Peter,
If orient_body_fixed produces longer equations of motion than chaining
orient_axis (or the older orient() and orientnew()), then we should figure
out what the problem is with orient_body_fixed. orient_body_fixed should
produce shorter equations of motion because the angular velocities are
supposed to be in the simplest form.
Jason
moorepants.info
+01 530-601-9791
On Mon, Feb 14, 2022 at 6:41 PM Peter Stahlecker <peter.stahlec...@gmail.com>
wrote:
> Dear Jason,
>
> As to the speed of the new terms, I simply tried it, using the equations
> of motion of a one body pendulum.
> There is no difference to the older terms:
>
> with the *body* version the the rhs has 863, 824 operations.
> with the axis version, 2 intermediate frames, the rhs has 43,722
> operations.
>
> The operations count was *exactly* the same with older and newer terms.
>
> Take care, Peter
>
> On Mon 14. Feb 2022 at 18:04 Peter Stahlecker <peter.stahlec...@gmail.com>
> wrote:
>
>> Dear Jason,
>>
>> Just read you latest addition about vectors and reference frames.
>> Small question:
>> In order to rotate a frame relative to another one, you use these terms
>> *A.orient_axis(N, ..)*
>> *A.orient_body_fixed(N, …)*
>>
>> I assume, these are the new versions for
>> A.orientnew(N, ‚Axis‘, …)
>> A.orientnew(N, ‚Body, …)
>>
>> You might recall, that I ‚empirically‘ found that the *Body* version
>> created much larger equations of motion compared to using ‚intermediate ‚
>> *Axis*‘ versions.
>>
>> Is it better to use *orient_body_fixed,* to avoid this issue of larger
>> equations of motion?
>>
>> Thanks & take care!
>> Peter
>>
>>
>>
>> On Sun 6. Feb 2022 at 08:19 Peter Stahlecker <peter.stahlec...@gmail.com>
>> wrote:
>>
>>> Dear Jason,
>>>
>>> Thanks a lot for your explanation! Clear!
>>> I checked on metaclasses, but I must admit I mostly understood, that a
>>> simple user like me should not mess with them! :-))
>>>
>>> Peter
>>>
>>> On Sun 6. Feb 2022 at 07:49 Jason Moore <moorepa...@gmail.com> wrote:
>>>
>>>> Peter,
>>>>
>>>> All `dynamicsymbols` is, is:
>>>>
>>>> f = Function('f')
>>>> t = symbols('t')
>>>> f_of_t = f(t)
>>>>
>>>> The last line `f(t)` is generating a new class of type f, instead of
>>>> using a predefined class (look up metaclasses). So the user, typically not
>>>> aware of this element in Python, is confused about what they are working
>>>> with in the last line. It is just the way SymPy Function works. There are
>>>> open issues about trying to change it to something more sensible for the
>>>> user to understand.
>>>>
>>>> Jason
>>>> moorepants.info
>>>> +01 530-601-9791
>>>>
>>>>
>>>> On Sun, Feb 6, 2022 at 7:39 AM Peter Stahlecker <
>>>> peter.stahlec...@gmail.com> wrote:
>>>>
>>>>> My question is more for my ‚general education‘ in sympy.
>>>>>
>>>>> I write this little program
>>>>>
>>>>> *from sympy.physics.mechanics import **
>>>>> *import sympy as sm*
>>>>> *a = dynamicsymbols(‚a‘)*
>>>>> *b = sm.symbols(‚b‘)*
>>>>>
>>>>> *print(‚type of a:‘, type(a))*
>>>>> *print(‚type of b:‘, type(b))*
>>>>>
>>>>> I get this result:
>>>>>
>>>>> *type of a: a*
>>>>> *type of b: class sympy.core.symbols.Symbols*
>>>>>
>>>>> Is seems that *a* does not have a type. How can that be? I thought in
>>>>> python ‚everything‘ has a type.
>>>>>
>>>>> Thanks!
>>>>> Any explanation is highly appreciated!
>>>>>
>>>>>
>>>>>
>>>>>
>>>>> --
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>>>>> <https://groups.google.com/d/msgid/sympy/5db2836e-44a8-428f-8b82-c56b2b2b5b20n%40googlegroups.com?utm_medium=email&utm_source=footer>
>>>>> .
>>>>>
>>>> --
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>>>> <https://groups.google.com/d/msgid/sympy/CAP7f1Ajkjs%3DNhJOhrFXmEpLJ6nv0TM9FgHXg%3DS1kSCF-6Cw5zw%40mail.gmail.com?utm_medium=email&utm_source=footer>
>>>> .
>>>>
>>> --
>>> Best regards,
>>>
>>> Peter Stahlecker
>>>
>> --
>> Best regards,
>>
>> Peter Stahlecker
>>
> --
> Best regards,
>
> Peter Stahlecker
>
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