On Circuit Theory
Probably posted before, but didn't bother to check.
Apologies to alluded, only out of literary necessity.
A group of Polish nationals charter a flight to Tenerife for vacation. On landing approach, a member sitting by the window on the right row, spots a beautiful 3 masted ship leaving harbour and hails:
- Hey, come over, see that ship !!
Mates crowd to the windows, the airplane rolls over to the right and crashes.
Moral: Don't let poles sit in the right of the plane.
Rodolfo
Probably posted before, but didn't bother to check.
Apologies to alluded, only out of literary necessity.
A group of Polish nationals charter a flight to Tenerife for vacation. On landing approach, a member sitting by the window on the right row, spots a beautiful 3 masted ship leaving harbour and hails:
- Hey, come over, see that ship !!
Mates crowd to the windows, the airplane rolls over to the right and crashes.
Moral: Don't let poles sit in the right of the plane.
Rodolfo
Wyloch said:
It's based on linear control systems, and it's REALLY funny! (poles of the transfer function in the right half of the plane means the system is unstable)
Stability and poles
I have discovered - empirically - that a single pole at the origin can cause instability. As a non-audio DIY project I recently made a round dining table, 1200mm diameter from 30mm thick maple. Indeed I sold my perfectly good 4-legged oak dining room table to accomodate this project.
I mounted my table atop a commercial 'mushroom' type base of unfortunately feeble character which supports the table by means of a kind of cruciform affair at the end of a 50mm stainless steel pole. At the Origin in my 'table space', so to speak. Now everytime we have a 'purturbation' in table space, like someone shaking the salt cellar, or Sixpence the cat jumping up on the table, the entire table and base oscillates at about 0.75Hz with peak-peak amplitude of about 30mm. The disasterous results of this are usually sufficient to remove the cause of the purturbation, but it happens time after time.
So even a single pole at the origin can cause oscillation if the pole is feeble enough. . .
John
I have discovered - empirically - that a single pole at the origin can cause instability. As a non-audio DIY project I recently made a round dining table, 1200mm diameter from 30mm thick maple. Indeed I sold my perfectly good 4-legged oak dining room table to accomodate this project.
I mounted my table atop a commercial 'mushroom' type base of unfortunately feeble character which supports the table by means of a kind of cruciform affair at the end of a 50mm stainless steel pole. At the Origin in my 'table space', so to speak. Now everytime we have a 'purturbation' in table space, like someone shaking the salt cellar, or Sixpence the cat jumping up on the table, the entire table and base oscillates at about 0.75Hz with peak-peak amplitude of about 30mm. The disasterous results of this are usually sufficient to remove the cause of the purturbation, but it happens time after time.
So even a single pole at the origin can cause oscillation if the pole is feeble enough. . .
John
By using a single pole you did actually implement two poles (i.e. a conjugate pair) ! 😎
It does not often happen that one gets twice as much as one actually paid for ! 😀
Regards
Charles
It does not often happen that one gets twice as much as one actually paid for ! 😀
Regards
Charles
Re: Stability and poles
Actually, I guess I recall a paper by a japanese research team published some years back on the subject.
They devised a clever variation of the "pole shadowing" technique, whereby a large umbrella was rigidly tied to the table at its center, while a set of tree heavy duty blowers spaced 120 deg. around and canted upward exerted a stabilizing force.
Reportedly, though the instability was not erradicated completely, it helped damp it considerably.
Rodolfo
John Hope said:
Actually, I guess I recall a paper by a japanese research team published some years back on the subject.
They devised a clever variation of the "pole shadowing" technique, whereby a large umbrella was rigidly tied to the table at its center, while a set of tree heavy duty blowers spaced 120 deg. around and canted upward exerted a stabilizing force.
Reportedly, though the instability was not erradicated completely, it helped damp it considerably.
Rodolfo
My Table Pole
My good fellows
I plan very soon to replace my single pole (or complex conj 0 +/-j0 polepair as suggested by Charles) with a barrel-like structure about 500mm diameter.
I tried to analyse this by reasoning that although the barrrel is continuous, one could model it as the limiting case of a very large number of poles all located on a circle. A 'Distributed Pole', in fact. But this soon became 'mathematically intractable' as the academics say when they get bogged down in maths.
So I adopted an alternative approach by considering my table as a discrete entity, which to be sure it is. This means I can analyse it in the z-plane. Since my barrel is less than 1 metre diameter, the Distributed Pole is in effect, within the Unit Circle on the z-plane and my table will be unconditionally stable.
Just to be sure, I'll fill the barrel with some sand. . .
JFH
My good fellows
I plan very soon to replace my single pole (or complex conj 0 +/-j0 polepair as suggested by Charles) with a barrel-like structure about 500mm diameter.
I tried to analyse this by reasoning that although the barrrel is continuous, one could model it as the limiting case of a very large number of poles all located on a circle. A 'Distributed Pole', in fact. But this soon became 'mathematically intractable' as the academics say when they get bogged down in maths.
So I adopted an alternative approach by considering my table as a discrete entity, which to be sure it is. This means I can analyse it in the z-plane. Since my barrel is less than 1 metre diameter, the Distributed Pole is in effect, within the Unit Circle on the z-plane and my table will be unconditionally stable.
Just to be sure, I'll fill the barrel with some sand. . .
JFH
Isn't the phrase "mathematically intractable" reserved for balancing a checkbook??
And I always thought "z plane, z plane" was an announcement of arrival used to inform za bozz of ze arrival of ze passengers to za island..?
Cheers, John
And I always thought "z plane, z plane" was an announcement of arrival used to inform za bozz of ze arrival of ze passengers to za island..?
Cheers, John
then I am a real engineering geek - 3 times the first try, scored 18000 points and lost count the second. 
Want Jokes!!!
Everyone:
Too long has elapsed without jokes on this thread. The thread then filters down the list and people forget about it.
So come on - let's brighten up our Monday!
Regards
John
Everyone:
Too long has elapsed without jokes on this thread. The thread then filters down the list and people forget about it.
So come on - let's brighten up our Monday!
Regards
John
Re: Want Jokes!!!
Well, I dunno. I get all the humor I can take reading the regular threads...😀
Jan Didden
John Hope said:
Well, I dunno. I get all the humor I can take reading the regular threads...😀
Jan Didden
Re: Reading the regular threads
Yeah, yeah, I got also tears in my eyes, but not from laughing...........
😱
janneman said:
Yeah, yeah, I got also tears in my eyes, but not from laughing...........
😱
- Status
- Not open for further replies.