Advanced systems aim to keep new cars running clean
WEST LAFAYETTE, Ind. Purdue University and Ford Motor Co. are teaming up to develop an advanced, onboard electronic system designed to monitor the health of aging engines and keep cars in compliance with stringent exhaust-emission standards.
Findings from the research ultimately could make possible the creation of sophisticated diagnostic systems that not only warn the driver about impending engine failures but also identify the likely sources of the problems, says Matthew Franchek, an associate professor of mechanical engineering at Purdue.
The technology works by using newly developed computer models to better control how much fuel is delivered to the engine. It has the potential to eliminate certain expensive and time-consuming steps now needed to develop electronic-fueling controls for new engines.
A paper about the fueling control research will be presented on Aug. 23, during the 5th International Symposium on Advanced Vehicle Control, a gathering of researchers specializing in automotive and rail technologies, at the University of Michigan in Ann Arbor.
Cars equipped with modern electronic control systems are able to meet increasingly strict pollution standards by automatically adjusting how much fuel is delivered to the engine. The control system is said to "adapt" the engine fueling to changing situations, such as climbing steep hills, variations in driving speeds and sudden accelerations. At the heart of this adaptive-fueling control system are electronic chips that have been carefully programmed to deliver the right amount of fuel to the engine, depending on how much air it is using. With conventional technology, automotive technicians and engineers calibrate these chips for each line of new engines to precisely meter the amount of fuel for a wide range of driving conditions.
When this "engine mapping" process is completed, the electronic-control system will determine how much gasoline the fuel injectors will deliver to the cylinders as the car travels down a highway, idles at a red light or labors up a steep incline. The ratio of air to fuel is tightly controlled to meet emission standards regardless of the driving conditions.
"It takes a long time to map an engine," Franchek says. "There are thousands of parameters to calibrate in an engine-control system, including transmission, fueling, idle speed, diagnostics, everything that the engine does."
The control technology being developed at Purdue promises to eliminate the engine-mapping process altogether, saving time and money by using newly developed mathematical models.
In addition to the engine-mapping requirement, current technology has another drawback: as an engine ages its performance no longer matches the carefully calibrated data programmed into the electronic control system. Clogged fuel injectors, the changing performance of engine sensors and a variety of age-related factors conspire to foul up the precise fuel-to-air ratios needed to meet pollution standards, causing the car's tailpipe emissions to increase.
In an attempt to correct the emissions, conventional electronic systems try to assign a root cause of the fueling-control errors so that the system's software can adapt. Based on the root-cause assignment, the fueling control system will correct itself by changing the amount of gasoline being injected into the cylinders. Unfortunately, the root cause assigned by the system is often inaccurate. Consequently, the corrective action is wrong.
The fueling control system being developed at Purdue is now being extended to enable car makers to overcome that problem by more accurately assessing the root causes behind changing engine performance. A more accurate assessment makes the system better able to adapt to changes in aging engines, while also reducing maintenance costs by automatically keeping the engine running smoothly, Franchek says.
"In the end, the fueling software will adapt itself to deliver fueling to the correct value," says Franchek, noting that the system is designed to last over the life of the engine.
Source: Matthew Franchek, (765) 494-5714, firstname.lastname@example.org
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PHOTO CAPTION: PHOTO CAPTION: Matthew Franchek works on a Ford engine being used for Purdue's fueling-control research. (Purdue News Service Photo by David Umberger)A publication-quality photograph is available at the News Service Web site and at the ftp site. Photo ID: Franchek.engines
Transient and Steady-State Adaptive Fueling Control
David J. Stroh and Matthew A. Franchek, Purdue University,
Presented in this paper is an adaptive, model based, fueling control system for spark-ignition internal combustion engines. Since the fueling control system is model based, the typical engine maps currently used in engine fueling control are eliminated. This proposed fueling control system is modular in structure and can therefore easily accommodate changes in the engine sensor set such as replacing the mass-air flow sensor with a manifold air pressure sensor. The fueling control system is also parceled into steady state fueling compensation and transient fueling compensation. This steady-state feed-forward controller is comprised of two nonlinear models capturing the steady state characteristics of the fueling process. These models are identified from an input-output testing procedure where the inputs are fuel pulsewidth and mass-air flow signal and the output is a lambda signal. The transient fueling compensation also utilizes a feed-forward controller that captures the essential dynamic characteristics of the transient fueling operation. Essentially, this controller is measured using a frequency domain system identification approach. This proposed fueling control system is demonstrated on a Ford 4.6L V-8 fuel injected engine.