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Accelerating Vehicle Testing

Steve Haeg, Principal Staff Design Engineer at MTS, discusses new laboratory testing advances that make the best use of computer-aided engineering (CAE) and physical testing to optimize both.

Q: What key challenges do today’s vehicle subsystem and component developers face, especially with so many new players entering the global marketplace?

Haeg:
The challenge is basically the same for all vehicle test professionals. They are pressed to develop better products in less time and for less money, which forces them to find new ways to accelerate their vehicle development. Subsystem and component developers do not want to wait until near the end of the development cycle to characterize the performance of their products. Waiting until such a late stage, especially after tooling decisions have been finalized, makes it expensive and time-consuming to make design changes.

Historically, test professionals have been confined to two methods for characterizing performance, each with strengths and shortcomings. First, simulation modeling and analysis using computer-aided engineering (CAE) is repeatable and allows testing to begin at a very early point during development. But it involves many unknowns and is incapable of identifying many potential issues that may arise when a part is integrated into a full vehicle. Plus, many vehicle components, such as bushings and shock absorbers, are difficult to model accurately.

The second testing method involves evaluating subsystems and components when installed in a full-vehicle prototype driven on a proving ground. Track testing is more realistic and comprehensive than computer modeling, but it is slow and non-repeatable. Another major shortcoming of track testing is that it occurs at a late stage in the development cycle. Any performance issue discovered at this point will have a dramatic impact on both budgets and schedules, and a change in one component’s design may cause a ripple effect that necessitates changes in other components and systems.

So the key to accelerating vehicle development rests in combining the speed and timeliness of computer modeling with the thoroughness and accuracy of track testing.

Q: What new advances are helping to accelerate vehicle development?

Haeg:
Mechanical Hardware-in-the-Loop (mHIL™) technology is one of the most promising advances to come along in years. Pioneered by MTS, mHIL technology closes the gap between computer analysis and track testing, by supplementing CAE with physical testing during the preliminary stages of development.

MTS mHIL technology places mechanical systems or components in the loop of a real-time vehicle model. It builds a ‘virtual’ vehicle around an actual physical component or system under development, and allows test engineers to ‘drive’ these parts under highly realistic and repeatable simulated service conditions. Specimens can be subjected to precise and thorough vehicle-level testing, long before a full-vehicle prototype is available.

Since mHIL technology uses real parts, it is far more sensitive and involves far fewer unknowns than CAE alone, leading to more effective development decisions. And it yields the same complete performance picture as track testing, only without the associated tradeoffs in time, cost and repeatability.

Q: How will vehicle developers benefit from this technology?

Haeg:
It allows them to perform accurate mechanical tests on an actual physical subsystem or component before tooling decisions are made, where time and flexibility still exist to support necessary design changes. They can leverage today’s advanced computing capabilities while depending far less on track testing to fully characterize products under development, allowing better engineering decisions to be made earlier in the game.

Such capabilities benefit suppliers and vehicle manufacturers equally. With better subsystems and components reaching the market faster and for less money, more competitive vehicle models will be able to enter the marketplace sooner.

Q: With such technology advances, might there come a day when the proving ground is no longer necessary?

Haeg:
Complete elimination of expensive prototypes and proving ground testing is the goal of most vehicle development managers. Almost every company has reduced its number of full-vehicle prototypes over the last decade, and are opting to rely more heavily on CAE and lab testing to verify product performance.

However, due to certain modeling limitations, the comprehensive environment of the proving ground is still the only way to thoroughly evaluate vehicle durability and performance. Those limitations include the inability to accurately model things like wear, degradation, fatigue, joints and connections, along with various non-linearities such as those encountered when characterizing elastomers and dampers. New materials and manufacturing methods also provide modeling challenges. For example, a rise in the use of more technically advanced materials, such as composites and plastics, requires testing in a highly realistic environment beyond the scope of laboratory simulation.

In addition, some things are still not well understood enough to be modeled. Vehicle ride and handling ‘feel’ immediately comes to mind as an example. It may one day be possible to accurately assess such performance analytically, but I don’t see that happening for at least a decade. Lab tests are no doubt getting more sophisticated, but we still have a way to go before we can have a ‘test track in a box,’ as a former test lab manager I know likes to call it.

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