Jason, thanks again for answering and excuse me for any dumb questions. When you are saying that I can't use the position (x,y,z) and euler angles (roll, pitch, yaw) as my generalized coordinates, is that something specific to the Kane's Method? I ask this since that's the first time I hear about that and for example, when one wants to model a rigid body in space (both its position and orientation) those are the generalized coordinates used (Think for example of a quadcopter model).
Thanks, Nuno segunda-feira, 15 de Agosto de 2016 às 19:13:25 UTC+1, Jason Moore escreveu: > > 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 <javascript:>> > 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+un...@googlegroups.com <javascript:>. >> To post to this group, send email to sy...@googlegroups.com <javascript:> >> . >> 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/4d22f6ec-f826-4a45-98ac-14152edaeac5%40googlegroups.com. For more options, visit https://groups.google.com/d/optout.
