MMF320 Active Safety Department of Machine and Vehicle Systems

Chalmers University of Technology Gothenburg, Sweden

Potential of integrated safety systems for improved crash

protection

Spring 2006

Group 1

Finnis Leen

Orlando Sanchez

Audrey Heidinger

Birol Gonul

Adrien Castaldini

Xavier Bertrand

Outline

Introduction ................................................................................................................................... 3 1. Sensors technology............................................................................................................... 4

a. Steering angle sensor ....................................................................................................... 4 b. Speed and acceleration sensors ....................................................................................... 4 c. Surround sensors .............................................................................................................. 4 d. Radio Communication ....................................................................................................... 7

2. Integrated Safety – Interior.................................................................................................... 9

a. Seat ................................................................................................................................... 9 b. Dashboard....................................................................................................................... 15 c. Airbags ............................................................................................................................ 18

3. Integrated safety - Exterior.................................................................................................. 21

a. Active pedestrian protection ............................................................................................ 21 b. Adaptive structures.......................................................................................................... 24

4. Dynamic integrated safety systems .................................................................................... 25

a. Active steering................................................................................................................. 25 b. ABS ................................................................................................................................. 26 c. Brake Assist System ....................................................................................................... 27 d. Lane Departure Warning. ................................................................................................ 27 e. Driver alertness monitoring ............................................................................................. 27 f. Stability control ................................................................................................................ 28 g. Active rollover protection ................................................................................................. 29 h. Collision avoidance systems ........................................................................................... 30 i. Route guidance systems................................................................................................. 30 j. Future systems................................................................................................................ 30 k. Discussion of integrated dynamics systems.................................................................... 32

5. European programs working on integrated Safety Systems ............................................... 33

a. AIDE - Adaptive Integrated Driver-vehicle InterfacE ...................................................... 33 b. PReVENT ....................................................................................................................... 33 c. Electronic Architecture and System Engineering for Integrated Safety Systems ........... 35

6. Discussion........................................................................................................................... 37 Conclusion .................................................................................................................................. 40 References.................................................................................................................................. 41

Introduction In the past decades safety has taken an ever increasing role in the automotive industry. Apart from probably still the most life saving device, the seatbelt, more and more systems have appeared to prevent or mitigate crashes. Passive safety covers all the systems and features designed to protect vehicle occupants if an accident occurs. These include seatbelts, seatbelt tensioners and airbags as well as construction features like the safety steering column and a crash-resistant body shell. The last 2 decades we have also seen the rise of active safety systems. Active safety is a term normally used for those systems that help avoid accidents. With (computer) technology advancing more and more, systems and operations have become possible to actively protect the occupants of vehicles from an accident. An early example of these systems is an ABS brake system; at this point full vehicle stability programs are already available on the market. In this report we will look at all the different systems, both passive and active, that are currently present in a vehicle and systems that are likely to be used in the future. The discussion of these systems will be divided into 4 main groups;

• Sensor technology • Interior safety devices • Exterior safety devices • Dynamic safety systems

The aim of this report is to investigate how these systems are working together and could work together in an effort to reduce the number of injured and killed people in accidents. This is so-called integrated safety; the integration of active and passive safety systems within the vehicle to sense and interpret different traffic situations and to act in such away that accidents can be avoided or at least the damages can be minimized. In this report several existing and future integrated safety systems will be discussed A very important factor in the development of integrated safety systems (same for most active safety systems) is the interaction of the system with the driver. Using new active/integrated systems has great potential since such a system can already act in the valuable time a human needs to react. However it is also thinkable that the reaction of the driver to the actions of the system might actually cause an accident. In this light it s also especially important to keep liability issues in mind; a safety system might end up causing more accidents than if it is not used! These questions will be addressed in the discussion at the end of this report.

1. Sensors technology This section focuses on sensors, controllers and actuators which are needed in passive, active or integrated systems in cars. These systems can be as simple as switches or as complex as active radar or sonar systems.

a. Steering angle sensor A steering angle sensor is very simple, but is becoming more and more important, as several systems rely on it, like the ESC, the suspension control or the active steering. This sensor consists of an encoder, a photo emitter, a photo receiver and an optic disc (having opaque and transparent parts). The receiver counts the signals received when turning and deduces the steering angle. It is usually installed with other sensors such as a steering torque sensor or a steering angle velocity sensor.

b. Speed and acceleration sensors The fast and accurate measurement of speed in both longitudinal and rotational directions is very important because many systems rely on this information, like the steering angle measurement, such as the ESC, the BAS or the ASR. The determination of speed is based upon the anisotropic magneto-resistance (AMR) effect. But the proper functioning of the ESC requires measurements of the vehicle acceleration. So, sensors to measure acceleration, like a yaw rate sensor, a lateral acceleration sensor as well as a longitudinal acceleration sensor are often installed in cars. These sensors use several principles:

The piezoelectric principle: a piezoelectric material is sandwiched between a mounting plate and a mass. When the mass is affected by a force generated by the acceleration, it transmits the force to the piezoelectric material. Piezoelectric materials generate an electric charge proportional to the force applied on it.

The capacitance principle: in capacitive sensing systems, a mass is inserted between two

capacitive plates and a voltage is applied to hold the mass in balance. When there is any disturbance on the mass between the capacitive plates, there is a corresponding voltage change.

c. Surround sensors Today, the components for the realization of predictive driver assistance systems – highly sensitive sensors and powerful microprocessors – are available or under development with a realistic time schedule, and the chance for the realization of the “sensitive” automobile are fast approaching. Soon sensors will scan the environment around the vehicle, derive warnings from the detected objects, and perform driving manoeuvres all in a split second faster than the most skilled driver. Electronic surround sensing is the basis for numerous driver assistance systems – systems that warn or actively intervene. Figure 1 shows the detection areas of different sensor types. Until now, due to the limited availability of sensors, only a few driver assistance systems could be established on the market. However some examples exist such as sensors integrated in the bumpers, which forward an acoustic or optical warning to the driver as soon as he approaches an obstacle. In the meantime, this system is widely used and has high acceptance with the customer. It is already in series-production in many vehicles [1].

Fig. 1: Surround sensing: Detection fields of different sensors

Upon availability of appropriate sensors, new systems will be introduced in future vehicles. Their spectrum will range from warning systems to systems with vehicle interaction [2]. They are listed in the following sections.

o Ultrasonic sensors Reversing and Parking Aids today are using Ultra Short Range Sensors in ultrasonic technology. They have a detection range of approximately 1,5m. They have gained high acceptance with the customer and are found in many vehicles. The sensors are mounted in the bumper fascia. When approaching an obstacle the driver receives an acoustical and/or optical warning. The next generation of ultrasonic sensors has a detection range of approx. 2.5m, and thus, explores new applications like Parking Space Measurement and Semiautonomous Parking.

o Long range radar 77 GHz The 2nd generation Long Range Sensor with a range of approximately 120m is based on FMCW Radar technology. The narrow lobe with an opening angle of ± 8° detects obstacles in front of the own vehicle and measures the distance to vehicles in front. The CPU is integrated in the sensor housing. The sensor is multi target capable and can measure distance and relative speed simultaneously. The angular resolution is derived from the signals from 4 Radar lobes. Series introduction was made in 2001 with the first generation. Figure 2 shows the 2nd generation sensor. It has been introduced into the market in March, 2004. At that time this sensor and control unit was the smallest and lightest of its kind on the market. The antenna window for the mm-waves is a lens of plastic material which can be heated to increase the availability during winter season. The unit is mounted in air cooling slots of the vehicle front end or behind plastic bumper material by means of a model specific bracket. Three screws enable the alignment in production and in service [2].

Fig 2: 77 GHz Radar sensor with integrated CPU for Adaptive Cruise Control

The information of this sensor is used to realize the ACC function (Adaptive Cruise Control). The system warns the driver from following too close or keeps automatically a safe distance to the vehicle ahead. The set cruise speed and the safety distance are controlled by activating brake or accelerator. At speeds below 30 km/h the systems switches off with an appropriate warning signal to the driver. In the future, additional sensors (Video, Short Range Sensors) will be introduced in vehicles. They allow a plurality of new functions.

o Short range sensors Besides ultrasonic sensors, 24 GHz radar sensors (Short-Range-Radar (SRR)-Sensors) or Lidar sensors can be used in future to build a „virtual safety belt” around the car with a detection range between 2 and 20m, depending on the specific demand for the function performance. Objects are detected within this belt, their relative speeds to the own vehicle are calculated, and warnings to the driver or vehicle interactions can be derived. Today, there is still a limitation for the introduction of the 24 GHz UWB (Ultra Wide Band) Radar imposed by the pending release of the frequency band for the mentioned applications. This release has been given in 2002 for the USA. In Europe this process is still going on and under intensive discussion, mainly opposed by the established services such as Earth Exploration Satellite Services, Radio Astronomy and Fixed Services. A worldwide harmonization is necessary.

o Video sensor Figure 3 shows the current setup of the Robert Bosch camera module. The camera is fixed on a small PC board with camera relevant electronics. On the rear side of the PC board the plug for the video cable is mounted. The whole unit is shifted into a windshield mounted adapter. CMOS technology with non linear luminance conversion will cover a wide luminance dynamic range and will significantly outperform current CCD cameras. Since brightness of the scene cannot be controlled in automotive environment, the dynamic range of common CCD technology is insufficient and high dynamic range imagers are needed.

