Compact and powerful electric motors are integrated into the transmission and work with traditional transmission gears and electronic controls to provide two modes, or ranges, of infinitely variable gear ratios. The input split mode is used for launching the vehicle from a stop, driving at low speeds and providing better performance and moderate load trailer towing. The compound split mode is used primarily when the vehicle is at higher speeds, to provide efficient cruising.
''The AHS2 drive modes alternate seamlessly between the input split mode and a compound split mode,'' Stephens says. ''In the input split mode the vehicle can operate on electric, mechanical or a combination of the two. The vehicle operates as a full hybrid when the engine is shut off at low speed and light loads, as leaving the engine off for extended periods of time and moving under electric power is key to reducing fuel consumption in stop and go traffic.''
As complicated as the technology is, ''It all happens without the driver realizing it," says Larry Nitz, executive director of GM's hybrid program. ''AHS2 simply optimizes power and torque for the given driving conditions, and all the driver feels is the satisfaction of low fuel consumption and the exceptional reserve power and performance."
The addition of a second mode to the drive system improves efficiency and reduces the need for the ''exceedingly large electric motors'' that are typical of today's single-mode systems, says Nitz.
''Typical single-mode systems depend on large electric power loops between two large electric motors, resulting in inefficiency and ultimately less continuous power,'' says Nitz. ''AHS2 delivers seamless, dependable power on demand and in a more efficient power flow -- and is packaged with motors less than half the size of single-mode systems.''
A sophisticated controller determines when the vehicle should operate in either mode of the two-mode drive system, Nitz explains. The system is meant to be as seamless as it is compact and flexible, he says.
photo:General Motors
''The AHS2 drive modes alternate seamlessly between the input split mode and a compound split mode,'' Stephens says. ''In the input split mode the vehicle can operate on electric, mechanical or a combination of the two. The vehicle operates as a full hybrid when the engine is shut off at low speed and light loads, as leaving the engine off for extended periods of time and moving under electric power is key to reducing fuel consumption in stop and go traffic.''
As complicated as the technology is, ''It all happens without the driver realizing it," says Larry Nitz, executive director of GM's hybrid program. ''AHS2 simply optimizes power and torque for the given driving conditions, and all the driver feels is the satisfaction of low fuel consumption and the exceptional reserve power and performance."
The addition of a second mode to the drive system improves efficiency and reduces the need for the ''exceedingly large electric motors'' that are typical of today's single-mode systems, says Nitz.
''Typical single-mode systems depend on large electric power loops between two large electric motors, resulting in inefficiency and ultimately less continuous power,'' says Nitz. ''AHS2 delivers seamless, dependable power on demand and in a more efficient power flow -- and is packaged with motors less than half the size of single-mode systems.''
A sophisticated controller determines when the vehicle should operate in either mode of the two-mode drive system, Nitz explains. The system is meant to be as seamless as it is compact and flexible, he says.
photo:General Motors
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