GM's 'Autonomy' skateboard-like concept raised a few eyebrows at the NAIAS show in Detroit last month. But the thinking behind it is revolutionary and something like it could provide a platform for the fuel cell powered cars of the future. Autonomy reflects the fact that a fuel-cell stack can be made flat and thin; if form follows function in good design, then Autonomy could be a precursor to the vehicle platform of the future. It could also be the springboard for a lot of new ideas.

When Rick Wagoner, President and CEO of General Motors Corp., asked a simple "What if?" question, the answer he got surprised him. It's a futuristic concept vehicle called Autonomy. "We started with the premise, 'What if we were inventing the automobile today rather than a century ago? What might we do differently?'" Wagoner said. "Autonomy is more than just a new concept car; it's potentially the start of a revolution in how automobiles are designed, built and used."

Designed ground-up from the fuel cell

GM claims that Autonomy is the first vehicle designed from the ground up around a fuel cell propulsion system and the first to combine fuel cells with x-by-wire technology, which allows steering, braking and other vehicle systems to be controlled electronically rather than mechanically.

According to Larry Burns, GM Vice President of Research and Development and Planning, the result is an entirely new vehicle architecture that is far greater than the sum of its innovative parts. With Autonomy, multiple all-wheel-drive vehicles could be built from a limited number of common chassis - possibly as few as two or three - emitting only water from the tailpipe and using renewable energy.

Burns added: "If our vision of the future is correct - and we think it is - Autonomy could reinvent the automobile and our entire industry. Autonomy is not simply a new chapter in automotive history. It is volume two, with the first hundred years of the automobile being volume one. The 20th century was the century of the internal combustion engine. The 21st century will be the century of the fuel cell."

Form and function

In any good design, form should follow function. With a petrol or diesel powertrain, most automotive engineers have opted for an engine compartment at the front of the vehicle, and a driveshaft that delivers power to the wheels. A passenger compartment sits behind the engine, and a luggage space is installed behind the passengers. It's the classic three-box passenger-carrying automobile.

But arriving at an optimal version of this design took time. The first horseless carriages looked very similar to the horse-drawn models from which they had evolved, and it was decades before they shook off the essential boxiness that resulted. General Motors' top managers do not want to repeat that process if fuel cells take over.

More flexible layout with fuel cells

A fuel cell combines hydrogen with oxygen to produce water and a flow of electric current. That electricity can be used to operate a motor, or, in the case of Autonomy, four motors—one attached to each wheel. In addition, unlike the power-generating elements of internal-combustion engines (the cylinders), which have to be arranged in a precise geometrical relationship with each other, fuel cells can be arranged more flexibly, so long as the wiring is correct. That means they do not necessarily have to be lumped together as an engine block, in the way that cylinders must.

Autonomy reflects the fact that a fuel-cell stack can be made flat and thin.

The prototype is barely 15cm thick, although it is as long and wide as a conventional chassis. It contains not only the fuel cells and the storage system, but the motors, suspension and electronic control system. As GM envisages the concept, vehicle bodies would not only be manufactured separately from the chassis, but might even be sold separately. That would be possible because, rather than having mechanical links from controls to working parts, a motorist behind the wheel of Autonomy would be driving by wire without mechanical linkages.

The Autonomy concept provides a vision of the potential of the coming hydrogen economy. "With a hydrogen economy, we have a major opportunity for sustainable economic development, which respects the environment and creates the path to non-petroleum and renewable energy sources without constraining economic growth," Burns said. "From my perspective, GM is in an excellent position to lead the race to sustainable mobility."

Increased customer value

Just as GM's experimental Firebird I, II and III vehicles of the 1950s showed a vision of the future, Autonomy provides a glimpse into GM's revolutionary vision for the 21st century: a socially responsible, infinitely adaptable and globally marketable vehicle line that has minimal design constraints.

"A lot has been written about the potential of fuel cell technology and the hydrogen economy to address energy and environmental challenges. Autonomy has the potential to reduce petroleum consumption, decreasing emissions and increasing our energy independence," Burns said.

Since a fuel cell propulsion system is about twice as efficient at an internal combustion engine, a fuel cell vehicle could provide twice the fuel efficiency of a comparably sized conventional vehicle, and an optimised fuel cell vehicle like Autonomy would be even more efficient.
 
