PhD Projects

The PhD projects are accomplished in cooperation with the University of Rostock, Clausthal University, Liverpool John Moores University and industrial partners.

  • Acceleration of Discrete Event Simulation Studies using the DEVS formalism on HPC systems
    M.Eng. David Jammer
    in cooperation with University Rostock
    since September 2019
Project Description D. Jammer

Project Description D. Jammer

Over the last 40 years, a considerable number of formalisms and simulators have been developed for modeling and simulating Discrete Event Systems (DES). One formalism that has received particular attention in the research community is the Discrete Event System Specification (DEVS). This approach, today known as Classic DEVS, was developed by Zeigler from systems theory and published in 1976. Over the years, there have been further developments of the formalism with respect to specific application needs, such as fuzzy, hybrid or real-time simulations. The main evolution for general use is Parallel DEVS (PDEVS), which was introduced by Chow in 1994. Classic DEVS as well as PDEVS can be viewed primarily as extensions of a Moore machine. Therefore, modeling of certain Mealy-type components can be difficult with these formalisms. Preyser et al. analyzed this problem and presented a revised version RPDEVS in 2018. In 2020 Junglas showed that RPDEVS still has problems with complex structures of concurrent events. He proposed the use of concepts of Nonstandard Analysis to develop a more robust method of handling concurrent events. The short name of the new formalism variant should be NSA-DEVS.

Subsequently, this idea was further developed as joint research with the CEA group. Moreover, NSA-DEVS became a central component in this cooperative PhD project with the Institute for Automation at the University of Rostock.

  • Human-Robot Collaboration with Reinforcement Learning in Context of Assembly
    M.Eng. Georg Kunert
    in cooperation with Clausthal University
    since March 2018
Project Description G. Kunert

Project Description G. Kunert

Manufactural assembly is becoming increasingly complex. At the same time, efforts to increase efficiency are on the rise. Among other things assembly processes where humans and robots work together offer great potential for improvement.

Aim of the project is to enable the robot control to independently learn a behaviour strategy to react on the stochastic behaviour of humans and the entire environment with the help of Reinforcement Learning.

It is investigated how a robot control can be generated from a learned behaviour strategy, how reinforcement learning can be accelerated, and how the learning effort of the learning process can be reduced by using several agents.

  • Variability Modeling for Simulation in Engineering Using System Entity Structures
    M.Eng. Hendrik Folkerts
    in cooperation with Clausthal University
    since September 2017
Project Description H. Folkerts

Project Description H. Folkerts

The System Entity Structure (SES) is a high level approach for variability modeling, particularly in simulation engineering, which is under continuous development. In this context, an enhanced framework is used that supports dynamic variability evolution with the SES approach.

An SES describes a number of structure variants encoded in a tree structure with nodes and edges. On the SES a pruning operation is defined, which resolves all decision points on execution, transferring the SES in a Pruned Entity Structure (PES). The PES describes one possible structure variant. Leaf nodes can contain links to a Model Base (MB) storing basic and coupled models. With the help of a build method, an executable simulation model (SM) can be built from a PES and basic models from the MB. For automatic derivation of PES and generation, simulation, and evaluation of SMs the SES/MB approach was extended.

For this extended SES/MB (eSES/MB) framework software tools are developed. This project focuses on the development of different approaches for the generation of SMs for several simulators. In this context the Functional Mock-up Interface (FMI) as general simulator interface is connected to the eSES/MB framework.

  • Reactive and Cooperative Robot Controls Based on the SBC Framework 
    Dr.-Ing. Birger Freymann
    in cooperation with Clausthal University
    (PhD thesis submitted 11/2021, thesis defense 04/2022)
    poster & video

  • Variant Management in Modeling and Simulation Using the SES/MB Framework
    Dr.-Ing. Artur Schmidt
    in cooperation with University of Rostock
    (PhD thesis submitted 10/2018, thesis defense 06/2019)
Project Description A. Schmidt

