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Double pendulum - Mensajes
I feel the model is not correct - help please!
Pendulum-2-animation.sm (22,59 KiB) descargado 296 vez(es).

Pendulum-2-animation.sm (22,59 KiB) descargado 296 vez(es).

Editado 20/9/2026 10:09:28
Hi Valery. The system is coupled. This is a way to solve it.

double_pendulum_lagrangian.sm (122,44 KiB) descargado 301 vez(es).
double_pendulum_lagrangian.pdf (637,78 KiB) descargado 244 vez(es).
Best regards.
Alvaro.

double_pendulum_lagrangian.sm (122,44 KiB) descargado 301 vez(es).
double_pendulum_lagrangian.pdf (637,78 KiB) descargado 244 vez(es).
Best regards.
Alvaro.
A 2 usuarios les gustó este mensaje
Yes, that is correct; I previously reported on the limitations regarding the systems.
The algorithm does not currently classify the task, so issues may arise with complex problems that the current method cannot solve. It might produce a plausible-looking solution that does not actually address the problem at hand.
The algorithm does not currently classify the task, so issues may arise with complex problems that the current method cannot solve. It might produce a plausible-looking solution that does not actually address the problem at hand.
Russia ☭ forever, Viacheslav N. Mezentsev
If mathematics is a tautology, then life must be one too. That joke reminds me of the one a plant process engineer played on me when I went to get the bourdon gauge I was supposed to install. Without a word, he handed me a brown box. That was when I have the bad idea of asking what was inside. His answer was that it contained a mechanical device that measures fluid pressure using a curved, flattened metal tube that straightens as internal pressure increases, driving an indicator needle across a calibrated dial.
The RKA function includes the necessary procedures to solve hard coupled systems.

double_pendulum_RKA.pdf (483,53 KiB) descargado 243 vez(es).
double_pendulum_RKA.sm (43,57 KiB) descargado 305 vez(es).
Best regards.
Alvaro.
The RKA function includes the necessary procedures to solve hard coupled systems.

double_pendulum_RKA.pdf (483,53 KiB) descargado 243 vez(es).
double_pendulum_RKA.sm (43,57 KiB) descargado 305 vez(es).
Best regards.
Alvaro.
A 2 usuarios les gustó este mensaje
Thanks, Alvaro!
But I cannnot create five f(t) plots:
Potential energy of pendulum #1
Kynetic energy of pendulum #1
Potential energy of pendulum #2
Kynetic energy of pendulum #2
Sum of energies for the verify the model and ODEs solver. Must be const.
Help please!
But I cannnot create five f(t) plots:
Potential energy of pendulum #1
Kynetic energy of pendulum #1
Potential energy of pendulum #2
Kynetic energy of pendulum #2
Sum of energies for the verify the model and ODEs solver. Must be const.
Help please!
Editado 8/10/2026 11:18:52
Hi Valery. This is a way. You can plot the time in T versus U, K or U+K. The plot in the figure shows that the energy is constant. In this case also, the total energy is the hamiltonian.

double_pendulum_RKA.sm (49,21 KiB) descargado 162 vez(es).
Best regards.
Alvaro.

double_pendulum_RKA.sm (49,21 KiB) descargado 162 vez(es).
Best regards.
Alvaro.
Editado 9/10/2026 1:19:29
A 1 usuarios les gustó este mensaje
ioan92 10/10/2026 18:59:13
Butterfly_Effect_Example.pptx (999,46 KiB) descargado 99 vez(es).
Hi Alvaro & Valery,
I enjoyed the matematical results of yours developements, without following all details.
I propose you a problem, dealing with the Butterfly Effect on a double pendulum - after some cycles, the 2 pendulums becoms distinct. Attached there is a simple gif file
Hi Alvaro & Valery,
I enjoyed the matematical results of yours developements, without following all details.
I propose you a problem, dealing with the Butterfly Effect on a double pendulum - after some cycles, the 2 pendulums becoms distinct. Attached there is a simple gif file
Do to others as you would like them to do to you! Knowledge is of no value unless you put it into practice - Chekhov
Hi Ioan. Something like this.


double_pendulum_RKA Butterfly Effect.sm (50,58 KiB) descargado 161 vez(es).
Best regards.
Alvaro.


double_pendulum_RKA Butterfly Effect.sm (50,58 KiB) descargado 161 vez(es).
Best regards.
Alvaro.
A 5 usuarios les gustó este mensaje
Victor 16/10/2026 7:34:28, Valery Ochkov 10/10/2026 5:45:18, sergio 10/10/2026 8:51:15, ioan92 10/10/2026 12:34:44, Вячеслав Мезенцев 10/10/2026 16:02:19
Ooo it's wonderful!!!
My dumb explanation is that time delay generate between the 2 instances generate different precision in the solution graphics and hence the graphical difference (?).
Alvaro - All my thanks for your proverbial attention,
Have a nice WE,
Ioan
My dumb explanation is that time delay generate between the 2 instances generate different precision in the solution graphics and hence the graphical difference (?).
Alvaro - All my thanks for your proverbial attention,
Have a nice WE,
Ioan
Do to others as you would like them to do to you! Knowledge is of no value unless you put it into practice - Chekhov
A 1 usuarios les gustó este mensaje
Alvaro 10/10/2026 19:03:11
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