Jens Neubeck

Sideslip angle estimation based on input-output linearisation with tire-road friction adaptation

An adaptive sideslip angle observer considering tire–road friction adaptation is proposed in this paper. The single-track vehicle model with nonlinear tire characteristics is adopted. The tire parameters can be easily obtained through road test data without using special test rigs. Afterwards, this model is reconstructed and a high-gain observer (HGO) based on input–output linearisation is derived. The observer stability is analysed. Experimental results have confirmed that the HGO has a better computational efficiency with the same accuracy when compared with the extended Kalman filter and the Luenberger observer. Finally, a road friction adaptive algorithm based on vehicle lateral dynamics is proposed and validated through driving simulator data. As long as the tires work in the nonlinear region, the maximal friction coefficient could be estimated. This algorithm has excellent portability and is also suitable for other observers.

Nichtlineare Lenkregler für den querdynamischen Grenzbereich (Nonlinear Steering Controllers for the Lateral Dynamics Stability Limit)

Beim Entwurf eines Lenkreglers zur automatischen Spurführung wird das charakteristische Sättigungsverhalten der Seitenkraftkennlinien bei großen Schräglaufwinkeln im Streckenmodell berücksichtigt. Es zeigt sich, dass bei dem aus mathematischer Sicht optimalen modellprädiktiven Regler eine Vielzahl von Reglerparametern auf heuristischem Wege festgelegt werden muss. Daher wird hier, nach dem Prinzip der exakten Linearisierung, ein Rückführgesetz vorgeschlagen, dessen Leistungsfähigkeit dem modellprädiktiven Regler gleichkommt, das dabei aber nur einen Bruchteil der Rechenzeit und lediglich zwei Reglerparameter mit physikalisch anschaulicher Bedeutung benötigt. Die Position des fahrzeugfesten Spurführungs-Referenzpunktes hat erheblichen Einfluss auf das Stabilitätsverhalten im Grenzbereich. Dies kann durch mathematische Stabilitätsanalyse und anhand von Simulationen stabilitätskritischer Fahrmanöver demonstriert werden. Simulationsuntersuchungen mit einem Formelrennfahrzeug und Messfahrten mit einem X-by-wire Versuchsträger im Modellmaßstab, der am Institut für Verbrennungsmotoren und Kraftfahrwesen der Universität Stuttgart (IVK) aufgebaut wurde, belegen die Fähigkeit des hier vorgestellten Regelsystems zur hochpräzisen Spurführung im querdynamischen Grenzbereich. Dabei beträgt die maximale seitliche Abweichung von der Soll-Trajektorie nur wenige Prozent der Fahrzeugbreite. The well known nonlinear shape of the vehicles side force characteristics is considered to design a steering controller for automatic guidance. When applying nonlinear model predictive control, which should be the best possible controller from a mathematical point of view, it turns out that a large number of controller parameters has to be defined using heuristic methods. In this paper, however, exact linearization technique is used to determine a feedback law that matches the performance of the model predictive controller with a much lower amount of computing time and only two controller parameters. The position of the vehicle fixed reference point for automatic guidance significantly affects the stability properties of the control loop, which can be proven by means of mathematical stability analysis and simulation results concerning test maneuvers at the stability limit. The capability of performing precise automatic guidance at the lateral dynamics stability limit is shown by means of a race car simulation model and a 1 : 5 scaled x-by-wire experimental prototype. During these simulations and test runs, the maximum lateral deviation from the desired trajectory was within a few percent of the vehicle width.

Der Fahrer als Sensor fuer die Bewertung des Seitenwindverhaltens

Derzeit existiert kein einheitliches Verfahren zur Beurteilung des Fahrzeugseitenwindverhaltens. Ein Vergleich gangiger Verfahren zeigt bei einigen Fahrzeugen unterschiedliche — teilweise widerspruchliche — Ergebnisse. Am Forschungsinstitut fur Kraftfahrwesen und Fahrzeugmotoren Stuttgart (FKFS) der Universitat Stuttgart wird eine Beurteilungsmethode entwickelt, die den Fahrer als Sensor betrachtet. Der Fahrer passt sein Lenkverhalten bei Seitenwind dem Fahrzeugverhalten an. Aus dieser Anpassung des Fahrers wird die subjektive Beurteilung des Fahrzeugseitenwindverhaltens durch den Fahrer abgeleitet. Das Ziel der Untersuchungen ist die Modellierung eines adaptiven, virtuellen Fahrers, mit dem das Seitenwindverhalten bereits in der Entwicklungsphase untersucht werden kann.

