New Computer Control System For Hybrid SUV

Ohio State engineers develop new compute control system that can increase sport utility vehicle by 50 percent, while maintaining comparable performance.

Published: 18-Jan-2002

COLUMBUS, Ohio, Jan. 16 () -- Engineers at Ohio State University have developed a computer control system for hybrid electric vehicles that can make even fuel-hungry sport utility vehicles (SUVs) more environmentally-friendly -- and lower gas pump costs, too.

Road tests confirmed that the control system increased the fuel efficiency of a sport utility vehicle by 50 percent, while maintaining comparable performance.

This work demonstrates that energy-efficient hybrid cars can retain the high-performance "feel" of traditional, gas-powered cars, said Giorgio Rizzoni, professor of mechanical engineering and director of Ohio State's Center for Automotive Research and Intelligent Transportation.

Better control systems could make hybrid electric vehicles -- cars which run on a combination of an electric motor and a scaled-down version of a gas engine -- more attractive to future car-buyers.

"The success of tomorrow's hybrid electric vehicle depends on whether it offers the performance -- the 'feel' -- that drivers expect," Rizzoni said. "The question is, can you make a hybrid car feel just like a traditional car?"

In modern vehicles, a computerized control system manages engine performance, fuel consumption, and emissions. In a hybrid vehicle, the control system is even more crucial to its operation, explained Yann Guezennec, associate professor of mechanical engineering.

"Normally, when a driver presses on the accelerator pedal, that request for power goes directly to the engine, and the car accelerates. But a hybrid vehicle must interpret what the driver wants, and decide whether to send that command to the gas engine alone, to the electric motor alone, or any combination of the two," he said.

"These decisions must be transparent to the driver so that the performance of the car doesn't feel any different," Guezennec continued. "And these decisions must occur every millisecond that the car is running."

Based on numerical simulations and in-vehicle tests, the engineers created a computerized control system that they describe in the current issue of the Journal of the Society of Automotive Engineers of Japan. Their co-authors included Gino Paganelli, a postdoctoral researcher, and Gabriele Ercole and Avra Brahma, both graduate students.

They installed their control system in Ohio State's FutureTruck, a 2000-model Chevy Suburban outfitted with hybrid electric technology. They drove the truck on a 22-mile route in and around Columbus, on highways and city streets, while algorithms in the control system optimized the power split between the engine and electric motor.

The truck achieved an average fuel efficiency of almost 22 miles per gallon -- 50 percent more efficient that a traditional gas-powered Suburban.

Guezennec, who drove the FutureTruck, said the feel of the car was the same as a typical Suburban.

Another bonus: the batteries that powered the FutureTruck's electric motor remained charged at the ideal level -- between 60-80 percent of capacity. These batteries are meant to recharge while the car is moving, Guezennec explained, so they never fully empty, and drivers needn't bother to recharge them.

Honda and Toyota are already selling small to midsize hybrid cars, and doing so at a loss, Rizzoni and Guezennec said. The addition of an electric motor and batteries, as well as the associated technologies that make a hybrid vehicle work, increase the cost of manufacturing a car by several thousands of dollars.

Despite the higher cost, American automakers will debut the first hybrid versions of sport utility vehicles (SUVs) and light trucks in the next few years.

SUVs are among the most popular in America. In the 2001 model year, half of the top ten vehicles sold were SUVs or light trucks. Roughly 2.6 million such vehicles were sold that year, according to automakers.

Guezennec said that these large, popular vehicles are ideal choices for introducing hybrid technology.

That's because drivers don't typically utilize trucks and SUVs to their full potential. Though both possess a strong engine capable of towing a heavy trailer, the average American family uses its truck or SUV only for basic transportation.

"When a great deal of the engine power is already going to waste, we can achieve significant gains by using hybrid technology instead," he said. The profit margin on these vehicles is large enough that automakers can more easily absorb costs of hybrid technology, Guezennec added.

As these new vehicles are designed, computer simulation models such as the ones the Ohio State engineers used can make the process easier, Rizzoni said.

"If designing hybrid vehicles were just a matter of putting together some new components, the auto industry could do that very well. But we add value by offering an array of tools that help with all-over vehicle design and development. That's why we think Ohio State is truly a leader in this area."

Though the Ohio State engineers developed their control system specifically for the Chevy Suburban, Rizzoni said it could be adapted to suit any model of hybrid vehicle.

"We've solved the control problem in a generic sense. We could change a few details to fit a different class of car, but the fundamentals would stay the same," he said.

Currently Rizzoni, Guezennec, and colleagues are working on the next generation of the Ohio State FutureTruck -- a 2002-model Ford Explorer.

Rizzoni said the researchers are also turning an eye to the next frontier: the incorporation of fuel cells into the hybrid electric vehicle. Because fuel cells convert hydrogen into electricity and produce no pollution, they could one day replace gas-powered engines altogether.

"We are working on both immediate and long-range vehicle technologies," he said.

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