5th International Munich Chassis Symposium 2014

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Designing a good chassis is never a trivial task. The problems already start with the fundamental question: What makes a good chassis in first place? In fact, the engineering goals keep changing as more and more influencing factors come in and have to be considered. In the early years the main focus was on the primary function of a chassis, which is to offer the best possible ride and handling performance. The reason for this narrow view was that neither ride nor handling scored very high and therefore a good chassis meant a significant advantage in the marketplace. For upper market vehicles or for performance cars the chassis is still a differentiator, but in general the technical progress has led to performance levels that exceed the expectations of many customers.

Mit dem BMW 2er Active Tourer erweitert BMW sein Modellportfolio in ein weiteres Fahrzeugsegment. In der Premium-Kompaktklasse verbindet der neue BMW 2er Active Tourer Komfort und Raumfunktionalität mit der für BMW typischen Dynamik. Er verbindet kompakte Abmessungen mit Raumgefühl und ist damit ideal geeignet für die ständig wachsenden Mobilitätsansprüche im urbanen Umfeld.

Since the early eighties, significant progresses in terms of stability and safety have been observed in passenger cars. Nevertheless, driver impression of current vehicle is not always positive. The sense of unity with the vehicle is important for the driver to feel fun while driving. Enthusiastic drivers prefer cars of the good old days not only because of styling or scarcity reasons, but for the pleasant feeling at accelerating, steering and braking. They enjoy driving vehicles with straightforward commands in contrast to modern ones with their excellent dynamic and safety performance but partly decoupled commands.

The Porsche 918 Spyder is the blueprint for tomorrow’s sports cars with a hybrid powertrain and other trendsetting technologies. Due to this combination it achieves a great spread between highest performance and lowest fuel consumption. On the one hand the 918 Spyder offers to drive 16 – 31 kilometres purely electrically or a fuel consumption of 3.1 – 3.0 l/100 km1 in the NEFZ – cycle. On the other hand it enables a unique driving experience by generating 887 hp from a 4.6 litres naturally aspirated V8 engine and two electric motors. Those figures in collaboration with the chassis systems let the 918 Spyder set a new record for the fastest lap on the Nürburgring Nordschleife for seriesproduction vehicles with standard tyres of less than seven minutes.

The automotive industry is facing great global changes. With an increasing world population and a more concentrated human density in urban areas, the question of responsible resource employment has to be urgently answered by political authorities and societies. Furthermore, environmental problems and the awareness of climate change are leading to new cultural values and customer expectations in many global markets. Consequently the political regulations for CO2 fleet restrictions and import limitations are getting more important for the automotive industry. In order to keep up with these challenges, a new comprehensive concept of mobility is necessary to make the products of an automotive manufacturer future-proof. With the sub-brand BMW i, the BMW Group is facing these changes seriously and is offering a contemporary solution for mobility.

For the attempt to improve the lateral stability so that the driver’s steering corrections are decreased, the following target scenes are defined in considering this control method.

1. Driving on the road with lateral slope. It is required that the vehicle goes straight without driver’s constant compensation to the steering wheel.

2. Encountering disturbances such as crosswinds or road irregularities. It is required that the vehicle can keep the target path with little drivers’ steering correction.

The quality of steering systems and their application has significant impact on the overall assessment of handling performance. In some cases it is even possible to mask non-optimum handling characteristics with a good steering system. On the other hand a nice and smooth vehicle may be ruined by a bad steering application. The impact of steering systems and their application has increased with the introduction of vehiclespeed dependent assist forces. The biggest boost in challenges appeared with the introduction of Electric Power Steering (EPS) systems and their application process still offers a couple of challenges.

The conceptual layout of a damper is subject to many requirements related to vehicle ride, lateral dynamics, misuse, and acoustics. Conflicts of goals between these different disciplines often occur and may be caused by various reasons. In classical design, there are two major contributors. First, design work is typically done by considering only one damper characteristic that is iteratively improved in distinct development steps. Second, design objectives are considered one-by-one and not simultaneously. In order to avoid conflicts of goals and to find optimal solutions that satisfy all design requirements, a design method is proposed that relies on computing a solution space. A solution space defines a permissible range of damper characteristics on which the specified set of requirements is satisfied. It is constructed to be as large as possible in order to provide maximum flexibility for other requirements or tolerance to uncertainty in design work.

