Dear Jason, Now all clear to me, thanks!
Peter Am Do., 3. Feb. 2022 um 10:39 Uhr schrieb Jason Moore <moorepa...@gmail.com >: > Peter, > > Yes, the velocity constraints work the same way. There are reaction forces > that constrain the velocities. > > Jason > moorepants.info > +01 530-601-9791 > > > On Thu, Feb 3, 2022 at 10:37 AM Peter Stahlecker < > peter.stahlec...@gmail.com> wrote: > >> Dear Jason, >> >> Thanks! >> If I understood correctly, if I use velocity constraints, I do not use >> the minimal number of generalized coordinates, hence these reaction forces >> and 'virtual' speeds appear in my force term of the equations of motion. As >> they are normal to the motion of the particle(s), I simply set them to zero >> in the force term. >> >> Peter >> >> moore...@gmail.com schrieb am Donnerstag, 3. Februar 2022 um 10:20:46 >> UTC+1: >> >>> Peter, >>> >>> If you have a particle that is forced to move along a path (typically be >>> a configuration constraint), then there exists reaction forces normal to >>> the path that keep it on the path. These forces are not present in the >>> equations of motion when they are formed with minimal coordinates. But you >>> can expose the forces by introducing fictitious (auxiliary) generalized >>> speeds normal to the path and a variable for the forces. This will result >>> in the minimal equations of motion and some algebraic equations for the >>> forces. All of these equations will have the aux speeds, which then must be >>> set to zero because they are fictitious. This should then leave you with >>> the equations of motion plus some equations that can be solved for the >>> forces. >>> >>> Jason >>> moorepants.info >>> +01 530-601-9791 <(530)%20601-9791> >>> >>> >>> On Thu, Feb 3, 2022 at 10:03 AM Peter Stahlecker <peter.st...@gmail.com> >>> wrote: >>> >>>> Thanks! Would I also set the 'reaction forces' appearing in the force >>>> term equal to zero? >>>> As per my understanding of mechanics, they also should have no >>>> influence on the equations of motion (?) >>>> >>>> moore...@gmail.com schrieb am Donnerstag, 3. Februar 2022 um 09:59:53 >>>> UTC+1: >>>> >>>>> The virtual speeds will appear in the force equations, but you then >>>>> just set them to zero because they are fictitious. You force equation >>>>> should then be correct. >>>>> >>>>> Jason >>>>> moorepants.info >>>>> +01 530-601-9791 <(530)%20601-9791> >>>>> >>>>> >>>>> On Thu, Feb 3, 2022 at 9:58 AM Peter Stahlecker <peter.st...@gmail.com> >>>>> wrote: >>>>> >>>>>> When I use a velocity constraint to force a particle not to move in a >>>>>> certain direction, there must be a 'reaction force' on the particle. >>>>>> I use KM.auxiliary_eqs to find reaction forces, which works very well >>>>>> in general! >>>>>> >>>>>> However, if I try to find the reaction force due to a velocity >>>>>> constraint, it does no seem to work: >>>>>> The force term of the equations of motion contains the 'virtual >>>>>> speed', its time derivative and the reaction force. >>>>>> >>>>>> Am I doing something wrong, or do velocity_constraints and >>>>>> KM.auxiliary_eqs just not work together? >>>>>> I attach some code, showing my problem. >>>>>> >>>>>> *Any help is greatly appreciated!* >>>>>> >>>>>> -- >>>>>> You received this message because you are subscribed to the Google >>>>>> Groups "sympy" group. >>>>>> To unsubscribe from this group and stop receiving emails from it, >>>>>> send an email to sympy+un...@googlegroups.com. >>>>>> To view this discussion on the web visit >>>>>> https://groups.google.com/d/msgid/sympy/e8091bb4-9730-4dc2-8e31-59662ef09e56n%40googlegroups.com >>>>>> <https://groups.google.com/d/msgid/sympy/e8091bb4-9730-4dc2-8e31-59662ef09e56n%40googlegroups.com?utm_medium=email&utm_source=footer> >>>>>> . >>>>>> >>>>> -- >>>> You received this message because you are subscribed to the Google >>>> Groups "sympy" group. >>>> To unsubscribe from this group and stop receiving emails from it, send >>>> an email to sympy+un...@googlegroups.com. >>>> >>> To view this discussion on the web visit >>>> https://groups.google.com/d/msgid/sympy/5b2301f3-8dc7-4e69-9a52-31f5d235daban%40googlegroups.com >>>> <https://groups.google.com/d/msgid/sympy/5b2301f3-8dc7-4e69-9a52-31f5d235daban%40googlegroups.com?utm_medium=email&utm_source=footer> >>>> . >>>> >>> -- >> You received this message because you are subscribed to the Google Groups >> "sympy" group. >> To unsubscribe from this group and stop receiving emails from it, send an >> email to sympy+unsubscr...@googlegroups.com. >> To view this discussion on the web visit >> https://groups.google.com/d/msgid/sympy/aa252785-8644-40a6-afe9-c7a817388500n%40googlegroups.com >> <https://groups.google.com/d/msgid/sympy/aa252785-8644-40a6-afe9-c7a817388500n%40googlegroups.com?utm_medium=email&utm_source=footer> >> . >> > -- > You received this message because you are subscribed to the Google Groups > "sympy" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to sympy+unsubscr...@googlegroups.com. > To view this discussion on the web visit > https://groups.google.com/d/msgid/sympy/CAP7f1AiNUGcpQx-8X4xoZp0ezT7%2Bgm_q8ZZpKmTwTGYix9qiGA%40mail.gmail.com > <https://groups.google.com/d/msgid/sympy/CAP7f1AiNUGcpQx-8X4xoZp0ezT7%2Bgm_q8ZZpKmTwTGYix9qiGA%40mail.gmail.com?utm_medium=email&utm_source=footer> > . > -- You received this message because you are subscribed to the Google Groups "sympy" group. 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