diference between brake assist and VSA?

It looks confused to me between EBD and VSA found on 06 Accord V6.

What is it and the difference? I understand the car's computer can detect
slippage on one of the wheel and reduce the brake force on that tire but how
can a vehicle detect the car is over/under turn at a curve like Honda
website described?

Anyone ever studied/experienced on this device? Like to hear if it is a
real help and selling point for an 06.
I have a 05 EX-V6 and wanted to get another 06 mainly for these "safety"
feature.

Thanks

 

VSA stands for Vehicle Stability Assist. This system uses the existing ABS
components to slow or stop wheels on one side of the vehicle (side to side
operation) to prevent over/understeer situations and to aid in prevention on
vehicle control loss in emergency situations/maneuvers.

 

Thank you for the response.
My next question is --is it duplicate function if brake force distribution
can control the brake, why need VSA again?
What does traction control's role?

Sorry for all these questions, I am puzzled.
I saw ABS first and then TC and the EBD and now the VSA.
IS there any data/test reveals the effeciveness of all these so called
safety features?

 

This is a confusing topic because there is a lot of overlap. The good
news is that you don't have to understand any of it, to benefit from
it.

It comes down to what do you know and what can you do about it. You
can know the speed of each wheel with ABS sensors. You can know how
much throttle is requested and how much throttle is delivered to the
driven wheels. You may even be able to lock the wheels together to
some extent when delivering power. You can know how much braking is
being requested. You can control the braking force exerted on each
wheel independently. You could even have accelerometers that measure
centrifugal force, but I don't know that they actually do this.
(I'll bet the airbag systems have accelerometers.)

ABS (Antilock Braking Systems) is well tested technology at this point.
You want to stop fast, you stamp on the brake pedal hard. This might
cause the brakes to lock up. The ABS sensors can detect this lock up
and release the brakes. For threshold braking you want the brakes just
short of locking up. Cycling the brakes quickly between locking and
just short of locking is a very good approximation to threshold
braking. Remember you can steer a car just with the brakes. If you
brake the right front wheel, the car will pull to the right. If you
brake the left front wheel, the car will pull to the left. If you
steer the car while braking hard, different levels of braking can be
applied to each wheel. It requires a great deal of skill to threshold
brake and steer a car without ABS. With ABS it takes little skill to
threshold brake and steer the car. You just brake really hard and
steer. The ABS does all the hard work. Without ABS you have no way of
independently controlling brakes force right to left, so ABS is has
some actual advantages over non-ABS systems. The most common mistake
in ABS cars is not to steer around the dangerous object while threshold
braking. The second most common mistake is getting off the brakes when
you feel the funny pulsing in the pedal.

TC (Traction Control) has to do with controlling acceleration forces on
the driven wheels. Because of differentials, the right and left wheel
can spin independently. This is necessary in normal cornering as the
inside wheel travels a shorter path than the outer wheel. In some
situations the traction is better on one wheel than the other. Without
traction control, much of the engine power goes to spinning the tire
that has no traction and little power to the wheel that does have
traction. You want the opposite of this. In off-roading this is a
well know problem. Locking hubs are the traditional solution. You
lock the wheels together (bypass the differential that allow the wheels
to spin at different speeds). Some times this is done with
electronically controlled clutches. Braking just the tire with poor
traction looks a lot like traction control. Since the wheels spin
together when they are locked together, power will be delivered to the
wheel with traction. The wheel with poor traction can't spin any
faster than the wheel with good traction. This is a complicated
subject. There are many ways to skin the cat. Off-roaders love to
talk about locking hubs and traction control. Find one.

EBD (Electronic Brake Distribution) controls the ratio of braking force
front to back. This is problem wheel know to sport bike motorcycle
riders. Motorcycles has independent front and rear brake controls for
a good reason. When you decelerate from braking more down force goes
onto the front wheel and less on the rear wheel. This means that the
front wheel is harder to lock up and the rear brake is easier to lock
up. You want more braking force on the front wheel and less on the
rear. In the extreme you can "stoppie" a sport bike where a great
deal of braking force is applied the front wheel and the rear wheel
lifts completely off the ground. Just before this happens the amount
of rear braking force that can be applied without skidding goes to
zero. Note that it is deceleration that causes this weight transfer.
Normal sedans can't stoppie, but they are affected by front/rear
weight transfer. At the very beginning of the braking, the rear wheels
have good down force and braking capability. The harder you decelerate
the more weight transfers to the front and the more braking force you
want on the front wheels. This can all be done short of locking up the
brakes with ABS. Sports car drivers might call this continuous
(front/rear) brake bias control.

VSA (Vehicle Stability Control) works in conjunction with the ABS to
control over steer and under steer. The total side force on a tire is
a sum of acceleration force, braking force and centrifugal force (force
due to centripetal acceleration for the pointy heads). Front wheel
drive cars like the Accord tend to under steer. Centrifugal forces
acts more or less equally front to back. Only the front tires are
driven. So at the extreme the front tires will tend to slide before
the rears, because the have more side force on them. This causes the
car to steer to the outside of the turn. Backing out of the throttle
tends to solve this problem, so this isn't so bad. Rear wheel drive
vehicles tend to over steer when power is applied vigorously in a turn.
This causes the rear wheels to loose traction and steer the car to the
inside of the turn. This is great fun, but a dangerous situation can
occur. Backing out of the throttle may cause the over steer to stop.
It can also cause the over steer to suddenly increase and spin the car
out. Why is this? When you accelerate, weight transfers back and
increases traction on the rear tires. When drop the throttle you lose
this weight transfer, traction on the rear lessons (traction of the
front increases) and the rear spins out to the outside of turn. Ask
anyone who drove a Porche 911 hard in the bad old days before all this
helpful VSA stuff. Judiciously applying brakes to each tire can steer
the car (remember our ABS example) and overcome, to some extent, errors
in judgment.

 

This is such a great in depth explanation!!

I copied and saved as word documents.

Thank you so much.