Excellent vehicle dynamics performance has strongly contributed to the appealing driving experience of Ford vehicles. This is achieved via application of advanced suspension concepts, high structural stiffnesses of body and chassis components and extensive tuning work on the vehicle proving grounds. One of the key challenges in vehicle engineering is to optimize vehicle driving comfort without degrading the steering and handling performance.

In this talk we will present the motivations and advantages of highly integrated platforms in the chassis sector. We will discuss a concept for such a platform based on the AUTOSAR architecture.

There are two visible trends that can be observed in the automotive industry that have a big impact on the steering system. The first is the development towards automated driving. Up to level 2 of the SAE Standard (see figure 1), the required steering functionality can be offered by a standard EPS system. However, from level 3 onwards where the driver can be taken out of the loop, the standard EPS system is not sufficient anymore. In that case, a full redundancy of the steering system is required to guarantee full functionality at all times. The second trend, which is not independent of the first one, is the development towards Steer by Wire (SbW) systems. It has always been clear that SbW would be the next logical step in the development of new steering systems. However, the technical challenges and the costs of such a system are quite high when weighed against the direct customer benefits. The trend towards automated driving however is a new driver for SbW systems. A redundant SbW system is the only solution to be able to develop complete new interior concepts and HMI’s for automated driving vehicles.

The automotive industry is facing the next major evolutionary step. New functions for highly automated driving are entering the vehicles. This is accompanied by increased E/E and mechatronic contents, leading to increased topological complexity. At the same time the system/component and development costs should remain stable and product quality should be further improved.

Dynamic Driving Simulators are becoming more and more popular in the automotive industry for developing equivalent-to-real full vehicle testing. They embed detailed in-SW or in-HW description of all the passive and active vehicle subsystems, for combined ride & handling maneuvers: professional drivers have access to an accurate reproduction of the real vehicle and, within a new revolutionary approach to vehicle engineering, they work with engineers to significantly influence the design of the ondev vehicle real prototype. Key factors for the effectiveness of a dynamic driving simulator are vehicle and road model accuracy, graphics / sound / vibration quality, realism of human interface, effective motion cueing and the ability to correlate parametric results between simulation and reality. Balancing all the factors is the real issue, and doing it properly within all the constraints of a simulated reality is one of the main challenge for the OEM and the simulator supplier. Ferrari and VI-grade have been and are working together to fine tune the new Ferrari driving simulator in order to minimize the on-platform vs. on-vehicle driver feeling difference and summarize in this presentation what the experience has been so far.

The technology of the driving simulator is being used more frequently in the development of commercial vehicles for the optimization of driving and steering behavior. It allows for important optimization steps in the field of chassis suspension and steering, as well as for the definition of consistent target criteria for handling, active safety and primary ride, which are specifically tailored to the different types of commercial vehicles. Examples show how the application of the driving simulator significantly increases the efficiency, helps minimizing design loops and thus reduces development time and cost.

allows the interactive evaluation of steering functions in the Stuttgart Driving Simulator. The focus of this method is the consistent representation of the correlation of steering input, steering wheel force feedback and perception of the vehicle motion by the driver. The objective is that even slight modifications of the design and calibration of the steering system and chassis should be experienced in driving simulator rides. This allows the evaluation of new designs of steering and suspension systems already in the advanced development phase and to identify variants with maximum customer’s benefit. Further research topics are automated driving functions, especially the safe transfer of vehicle lateral control from the driver to the automatic system and vice versa.

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Air spring systems are gaining more popularity in the automotive industry and with the ever growing demand for comfort these-days they are almost inevitable. Some significant advantages which they offer over conventional steel springs are appealing to commercial vehicles as well as to modern passenger vehicles in the luxury class. Current production air spring systems exist in combination with hydraulic shock absorbers (integrated or resolved). An alternative is to use the medium air not only as a spring but also as a damper: a so-called air spring damper.

