Sequel Test Drive, Part 2: Background
The Sequel is GM's third step in reinventing the automobile around hydrogen. From the beginning, engineers did not want to develop a system where the fuel cell could be adapted to existing vehicles across the GM line.
"We wanted to build a vehicle completely around the fuel cell," Chris Borroni-Bird told journalists at a recent test drive arranged for journalists in
The AUTOnomy concept vehicle was first shown at the 2002 Detroit Auto Show. It was a show vehicle only to demonstrate the "skateboard" idea that the propulsion system could be neatly packaged in a 6-inch-thick platform underneath of a variety of body styles. Ideally, such a chassis could support an economy car as well as a luxury limo and it should be able to support vehicles in different world markets.
It was designed as an all-wheel-drive vehicle with motors at each wheel. It also incorporated by-wire features but the AUTOnomy was never a driver. It was simply a design concept to provide a vision of the future and give engineers a starting point.
A few months later at the Paris Auto Show, the Hy-Wire was shown. It too used a skateboard chassis, this time 11 inches thick, but had a more traditional single motor to drive the front wheels. The Hy-Wire was also a more advanced test bed for steering and braking by-wire. Unlike the AUTOnomy, the Hy-Wire was built to be a test vehicle and to show off innovative features such as the X-drive steering wheel that could move from left or ride side in a few seconds. The vehicle also didn't have foot pedals: all engine controls and braking were handled with the X-drive controls. The Hy-Wire also had a more traditional body style and amenities for vehicle occupants.
"Then we had to make a real car," said Borroni-Bird, who is director of design and technology for the Fusion Group at GM and the lead designer of the Sequel. "But we didn't want the technology in the driver's face."
Key to the acceptance of fuel-cell vehicles is range. The Sequel was designed with three storage tanks capable of holding eight kilograms of hydrogen, or the equivalent of eight gallons of gasoline for a 300-mile range. The main tradeoff was that the center tank invaded the passenger space slightly requiring a tunnel between the seats.
The Sequel uses GM 4th-generation fuel cell, motor and interface technology with a front-wheel-drive motor and separate wheel motors for the rear wheels. It's powerful enough for 0-60 times in the 10-second range. The by-wire technology means there is no direct mechanical or hydraulic link between the steering and brake systems. The driver turns the steering wheel in a traditional manner and applies the brakes as usual, but all the signals are electronic and programmable.
Next: Test driving the Sequel
Reader Comments (Page 1 of 1)
Howard Lee Harkness 2:47PM (9/18/2006)
"The by-wire technology means there is no direct mechanical or hydraulic link between the steering and brake systems."
Can anybody say, "Single point of failure"?
I see that some of my postings on the extreme hazards of hydrogen have been deleted. I'll be watching for how long this one lasts.
Using hydrogen to power cars is insanely stupid. Doing so with a system with no mechanical backup for steering or braking is even worse. The redundancy needed to achieve acceptable reliability would be prohibitively expensive -- which I regard as a GOOD thing. The expense will keep people away from it.
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Jimmy 4:49PM (9/18/2006)
For what it's worth, many vehicles already have "throttle-by-wire" systems and some Mercedes use a "brake-by-wire" system. Both systems have no mechanical connection for the controls.
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Tim Russell 10:35AM (9/19/2006)
Jimmy when it comes MB brake by wire system if it fails there is a mechanical backup system.
While fly by wire works in aircraft that are covered by FAA regs on how often they are serviced etc. I worry about their use in cars, many people don't service their vehicles often and I have even seen cars with failed suspension systems on the side of the road. Throttle control is no problem as if it fails you don't go and even if the trottle went wide open you can shut off the car. Braking and steering fill me with FUD (Fear Uncertainty and Doubt).
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Adam 1:14PM (9/19/2006)
Mechanical and hydraulic systems imply moving parts. Drive by wire systems use electronic signals which has no moving parts. As a rule of thumb, systems with no moving parts are 10x more reliable than systems with moving parts.
I am sure the engineers would have thought about having no single point of failure when it comes to braking and steering.
If we can have a triple fully redundant systems, your safety driving such a vehicle would be an order of magnitude better than whatever is driving on the road today. I would much rather drive such vehicle compared to the cars we drive today.
If you worry about servicing, which is better, having a mechanical car that needs service every 18 months or having an electronic car that only needs service every 180 months/15 years?
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Phil 2:57PM (9/19/2006)
Don't anybody dare use brake-by-wire by itself. EVER!
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