Pixhawk and some ESCs with Low KV motors. Pixhawk is not the problem. Problem is related to ESCs, Firmware and fine tuning.

I Found a solution to the problem; I changed ESCs to Tiger Motor ESCs and changed the signal to 200hz.

More tunning on PID required, will try Autotune, however quad flies great on stabilized mode.

It is now clear that the problem is not related to PIXHAWK but to the ESCs and signal processing by the motors . As previously mentioned by experts in this Forum, the signal for Pixhawk is always the same and the controller is not the problem.

7/27/2015

Ok I accidentally sent a message to all the group, but I meant to make a clear declaration about PIxhawk.

For some reason, no one has ever found a resolution with the motor sync issue with some ESCs,( in my case with hobbywing 40a and 60a and the sudden loss of control of the Pixhawk due to signal malfunction with low RPM high pole count motors ( t motor 4008 380kv).

I believe it is important to mention, that after tunning, changing ESCs checking motors, and a few minutes of Stabilize and Loiter flight mode flight, switching to Pixhawk has been truly disappointing, and everyone should no that it will take some time to reach the " industrial" reliability and end user friendliness of the DJI Wookong M in the Pixhawk.

I believe it will be possible, but when there are potential to date unsolved issues, the community needs to be aware of them, in order to create proper expectations of Drone Builders and developers.

Pixhawk is completely incompatible with hobbywing Pentium 60 a and Hobbywing 40a ESCs. It Flips on necessary roll adjustments, and the motors are completely out of synchronization, even after adjusting RC signal parameters, PID adjustments, ensuring good connections, and checking motors and ESCs.

I truly hope the solution will be using DJI or T motor ESCs; however, there is a lot of people that are likely to try Hobbywing, or other brand high Amp ESCs with large motors, and my message is:

DON'T try it!!

You will spend more money, parts and time and brain power than simply using another controller.

Firstly these comments are not aimed at anyone in particular, but if the cap fits then feel free to put the hat on....! I think a lot of you guys are missing an important point. It is NOT the PIXHAWK that has the issue, it is the speedies and Simon K firmware with high pole count motors, another important point is the WEIGHT of the props, if you are not using a very light prop then the motor has to work much harder to accelerate an decelerate the prop to control the stability, so it is a balance of tuning and stability vs control. If the motor looses sync then there is not a damn thing the flight controller can do about it! It still sends out the right signals, they are just not being acted on as expected.
Incidentally I run a coax quad with 28" props and 180kv tiger motors on 6s with Pixhawk flying between 13 and 20kg with out any issues.
If you don't understand that the Pixhawk is actually a very advanced autopilot and DOES need tuning, and are not willing to spend the time to learn the system to get the best out of it then maybe you are better off with another brand of autopilot. But please guys stop bagging the pixhawk ( and in effect, the developers..) because YOU don't know how to use it.
You may know how to drive but the first time you get in a formula 1 race car you would likely crash the car rather than make a very fast lap time..?
Again this is not a rant or shot at anyone in particular, just my observations. I do use ALOT of pixhawks in many different vehicles, and having been in the UAV industry for 20+ years a lot of you have no clue just how good this system is, especially when you consider the price.
All the best and good luck!
Steve

Replies

De Le July 23, 2015 at 7:56am

I have a T810 with Tator 4114 320KV motors and Hobbywing 40a ESCs and haven't seen any sync issues. I've flown several times and have tried to specifically reproduce the sync issues with rapid throttle changes and still no problems. I'm running an official Pixhawk on this one.

My previous setup a Tarot 680Pro with Tarot 620KV motors and 30a ZTW spiders V1 had no issues either and that was using a RTFHawk. When I put this setup together I also saw the reports of sync issues with the SimonK firmware, but didn't have any issues. When I had the Turnigy 30a ESCs on the rig however, I was able to reproduce the sync issues with ease. Since then, I've swapped out all the Turnigy ESCs with ZTW spiders and it's still flying like a champ.
- Pmarche > De Le July 23, 2015 at 2:04pm
  
  I just Finished first flight in stabilized mode, it was great!. Problem solved with T Motor ESCs. Had to do some tuning, but no sync problems, and no FLIPS
- Pmarche > De Le July 23, 2015 at 8:12am
  
  It could also be a problem related to T-Motors exclusively. I am going to try today with the new ESCs. I will also Install the Firmware Marc suggests on Hobbywing. I will let you all know the results.
  