Subjectively the impact of car body stiffening on the handling performance can be perceived. The impact of reinforcements of the vehicle body on the vehicle performance has been studied in the past (see [1], [2], [3] and [4]). These studies had a main focus on the objective observations on the level of body forces and body deformations.

on ride comfort. Therefore the differences between measurements of full car tests with the results from traditional 4-post test rigs and finally with the dynamic suspension test rig up to a frequency around 30 Hz are analysed. For this research a standardized driving surface and bump is used for the full car test. On the 4-post and dynamic suspension test rig the dynamic transmission behaviour is inspected with a sinus sweep with constant amplitude and frequency velocity and a vertical bump. The study shows that the results of all three measurement methods used for the subsystem suspension are comparable. Further a multi body simulation (mbs) is validated with the measurements. The results of the simulation are nearly the same compared to the real tested measurements. Furthermore this study investigates a method to analyse the maximum and minimum eigenfrequency of a suspension. Another eigenfrequency within the suspension is possible with a stiff damper stiffness and is affected by the wheel trajectory angle and the longitudinal elasticity of a suspension. This eigenfrequency can be affected by the damper position. Furthermore all three parameters influence each other. This reciprocal dependency is also investigated of accelerations on the chassis dome, wheel carrier and seat by driving over a bump. With this study it is possible to increase the spread of best-in-class handling performance and optimal ride comfort.

With the idea of designing new electric vehicles that reach high energy efficiencies by drastically reducing the curb weight, a completely new problem arises with respect to driving dynamics. The weight of everyday load has an increasing influence on the car’s mass and inertia properties as well as on the tire properties. Thus, vehicle dynamics and its parameters change with every trip. This work shows the consequences on passive behavior for different everyday load scenarios. An estimation algorithm is proposed that is able to determine the trip-individual parameters online and to provide vehicle dynamics controllers with adapted values.

This contribution investigates the sensor fusion of a three antenna GPS-system (position, velocity, yaw, pitch and roll angles) and an inertial measurement unit (IMU, angular velocities and accelerations) to get a three dimensional motion estimation of a vehicle. To handle the different delays of GPS measurements and the nonlinearities in the measured system a Sequential Enhanced Kalman Filter is used. Bias and gain errors of the IMU are estimated to allow a precise calibration of angular velocities and accelerations.

The stability of articulated vehicle combinations is an ongoing concern in the automotive community. When larger trailers are towed by ordinary passenger cars, they tend to exhibit lightly damped oscillations in the yaw plane, or “snaking,” at higher speeds [1, 2]. Above a critical speed, the entire vehicle-trailer combination becomes unstable and uncontrollable [1-4]. This critical speed can correspond to ordinary highway speeds, and is heavily influenced by factors in control of the vehicle owner, such as the centre of gravity location of the trailer and tyre inflation [1-4].

In the context of future electric vehicles, new requirements and restrictions, but also larger degrees of freedom, have been revealed for vehicle concepts. To meet the revised conditions, new approaches are necessary as well as a holistic view of the vehicle and its subsystems. Those revised conditions are for example the integration of new and additional functions into the chassis, the reduction of the unsprung mass or the maximization of the packaging space that can lead to a complete redesign of the automobile.

Nowadays the development of mechanical components is driven by ambitious targets. So engineers have to fulfill all technical requirements and have to reduce weight and cost of the mechanical components simultaneously. Beside this, the development time and costs have to be lowered in order to reach shorter product cycles and faster market innovations.

Over the last few years, Schaeffler has played its role in driving the replacement of hydraulic with electromechanical systems thanks to developing an electromechanical anti-roll system. The plan is for series production of this system to start in 2015. The benefits offered by the system are:

– Little or no tilting of the vehicle when cornering as a function of the present lateral acceleration

– More accurate steering behaviour, improved agility and stability

– Enhanced system dynamics compared to hydraulic systems

– Simple installation and easy maintenance

– Reduction in the number of field complaints by up to 30 % compared to hydraulic systems

– Installation in hybrid vehicles possible

– Reduction in fuel consumption of up to 0.3 litres compared to hydraulic anti-roll systems, and

– Weight neutral compared to hydraulic systems

Current HPS consists of gear, pump, tank, piping and oil cooler. On the other hand, our Hybrid EPS consists of gear, piping and a special power pack which integrates pump, tank, ECU and motor. Our system is basically the same one of the hydraulic standard like PS system as shown here. Our system, therefore, can be installed with minimum modification of engine compartment.(Fig.1)Similar system so called Hydarulic Electric Power Steering (here after called HEPS) use by several OEMs consists of same as our system. But it uses exactly hydraulic PS gear. Only difference between hydraulic PS and HEPS is how to drive PS pump. HPS uses engine to drive pump. HEPS uses motor to drive pump. Both of them are purely HPS. Our system uses gear with torque sensor. So structure is similar between our Hybrid system and HEPS but clearly different system.