Fig. 3: Video camera module

o Actuators

Vehicle speed can be controlled by three different ways:

Engine Control: it can be done by separate or integrated electronic throttle control (EGAS), combined throttle control with engine management, pneumatic or electric cruise control actuators or EDC systems for diesel engines.

Transmission control: electronic transmission control in vehicles with automatic

transmission. It is possible for the ACC to shift down to decelerate with the engine.

Brake control: active brake control is based on the hydraulic systems for standard traction control or VDC and does not require a smart booster. It allows a quiet and comfortable deceleration control. The ability to accelerate or decelerate, respectively, is limited to about ± 2 m/s2 (~0.2 g) for safety reasons and customer convenience [4].

o Technical Limitations Technical limits for different radar sensor units are already explained. Limitations due to geometrical obstructions are characteristics for all autonomous ranging sensors today. Tops of the hills and bottoms of valleys naturally limit the longitudinal range. Other limitations arise from the difficulties in predicting the course far in front of the ACC equipped car. It is shown on figure 4.

Figure 4: Lane prediction

This is mainly due to two reasons: errors in determining the actual value of the road curvature and parts of the road which can have non-constant curvatures. This problem is the most restrictive limit to any ACC and a matter of current research [5].

d. Radio Communication

One of the newest techniques used is the radio communication between an on going car and the surrounding environment. This technique is developed due to the computer and material advances, as it is nowadays possible to implement this kind of devices in cars and at roadsides. The principle is to exchange information with the surroundings in order to warn the vehicle’s driver about possible risk situations or possible traffic congestions on the road. This exchange of information can be done between the on board equipment of the vehicle and a fixed road equipment or a traffic information centre. This exchange is possible between the surrounding cars as well [6]. This communication is done through a fibre optical “IP” unit. This unit allows the exchange of several different data with high speed and joint of communication [7]. The information sharing has an important role on the vehicle communication system. There are three ways of sharing information:

o Radio beacons On this method the information is transmitted by radio waves to the beacons and then this information is transmitted to the cars on radius of approximately 70 meters with a capacity of 64 Kbps, as is shown on figure 5 [8].

Figure 5: Information sharing through radio beacons

o Optical beacons

It is method very similar to the Radio Beacons except on the way of transmitted the information to cars. These beacons are mainly installed before road interceptions and the information is transmitted by the cars sensors. These devices have a capacity of 1 Mbps and a range of 3,5 meters [8].

Figure 6: Information sharing through optical beacons

o FM multiplex broadcasting

This information sharing method is restricted by area of range of the broadcast. This means that the information it is only available on a determined area. However, the information can be shared through the FM broadcasts areas. So, in this model the information is sent by the local FM broadcasts [8].

2. Integrated Safety – Interior This part deals with these systems which can be found in the interior of cars, mainly represented by three parts: the seat, the dashboard and airbags.

a. Seat One interesting example is the A.I.S.S. [9] (Advanced Integrated Safety Seat) designed for frontal, rear, side, and rollover crash protection. This device is not only implemented for the driver protection but also for the right front passenger position, which accounts for the second most common location of fatalities and injuries among car occupants. The A.I.S.S. restraint features included are:

Dual linear recliners (rear impact) Pyrotechnic lap belt pretensioner (frontal impact and rollover) 4 kN load-limiter (frontal impact) Extended head restraint system (rear impact and rollover) Rear impact energy absorber (rear impact) Seat-integrated belt system (frontal, rear impact and rollover) Side impact air bag system (side impact)

An advantage of integrated seats is that they have the belt anchorages on the seat itself as opposed to conventional seats where the shoulder belt upper anchorage is located on the car upper body structure. Therefore, the belt fit is considerably improved regardless of the seating position, and the assembly of the seat in the car becomes much easier with this design as the belts are part of the seat. The A.I.S.S. seat system is also designed to function with the body structure to resist passenger compartment intrusion in side and rollover crashes. This section, made from an interesting NHTSA report, is divided in four parts according to the crash situation (frontal, rear, side and rollover) and relates how these passive safety devices are implemented and how they can be improved by being integrated with the use of active systems as Electronic Stability Control (ESC), passengers’ sensors system or external smart cameras.

o Frontal Impact Pyrotechnic lap belt pretensioner In frontal impacts, pyrotechnic lap belt pretensioner takes up slack in the seat belt and induces energy absorption during the early forward travel of the occupant. When the device is fired, the pretensioner pulls down on a cable that is attached to the belt buckle. This effectively removes the extra slack, and cinches the occupant to the seat. Some studies have reported that this also prevents submarining by narrowing the opening for the pelvis to slide through. 4kN load limiter This system was included in the A.I.S.S. design to reduce the belt loads on the chest while maintaining enough restraint to keep the occupant within the compartment during side and rollover crashes.

The upper anchorage of the torso belt on the seat back structure of current integrated seats is the greatest source of seat back bending moment and shear load on the seat structure. By limiting the torso belt loads on the integrated seat, it allows a weight reduction of the seat back structure and reduced floor pan shear while also reducing occupant injuries in frontal crashes. The load limiting retractor of the A.I.S.S. is designed to let the belt spool out of the retractor at a prescribed load of 4 kN. In the A.I.S.S. design, the retractor is fitted with a torsion bar to provide the load limiting feature.

Fig. 7: Analytical model of the Advanced Fig. 8: AISS prototype (front and side view) Integrated Safety Seat (A.I.S.S.)

Fig. 9: Frontal impact sled test set-up

In the frontal crash mode, the AISS pyrotechnic lap belt pretensioner and 4kN load-limiter contribute to a 26 percent reduction in occupant chest acceleration. Possibility of integration? At this stage, the pyrotechnic lab belt pretensioner and the 4kN load limiter work without any information from the type of passenger, and using feedbacks from sensors placed around the seat can obviously improve and adapt the pretensioner and load-limiter with the passenger current body height and weight, and also the seat position. The figure 10 below shows a passenger’s sensors system which is implemented to improve frontal collisions by adapting the airbags inflation. Ultrasonic sensors detect the passenger’s body height and position on the seat, and if combined with the weight sensors the corpulence of the occupant can be estimated. Then in function of the position of the person the smart airbag inflator adjust the outgoing airbag.

Pyrotechnic lap belt pretensioner

4kN load limiter

Fig. 10: Example of a passenger’s sensors system used for adaptive airbags

Therefore, the pretensioner stroke and load-limiter force can become flexible and adaptable to the type of passenger present on the integrated seat and improve the occupants’ safety during frontal collisions. But these devices can also be integrated by the use of external information. An integrated system is already implemented by TRW for the pretensioner: Adaptive Restraints (TRW) One of the prime examples of active and passive safety integration already available on vehicles is TRW's Active Control Retractor (ACR) seat belt system. ACR uses signals from active safety systems such as electronic stability control or brake assist to sense a possible loss of lateral vehicle control or an emergency stop situation. Once a potentially dangerous situation is sensed, the active control retractor seatbelt rapidly removes slack to help better position the occupant for a possible accident. If the accident is avoided, the ACR will release after several seconds and return to normal seatbelt mode.

Fig. 11: TRW’s active control retractor Fig. 12: Dual stage inflators and self adapting airbag

o Rear Impact

Seat-integrated belt system In rear impact cases, having an integrated safety belt system can reduce considerably damages if crash and passenger information are correctly provided, e.g. systems described above. Using this device reduces seat back ramping and potential contact with rear seat occupants.

Dual linear recliners

This device results in uniform loading of the seat back and provides torsional resistance from seat back twist. Rear impact energy absorber

Using this absorber also minimized occupant rebound and ramping by adding structural elements that deform plastically in a controlled manner. The mechanical energy absorbing elements were added in series to both recliners on either side of the seat. Extended head restraint system

This system is fixed in position (i.e., not adjustable). This eliminated the possibility of the head restraint not being positioned correctly for the reduction of whiplash injuries in rear impacts.

