Horrendous Jello

BrianRHoff · Oct 22, 2015

Help!

The Editor · Oct 22, 2015

BrianRHoff said:
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Help!

Were you using an ND filter?
Have you balanced your props?
Do you have excessive free play in your motor arms at the T-Joint?
Personally I would not want to fly that close to a high power microwave Fresnel zone!
You can get in deep doo-doo for flying the Hollywood Sign!

Machoman · Oct 22, 2015

Was interesting to see how it really looks there.

- check the propellers play
- check if you have the same jello if you put the camera only foward
- change the vibration dumpers

change brake to 70%
set everything in expo to 0,2

play with gain settings

Most jello happens when you brake or change direction however I noticed you get the arms in the picture even at very low speed this means you put the camera extremely high or your Inspire makes very sudden movements.

Redtazdog · Oct 22, 2015

Good chance you got above the 400 ft elevation from the point of take off to get that video, how did you do it as I cant get over a **** 600 ft hill on my own property without hitting the max height limit.
maybe the wind was adding to the jello effect as it does get breezy up there.

The Editor · Oct 23, 2015

Machoman said:
Was interesting to see how it really looks there.

- check the propellers play
- check if you have the same jello if you put the camera only foward
- change the vibration dumpers

change brake to 70%
set everything in expo to 0,2

play with gain settings

Most jello happens when you brake or change direction however I noticed you get the arms in the picture even at very low speed this means you put the camera extremely high or your Inspire makes very sudden movements.

I am sorry but this is wrong information...

Exponential adjustments will have zero effect on jello during flight. It is there to desensitize the throw around mid stick by altering the control input from a linear 'curve' - that's all it does.
Playing with the gain settings IS DANGEROUS ADVICE to give out to somebody unless they have an understanding of what they do and why. You are altering the PID tuning of a closed loop feedback system - these should not be altered unless you understand the consequences.You can end up making your aircraft unstable in flight and difficult to control.
The dynamic breaking adjustment similarly should only be adjusted if you know what the function does and why you are adjusting it. A user could drop the figures down to your quoted 70% and then suffer a crash because the aircraft does not come to hover upon releasing the sticks in the same distance it did previously.

Please do not give out advice which can be dangerous to inexperienced pilots.

jebsmith · Oct 23, 2015

What is your shutter speed? Are you using a ND filter? Looks like 60fps to me.

Machoman · Oct 23, 2015

The Editor said:
I am sorry but this is wrong information...
Exponential adjustments will have zero effect on jello

Playing with the gain settings IS DANGEROUS ADVICE

A user could drop the figures down to your quoted 70% and then suffer a crash because the aircraft does not come to hover upon releasing the sticks in the same distance it did previously.

1. This information is not wrong. I dont have jello like in the shown video but there are situations where i got it so I experimented very long with all possible options. I could not get it 100% away but I could reduce it. The main cause is unsmooth movement. In the shown video you see the biggest jello when brakeing from high speed in minute 2:20.Jello is caused in shaky situations and putting the expo to 0,2 makes it easier to fly smooth. Putting expo to 0,8 you cannot start or stop a smooth movement and that increases jello.

2. Quoting DJI-Dave from the official DJI forum on August 6th 2015 playing with gain settings is not dangerous with the Inspire: "No it will not crash or flip the Inspire with various gain and expo settings. We have limited those setting to avoid that."

3. The 70% brake setting causes a 5m brake way out of full speed. It still makes a heavy brake and reversal movement. If someone flies that close to an aircraft the drone will already be affected by the wind long before and crash. If it would be dangerous DJI would not have allowed this setting. DJI are cowards they sure allow nothing in their software which could be dangerous for any reasons.

The 70% brake setting in combination with 0,2 expos is one of the most efficient settings to fight jello AND avoid to get legs into the picture when using the camera higher then -1. Its the reverse movement of the brake command which is the unsmoothest movement the Inspire can make. You can even see the smoother movement with 70% brake in the simulator.

There is one more thing. I had most jello problems flying diagonal back with speed over 35 km/h and then brake or change direction while putting the camera to a side angle fully exposed to the wind. I still did not find a solution for this but flying forward and putting the camera to back with above settings eliminate most jello even at highest speed.

PS: I like to fly with short shutter speeds and I never use ND filters unless there is something like snow. So my effort is to get out jello under this conditions.

The Editor · Oct 23, 2015

I am sorry but you clearly have absolutely no idea what you are talking about and are giving out erroneous information.

You clearly know nothing about integral wind-up, PID tuning, closed loop feedback systems or even the cause of rolling shutter or you would not make statements like "The main cause is unsmooth movement". I nearly deleted your post outright since it contains so much bad advice in there

I cannot stop you posting such utter rubbish on here (well I can, I could simply delete your posts) but I will leave it up to individuals who's advice they wish to follow.