The Institute for Automotive Engineering at RWTH Aachen University (ika), is currently developing, constructing, and implementing the research vehicle SpeedE as an open research and innovation platform for research and industry. On research focus of the SpeedE concept, amongst others, is the innovative front suspension. Not only is the front axle’s steer-by-wire system able to steer each wheel individually, but it is also able to achieve steering angles of up to 90°. These requirements lead to an unconventional setup of the axle replacing the tie rod and the rack and pinion steering gear of a double wishbone suspension by two steering actuators consisting of an electric motor and a strain wave reduction gear located at the outer kinematic hardpoint of the upper control arm and mounted to the wishbone through a cardan joint.

Cornering with more dynamism and agility, improved driving stability and safety at high speeds, as well as mastering parking and turning manoeuvres more easily: These are the benefits offered by the rear axle kinematics called Active Kinematics Control (AKC) from ZF. The system allows the rear axle of passenger cars to provide active steering assistance via electromechanic wheel alignment – and can be adapted in two variants for different axle designs in a modular manner.

This work presents distributed architecture for vehicle control systems, especially for EPS. Main purpose is to anticipate future requirements on vehicle control systems. This architecture makes system fail operational using PERICAN. In addition, protection against security threats is also taken into account.

It has passed almost 2.5 years since ISO26262 international standard was issued. As for the microcontroller, still lots of interpretation for the actual implementation of the architecture and its verification method are in discussion and sometimes there are many confusion. It is said one reason for this might be abstract way of writing for the ISO26262. Even if ISO26262_Part10 exists as guideline, it is not enough.

The increasing pressure to reduce cost and minimize developing time in the automobile industry, together with constantly growing number of vehicle variants, makes the employment of Hardware in the Loop (HiL) technologies for testing Electronic Control Units (ECU) mandatory. They allow the meticulous application and controlling of system desired characteristics in a very early phase. The steering, which acts as interface between the driver and his vehicle, plays a key role in the vehicle performance since influences the handling and the drive feeling massively. Similar to the Electronic Stability Control (ESC) the Electric Power Steering (EPS) is today standard equipment in each vehicle. However, the EPS is working permanently instead of only in special driving situation like ESC.

Unlike conventional steering systems, there is no mechanical linkage between the steering wheel and the wheels in steer-by-wire (SbW) vehicles. The steering angle and the steering torque are instead realised through separate actuators: a wheel actuator and a hand wheel actuator. This paper focuses on the steering feel generation in SbW vehicles and is devoted to the related design of an intelligent mechatronic system, consisting of the hand wheel actuator as hardware unit and the computation of the desired steering torque as control algorithm. The paper finds another application field in driving simulators (DSs), where the task of the steering feel generation also needs to be completed.

Since motorized vehicles are on the road, they all have an element to steer the vehicle. At the beginning it was a pure mechanical connection steering wheel – steering column – steering gear – front axle – front wheel. In the 50’s of last century the first systems of steering assistance were developed and introduced into the market. A hydraulic system supported the driver to turn the steering wheel with lower torque, so especially steering at low speed became more convenient. To reduce the fuel consumption of the vehicles the hydraulic system was replaced by electrical systems in the 90’s. Beside torque assistance, almost 10 years ago angle assistance was introduced to steering systems.

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Die Betriebsbremse steht für den Vorgang, die kinetische Energie des Fahrzeugs zu verringern. Da diese Energie durch Antriebsleistung erst aufgebaut wurde, ist die Rekuperation der kinetischen Energie die naheliegende Lösung zur Wandlung der kinetischen Energie. Im Zuge der Elektrifizierung des Fahrzeugantriebs sind Möglichkeiten zur Rekuperation inhärent geboten. Das Potential wird an Beispielen erörtert, die zeigen, dass dieser Verzögerungsmechanismus nur in speziellen Fällen ausreichend für den Ersatz von Dissipationswandlern wäre, nämlich an Hinterachsen in Fahrzeugen mit insgesamt geringer maximaler kinetischer Energie, also kleiner Masse und eher niedriger Höchstgeschwindigkeit. Da aber die Rekuperation trotzdem einen großen Teil der Verzögerungsleistung im Fahrbetrieb aufnehmen kann, werden die Bremsen immer mehr Teil des Antriebsmanagements, womit auch neue Architekturen angeregt werden.

