MOTOR SPEED ERROR MAVIC MINI

[Davros007]

So, we can say, that this is problem of software, not props. Okay, let's see what happens next.

Or we can say the left rear prop is the most squashed one when stored...

 

[sar104]

It might though. Pure speculation on my part but what if the IMU error was below the threshold triggering an IMU recalibration message. So up we go. IMU reports in-flight out of trim, FMC responds, gunning one or more motors. No effect so it increases power until motor overspeed threshold is reached and triggers the warning message.

Somewhat supportive of this scenario are the are reports of the overspeed error occuring after a prop change, if I'm not misremembering that.

It could also be just a bad case of wind upsetting the trim. There are so many permutations it's hard to nail down without so much as a system diagram, let alone the code. Could be a combination of several errors, in fact I'd bet good money on that, the swiss cheese model strikes again. As a result I'm not expecting a fix anytime soon.

Right, but that's obviously not happening here, because the IMU is correctly reporting attitude. The rear motors are reaching maximum and the aircraft is not pitching forwards as it should. That's a thrust problem, not an IMU problem.

 

[rehkram]

Gotcha. Not triggered by the IMU then.

But we know the prop blades are likely under spec to be driven beyond some limit,TBD. Perhaps that limit is set too high (e.g. a hard-coded literal buried in the code, etc).

We know the motors are capable of it, that doesn't make it the correct thing to do if the hardware can't handle it.

Cause or effect?

 

[sar104]

Gotcha.

But we know the prop blades are likely under spec to be driven beyond some limit,TBD. Perhaps that limit is set too high (e.g. a hard-coded literal buried in the code, etc).

We know the motors are capable of it, that doesn't make it the correct thing to do if the hardware can't handle it.

Cause or effect?

It's been hypothesized, including by me, that the props might deform dynamically at high rotation rates, or at least be additionally deformed enough to lose their profile in flight. I replicated that, albeit not conclusively, in one of the tests. Interestingly, in the new firmware, DJI introduced the motor speed error but didn't reduce the maximum permitted motor speed. But either way - even if it is exacerbated by too high a motor speed limit in the firmware - it doesn't appear to have anything to do with the IMU.

 

[rehkram]

Right, I amended the first line of my previous post.

 

[Mr Curry Lover]

But what are you proposing the IMU has to do with this? The IMU data are what show that the problem is occurring, so that doesn't make any sense to me.

I'm proposing to try it, you have nothing to lose and a lot to gain. It worked for me and I'm using the latest firmware without any issues at all

 

[Mr Curry Lover]

It's been hypothesized, including by me, that the props might deform dynamically at high rotation rates, or at least be additionally deformed enough to lose their profile in flight. I replicated that, albeit not conclusively, in one of the tests. Interestingly, in the new firmware, DJI introduced the motor speed error but didn't reduce the maximum permitted motor speed. But either way - even if it is exacerbated by too high a motor speed limit in the firmware - it doesn't appear to have anything to do with the IMU.

I'm not trying to argue that it's down to something else. I'm not knowledge enough in the technology and how it works to put forward a good argument. What I am proposing is that you at least try what worked for me because you have nothing to lose and lots to gain. Why not just try it and prove that it's another way that doesn't/or does fix the problem?

 

[sar104]

I'm not trying to argue that it's down to something else. I'm not knowledge enough in the technology and how it works to put forward a good argument. What I am proposing is that you at least try what worked for me because you have nothing to lose and lots to gain. Why not just try it and prove that it's another way that doesn't/or does fix the problem?

I should clarify. The Mini that I've been testing is on the latest firmware and has a calibrated IMU. I can still reproduce the issue at will by using deformed props, and I can (and have) eliminated it by using good props. And the effects and results are clearly shown in the IMU telemetry that has been posted multiple times, not just by me.

I'm delighted that your current props are not triggering the problem (or the related error), but it was not an IMU problem.

 

[FoxhallGH]

There have been reports of the motor-overspeed error still being reported after change of a set of props. However, we are not told if that prop change occurred in the field immediately before the flight, or if the change took place the day before and the Mavic Mini was again folded and stowed in the case for 8 to 10 hours before being used.[??]

If a Mavic Mini is folded with the rear prop-set meshed across the body (as suggested by DJI), then that will immediately (and this can be observed) deform the props!

The reason for this is that the rear arms mount the motors with a (approx.) 5 degree outward tilt. The result of this is that when the rear arms are folded, and then their props are also folded and swung across the belly of the drone - they don't sit horizontally. They are pointing at +5 degrees relative to each other. Any attempt to mesh the blades to stow them (as per DJI instructions) will put pressure on the blades, as the tips will have to be pushed toward the body of the drone to slide under another blade tip. Only the blade on top would end up without pressure toward the drone's body - but that would have the blade under it, pushing upwards! A complete mess!! If you then add post-flight heat from the body of the drone into the mix, you'll have a set of prop blades all deformed away from the manufactured 'normal' in a hot environment that will soften the plastic then slowly cool to allow the blades to keep their deformed shape.

This is not an IMU or software problem ... It's a hardware stowage issue. ( and thanks to @Zbip57 for providing photo/descriptive evidence of this).

 

[Buzzfledderjohn]

Hello all. I am new to the forum due to having my first uncontrolled decent yesterday with motor error message. I purchased my MM in December, before Christmas. I was one of the lucky ones who was able to snag a Fly More kit from my local Apple Store. I have done about 30 flights without incident until yesterday. The drone spends an equal amount of time in the case vs sitting open on my desk, so what I'm saying is, it spends a fair amount of time in the case as I do not fly that often. The big piece of evidence I will share is that I have not updated the firmware since purchase. I was on the original firmware for controller, MM and batteries and while flying yesterday I received the max motor warning message for the first time. Tried to return to landing but MM would not respond to my direction commands and then began its decent into 100 foot oaks that border my property. I got lucky as I was about to fly out over the wetlands which I have done on many occasions. It weed-wacked several groups of leaves (no branches) which absorbed the fall to soft leaf-covered ground. Not a scratch and only the smallest abrasion on 2 props.

