As has been stated by at least two others, this is a supremely logical idea. The only potential fly in the ointment is whether the Prius' (or this Lexus') electric motor goes through the transmission or is more directly coupled to the drive axle. Some purely electric cars have the drive motors mounted on each wheel. This seems awkward (at best) for a hybrid. Does anyone know how these hybrid drivetrains work?
This may be taking the thread a bit off topic, but the way the Toyota hybrid transmission the two motors are integral to the transmission -- I've linked to a Java applet that shows a demo of how the transmission works if you're interested:
http://www.wind.sannet.ne.jp/m_matsu/prius/ThsSimu/index_i18n.html
Basically, instead of "shifting gears", the engine and two motors are all connected to the wheels at the same time using a planetary gearset. The transmission works by using one of the two electric motors as a generator, then using that electrical power to simultaneously drive the other motor. Power can be stored or withdrawn from the batteries, but it is not necessary for the vehicle to operate. Since the motors all are connected at different gear ratios, this has the effect of 'changing gears'.
An active role by at least one of the motors is required, from what I understand, for any power from the engine to be transferred to the wheels. In "neutral" both electrical motors would simply freewheel from what I understand.
The fact that the vehicle acts as a hybrid does require a lot of redundant systems. Power steering and braking on most cars is dependent on the engine being ON at all times. In the Prius and other hybrid cars the engine can actually be OFF for extended periods of time, it is necessary to have both electric power steerinng, and an auxiliary electric vacuum pump to maintain intake manifold vacuum for power braking. Some (but not all) hybrids also have a second starter motor, in addition to the traction motor.
Back on topic, can't you guys wait until Drive by wire steering and brakes come out:duck:?
What do mean when? 2 of our 3 vehicles have that right now. Wife's accord has EBD braking. It will brake one of more wheels to help in a normal turn, even when brakes are not applied by the driver at all. This appears to be the culprit that's making all the 07(?)+ accords go through a set of rear brake pads at 15-20k miles.
My s2000 has electric power steering. While not drive by wire (yet) I can tell you it's a lot different than normal power steering.
From what I understand nearly all the current braking and steerinng systems are power
assisted, and that those assist systems are often governed by wire -- such as cars with features that determine that a driver is too "stupid" to stop in time to avoid a collision, thus applying stronger brake pressure to prevent a crash.
However, all still have a direct mechanical link, at least on some level. Braking without brake assist is for example much much more diifficult, but still possible (in theory) in the event of say an engine stall causing brake assist vacuum to dry up. Also, most cars still can be steered but with much greater effort if power steering cuts out because a mechanical link exists between the steering column and the actual steering on the vehicle. Just as there is a physical cable still connecting the brake pedal to the brake cylinder. It's just that most cars have auxiliary systems to "help" in those cases.
In the case of throttle, the throttle pedal is strictly an electronic input. I am okay with that in the case of acceleration, I would not feel comfortable driving a car in which the sterring wheel and brake pedal were mere electrnic inputs that were mechanically decouppled from the actual steering and braking systems. IMO there should always be some mechanical link between brakes, and steering as a failsafe -- as in the case of a catastrophic failure, it is critical that the driver be able to stop and steer the car, even if those systems are assisted by complex "smart" systems under normal circumstances.