eBraking cuts stopping distance 50%
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Could technology from an 18th century horse & buggy become the latest high-performance braking innovation? Back then, they used a wedge of wood to bring the wheel to a stop. Since then, we have been through several innovations in braking, with the latest being with multi-piston calipers, squeezing ceramic-carbon rotors with a multitude of brake pad formulations. According to Siemens, the future of braking technology is called EWB or Electronic Wedge Braking. Along with a claim that they have regularly experienced braking distances that are less than half of what's required by standard brakes, they also claim to utilize less than 10% of the energy needed by hydraulic brakes and weight substantially less than their conventional counterparts. What's more, the EWB will eliminate the need for brake lines, a servo-unit and a brake fluid reservoir, as it is entirely driven by 12-volts of electricity.
Here are a couple of other really cool features of the system. The faster the vehicle is traveling when the brakes are applied, the more powerful the brakes immediately become. The rotor momentum draws the pad further up the series of interlocking wedges applying progressively more pressure and increasing efficiency. Each wheel can also be electronically modulated to allow for much more precise anti-lock and stability processes as well as eliminating the pulsating pedal associated with the current ABS systems.
When will the EWB system hit the road? Possibly as early as 2008 on a Porsche, BMW, Audi or Mercedes-Benz.
[Source: AutoWeek]
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Reader Comments (Page 1 of 2)
Paul 11:22AM (11/10/2006)
I am anti-drive by wire in general but I can deal with it. I am HUGELY anti-brake by wire - unless the system automatically engages in case of a power failure I am worried.
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Ben Towner 11:16AM (11/10/2006)
While electronic brakes are good there is no substitute for hydraulic brakes. In the event of a total electrical system failure (Not that UNcommon these days) the brakes will not work. IMO those are the most important pieces of equipment on any vehicle. I have been without brakes before and the feeling of being out of control and helpless is overwhelming. I think the concept is great but should be applied to hydraulic brakes.
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araemo 11:33AM (11/10/2006)
Are electronic brakes really that much less reliable than hydraulic brakes? In a total hydraulic failure, you're equally without brakes. Not completely in either case, the Emergency-brake(Hint: total hydraulic or electric failure on the road would be considered an 'emergency') is usually cable-actuated by your arm muscles...
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Jeff 11:36AM (11/10/2006)
The mechanical / hydraulic emergency brake wouldn't need to go away just because the main brakes are electronic.
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A54 11:40AM (11/10/2006)
If you look at a hydraulic brake system, it is designed so that if you rupture a brake line, you still have 50% of your brakes. It should be simple to come up an electric system that functions in the same manner.
I know one thing, I look forward to the shortened stopping distances. It'll save me when some cuts me off in traffic(again).
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Stedwoo 11:40AM (11/10/2006)
It has a battery back-up in case the Car battery dies. Here is a video showing how the system works.
http://i.cmpnet.com/automotivedesignline/2006/04/0913b_low.wmv
Stedwoo
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gkz 11:43AM (11/10/2006)
safety issues aside (which i'm sure would be taken care of before production use), this would be a pretty cool thing to have. probably not long til you see them on race cars.
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Steve C 11:44AM (11/10/2006)
As a mechanical engineer I'm curious about brake pad wear with the EWB system. When I read that autos with this system can stop in 50% shorter distances, the increase in braking energy has to be dissipated somewhere, in this case the pads. If reliability issues can be worked out a lot of lives could be saved with this system.
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Phil L. 11:44AM (11/10/2006)
Actually, in my experience, it's probably easier to create a super-reliable electrical braking system than a similarly-reliable hydraulic system. Just because auto manufacturers haven't yet put the same amount of effort into electrical reliability doesn't mean it can't be done.
For example, it's fairly straightforward to create a second, temporary electrical supply that is used as a backup for critical systems (does your PC have a UPS? Then you know what I'm talking about). It'd be far more difficult to have a second, separate hydraulic system to account for possible brake line failure.
Your car probably already has some similar technology in place: Many airbag systems have small built-in power backups, so the airbags will still deploy properly - even if the car battery is destroyed before the full impact of an accident is enough to trigger the airbags. This is also the reason you'll see warnings to disconnect the battery - and then wait a period of time (I've seen specs claim half an hour!) before working on the airbag system.
