According to statistics provided by Robert Bosch GmbH (www.bosch.com), skidding is the cause of one quarter of all accidents. They also show that 60% of all accidents with fatal injuries happen through side crashes caused mainly by skidding. So to combat this bête noire of the road, Bosch devised the anti-lock braking system (ABS), the shorthand which sprang from the German word antiblockiersystem, in 1976. The technology, of course, has spread to other suppliers in the subsequent years. While it had a relatively slow take-up to begin with, ABS has become such a de facto part of the car that it has become a standard in Europe: all cars sold in the 25 countries that comprise the European Union must have it fitted. However, Bosch is still not satisfied and for the last 10 years it has been selling its Electronic Stability Program (ESP) system, a system that detects skidding almost before it starts and actively counteracts it, but the market success rate has been patchy for ESP. While some 64% of all new vehicles in Germany were fitted with ESP in 2004, the overall share for Europe as a whole is just 36% for the same period. The installation rate is even lower in other parts of the world, with the U.S., for example, recording just over 10%, although Bosch is confident that it will change following the announcement by the Big Three that most SUVs will be equipped with ESP as standard by 2006.
Various studies have reinforced the benefits of ESP. DaimlerChrysler, for example, said that the standard fitment of ESP in all Mercedes-Benz passenger cars had reduced their incidence in "driving accidents" in Germany by around 42%. A "driving accident" is defined as one in which the driver loses control of the vehicle without other road users being involved. A NHTSA (U.S. National Highway Traffic Safety Administration) study also showed that passenger cars that had been fitted with ESP as standard equipment from 1997 to 2002 had, on average, 35% fewer driving accidents than for the same vehicle models before the standard fitment of ESP, with the number of fatal driving accidents reduced by 30%. In the SUV class, the impact was even greater: according to the study, the number of road accidents in this category was reduced by 67% and fatal road accidents reduced by 63%.
With all these statistics in mind, whether it be the number of vehicles that still do not have ESP fitted as standard or else the number of accidents and fatalities that can be reduced, Bosch is going on the offensive not only to try and get better market acceptance and penetration, but even to get it written into a standard, as has happened with ABS in Europe. Already 2005 has been declared as the "year of ESP" by a member of the European Commission and upheld by the EU Commissioner responsible for traffic, so certain lawmakers are "on message".
In a world where ABS, even 27 years later, is still perceived as having a "super-braking" effect rather than as a methodology of anti-skid whereby the driver is less likely to lose control, it does look like it could be an uphill battle for the German company. To this end, Bosch has launched the "ESPerience" dealer training program to improve awareness through dealerships.
As is the way with technology, though, we are into new generations of ESP with the main focus being on networking the passive safety systems with predictive driver assistance aids. Bosch has incorporated these functions into the CAPS—Combined Active and Passive Safety Systems—program. Additionally, Bosch is developing a scalable product line on the basis of ESP. There are going to be three different levels of ESP. Essentially, there are ESP, ESP plus and ESP Premium. While Bosch executives would not divulge prices for each, it was clear from talking to different engineers that there would be price premiums to pay on the advanced systems. ESP plus, for example, which will start to be seen on some cars this year, has added functionality that includes traffic jam assist, whereby the driver of a car with an automatic transmission can take his or her foot off the throttle pedal and allow the braking system to initiate a slow deceleration and electronic brake pre-fill. ESP Premium will offer automatic brake disc wiping and be linked into the adaptive cruise control system for stop and go.
"We have changed the pump system and the pump concept," says Hubertus Wienken, a senior engineer at Bosch working on the next-generation ESP systems. "Normally there are two pump elements that provide the active pressure build up, but with CAPS we have six pump elements—three for each circuit. This is because it is quicker with a higher hydraulic flow rate, but it is around 4 kg heavier than ESP 8—the current ESP generation. The hydraulic flow rate is up to 98% lower." The six-pump system means there is less vibration on the pedal during ABS intervention and pedal comfort is much better than on normal ESP. A high level of vibration not only can irritate the driver but also cause them to lift off for fear of damaging the brakes. With the system being developed by Bosch, the intention is to inform the driver by getting the pedal feel to firm up while the vibration pulse, which remains present, is greatly reduced.
Another function that Wienken and his team are working on is continuous current control. "OEM requirements mean that they will not accept sudden voltage drops so we have developed this continuous current control," says Wienken. "Normally there is a drop in voltage when switching on the pump, which in bad conditions can lead to flickering lights. It can also badly affect the accumulator in the car which can suffer from a reduced lifetime. Now we start the pump very smoothly with current controls so there is no sudden drop in voltage. This means no damage to the accumulator and no flickering lights.
"Due to the layout of the ESP Premium," continues Wienken, "we have a higher system runtime, a higher lifetime endurance that gives us the possibility of having more value-added functions for the end-customer such as touch-activated deceleration. In a normal ESP without any additional functionality, there are five hours of pump-run time during the whole life, which is nothing, but as soon as you start with additional functions then it rapidly increases—and ESP Premium is prepared for that. ESP 8 can get up to 200 hours but ESP Premium can do 400 hours because more functions are activated. We can also incorporate a scaleable micro-controller contact and include other software from the OEMs," claims Wienken. "For example, the ACU normally controls the center-clutch coupling on a rear-wheel drive car. However, we can implement this software in our ACU meaning that one can be eliminated. The same goes if it’s adaptive cruise control so we can save some space for additional functionality."