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Re: New brakes from Siemens VDO
Thanks so much for posting this, Dan 
According to the write-up here (click me) , the brake "style" characteristics are all software controlled by the master eBrake ECU.
The site referenced above has cool SAE conference papers to download, along with a very slow to load 27,8 megabyte movie. The movie is a good, quick way to understand what is going on in a mechanical sense.
I was initially curious about how the brake would work in the reverse direction with a wedge inserted from only one side. I found out from watching the movie that there are two wedge profiles used, one for forward and another for reverse rotation of the brake rotor. The wedge profiles are formed into the face of two opposing plates and made to operate by sliding the plates across some captivated roller bearings. It is VERY clever as a mechanical device.
I'm excited about this development. It has solved the problem of requiring lots of electrical power to "push" on the brake pads. This design only requires power to "jam" or "un-jam" the pads against the rotor. During the mid-stop phase, there is no power required to maintain pad pressure because of the way the rotor motion attracts the pad to keep pressing without further help. Way cool.
Download the SAE papers in .PDF form to see the theory and practice behind this invention.
Quote:
Grant said:
I wonder if they'll have good pedal feel and feedback?
According to the write-up here (click me) , the brake "style" characteristics are all software controlled by the master eBrake ECU.
The site referenced above has cool SAE conference papers to download, along with a very slow to load 27,8 megabyte movie. The movie is a good, quick way to understand what is going on in a mechanical sense.
I was initially curious about how the brake would work in the reverse direction with a wedge inserted from only one side. I found out from watching the movie that there are two wedge profiles used, one for forward and another for reverse rotation of the brake rotor. The wedge profiles are formed into the face of two opposing plates and made to operate by sliding the plates across some captivated roller bearings. It is VERY clever as a mechanical device.
I'm excited about this development. It has solved the problem of requiring lots of electrical power to "push" on the brake pads. This design only requires power to "jam" or "un-jam" the pads against the rotor. During the mid-stop phase, there is no power required to maintain pad pressure because of the way the rotor motion attracts the pad to keep pressing without further help. Way cool.
Download the SAE papers in .PDF form to see the theory and practice behind this invention.
Re: New brakes from Sieman
What if the motor fails, battery dies, or alternator dies. Hydro fluid doesn't need outside source to work. While there is power assist, your brakes are there if the car dies. Just another electronic part to fail. I would think hdro would be more reliable even though it doesn't work as well from performance perspective.
Re: New brakes from Sieman
Quote:
95jersey said:
What if the motor fails, battery dies, or alternator dies. Hydro fluid doesn't need outside source to work. While there is power assist, your brakes are there if the car dies. Just another electronic part to fail. I would think hdro would be more reliable even though it doesn't work as well from performance perspective.
Good point, but the system comes with backup battery and such. I think the reliability issue can be addressed adequately and maybe even be an improvement over the existing hydraulic system.
Thanks for the links Mike. You're right, this is a very cool system. I downloaded the video and watched it and looked briefly at one of the white papers. I think I have the forward and reverse concepts, but how does it work for a stationary vehicle. Seems like that would overtax the motors/battery? I'm sure the answer's in there, I just haven't read far enough.
Re: New brakes from Sieman
Here's another question...how much does all this weight? Electric motors can be heavy compared to lightweight fluid based aluminum calipers, and how will they fit those huge motors under a normal 17 or 18" wheel?
Not being negative, just trying to understand how this will work on a real car.
Not being negative, just trying to understand how this will work on a real car.
Re: New brakes from Sieman
Quote:
95jersey said:
Here's another question...how much does all this weight? Electric motors can be heavy compared to lightweight fluid based aluminum calipers, and how will they fit those huge motors under a normal 17 or 18" wheel?
Not being negative, just trying to understand how this will work on a real car.
Don't know how much, but the article says they weigh significantly less than current technology. I just bought new rotors (stock) for my 993 and I can barely lift the box with all 4 - like an anvil...
Re: New brakes from Siemens VDO
Quote:
95jersey said:
What if the motor fails, battery dies, or alternator dies. Hydro fluid doesn't need outside source to work. While there is power assist, your brakes are there if the car dies. Just another electronic part to fail. I would think hydro would be more reliable even though it doesn't work as well from performance perspective.
The Siemens-VDO system includes an isolated back-up battery in case alternate power is required.
The chance of all four electronic brake calipers failing at the same time is much less than a master cylinder rubber seal failing. Ever drive an old British car? Those things we now refer to as parking brakes used to be called Emergency Brakes. Wonder why?
What happens if a hydraulic line fails in a conventional system?
Are old systems with numerous "traditional" failure modes to be preferred to less complicated modern systems that lack a documented "failure trail"?
When I first heard of gas pedals connected to electronic position sensors, I was aghast. But, then, I was young and stupid. The image that came to mind was of volume control potentiometers in cheap TV sets that got all scratchy and some times intermittent with disappointing regularity.
But, TV volume adjusters don't have product-liability lawyers chasing around them, and their main design requirement is asymptotically low cost. Automotive drive-train controls are engineered and designed to a much higher standard of reliability, which includes redundancy. Those electronic position sensors on throttle-by-wire systems are dual, matching sensor units. In an instance where their sensor reports don't agree with each other, an electronic referee throws a flag and the system shuts down into limp mode. No harm, no foul.