Fig. 13: Rear impact simulation of the AISS Fig. 14: Analytical modelling of the dual linear recliners

and rear impact energy absorbers In the rear impact mode, the AISS dual linear recliners, rear impact energy absorber and extended head restraint system contribute to reduce the occupant head, neck, and chest injury numbers. Possibility of integration? The dual linear recliners, rear impact energy absorber and extended head restraint system are impossible to integrate because they are irreversible passive devices using only mechanical systems without any actuators able to control the reaction during a crash situation. The Seat-integrated belt system uses the same information for the potential to be improved than the frontal collision systems:

Passenger’s information system Adaptive Restraints system from TRW

Extended head restraint system

Dual linear recliners

o Side Impact Two side impact countermeasures proposed for the AISS design were independently evaluated through analytical simulations. The countermeasures included: an Inflatable Tubular Cushion (ITC), and a combination head/thorax side impact air bag system.

Fig. 15: Side impact simulation set-up

Inflatable Tubular Cushion (ITC) The ITC system is a seat-mounted tubular bladder that is designed to reduce lateral loads on the occupant and prevent occupant ejection during a side impact collision. The ITC is an inflated tube which is anchored on the outboard side of the seat at two end points (toward the front of the seat pan and the top of the seat back). When deployed, the ITC expands and shortens at the same time. Due to the unique properties of the structural materials and the anchored end points, tension is introduced into the system as the bag inflates. The advantage of the ITC is that it eliminates the need for a reaction surface and consequentially creates a self-supporting inflated unit.

Fig. 16: Inflatable Tubular Cushion (ITC) side impact countermeasure and simulation set-up

Head/thorax side impact air bag system The combination head/thorax side impact air bag system is mounted on the outboard side of the seat frame. The seat trim has a special seam at the air bag location that splits open from the inflation pressure and allows the air bag to deploy into the vehicle interior. The combination head/thorax side impact air bag has two inflation chambers separated by a vented partition wall.

The head/thorax side impact air bag system is designed to protect the occupant by filling the airspace between the intruding door and the occupant as early as possible in the crash event. Upon activation, the thorax chamber is filled directly by the inflator within the first 20 msec. The head chamber is subsequently filled as gas is passed through the vent holes in the chamber partition wall.

Fig. 17: Combination head/thorax side impact air bag system countermeasure and simulation set-up

The combination head/thorax side impact air bag system model was found to provide improved occupant protection due to its ability to cover both head and thorax regions and provided a softer reaction surface for the occupant. Upper and lower ribs Thoracic Trauma Index (TTI) were reduced 22.1 percent and 14.8 percent, respectively in the side impact simulations. Possibility of integration? In that case a possible improvement can be done if the “normal” airbag system becomes an “adaptive” airbag system. These adaptive systems have already been proved in the frontal airbags located on the dashboard. By using all the information about the occupant, it would be possible to adapt the lateral airbags volume and density (e.g. passengers’ sensors system described above in frontal collisions). Other possible systems can be the use of side impact sensors or smart cameras to detect the exact lateral impact position and the direction of the incoming vehicle ahead the crash. Once these parameters known, smart inflators can, again, adapt the airbag deployment according to the crash situation.

o Rollover Seat belts are currently the most significant restraint for occupants in rollover crashes because they help prevent occupant ejection from the vehicle. Seat-integrated belt system The AISS incorporates a seat integrated belt system which improves occupant belt fit and couples the occupant to the seat. The torso belt was also designed to limit belt system loads to 4 KN (to optimize frontal impact protection) while sustaining loads capable of retaining the occupant within the compartment during rollover crashes. A buckle pretensioner was incorporated in the AISS to take-up slack in the belt system and reduce occupant excursion toward the roof in a rollover event.

Extended head restraint system The AISS was also designed with an 815 mm tall head restraint system to reduce structural intrusion from roof crush. The head restraint design provides a minimal back set between the occupant’s head and the head restraint.

Fig. 28: The deformable phase of the rollover simulation

The simulations predicted that the AISS extended head restraint prevented larger intrusion into the occupant compartment during roof crush and reduced occupant injury. The AISS pyrotechnic lap belt pretensioner and seat-integrated belt system also provide benefit in restraining the occupant and minimizing roof crush in the rollover simulations. Possibility of integration? As a passive device, the seat belt system does not react prior to the crash. If the TRW's Active Control Retractor (ACR) seat belt system is implemented instead and if it is combined with a dynamic active system (e.g. TRW’s Rollover Prevention and Mitigation system), an integrated safety system can come up and improve safety ahead the rollover situation by rapidly removing slack and better position the driver or the front passenger.

b. Dashboard Real world crash and biomechanics Real world crash investigations show that the protection of lower limbs of a motor car driver in frontal impact is still a major problem. Knees can hit rigid components behind the dashboard or the steering column (and risk some lesions like tibia or patella fracture) and the restraint systems available today still do not prevent the sub-margining effect. In Europe, the majority of occupant injuries are caused by frontal crashes. The frontal crash is responsible for 69% of serious injured people seen in France [10].

Fig. 19: Distribution of injuries according to the part of the body

In frontal crash, the injuries are more frequently inflicted to the head, the chest and lower limbs. In the U.K., 40% of injured occupants in a frontal crash present some lower limbs injuries (2000 study of Birmingham Accident Research Center). [11] Until now, the improvement of safety in a frontal crash has been focused on the head, neck and chest. The lower limbs injuries are not lethal but are often the cause of long disablement [12] and high cost for the society (21.5 Md $ a year in the USA). [13] The knee is one of the more frequently injured parts of lower limbs with femur and patella fracture [13]. In the UK, femur and patella fractures represent 34% of lower limbs injuries [14].

Fig. 20: Patella fractures Fig. 21: Femur fractures

The patella fractures are the result of a direct impact of the knee on the dashboard. [5] Some real crash studies are showing that the risk is not really due to intrusion but rather to the internal structure of the dashboard and its very stiff points [15].

The femur fractures are the result of a direct impact of the knee and the dashboard. Unlike the patella, the risk is essentially due to intrusion (more than 150mm for the L.A.B.)[15].

Injuries below the knee are essentially due to intrusion (specially the floor) and the combination of knee locking in the dashboard and floor intrusion [15]. The load limit for the femur is actually estimated at 6 KN. Biomechanics studies are showing that for the same load, we can see a reduction of 65% of patella fractures and 14% of femur fractures if the knee is impacted by padding and not by a rigid wall. The padding increases the surface of contact and improves the load distribution [13]. Possible reduction of lower limbs injuries The reduction of knee, femur, tibia and ankle injuries is possible by reducing the intrusion and putting a padding between the knee and the dashboard to:

absorb kinetic energy of impact avoid contact between knees and rigid parts of dashboard and steering column. have a good load distribution which depends on the shape of the surface of contact.

Current market for energy absorber of knee impact As explained before; during a frontal crash event, front seat occupants will be projected forward generally striking the knee and lower leg into the lower half of the instrument panel. The inertia of the occupant should be slowed by absorbing energy without causing the reaction load to exceed limits that would permanently injure the occupant. These limits are quantified in federal motor vehicle safety standards legislated by the government under FMVSS 208. In order to meet these standards, most designers include a member in the underlying structure of the instrument panel to deform in a pre-engineered manner. These members are most commonly stamped metal brackets. This produces a structural system that is heavy, and once attachment features and other design considerations are incorporated, often lead to an expensive solution. An alternative approach is to use the efficiency of highly ductile engineering thermoplastics in a lightweight economical design. This component is then attached to a rigid structural beam, and a knee bolster is attached to the rear face as shown in figure 22. During knee impact, this member will deform to absorb energy in a pre-engineered manner.

Fig. 22: Assembly Layout This design produces a very efficient energy absorbing system that meets the performance criteria of OEMs today. The resulting design produces a very low mass system using a combination of geometric crush zones with engineering thermoplastic (ETP) material advantages to achieve a cost-effective way to meet occupant protection requirements.

Fig. 23 Comparison of geometry

Active knee protection: Pyrotechnic Knee Bolster

The design of the PKB allows to avoid the contact of the knees on the rigid parts and to absorb a part of the kinetic energy of the occupant of the car. Its adjustment, according to the other restraint systems like the seat belt, the seat and the driver airbag gives to the car driver a high level of safety. Today, lots of cars include a knee protection device. Knee bolsters included in the dashboard or steering column are made of steel, plastic or foam. The goal of these knee bolsters is to absorb kinetic energy of impact and to avoid contact between knees and rigid parts of dashboard and steering column. Some style requirements and the preservation of comfort by a minimum clearance room between the legs and dashboard are not really good for the safety. The more the clearance room between the legs and dashboard is important, the more the legs of occupant are increasing their speed and kinetic energy before impact.

