karla

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Re: Cliff Diving PID Setting
« Reply #60 on: May 26, 2018, 03:16:31 am »

jcg1541

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Re: Cliff Diving PID Setting
« Reply #61 on: June 01, 2018, 05:29:17 am »
Sorry I have been distracted by the search for abandoned tall buildings. I am sure I would have dived many decaying skyscrapers of Detroit if I lived there. Here in the north east, I found the rusting old Ramington Arms munition factory with a tall smokestack. See attached photo. I passed by it over the highway just this memorial weekend. Guess I will dive it in the next few weeks.

karla

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Re: Cliff Diving PID Setting
« Reply #62 on: June 01, 2018, 10:14:33 am »
 :P

jcg1541

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Re: Cliff Diving PID Setting
« Reply #63 on: July 01, 2018, 05:25:12 pm »
Just a question: are you using TPS (Stabilization->Advanced->ThrustPIDScaling)?  Mathematically at least, whenever you double the head speed, you should halve the PIDs, etc.  So if you are using a throttle controlled variable head speed, this will keep the PIDs in sync with the head speed.
That was an excellent question. I have tried it today, and the result is a dramatic improvement. Previously either the ascending was very slow or too much vibration to be shown on video. Now the punch up is forceful, yet no oscillation anywhere in flipping or diving. The ascending is 28 seconds, then the 9 second dive follows,

.  And the extreme scaling down is between thrust 75% toward 100% . The flipping and diving thrust is below and right adjacent to 75%.
The curves are attached in pictures.
« Last Edit: July 03, 2018, 03:14:53 pm by jcg1541 »

jcg1541

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Re: Cliff Diving PID Setting
« Reply #64 on: September 16, 2018, 01:47:28 pm »
This is a tribute to Boston Marathon spirit. We lost citizens, and we lost limbs. But our spirit is not hurt one bit.
The takeoff weight of this drone is under 250 grams. I have the PIDs for quadcopter-like diving now,
http://nocomputerbutphone.blogspot.com/2018/09/converged-iot-drone-build-notes.html
. FAA rule is that if you are within 400 feet next to a structure, your altitude limit is based off the top tip of the structure. The dive is about 600 feet from the top of the tower to the church spire. The following video will be deleted after being viewed by this forum.
« Last Edit: October 25, 2018, 07:43:21 pm by jcg1541 »

karla

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Re: Cliff Diving PID Setting
« Reply #65 on: September 17, 2018, 11:30:54 am »
Well done

jcg1541

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Re: Cliff Diving PID Setting
« Reply #66 on: November 24, 2018, 01:10:03 am »
I might have run into the Vortex Ring State now. I have been trying to push the limit of my tail motor ESC to the point of failure by forcing full throttle torque at the bottom of my dives.

2 incidences . The first dive starts at 1:00 mark.  In either case, maximum throttle-pitch was applied at least 2 seconds before the touch down crash and the craft crashed with full throttle-pitch still in effect. The pull-up deceleration appeared weaker than with "regular" pull up moderate collective pitch.


The solution is to just go back to the more moderate pull-up that we instinctively develop.

I have a diagram my reasoning of the vortex , which is a stall vortex due to wind direction change with the dive itself, in attached picture.

I believe this happens to quadcopters too, just that no one tries to push the limit of the tail ESC because there is no tail motor there.

I have found my tail ESC that allows the the vortex ring fault to occur before the ESC fails.

John


John, just an idea.

You could consider doing the dive in a different way.
Do it fully upright, horizontal and apply negative collective.
You now have a fully 3D heli setup right.

You will not have any issues with 'retreating blade stall', not even for the tail rotor since it spins typically 4 * faster than main rotor.
However, you will likely run it to another issue, Vortex Ring State.
But, I was just thinking this should just be initially, and then you can push through it, descending much faster.

This style of dive will give same speed and sensation as 40-50 m/s but you can control the descending speed so it keeps under control.
This will allow you to use Attitude stabilization for simplicity but more interestingly, a much longer dive, like any distance you prefer, really.
Move the camera to a downward position, or have two cameras, or maybe a camera that can tilt.

This is the problem of Vortex Ring State and how to recover from it. But you don't want to recover :)



But very little or no research has been done if you want to push it faster downward.
No one have ever had an interest doing that.

Fascinating John!
« Last Edit: November 24, 2018, 11:35:47 pm by jcg1541 »

Re: Cliff Diving PID Setting
« Reply #67 on: November 24, 2018, 01:27:52 am »
It could be a simple matter of the main blades stalling out if you pull out too sharply; just like a fixed wing.  High angle of attack associated with backwards flow through the main disk / high G's.

karla

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Re: Cliff Diving PID Setting
« Reply #68 on: November 26, 2018, 01:32:33 am »
I am not sure, but I think this looks like another trap for helis called 'settling with power' (main rotor stalls).
It looks like your heli is slowing down the descend but just do not have time enough to stop before it hits the ground.
That is different from Vortex, since you will just keep falling without slow down.

Anyways, it do seem you really reached the limit now :)

This guy from Canada is trying to separate the two things.