New ramifications of applications & functions
ESP maintains its strong growth in Europe

Motion Trends,
PR, 23 August 2005.

Sixty seven percent of all newly registered passenger cars in Germany in 2004 had already been equipped with the Electronic Stability Program (ESP®). As could be shown by a Bosch study, this is a major increase by more than 20 percent in comparison to the 55 percent equipment rate in 2003.

Several studies confirm the high effectiveness of the active safety system when it comes to reducing the risk of an accident. They indicate that a comprehensive installation of ESP® has the capacity of reducing the number of so-called driver accidents with severe bodily injury by up to 50 percent.

The European Union has made a commitment to halve the number of fatal road accidents over the period from 2001 through 2010. " ESP® is an effective and furthermore available system which can contribute to reach this ambitious goal", said Herbert Hemming, responsible for sales in the Bosch Division Chassis Systems Control. Bosch was the worldwide first supplier to produce ESP® in 1995.

The reason for this major increase in the ESP® installation rate by 12 percentage points over 2003 is the strong growth of standard equipment of the safety system in the large-selling lower medium-sized class of cars. The share of cars sold with ESP® in this class increased from 60 to now 83 percent. ESP® has already become standard in the high-end and luxury class, now it is heading this way also in the medium class.

For compact cars, the share grew three fold from six percent in 2003 to 19 percent, but remains at a low level in absolute figures. "In this class, ESP® is mostly merely available as optional equipment and rare actively requested. A higher installation rate in this class of cars would greatly affect the number of serious accidents in Germany and cause an even further reduction of them", Hemming showed himself convinced.

The German Insurance Association, GDV, proved in a study that in Germany 25 percent of all accidents with seriously injured people and 60 percent of fatal accidents are due to skidding. This is exactly where ESP® renders active assistance. The German Federal Ministry for Traffic is of the same opinion. Dr. Stolpe, the Federal Traffic Minister, announced that rarely had a technological innovation generated such tangible and visible effect for greater road safety than electronic stability control systems. The European New Car Assessment Programme (EuroNCAP), which had previously focused on the examination and evaluation of passive safety systems, is now also more involved in active safety. As recently as end of June, the organization recommended to make the equipment with ESP® an absolute must when purchasing a new car. They share the same opinion that the system immensely reduces the risk of an accident by assisting the driver to stay in control of his car.

The installation rate with ESP® shows partly major increases from 2003 to 2004 in practically all other countries of the European Union as well: in France, from 35 to 39 percent and from 25 to 32 percent in Spain. In the United Kingdom, 29 percent of all new vehicles in 2004 were equipped with the safety system and 24 percent in Italy. Bosch calculates an installation rate of 37 percent of ESP® in new vehicles across all countries in Europe. This rate was still at 29 percent in 2003.

Trailing stabilising function - Having evolved from its ABS origins, ESP is not confining itself within the anti-skid corrective functions. With its range of sensors, ECU, network connections and actuators, the new generation ESP is inaugurating a new standard of predictive measures, amongst them the new trailer stabilising function.

The trailer stability assisting function recognizes initial swaying of the trailer and automatically brakes the vehicle briefly but effectively. The risk of pitching and thus of incurring an accident is dramatically reduced. An increasing number of models by many OEMs are meanwhile equipped with this function either as standard or optional equipment. Bosch installed it for the first time as standard equipment in 2001 with BMW in the X5.

When trailers start to sway dangerously, it is usually a result of the way of driving, speed, crosswinds, road condition and, on the other hand, mass distribution in the trailer and its tongue load. Caravans and horse trailers present a special risk. With pendular movements, one reaction proves to be especially effective: stepping on the brake. This reduces the speed of the vehicle train and causes a rapid stabilization. However, many drivers show the wrong reaction under stress and try to keep their tractor vehicle and trailer on track by counter steering. This will only amplify the swaying effect and finally lead to an accident.

According to statistics, 422 accidents with passenger cars and trailers happened on German freeways in 2004, and another 900 accidents were counted off the speedways outside of urban areas. More than 1,800 people were injured in these accidents or even killed.

The specific additional function of ESP® recognizes swaying on the basis of the typical yaw rate in the tractor vehicle. This allows for the right measures to be initiated at an early stage: the vehicle train is slowed down to a non-critical speed by automatically braking all four wheels of the tractor vehicle while simultaneously reducing the driving torque and thus ending the swaying movement. The additional software module in the ESP is activated as soon as the electrical connection cable of the trailer is plugged into the tractor vehicle.

Even without the additional function for trailer stabilization, ESP provides greater safety for drivers of vehicle trains. While it is not capable of completely stabilizing the train, it can, however, limit the pendular movement by braking down the individual wheels of the tractor vehicle. This basic function of stability control is also active in the extended ESP. Both functions act together when it comes to wide pendular movements and mutually enhance their effectiveness. The extended ESP also functions when mechanical rolling suppressors are used, which are mounted between tractor vehicle and trailer and produce friction torque at the coupling port.

New steering angle sensors for end 2006

On a differently related level, and within the continuing advance of the ESP concept, Bosch announced recently (May 2005) its current development of a new generation of steering angle sensors which differ from their predecessors in having a modular construction. This allows different versions to be produced to cover a range of different functional requirements.

The simplest version is a competitively priced absolute measurement sensor with a range of measurement of 90 degrees. The most high-performance version is a 780 degree multiturn sensor featuring customer-specific programmable signal processing with built-in redundancy.

The new generation of Bosch sensors with the designation "LWS 5" can thus be used for a wide range of applications. The very different requirements of the Electronic Stability Program (ESP), an electric or electro-hydraulic power steering system, adaptive lights or a parking assistance system can in each case be met with a precisely matched version. The sensors are fully compatible with the previous LWS 3 model, so that they can be fitted to existing systems without any modification. 

The functional principle of the LWS-5 sensors relies on two resistance bridges positioned at 90 degrees to each other, the bridge parts consisting of GMR (Giant Magneto Resistance) elements. In the simple version, when the steering wheel is turned, a measurement cog wheel rotates over a GMR element. An integrated microcontroller uses the change in the bridge voltage to accurately calculate a steering angle of up to 90 degrees. No external control unit is required. The LWS 5 version is used for measuring larger steering angles; it has not one, but two, measuring cog wheels with a differing number of teeth. This expands the precise range of measurement (according to the Nonius process) to 780 Grad, which allows more than four complete turns of a steering rod to be measured.

Since in all the sensor versions the steering angle data is stored at a resolution of 0.1 degrees only in the relative position of the two measurement cog wheels to each other, the new Bosch sensor – like its predecessors – requires no quiescent power supply when the engine is switched off. Nonetheless, the sensor immediately registers the current steering angle as soon as the ignition is switched on. In addition to the increased range of measurement, the Nonius process also offers additional safety, because in the interaction of the two cog wheels there are only a certain number of plausible steering angle settings. If measurements diverge from these, they are noted in the interface protocol as invalid. The wide-ranging monitoring functions cover the entire signal chain from the cog wheels to the measurement of the steering angle and the emission of the signal. Further safety elements of the LWS 5 are redundant microcontrollers working on the master/slave principle and the systems for monitoring them.

An LWS 5 is fitted as standard with a CAN interface. Customer-specific interfaces and individual programming of the microcontroller are possible. The new steering angle sensor is expected to be available from the end of 2006.