It has seen that the clearance room between the legs and dashboard must be as small as possible, so the solution is to move a padding from the inside of the dashboard to a position close to the knees only in the event of a frontal crash. To be efficient, the padding must be at the right position in front of the knees before the impact. To obtain this speed in the deployment, a pyrotechnic activator can be used.

Fig. 24: Before and after deployment

The PKB can improve the car driver safety for different reasons:

Important reduction of sub-margining risk Reduction of pelvis acceleration Important reduction of chest acceleration Optimization of kinetic energy dissipated by lower legs.

The PKB can avoid contact between knees and rigid parts of dashboard and steering column. Another interesting point is a possible improvement of safety in the lumbar region.

Discussion

The cockpit module is one of the most challenging vehicle systems due both to the complexity of its design and its role in maintaining passenger safety in the event of a crash. Compared with what is currently considered state-of-the art in cockpit designs - the next-generation concepts will integrate the cross-car beam and Instrument Panel carrier functions with the instrument panel and the firewall and it will do so in just 2 parts. A separate cross-car beam will no longer be needed. This will free up significant mass and package space in the vehicle, while still meeting global safety standards. It will also offer the flexibility to customize the vehicle interior to meet each OEM’s signature look and feel.

The knee protection system can be improved by using the data from the pre-crash sensors. The knee padding can be moved closer to the driver and passenger before crash to improve the safeness. Also similar activators can be used inside the doors to keep the driver and the passenger in best position before collision.

c. Airbags

Airbags are a more recent addition to the armoury against road trauma. Most commonly, these are located in the centre of the steering wheel and above the glove box on the passenger side. They are designed to activate almost instantaneously on impact to form a cushion as the head and chest of the driver or passenger flex forward.

An airbag is designed to be fully inflated by the time the occupant’s head makes contact with it. Anything else would be dangerous: a collision between a head, moving at high velocity in one direction, and the bag, moving at a similar speed in the other, could be fatal.

Siemens VDO is developing a state-of-the-art combination of electronics and sensors for airbag deployment. The demonstrated system uses a complex optical arrangement to detect the distance between passenger and instrument panel. The "intelligent" system was developed by company engineers to overcome the position-detection shortcomings of conventional video-camera technology that produces only a 2-D image.

The company's new system monitors the passenger side using a 3-D camera that signals the occupant's position to the airbag control unit. When a collision is detected, the improved information is used to deploy the airbag accordingly. Company engineers say that extensive testing of the system, using a camera in the passenger-side roof lining, has proven to be reliable in determining the occupant's precise position in the seat. The method already is in the final development stages for production.

Fig. 25 Siemens VDO's 3-D sensing system can determine the distance between an occupant's head and the instrument panel and alter airbag deployment accordingly

Meanwhile, Siemens VDO engineers continue work on other advanced methods of image recording and processing. At the IAA, the company unveiled a running-time-based method of detection it is developing with the central research division of Siemens AG. This method employs a laser to transmit flashes of light to be reflected by an object's surface. Position is calculated by the time taken for the light to travel to the receiver's shutter, which opens for just a few nanoseconds as the light enters. To compensate for differing material and colour reflectivity, the shutter is opened a second time when the complete light pulse has already entered the receiver. Software then calculates a 3-D image from the measured light intensities. This image processing method provides a highly reliable distinction between a person and an object on the passenger seat as well as a precisely determined head position.

The 3-D camera technology is part of a Siemens VDO integrated safety system incorporating a mat-based seat-occupancy detection system. It offers automakers an effective means of complying with the more stringent requirements of future U.S. legislation.

Discussion

By using the data from exterior warning sensors (pre-crash), airbags can be explode step by step. This provides less explosion speed that lowers the impact energy between the airbag and the head of the driver (or passenger). And also using the body position sensors, the airbags can be exploding in different angles. The development of systems to provide early warning of potential accident situations will remain one of the biggest challenges for road safety in the years to come. With the growing precision and predictive accuracy of the sensor technology in automobiles, pre-safe systems will be increasingly capable of directly identifying an impending collision. This makes it possible to optimize the design of non reversible safety systems. Then, for example, the airbags can be activated so that they inflate more slowly and thus cause less discomfort to the occupants.

As the idea of integrating subsystems to make an overall system, Mercedes introduced a “safe cabin preparation concept” called pre-safe and put on the market. Pre safe is a preventive protection system that activates the different systems for fixing occupants in place and positioning them in advance of a collision by analyzing the driving dynamics or the driver’s braking.

For example if emergency braking occurs prior to a collision, the occupants tend to be pushed forwards which gives extra slack to the seatbelt. The Pre Safe system tries to minimize this forward displacement with the use of reversible emergency tensioning retractors to couple the occupants to the deceleration of the vehicle and prepare occupants for a crash. Also, if the one of the front seats is in an unfavourable position for a collision Pre Safe changes this automatically in to a safe position

The next step is called “Advanced Pre Safe” and it works with an algorithm which identifies objects and impending collisions, provides information on the vehicle’s immediate surroundings in the event of danger using linked-up smart close-range radar systems to monitor a vehicle’s surroundings, and thereby helps to activate safety functions.

A version of Advanced Pre Safe currently installed in a test vehicle makes use of several radar sensors. These are fitted behind the front bumper and monitor the area immediately in front of the vehicle. The sensors are based on the very latest high-tech radar technology featuring exceptional properties developed in a project led by the Mercedes-Benz development department Driver Assistance Systems and Night View and involving the participation of the Environment Sensor Technology research department.

A project team of research and development engineers under the leadership of the Passive Safety unit has now linked up the individual radar systems in a network and developed a special algorithm to process the radar signals. This generates a large virtual radar beam that provides rapid and unequivocal information on whether, for example, the vehicle will collide with, or just miss, an obstacle. Advanced Pre Safe divides the road ahead into a virtual grid, and the sensors are then able to measure the distance to objects within their sphere in a matter of milliseconds. As a result, the onboard computer, which is equipped with a real-time operating system, can identify an object on the road within a fraction of a second so that, if necessary, active and passive safety systems can be rapidly activated.

Advanced Pre Safe, Pre Safe, and the various active and passive safety systems are all elements within an integrated seven-step safety concept rigorously pursued by research and development engineers at DaimlerChrysler. Here, the fundamental principle is always the same: Accidents should be avoided whenever possible- and when unavoidable, they should be identified as early as possible so that their impact can be diminished.

3. Integrated safety - Exterior

a. Active pedestrian protection Pedestrians are a high-risk group in vehicle impacts and in Europe they account for around 20% of all traffic fatalities: more than 6000 people are fatally injured annually. These numbers varies around the world from 14 to 47%. The figure below shows the sequence of a pedestrian contact with a vehicle for a typical pedestrian accident. It is valid in average if the vehicle speed is 40 kph and the person is an adult.

Fig. 26: pedestrian collision time-sequence at 40 kph

The majority of pedestrian fatalities are due to head impacts and today two passive safety systems are used to reduce them: active hoods and A-pillar airbags.

o Active hood This safety system aims to reduce the severity of head-to-bonnets impacts by offering space for deformation during the impact. A part of the energy can be absorbed by structures of the involved vehicle and thus injuries are minimized. When a vehicle hits a pedestrian, the rear end of the hood is lifted of around 100mm: a space for deformation is created between the hood and the engine bay. It also prevents the head from hitting the scuttle. Reduction of head injury criteria is higher than 60% in most cases [16].

o A-pillar airbags In some cases, for example when vehicle speed is higher than 50 kph, the head of the pedestrian reaches the windscreen or the A-pillars. A-pillar airbags are designed to offer head protection for a secondary impact, when the pedestrian is thrown over the hood toward the windshield. The airbags deploy in the time it takes the pedestrian to travel across the hood area toward the windshield - about 100 milliseconds. When fully inflated, some of A-pillar airbag systems cover the full width of the vehicle along the windshield base, from A-pillar to A-pillar; the others just cover A-pillars. In fact, most pedestrians do not impact right in the middle of the car front but impact with an offset. The airbags stay inflated for a few seconds, in contrast to typical interior airbags that can remain inflated for less than 100 milliseconds.

