M4+BLHeli_ESC+5g brushless+4x2.5

Info and discussion about the autonomous Micro FC, suitable for nanos, micros and mini multirotors

M4+BLHeli_ESC+5g brushless+4x2.5

Postby okallio » Mon Aug 31, 2015 1:12 pm

I'm building quad with 100g AUW and Quatos in mind. Planning to use following components:

M4V1
HXM1400-2000 (5grams/2000kv)
BLHeli 3A ESC
4x2.5 props
2s 450-600mAh

+FPV gear

I have build very basic frame with 170mm motor to motor using 6mm carbon tube as arms. Frame weight is some ~30g and it feels quite rigid. So total weight of the copter is now 95-105g depending on the battery used. I have done thrust measurements and 4x2.5 seems to give ~60g of max thurst. In my build I'm using 2s lipo to power motors. For M4 I'm taking power from the first cell of the same pack. As I'm on the diet I'm not planning to use expansion board. I have taken PWM 1-4 from on-board FET gates.

Are there any other builds in this category around? I would love to see parameter files. I have most of the stuff well figured out but some things still need clarification what comes to tuning this bird.

MOT_VALUE2T_A1 and A2 are clear but MOT_VALUE_SCAL needs some clarification. In one posting there was instructions to use the same value what is the maximum PWM when measuring thrust. And then there was also information to use this parameter in the same manner than in Labybird case i.e. to compensate thrust variations due battery voltage drop. So which one is the right way? Is there any other parameters needing tune when upgrading from Ladybird size? I attached print screen from current Quatos settings.

I have airframe geometry .xml file done and also .params generated with online tool. So these are clear.

Are there some other things to consider?

BTW. I upgraded from GroundControl from 1.5.x to 1.6.3 and noticed that old values are using commas but when trying to save it reports error. Do we haveto use point/period from now on? Do we have to generate new param files with this separator?

And then a small video of thrust measurement. I'm using BLHeli ESC controlled by Arduino. Arduino also reads thrust data from HX711 + strain gauge -combo and prints results thru serial terminal. These are then easy to copy-paste to Excel for A1 and A2 calculations.

https://www.youtube.com/watch?v=ChllAJh ... r_embedded

And sorry that I may have asked some of these questions in this thread "Quatos for 234mm Quad X? Thrust curve measurement?" earlier. I just thought to start my own thread not to steel the other one :)
Attachments
100G_Quatos.jpg
okallio
 
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Re: M4+BLHeli_ESC+5g brushless+4x2.5

Postby LPR » Tue Sep 01, 2015 9:13 pm

I wanted to build a quad like yours but I have not done it yet.

Your BLHeli ESC build will have parameters that are quite similar to quads that are using Kiss ESC.

Do not use parameters for the Ladybird because the parameters are for Brushed motors.

"MOT_VALUE2T_A1 and A2 are clear but MOT_VALUE_SCAL needs some clarification. In one posting there was instructions to use the same value what is the maximum PWM when measuring thrust. And then there was also information to use this parameter in the same manner than in Labybird case i.e. to compensate thrust variations due battery voltage drop. So which one is the right way? Is there any other parameters needing tune when upgrading from Ladybird size? I attached print screen from current Quatos settings."

The value for MOT_VALUE_SCAL is the maximum RPM your motor can run with your battery and ESC.

Quatos uses the A1 and A2 values to find the curve of the RPM to thrust response. Zero is the start of the curve and the maximum thrust that you can achieve is the end of the of the RPM to thrust curve.

I think that once Quatos has the curve of the RPM/thrust response it can calculate the PWM response needed for proper control your BLHeli ESC if the BLHeli is calibrated to starts turning the motor at near the same PWM value as the ESC 32 does 1100us and the RPM stops increasing at near 1950us.

Larry
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Re: M4+BLHeli_ESC+5g brushless+4x2.5

Postby okallio » Tue Sep 01, 2015 10:13 pm

Thanks Larry. I got her flying tonight. At the first attempt I had severe oscillations. For the second run I narrowed my ESC throttle range to your suggestion from 1100us to 1950us. Also I further lowered Correction rate to -2 and Thrust rate to -4. Prop torque was guessed to lucky 50. With these values I got my bird flying at some reasonable level. At least I now have a good starting point for further tuning.

I did my .XML file quite roughly so there is also something to tweak. I'm also implementing RPM read-out to my test rig so I can get RPM data also. For now I have done calculation using 0-100-200...1000 as numbers in RPM column. And in Quatos I have this 1000 as MOT_VALUE_SCAL. I think this is not the best way but at least I got a proof that she can fly :)

https://youtu.be/A7F1fQoCOEE
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okallio
 
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Re: M4+BLHeli_ESC+5g brushless+4x2.5

Postby LPR » Wed Sep 02, 2015 4:23 am

Nice little quad. Great to hear that it's flying.

I would guess that the maximum RPM those little motor can turn your 4 inch props is higher the 1000 RPM. If 1000 RPM is the max RPM I would think the motors will get hot quickly. Three inch props might work better.

A little more tuning, GPS antenna and your ready for a mission.

Larry
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Re: M4+BLHeli_ESC+5g brushless+4x2.5

Postby okallio » Wed Sep 02, 2015 6:28 am

Those 100-200...1000 are PWM steps in us from thrust measurement. I think those props are turning somewhere between 10-11 krpm at max throttle. After flight motors are barely warm for hand to touch so no worry. Those motors have kv of 2000 which is quite low for 2s. I would have wanted to use 3" and higher rpm but those gave only 40g of max thrust which would have been too low.
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Re: M4+BLHeli_ESC+5g brushless+4x2.5

Postby okallio » Sun Mar 27, 2016 7:17 pm

Have been flying this craft for a while now and been quite pleased with her behaviour. But today out-of-the-blue RTH stopped working correctly. I have telemetry thru Android GCS and it does say that RTH is activated. Also get home position announcement correctly. Checked channel monitor and three position switch on RTH/home position channel is working OK. However I only get change in altitude when switching to RTH. It corresponds to saved home position altitude ok but there is no change in position. Despite RTH not working position hold and way point missions are working fine?

Any ideas? Sorry for not posting logs but i'm afraid i don't have them due wrong settings in GCS.

If I recall correctly my FW is aqv7.1.1852-hwv8.5-quatos-ext_esc

BR, Oula
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Re: M4+BLHeli_ESC+5g brushless+4x2.5

Postby chschmid » Mon Mar 28, 2016 8:51 am

The only thing I can imagine without logs is, that your trims (or at least one trim) are not centered. If you are RTH and you touch nick or roll, RTH stops.

Cheers
Christof
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Re: M4+BLHeli_ESC+5g brushless+4x2.5

Postby okallio » Mon Mar 28, 2016 6:54 pm

Re-centering nick and roll channel did the trick. Thanks a lot for the tip!!!
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