Stability Control 101

[Lexusfreak]

Thought this was a very good read.....a little long perhaps, but very informative. Enjoy! B)

From Canadiandriver.com...

November 28, 2005

Stability control: the guiding hand

By Jeremy Cato

It was a dark and stormy night. Bear with me: though this sounds like the beginning of a very, very bad novel, it's not.

2005 Porsche 911 Turbo S. Photo: Porsche. Click image to enlarge

Yes, it really was dark and stormy and I really was test driving a Porsche 911 Carrera Turbo with gobs and gobs of power, cutting up slippery, winding roads leading to my favourite ski resort, Whistler, B.C.

Then it happened: I went into corner hot, hit an icy patch and for a brief moment I thought I was toast. And I would have been in the bad old days before electronic wizardry began turning cars into safety modules with life-saving brains of their own. My Porsche would have whipped around like a pendulum weight launched from a slingshot. If my driving were perfect, I might save myself from the ditch, but not likely. This sort of thing simply happens too fast for even the best driving skills to come into play.

But in the 21st century it is a different matter. In my case, a high-tech system Porsche calls Porsche Stability Management (PSM) took over to make things right for a driver – me – who was in over his head. In other words, PSM noticed instantly that I was taking a corner too fast, that the tires were losing grip. Faster than the blink of an eye, a computer brain ordered brake application at the appropriate wheel.

In my case with the rear stepping out, a condition the experts call "oversteer," the outer front wheel received a carefully modulated application of braking and the car came back into line. If I had been pushing or running wide in a corner, what they call "understeer," the brain would have told the brake at the inner rear wheel to get to work.

On this night, PSM did its magic and I am here to tell the tale. The Porsche's electronic stability control system (ESC) took a potential oversteer incident and corrected automatically. I made a tight and slick corner without incident and ultimately arrived in Whistler where the skiing turned out to be great, by the way.

This past Spring, Lexus officials were showing off what they think is an even better ESC system. The Lexus people call theirs "Vehicle Dynamics Integrated Management" or VDIM. It is, arguably, one of the most sophisticated ESC systems in the world today. Like Porsche's PSM, VDIM, too, is designed to keep drivers from losing control.

2006 Lexus GS 430. Photo: Bill Petro, Lexus. Click image to enlarge

But Lexus officials say their system has a new twist: the computer controls are programmed not just to react to spins by applying braking to the appropriate wheels and modulating engine power, but rather to anticipate problems and correct them before they become out-of-control catastrophes. The correction comes in the form of automatic braking at individual wheels, as needed, and adjustments of the throttle, as well.

"In other words," said Lexus technical consultant Jeff Powell, "VDIM monitors the balance of the vehicle and can therefore anticipate problems before they occur, rather than reacting after the loss of stability."

Of all the electronic stability programs I've tested, VDIM and PSM are the two least intrusive systems available – that is, they do their work without startling the driver. They are also the most effective. Both really and truly do save drivers from themselves.

However, Lexus and Porsche are by no means the only manufacturers offering electronic stability control. Most car companies offer some sort of ESC system on a variety of models, even sub-$20,000 SUVS like the Kia Sportage. In fact, about 40 per cent of vehicles in 2005 come with stability control standard or as an option, up from about one-third in the 2004 model year. Still, the greatest concentration of standard ESC systems can be found on luxury models and sport-utility vehicles (SUVs).

How electronic stability control works

All ESC systems have the basic hardware in common, though there are major differences in the use of hardware components. And then there is the software -- the algorithms within the computer brain (microcomputer) that evaluate signals from several sensors and then order the appropriate braking, and in certain cases, engine throttle and spark intervention, as well.

First, the basic hardware:

Steering sensor: monitors steering wheel angle to determine if the vehicle is headed in the intended direction.

Wheel sensors: determines if the vehicle is sliding by monitoring individual wheel speeds.

Yaw sensor: determines if the vehicle is sliding by measuring movements around the centre vertical axis.