"Achieving energy and environmental improvements are extremely important objectives in and of themselves, but the Autonomy concept promises much more," Burns added. "By synergistically combining fuel cell and x-by-wire technologies, we can provide a totally different value proposition for our customers.

"Autonomy's breakthroughs in vehicle design, versatility and features will inspire our customers to want to buy fuel cell vehicles because they are so exciting and offer more for the money than today's conventional vehicles. This new concept can help us realize important societal benefits, such as renewable energy and minimal emissions, while allowing customers to buy the kinds of vehicles they want with no compromises."

Unprecedented design freedom

With all of its propulsion and control systems contained within a six-inch-thick skateboard-like chassis, the vehicle body is freed from traditional design requirements.

"There's no engine to see over," explained Wayne Cherry, GM Vice President of Design. "People could literally sit wherever they are comfortable. Drivers wouldn't have to sit in the traditional left-hand location. They could move to the centre of the vehicle or they could move much closer to the front bumper or further back.

"It will take a little getting used to, but it's maximum freedom, maximum space for people and their stuff. There wouldn't be foot pedals or a steering column. The body shape could be literally anything you want it to be."

This would lead to customised bodies and perhaps more individualised expression, Cherry said. In fact, a customer could lease multiple bodies and swap them out throughout the week, depending on their needs.

"We've chosen this sleek, futuristic two-seater, but it doesn't have to be that way at all," Cherry said. "Next, we might do a mobility body that allows a wheelchair user to roll right into the driving position, or a 10-seat transit bus. We've even talked about a seating position that puts the driver right up front, like a helicopter pilot. "

In developing nations, one chassis might be the common base for vehicles as diverse as luxury limousines or farm vehicles. In urban Asia, the platform might support a jitney bus; in rural Africa, it might be used as a reliable, environmentally friendly tractor.

A new way to build and sell vehicles

Autonomy would dramatically affect the way vehicles are built, distributed and even marketed.

All of Autonomy's essential systems, including the fuel cell stack and on-board hydrogen storage system, are packaged in the skateboard-like chassis. The unit is intended to last for years, much longer than a conventional vehicle. This universal "skateboard" chassis simplifies manufacturing and service, and enables a wide variety of vehicles to be built on a small number of platforms with much shorter product development cycles.

The nerve centre of Autonomy's electrical system is a universal "docking port," or connection, at the centre of the "skateboard" chassis. The docking port creates way to connect all of the body systems - controls, power and heating - to the rolling chassis. That makes the vehicle body lightweight and uncomplicated. With customised bodies that are easy to switch, customers could lease multiple body styles, depending on their needs.

Because computers and software control the x-by-wire systems, upgrades can be downloaded to improve vehicle performance or tailor handling to suit a particular brand character, body style, or customer preference.

"The car or truck would not only be transportation, but would also be a power source," Burns added. "Imagine the impact of a vehicle that can provide transportation, power or heat. And we've only scratched the surface of what this idea might do." GM has partnered with SKF to develop the x-by-wire technology for Autonomy. Italian-based Bertone is another key supplier.

New technology confers added benefits. From a safety perspective, the "skateboard" chassis creates an unusually low centre of gravity without sacrificing ground clearance. This gives it superior handling while resisting rollover forces, even with the tallest body attached. In a crash, the stiff chassis below the floor would absorb most of the crash forces, helping to prevent passenger compartment intrusion that can occur with today's internal combustion engines, steering columns and foot pedals.

Autonomy's potential

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"By combining fuel cells and x-by-wire, we can explore the design, use and marketing of transportation devices that truly give our customers what they want - regardless of where or how they live now or in the future," Burns said. "This is the first concept vehicle that captures the vision and potential of where fuel cell technology will lead the industry in every region of the world, well within the lifetimes of most of the people who will be visiting this show.

"This is a global vision because GM and its alliance partners have an unparalleled ability to design and build vehicles all over the world. "Some people think the auto industry is mature, with evolutionary innovation and slow growth," said Burns. "But the Autonomy concept reinforces the incredible growth potential of the automobile industry worldwide. What if the entire world could affordably enjoy as much mobility freedom as the developed world does today? Add to that the ability to power up your home or your farm from your vehicle. With these capabilities, Autonomy may prove to be as important as the original invention of the automobile.

"More than 100 years after the automobile's invention, only 12 percent of the world's population currently enjoy its benefits. The Autonomy concept, we believe, could be the foundation for extending the benefits of personal transportation to the remaining 88 percent of the world's population."