There is a known incompatibility issue with Pixhawk FCs and DJI Tuned Propulsion Systems. And I have seen various solutions online in multiple forums, including this one. Problem is, some of those solutions are months and even years old and the info is incomplete. All I'm looking for right now is consensus on how to resolve this known issue. Here's some background on the subject.
I have two UAV's built on Flywheel 450 DIY clone kits, each with a Pixhawk PX4 running 1.4.1dev. Both fly fine with the cheap clone kit parts, but they are not very resilient. I have had multiple motor failures while in the air. I understand that's what you get when you buy cheap parts. So in an effort to upgrade I got a DJI E310 Tuned Propulsion System from the brick and mortar Multicopter Warehouse shop in Castle Rock Colorado (they are investigating this issue for me, as well).
The core of the issue is that the 420S ESC that come in the E310 kit are already "tuned", so you are supposed to skip that step, as stated here;
http://ardupilot.org/copter/docs/esc-calibration.html
So, I did indeed skip that part, and my UAV now flips when given enough throttle for take off. I triple checked, everything is spinning properly, motors and props.
Obviously the ECS need some sort of calibration, or the throttles have to have their PWM values manually set. I'm really not sure.
Now in investigating the issue online I see that there are a lot of people experiencing the same issue and they have come up with the flowing solutions.
- Stop using a Pixhawk and get a DJI Naza-M and be done with it.
- That solves the immediate issue of getting the UAV up in the air, but it doesn't take into account all my proprietary custom accessories that run off the Pixhawk. I have to be flying on a Pixhawk.
- Flash those 420s ESCs with firmware that works
- I have seen a couple of posting where they claimed this works. but when going to the link the link is missing, 404. What firmware is working, where do I find it and how do I flash it?
- Just get new ECSs with known compatible firmware.
- Sure, but I hard soldered in those ESC to the PDB and all that hard work, time and money will be lost... which is frustrating. There's has to be a simpler, less frustrating, solution.
- Manually set your throttle PWM values to 1000min and 2000max.
- I have seen this mentioned but I haven't seen anybody confirm that this solved their issue.
Is anybody familiar with this issue and know of a solid fix, something I haven't herd of, or one of the ones listed above?
Any practical insight will be helpful.
Replies
@Troy Apart from the extra cost (which sucks) getting bigger generic ESCs will give you a good solution. Just a quick warning if the bigger drone you're thinking of in the future will have low kv motors, then pick your new ESCs really carefully. Bigger/lower-kv motors are super sensitive to the ESCs timings and easily desync (read: fall out of the sky). I've had pretty good (but not perfect) results with blheli ESCs - most people swear by the hobbywing xrotor 20a/40a ESCs that are specially tuned for bigger motors for the best reliability.
In terms of the DJI ESCs, shame you can't quite get them to work to your liking. Sounds like setting the MOT_PWM values gets them almost working great. They spin at initialisation and when you get in the air flies fine, it's just taking off at low rpm that has a problem? Thinking back I had the same problem with the E300 ESCs - the quad (flamewheel f450) would flip on takeoff until I tuned the PIDS. For initial flights I had to use ch6 dial to set rate roll/pitch as detailed here:
http://ardupilot.org/copter/docs/ac_rollpitchtuning.html
If the PIDs are too low then it just won't compensate fast enough for the tipping and will faceplant into the dust, as you've seen. The thing with different props spinning up and different speeds is quite normal for various reasons - quad not perfectly level on takeoff, gyros/accels not perfectly calibrated, ESCs/PIDs not tuned perfectly, it's more noticeable on bigger motor/props.
Might not be your problem, but worth trying. The advantage of getting the DJI ESCs working would be confidence - they are the essentially what is flown in the phantom so the most tried and tested ESC there is. I and many others have had many hours great flying with them :) Don't be put off by a bit of setup work up front, it's only because DJI use a set throttle range unlike everyone else out there and don't support dynamic calibration.
Out of the four solution points I outlined in the original post, I used the third one, replace the ESC's, it's the only one that I know that works. The other solutions are not true solves, they are just work-arounds.
