to increase precision by increasing form >>4 to >>6 (from 16 to 64). accTemp[axis] = (accTemp[axis] - (accTemp[axis] >>6)) + accADC[axis]; accSmooth[axis] ...

mahowik

I checked it, and I did not experienced any error... it's linear... So perhaps your sensor is broken... So, bad news for me, but probably good news for you Could you try this mode? I tested this on the flight and it works In my config, but head/front is "swimming" because of this nonlinea...

mahowik

I do not understand that non linear error, sorry but can someone please give an explanation for dummies? it means when you physically rotate the copter (or PCB with sensors) for N angle, after IMU in GUI it shows N+D angle but not N... In my case if N=180 then D= +/-(20..30) degrees and depends fro...

mahowik

Hi Ziss, Yes, it seems you are right again If we take into account that accSmooth[axis] is float it will be the same LPF with high accuracy (like current 1.9). BUT why in this case marbalon's version helps to keep level and avoid the drift?! I have also made some test. I have added the cut condition...

mahowik

Hi guys,

Could someone test your mag for nonlinear error?
It means when you rotate the copter for 30/60/90/180 etc. IMU should calculate the same. Just check the diff of heading in GUI diff angles/degrees... probably I have broken one...

mahowik

Thanks a lot for the comments! I have already found similar in MegaPiratePlane // Declination correction (if supplied) if( fabs(_declination) > 0.0 ) { heading = heading + _declination; if (heading > M_PI) // Angle normalization (-180 deg, 180 deg) heading -= (2.0 * M_PI); else if (heading < -M_PI) ...

mahowik

You have to handle magnetic decliniation, if you want to use mag for anything else than heading hold. Take a look at the Arducopter code, there is a clean implementation in the compass library. It will be neccessary anyway, since gps guided flight also needs a precise compass. Thanks a lot! I suppo...

mahowik

I can agree with this but you miss second pass because when you are using int implementation with bit operations you miss small values, but if you analyze this example: ACC data 3, old value 0, lfpFactor = 0.27 if fist pass you will get 0*(1-0.27) + 0.27*3 = 0.81 -> then this will be converted to i...

mahowik

Hi Marcin, I have found out the same, that new ACC LPF filter doesn't work as required. As I told before in another thread: Yes, this LPF has good precision/accuracy for small input values, BUT these small ACC values are vibrations as usual... than that vibrations will be integrated and as result we...

mahowik

Hi Alex, I don't know about "carefree mode" in Mikrokopter... Yes, I have tested this and it's works, but no so great because my MAG has a big inaccuracy, e.g. if after IMU it has Nord in 0 degree the South will not be 180 degree but about 200-210... As I know in Canada the magnetic field ...

mahowik

Hi guys, I have implemented the simple mode for the bad pilots like me . I got the idea (but not the code ) from arducopter project. The main goal is: 1. Remember the YAW angle/orientation when you turn on the engines. 2.Then when you rotating the copter for yaw, it will know where is the "new&...

mahowik

Hi Shikra, Thanks for your idea! As I understand the main goal here to control the reaction speed to achieve necessary inclination. I'm sure you know but just FYI, as I have experienced, you can achieve almost the same by set big "D" (it's related not only for acro but also for stable mode...

mahowik

Hi guys, Good news! I have tried this fix (talking about increasing of acceleration range for bma020) yesterday and it work perfect, very stable with real ACC Z data (i.e. when TRUSTED_ACCZ uncommented). As I have very noisy/vibrated config I have set the following changes: 1. Set the acceleration r...

mahowik

Also I'm going to play with Nunchak. As it has analogue acc chip it possible to add the condensers with more capacity to filter unnecessary high frequency (vibrations).

mahowik

The ADXL345 works fine because in the Multiwii software the acceleration range is set to +/- 8G (register 0x31, 0x0B) and thus there is no saturation of the A to D converter with high frequency motor vibrations. Also the sensitivity is maintained to 256 LSB/g because Full_RES bit is set to 1 and th...

mahowik

I tested that but I am afraid that does not work, stillt twitches, might be even worse. I see the changes in I2C driver there. Probably it's a reason of this issue... from MultiWii_1_9: void waitTransmissionI2C() { uint16_t count = 255; while (!(TWCR & (1<<TWINT))) { count--; if (count==0) { //...

mahowik

Yes, it was clear

As I supposed (2nd way) above

Thanks in any case.
Alex

mahowik

ziss_dm wrote:Are you sure, that after changing range to 8G, the acc_1G is still 255? I think, it should be 63?

In case of BMA020 I suppose 2 ways can be here:
1. change the acc_1g accordingly, i.e. 127 for 4g and 63 for 8g
2. reduce the delimiter in ACC_getADC(), i.e. 32 for 4g and 16 for 8g

mahowik

Wow!!! Thanks a lot for the detailed explanation! This is the first time when we have a chance to really understand what is going on with Z acc axis. I will try the 4g/8g with my config. I hope it help to get Z more stable when engines is ON and reduce the acc drift. Only one question: in this case ...

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