Brake By Wire

[Treibenschnell]

They've completely done away with the hydraulic system... and do to be in vehicles by the end of the decade!

Mercedes already does a version of this but with hydraulics still intact....



Linkie

[srivendel]

We're sorry. Your brakes are not functioning at this time. Please restart the vehicle to resume regular brake function.



S.

[Majik]

Yeah so what happens when that $3,000 sensor goes out? Will it keep working just long enough so you dont smash into the wall infront of you? Sort of like parts now that last just enough until you are out of the warranty.

[Kestrel]

Yeah, I don't get why "mechanical" (in this case hydraulic) is a bad word these days. Everything "mechanical" simply has to be done away with due to the march of technology... even when/if "mechanical" works perfectly well.

We're sorry. Your brakes are not functioning at this time. Please restart the vehicle to resume regular brake function.

Good one srivendel

[Miatamoto]

I agree that there is entirely too much electronics in cars these days, but this brake by wire can probably have some redeeming qualities. As far as traction control goes, the brake pressure will be more easily and precisely applied to each wheel.

The drag racers will probably like this, they'll just have to wire up a switch to lock up the front brakes to do their tire warm up.

[rx7gslse]

that whole article reads like a sales pitch...

The module consists of the brake pad, the wedge attached to the wedge-bearing mechanism, the mechanical power transmission between the two electric motors and a sensor system for monitoring movement and force. The sensors measure current wheel speed approximately one hundred times per second and braking forces and wedge position to a high degree of accuracy and resolution.

how teh heck is that 'reduced'

it reduces assembly times on the production line and the number of components required for the brake. The electronic brake system also can be adapted more easily and faster to new types of vehicle helping to save time and development costs.

no mention of actual system costs...



And I just LOVE this one...

In the future, electronics will replace other mechanical and hydraulic systems, thereby reducing costs, enabling new functions and increasing reliability.

Nothing like a good blanket generalization to finish off an article. It's OBVIOUS to me that complicated electronic systems are ALWAYS cheaper than those pesky, simple mechanical ones we've had around for 75yrs...

[MadMerv]

The drag racers will probably like this, they'll just have to wire up a switch to lock up the front brakes to do their tire warm up.

They do it now. It's called a Line-Lock. Come to think of it, I had one on my drag car way back in 1972............ :)

[altiain]

Besides the mentioned engineering hurdles, Mercedes will also have to overcome some legislative hurdles, in this country at least. The United States mandates that braking systems must have at least a hydraulic, mechanically actuated backup system, in event of electrical failure.

I've heard a lot of complaints about Mercedes' current electro-hydraulic braking systems being too "grabby" or hard to modulate, and those are only an electric (instead of vacuum-actuated) assist to an existing hydraulic system. I think one of the primary problems with completely servo-operated systems (like brake-by-wire), is developing the proper force-feedback routines so that the driver can actually feel a relatively accurate simulation of what is going on at the wheels, or in this case at the brakes. I took a couple of courses on electronic control system design in college, and they made my head spin - I'd rather design a hydraulic or mechanical system any day of the week.

Although in theory an electric braking system should be simple and more robust (hydraulics take up a lot of weight, require constant fluid maintenance and servicing, and are prone to damage or contamination), I'd be concerned about the power requirements - and more importantly, the backup power requirements in case of an alternator or main electrical system failure - in this instance. When electrically-assisted power steering fails, you still have a good, old-fashioned mechanical linkage that connects you to the wheels. With brake-by-wire, you've got nothing physically connecting the pedal to the calipers, and a panic stop is going to require a lot more juice than, say, the backup battery for airbag deployment.

[Miatamoto]

They do it now. It's called a Line-Lock. Come to think of it, I had one on my drag car way back in 1972............ :)

But it's easier to splice a couple of wires than install a line-lock.

[altiain]

no mention of actual system costs...

Nothing like a good blanket generalization to finish off an article. It's OBVIOUS to me that complicated electronic systems are ALWAYS cheaper than those pesky, simple mechanical ones we've had around for 75yrs...

For a guy who works with fiber optics and electronic packaging for a living, you're even more suspicious of electrons than I am.

I would imagine that the actual systems costs for a true brake-by-wire system would be similar to, or even less than the cost of conventional hydraulic brakes. The hydraulic boosters, lines, and fittings, etc. aren't cheap and present some packaging concerns that don't exist with electrics (I can route a wire almost anywhere - a hydraulic hard line requires a bit more design work, more supplier lead time, and is more expensive to produce, for example). The biggest cost in the system from my limited understanding will likely be in servos and in software development.

[rx7gslse]

For a guy who works with fiber optics and electronic packaging for a living, you're even more suspicious of electrons than I am.

Ah yes... but I'm still a MECHANICAL engineer...

I never have trusted those mischievous electrons....