Project Description A. Schmidt

    Modeling and Simulation (M&S) forms the basis of the modern development and planning
    process in engineering. Modeling deals with the abstraction of essential aspects of technical
    systems and their implementation in a model. During simulation the implemented model is
    executed aiming to gain knowledge about the system behavior. A single model execution is
    called a simulation run. A simple simulation experiment comprises many simulation runs
    with varied input variables. Complex simulation-based experiments are characterized by the
    integration of simulation with numerical methods such as optimization, screening or sensi-
    tivity analysis. Highly complex simulation experiments investigate the different model
    structures in addition to the parameter space.
    The classical M&S approach is increasingly reaching its limits in engineering. One
    reason is the growing customers demand for customized products. This increases the variety
    and often the complexity of technical systems as well as of the resulting models and
    investigation objectives. This means that the specification and execution of simulation
    experiments includes not only a set of model variants with their parameter settings, but also
    combinations with numerical methods and their configuration. Furthermore, the sequence of
    variants to be investigated or numerical methods to be applied often arise from previously
    determined experiment results.
    Accordingly, this work contributes to the development of general methods for variant
    management in M&S up to the simulation experiments’ level and their automated execution.
    The proposed solutions are developed based on the ASIM procedure model, the modular-
    hierarchical modeling approach and the System Entity Structure/Model Base (SES/MB)
    framework. The variant management is based on different phases: variant analysis,
    variant formalization, variant implementation and variant generation. Furthermore, a
    modular-hierarchical structuring for simulation experiments is developed. By extending the
    SES/MB framework, not only model variants but complete experiment variants can be speci-
    fied, implemented and generated. Moreover, a framework for automated experimentation
    based on the extended SES/MB framework is proposed. Finally, the methods are presented
    using an application example from the field of production and logistics.

    • Modeling and Control in Breathing Therapy
      in cooperation with HOFFRICHTER GmbH Schwerin & University of Rostock
      M.Eng. Mathias Scheel
      2014 - 2021
      (PhD thesis submitted 05/2020, thesis defense 04/2021)

    • A Contribution to the Determination of Operationg Points for Axial Compressors
      (Ein Beitrag zur Betriebspunktbestimmung von Axialverdichtern)
      in cooperation with University of Rostock and IAV GmbH
      Dr.-Ing. Rocco Reinhardt
      2014 - 2019
      (PhD thesis submitted 2019, thesis defense 12/2019)

    • Contribution to the Control of the Air Ratio of a Gasoline Engine, Taking Into Account the Dynamics of a Three-way Catalyst
      (Beitrag zur Regelung des Luftverhältnisses eines Ottomotors unter Berücksichtigung der Dynamik des Dreiwege-Katalysator)
      Dr.-Ing. Michael Tomforde
      in cooperation with University of Rostock and IAV
      (PhD thesis submitted 2014, thesis defense 10/2014)
    Project Description M. Tomforde

    Project Description M. Tomforde

    In practical control systems, deadzone characteristics are encountered in a wide range of mechanical and electrical components, such as valves or DC servo motors. Another process that exhibits a deadzone characteristic is the three-way catalyst. Due to its oxygen storage ability, the normalized air-fuel ratio post catalyst remains at one despite air-fuel mixture variations pre catalyst, as long as certain levels of the oxygen storage state are not exceeded. 
    The aim of this project is to reduce the exhaust emissions produced by cars equipped with a three-way catalyst by improving the control of the air-fuel mixture. Low emissions are reached if post-catalyst air-fuel ratio remains at one despite large air-fuel mixture variations and a biased measurement of pre-catalyst air-fuel ratio. Typically, the aim of a controller for deadband processes is to overcome the deadzone in an optimal way, commonly by employing the deadzone inverse to cancel it. For this project, however, the aim of the controller is to keep the oxygen storage state within the deadzone. 
    In order to control the oxygen storage state (and pre-catalyst air-fuel ratio which is connected to the storage state via the deadzone), a model-based approach is proposed, since the storage state cannot be measured directly by a sensor. Thus, the project includes i) the development of a control-oriented model of a three-way catalyst, which has to be both accurate and simple enough to be calculated on the vehicles electronic control unit, and ii) the design of a suitable control strategy. 

    • Torque Coordination of Spark Ignition Engine - Control of Processes with Auxiliary Actuating and Control Variables
      Dr.-Ing Christian Steinbrecher
      in cooperation with University of Rostock and IAV
      July 2006 - 2010
      (PhD thesis submitted 03/2010, thesis defense 11/2010)
    Project Description C. Steinbrecher

    Project Description C. Steinbrecher

    Due to increasing demands on driving comfort, consumption and emission of modern combustion engines new combustion processes came to introduction of series production in the last years. The potential of these combustion processes in general can only be utilized by introduction of additional actuating and measure variables. Thereby an increasing complexity from control viewpoint is almost unavoidable. The choice of particular actuating variables has decisive influence on efficiency, comfort and waste gas emission. Besides the main manipulated variables, as e.g. the throttle position, there are some more different actuating variables that are in many cases only effective for limited operating ranges of the engine with different effects.
    The cooperative graduation project deals with the general problem of control with auxiliary actuating and control variables. Application emphasis of the procedures to be developed is located in the field of combustion engine controllers.
    One aim is to find the best compromise between efficiency, driving comfort and waste gas emission. This is achieved by an optimized choice, according to several criteria, of available actuating variables for the realization of the driving torque. 