These stop-by-wire wedge brakes have two (redundant) actuator motors. Electronic sensors can determine if they are both working. If one electric motor happens to fail, the second is still available to actuate the brakes. One still has all 6 electric motors from the other three calipers in fine working condition. Immediately upon sensing the first motor's failure, the system can curtail the vehicles ability to travel in an endangered state by interacting with the engine control systems.
Computer control of mechanical systems is here to stay. It allows many more safety back-up systems without additional cost or prohibitive weight. The design of the systems is very modern and always advancing in capability and reliability. The market won't tolerate a decrease in reliability or lack of function, and every vehicle component designer knows it all too well.
Not to worry
Re: New brakes from Siemens VDO
Quote:
GM Austin said:I think I have the forward and reverse concepts, but how does it work for a stationary vehicle. Seems like that would overtax the motors/battery? I'm sure the answer's in there, I just haven't read far enough.
As I read the papers, I surmise that the only power required for parking is to drive the wedge into compressing the pad against the disk.
The actuator motors drive a helical shaft (Rollerscrew in Fig. 2 above)) that moves the wedge plates back and forth. The wedge can't drive the screw backwards, so the pad pressure is maintained without any further actuator input.
It works just like the ratchet on a conventional parking brake handle
Re: New brakes from Siemens VDO
I am waiting for download to complete at this moment. What I do pick up is there will no longer be a need for master cylinder, brake lines, Hydraulic fluid, less electic needed so maybe smaller alternator, no separate emergency brake so all this adds up to something that weights consideralby less. As Mike pointed out 4 separate wheels with controlers means no more abs system as the software will control. Sounds like I won't be needing $9000 Carbon Fiber brakes anymore. Whew!!
Re: New brakes from Siemens VDO
Quote:
W8MM said:Quote:
GM Austin said:I think I have the forward and reverse concepts, but how does it work for a stationary vehicle. Seems like that would overtax the motors/battery? I'm sure the answer's in there, I just haven't read far enough.
As I read the papers, I surmise that the only power required for parking is to drive the wedge into compressing the pad against the disk.
The actuator motors drive a helical shaft (Rollerscrew in Fig. 2 above)) that moves the wedge plates back and forth. The wedge can't drive the screw backwards, so the pad pressure is maintained without any further actuator input.
It works just like the ratchet on a conventional parking brake handle
Hmmm ... I see what you're saying, but I see elsewhere that the friction of the pad against the disk actually increases the braking force as it pulls the rollers up the inclined plane/wedge. And it works either direction as the friction pulls the rollers up one side or the other of the wedge.
as I said before, I need to read further ...
Re: New brakes from Siemens VDO
Do any of you recall the worry that MBZ's US liabilty people had before they brought ABS to the US mkt here in 1985 model year ( and years before enough other cars would have it ) ? They worried about the potential for rear end collisions due to stopping on wet roads so much faster ! I wonder what happens now , if you can stop 30-50 % faster when the lumbering 6000 lb SUV right on your tail needs 2-3x the distance to come to a halt ? I guess your car and it's contents becomes the " wedge " that helps the Suburban stop 30-50% sooner also
Re: New brakes from Sieman
Quote:
95jersey said:
What if the motor fails, battery dies, or alternator dies. Hydro fluid doesn't need outside source to work.
For liabilty reasons, of course , manufacturers would be have to incorporate a release cord to manually open the floorboards so that you can brake in this fashion . (Stopping distance then depends on number of passengers and type of shoes worn) :
Re: New brakes from Siemens VDO
Quote:
MKW said:
Do any of you recall the worry that MBZ's US liabilty people had before they brought ABS to the US mkt here in 1985 model year ( and years before enough other cars would have it ) ? They worried about the potential for rear end collisions due to stopping on wet roads so much faster ! I wonder what happens now , if you can stop 30-50 % faster when the lumbering 6000 lb SUV right on your tail needs 2-3x the distance to come to a halt ? I guess your car and it's contents becomes the " wedge " that helps the Suburban stop 30-50% sooner also
Amazing brakes are great for when one has no one following/in mtn twisties, but in normal traffic, I always leave immense following dist and am very aware of what's following me and how inept a driver they seem....gotta use common sense defensive driving....drive safest perf cars one can afford to reduce injury risk to self....
Have never been in any accid, but fully expect, no matter fault, that a personal injury lawyer will try to shake down the most affluent driver involved to get a nuisance-go-away settlement from those w/more money than time for petty litigation....rules of the US class warfare game that most affluent guys prepare for anyway in any interactions w/the general public....
Nov 13, 2006 8:39:50 PM
- trip
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- Loc: Bay Area California , United States
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Nov 13, 2006 11:38:35 PM
- Jim_in_Iowa
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Re: New brakes from Siemans
This is interesting technically, but it seems to me a solution in search of a problem. The drive-by-wire + teleoperation crowd will love it, but I don't see much appeal in it.
The main problem with current brakes is the monkey not paying enough attention and putting foot on pedal soon enough (or treating it like a binary switch when surprised). The other limitation in braking is tires.
Jim
The main problem with current brakes is the monkey not paying enough attention and putting foot on pedal soon enough (or treating it like a binary switch when surprised). The other limitation in braking is tires.
Jim
Re: New brakes from Siemens VDO
Quote:
trip said:
I always thought that the limit on current stopping distances was not the braking power, but the grip the tires could maintain when stopping.
Yes, if your brakes are strong enough to trigger ABS, then the tires are the limiting factor. If not, it's the brakes. Maybe conventional brakes take slightly longer to start working at high speed when you first apply them...
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