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ZAMBONO 11:44AM (11/10/2006)
If the energy is applied in reverse it would work in an emergency situation. Example, when you turn on the engine and the alternator is juicing up the car the energy is used to depress the brake. So when there is no electricity the brakes are applied at lets say 25%, that is their resting position. It would be an automatic parking brake as well.
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Phil L. 11:47AM (11/10/2006)
...continuing where I left off....
In any case, the possibility of 50% reduction in braking distance is too great to ignore, simply based on reliability of current hardware. Would you turn down a 50% improvement in power if you had to give up a carburetor and depend on electronic fuel injectors, just because you don't trust them?
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Rob Theriaque 11:53AM (11/10/2006)
I find a 50% reduction in braking distance hard to swallow. On many vehicles, your braking potential isn't limited by the brakes, rather the friction of the tires and the road. It's the same reason that using 14 pistons on a caliper is silly- locking up your rotors (therefore your tires) isn't going to slow you down any quicker. Modulating that will help, but in the end you're limited by tires more often than your brakes.
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Coachzed 11:59AM (11/10/2006)
Putting the issue of whether or not we should trust a totally electronic braking system aside, this technology really doesn't have that much to offer street cars.
The brakes on nearly every car on the street (excepting maybe some monstrosities like the Laforza or Humvee) are powerful enough to lock the tires or trigger ABS in a panic stop. The weak point of car braking is the tires, not the brakes themselves.
This technology could be put to great use in racecars, but heat dissipation then becomes a major issue. It would be interesting to see what happens when those electronics become glowing hot.
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Chance 12:08PM (11/10/2006)
So this will avoid accidents or cause them - following distances and reaction time?
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neox 12:13PM (11/10/2006)
Did anyone (#1-#12, ecxept #6) see the video?
if so enough of the power falure and
I think the system is as tuneable as an ECU
on how much power you want the brakes to have or which ones you want to have the most power front or back brakes...
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ME 12:16PM (11/10/2006)
"I find a 50% reduction in braking distance hard to swallow. On many vehicles, your braking potential isn't limited by the brakes, rather the friction of the tires and the road."
Exactly. I would say most if not all passenger vehicles ultimate stopping distance is limited by tire grip. I really hope Siemens provides some explination for their claim.
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Stedwoo 12:17PM (11/10/2006)
Some are missing the point in how this system improves Braking distance. A Hydrolic ABS takes 140 to 170 milliseconds to generate full braking force. The EWB system can accomplish it in less than 100 milliseconds.
http://www.physorg.com/news6781.html
The actual pads and rotor system, other than being wedged shaped, is not that much different than existing fluid based systems. The primary change is the use of actuated motors to drive the wedge shaped pads therby eliminating the fluid portion of the system.
In addition it assist with stability control and will not pulse like existing ABS systems do today; this should help with the average drive so they will not freak when the pedal pulses. Since the pedal is decoupled it provides safety in a crash reducing foot injuries.
http://www.automotivedesignline.com/howto/showArticle.jhtml?articleID=184429176
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A54 12:17PM (11/10/2006)
Given the limitation of the tires, are hydraulic brakes, even modulated ones, taking full advantage of the capabilities of tires?
How long does it take for a hydraulic system to transmit stopping force to the rotor? When modulated, what is the lag time?
Could the improvements be due to the simple fact that the electronic wedge brakes are much better at applying a modulated, maximum braking force to the wheels without locking the tires?
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Miguel 12:29PM (11/10/2006)
"they have regularly experienced braking distances that are less than half of what's required by standard brakes"
REQUIRED is the key word here. Braking requirements are pretty lenient, and chances are that your current car exceeds these requirements (shorter stopping distance than required). From this, we can say that this system improves stopping distance by less than 50%.
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MrClever 12:52PM (11/10/2006)
3. Are electronic brakes really that much less reliable than hydraulic brakes? In a total hydraulic failure, you're equally without brakes. Not completely in either case, the Emergency-brake(Hint: total hydraulic or electric failure on the road would be considered an 'emergency') is usually cable-actuated by your arm muscles.
DITTO.
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