Fig. 27: Test with a combined system at 40 kph: active hood + A-pillar airbags

These two systems are currently limited by the pedestrian recognition. In fact it is important to avoid unwanted deployments when the vehicle hits a pole for example. It can induce problems such as intrusion of the hood (in case of front crash) or visibility obstruction with A-pillar airbags. The major problem is to distinguish pedestrian from poles or garbage cans. Current systems use several kinds of sensors: acceleration sensors, pressure sensors, knock sensors or piezoelectric sensors. All these systems detect legs by using crash information: for example acceleration sensors measure the velocity change to evaluate the stiffness of the impacting object [16]. Information provided are supplied with speed information to decide if systems must be deployed or not. Improving by using sensors from active safety systems All these information are collected after the first impact and then it reduces the available time for systems deployment. By using remote sensors that sense the pedestrian before the crash we could improve these systems. Several remote sensors types can be used [17]:

- video sensor: with 2 cameras a 3 dimensional object information can be calculated by triangulation. With a wide field-of-view, pedestrians can be recognised much before the crash (around 50 meters with cameras, which is equals to 3.6 seconds at 50 kph). This type of sensor is used in Adaptive Cruise Control systems and using it in pedestrian recognition does not need lots of hardware modifications. Nevertheless new software analysing road scenery has to be implemented. Pedestrian recognition can be achieved by detecting their movements.

- ultrasonic sensor system can be used for pedestrian recognition too but for much shorter

distances (less than 3 meters). Ultrasonic sensors equip some cars for parking aids. However some changes are necessary in the kind of measurement and signal processing.

- long range radar systems are also possible for long distances (higher than 150 meters). However these sensors are not already in use in production and introducing them only for pedestrian recognition seems to be difficult.

- infrared sensors: it is under research, especially in Siemens VDO [18]. It will allow pedestrian detection during night time.

All these sensors allow much more time for pedestrian protection systems deployment and better accuracy in terms of recognition of pedestrians and poles. Moreover these sensors can localise pedestrian position and then deploy only one A-pillar airbag for example if the impact occurs on one side. In fact most pedestrian do not impact right in the middle of the car front but with an offset. These sensor systems can also recognise a child from an adult and then deduce if it is necessary to lift the hood or not. All these improvements lead also to reduce inappropriate triggering: in case of offset impact it is useless to deploy A-pillar airbags at each side. We also can think about a communication with pedestrian integrated safety systems and Adaptive Cruise Control systems for example: if a pedestrian is recognised in the way of the car, brakes can be activated to reduce the speed impact. Pre-crash sensing allows finally some others new system for pedestrian safety such as over-the-hood airbag, which deploys from just above the bumper. Ford Motor Company's Pedestrian Safety is currently working on it.

Fig. 28: Experimental reproduction of a side pedestrian impact with an over-the-hood airbag for controlling collision

behaviour [19] Limitations All these improvements of current pedestrian protection systems can reduce the number pedestrian killed each year by offering an appropriate protection for pedestrians. Moreover inappropriate triggering can be avoided as explained before. However some specific problems are still under research. About image processing for example, looking at a scene taken by a video camera mounted on a vehicle, it appears that main changes are due to vehicle global motion, while minor changes are rather related to other moving objects such as cars, bicycles or pedestrians. Researchers are currently working on a technique called “compensation technique” which consists in estimating the camera induced 2D motion field and use it to align two successive images. So regions with secondary motions will be badly corrected and thus detectable. For such kind of reason and according to press announcements of several car manufacturers and suppliers, video-based safety applications will be introduced to the market within the next five years [20].

b. Adaptive structures Frontal collisions represent the majority of real world crashes involving occupants with fatal or serious injuries. Improvements can be made by using front structures which collapse if a crash happens. However these traditional passive front-end structures are limited by their fixed characteristics. NCAP tests can be “easily” fulfil by these solutions by it is obvious that reality is more complex and each crash is a particular case. These varying crash conditions lead to a new type of structure, called “adaptive structures”. These structures can change according to crash type and severity and then offer a hope of further reduction in injuries. They use different type of dampers to have controllable yield characteristics: hydraulic [21], damper with magneto-rheological fluid, damper with solenoid valve [22].

Fig. 29: Crash damper with solenoid valve (Siemens)

These devices are mounted at longitudinal members’ tips such as the figure below:

Fig. 30: Front end arrangement

Adaptive structures require pre crash information. In fact position and speed of impact must be evaluated a few milliseconds before the crash in order to determine how and where the structure must be changed. Thus sensor systems such as described previously for pedestrian recognition are needed. However in this case the data processing software must be adapted to recognize vehicles, humans or others obstacles. Adaptive structures are currently under research, and will probably introduce at the same time as the integrated safety systems for pedestrians described before. Discussion According to some research works, adaptive structures are efficient in terms of safety and reduce injury risk about 10% for the driver and 35% for pedestrian. However these experiments do not take in account the “recognition part”: obstacle properties and position are known from the beginning of the test. Tests on obstacle recognition have not been carried out yet. Determination of obstacle properties (for example stiffness) seems to be quite difficult to evaluate today and this is one of the key-point of introduction of adaptive structures.

4. Dynamic integrated safety systems The stability of terrestrial vehicles is determined by the combined functions of the vehicles steering, braking, traction, and suspension subsystems. Traditionally, these all-mechanical subsystems have been designed and developed by different suppliers in accordance with specifications from vehicle manufacturers. As a result, optimizing vehicle stability has been a difficult coordination issue. The advent of electronic controls has greatly advanced the ability to control vehicle stability but has also complicated optimization issues. New sensors, such as vision or radar, can be added to enhance vehicle control and safety. The evolution toward integrated vehicle controls is the result of a long series of developments in automotive electronics. As the reliability of electronics in automotive environments has improved and the cost of electronics decreased, more and more of the individual control functions have transitioned from mechanical systems to electronic systems. Equally important has been the development of vehicle networks and protocols that enable the sharing of sensor and control signals among the various vehicle subsystems. Together, these developments are enabling the emerging technology of integrated vehicle control. [23]

Fig. 31: Development of integrated vehicle control systems [23]

a. Active steering. During critical driving manoeuvres, vehicle control system (VCS) improves vehicle stability by braking a single wheel. As a result, the driver senses a torque disturbance at the steering wheel and may react by undesired steering inputs. The combination of VSC and active steer can solve this problem by applying an additional corrective torque to the steering system. The braking torque introduced by the VSC system reduces its amplitude. The additional compensation torque

generated by the active steering system eliminates this oscillation completely. Furthermore the severity of steering manoeuvres, as seen in the steering assist torque, is materially decreased by addition of the active steering correction torque, keeping the car in the lane without driver effort, is one of the aims of the active steering system. A similar system is currently in use by BMW but nowadays the system only helps to keep the vehicle in a strait line avoiding constant steering wheel corrections on windy days for example [24].

Fig. 32: Active front steering technology

As a next step, the system becomes an active lane keeping assistant, combining the active steering with the lane keeping system. The system measures the vehicle position relative to the lane, but offers active support in keeping the vehicle to the lane. However, the driver always retains the driving initiative, meaning that although he can feel the recommended steering reaction as a gentle movement of the steering wheel, his own decision takes priority at all times.

b. ABS The Anti-lock Braking System, or ABS, is a system which uses electronic controls to maintain wheel rotation during braking. Through that, it is possible to achieve maximum vehicle control with near optimal braking compared to non-ABS cars which suffer from locking wheels during hard braking. The ABS system thereby increases vehicle stability, especially when tire/roadway friction is below average or varied (for instance when the road surface is wet or icy) and generally reduces the minimum stopping distance [25]. The next stage in ABS development, involving the use of additional brake pressure sensors on all wheels, offers further potential for improvement. With this system, ABS will no longer be controlled indirectly on the basis of wheel speeds and slip but directly, using the brake pressure measured. This will make control operations even faster and more sensitive, leading to a further reduction in stopping distances combined with more stable handling. Another challenge is the evaluation of peak value of adhesion between the tyre and the road. It will allow higher performances. This parameter can be evaluated by different ways as using information provided by cars in front of or by braking a wheel to get the current value of adhesion [26].

c. Brake Assist System Crash research studies by Mercedes and Toyota, found that although drivers reacted quickly in critical situations, they did not apply the brakes with sufficient force. More than 90 percent of the drivers who participated in the tests either could not make up their minds to brake with full force until it was too late, or simply reacted incorrectly. During an emergency, driver’s foot comes off the throttle and on to the brake pedal faster than normal, which you then depress with more urgency than usual. This is registered by on-board sensors. Next, a brake pedal load-sensing switch and speed sensor determine if you have braked hard enough. If not, the system instantly determines how much extra braking force is required and increases the hydraulic pressure in the braking system. Then the brake actuator distributes the extra braking force to all four wheels that will decrease the stopping distance. If the driver successfully avoids the danger and removes or reduces the force on the pedal then the system will also reduce its involvement [27].

