The 42-volt integrated starter generator (ISG) is built into the flywheel between the engine and transmission and is the power behind the Saab BioPower's fuel-saving, stop/start functionality. It serves a multi-functional role as a starter motor, alternator and 15 kW engine power booster, while also helping to iron out residual crankshaft vibrations.
Jonsson says that auxiliary functions, such as the water pump, air conditioning and power steering systems, are now removed from the engine's belt drive and electrically-powered instead, through the hybrid system.
A parallel hybrid system uses a control strategy is based on efficient "energy management" -- recovering, storing and feeding back energy that is otherwise lost in a vehicle powered only by an ICE. Apart from converters to manage AC/DC and 12, 42 and 300-volt interfaces, the system consists of just three core components: two electric motors and a battery bank.
Electric energy storage is provided by a 42-cell, 300-volt lithium-ion battery bank, designed to be entirely maintenance-free throughout the lifetime of the vehicle.
The battery supplies a compact 38 kW electric motor located between the rear wheels which powers a transmission differential and drive shafts. At low speeds, this Rear Drive Unit is able to briefly generate about 500 lb-ft of additional torque.
In reverse operation, the motor acts as a generator to provide "regenerative braking" by recovering kinetic energy otherwise lost during braking and converts this into additional battery charging. It also performs the same function whenever the driver lifts off the throttle, harnessing the energy in the rotating drive shafts.
The second electric motor is the integrated starter generator (ISG) located within the flywheel between the engine and main transmission. On demand, it contributes 15 kW of additional power about 90 lb-ft of extra torque to the output of the engine through the front wheels.
At take off, the Saab BioPower "also exploits the instant torque generation of its electric motors," notes Jonsson, "smoothly adding strong, accelerative power during the engine's pick-up, from tick-over to about 1,500 rpm. It is during this phase that the available pulling power, or torque, is more than tripled."
An estimated fuel saving of five-to-seven percent is provided by the automatic engine stop/start function. Whenever the vehicle is stationary, the engine is shut off to save fuel. As soon as the brake is released, it is automatically started again by the ISG. "The operation is carried out seamlessly," promises Jonsson, "and requires no input from the driver."
In congested driving conditions, he notes, "fuel saving is taken a step further by the Saab BioPower's 'Zero Mode' operation -- giving zero fuel consumption, and, of course, zero emissions -- which can be selected by the driver via a button in the central console."
At speeds below 50 km/h, 'Zero Mode' will shut off the engine and again switch the car over to electric power only through the RDU. Jonsson says that, "In this mode, the battery bank provides a range of between 10 and 20 km. The engine is smoothly re-engaged whenever the battery status approaches a low charge level or the electronic throttle opening requires acceleration beyond the 50 km/h operating limit."
photo:Saab Cars
Jonsson says that auxiliary functions, such as the water pump, air conditioning and power steering systems, are now removed from the engine's belt drive and electrically-powered instead, through the hybrid system.
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| (Photo: General Motors) |
Electric energy storage is provided by a 42-cell, 300-volt lithium-ion battery bank, designed to be entirely maintenance-free throughout the lifetime of the vehicle.
The battery supplies a compact 38 kW electric motor located between the rear wheels which powers a transmission differential and drive shafts. At low speeds, this Rear Drive Unit is able to briefly generate about 500 lb-ft of additional torque.
In reverse operation, the motor acts as a generator to provide "regenerative braking" by recovering kinetic energy otherwise lost during braking and converts this into additional battery charging. It also performs the same function whenever the driver lifts off the throttle, harnessing the energy in the rotating drive shafts.
The second electric motor is the integrated starter generator (ISG) located within the flywheel between the engine and main transmission. On demand, it contributes 15 kW of additional power about 90 lb-ft of extra torque to the output of the engine through the front wheels.
At take off, the Saab BioPower "also exploits the instant torque generation of its electric motors," notes Jonsson, "smoothly adding strong, accelerative power during the engine's pick-up, from tick-over to about 1,500 rpm. It is during this phase that the available pulling power, or torque, is more than tripled."
An estimated fuel saving of five-to-seven percent is provided by the automatic engine stop/start function. Whenever the vehicle is stationary, the engine is shut off to save fuel. As soon as the brake is released, it is automatically started again by the ISG. "The operation is carried out seamlessly," promises Jonsson, "and requires no input from the driver."
In congested driving conditions, he notes, "fuel saving is taken a step further by the Saab BioPower's 'Zero Mode' operation -- giving zero fuel consumption, and, of course, zero emissions -- which can be selected by the driver via a button in the central console."
At speeds below 50 km/h, 'Zero Mode' will shut off the engine and again switch the car over to electric power only through the RDU. Jonsson says that, "In this mode, the battery bank provides a range of between 10 and 20 km. The engine is smoothly re-engaged whenever the battery status approaches a low charge level or the electronic throttle opening requires acceleration beyond the 50 km/h operating limit."
photo:Saab Cars
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