Anyone reading this thread please be advised that:

1. Altering your gains without an understanding of what and why you are doing so will dynamically affect both the aircraft's stability in differing flying conditions and will alter its characteristics as to how it actively stabilizes and adjusts its attitude as well as altitude hold.
2. Dynamic breaking can be adjusted and will alter the force at which reverse emf breaking is applied through the esc's - however, it will dramatically change the 'stopping distance' once you let go of the sticks and this can catch people out if they are inexperienced or have not made several test flights and got used to their breaking adjustment.
3. Rolling Shutter (Jello) can not be stopped by dialling in an exponential value into the remote control. The effect of an expo adjustment is to make the centre stick movement non linear. It effectively 'dumbs down' the central part of stick travel - It has zero to do with alleviating resonant frequency or high frequency vibrations transmitted through the airframe or vibration of the camera caused by wind which coupled with higher shutter speed emphasize the jello effect during fast lateral movement.

I would urge all Inspire owners to think very long and hard before adjusting their gains or dynamic breaking since your flight characteristics WILL change. The SIM is OK for what it is but it is not 100% reliable for simulating all flight physics.

Machoman's advice to "Play with the gains" is irresponsible and I do not advocate that line of action especially if you are searching to alleviate/mitigate rolling shutter/Jello

I would hope by the sheer amount of advice I have given out on this forum that I have demonstrated I have a reasonable understanding of not only the Inspire but multirotor platforms in general. At the end of the day, everyone has their own Inspire and they are free to follow what advice they want to but please be mindful of the above.

Mike Mas · Oct 23, 2015

Find my post on this forum on installing two small tie wraps on the front mounts this will stop 90 per cent of your problems add battery life and save your motors. The original inspire mount is broke.

Turn the goofy brake feature completely off it is absolutely worthless why would anyone want to stop a drone and have the machine react so abrubt. This is a nightmare feature that some genius dreamed up and more than likely never flew a helicopter.

The Editor · Oct 23, 2015

Mike Mas said:
....Turn the goofy brake feature completely off it is absolutely worthless why would anyone want to stop a drone and have the machine react so abrubt. This is a nightmare feature that some genius dreamed up and more than likely never flew a helicopter.

I'm afraid by making that statement you have demonstrated you do not understand reverse emf breaking and its benefits which first appeared on the Freefly systems.

Your zip tie mod, I can live with since it would alter the damping on the gimbal mount and thus could prevent vibrations/lateral movement and/or alter the resonant frequency of the set up for people suffering rolling shutter.
I cannot accept you get 2 plus minutes of extra flight time though... that s a stretch too far. But hey... if people want to try it, who am I to stop them.

Mike Mas · Oct 23, 2015

Do the math - I'm right on the money.

Machoman · Oct 23, 2015

The Editor said:
3. Rolling Shutter (Jello) can not be stopped by dialling in an exponential value into the remote control. The effect of an expo adjustment is to make the centre stick movement non linear. It effectively 'dumbs down' the central part of stick travel - It has zero to do with alleviating resonant frequency or high frequency vibrations transmitted through the airframe or vibration of the camera caused by wind which coupled with higher shutter speed emphasize the jello effect during fast lateral movement.

All you say here is correct and of course I also know this but your conclusion is wrong.

While a 0,2 expo does not directly reduce jello - you explained why I didnt because this doesnt help here - it still reduces it because of the smoother start and stop while with a high expo you will get sudden harsh movements because it will start and stop very fast. You cannot brake slowly with a high expo.

Mike Mas · Oct 23, 2015

Expo has absolutely nothing to do with the camera at all -it only reduces cyclic travel at the center of stick travel.

Machoman · Oct 23, 2015

Mike Mas said:
Expo has absolutely nothing to do with the camera at all -it only reduces cyclic travel at the center of stick travel.

Does a very harsh brake affect the vibrations to the camera? And does expo affect how it brakes? Unless you put the stick from maximum to middle in a second of course but if you do this you dont need a expo setting at all.

Mike Mas · Oct 23, 2015

No brakes have no effect nor have anything to do with camera vibrations - Brakes are only brakes and only effected by the brake slider for response - Turn the brake i.e. to the lowest position.

Expo does not reduce the amount of control of the cyclic it only slows the response at the center position of the sticks.

The brakes on the Inspire are about as useless as a screen door on a submarine!

The Editor · Oct 23, 2015

Machoman said:
Does a very harsh brake affect the vibrations to the camera? And does expo affect how it brakes? Unless you put the stick from maximum to middle in a second of course but if you do this you dont need a expo setting at all.

Well now will you accept you are wrong?

Machoman · Oct 23, 2015

Mike Mas said:
No brakes have no effect nor have anything to do with camera vibrations

I am sure you didnt even look the video in the initial post. So in minute 2:20 its not the brake causing the jello?

The Editor · Oct 23, 2015

Machoman said:
I am sure you didnt even look the video in the initial post. So in minute 2:20 its not the brake causing the jello?

No, I didn't think you would. Just won a bet with myself.

Machoman · Oct 24, 2015

Do the expo settings not also change the speed at all?

Mike Mas · Oct 24, 2015

Expo has no effect on speed i.e. full forward cyclic with or without expo will be 100% travel - all expo does is de-sensitize the centers of the sticks travel. This allows you to move the stick further or more at center without abruptly changing the drones stable condition,

If you look at the graph provided in the rates expo setting on the DJI Go app - for the Inspire or P3 you can see a graphic representation of what's happening - the center travel position will take more stick movement then it will at the end of travel.