The hybrid ideal

Mar 2, 2007

A $75,000 grant from the U.S. headquarters of Mentor Graphics Inc. based in Wilsonville, Ore., helps Kettering University researchers develop computer models that allow automakers to design and evaluate hybrid drive trains that might make hybrids more cost efficient.

Mentor GraphicsSome scientific facts are impossible to ignore. Oil, for example, will one day dry up, leaving cars gasping on highways for one last whiff of energy.

Before the advent of automobiles, earth contained rich deposits of crude oil, from which we manufactured fuel for cars and trucks, as well as oil to heat homes and create various products. In a practical sense, such fossil fuels allowed for large-scale industrial development as our world expanded. As a result, many Americans enjoy a standard of living that would otherwise be less than satisfactory if not for the creation and use of fossil fuels.

But as the name suggests, fossil fuels will eventually evaporate, leaving humanity without one of its most prized commodities. Scientists 2,000 years from now studying our civilizations may indeed find hints of oil among the dusty and rusty shells of junked cars and trucks, and come to some understanding about the social, economic, political and even cultural power of oil during our existence.

Researchers currently examining the issue of oil consumption and alternative power today also hope that what future scientists find are sources of power that represented an eye toward developing energy independence without environmental impact. And while fuel cell power holds perhaps the most potential, we're still years away from full incorporation of this resource and hybrids are clearly more practical. Although hybrids such as the Toyota Prius and Volt by General Motors are exceptional examples of this technology, cost and the current capabilities of battery technology keep them out of financial reach of many environmentally conscious Americans.

However, this could all change based on some important research taking place at Kettering University in Flint, Mich.

Dr. Juan PimentelDr. Juan Pimentel and Dr. Jim Gover, professors of Electrical and Computer Engineering, recently took receipt of a $75,000 grant from Mentor Graphics Inc., a technology leader in electronic design automation that provides software and hardware solutions that enable electronics, semiconductor and automotive companies to design products faster and more cost efficiently. With this grant, the two professors will develop computer models of an entire hybrid drive train that will allow them to perform a complete analysis of a hybrid vehicle design. They can then determine its "functionality, lifetime, effects of component aging, EMI generation, mechanical and electrical effects of thermal cycling, cooling requirements and costs, among other things," explained Gover.

One possible impact of this computer modeling could be lower costs in terms of purchasing a hybrid in the future. Currently, hybrids cost anywhere from $3,500 to $6,000 more than traditional cars. More importantly, at the Detroit Auto Show in January, manufacturers displayed significantly more hybrid cars and trucks than at last year's show. This clearly suggests that the general public is more interested this year in hybrids than in previous years, due in large part to the increasing cost of gas.

Dr. Jim GoverUnfortunately, the adoption of hybrid electric vehicles may take time because of a number of issues. Some of these include vehicle costs, battery lifetime, and battery energy and power density. According to Gover, major advancements in battery technology could actually "make fuel cells much less critical to the future of automobiles," he said. "There is an infinite space for the design of hybrid vehicles that can range from mild hybrids to full hybrids. If cost was not a factor, one could design a hybrid vehicle that's optimized for the driving style, driving conditions and cost needs of each driver," he added.

Pimentel and Gover will focus their research efforts in this project on several areas of a hybrid drive train. One of the primary components of these drive trains are the power electronics comprised of a dc-dc converter and three-phase inverter that converts dc voltage to a three-phase, frequency-dependent voltage. This voltage then provides power to the electric motor that operates the wheels. One starting point for this grant-funded project is to model the inverter. Gover will work on developing computer models of the power electronics system, while Pimentel will model the control electronics for the inverter. Both will use the Institute of Electrical and Electronics Engineers' standard modeling language called VHDL-AMS (very high speed hardware description language-analog and mixed signal). The primary tool to be used is SystemVision ™, which is Mentor Graphics' implementation of VHDL-AMS. The hope is to calculate the heating rate generated in the inverter semiconductor switches to determine cooling requirements over the full range of drive train speeds as well as the performance sensitivity to electrical parameters.

"The VHDL-AMS language is important to this project because it can handle complex systems where there is a mixture of electrical, mechanical, fluidic, thermal and other physical phenomena," Pimentel said, adding that the VHDL-AMS language "has acquired worldwide acceptance and is the language of choice for modeling and simulation of multi-physics complex systems."

This project has a wide range of required application expertise involving different domain modeling tasks. "In addition to establishing contacts with leading experts worldwide, the project will involve a graduate student and several undergraduate students in conducting research," he said. Some of the project outcomes could potentially be incorporated into the Kettering curriculum and shared with other universities.

Ultimately, the two professors believe that another outcome of this project is a compelling reason for automotive OEMs and suppliers to consider using these types of computer models and tools. These resources could provide automotive designers the capability of designing a hybrid vehicle drive train and evaluate it without having to build the hardware, which is extremely expensive. Drive train design costs are often passed onto the sales price of a vehicle.

Gover also noted that while this project focuses on the various power electronics components of hybrid vehicles, he and Pimentel are not attempting to invent new power electronics topologies. The computer models under development should allow what he describes as the payoff of inventions "to be determined without having to build hardware. The automotive sector, which is dominated by mechanical engineers, is far too dependent on testing and underutilizes math-based simulation for electrical systems. In a hybrid vehicle, more than 50 percent of the cost is electrical. The result is that automotive manufacturers will soon find out that they simply cannot afford to contract all of their electrical systems to suppliers and only work with performance specs, which requires them to conduct expensive tests to determine if their supplier has met their specifications."

Serge Leef, general manager of the System-Level Engineering Division at Mentor Graphics, said "We believe that applying state-of-the-art multi-physics simulation technology to hybrid vehicle electronics optimization is a great way to leverage our SystemVision? product. Our team's joint activities with Kettering researchers will result in profound learning that could lead to exciting advances in the understanding of the hybrid-drive operational and cost trade-offs. Professors Pimentel and Gover have deep insights and clear vision in this area, and we look forward to long and fruitful collaboration."

And if the predictions made by this project come to fruition, the developmental costs of hybrids could indeed come down if car makers pay careful attention to how they design, simulate and evaluate hybrid vehicles. So if car manufacturers can reduce their development costs, it stands to reason that consumers should be able to buy hybrids at more efficient cost points, which could eventually reduce our need for oil and help establish the country's energy independence.

To find out more about this project, contact Dr. Jim Gover at (810) 762-9500 extension 5643, or Dr. Juan Pimentel at extension 7990.

Written by Gary J. Erwin
(810) 762-9538