Method for analysing the feeling of safety at high speed using virtual test drives

The interaction between vehicle and driver within the close-loop perception and control process is a very important research aspect in the development of new vehicles. Previous investigations indicated the increasing importance of the feeling of safety in conventional and severe driving situations. A typical European situation is fast driving on autobahn or highway with simultaneous effects of lateral dynamics and vertical disturbances. Especially in this case the impression of safety influences the overall driver’s vehicle assessment. For vehicle manufacturers it is essential to provide an adequate feeling of safety, whereby the vehicle has to be stable and comfortable and has to meets customers’ expectations [1]. Most investigations and test definitions related to vehicle stability are focusing on critical driving situations such as maneuvers defined in the ISO standards. Apart from these situations, customer-oriented driving maneuvers in everyday driving situations become increasingly important and have to be defined. In [2] it is described, that especially driving safety, well feeling and comfort are important criteria for customers’ decision-making to buy a new car. Other aspects are smooth vehicle movements and consequently a higher ride comfort. This causes a good subjective impression of the level of safety at higher speeds. Furthermore, a harmonious roll behavior contributes to a good feeling of safety [3]. However, not only in the role as a driver, trust in the vehicle is particularly important. All other vehicle occupants on the passenger and the back seats should feel comfortable without disturbances by unusual or annoying vehicle movements. Considering new driving scenarios such as autonomous driving, special attention must be paid to vehicle motions as reaction from uneven road surfaces or lateral and vertical dynamics control systems. Again, in this situation the human sense of safeness and trust in the vehicle and its body movements is particularly important.

Stand der Technik

Reifenmodelle spielen als kraftubertragendes Bindeglied zwischen Fahrzeug und Fahrbahn in der Simulation des Gesamtfahrzeugverhaltens eine entscheidende Rolle und bestimmen oft masgeblich die Ergebnisqualitat. Sie lassen sich hinsichtlich mehrerer Kriterien klassifizieren, [71].

Schlussfolgerung und Ausblick

Im Rahmen der vorliegenden Arbeit wurde ein teilempirisches thermisches Nutzfahrzeugreifenmodell zur Prognose realer transienter Rollwiderstandsverlaufe vorgestellt. Das Modell wurde sowohl auf Basis einer gros angelegten Messkampagne im realen Guterfernverkehr als auch basierend auf Rollwiderstandsmessungen auf der Strase entwickelt und parametriert. Das transiente thermische Rollwiderstandsmodell wurde in ein Nutzfahrzeugreifenmodell eingebunden und in eine vorhandene Gesamtfahrzeugentwicklungsumgebung integriert.

Innovative torque vectoring control concept to generate predefined lateral driving characteristics

Active chassis systems offer the possiblity to specifically influence the driving behavior of the passive vehicle [1]. According to Becker et al., the driving behavior of a vehicle is defined by the car’s reaction to driver inputs and to disturbances during a maneuver [2]. In the context of lateral vehicle dynamics, the reaction of the vehicle can be described by the yaw rate and the side slip angle in the center of gravity. Since the latter two quantities are dynamically coupled, Direct Yaw Moment Control or Torque Vectoring is not appropriate to control the vehicle’s yaw rate and side slip angle independently [3]. The proposed innovative Torque Vectoring system in this paper focusses on yaw rate tracking. References to systems with additional active rear steering to control the vehicle’s side slip angle independently are exemplariliy given in [4].

Subjective perception and evaluation in the virtual test drive

The high simulation quality of today’s driving simulators enables investigations with a driving impression close to reality. The possibility of such a realistic vehicle simulation environment allows new test methods of driving dynamics related topics. While the driver immerse in the virtual reality his subjective impression is an important evaluation instrument for the development process of driving dynamics. Benefits of the virtual test drive include a higher reproducibility and a faster generation of vehicle variants compared to real on-road tests. These benefits lead to a better system understanding and can improve the process in the early development stages.

Development of objective criteria to assess the vehicle performance utilized by the driver in near-limit handling conditions of racecars

Racecar operation typically takes place in the near-limit range of the vehicle’s tires. Drivers attempt to exploit all of a vehicles potential to achieve the minimum possible laptime around a given circuit.

Driving dynamics development

Improvements and advancements in automotive engineering require increasingly innovative and interdisciplinary views and approaches. This article by the Research Institute of Automotive Engineering Stuttgart (FKFS) in cooperation with the Institute of Combustion Engines and Automotive Engineering (IVK) shows how the traditional field of driving dynamics is located in modern development processes and how that specific area can be extended by considering interdisciplinary approaches on the basis of various projects in the field of vehicle technology and driving dynamics