  Again. my point on this discussion is not that there is something wrong with Pixhawk, I really like it, my point is that frequently, the signal incompatibility with some ESCs can cause unpleasant,costly in-flight surprises.
  
  Testing in the ground typically is done once an accident has happened. It should be done with tape, as seen in many youtube videos.
Mike Evers July 23, 2015 at 7:14am

I fly a TAROT-960, HobbyWing Xrotor 40A, U5 T-Motor, Pixhawk with 433Mhz and Foxtech 6S 10000 mAh.

Foxtech 5.8 Ghz 400 mW, Futaba 10C with XPS module, RFU PPM direct connected to the Pixhawk.

I fly super simple, drift, auto, Loiter, Alt hold.

So far I am very happy with this setup.

Mike.
Michael Burmeister July 23, 2015 at 4:14am

I have also seen many posts about this issue as well.

In my option the issue is that the ESC's just energize 3 or 4 coils on the motor and hope that the magnets react and turn. It then energizes the next set of coils in hope that it also follows. With no feed back its possible that it has sequenced past where the motor is and cause the motor to actually turn backwards since now the coils that are being energized are behind it.

So changing speeds quickly is not a good thing here and since the Pixhawk is able to do it in a blink of an eye and the ESC's will take it bad things are going to happen. Having a controller that slowly changes speed would be ideal here or having ESC's that don't respond very quickly would also work.

We need ESC's that are able to determine if the motor is keeping up.
- Steve Keep > Michael Burmeister July 23, 2015 at 2:32pm
  
  Hi Pmarche,
  I use 60a foxtech speedies with Simon k firmware, the foxtech props have proven to be pretty nice too. Very stiff and very light
Steve Keep July 23, 2015 at 3:28am

Firstly these comments are not aimed at anyone in particular, but if the cap fits then feel free to put the hat on....! I think a lot of you guys are missing an important point. It is NOT the PIXHAWK that has the issue, it is the speedies and Simon K firmware with high pole count motors, another important point is the WEIGHT of the props, if you are not using a very light prop then the motor has to work much harder to accelerate an decelerate the prop to control the stability, so it is a balance of tuning and stability vs control. If the motor looses sync then there is not a damn thing the flight controller can do about it! It still sends out the right signals, they are just not being acted on as expected.
Incidentally I run a coax quad with 28" props and 180kv tiger motors on 6s with Pixhawk flying between 13 and 20kg with out any issues.
If you don't understand that the Pixhawk is actually a very advanced autopilot and DOES need tuning, and are not willing to spend the time to learn the system to get the best out of it then maybe you are better off with another brand of autopilot. But please guys stop bagging the pixhawk ( and in effect, the developers..) because YOU don't know how to use it.
You may know how to drive but the first time you get in a formula 1 race car you would likely crash the car rather than make a very fast lap time..?
Again this is not a rant or shot at anyone in particular, just my observations. I do use ALOT of pixhawks in many different vehicles, and having been in the UAV industry for 20+ years a lot of you have no clue just how good this system is, especially when you consider the price.
All the best and good luck!
Steve
- Pmarche > Steve Keep July 23, 2015 at 7:54am
  
  By the way, what ESCs do you use with your COAS quad with 28" props?
- Pmarche > Steve Keep July 23, 2015 at 7:51am
  
  Steve, I agree with you. I need to learn details about the Pixhawk and how to tune it.
  
  However, I tried to make it clear, the issue is the signal from the ESCs and how is processed, and the Fact that in order to learn one has to make a costly mistake. I never stated the Pixhawk was low in quality or inappropriate. I only want to keep people from doing a mistake.
  
  For example, the quad lifts and flies good, but when you switch it to Autotune, it flips. If that happens when the quad is higher than 20 ft, it is going to cost some parts.
  
  That was precisely my point, it is not a Flight Controller that is plug and play, and people have to know it.
- Cala > Pmarche July 23, 2015 at 10:01am
  
  Plug and play?? forget it, is plug and read ! I don't recommend to people that want plug and play, buy a Phantom for that but there is a lot of possibilities with this board; it's for people who enjoy what they are doing.

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