Dale Peterson

Animation of the motion of the bicycle

By luke, on June 6th, 2010

New VPS

By luke, on June 6th, 2010

My VPS host just upgraded their servers to Ubuntu 10.04, so I just spent today saving all my old stuff, wiping my VPS, and reinstalling everything. I was using nginx as my webserver previously, but now I’m using lighttpd, and it was pretty easy to setup. I’m still ironing out the bugs, but I . . . → Read More: New VPS

New rolling torus code

By luke, on October 15th, 2009

I changed the code to the rolling torus example pretty significantly. Little fixes in how the arrows representing the body fixed unit vectors are now fixed. Additionally, I added some code that calculates the kinetic, potential and total energy of the system, and plots it. The scipy solver seems to do a pretty good . . . → Read More: New rolling torus code

Gyrostat

By luke, on October 9th, 2009

I just added an example of use for the derivation of the equations of a gyrostat using PyDy. It is located in the examples/gyrostat/ subdirectory.

In case you aren’t familiar, here is the definition of a gyrostat:

A gyrostat is a mechanical system which is comprised of more than one body and yet has . . . → Read More: Gyrostat

New examples of use with PyDy

By luke, on August 23rd, 2009

In the last several days I’ve made a lot of updates to tools for using PyDy and have come very close to settling on the way that PyDy is used to derive the equations of motion. I have added and updated several examples, including the double pendulum and a rigid body with two reaction . . . → Read More: New examples of use with PyDy

Developments in PyDy

By luke, on August 12th, 2009

I haven’t blogged in about two weeks, and there has been a lot of progress in PyDy. For starters, PyDy now ‘automatically’ derives the equations of motion for a rolling disc and a rigid body in space. I haven’t blogged in about two weeks, and there has been a lot of progress in PyDy. . . . → Read More: Developments in PyDy

Recursive methods for computing equations of motion

By luke, on July 28th, 2009

In the last week, I added methods to the NewtonianReferenceFrame class of PyDy which start at the top of the reference frame tree and the point tree and do several things. The first method, recursive_subs(expr), is designed to take kinematic differential equations (which arise through a combination of linear nonholonomic constraints and/or holonomic constriants, . . . → Read More: Recursive methods for computing equations of motion

New trig functions

By luke, on July 20th, 2009

Last week I spent most of my time writing and testing new trigonometric functions for Sympy. Sympy already had sin, cos, tan, cot, asin, acos, atan, acot, but did not have sec, csc, asec, or acsc. So I added those four new functions and am in the process of writing very extensive tests for . . . → Read More: New trig functions

GSoC developments

By luke, on July 13th, 2009

In the last week, I finalized the locate method for the point class, as well as the .rel() and .vel() methods. Just as relative angular velocity between adjacent ReferenceFrame instances is stored, so is the relative position and relative velocity of points. By doing it in this fashion, the partial velocities can be formed . . . → Read More: GSoC developments

Point class and doctest

By luke, on July 6th, 2009

When I implemented the ReferenceFrame class with Ondrej, things were fairly straightfoward because the angular velocities of frames are 1) always described relative to another frame, and 2) because they add up in according to the angular velocity addition theorem. Points, on the other hand have proven a bit more complex to implement. When . . . → Read More: Point class and doctest