Nuno, You can only select one set of independent generalized coordinates for things to work out. You seem to be setting two sets, both the cartesian and the angular coordinates. You may need to refer to a dynamics text to see how to go about selecting generalized coordinates.
Jason moorepants.info +01 530-601-9791 On Thu, Aug 11, 2016 at 4:30 AM, Nuno <nmi...@gmail.com> wrote: > Right now I'm trying to get the equations of motion of a 3D pendulum > system (spherical pendulum) and I want to describe the system using the > (x,y,z) coordinates of the mass as well as its attitude (phi, theta, psi), > > > > <https://lh3.googleusercontent.com/-1z2YB-NMqyI/V6xeoxDJD8I/AAAAAAAAAOg/mXiuBW11_ZEjKZWSnK56ILAP1XzrXzB1wCLcB/s1600/simple_diag.png> > > > In the jupyter notebook (https://nbviewer.jupyter.org/ > github/ndevelop/sympy_3D_pendulum/blob/master/3D%20pendulum.ipynb) I have > added 3 reference frames (Inertial, one for the anchor point and other to > the mass). > > The anchor frame is not really necessary since its the same as the > inertial frame for this problem, however futher down the line I want to > test the system with a mobile anchor point (imagine it as a balloon with a > lift force applied in the anchor center of mass). > > > The mass frame is centered on the "Mass" center of mass (this nomenclature > is not the best) and it's orientation in relation to the inertial frame is > composed by 3 euler angles. > > > Now the twist in the problem is that the mass is "actuated". Besides the > gravity force acting on its center of mass (along the inertial frame > z-axis), there is also a force F applied on the positive direction of > x-axis of the mass reference frame and a torque T about the z-axis of the > mass reference frame. > > > Furthermore, I want to "model" the cable connecting the mass to the anchor > point, by using a distance constraint: (r_anchor - r_mass) - cable_length > = 0 > > > The goal is to obtain the equations of motion for this system. > > I have set everything as described in this jupyter notebook > <https://nbviewer.jupyter.org/github/ndevelop/sympy_3D_pendulum/blob/master/3D%20pendulum.ipynb>, > however I'm not sure if the way I'm doing things is correct, since the > resulting equations of motion seem to be really large for such a simple > problem. Then again, I'm not experienced with this kind of problems. > > > Thanks in advance for all the help, > > Nuno > > > > > > -- > 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 post to this group, send email to sympy@googlegroups.com. > Visit this group at https://groups.google.com/group/sympy. > To view this discussion on the web visit https://groups.google.com/d/ > msgid/sympy/41580794-f61d-4106-9425-d2552d71424a%40googlegroups.com > <https://groups.google.com/d/msgid/sympy/41580794-f61d-4106-9425-d2552d71424a%40googlegroups.com?utm_medium=email&utm_source=footer> > . > > For more options, visit https://groups.google.com/d/optout. > -- 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 post to this group, send email to sympy@googlegroups.com. Visit this group at https://groups.google.com/group/sympy. To view this discussion on the web visit https://groups.google.com/d/msgid/sympy/CAP7f1Ag8qXp5Z16nkh68MzeTFdEZVB9R7A9pX5d1LE8y%2BwBnwA%40mail.gmail.com. For more options, visit https://groups.google.com/d/optout.
