review of abs and esp braking systems

7/31/2019 Review of ABS and ESP Braking Systems

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Review of ABS and ESP braking systems

Since the first ESP (electronic stability programme) system appeared on a Mercedes-Benz model in

1995, braking system manufacturers have been predicting significant demand as appreciation of ESP

among drivers of the middle and lower segments of the car market grows, writes Matthew Beecham.

ABS (anti-lock braking system) was the first slip control technology. The aim of ABS is to limit the

pressure to any wheel which decelerates too rapidly, allowing maximum stopping force to be applied

without lock-up. When the brakes are applied, the tyres begin to slip. ABS measures the degree of slip to

determine when wheel lock will occur, reducing the hydraulic pressure to prevent it.

Traction control is like ABS in reverse. Instead of using the ABS system in the normal manner (to release

the brake of a locked wheel under braking) traction control aims to lock a wheel when it is spinning or

losing traction. Traction control is popular on four-wheel drive vehicles. Basically, it eliminates the

mechanical limited slip differentials thereby reducing weight and cost.

"When ABS was introduced, it was only fitted as optional equipment on high-end luxury models," said

Herbert Hemming, executive vice president of the Bosch Chassis Systems Control division. "Now it is

standard across all new vehicles within the European Union and in many parts of the world. ABS has

made braking safer, and has therefore made a major contribution to reducing accidents." When Boschproduced the first ever ABS in 1978, it weighed in at just over 6 kilograms. Today, Bosch offers ABS units

weighing 1.4 kilograms. The latest ABS technology also operates considerably faster and offers greater

levels of safety.

Meanwhile, fitment rates in emerging markets are mixed, as Dr Ralf Cramer, executive vice president,

Electronic Brake & Safety Systems, Member of the Management Board, Continental Automotive

Systems, said: "We see a big difference in terms of take rate of ABS in China and Brazil. In Brazil it is still

very low. We already have 80% take rate of ABS in China while ESC is slowly growing."

Continental Automotive Systems is developing "special brakes" for certain emerging markets. Cramer

added: "In the developed markets like Europe, America and Japan, we look for technology with high-

end functionalities. For the emerging markets such as Brazil, Russia, India and China then, of course, we

as an industry strive to bring safety into those car markets, too. That means bringing the cost down. The

cars in those emerging markets are typically smaller compared to the premium cars found in the West.


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Consequently, we have focused on reduced weight and size of braking components. For example, we

are developing the MK100 for those markets where we will have 50% less size and 25% less weight yet

deliver the same level of performance."

While ABS prevents the wheels from locking during braking, and traction control stops the wheels from

spinning on acceleration, ESP goes one step beyond the functions of both these systems. ESP

permanently monitors the vehicle's motion and compares it with the driver's wishes (steering angle). If

the position of the steering wheel deviates from the actual direction in which the vehicle is moving, this

means that there is a risk of skidding. In this situation ESP comes into play, by applying the brakes on

individual wheels in carefully measured doses so that the vehicle is stabilised and more safely held on

course.

ESP consists of a hydraulic modulator and control unit with sensors which determine and evaluate thedriving situation. ESP hydraulics rapidly increase brake pressure on a single wheel in critical situations in

order to counteract the undesired skidding motion. This pressure increase automatically occurs on the

wheel, without driver involvement. The brake impulse can thereby stabilise the vehicle at all times and

return it to the proper course. The system may also reduce the engine torque, which provides an added

stabilisation effect. In a nutshell, the benefits of ESP for the driver include:

Improved steerability in critical driving situations;

Reduced danger of slipping or skidding;

Greater vehicle stability within physical limits; and

Optimised stopping distances.

Although ESP is already standard equipment on many luxury cars, an increasing number of mid-range

and small cars are being fitted with the unit.

In September 2006, the US National Highway Traffic Safety Administration (NHTSA) released a proposal

that will require electronic stability control (ESC ) to be standard equipment on all light vehicles sold in

the US. The NHTSA has apparently been keen to legislate in favour of ESC for some time, particularly on

SUVs. There was some discussion about ESC following the Ford Explorer tyre failure and rollover

problems at the beginning of the decade. NHTSA is demanding that all light vehicles in the US with a

gross weight of up to 4.5 metric tons are to be equipped with this active safety system, a requirement

that will be phased in gradually from the 2009 model year up to the 2012 model year. This would make

the US the first country to mandate the installation of an active safety system.


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Ford has already announced that it would put stability control on its entire line-up by the end of 2009

and General Motors is planning to have the technology on all vehicles by 2010. Several automakers have

made ESC standard equipment on SUVs.

During an eSafety forum held in Rome last May, European automakers and supplier companies joined

forces with the EU Commission and vehicle and road-safety organizations to instigate a public campaign

aimed at accelerating the market penetration of ESP safety technology. The latest example of this is the

"Choose ESC!" campaign which is designed to persuade car buyers to purchase only vehicles with ESP. In

China, too, the Development Research Centre of the State Council wants to make sure ESP becomes

widespread.

Indeed, Kevin Elgood, chief engineer, Asia-Pacific, TRW Automotive, said: "Vehicles equipped with

electronic stability control systems are steadily on the rise. . TRW currently supplies ESC systems to

more than a dozen vehicle manufacturers on nearly 40 models worldwide." His colleague, Gary

Dubberley, TRW's senior project manager responsible for ESC launches in Asia-Pacific, added: "We are

experiencing a growing application of ESC technology to vehicles manufactured in China, for the

domestic and overseas markets."

Meanwhile, UN experts are drawing-up plans to make ESP a global technical standard. The aim is to

supplement the existing requirements for braking systems, which can then be incorporated in nationallaw by the member states.

In late 2006, Bosch extended its ESP product family to include its so-called ESPpremium. "The system

can develop braking pressure even more quickly, yet operates more quietly and almost without any

vibration," said Hemming. Bosch says its ESPpremium compliments its existing ESP and ESPplus

products. The three systems together cover the varying demands made of the brake control systems

when applied in small cars, luxury cars, or in light commercial vehicles. A feature of the ESPpremium is

the new pump design, which has six pistons instead of the two used previously. Bosch says this has

allowed a reduction in pressure pulsation - the variation between the lowest and highest values of the

braking pressure developed - of 90% in comparison with earlier ESP units.

ESPpremium also develops braking pressure with a higher dynamic response than conventional systems,

enabling fast automatic emergency braking and improving the effectiveness of the braking assistant.


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Other functions optimize the agility of the vehicle and its handling. Bosch has grouped its activity in this

field under the term 'vehicle dynamics management', the networking of the braking system with active

steering and chassis systems.

Continental Automotive Systems plans to introduce a new generation of ESC control units into series

production from mid-2008. By integrating the yaw rate and acceleration sensors required for ESC

directly in the control unit, installation and integration work is reduced, says the company. The

company's designs means that the sensor no longer has to be fitted in the upper area of the steering

column near the steering wheel but can also be fitted in the engine compartment. The steering angle

sensor uses a technology to measure wheel speed developed in the mid-1990s by Continental

Automotive Systems in partnership with a French supplier. The idea of integrating an active wheel

speed sensor in the wheel bearing has become an industry standard for measurement of wheel speeds

and now has an 80% share of the market.

On balance, Germany's vehicle manufacturer's association, Verband de Automobilindustrie (VDA),

estimates that more than 90% of all German passenger cars on the market this year has ESP as standard.

"In Europe as a whole, it is a feature on 42% of all new automobile registrants," says the VDA. While

fitment rates of ESP have shown strong growth in Europe, the US market is set to double by 2011 thanks

to the recent NHTSA ruling.

review of abs and esp braking systems

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