d. Lane Departure Warning. LDW will warn the driver if he or she is on the verge of inadvertently drifting out of the lane. Using a CMOS Camera and an image processing algorithm, this driver assistance system registers the course of the lane in relation to the vehicle. The system "sees", as it were, the course of the road and where the car is going. If the warning algorithm detects an imminent leaving of the current driving lane, the system warns the driver with haptic, kinestatic, or acoustical feedback. Possible warning alerts can be a trembling in the steering wheel, a vibrating seat or a virtual washboard sound

Infiniti’s LDW system uses a small camera mounted behind the rear view mirror to detect the lane marking on the road. A speed sensor measure vehicle speed. The camera’s image and vehicle speed are sent to the system’s microprocessor where this information is used to calculate both the distance between the vehicle and the lane markings and the rate of change of the lateral velocity relative to the lane marking. The microprocessor then compares this to its programming to determine if the vehicle is moving out of its lane. If from the distance and lateral velocity, it is determined that the vehicle is moving out of the lane the driver is alerted by indicator light on the instrument panel and by a buzzer-like warning. Fig. 33: Detection the lane marking on the road

The system will not work if the camera can't detect lane markers or if vehicle's speed is below 45 mph. The driver can turn off the system temporarily via a manual switch, but is automated activated again when the vehicle is restarted. Also, the system doesn’t provide a warning when the appropriate turn signal is used indicating an intended lane exchange [28].

e. Driver alertness monitoring The car industry is working on driver alertness monitoring systems. These systems are constantly "keeping an eye" on the driver's level of arousal and warn them whenever it falls below the necessary level to drive a car.

Some systems have proven in simulators that they were able to successfully detect driver fatigue. The first real-life systems will probably be introduced into the passenger car in the near future. There is a danger to this development though, because people might start to rely just a little bit too much on their warning system. Thinking that the system will wake them up anyway, they may take even more unnecessary and irresponsibly high risks with respect to tiredness than they already do now.

f. Stability control The Electronic Stability Program (ESP) maintains a car's stability under all circumstances. Sensors are built into the car to compare the actual direction the car is moving in with the direction indicated by the driver. If the input from the steering wheel differs from the desired direction, the system will correct this by applying the brakes on one or more wheels and/or by adjusting the engine couple. The ESP system receives the required information of the driver's intentions regarding steering and braking and thus on the vehicle's intended course through the steering and brake pressure sensors

Fig. 34: Components of the ESP system and triggered units

The wheel speed sensors determine the current speed driven by the vehicle. The turning movement of the vehicle around the vehicle vertical axis and the resulting lateral acceleration are measured by the lateral acceleration and yaw rate sensors. ESP becomes active whenever the course of the vehicle determined by this information deviates beyond a certain tolerance level from the course intended by the driver. This means, that as rule, first the engine drive torque is reduced. If this is not enough, brake pressure is generated at one wheel by the ESP hydraulics unit. The resulting, one sided braking torque causes a yaw moment which brings the vehicle back onto the course intended by the driver within the scope of physics

Fig. 35: Principle of Enhanced Understeering Control

In these situations of oversteering, ESP® intervenes by rapidly building up braking torque at the curve outside front wheel, thus stabilizing the vehicle. A similar braking intervention is also initiated in driving situations which threaten to bring the car into a roll-over situation, and has proven to be especially efficient for cars with a raised centre of gravity. In addition to the braking intervention in situations of oversteering or understeering, the drive torque of the engine is equally adjusted. In situations of understeering, during which the vehicle is pushed to the outside of the curve over its front wheels, ESP® builds up braking torque on the curve inside rear wheel. This practically pulls the vehicle back into the curve. Should the driver insist on tightening the radius of the curve even further, this will finally result in reducing the vehicle's speed [29]. Most drivers react to such emergency situations by turning the steering wheel even more into the curve, which, however, cannot yield any better driving dynamics. The error is equalized by the Bosch ESP® system with the function "Enhanced Understeering Control". The standard understeering intervention is overridden at all four wheels by a braking torque which reduces the vehicle speed to the extent that the curve radius requested by the driver can be achieved (see fig. 4). Normally, the vehicle would have shot off the road in such a situation, now accidents can be prevented.

Fig. 36: Results of Enhanced Understeering Control

g. Active rollover protection

Active Rollover Protection system (ARP Continental) can prevent rollover accidents from occurring. ARP is the next step in Electronic Stability Control Systems. It goes one step further than ESC (ESP) and monitors vehicle roll. When a driver enters a potential rollover situation, ARP detects it and works to help the driver keep the vehicle on all four wheels [30].

Fig. 37: After a rollover crash

ARP builds on ESC and its three chassis control systems already on the vehicle - ABS, Traction Control and Yaw Control. ARP adds another function, Vehicle Roll Sensing. Excessive lateral force, which is generated by driving too fast in a corner or turn, may result in a rollover because of

the high vehicle centre of gravity. ARP automatically responds whenever it detects an unstable condition leading to a potential rollover. ARP rapidly applies the brakes with a high burst of pressure to the appropriate wheels to interrupt the rollover before it occurs. ARP continuously analyses the driving situation and steering movements on the basis of signals from the ESP sensors, develops proactive emergency scenarios and implements them at lightning speed when necessary to prevent a rollover. For example, if ARP detects a rapid steering movement typical of an avoiding manoeuvre, the system reduces the force acting on the side of the vehicle and the lateral acceleration by braking the front wheel on the outside of the bend and slowing the vehicle. In this way, ARP counteracts critical body roll before it even starts, preventing dynamic wheel load changes and avoiding the risk of rollover [24].

The only difference between ARP and normal ESP is the extended software package; no additional hardware is needed. This makes ARP a good example of an integrated safety system. The system is already in use in several SUV’s on the market.

h. Collision avoidance systems Drivers have difficulties estimating the distance and speed of the car in front of them is a problem. Since those problems can lead to rear-end crashes, in-vehicle collision avoidance systems have been developed. The purpose of these systems is to warn the driver when a potentially dangerous situation occurs. The driver can then anticipate on the information he received from the system and most likely avoid an accident from happening. There are also collision avoidance systems available which have the option to automatically keep a certain distance from the car in front. Such a system does, of course,

i. Route guidance systems Right now, many different types of route guidance systems are being developed and, in some cases, already available in the stores. The purpose of these devices is to help the driver find his way in places where he has not been before, but also to help him find alternative routes in case of traffic congestion, delays, road maintenance and accidents. Since the onboard computer gives information about where to go, the driver does not have to check a map anymore and can concentrate on the driving task instead. Research has shown that, compared to the conventional paper map, the use of a route guidance system increases traffic safety.

j. Future systems

o ESP II: networked steering and brakes (Continental)

Today, brake systems are already being networked with intelligent air-sprung chassis with adaptive dampers. The next stage in development will be to include the steering system in the network. ESP II from Continental combines the brake control unit with ESAS (Electric Steer Assisted Steering). This Continental system is comparable to the Active steer system from BMW described before.

For parking, ESAS provides a very direct ratio, reducing the movement of the steering wheel needed to obtain full lock to a minimum. In fast cornering, this direct steering ratio means that the force needed on the steering wheel is much lower than with conventional systems. The car reacts more spontaneously, especially as ESP II encourages nimble cornering by initially leading the wheels into a bend further than would really be called for by steering wheel movement. For fast, straight driving, the steering is less direct, reducing the risk of swerving as a result of rapid

movement of the steering wheel. All these functions mean that ESP II makes for greater convenience and active driving pleasure.

With combined control intervention on the brakes, steering and engine, ESP II is also a highly effective dynamic handling control system. Targeted control of the front wheels, for example, makes the handling of the vehicle considerably more stable without any assistance from the driver. Oversteering tendencies can be counteracted by automatic steering corrections. As a result, automatic brake operation by ESP can be postponed and, if still required, can be gentler than would otherwise be the case. Optionally, the system can also control chassis systems, if the vehicle is equipped with air springs and/or adaptive dampers. The key advantage is that the vehicle's dynamic limits are no longer so narrowly defined and thus easier to control, while load changes are compensated for much more effectively and comfortably. Braking on roads with different grip on the two sides of the vehicle (µ-split braking) is a particularly striking example of the effectiveness of ESP II. On surfaces of this type, the brake forces developed are highly asymmetrical, with a pronounced tendency for the vehicle to turn towards the side which offers more grip. ESP II can effectively prevent the vehicle from running off course in this way by automatically correcting the steering as prescribed by an electronic control unit. All the driver has to do is carry on steering in the direction required. In addition, the fast and effective assistance provided by ESP II means that brake pressure at the wheels is built up with virtually no delay, allowing a modified brake pressure control system to be used for the rear axle. The result is a reduction of up to 15 percent in stopping distance compared with current ABS systems [31].

o Global Chassis Control (GCC): the active safety network (Continental)

ESP II controls yaw behaviour - the tendency of a vehicle to gyrate about its vertical axis - by combined control operations on the brakes, steering system and engine. ESP II can therefore be seen as a precursor of the Continental Global Chassis Control (GCC) project, which adopts a holistic approach to the overall system of "driver commands/external effects-vehicle-vehicle behaviour" with a view to obtaining further improvements in handling. The basic principle of GCC is as follows: Instead of using a large number of independent systems, each with its own sensors and vehicle status detection and control infrastructure, GCC is based on a centralized configuration. Semi-intelligent actuators - which only control the basic functions - are networked with the central GCC controller, which handles all management and coordination functions. Individual systems are limited to controlling basic dynamic handling functions such as the adaptation of steering ratio as a function of speed in the case of ESAS, or compensation for body roll as a function of lateral acceleration in the case of active stabilizers. The individual systems continuously exchange information with the GCC control unit, which issues the commands [24].

