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With its unified interface, MSC.visualNastran 4D (vN4D) from MSC.Software (Santa Ana, CA), allows an engineer to complete the analysis of a system of parts/assemblies involved in multibody motion and interaction, to check its structural integrity with finite element analysis (FEA) methods, and to control it with industry standard Matlab/ Simulink.

Integration of Matlab/Simulink into vN4D provided an excellent tool for control engineers who want to couple a Simulink model to the physical world and extract meaningful results and feedback. Based on a Simulink block named vNPlant- developed for vN4D-the data 'handshake' is done between the control system in Simulink and the dynamic system in vN4D

Any meter in vN4D becomes a candidate for input and output in the vNPlant block. A new feature, 'FEA Meter,' is used to monitor FEA-related results in numerical or graphical display. Effects of these results can be used with vNPlant to trigger events and processes on the control side of the system.

Since the Simulink side of the interface drives the simulation, the animation step is key to guarantee synchronization between Matlab and vN4D. When simulating bodies in contact, use of a variable step is the solution for remaining in contact with Simulink. Unfortunately, the penalty may be increased computation time.

One of the improvements in this version is how information is set up for each part or assembly, its connections and constraints, as well as its properties (see graphic).

The new 'Paint the Constraint' concept eases this function, relative to earlier versions by specifying the starting point and dragging the constraint to the endpoint. Coupling can also be extended into the modeling. For example, a gear model can be used in a simple form to verify kinematic performance, as well as in a true form with full contact resolution to measure gear loads. Contact is treated with two possible models: a smooth surface for parts always in contact, or a faceted surface, parametrically defined for better contact detection.

The Formula Window represents one of the key parts of this vN4D version. It offers various ways to assign and extract information from models, such as position, velocity, math, logic, or prescribed functions. With built-in functions, tabular results can be created and used in the simulation.

Using a subset of MSC.Nastran (MSC's main software package), FEA capabilities of vN4D can help design engineers get a feel for the structural performance of their designs without being experts. While limited to linear models, FEA tools cover structural, steady-state thermal, modal, and buckling types of analyses with a new fast, iterative solver.

A typical procedure entails just a few steps, with solutions and results only a few mouse clicks away. FEA can be run for a single-load application, or linked to motion with dynamic loading and calculation of results for each frame. Results are calculated on demand, but the settings can be tailored for specific output. A 'Getting Started CD,' along with online context-sensitive help on any part of the program, provides guidance through new features.

Data sharing in vN4D is also seamless due to its integration with all major players in the midrange CAD market. As a result, vN4D supports geometry transfer in various formats while all constraints, loads, and boundary conditions remain intact.

vN4D targets design engineers in need of an analytical tool in the early stages of design. Without the need to rely on experts or advanced software, its capabilities go beyond these limits in many respects. For a new user, this version closes the loop on a complete analysis and simulation package.

This review is based on vN4D 2002 and Matlab/Simulink in respective versions 5.3/3 or 6.1/4.1. Hardware requirements are Microsoft Windows NT, 98, 2000, or ME, P-II w/128 MB RAM, 32 MB VRAM, and 300 MB available disk space for installation.

For more information, visit www.controleng.com or www.mscsoftware.com