In the recent years alternative drive technologies have been become increasingly important. The price increase of petroleum based fuel in the past few years has given rise to various research and development efforts for energy conservation. However, reduced fuel consumption and therefore operating cost and reduced gaseous emissions including primarily carbon dioxide (hence global warming) are the major driving forces behind considerations of sub systems like electromechanical brake booster (eBKV) [1,2,3]. The future viability of electrical powertrains is greatly dependant on their range and battery storage capacity. Electric vehicles will achieve ranges that are sufficient for everyday use only with efficient batteries, intelligent energy management and especially the recovery of braking energy. When a conventional vehicle applies its brakes, kinetic energy is converted to heat by friction between the brake pads and wheels. This heat is carried away into the environment and the energy is effectively wasted. The total amount of energy lost in this way depends on how often, how hard and for how long the brakes are applied. Hybrid and electric vehicles with regenerative braking system are different in that. They recover kinetic energy via the electric motor and store it as electrical energy. This process is known as regenerative braking. This method makes it possible to increase the range of electric vehicles and reduce the CO2 emission.

Electrically driven axles differ in many aspects from conventional drives with combustion engines. These differences regard both the actuator properties and the characteristics of the drive train structure. Based on these differences, new potentials for improving the driving performance and the quality of braking control systems can be tapped.

Modern vehicles act more and more autonomously. While in the early years of driver assistance systems parking aids were only available in premium-class vehicles and initially provided drivers only with acoustic help in maneuvering a vehicle into a parking space, the evolutionary automatic parking assistance system today is available even in medium-sized vehicles. The simple cruise control evolved into adaptive cruise control (ACC); the automatic emergency-brake-assist function is an extension of ACC. Lane change, intersection and emergency-steer-assist are additional electronic “co-drivers” intended to make driving safer.

The customer’s demand for novel functionalities in modern vehicles requires reconsidering the traditional architecture of vehicle electronics and the continuous further development of individual systems. Especially, driver assistance and safety systems lead to increasing functional complexity and demand powerful actuators to intervene into vehicle handling. These trends increasingly cause by-Wire systems to invade critical components as the steering or braking system. While supporting the achievement of functional goals driven by the application, these systems come along with challenges in terms of functional safety if cost objectives have to be met.

The hydraulic brake products like brake calipers, master cylinders and boosters are the foundation of today’s complex vehicle brake systems. The state of the art application is very often an individual design, due to the fulfillment of customer requirements within the available installation space.

One of the main goals of the EU, federal traffic agencies and automotive consumer protection associations is to reduce traffic accidents and fatalities. To achieve this, the measures of passive vehicle safety have been massively improved over the last 15 years. The level of passive safety for affordable cars in Europe is near to its upper limit while still about 3,300 people are killed in traffic accidents in Germany1 (about 50% in passenger cars, 25% vulnerable road users like pedestrians and cyclists). In order to increase road safety and to keep up with the technical development, the European New Car Assessment Programme (Euro NCAP) requirements have become more stringent, with more emphasis on active safety systems and accident avoidance/ mitigation. Since 2014,

A

utonomous

E

mergency

B

rake Systems have been included in the rating. Thus a future 5-star car should be equipped with an AEB system. These testing and assessment protocols are based on accident data, the findings of EU funded research programmes such as AsPeCSS and consumer protection tests that have been performed for instance by ADAC since 2011. Currently there are three different groups of these assistant systems:

AEB City Brake function on standing cars from 10-50kph

AEB Interurban Brake & warning function on standing, moving and braking cars; 30-80kph

AEB Pedestrian Brake & warning function on crossing pedestrians from 20-60kph

Automated driving is no pure vision anymore. First vehicles with similar functionalities are already in series or will come into series production soon

In 2013 BMW has launched worldwide the i3, the first BEV automobile designed to be completely sustainable, and the i8, the most advanced PHEV sport car of its time. These two cars are the first members of a new BMW brand, the BMW i.

