Wolfgang Drewelow

A DEVS-based approach for modeling and simulation of hybrid variable structure systems

The modular-hierarchical modeling subdivides a system into dynamic describing atomic, and structure describing coupled systems. Due to the usally static structure of coupled systems, it can sometimes be hard to realize a component-oriented mapping of real system elements in model components. Hence, several approaches to model structural changes are developed, which are roughly classified in the paper.

HLA-based simulation within an interactive engineering environment

This article discusses prerequisites and possible methods of a Matlab/HLA (High Level Architecture) integration and presents a novel concept of an HLA interface that is suitable for interactive usage. The result of a performance comparison study of a demonstration program on different Matlab/HLA interface implementations is given.

A predictive energy management for hybrid vehicles based on optimal control theory

In this paper we propose a predictive energy management for a hybrid electric vehicle with compound power-split powertrain configuration. The strategy relies on information on the future driving trip provided by modern navigation systems. Based on this information a simplified optimal control problem is solved via an indirect variation of extremals algorithm to determine a feasible start value of the adjungated variable. The powertrain controls are then determined from offline calculated maps using the value of the adjungated variables, the current vehicle speed and the requested wheel-torque. The strategy is implemented into a model-based simulation environment and has shown fuel savings on real world driving cycles. It has proven to be real-time applicable and very robust against low accuracy of the predicted driving trip.

Air-fuel ratio control with respect to oxygen storage dynamics

Reducing exhaust emissions is one of the biggest challenges facing the automotive engineering community today. In order to comply with future more stringent emission standards, the air-fuel ratio control must be improved. Commonly used control concepts do not account for the oxygen storage ability of the three-way catalyst, even though the storage state mainly influences post-catalyst exhaust emissions. In this paper a new air-fuel ratio control strategy based on the oxygen storage state is presented. Since the oxygen storage state can not be measured directly, a major component of the controller is a newly developed catalyst model that accounts for the spatial distribution of oxygen within the catalyst. The proposed control concept has been successfully tested on a vehicle equipped with a turbocharged, direct injection gasoline engine.

Improvements in knock control

The aim of this work is to develop an improved method for knock control in gasoline engines. This should enable higher power output compared to existing methods of knock control without raising the level of knock probability. An analysis of a known knock controller shows, that information about distance to knock limit is not used in knock control. Based on this analysis a design of a new knock controller is developed. This controller uses cylinder-pressure signals to estimate the distance to knock limit and to control ignition angle. An improvement in power output is proven using engine tests.

Online Process Identification of Hypnosis

For most kinds of surgeries an adequate anaesthesia is necessary. Three main components characterise an anaesthesia - the relaxation, the analgesia and the hypnosis. This paper treats the topic of the Propofol/ Remifentanil induced hypnosis. We try to find a suitable model structure for the online identification of this process during a surgery. After a review of known models from literature an own model approach was developed and validated. By an offline optimisation study the parameter estimation problem of the defined cost function was examined. An online approach based on a recursive, iterative gradient algorithm was implemented. The quality of the identified parameters could be verified using measurements of surgeries.

Exact air charge feed forward control of a turbocharged SI engine

In this work, a MIMO feed forward control for the air charge, i.e. the mass of air in the cylinders of a turbo charged spark ignition (SI) engine is presented. The control inputs are the angle of the throttle plate and the opening of the wastegate. There are many publications in this field of application. Often the control task is separated into an air charge control with the throttle plate as control input and a boost pressure control with the wastegate opening as control input. These approaches often lack the ability to precisely track reference trajectories in the transition between suction mode operation and turbocharged operation. The approach presented here is based on exact input-output linearization and enables a perfect tracking of air charge reference trajectories in both modes of operation and the transition between them.

Modeling and exact feed forward control of air and burned gas fraction within SI engine cylinders

A physically based, nonlinear model of the masses of air and burned gas inside the cylinders of a spark ignition (SI) engine is presented. Goal of this work is to develop a feed forward control law, which perfectly tracks given reference values of these masses. This is done by utilizing the exact linearization approach [1]. The final feed forward control law is verified in combination with a slightly modified design model as well as the original model.

A Control Oriented Model Design of Heart Assistant Devices

Abstract As a treatment option for patients with end-stage heart failure, mechanical circulatory support systems maintain the blood circulation in the human body. For biventricular assistance or for pediatric patients, paracorporeal pulsatile blood pumps are used. Mobile driving units are available which offer more quality of life to the patients. Automatic control is used to match the pump output to the metabolic needs and to operate the blood pumps as gently as possible. This paper treats the approach of modeling for the EXCOR system (Berlin Heart, Germany). The EXCOR system is a pneumatically driven extracorporeal assist device which allows one-sided and two-sided heart support. Main goal of the modeling was not to simulate the process as accurately as possible. Rather, the resulting model is intended to be the basis for subsequent controller design. Therefore this paper points to problems, which have to be taken into account if the resulting model should be used in practical applications. For this reason several models for different purposes were developed. This article treats mainly the open-loop-control design, but the considerations can be extended to closed-loop-control. The results are currently used to synthesize a robust, efficient control for the EXCOR system.

Die DP-Toolbox: Verteilte und parallele Verarbeitung mit MATLAB / The DP-Toolbox: Distributed and Parallel Processing with MATLAB

Multiprocessingsysteme insbesondere vernetzte Standard-PCs und Workstations (Computerduster) sind für einen wachsenden Anwenderkreis verfügbar. Ihr Einsatz zur verteilten und parallelen Verarbeitung ist aber äußerst aufwendig und nur mit Spezialkenntnissen möglich, da Entwicklungsumgebungen wie MATLAB derartige Verarbeitungskonzepte nicht unterstützen. Diese Lücke wird von der vorgestellten DP-Toolbox geschlossen, welche die interaktive Entwicklung, Validation und Ausführung von verteilten und parallelen Anwendungen auf Basis mehrfacher MATLAB-Instanzen ermöglicht.