04-10-2007, 06:02 AM
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Engineering first
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Real Name: Bob
Location: Huntsville, AL
Hybrids: Prius Classic 03
Posts: 5,160
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IEEE Spectrum reviews cars
http://www.spectrum.ieee.org/apr07/5012
Quote:
By John Voelcker
2008 GMC Yukon Two-Mode Hybrid
A hybrid heavy hauler
GMC’s Yukon is a strapping 2500 kilograms unloaded. In other words, it ain’t no Prius.
And yet, Yukons fitted with GM’s new two‑mode hybrid system use essentially the same principle to reduce energy consumption as Toyota’s celebrity-friendly it-car. An electric drive can power the vehicle, by itself or together with the combustion engine. The battery that powers the motor is charged by the engine and also through regenerative braking.
Being as big as it is, though, the Yukon outdoes other hybrids by having two electric drive motors, each capable of 40 kilowatts sustained. A single motor with enough torque to move such a mass couldn’t be accommodated inside the truck. So GM’s engineers, who led a design effort that later included engineers from DaimlerChrysler and BMW as well, used a pair of electric motors—a system GM had previously put into production for its hybrid transit buses. As in the Prius, the Yukon’s motors are actually motor/generators that can produce torque when fed with electricity—or vice versa.
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This is one of the better write ups on the 2-stage transmission. It sure has a lot of parts: - planetary gear set
- electric motor
- clutch
- secondary gear set
- motor
- final clutch
- four fixed gears
The other interesting statement is "70 percent of the total effort involved in designing and testing the system went toward control logic." The projected efficiency is ~22 MPG.
Bob Wilson
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