How To Analyse Jerks

Please confirm: do you mean shock or shunt measurements?

Jerk is something different and not really used in a technical context.

what i understood is that jerk is the derivative of acceleration over time. So if i measure the change in acceleration, would i be able to calculate jerk.

https://en.wikipedia.org/wiki/Jerk_(physics)

Something like this?

There was some good information in the old thread. But you did see that didn't you?

Terrible to read, but I get the gist. Thanks.

You need to pull the bottom RH corner out to make it as large as CR4 will allow!!

A psychiatrist's couch might be the best tool for this.

If he gets it to work, he can try it on me!

Quite right! GA

This conversation has me re-thinking the mounting on my quad-copter. It has a 6 axis accelerometer in it for stabilization and must be affected by vibrations from the props and motors. I wonder what frequencies I'm dealing with and what mounting technique I might employ. I think there are some tests to be made...

With the low mass requirement of a quad-copter it maybe easier for an analog filter to be placed between accelerometer and electronics than to stiffen your frame. This will induce some lag in your response time but properly designed only fractions of a second delay.

Also, if you program it to ignore signals below a certain threshold, you'll effectively dampen the vibration out, you just need to make sure the threshold is set tight enough to allow actual acceleration to be read while discounting the vibration.

Wait, 6 axis, that means three paired of opposed acceleromiters, it'll read both directions of any vibration, so they should cancel out, with the worst case being a 'beat frequency' that would make the copter bob slowly in still air. We're already used to seeing 'bobbing in midair' to mean hovering, so programming that out would make the copter seem 'unnatural.' (Ref: http://tvtropes.org/pmwiki/pmwiki.php/Main/TheCoconutEffect )

Thanks guys. My controller has the accelerometers built-in, and the setup software does filter the basics and it provides a graph as well, but I always do the setup with the props off, and so I'm going to try different mounts and bolt the copter down so I can record the effects with the props on and at speed.

We've been going through all this, and you haven't even measured the system response on the default settings under power?

Pardon me, but I need to do this: <strongman facepalm>

Quad copters!

I hate 'em.

Some Many of the so called "pilots" have no respect for privacy or personal safety!

Twice last week these IDIOTS grounded air tankers fighting fires in California.

How stupid can they be. Incredibly stupid, I'd say.

Obviously just an impersonal rank, not directed at you personally.

Air tankers were operating in the area?

Shouldn't that have made it 'restricted airspace?'

And shouldn't there be a regulation authorizing 'decommissioning⁽¹⁾' of unauthorized UAVs in restricted airspaces?

Notes:

1. Also known as 'Blasting the annoying gits out of the sky, and not feeling bad afterwards for enjoying the shooting too much."
   

The jerks that fly these don't care about restricted air space.

Hence the second part of my comment about being allowed to take a shotgun to unauthorized UAVs.

I'm with you 100% on the shotgun as a cure for unwanted crones.

Along with a hefty fine for the owner/flyer.

I do not consider these people as pilots.

To say nothing of their owners.

The juvenile idiots at Gizmodo called this idiot and awesome guy.

An Awesome Guy Made a Flying Drone Armed with a ...

Sure, I'm an old man. But this $hit scares me.

It was restricted airspace. Here is a report from last month. Here is another report from last week. The drone and remote aircraft problem is real.

Well, just for the record, I'm setting it up to race FPV. The next one is going to have telemetry and sensors to monitor the power to to the rotors and the GPS to fly straight up and hold a particular Lat and Long to "map" the air currents. I intend to coordinate with the FAA and the local airport tower to share the data and provide a current map of winds and altitudes for the balloonists that launch from the airport here. The craft will have a "chaf" tail underneath it for the tower's radar to see and track, cut to 1/4 wavelength of their near space signal.

I never doubted your responsibility.

Oh, sure, especially not with those teeth.

Carbon fiber mounting of the accelerometer might be a viable solution.

I got clever and made mounts from cut-down ear-plugs (memory foam), and hot glue. Very nice! Works like a charm.

OK. That's certainly a creative choice of dampening material to use.

The foam is designed to dampen 95db or so of vibration (sound). Seemed to me to be a good thing to try. Cheap too! And widely available. The stuff "flows" slowly finding a new "norm" for the given application of force. It is like a good set of shocks because it is slow to compress, but it is equally slow to de-compress. It slows every bump down nicely.

You came to the right place.

CR4 has an abundance of jerks.

They literally post here many times each day.

Simply begin by reading the posts from Anonymous Posters and analyzing them.

If more data is needed, some of the members here will provide more specific information.

Hilarious, and 'not-wrong,' but also not relavent to the discussion thread.

This is a case where I wish we had two voting axes, "I like this/I don't like this" and "Good Answer/Off Topic." I *LOVE* this response, but it *DOES* distract from the problem at hand, rather than advance it.

At the risk of being labelled one:

Jerk is the third derivitive of position with respect to time.

Yank is Jerk x mass

Jounce is the fourth derivitive of position with respect to time or the rate of change of Jerk. (NASA actually specified maximum Jounce for the Hubble Space Telescope)

https://en.wikipedia.org/wiki/Jounce

After you posted that a Yank is a Massive Jerk I didn't know whether to be offended or to ask if you have been talking to my wife.

That would depend on who you really are! Posting anonym does not make it easy to speak to your wife, would you not thing? . . .

I note, yet again, a score of 5 off-topic, a score which is by far the most common, apart from the odd 1-2. Is there a Gang of Five to be wary of?

If you 'self-mark' as Off Topic, your vote counts for 5.

And, if the mods mark it as OT it counts as 5, too.

There is no "Gang of 5."

When moderator Merph was around, he once gave 10,000 OT's to somebody--Doorman, iirc.

Dang, now THAT'S showing someone the door, throwing them through it, THEN opening the door after they've left.

I can't even think of what he had to to to get smacked that hard, then again, most of what I *CAN* think of is weak puns and jokes so old that after God said 'Let There Be Light,' he saw the list and said, "Dude, The Universe Has Only Been Around For Seven Seconds, And These Jokes Were Old Last Year."⁽¹⁾

Notes

1. Yeah, when I'm doing 'God speak,' I have to capitalize every word, it's just how loud and booming the Voice seems to be. It could have been worse, I could have been using BRIAN BLESSED'S⁽²⁾ voice for God.
2. All caps, Bold, and (if the forum allows) one and a half to two times the size of the normal font. BRIAN BLESSED is, after all, the 'greatest actor in England, measured by volume.'
   

Great, now I don't know if I got that GA vote for the door joke, the 'my jokes are so old' joke, or for the BRIAN BLESSED shout-out.

He pointed those OTs out with pride, I might add.

Thats what happens if you rate yourself off topic...

When I need to analyze a jerk I typically just look in a mirror and say 'It's okay. Nature made you this way for a reason.' then go online and smile all day long knowing I am just being who I was created to be!

Someone seems to be in their happy place.

When I need to analyze a jerk, I read a post from an AP.

LOVE IT!!