For example, in critical handling situations, the GCC controller calculates the yaw moment required for stabilization and then splits the correction needed into work packages for the individual actuators, taking into account their control capabilities, as well as the driving situation and input from the driver. GCC optimizes the reactions of the vehicle to the driver's commands by effectively controlling all the individual systems which can make a major contribution to performing these commands. Safety is the main priority, followed by ride quality.

o Active collision avoidance

Ever further ahead one can think of integrated systems actively avoiding accidents. This could mean an autonomous system monitoring the environment around the car which takes action by itself in ways of braking or actually steering away to avoid a collision should the driver not react in time. The technical tools to implement such a system are already available. The big challenge however is to make such a system fail safe and to design a good interaction with the driver so that the system will actually be accepted by customers as a safety feature. These issues will be discussed in the discussion part of this chapter.

k. Discussion of integrated dynamics systems With sensor and computing technology ever improving the possibilities to try to actively avoid accidents are getting bigger and bigger. One thing that will not change so fast however is the fact that all cars are driven by human beings of all ages, countries, etc. It is very important to know how these drivers will react to the systems that will be developed. It is quite possible that a new safety system will actually cause more accidents since drivers react in a wrong way to the actions of the system. Also there is the issue of reliability of a system. There are 2 main actions of an active/integrated safety system which are not desirable:

The system works when it is not supposed to: sensor information could be misread which can result in a system taking action when it is not called for and the driver is not expecting anything. This can be something as minor as giving a warning signal up to severe actions such as deploying airbags which can create extremely dangerous situations.

The system does not act when it is expected to: it is reasonable to assume that driver will

get used to the systems in their vehicle and will rely on them. A good example of this might be the sensor/warning system for overtaking vehicles. If such a system works well drivers will tend to rely on these systems and not use their conventional mirrors as carefully as without such a system. When the system the does fail to give a warning this can lead to a potentially dangerous situation.

Another issue that has to be considered is the impact of all active systems on the driving skills of the driver. With more and more systems in a vehicle, the everyday job of driving a car will become less and less demanding on a driver. It seems very probable that when such a driver is then placed in a conventional vehicle without active aids his/her skills will be less than those of drivers that normally drive in “conventional” vehicles, this again also can result in dangerous situations.

5. European programs working on integrated Safety Systems After the publication of the “White Paper on European Transport Policy for 2010”, several programs where established to fill up the necessities of reducing the human, social and financial costs terms. The European Commission declares the ambitious objective to reduce by 50% the number of fatal accidents on European roads by 2010. While conventional vehicle safety measures (e.g. seatbelts and airbags) have contributed significantly to the reduction of accidents in the last decades, their contribution is reaching its limits and currently further improvement is difficult to achieve at a reasonable cost. The development of new Advanced Driver Assistance Systems (e.g. collision avoidance-, line keeping aid- and vision enhancement systems) offers great potential for further improving road safety. In order to accelerate the research and development and deployment of these technologies, the eSafety initiative has been set up. This is a European joint public-industry initiative aimed at promoting the development and deployment of Intelligent Road Safety Systems, Integrated Safety Systems. [32]

a. AIDE - Adaptive Integrated Driver-vehicle InterfacE [33] The AIDE Integrated Project (IP) has been set up to address HMI (Human Machine Interface) issues within a general European joint effort towards the large-scale deployment of Intelligent Road Safety Systems and, ultimately, a significant reduction of road accidents. The general objective of the AIDE IP is to generate the knowledge and develop methodologies and human-machine interface technologies required for safe and efficient integration of ADAS, IVIS and nomad devices into the driving environment. The sub-objectives of AIDE are

To maximize the efficiency, and hence the safety benefits, of advanced driver assistance systems,

To minimize the level of workload and distraction imposed by in-vehicle information systems and nomad devices and

To enable the potential benefits of new in-vehicle technologies and nomad devices in terms of mobility and comfort.

b. PReVENT [34]

The Integrated Project PReVENT is a European automotive industry activity co-funded by the European Commission to contribute to road safety by developing and demonstrating preventive safety applications and technologies.

Preventive safety applications help drivers to avoid or mitigate an accident through the use of in-vehicle systems which sense the nature and significance of the danger, while taking the driver’s state into account.

The goal of Integrated Project PReVENT is to contribute to the:

Road safety goal of 50% fewer accidents by 2010 - as specified in the key action 2.3.1.10. eSafety for Road and Air Transport from the European Union.

Competitiveness of the European automotive industry European scientific knowledge community on road transport safety Congregation and cooperation of European and national organizations and their road

transport safety initiatives PReVENT consists of a number of subprojects in complementary function fields:

o Safe Speed and Safe Following These functions help drivers keep or choose a speed or inter-vehicle distance, allowing them to safely cope with the road situation they will meet in the following seconds. The approach is mostly autonomous.

Fig. 38: Saspence systems

o SAFELANE focuses on the following challenges:

• Fusion of camera-based lane detection system with digital map data (cooperation with PReVENT horizontal subproject MAPS&ADAS) and supplementary data from active sensors

• Model-based and adaptive decision component with situation analysis and determination, including precise vehicle trajectory calculation and self-assessment

• Active steering component for actively supporting the driver in avoiding unintended lane or road departure.

Fig. 39: Safeline principle

o Intersection Safety

INTERSAFE explores the accident prevention and mitigation potential of an integrated preventive safety system for intersections. The effectiveness of the safety system for higher-risk scenarios will be evaluated in a simulator environment as well as through demonstration of an application providing the driver with turning assistance and infrastructure status information.

Fig. 40: Vision at intersections

o Vulnerable Road Users and Collision Mitigation Collision mitigation and pre-crash protection systems focus on reduction of injuries and fatalities in case of unavoidable crashes (in particular during the last 2-3 seconds before the impact). Collision mitigation by braking significantly reduces kinetic energy of impact, thereby greatly reducing crash severity. The PReVENT APALACI and COMPOSE sub-projects address different complex and challenging aspects that have to be tackled in the field of Collision Mitigation and Vulnerable Road Users protection by following complementary approaches and focuses in a joint work plan.

c. Electronic Architecture and System Engineering for Integrated Safety Systems [35]

The road safety targets set by the European Commission Transport Policy can only be reached through an integrated approach to vehicle safety systems, i.e. the combination of active and passive safety systems over vehicle domains or networks.

From a technical point of view today’s safety systems are mostly stand alone systems with a limited degree of interdependency. These systems must be integrated - combined with upcoming enhanced telematics services - into a complete network of so-called Integrated Safety Systems.

For the realization of such Integrated Safety Systems, powerful and highly dependable in-vehicle electronic architecture and appropriate development support are necessary. These elements must be standardized to achieve an improvement in system quality with shorter development times and lower system costs.

The goal of EASIS is to enable the realization of integrated safety systems by defining a powerful and highly dependable in-vehicle electronic architecture and an appropriate development support. To achieve this a joint effort of a variety of major industrial players in the automotive field is necessary. They are

• Vehicle manufactures, • Automotive suppliers, • Tools and middleware suppliers.

The fourth group of partners in the project is leading European research institutes. They supply the consortium with the latest research results as well as the basic and fundamental know how to deal with upcoming conceptional designs and the long-term perspective.