Lateral acceleration sensor: determines whether a vehicle is sliding by measuring the side-to-side centrifugal forces generated when cornering.

The information from these sensors is processed slightly differently, and at different speeds, depending on the system. The interventions ordered up by the computer brains also differ in degree and comprehensiveness, depending on the system.

The faster, more sophisticated ones come in the more expensive vehicles. The quicker ones make more than 150 different corrections per second to keep a vehicle on its intended track. Still, they all order some level of extraordinarily fast braking to correct a number of potentially fatal driving situations:

Oversteer or the rear-end sliding out. For instance, in a left-hand curve ESC corrects oversteer by braking the front right wheel to generate counteracting torque. For a right-hand curve, braking would be applied on the left front wheel.

Understeer or when the front wheels push ahead rather than follow the cornering inputs of the steering wheel. In a left-hand curve, to correct understeer brake force is applied to the left rear wheel. For a right hand curve, the braking goes to the right rear wheel.

In addition to braking, many ESP systems are integrated with the engine management system. Together, they coordinate a cut in engine power by shutting down the throttle and/or ignition spark to one or more engine cylinders. At the other end of the spectrum, less elaborate systems might allow only for braking at two wheels. These are called two-channel systems, as opposed to the four-channel systems described above.

What will change in the coming months and years is the general availability of electronic stability control right across the market. These systems, which have been available in limited numbers since the mid-1990s, are now poised to go completely mainstream.

Why? First, the cost of ESC is going down. The price of the systems varies by manufacturer, but it costs consumers an average of less than $1,000 to add electronic stability control to a vehicle, according to a coalition of suppliers who make the technology. Second, ESC appears to work. The first major studies by independent bodies using real-world crash data arrived last Fall and they tell the story.

Take the initial results of a recent U.S. Government study from the National Highway Traffic Safety Administration or NHTSA. It showed that ESC reduced single-vehicle fatalities by 63 per cent in SUVs and ESC reduced single SUV crashes by 63 per cent. Cars equipped with ESC had 30 per cent fewer fatal crashes, and car crashes of all sorts dropped 35 per cent with ESC on board. True, the study sample sizes were small; only 7.4 per cent of light vehicles sold in 2003 had some kind of ESC.

However, the NHTSA study results have been bolstered by an insurance industry study which found that ESC systems could save as many as 7,000 lives each year in the U.S. if they were standard equipment on all vehicles. The Insurance Institute for Highway Safety (IIHS) found ESC systems reduced one-car fatal accidents by 56 per cent and ESC systems reduced all one-car accidents -- fatal and nonfatal -- by 41 per cent. A 2003 study in Japan also showed a decrease of 35 per cent in one-car crashes thanks to interventions by ESC. Single-vehicle crashes account for more than half of all vehicle crash fatalities each year in North America.

In releasing the study results, IIHS official Russ Rader said there is mounting evidence that ESC "provides a big benefit, and if you're shopping for a new vehicle it's definitely money well spent to buy it."

CanadianDriver contributor Jeremy Cato (driving) and CanadianDriver editor Greg Wilson test the 2006 Lexus GS 430's VDIM.

Testing the braking stability of the 2006 Lexus GS 430. Photos: Bill Petro, Lexus. Click image to enlarge

However, most drivers remain unaware of what stability control does, and most car sales people don't know how to sell stability control as a feature. That's why Lexus officials went out of their way to showcase the benefits of VDIM on soaking, slippery skid pads at the introduction of the GS300 and GS430 luxury sedans. The VDIM system is standard on the $74,700 GS430 and it features prominently in Lexus advertising on that model and others, such as the RX400h gasoline-electric hybrid SUV, which also has VDIM as a standard feature. "It's part of our performance message with Lexus – safety performance," says Lexus Canada advertising manager David Brimson.