After reading here and other forums I looked at my propellers and the back are definitely deformed. Not from the crash, they are bent in the manner consistent with what has been shown here. No IMU or GPS warnings and to reiterate, on original firmware from product launch. For me, it seems the likely culprit is prop deformation, most likely caused by storage. I rarely fly in sport mode or high wind. There was no wind yesterday. I have ordered a full set of new props and have completely updated all firmware including batteries via the desktop app as per the instructions outlined in this thread. I will report back when props are installed.

 

[FoxhallGH]

Hello all. I am new to the forum due to having my first uncontrolled decent yesterday with motor error message. I purchased my MM in December, before Christmas. I was one of the lucky ones who was able to snag a Fly More kit from my local Apple Store. I have done about 30 flights without incident until yesterday. The drone spends an equal amount of time in the case vs sitting open on my desk, so what I'm saying is, it spends a fair amount of time in the case as I do not fly that often. The big piece of evidence I will share is that I have not updated the firmware since purchase. I was on the original firmware for controller, MM and batteries and while flying yesterday I received the max motor warning message for the first time. Tried to return to landing but MM would not respond to my direction commands and then began its decent into 100 foot oaks that border my property. I got lucky as I was about to fly out over the wetlands which I have done on many occasions. It weed-wacked several groups of leaves (no branches) which absorbed the fall to soft leaf-covered ground. Not a scratch and only the smallest abrasion on 2 props.

After reading here and other forums I looked at my propellers and the back are definitely deformed. Not from the crash, they are bent in the manner consistent with what has been shown here. No IMU or GPS warnings and to reiterate, on original firmware from product launch. For me, it seems the likely culprit is prop deformation, most likely caused by storage. I rarely fly in sport mode or high wind. There was no wind yesterday. I have ordered a full set of new props and have completely updated all firmware including batteries via the desktop app as per the instructions outlined in this thread. I will report back when props are installed.

Good feedback @Buzzfledderjohn - I think it's pretty obvious now that the Mavic Mini will do these crazy uncommanded descents no matter what firmware it's running. DJI's firmware 'enhancement' simply gives you a warning about motor overspeed - which - now we know why! - will give you the heads-up that you have a problem with your props.

 

[Buzzfledderjohn]

Good feedback @Buzzfledderjohn - I think it's pretty obvious now that the Mavic Mini will do these crazy uncommanded descents no matter what firmware it's running. DJI's firmware 'enhancement' simply gives you a warning about motor overspeed - which - now we know why! - will give you the heads-up that you have a problem with your props.

I got the motor overspeed warning on the original firmware so that must have been coded from the beginning.

 

[Exotic Blacklist]

Haven't used my mini in a while. Took her out today and I got the notorious warning. Seems to be the left rear prop. Ive done very few flights and no crashes. But I have the flymore combo. Here is the log attached. I received a few wind warnings. I was not too high or far away and in an open area. The wind wasn't bad at at all and the warning came as a surprise. I have been flying the air for about 45 minutes before I started with the mini. I flew it once after the firmware update and I got no errors them.

Appreciate your inputs as Im trying to understand this error logs.

 

[Buzzfledderjohn]

I also forgot to mention, after the crash I started the MM back up to make sure it was still functional and after hovering at 6 feet for a minute with no issues, I got overspeed and prop replacement warning for the left rear beeping esc after landing.

 

[apexbeat]

I am experiencing the same issue. It’s the left rear arm that is beeping. Flying is steady with no issues.

 

[apexbeat]

Yes

Yes

 

[Buzzfledderjohn]

I also forgot to mention, after the crash I started the MM back up to make sure it was still functional and after hovering at 6 feet for a minute with no issues, I got overspeed and prop replacement warning for the left rear beeping esc after landing.

New props came and MM is 100% back to normal. Flew 3 batteries with NO ISSUES. The problem is clearly storing the drone with rear props folded and compressed. I'm leaving mine out of case unless I need to transport. Not sure how to do that now. Not being able to fold it up and store safely during transport kind of limits its usefulness and purpose of being a compact drone. Is this happening on the larger Mavics or are the larger props more resilient?

The front props seem to be level so storing upside down may be an option. That would mean carving out the Flymore case or buying a new custom with foam that can be carved. DJI should really be informed and pressed on this issue, it is a bizarre design defect, not in the drone itself but the storage. I was lucky and did not loose mine but many have.

 

[vishalpmehta]

After going through all the posts on this thread, I've decided to just store my drone at home unfolded. I Will put it in the case only when going out with it. I can't think of any other solution to this problem at the moment. Well, I can always buy another case I guess.

 

[floyd]

Has DJI addressed this issue anywhere? On their website? On this website? In an article on another site? ANY RESPONSE FROM DJI, or just crickets?

 

[Xanadu]

I ve never had the speed error warning. After going through all the posts here and looking at the results from @sar104 's tests, I was keeping it out of the case unfolded on a desk. Just to test the storage, I experimented by placing it in the case and taking care of the prop's alignment as per DJI's instructions. Problem is, when moving the case (as if you were, for example, walking with it) I found that when removing the drone from the case, the props were misaligned.

I ended up giving away the FMC case and bought DJI's mini bag (to be used with prop holders). Not the best in terms of protection from impacts to the drone, but i just need to store it and transport it by car.