Simulate and analyze your designs for fast product development

With its unified interface, MSC.visualNastran 4D (vN4D) from MSC.Software (Santa Ana, CA www.mscsoftware.com), 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 software from The MathWorks (Natick, MA www.mathworks.com).

09/03/2002


This article is an expanded version of the September 2002 Control Engineering Software Review department .

With its unified interface, MSC.visualNastran 4D (vN4D) from MSC.Software (Santa Ana, CA www.mscsoftware.com), 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 software from The MathWorks (Natick, MA www.mathworks.com ).

Integration of Matlab/Simulink into vN4D provides 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.


Fig. 1A: vNPlant block definition.

Input and output controls in vN4D are read in Simulink via the vNPlant block, as shown in the first graphic. Part A of the diagram defines a vNPlant block, while placement of vNPlant within the Simulink block diagram is shown in Part B. Any meter in vN4D is 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 is driving the simulation, the animation step is the key to guarantee synchronization between Matlab and vN4D. When simulating bodies in contact, use of a variable step-along with vN4D's robust solver-is the solution that allows retaining communication with Simulink. Unfortunately, the penalty may be increased computation time.

Numerous new features

One of the improvements in vN4D's 2002 version is on its desktop. This includes the way information is set up for each part or assembly, its connections and constraints, as well as its properties. vN4D's custom templates for different classes of problems offer the best way to take advantage of the many settings for units, material, geometry, FEA, and contact (see second graphic). Due to the number of settings, use of tabs and the object browser gives users access to input/output lists, annotation, and animation controls.


Fig. 1B: Simulinkblock diagram with vNPlant.

Constraints are much easier to create relative to earlier versions of the software. With the new "Paint the Constraint" concept, users simply specify the starting point and drag the constraint to the endpoint. Coupling also can be extended into modeling belt and gear mechanisms in true part representation. 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 simulation or analysis is treated with two possible models: 1) as a smooth surface for parts always in contact, or 2) as 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 your models, such as position, velocity, math, logic, or prescribed functions. With built-in functions, tabular results can be created and used in the simulation. Formula Window also is an integral part of the Annotation text where a calculated rule can be attached to the selected note and display information on the fly.

FEA as well


Fig. 2: vN4D desktop.

Using a subset of MSC.Nastran (MSC's flagship software package), FEA capabilities of vN4D can help design engineers get a feel for the structural performance of their designs without being experts, or having to resort to advanced capabilities. Although limited to linear models, FEA tools allow you to complete 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 the proper material properties assigned, a candidate part for FEA simulation is meshed with nodes and elements, suitably constrained, and loaded. Solutions and results are only 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. Part of the software package is a "Getting Started CD," along with online context-sensitive help on any part of the program that steers you through the new features.

Data sharing in vN4D is also seamless due to its integration with all major players in the midrange CAD market. This allows vN4D to be launched from within SolidWorks, a product of SolidWorks Corp. (Concord, MA www.solidworks.com); Electronic Data Systems Corp's (Plano, TX www.eds.com) Solid Edge; and Autodesk Inc.'s (San Rafael, CA www.autodesk.com) Inventor, or Mechanical Desktop. As a result, vN4D supports geometry transfer in various formats while all constraints, loads, and boundary conditions remain intact.

Although MSC.Software targets this package for design engineers in need of an analytical tool in the early stages of design, without the need to rely on experts or MSC's advanced software, capabilities of visualNastran 4D go beyond these limits in many respects. For a new user, this version literally 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. Pricing for single user or network is $8,000. Other options include lease on demand or online subscription with monthly or weekly rates.

Paris Altidis is a staff engineer at Borg Warner Automotive, Chicago, IL. Contact him at paltidis@ats.bwauto.com

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

Click www.vn4d.com/basket/ for a live link to an online tutorial that shows an example application of MSC.Software's vN4D and Matlab/Simulink





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