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Working Model 3D

DN Staff

September 9, 1996

4 Min Read
Working Model 3D

Working Model 3D (WM3D) is a 3-D dynamic simulation program that models rigid body behavior. It models constraints between bodies, and automatically detects collisions among constrained and free bodies.

Objects can be created within WM3D or can be imported from ACIS solids. Constraints are attached to user defined local coordinates (construction points). Automatic assembly implements constraints that require body motion for completion.

Models are displayed in wireframe, hidden line, or speed-optimized Gouraud shaded format. Multiple viewports are available, with independent view format, size, and view aspect control. Animations can be saved in Windows .AVI format.

Editing controls are sparse, simple, and easy to learn. It took only a few hours to become familiar with a majority of WM3D's features, and simple, free body collision experiments can be run almost immediately.

Simulation output data is displayed as graphs or digital "meters", with each occupying a single window. These output windows can be printed individually; however, there is no provision for single sheet output of multiple model and data windows. All output data can be written to an ASCII file for import and consolidation by other Windows applications. The version I reviewed was limited to writing four windows at a time; however, Knowledge Revolution offers a fix to this limit.

There are no run-time controls, so model behavior must be pre-programmed through model parameter functions. Although this inhibits interactivity, I found practical means of controlling most models.

Model and constraint construction and editing are precise, using a local coordinate system that may be attached to user-defined construction points. The approach is flexible, with position coordinates displayed and editable in both local and world coordinates.

Collision detection is one of WM3D's strongest features. The user need only specify which bodies are allowed to collide. No pre-definition of collision points is needed. Collisions are analyzed using variable values of coefficients of restitution and friction. Extremely complex, multiple-body interactions can be analyzed with ease. Note that bodies in WM3D are composed of plane surfaces (facets), and collision detection monitors interaction of these surfaces. For example, a wheel constructed as a cylinder with coarse faceting will bump as it rolls. The solution is to use finely faceted models in regions where curved surfaces interact. Only WM3D's sphere models collisions of an analytical, curved surface.

I couldn't resist constructing a 3-D pool table. With table and cue from AutoCAD and balls constructed in WM3D, model construction took just over an hour. The result--a break with realistic cue impact and ball, rail, and pocket interaction. It took about 13 minutes to simulate the cue and 16 balls through a 500-step full break on a 133-Mhz Pentium.

WM3D's constraints are basic, but adequate to model a wide variety of mechanisms. I modeled a multi-degree-of-freedom 3-D mechanism that was previously solved analytically--taking several weeks for a very talented analyst. I modeled it in WM3D in a few hours (it was my first complex model), and obtained static solutions that agreed with the closed-form analysis to three significant figures. The only differences occurred in an indeterminate linkage where the analyst had made assumptions of force distribution to add equations. WM3D ignored excess constraints.

While WM3D needs marked expansion in printed output flexibility and in interactivity, and many improvements to increase productivity, this first release is robust and provides a valuable tool for analyzing a variety of 3-D problems. Its ease of use and immediate visual out-put make it an ideal conceptual design tool. Its numerical output is adequate for a wide variety of quantitative analyses as well.


Working Model 3D

Working Model 3D is a 3-D dynamics simulation program for Windows 3.11, 95, and NT. It requires a 486/66 processor and 8M bytes RAM with a Pentium and 16M bytes of RAM strongly recommended. All files supplied occupy 32M bytes of hard disk. The software is distributed on CD-ROM and uses a hardware key.

List Price: $5,500 and up

Knowledge Revolution, 66 Bovet Rd., Suite 200, San Mateo, CA 94402; ph: 800-766-6615; fax: 415-574-7541; http://www.krev.com

A similar product:

DADS - CADSI, 2651 Crosspark Rd., Coralville, IA 52241; ph: 319-626-6700; fax: 319-626-3488.

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