The DJI E310 kit ECSs simply don't work with Pixhawk... That is the answer.
Cheers!
_Mark
Since the issue is not well understood, I don't think I can trust a process that is simply, try this or try that. Without any confidence on a resolution to a problem not well understood, there is now way I am going to hang a $400 GoPro camera on a gimble on this Drone.
This is a real problem and I hope DJI coeerects the firmware issue with their tuned system ESCs. These are very nice systems, IMO just not compatible with Pixhawk based drones. If anyone wants a barely used DJI E310 system just message me. For now I am going to order 6 DYS BL40a ESCs. I know the 40a is way overkill but I am already planning and starting to acquire the parts for a larger drone and would like the ESCs to be big enough to handle the larger size motors it will require.
Any thoughts on the BL40a ESCs and them working with the Pixhawk and the DJI motors 2312 motors from the E310 kit?
Thanks to all those who tried to help.
Troy
Pixhawk refreshes at 400hz maximum, so changing RC_SPEED above that value won't have any effect.
Justin said:
For those who have a working E310 setup, what value are you using for RC_SPEED? A quick search shows E310 to work @30-450 Hz. Changed mine from 490 to 450 & then 400, nothing changed, but maybe there's a specific value that works.
my point is not mute just because you say so ! other posts with this same issue over the years with ESC since the pix hawk was released! You should not need to change MOT perimeters to get you copter to work it should work out the box with clean firmware install!
I have never heard of ESC issue like this with BiHeli firmware & Pix hawk! you can be DJI fan boy all you like E300 ESC still is not guaranteed to work and it seems your troubleshooting the wrong issue !!!!
I have run Pixhawk all available ESC on the market with and without issues, difference I find out what the underlying issue is , so I can help people having the same issues!
Fnoop said:
It might be 1) at low RPM. Important to note that pixhawk doesn't command (or have any knowledge of) RPM, it just outputs PWM value (essentially a percentage of thrust). At low PWM values ESCs don't always respond predictable or consistently - I was sitting here yesterday trying to calibrate some Afro ESCs (running blheli) that behaved really oddly in motor tests at low RPM but seem to fly fine.
It might be 2) if the ESCs are calibrated incorrectly within the FC firmware, or if the accel calibration isn't correct (might not realise it's tipping over until it's too late).
If it's 3) then you have bigger problems :)
4) Entirely possible :)
There are numerous parameters that can be changed:
MOT_PWM_MIN (1120)
MOT_PWM_MAX (1920)
MOT_PWM_TYPE (start with 0)
MOT_SPIN_ARM
MOT_SPIN_MIN
MOT_THST_EXPO
These will all influence low throttle behaviour. You can also graph your RCOU channels to look at the commanded output from the firmware/pixhawk when you throttle up.
I'm no expert in any of this, if you post in the ardupilot thread you're much more likely to get advice from people who know what they're talking about :)
Troy Gamm said:
This is, how do you say politely, um, 'not entirely accurate'.
Many people (including myself) use DJI ESC without a single problem.
Many people (including myself) use Simonk firmware without problems.
Many people (including myself) use blheli firmware with problems (also without problems, I run mostly blheli).
I've also just had to return a hobbywing ESC because it had problems.
This has been discussed numerous times in the past. Pixhawk is not inherently incompatible with any ESCs. ESCs just want a PWM (or more recently oneshot) input. Problems are usually setup or mismatched esc/motor issues.
OG said:
I am Glad you figured it out ! but the problem still remains and you can not help pinpoint what it is!
People who buy the DJI E300 kit with the intention of using it with the Pixhawk seem to have issues ! Compared to using Blheli ESC 0 issues 100% of the time! so your E300 do not work , your taking a chance going with them! so can you tell me what firmware your using on E300 ESC you have working ?
Alexey Dobrovolskiy said:
Hi, here you can see our drones with Pixhawk + ArduCopter + DJI propulsion systems:
https://youtu.be/zcUMGAYHno4 - DJI E1200
https://youtu.be/BJZMZL490Dg - DJI E310
All flights are fully automatic.
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