    • Application of Sophisticated Algorithms for Spark Ignition Engine Control
      Dr.-Ing. Stefan Behrendt
      in cooperation with University of Rostock and IAV
      March 2006 - 2018
      (PhD thesis submitted 2017, thesis defense 01/2018)
    Project Description S. Behrendt

    Project Description S. Behrendt

    The coordination of available actuators in modern engine control units (ECUs) is a challenging task. The broad variety of signals (e.g. throttle, advance angle, exhaust gas recirculation, injection, etc.) to influence the momentum and engine speed are coupled. Therefore a multi-variable control should manage these actuators to fulfill the control aim in an efficient manner. A compromise respecting further aims like comfort issues and exhaust gas emissions must be found. An available scheme to cope with these requirements is model predictive control (MPC). The incorporated optimization ensures the optimal selection of actuator signals under their constraints. 
    The cooperative graduation project is concerned with the development of a suitable quadratic program that solves the optimization within the MPC algorithm. It needs to fulfill the real-time requirements when run on high-potential micro-controllers (e.g. Infineon Tricore) that are incorporated in modern ECUs. 

    • Simulation model-based Rapid Control Prototyping of Complex Robot Controls
      Dr.-Ing. Gunnar Maletzki
      in cooperation with University of Rostock
      since March 2005
      (PhD thesis submitted 06/2013, thesis defense 03/2014)
    Project Description G. Maletzki

    Project Description G. Maletzki

    Progressive robotics research opens up new application fields incessantly. Hence, demands on the development of robot controls are increasing. Easy programming and integration of different external hardware are of particular importance. The aim of every control implementation is to realise easy, safe, fast and cost-effective design and commissioning of robot applications. Therefore, it is essential to avoid re-implementations in the entire development process. 
    An approach for integrated modeling, simulation and operation, named "simulation model-based rapid control prototyping", is introduced and illustrated by the example of a sensor based robot control. It is discussed how simulation models have to be structured in the early system design stage in order to extend them to model-based control programs for the operation stage stepwise. 
    Objects of this research are (i) the prevention of re-implementations, (ii) the development of a task oriented programming approach, (iii) methods for an easy integration of different hardware and (iv) a concept for specification of high flexible and re-configurable controls. 

    • Simulation Based Parameter and Structure Optimisation of Discrete Event Systems
      Dr. (PhD) Olaf Hagendorf
      in cooperation with Liverpool John Moores University and Syntax Software GbR
      July 2005 - July 2009
      (PhD thesis submitted 05/2009, thesis defense 07/2009)
      The research reported in this thesis details a new simulation based approach providing automatic reconfiguration and optimisation of both model structure and model parameters.This is achieved through a combination of simulation, optimisation and model management methods. Simulation is used to determine current model performance and an optimisation method, assistet by model management, searches for an optimal solution with repeated model parameter and model structure changes. The approach employs a meta-modeling method to define a set of model structure variants and includes a model base with pre-defined basic components. With the meta-modeling method the model management can determine specific model structures and create executeable models. 

    • DEVS-Based Modeling and Simulation in Scientific and Technical Computing Environments
      Dipl.-Ing (FH) Christina Deatcu
      in cooperation with University of Rostock
      since January 2005
      Discrete Event System Simulation (DEVS) in our days is not widely accepted by engineers. This is mainly caused by the fact that engineers usually are rather familar with Scientific and technical Computing Environments (SCEs) than with the use of high level programming language simulation libraries. Furthermore, most of those comercial off-the-shelf tools are just suitable for specific application areas.
      One more aspect is that SCEs offer good opportunies to integrate DEVS modeling and simulation with other advanced techniques such as e.g. optimisation, ode solvers, data aquisition and analysis and integration of hardware.
      In this project main focus is put on modeling and simulation of hybrid system dynamic by utilisation of the features for solving ordinary differential equations within the most popular SCE Matlab. The approach includes modeling of structure variable systems, as well.
      A prototype for DEVS modeling and simulation is available here.

    • Investigations on SCE Based Parallel Computing
      Dr.-Ing. René Fink
      in cooperation with University of Rostock and IAV
      March 2004 - December 2007 
      (PhD thesis submitted 07/2007, thesis defense 12/2007, honored with summa cum laude)
      Scientific and technical Computing Environments (SCEs) like Matlab are powerful tools for todays engineers, especially for desing problems. But the increasing complexity of calculations often lead to bottlenecks in interactive design processes. Parallel processing offers one possibility to bypass those bottlenecks. Within this research project, approaches for combining SCEs and parallel processing are investigated and classified. Several tools are examined with respect to their programming model, abstraction level and communication performance. Furthermore, several example programs are parallelized for runtime measurements and implementation effort investigations.

    • The Development of a Genetic Programming Method for Kinematic Robot Calibration
      Dr. (PhD) Jens-Uwe Dolinsky
      in cooperation with Liverpool John Moores University
      finished March 2001