When the Whole Is Less Than the Sum of the Parts

Article From: 12/15/1997 Automotive Design & Production, , Editor-in-Chief from Gardner Business Media, Inc.

Mechanical interactions can have negative effects that may not seem obvious when discrete elements are being designed for assemblies. One software company has the means by which these subtractive characteristics can be eliminated before physical models are produced.

Mechanical interactions can have negative effects that may not seem obvious when discrete elements are being designed for assemblies. One software company has the means by which these subtractive characteristics can be eliminated before physical models are produced.

ADAMS/Car CAE software

Through the use of ADAMS/Car CAE software, Ford (Mechanical Dynamics' largest customer) can design and build better sport utes.

Someone makes part A. Someone else makes part B. Both parts are made to spec. Parts A and B are components that, when put together, create mechanism C.

So, given what you know about parts A and B, what can you assume about mechanism C?

Probably that mechanism C will probably work as designed. After all, the components were made to spec.

But according to Robert R. Ryan, president and COO of Mechanical Dynamics, Inc. (Ann Arbor, MI), that assumption may be a faulty one. In fact, it probably is incorrect. As he puts it, "You can't make two perfect parts and expect that the sum of the two will be great. There are interactions that occur." And it is the interactions that the software developed by Mechanical Dynamics has been created to analyze.

The software is called ADAMS. There is a specific auto vehicle simulation package, ADAMS/Car, that was developed by Mechanical Dynamics along with a consortium of automakers; the original consortium included Audi, BMW, Renault, and Volvo. The software is capable of providing information about suspension, vehicle dynamics, engine, powertrain, noise, vibration and harshness (NVH), handling and ride, tire-roadway interaction and more in a fraction of the amount of time that it would take to obtain this by using more traditional methods. Not only is it faster to create models in software on a workstation or PC than it is to create a physical prototype in a model shop, it is a whole lot more inexpensive.

Ryan says that by building "virtual prototypes" in place of some of the physical models (he recognizes that there is still a desire to have something you can hold in your hands in addition to something you can view on a screen in all of its animated glory), companies can expect to realize shorter development times, higher quality, lower costs, and the ability to deal with more complex systems.



Fundamentally, the ADAMS/Car computer-aided engineering (CAE) software makes use of the digital information that is already, undoubtedly, stored within computer-aided design (CAD) and product data management (PDM) systems. So it isn't necessary to start from scratch.

Generally, they're working at a subassembly level. What they are doing with this physics-based software package is determining how the subassembly will work given a set of parameters. It is not only simulating what the subassembly will look like, but it is also testing. By building up subassemblies into assemblies and further testing, it is not only possible to determine performance but to see where there are problems and what can be changed in order to resolve them. That is, when there are interactions between various parts, it may be possible to make an adjustment to something that is not immediately interacting with the area in question and thereby resolve the problem. The CAE software that Ryan's company offers permits this to happen.


More-effective Testing

Speaking of general practices in the physical prototyping world, Ryan says that often times, testing can't be used to its fullest extent because of time constraints. But with the computer-based approach, when the assembly is being tested while it is still in a digital form, it is much simpler to accommodate these changes. "We're not suggesting that physical testing be eliminated. But we are making it more effective." At the very least, some problems can be solved before the prototypes are fabricated. Then the testing can be used to more closely optimize the product before its design is released for build. "Engineers can use the information they obtain with confidence," Ryan comments.

According to Ryan, companies that are using the software are realizing huge savings. Not only does it help create better products, but there are significant savings in manufacturing costs, as well. For one thing, since the simulation catches problems early in the development cycle, it is less likely that there will be engineering change orders coming down—after the tooling has been produced.

Ryan says that there are fundamentally five phases of auto design. First, it was a matter of building vehicles, then taking them out hither and yon and seeing how (or if) they'd perform under various conditions. Next, to do away with some of this expense in time and travel, proving grounds were built. These were bolstered by the construction of corporate test labs. Companies are now in the fourth stage: computer simulation and virtual prototyping. What's to come? "Immersive design," Ryan answers. This means virtual reality prototyping.

In the closer-term, Ryan says they're looking at Java—which could put the CAE product on the web so that there can be far-flung collaborative virtual prototyping among engineers.