Fig. 41: EASIS concept

6. Discussion As with most systems in the automotive industry their idea is not something novel, generally we see that systems appear when it is technically feasible to produce them. There are however a lot of factors that will influence what a system will look like and whether they will be used. It is very important to keep in mind that in the end a customer will decide to buy vehicle, interaction of different systems as well as added cost is therefore crucial. Furthermore the effect of implemented must be well considered and researched; How will they work in reality, what can go wrong, does the system actually add to the occupant and traffic’s safety? The following five issues influencing the introduction of new (integrated) safety systems will be discussed: added cost, legislation trends, functioning in daily use and HMI (Human Machine Interface).

o Added cost: Cars are sold on an extremely competitive market, although the public is becoming increasingly aware of the importance of vehicle safety that will not be the main motivation for most people to buy a vehicle. Besides design the overall price of a car will be extremely important. All added safety systems will add to the price while most customers will normally hardly notice anything of these systems. This is of particular importance for pedestrian protection systems, as these do not involve a direct benefit for the buyer and driver of a car. In fact no one believes that they will hit someone so they do not want to pay for these safety systems. Integrating different systems already present in a vehicle seems like the only cost effective way to go to keep a vehicle on the market competitively and still increase the amount of safety features.

o Legislation trends: Regulations for vehicle safety are constantly being upgraded; the bar is being put higher and higher. This clears the way to develop new systems since all manufacturers will have to fulfil all these regulations. In the coming years regulations will also come into action for pedestrian safety which is an issue that has come up strongly in the last years. Since it can be expected that regulations will continue to be stricter and stricter, integration of different systems must be the way to go to both comply with these rules and still have a competitive product. Luckily customers have become increasingly aware of the safety ratings of vehicles, mainly due to smart marketing of different brands; this will help new systems complying with future legislation easier to be accepted by customers.

o Functioning in daily use Systems introduced into vehicles are expected to work fail-safe through out the life of the vehicle. Small errors like a cruise control that does no longer work are maybe acceptable; problems with more critical systems however can be extremely dangerous. This mainly applies to the non-reversible systems. Main examples of irreversible systems are: airbags, seat belt pretensioners, active hood… (in general all systems using pyrotechnic devices as starters). In an integrated system general malfunction or misinterpretation of different signals could result in the 2 following situations;

The system works when it is not supposed to: sensor information could be misread which can result in a system taking action when it is not called for and the driver is not expecting anything. This can be something as minor as giving a warning signal up to severe actions such as deploying airbags which can create extremely dangerous situations.

The system does not act when it is expected to: it is reasonable to assume that driver will

get used to the systems in their vehicle and will rely on them. A good example of this might

be the sensor/warning system for overtaking vehicles. If such a system works well drivers will tend to rely on these systems and not use their conventional mirrors as carefully as without such a system. When the system the does fail to give a warning this can lead to a potentially dangerous situation.

Extreme care will have to be put into the processing of all data and the computing of different actions to assure a fail safe operation of the system. This can also give rise to liability issues, although a system is fully functioning for the safety of the occupants, the actual behaviour of an occupant might actually make it so that there will be an accident whereas there would not have been one without the system. This of course applies both to the reversible as to the non-reversible systems. In parallel to that, another way could be the development of new reversible systems such as the TRW’s Active Control Retractor (ACR). This reversible pretensionner uses an electrical motor adapting the tension in pre-crash situations to the passenger’s type and releasing the tightening if the crash is avoided. Today the triggering time will be slower but the technology will certainly be improved in few years and reversible systems will reach the same efficiency than non-reversible.

o HMI (Human Machine Interface) With sensor and computing technology ever improving the possibilities to try to actively avoid accidents are getting bigger and bigger. One thing that will not change so fast however is the fact that all cars are driven by human beings of all ages, countries, etc. It is very important to know how these drivers will react to the systems that will be developed. It is quite possible that a new safety system will actually cause more accidents since drivers react in a wrong way to the actions of the system. All of the radio communication systems offer the driver much information about the road environment. But, the recent systems are becoming more complex due to the fusion of different technologies. This fusion produces a more autonomous vehicle, which can take decisions itself. As a consequence, one of the main concerns is how the driver will react to this amount of information The HMI will also play a big role in customer acceptance and therefore sales of vehicles featuring the discussed safety systems. Since the customer will in the end be the one paying for the system it is crucial that the customer can easily handle the systems and confides in them. Another issue that has to be considered is the impact of all active systems on the driving skills of the driver. With more and more systems in a vehicle, the everyday job of driving a car will become less and less demanding on a driver. It seems very probable that when such a driver is then placed in a conventional vehicle without active aids his/her skills will be less than those of drivers that normally drive in “conventional” vehicles, this again also can result in dangerous situations Others parameters are currently delaying the market introduction of these integrated safety devices. As an example how to use several sensors to provide a unique information? At the moment, sensors suppliers are collaborating to refine the way to make the sensors (video and radar) work together. To do so, they have defined a calibration procedure between the two sensor systems in order to enable a cooperative work and then to build a strategy for data fusion. The objective is to find a geometrical correspondence between the radar and the video coordinates systems. Then, a fusion strategy will be chosen that takes into account the results (precision and uncertainty, constraints) of the previous task. Therefore the functional blocks for low-level data fusion will be defined.

o Consumers acceptance User acceptance will play a critical role in how next generation safety vehicles will look and perform. Researches suggest that consumers are interested in advanced traveler information systems that provide accurate and timely information; are reliable, affordable, and easy to use; and improve personal safety and security. But the driving public is notoriously picky about what goes in

their vehicles. In the 1980s, consumers in the United States almost universally rejected voice-alert systems in the vehicle, including those reminding passengers to buckle their seat belts. But consumers are also growing more accustomed to interacting with machines, which have become an intractable feature of everyday life in banking, communications, and entertainment. From a market perspective, customization is an attractive feature, as exemplified by the thriving vehicle accessories market, which allows consumers to individualize "one size fits all" vehicles. Given the wide variety of information and technologies that could be placed in vehicles, it is not too improbable that in the future, drivers would be able to personalize the types of information provided by their vehicle. The ability to personalize would mean that the vehicle would know the driver's routine, recommend routes, and remember the context of those trips, such as ongoing construction on a much traveled exit ramp. In another fashion, an intelligent vehicle could allow the driver to customize how information is presented, in much the way that Microsoft or Apple allows a user to customize how he or she maneuvers through programs or the way an individual can touch a button in high-end luxury cars to position the seat, mirrors, and steering wheel for a particular driver. Paralleling the current discussions on air bags, however, are questions such as whether drivers would be able to disengage systems, particularly safety systems, they didn't like or found personally distracting. Although user acceptance has been discussed as a key issue for Intelligent Safety Systems, some questions are still waiting for answers:

Identifying how drivers react to an integrated, multi-function display that presents both collision and traveler information,

Determining if a distributed display approach (i.e., multiple displays) is preferred by drivers, Determining how drivers react to concurrent presentation of collision avoidance systems, Determining how visualization designs can help drivers selectively focus on the most urgent

information. According to develop the systems integration with human, at least two strategies can be developed. A first strategy is to specify the instruments’ functionality according to the preferences of the car drivers. This strategy is probably relatively easy to implement as it is based on current preferences and does not require any change in user preferences. However, this strategy may not be sufficiently effective, because car drivers might prefer the warning functionality, which still allows them to violate speed limits. Therefore, a second strategy may be followed specifying a functionality that maximizes the systems’ efficiency. As the current driver acceptance for this functionality is expected to be rather low, this strategy is less easy to implement. The successful implementation of this strategy probably requires an accompanying policy to influence the car drivers’ attitudes in order to increase intelligent warning systems acceptance. Future possibilities Since the quality of the different sensors keeps increasing the “electronic horizon” of a vehicle equipped with integrated systems can increase. With this there will be more time for reversible system to take action, this offers a great potential in further reducing casualties, occupants can be put in a better position, should the accident be averted, no harm in done and the system will continue to function normally. The main challenge here will be to accurately process the different sensor signals to make absolutely sure no wrong actions will be taken. Once this is taken care of the road is open for even more active systems like systems actively avoiding obstacles or autonomously bringing the vehicle to a stop. The introduction of these systems will for the biggest part not depends on the technical possibilities but more on the level of customer acceptance, legislation and liability issues, much study remains to be done in this area.

Conclusion

A wide range of both passive and active safety systems currently available and predicted for the future have been discussed. To keep increasing the use and range of the safety systems in a vehicle these will have to be fused together into an integrated safety system. An integrated safety system can offer the possibility of using the already available sensors to increase the amount of task for the system. Mainly this will result in pre sensing dangerous situations and reacting accordingly. There are however a lot of challenges facing the implementation of such a system. Apart from the added cost of an extended safety system matters such as customer acceptance and HMI have to be carefully researched. Also, the more autonomy a system gets, the more crucial it becomes that the system will always work as it is intended; a system failing or not functioning when it is supposed to cannot be accepted. Fusing data from different sensor to get accurate, reliable and uniform information is another big challenge. The processing of the data will also have to receive a lot of attention. If all these challenges can be overcome there is a great potential to make modern traffic a lot safer.

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