lvODE 0.1 LV2009, 8.2

Author: Wojciech Golebiowski (vugie), w_golebiowski at tlen dot pl

Name: lvODE

Type: Library

LabVIEW Version: 2009

Description

lvODE is a set wrappers, an interface to ODE (Open Dynamics Engine) library written in C and used to simulate dynamics of rigid body systems, including interactivity and in real time. In the present state lvODE allows you to use almost the full functionality of ODE in the LabVIEW environment using object-oriented programming (LVOOP). Such simulations may be used, among others, for programming the control systems of robots and manipulators (as well as in the control systems themselves, i.e. for trajectory planning), for development and testing of artificial intelligence systems, for modeling of complex mechanisms and other physical systems, etc.

lvODE is not a strict set of ODE wrappers. Although it uses the same concepts, the same terminology and most of the ODE functions are reflected, many of them have been grouped, data structures have been simplified, all in a user-friendly manner and taking into account specifics of LabVIEW environment. There are also few features not present in the original library which greatly facilitate programming – i.e. Object Manager. Further extensions (i.e. 3D Picture Control integration) are planned.

Short preview movie:

Briefly about the ODE

ODE is a free and widely-known library designed to simulate systems of rigid bodies. The programmer defines the layout of bodies, their physical parameters and types of connections between them, the role of the library is to calculate the forces acting in the system and to determine position and velocity of all bodies in the next time step, while satisfying all defined relationships. Programmer is able to interfere in simulation in full range while it goes on. It allows for the accurate analysis of its results (access to all the physical parameters) as well as programming any degree of interactivity. ODE is designed specifically to perform real time simulations – it uses a first order integrator (the procedure to solve a system of differential equations), which is a compromise between speed and accuracy. Results generated are not as accurate as they would be using higher-order integrators, but it is stable, fast and flexible.

The basic features of ODE include:

• Rigid body with arbitrary mass distribution
• Types of kinematic pairs (joints, constraints): ball, slider, hinge, suspension, universal (Cardan), linear and rotary actuators, contact, and combinations that are already listed
• Types of geometry used for collision detection: sphere, cube, cylinder, capsule, plane, ray, any shape in the form of triangle mesh, convex, heightfield
• Three types of spaces for fast collision finding
• Equations of motion derived using Lagrange multipliers
• Choice of integration method: the "full" method – slower, but more accurate, and quick iterative method
• An advanced model of contact and friction

Installation
The contents of the archive folder ("lvODE") should be extracted to directory \user.lib. After restarting LabVIEW the sub-palette "lvODE" appears in the User Libraries section, where all the necessary functions may be found.
Or use the VIPM package.
Documentation
The documentation is located in the subdirectory 'doc' and it consists of the following files:

• ODE Manual.pdf - The original guide to the ODE. At least brief knowledge of it is necessary to understand the main concepts and mechanisms of library. Due to the use of the same terminology, it can also be a sufficient source to use the lvODE. The main difference from the original is the simplified naming convention.
• lvODE Class Hierarchy.pdf - graphical representation of a lvODE class hierarchy of classes library - not necessary to start programming, but it may help to understand certain concepts.
• lvODE Function Reference.pdf - a list of all public lvODE functions with descriptions and organized by class. Descriptions of the functions derive much of the original ODE manual, however, cover all the differences of the conventions and LabVIEW specifics. This document is definitely to be polished (better grouping, more detailed descriptions of each section, etc.)
• Files *. png - map of all pallets

An integral part of the documentation are also descriptions in of context help for each VI. In large part they fit the descriptions in the file "lvODE Function Reference". Private functions are documented as well.

Examples

Example applications are located in "examples" subdirectory. There are few examples with varying degree of complexity, and with comprehensive comments in the code. These examples, supported by context help and (in difficult cases), reading a few chapters of the original manual should be sufficient to start programming in lvODE.

Comments

lvODE is not a finished project. Once the ODE itself is still being developed, second, not whole its functionality is currently implemented in lvODE. The major differences include: no support for trimesh, heighfield and convex geometries, the lack of a 2D Plane constraint, lack of gyroscopic mode for the bodies, single precision floating point numbers only.

Few words about licensing. I publish lvODE under such a restrictive license (see below), because this is still experimental phase. I’ll appreciate any feedback which could help to make this library better and more stable. My further plans are to provide less restrictive free version and full-featured commercial one. Please contact me if you are interested.

Comments on this approach are also appreciated.

Version History

v0.1.0: Initial release of the code.

Support

If you have any problems with this code or want to suggest features:

please go to lavag.org and Navigate to LAVA > Resources > Code Repository (Certified) and

search for the "lvODE" support page.

License

This work is published under the Creative Commons BY-NC-ND license (description and text of the license here and in license.txt)

ODE library is distributed under BSD license (www.ode.org)

Copyright © 2010, Wojciech Golebiowski