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| Keeping one step ahead | March 2005 |
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| According to statistics provided by Robert Bosch, 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. To combat this bête noire of the road, Bosch devised an anti-lock braking system ABS, the shorthand which sprang from the German word antiblockiersystem, in 1976. While it had a relatively slow take-up to begin with, it has become such a de facto part of the car that it has become a standard in Europe so that 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 that, but the success rate has been patchy. 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 US, 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. ![]() At its most basic is ESP, ESP plus (business class) and ESP premium (first class) and while they would not divulge prices, it was clear 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 include traffic jam assist whereby the driver of a car with 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 per cent lower.” The six pump system means that 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 centre-clutch coupling on a rear-wheel driven 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.” As an addendum to this, we were taken to Bosch’s new winter test centre in North Sweden to drive cars fitted with different ESP iterations, including prototype versions of ESP premium. Despite driving on ice lakes, sometimes with the system on and at other times with it off to demonstrate one’s prowess in driving in difficult conditions, one always felt safe because even a full 360° spin would lead to no harm. However, on arrival back to the UK on a wild and stormy evening, the lack of EPS on your correspondent’s car, something never really considered before, was the cause of real concern when charging down the motorway. It is only when you have first-hand experience like this that the true benefits of ESP become apparent. However, it would be a rather expensive operation for Bosch to ship every driver of the world to northern Sweden to experience the benefits.
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