Companies that supply ESC are also getting into the promotions act. Continental Teves, a large supplier of ESC systems to automakers, has a bright orange tractor trailer equipped with a six-seat motion simulator that bounces around people in 3D glasses to show them the benefits of ESC. The trailer, which has travelled to various auto shows and other events, displays a movie of a mother describing to her friend how she narrowly averted hitting a child in the road thanks to her electronic stability control.

"Why doesn't every car have it?" the friend asks. "You got me," the mother responds.

Emerging safety regulations have also begun to have an impact on public awareness and consumer demand. In the U.S., government regulators have begun rating vehicles for rollover propensity and this has cast a bright light on SUVs, which because of their high centre of gravity have a greater tendency to tip up onto two wheels in more aggressive driving manoeuvres. Tipping up on two wheels is the first step in a rollover. More than a third of 2004 SUVs tested were prone to rollover on the track, thus it's not surprising that manufacturers are moving quickly to make ESC standard on all their SUVs.

2003 Chevrolet Suburban with StabiliTrak. Photo: GM. Click image to enlarge

General Motors Corp. is among the automakers leading what will be a huge increase in the installation rate of ESC in not just luxury vehicles and SUVs, but everyday automobiles. Earlier this year GM said that by 2010 all its new cars and trucks in Canada and the U.S. will have some version of GM's anti-skid technology called StabiliTrak.

"Except for the growing use of safety belts, we have rarely seen a technology that brings such a positive safety benefit as electronic stability control," said GM's senior executive Gary Cowger in an interview earlier this year.

GM may have been first among the traditional Big Three North American Automakers to commit 100 per cent of its line-up to ESC, but Ford Motor Co. and the Chrysler Group are dramatically increasing their installation rates, too. Suppliers say ESC will be installed on 50 per cent of new cars and light trucks by 2008. Perhaps within a decade ESC will be standard on all new vehicles as a result of a combination of consumer demand a regulatory pressure. Perhaps.

Lexus officials such as Brimson and others in the auto industry say it is difficult to demonstrate ESC in the showroom and that remains a challenge for the car business. Also, even though the technology has been around for more than a decade, it is marketed under at least 15 different brand names, with at least six different automotive suppliers offering one version or another. With all these different ESC systems for sale under so many different names, consumers might be excused for feeling a little confused.

In a nutshell, the situation is not at all like what has happened with ABS or anti-lock braking. While the automakers offer different versions of ABS right across their various ranges, ABS remains the one universal tag that all of us can understand. Thus, ABS enjoys widespread acceptance. Not so with the range of ESC systems out there. Brand names include GM's StabiliTrak, Porsche's PSM, Lexus's VDIM and Ford AdvanceTrac.

But all automakers agree that safety has become a top issue with consumers. Virtually all new models now come with air bags and seatbelts for "passive" protection, so the next frontier in safety must be "active" protection which includes ESC. As a front-line recipient of the benefits of ESC, I'm all in favour of more widespread acceptance of these systems.

[ArmyofOne]

JMO, I dont like traction control, especially if i have a manual trans, there is no need. all it does is hinder things. If you know how to drive fast (are trained in it) and you knwo your vehicle, its not thta hard to realize when you are at your cars limit.

I do agree that it savs lives, becuase the vast majority fo america isnt trained in high speed handling of vehicles like me and few speedfreak friends who had money to burn one week. LOL.

But if it were up to me, i wouldnt have it on any vehcile i own. and i dont. :)

[Toysrme]

I love electronic controls. The best drivers will never be as good in any way a computer can be with good engineering behind it. God forbid you take the average person.

But ya, it's way more fun if you don't ahve any, or can turn it off.

The side way is the fun way!

[nc211]

I agree, I hit some wet leaves this morning coming in and juiced the gas, got a little sideways! Great way to wake up in the morning. Oh I love rear wheel drive!

[dcfish]

I agree, I hit some wet leaves this morning coming in and juiced the gas, got a little sideways! Great way to wake up in the morning. Oh I love rear wheel drive!

←

I love the rear wheel drive also, Better when I turn the VSC off on the GS. When I drive the ES it is a whole different ballgame.