Electronic Stability Control - Good or Bad (or Ugly???)

[JsTyLz]

In another post ESC came up and I am wondering how much it is affecting the the roll stiffness, if any? I assume none. I think the control is affected by the the self centering feel you gat from the steering column. If there is steering assist, then at low speeds the steering is loose, and at high speeds the steering is tight, without have to adjust camber, castor kingpin inclination etc.

What are your experiences on ESC and its advantages and disadvantages?

 

[GregLocock]

ESC brakes individual wheels. For a given lat acc the roll will still be the same, to within realistic tolerances.

The advantage is that it linearises the handling. The disadvantage is that it doesn't linearise the laws of physics.

Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[hutch325]

Yes, I agree with Greg. ESC is a brake-based system. Perhaps you're thinking of some other active handling systems like active anti-roll bars or active steering.

ESC is nice because it can reduce vehicle speed automatically or change the vehicle trajectory to mitigate a rollover, and can induce yaw moments to mitigate oversteer or (sort of) mitigate understeer situations.

 

[gt6racer2]

This is a confusing topic with the various systems. I'd break in down into yaw control ( your common ESC ) and rollover prevention ( commonly ESP ). ESC generally aims to make the car go where ( it thinks ) you want it to. ESP generally does the opposite by altering the vehicles dynamic response if it thinks you might be about to roll over. ESP systems became popular as an easy way to pass NHTSA's fishook test ( roll rate feedback ), and based on this "success" is to be mandatory. If you like to drive near the limit however you won't be fan of these systems as in order to act in time they have to severely limit the handling envelope. NHTSA has since realized that their rollover spec can be bypassed by preventing a vehicle from steering and are adding a steer response measure to stop the OE's dialing huge understeer. At the end of the day, ESP is a bandaid to mask poor vehicle dynamics. Given decent damping and roll stiffness most vehicles would pass NHTSA's test without it. ( BTW I've focused here on "on road" rollover mitigation. I realize that most rollover's are tripped events, in which case a vehicle going forward is much safer.. )

 

[JsTyLz]

Thanks for the tips so far.

I was wondering if the systems they have in place on many high end production vehicles actually help or hinder in terms of performance versus safety. To me, I would like to break traction slightly if the tires are warm and rely on the shearing action of the tires to provide better overall moment delivered, although maybe not as efficient.

One of the systems I am refering to are Stabilitrak by GM. I am under the assumption that this also limits the amount of torque the drive wheels see as to mitigate not only rollover as with a turning manuever, but also breaking traction when taking off from a dead stop and going straight, i.e. drag racing. I want all the power to go to the wheels when the foot pedal is fully depressed. I have the feeling that it is limited by these systems in my vehicle, but this is also the first time I have had AWD. Regardles my assumptions are purely subjective and I do not have any data to back them up.

THanks

 

[GregLocock]

TC is usually the second active system to go in after ABS.

The hierarchy is, roughly

ABS
ABS+throttle+spark control=TC
TC+lattac (or analogue) or roll angle?+SWA=ESP (antirollover)
ESP+yawvelocity (or analogue)=ESC (goes where you point it)

analogues are synthetic signals which estimate what the sensor would have given (sort of). For instance you don't really need to measure vx, lattac, yawv and SWA, most of the time as they are strongly related



Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.