Josef Zehetner

Integral Sliding Mode for the Torque-Vectoring Control of Fully Electric Vehicles: Theoretical Design and Experimental Assessment

This paper presents an integral sliding mode (ISM) formulation for the torque-vectoring (TV) control of a fully electric vehicle. The performance of the controller is evaluated in steady-state and transient conditions, including the analysis of the controller performance degradation due to its real-world implementation. This potential issue, which is typical of sliding mode formulations, relates to the actuation delays caused by the drivetrain hardware configuration, signal discretization, and vehicle communication buses, which can provoke chattering and irregular control action. The controller is experimentally assessed on a prototype electric vehicle demonstrator under the worst-case conditions in terms of drivetrain layout and communication delays. The results show a significant enhancement of the controlled vehicle performance during all maneuvers.

A Derivative Estimation Toolbox based on Algebraic Methods - Theory and Practice

In this paper, the implementation and usage of a so-called Derivative Estimation Toolbox is demonstrated. By means of this toolbox, time derivatives of sampled, noisy time signals may be determined in realtime, all based on a recently presented algebraic derivative estimation method. The main contribution is a possible implementation on a prototyping control unit. The performance of the Derivative Estimation Toolbox is experimentally validated on a brake-testbench. In particular, the friction force and the drive torque are estimated in realtime.

Model-based coupling approach for non-iterative real-time co-simulation

Non-iterative co-simulation is a prerequisite for the time correct coupling of distributed solved numerical problems. For this coupling approach typically signal-based extrapolation schemes are used to resolve existing bidirectional dependencies between the interacting subsystems. Nevertheless, the introduced coupling errors influence the entire system behavior. In the case of coupled real-time systems inherent time-delays and noisy measurements lead to significant additional distortions. Thus, to avoid a deteriorating dynamic behavior of coupled systems - which can even lead to instability - new coupling approaches are mandatory. A model-based extrapolation scheme is motivated to realize a compensation of the occurring round-trip-times and noise-handling. Besides the description of the fundamentals a representative example demonstrates the effectiveness of the proposed coupling approach.

Improving vehicle dynamics by active rear wheel steering systems

This article presents two design strategies for an active rear wheel steering control system. The first method is a standard design procedure based on the well-known single track model. The aim of the feedback loop is to track a reference yaw rate in order to improve the handling behaviour. Unfortunately, a reasonable specification of the reference yaw rate proves to be a nontrivial task. A second approach avoids this drawback. The structure of the controller is regarded as a virtual mass-spring-damper system with adjustable parameters. Due to the high abstraction level of this method, the controller parameters can be tuned intuitively. Experiments with a prototype vehicle illustrate the effectiveness of the two proposed methodologies.

A model-based approach for prediction-based interconnection of dynamic systems

This paper proposes a model based coupling technique for interconnected systems. It helps to overcome problems arising whenever the interconnections have a non-negligible influence on the overall system behavior. The main idea of the method is to use prediction schemes which compensate for performance degradation due to coupling imperfections. Exemplarily the so-called co-simulation scenario is selected to demonstrate the principles of the presented approach and its effectiveness by means of a complex real-time application.

A Brake-Testbench for Research and Education

This paper outlines the concept of a laboratory brake-testbench for education and research. It was developed to investigate the deceleration behaviour of a cars wheel during braking. The major components of the testbench are a driven wheel which is equipped with a disc brake and a rotating steel cylinder. The testbench is mainly used to test alternative antilock braking algorithms and to teach students of automotive engineering the principles of conventional braking systems. Furthermore it is used as a test object for robust nonlinear observers especially in automotive applications.

Echtzeit-Implementierung eines algebraischen Ableitungsschätzverfahrens (Realtime Implementation of an Algebraic Derivative Estimation Scheme)

In der vorliegenden Arbeit wird die Echtzeitimplementierung eines algebraischen Verfahrens zur Schätzung von Zeitableitungen gemessener Signale vorgestellt. Ausgehend von einer Taylorreihendarstellung des betrachteten Signals werden mit Methoden der Operatorenrechnung Berechnungsvorschriften für Zeitableitungen beliebiger Ordnung hergeleitet. Diese können effizient in Echtzeit ausgewertet werden. Im vorliegenden Fall wird Matlab/Simulink als Werkzeug eingesetzt. Mit Hilfe eines Codegenerators und eines Target-Compilers können die Echtzeitroutinen mühelos auf verschiedene Zielplattformen übertragen werden. An Hand eines praktischen Anwendungsbeispiels wird die Leistungsfähigkeit des Ansatzes demonstriert. In this article, a realtime implementation of an algebraic method for estimating the time derivatives of measured time signals is presented. Based on a Taylor series expansion of the time signal, elementary techniques from operational calculus are used for deriving estimator formulas for time derivatives of arbitrary order. These formulas may be evaluated very efficiently, in realtime. This task is solved by Matlab/Simulink by means of which resorting to code generation libraries and target link compilers realtime routines can easily be transferred to different target architectures. A laboratory setup demonstrates the applicability and impressing performance in practice.

Requirement identification for variability management in a co-simulation environment

Co-simulation is a powerful approach to verify a system design and to support concept decisions early in the automotive development process. Due to the heterogeneous nature of the co-simulation framework there is a lot of potential for variability requiring the systematic handling of it. We identified two main scenarios for variability management techniques in a co-simulation environment. Variability management capabilities can be included in the co-simulation tool itself or provide variability mechanisms to configure the co-simulation externally from a software product line. Depending on the context, one or even both scenarios can be applied. This work addresses different types of variability in an independent co-simulation framework (ICOS) and defines requirements for a realization concept.

Das Virtuelle Fahrzeug am Motorprüfstand

Potenziale zur Effizienzsteigerung in der Entwicklung konnen am Motorprufstand nur durch eine realitatsnahe Darstellung des instationaren Motorverhaltens in allen Betriebszustanden erschlossen werden. Durch den Einsatz des neuen Motorprufstands „VVETB“ von AVL wird „Frontloading“ im Entwicklungsprozess moglich. Entwicklungsaufgaben, die normalerweise in spaten Phasen des Entwicklungsprozesses stattfinden, konnen in eine fruhe Phase vorgezogen werden.

The virtual vehicle at the engine test bed

In reality close representation of the installed engine behaviour unlocks the potential for increased efficiency in the development process at the engine test bed. With the utilization of the new engine test bed “VVETB” by AVL “Frontloading” within the development process can be achieved. Development tasks, which are normally done in later phases of the development process, can be performed in early phases.