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Siemens VDO’s Electronic Wedge Brake Achieves an Average 15% Reduction in Braking Distance During Winter Testing; Key eCorner Component

Sv_pp_ewb_principles_020407_lowres
EWB. The brake calipers (1) span the brake disk (2) from two sides. The brake disk is braked by a pad (3) which is moved by an electric motor (4) by several rollers (5) along wedge-shaped inclined faces. Click to enlarge.

Siemens VDO’s Electronic Wedge Brake (EWB) (earlier post) has shown an average 15% reduction of braking distances on ice and snow compared to vehicles equipped with conventional hydraulic brakes. The automotive supplier achieved these results during intensive testing near the Arctic Circle in Arjeplog, Sweden.

The EWB, which will go into series production in 2010, is an important milestone in Siemens VDO’s development of eCorner: a system that integrates the motor, steering, shock absorbers and brakes directly into the wheels of future cars. (Earlier post.)

Prior to the winter testing, Siemens VDO had only obtained evidence of such improved braking behavior in simulation models. In the winter testing, it took mid-range vehicles with conventional hydraulic brakes, modern ABS and winter tires on average 75 meters on ice to come to a complete stop from a speed of 80 kph (50 mph). On the same test, Siemens VDO’s latest Electronic Wedge Brake (EWB) prototype reached a standstill in 64.5 meters. By the time a EWB-equipped car comes to a complete stop, the hydraulic brake-equipped-car is still traveling at 30 kph (19 mph).

Ecorner
eCorner. The wheel rim (1) remains the same. Beneath is the wheel hub motor (2). Braking is via electronic wedge brake (3). The active suspension (4), like the electronic steering (5), replaces the conventional hydraulic system. Click to enlarge.

In the EWB system, during braking an electric motor presses a wedge connected to a brake pad located between the brake caliper and the brake disk. The rotation of the wheel and the resulting friction automatically reinforces the wedge effect. This results in a very high braking force to be produced with very little effort.

With the successful completion of winter testing, Siemens VDO now is reviewing its gathered experiences to further develop and refine EWB hardware and software. In the future, the wedge bearing mechanism will be driven by a single, highly responsive electric motor. This will allow a size reduction of the by-wire brake module by the time it is ready to go into series production in 2010.

Comments

Brad

Ya know, some of these articles that have been coming out lately seem to have absolutely nothing to do with the environment.

Brett

This directly pertains to vehicle efficiency. Next time you are sitting at a stop light, with your foot on the brake to keep the car immobile (for both manuals and automatics), put on the parking brake and release the foot brake and watch your engine idle speed. It should increase due to the vacuum load from the power brake you have removed from the running engine. If you remove the need for this vacuum, power assist brakes for hybrid electrics are possible.

Fred

It also has an application in anti-spin, to brake the spinning wheel and transfer torque to the non-spinning wheel. This approach leads to less 4 wheel drive vehicles, so less mass, less friction.

It works for the environment if it's a lighter weight higher efficient design. (that assumes that it actually works)

Lucas


Brad - If you are unable to relate this to Green Car Congress, maybe you need to re-examine your thinking.

Neil

Brad: Don't sweat what Lucas says. Brett and Fred already answered your question well. Lucas has a very high opinion of himself.

Lucas


That's true. AND ... It's well deserved.

allen_xl_Z

This system also allows electric cars (and PHEV) to replace hydraulic brakes with electrics. Couple electric brakes with electrically powered steering assist and auxilaries, and the efficiency increases, and complexity falls (albeit slight).

koen

The PLM Flightlink electric car (which has 4 in-wheel motors), breaks only by means of regenerative breaking and can do without friction break. If this can be done savely, then why use a friction break in an electric car?

Ash

I like the electric brake concept, this would make traction and stability control much easier (and perhaps cheaper?) to impliment.

However the suspension integration is a very poor idea, it would have horrible grip characteristics on anything but flat level roads.

--Ash

Ruaraidh

The PML concept is illegal for road use. The VDO system will not be as it uses mechanical friction (albeit electrically controlled) to do the braking. That is a very different case than that of pure regenerative braking. In addition to that, if you use pure regenerative braking of sufficient power, you end up with motors that are greatly oversized as most braking performance of even small, cheap cars has a 60-0 of around 3s. With electrical braking, the corollary of that is very high performance and oversized motors. Do you really need an electric car that'll do 0-60 in 3s? No, you need friction brakes for peak use and sensibly sized motors for all other times.

clett

A razertech motor the same size as Prius MG1 can give out 500 hp (one at each corner would be fun!). I guess the current acceptance rate of the battery or capacitor would be the limiting factor for a regen only braking system.

Van

I would suppose the wheel adhesion limits the size of the regenerative braking collection system. And I would think it could be modulated at a pace an order of magnatude above that of a hydraulic system, being digitally controlled. First generation regenerative brakes achieved a 7% improvement in fuel economy by recovering braking energy, so something in the range of 10% improvement may be provided by a mature design.

Stan Peterson

Automotive advances in effiecinecy are what thsi blog is all about.

Sorry if you don't appreciate that.

Regenerative braking can't be sized big enough to recover all the energy without substanially oversized motor genrators and batteries/capacitors. The rate at which the energy can be stored in either a battery or capacitor is limited as the state of charge goes up.

So with a "full" battery/capacitor you theoretically would have no brakes. I would guess this would be the electrical equivalent of "brake fade".

DavidInAL

Wouldn't you then just include a big toaster heating element into the system to soak up excess electrical energy from braking? That's how locomotives do their dynamic braking.

andrichrose

just imagine trying to service this system after 5 years on the road with all the salt and grime , you would just end up throwing it all away and replacing with new parts,
which would probably cost an arm and a leg , but maybe thats the point!

Norris

Once again, the "self-energizing" brake is being reinvented. The engineering desire to convert the rotational force of a brake systems drum, disc or rotor to actuate the brake has been around since the 1930's, when hydraulic brakes became popular. General Motors has used a similar form of self-servo system in the cheap hydraulic drum brakes it used on the rear axles of such cars as the Malibu, Buick, Camaro, Firebird, in the '70's, '80's and '90's. Does the Siemens system work if the battery goes dead? Will it need two batteries for safety? Will it still need the old reliable mechanical parking brake? No, yes and yes. Nothing new here, move along.

John

I imagine the VDO system would or could be spring loaded to return to a "brakes engaged" mode in the event of power or signal failure. If that doesn't suffice, then tie it into a handbrake lever system for emergencies, similar to a vehicle parking brake system. Then when the diagnostics detects a brake issue or you have a total power failure, pull the lever.

Jeevan

Good.Is it applicable for indian roads. how about the cost compared to the hydraulic brake system. also explain the criticality in the assembly of this unit.

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