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.
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, petrol-powered cars, said Giorgio Rizzoni, professor of mechanical engineering and director of Ohio State’s Centre for Automotive Research and Intelligent Transportation.
‘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 computerised 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 petrol 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 computerised control system. 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 optimised the power split between the engine and electric motor.
The truck is said to have achieved an average fuel efficiency of almost 22 miles per gallon – 50 percent more efficient that a traditional petrol-powered Suburban.
Guezennec, who drove the FutureTruck, said the feel of the car was the same as a typical Suburban.
The researchers also found 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.
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.