Re: [sympy] Re: 3D pendulum and equations of motion of multi-body systems (KanesMethod)

2016-08-18 Thread Jason Moore
No this is not specific to Kane's method. You, as the modeler, get to choose whatever coordinates you want to describe a system including redundant coordinates. But for efficiency and simplicity's sake you are better off choosing a unique set of minimal coordinates, i.e. generalized coordinates. Yo

Re: [sympy] Re: 3D pendulum and equations of motion of multi-body systems (KanesMethod)

2016-08-18 Thread James Milam
To kind of expand on what Jason's saying a 3D pendulum can be completely defined using just (x, y, z) and you can deduce the angles from these coordinates. In your case the pendulum only has two degrees of freedom (x and y for instance and z be calculated because the pendulum has a fixed length

Re: [sympy] Re: 3D pendulum and equations of motion of multi-body systems (KanesMethod)

2016-08-18 Thread Nuno
Thanks for the input! I probably wasn't able to explain it properly, but in this pendulum system the mass is actuated. Think of it as a differential drive robot with fans instead of wheels (instead of the mass). The force acting on the x-axis of the mass frame and the torque about the z-axis of

Re: [sympy] Re: 3D pendulum and equations of motion of multi-body systems (KanesMethod)

2016-08-18 Thread Jason Moore
The system that you drew only has two degrees of freedom regardless of what forces you apply to the system. It also isn't clear as to whether you consider the mass a particle or a rigid body. The problem is very different depending on that. If you want a conical pendulum that has forces applied to

[sympy] Nested piecewise functions

2016-08-18 Thread Vincent Noel
Hi, I'm trying to represent a weird case using piecewise functions : z = sympy.Piecewise((True, x>0), (False, True)) A piecewise function returning a boolean value... so far so good. The problems comes when I want to use that as a condition inside another Piecewise : z2 = sympy.Piecewise((1,

[sympy] Galois Fields

2016-08-18 Thread clemens novak
Hello, I try to perform calculations in GF(2^3); e.g. calculate (x^2+x)(x+1) = x^3 + 2x^2 + x = x^3 + x as polynomial coefficients are modulo-2. Using the irreducible polynomial x^3 + x + 1 I arrive at (x^2+x)(x+1) = 1. I try to do the same in sympy import sympy as sym import sympy.polys as p

Re: [sympy] Nested piecewise functions

2016-08-18 Thread Aaron Meurer
I would use ITE for this case. It's the boolean version of Piecewise. Aaron Meurer On Thu, Aug 18, 2016 at 9:51 AM, Vincent Noel wrote: > Hi, > > I'm trying to represent a weird case using piecewise functions : > > z = sympy.Piecewise((True, x>0), (False, True)) > > A piecewise function returnin

Re: [sympy] Nested piecewise functions

2016-08-18 Thread Aaron Meurer
Of course, for Piecewise((True, x>0), (False, True)), you could just replace it with x > 0. It seems ITE doesn't do this automatically but it does if you call to_nnf() on it. In [12]: ITE(x > 0, True, False).to_nnf() Out[12]: x > 0 Aaron Meurer On Thu, Aug 18, 2016 at 4:09 PM, Aaron Meurer wrot

[sympy] Re: Galois Fields

2016-08-18 Thread Kalevi Suominen
On Thursday, August 18, 2016 at 9:30:23 PM UTC+3, clemens novak wrote: > > Hello, > > I try to perform calculations in GF(2^3); e.g. calculate (x^2+x)(x+1) = > x^3 + 2x^2 + x = x^3 + x as polynomial coefficients are modulo-2. Using the > irreducible polynomial x^3 + x + 1 I arrive at (x^2+x)(x+