Tyres pose a distinct set of challenges for the chassis development process in general and the advanced chassis development process in particular. Being highly non-linear composite structures, tyres are less amenable to the modelling and development techniques applied to other chassis components. Tyres are also not developed and manufactured by the vehicle manufacturer, which limits design interchange and access to prototypes and complicates the chassis development timeline.

The tyre as link between road and vehicle is one of the key elements in the field of vehicle dynamics concerning safety, driving performance and driving comfort [1]. To simulate the transmitted forces and torques in the contact patch of the tyre, vehicle dynamic models are coupled with handling tyre models. The data to parameterise tyre models is mainly identified by tests at the tyre test rig. These tests are accurate and reproducible measurements, as generally known, but correspond only rarely to real tyreroad contacts [2]. It must be clear to the user of tyre models that these measurement data are subject to systemic significant scatter. Studies have shown that measurements of the cornering stiffness on various tyre test rigs can differ up to 20%. Significant factors for these differences are the coefficient of friction, the geometry of the treadmill or drum or the high tread wear and thermal load [3]. Therefore an adaptation of the tyre parameters is necessary (e.g. cornering stiffness, maximum grip …) such that the vehicle dynamic simulation correlates to the real driving behaviour.

This manuscript is not available according to publishing restriction.

This manuscript is not available according to publishing restriction.

The oldest wheels, assembled from several sections of wood, were produced around 4000 B.C. in Mesopotamia, meaning that one of the most important inventions of mankind took place over 6000 years ago. The wheel on the “Standard of Ur” [Figure 1] has been dated to approximately 2600 B.C. . These first wheels were actually already made of fiber composite materials because the wood can be regarded as a lignin matrix with embedded, stiff cellulose fibers.

The accuracy of friction estimation depends on the sensors used. Furthermore, the costs of sensors have to be considered during system design.

In this work, we discuss how sensor configurations (i.e. subsets of the sensors used during our measurements) can be determined minimizing RMSE and/or sensor costs. We first demonstrate that simple strategies (e.g. replacing a sensor by a better one) may fail. Then we discuss different optimization strategies (search strategies and cost functions). By applying them, we obtained several sensor configurations showing interesting trade-offs in minimizing RMSE and sensor costs. Based on these results, we argue whether general statements can be derived about the usefulness of particular sensors and sensor combinations.

The understanding of tire performance during ABS braking is a complex task. The final ABS braking distance on dry, wet and icy roads is the result of several parameters interacting with each other on specific time (µs … s) and length (µm … cm) scales. These parameters describe the surface roughness and state, the tire tread compound and tire construction as well as the vehicle characteristics (like ABS controller, suspension, vehicle weight, etc.). See figures 1 and 2 for illustration. The work presented here targets the assessment of these key parameters at the actual tire operating conditions. Guided by the rubber friction theory published by B.N.J. Persson [1] and its numerous extensions, the key parameters for rubber friction have been identified and characterized in the appropriate parameter space.

Using the vehicle as a sensor for road grip becomes more promising when the vehicle’s reaction to both longitudinal and lateral excitation is exploited. This results in separate two dimensional estimates for the lower bounds and maxima of the friction value. The estimates need to be summarized to one lower boundary for pavement detection as well as generalized for a road-centered quantity. We will refer to the latter as road grip. As a basis to derive the availability in terms of temporal and spatial road coverage, a functional development and prototype implementation of a twodimensional estimation algorithm was conducted. It exclusively uses information from automotive grade sensors.

This paper describes the “Autonomous Driving Intelligence System to Enhance Safe and Secured Traffic Society for Elderly Drivers” project which was adopted and started in 2010 as one of the technology innovation projects to vitalize “aged society”. The project is sponsored by Japan Science and Technology Agency (JST). This project has been carried out based on the university and industry collaborative framework which is comprised of Tokyo University of Agriculture and Technology (TUAT), and the University of Tokyo, Toyota Central R&D Laboratory, and Toyota Motor Corporation. The main purpose of this project is to realize an autonomous driving intelligence system embedding an experienced driver model to recover degraded performances of recognition, decision-making and operation for elderly drivers. The vehicle control concept proposed in this project will be penetrated into the market as advanced driver assistance systems, and the concept is applicable to autonomous driving system design for certain traffic circumstances in the near future. Current activities and research results gained from the project study are described in the paper.

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