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.
