Given all of the luxury cars that are coming out with it I would find it very hard to believe that the Model S will not have it. Especially in 2 years when it will be practically standard on all cars.
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... and it looks like the Fisker and the Model S won't have it either. ...
Any ideas on why some cars do this and others do not ?
Products operations liability. Imagine a system failure causes a full stop at >60 mph on the highway. Imagine the fun you'll have. That's why Volvo only does a full stop at <20 something mph.
Personally, I couldn't care less about that option. Either I can drive a car and I'm fully attentive, or I shouldn't drive a car at all. No offense intended.
So all you are saying is that some manufacturers are will to take the risk of a law suit and others are not ? Seems kinda lame to me .... you may be right of course but that is a lame excuse.
What I don't understand about Volvo's system is that at Highway speeds it will take you down to about 20 mph before it turns off - same as my BMW - but Volvo also has a system that stops the car if you are traveling less than 20 mph. But the two do not work together !!! uuuuugh seems to me at 20 mph you should switch from one system to the other. If for some unknown reason the car needs to stop itself then it should be able to finish the job. Why slow the car to 20 mph and then have an accident when the car (and the accident) could have been avoided all together ?
I hope that I NEVER need the system but I am glad that I have it none the less !
At the <20 mph the time to stop is shorter or near your reaction time. So it makes kind of sense to let the system do a complete stop. Also, a failure wouldn't be so disastrous at that low speed. AFAIK Volvo is the only one with such a system. But I didn't pay much attention recently. Could be others have it too.
At highway speeds, they assume you will pay attention immediately if the car beeps, light on the dash go on and braking occurs. And then you'll be able to decide yourself if you need to floor the brake pedal. Anything other will incapacitate the driver and could be a sword against them for lurking lawyers esp. in the US, if the driver relies on it and / or it fails. I'm pretty much sure that was their reasoning when Daimler and BMW introduced their systems years back. It's not that is not technically possible. Drive be wire is pretty much possible to day as seen on many prototypes. But products operations liability holds them back (and costs of course).
You seem to be missing my point really.
...highway speed reduction to 20 mph at that point you are only going 20 mph so why not allow the other system designed for less than 20 mph kick in
Seems so.
Because it is another system? "Switching systems" on such a crucial thing as brakes would be a nightmake if I where in charge as engineer. How to ensure a full, complete and successful handover? And even if it could be done, I still fail to see why it should. In what case would a system brake the car driving 60mph at 40% rate to 20 mph and then do a full stop WITHOUT driver intervention? The Volvo system is an emergy stop system trying to eliminate your reaction time. At 20 mph your reaction time happends to be same or larger than your stopping time. At 60 mph it's not so they leave to driver to decide but still cut off of your reaction time quite a bit. It's just that simple. Sorry if I still do miss your point.
Several cars will come to a complete stop. The 2010 models of Audi, BMW, Mercedes, and Infiniti are examples. The 2010 Hyundai Genesis will work down to 6mph. It has nothing to do with dual-systems working together or potential lawsuits.
These adaptive cruise control systems work by using radar to measure the distance to the car in front of you. If there is no car there then guess what -- there is still radar energy being reflected back from surface irregularities on the empty road. How does it tell the difference? By taking a distance measurement, waiting a moment, then taking another distance measurement. It knows how far your car has travelled between those two readings, so if the "object" has grown closer by that same amount then it must be a stationary object (such as the road). Stationary objects are ignored. If the object appears to be moving then it will treat it as a car. As your own vehicle speed drops below about 20mph this calculation becomes much harder to do because your car isn't travelling far enough between samples to render an accurate calculation about the target object being in motion or not.
These ACC systems (even the fancy new ones) will let you plow right into a brick wall or parked car without ever even slowing down. The object has to be "moving" in order to be considered a car. On the fancy new systems, once your car "locks onto" a moving object, then if that moving object slows down to a complete stop then your car can maintain the "radar lock" on that object and also slow down to a complete stop. The fancy new systems just use more accurate radar sensors and faster CPUs and higher precision math libraries in order to work at the slower vehicle speeds.
The radar units are the best. The laser based systems (such as Infiniti and Lexus) don't work when driving directly into sunlight or when it is raining/snowing/heavy fog.
The radar units are the best. The laser based systems (such as Infiniti and Lexus) don't work when driving directly into sunlight or when it is raining/snowing/heavy fog.