However, amidst skyrocketing oil prices and a new generation of green-conscious consumers, fuel efficiency and environmental impact have become top design considerations for transportation. Engineers now face a new "green" challenge: How do you design an environmentally friendly product that also meets the traditional requirements of quality, cost, and time to market?

Armed with techniques such as hardware-in-the-loop (HIL) simulation and rapid control prototyping (RCP) as well as a new generation of measurement tools, engineers are taking advantage of new measurement and control capabilities to deliver new technologies to market and meet the accelerating demand for green transportation.

Consumers vote with their dollars, and the votes for fuel-efficient vehicles are in: Ford, GM, and even Toyota have closed or suspended SUV and truck plants in 2008. Legislative pressures are mounting as well—U.S. Federal Corporate Average Fuel Economy (CAFE) standards are proposed to rise to 35.7 miles per gallon in 2015, after remaining at 27.5 miles per gallon for the past 18 years. This combined with ever-stricter emissions requirements from both the California Air Resources Board and the U.S. Environmental Protection Agency makes delivering a vehicle to market that meets consumer expectations and these difficult requirements a daunting challenge.

Looking back several decades, today's vehicles, per kilogram, are more efficient than ever. Oil-powered engines have seen great strides in optimization, featuring elaborate emissions control systems and finely tuned calibrations. Hybrids have achieved consumer acceptance at realistic prices. Alternative fuel vehicles have been entering the market with engines capable of running on ethanol; mild ethanol-gasoline blends for use in normal engines can be found in gasoline supplies around the country. However, with all of these advancements, vehicles still emit many tons each of carbon dioxide over their lifetimes.

Role of the 'green' engineer in the automotive industry
While many industries have just started to practice green engineering, the automotive industry has been environmentally conscious for decades, becoming green to meet legislative requirements and handle competitive pressures during the first oil crisis in the early 1970s.

The role of the green engineer is more difficult than that of a traditional engineer because green considerations impact almost all aspects of a design. This includes everything from the operational impact of the product, a factor that is increasingly becoming relevant (especially for automobiles), to the end-of-life recycling of the product. Nearly every part of the design process is touched, affecting decisions in materials selection, manufacturing processes, electronics design, power train calibration, and vehicle testing.

These new factors can be difficult to justify from a business perspective. As recently as the 1990s, during the SUV boom, justifying extra development to increase mileage and reduce emissions beyond legislative requirements was a difficult task. It takes great discipline to look past the bottom line for a vehicle and take into account the big-picture life-cycle costs. Today's green engineer is aware of these issues and factors them into the design of the product.

Green automotive technologies have always been in development for a variety of reasons, ranging from complying with government standards to establishing goodwill with customers. A sense of urgency has gripped the automotive consumer as oil prices have nearly tripled in two years. Adam Smith's invisible hand is now accelerating advanced power train technologies into production at a new fervor not seen since the first oil crisis.

Optimizing the gasoline engine
Engineers are using a wide range of technologies to meet the challenge of the green automobile. It is impossible to cover them all here, but there are some notable advances that are showing both long-term and more immediate promise for improving transportation efficiency.

Advanced electronic control enhances going green
The vast majority of today's production vehicle fleet uses the venerable internal combustion engine. As it becomes more refined, realizing incremental gains is increasingly difficult because the technology is approaching its theoretical efficiencies. Early advances stemmed from mechanical improvements such as better materials, higher tolerances, and increased understanding of engine optimization. Most recent gains can be attributed to faster and more optimized electronic control of the combustion process.

Advanced control is enabling new efficiencies in engine technology that, mechanically, has remained fundamentally unchanged since the Model T. As engine controllers continue to benefit from increases in microprocessor power, more variables can be controlled in finer resolution at faster rates with higher-level modeling. With more reliable tool chains capable of taking mathematical models and converting them to production code, engineers can focus on new control strategies rather than debugging low-level controller code.

One example of advanced control making its way into production vehicles today is variable valve timing (VVT). In this advanced control technique, engines have finer control over how much and/or at which point intake and exhaust valves are actuated. VVT has been mechanically feasible for quite some time, but the more powerful engine controllers and algorithms to properly control them have only recently become available. In the past, engine designers generally chose valve configurations and timings for one optimization point, but now they can offer a wider range of both fuel efficiency and performance optimizations. Today, all of the major OEMs are producing some sort of VVT in one or more of their engine platforms to deliver both better fuel efficiency and performance.

A key enabling technique accelerating the development of advanced control is the ability to rapidly prototype controllers for engines that can make the high-speed measurements and decisions needed for technologies like VVT. This new generation of "sandbox" controllers allows engineers to implement, test, and validate algorithms much more quickly at a higher level than coding by hand in a low-level language, cutting design times and increasing innovation.

A wide variety of companies today supply hardware and software that help engineers work in higher-level graphical languages like National Instruments LabVIEW software as opposed to the low-level languages such as ANSI C and assembly, used to program production controllers.

No need for spark plugs with HCCI
A newer technology showing potential for production vehicles is the Homogeneous Charge Compression Ignition (HCCI) engine. In short, HCCI promises to combine the efficiencies and simplicity of the diesel engine with the cleaner emissions of a gasoline engine.

The HCCI engine essentially runs by actually controlling the "dieseling" effect often shown by carbureted engines that run on, stumbling, when the ignition is shut off on a hot day. The core concept of HCCI is that the engine combusts a precisely blended fuel-air mixture by squeezing it until it spontaneously combusts. This differs from gasoline, which uses a spark to initiate the combustion, and diesel, which sprays fuel into already-compressed hot air to begin combustion. The result is an engine that becomes completely dependent on the control algorithm, which has to continually monitor and adjust the fuel-air mixture nearly every cycle of the engine.

Today it is possible to make an HCCI engine that works at specific operating points, but the core of the problem is controlling exactly how much fuel and air are allowed into the cylinder given its exact speed and temperature as well as the characteristics of the air and fuel. Other variables can be introduced as well, such as varying the compression ratio. With so many variables and many outputs, complex and powerful control algorithms are needed to produce a usable engine on this technology.

One of the challenging parts of HCCI is to determine when the combustion actually happens in relation to the position of the cylinder. This is an area that modern high-speed measurements have benefitted. With the ability to synchronize high-speed vision and pressure measurements at hundreds of kilohertz to the crankshaft position, engineers are able to observe how well their control algorithms are working to optimize HCCI. New technologies such as high-speed, high-resolution analog-to-digital converters (ADCs) and user-programmable FPGAs give engineers new ways to observe the results of their control. HCCI technology is showing great production potential. GM has demonstrated a prototype Vauxhall Vectra HCCI model that is expected to be 15 to 20% more efficient than standard gasoline engines.

Part 2 of this article discusses transitioning from oil with plug-in hybrids and hydrogen fueled vehicles.

Paul Mandeltort is automotive product manager at National Instruments.

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