21. Internationales Stuttgarter Symposium

Table of Contents

1. Frontmatter

2. Mobility

   1. Frontmatter

   2. MobiLab – The Mobility Living Lab at the University of Stuttgart

      Wolfram Ressel

      Abstract

      MobiLab is following all in all three approaches: the strategy to reach climate neutrality with respect to the mobility of the University of Stuttgart until 2035, the implementation of the car-free campus Stuttgart-Vaihingen and the offer of the Mobility Living Lab Campus Stuttgart-Vaihingen. To reach climate neutrality in mobility until 2035 the University of Stuttgart acts mainly in the areas of the daily mobility of students and employees (commuting) and of the business trips of the employees. To address the students and the employees since the beginning of 2021 the position of a Mobility Manager at the University of Stuttgart is established. The basic idea of the car-free campus Stuttgart-Vaihingen is to shift all parking lots, which are currently scattered on the whole campus to the edge of the campus, finally in one huge car park covering a motorway. Then these peripheral parking facilities, as well as the already existing station of the regional train system (S-Bahn), will be connected with the campus. This will be done with novel means of transport like automated shuttle buses or a rental system with autonomous e-scooters. In this context, forward-looking electrical propulsion concepts in combination with autonomous driving as well as intelligent systems to store and distribute electrical energy are important research areas. Putting all this together, MobiLab finally forms a multifaceted Mobility Living Lab with the three main research topics “research vehicle”, “research street” and “research multi-storey car park”.

   3. Self-Propelled Trailers – An Approach to Type Approval

      Rüdiger Freimann, Sebastian Maier, Alessandro Sannia

      Abstract

      Today’s technological change into alternative power trains is having massive impact beyond the vehicle itself. Tests are showing that air streamed electric vehicles are reduced by half in reach towing a trailer, especially a caravan. In order to compensate for the significant loss of traveling distance with a single battery charge EHG, ZF and FKFS are designing a battery electric propelled caravan.

      In addition to the technical aspects that have already been presented, the approval of powered trailers poses various regulatory challenges. A vehicle category or definition for powered trailers does not yet exist and must therefore be newly created in coordinated association work and in close cooperation with the relevant approval authorities.

      The additional weight that is created by the drive components represents further requirements in terms of driving license and trailer load. The limit of 3.5 t should be emphasized here. Compensation for the additional weight is therefore necessary.

3. Pollutants I

   1. Frontmatter

   2. Preview on Future Developments of Non-exhaust Emissions

      Christof Danner, Andreas Pein

      Abstract

      Future regulations for emissions will increasingly focus on reducing respirable particles, which are caused by abrasion from brakes, tires and roads. PMP (Particle Measurement Program) under the United Nations Economic Commission for Europe (UNECE) has already defined a measurement cycle together with international organizations to measure brake wear on brake dynamometers. Questions about the sampling method and details about the measurement are open.

      This paper will focus on Brake Emissions as the regulations on the one hand are already on the way, and on the other hand the measuring methods are basically defined. Furthermore the central points are not chemical or legislative details, but a view from system and vehicle perspective.

      However, the focus of the regulation is currently only on passenger cars with internal combustion engines, since the measurement process only records the emissions of the “brake” component, without taking into account recuperation, for example.

      The exact definition of the limit values is still pending, but it can be assumed that they will be based on exhaust emissions of internal combustion engines.

      There are numerous measures to reduce particle emissions, which either aim to generally prevent particle emissions from the brake or to filter the particles that have already been emitted.

      As a result, the volume of tests relating to the brake will increase massively, as all variants have to be tested and certified. On the other hand, the necessary changes to the brakes are also affecting other properties of the entire vehicle, causing e.g. compromises between performance, emissions and comfort.

      The automotive industry will then face a further increase in the challenges when considering tire and road abrasion emissions.

   3. Stationary and Transient Simulation of HC and CO Emissions of Diesel Engines

      Christian Schnapp, Michael Grill, Michael Bargende

      Abstract

      Stricter emission and consumption requirements lead to an increasing importance of hydrocarbon (HC) and carbon monoxide (CO) emissions for diesel engines. On the one hand, the amount of HC and CO raw emissions are important for emission prediction as well as for exhaust gas after treatment. On the other hand, they are also important for fuel consumption prediction, since part of the fuel energy is bound in these molecules. Because of this importance, a phenomenological HC/CO model was developed to predict raw emissions for diesel engines. The HC/CO model takes the main emission sources into account: Fuel that slowly leaks out of the injector after the end of injection is included in the HC model. Furthermore, HC and CO emissions from cold areas near the combustion chamber walls are considered. HC and CO emissions from lean overmixed spray regions are also implemented. As an additional source, the CO model considers locally understoichiometric regions of combustion. The validation results of the model using two passenger car diesel engines are shown for this purpose. With the help of the calibrated model, the shares of the different emission sources in the total HC and CO emissions of an engine can be estimated and consequently optimization potentials can be identified. An application of the CO model in the context of an acceleration process within a real driving emissions (RDE) simulation is shown. In this context, it is demonstrated how transient influences on total emissions and emission sources are reproduced in the model.

4. E-Drive

   1. Frontmatter

   2. Flux Squeeze Reluctance Motor Improves Partial Load Efficiency in Vehicle Traction Applications

      Andreas Leich, Philip Hennig

      Zusammenfassung

      Permanent magnet excited (PMSM), externally excited synchronous machines and asynchronous machines (ASM) are state of the art in vehicle traction applications. Currently, the externally excited synchronous machine (EESM) has a high market share in Europe and also asynchronous motors are encountered in many battery electric (BEV) vehicle models still. However, the PMSM becomes the dominant type of vehicle traction drive in the product portfolios of the leading car manufacturers. The reason for this trend is that PMSM machines deliver torque at high efficiency over a wide range of load situations with no need for expensive rotor cooling in the typical load profile of a road vehicle. The main drawback of PMSMs: the mining of rare earth materials produces very harmful greenhouse gases. In the recent years, attempts were made to advance the switched reluctance motor (SRM) in order to make it suitable for traction applications. The advantage of SRM is that no permanent magnets are needed and its production cost is low. The most significant disadvantages are high torque ripple, noise, low efficiency in partial load situations and necessity for expensive rotor cooling. In this paper, the approach of a novel motor concept is shown that relies on seven phases. It overcomes the common drawbacks of SRM is a very promising concept for the next generation of electric vehicles.

   3. Electric Drive System Efficiency Modeling Based on Polynomial Functions

      Lukas Decker, Michael Timmann, Robert Inderka, Martin Doppelbauer

      Zusammenfassung

      During the dimensioning process of hybrid electric propulsion systems, engineers are confronted with a large variety of possible components. A key influence on overall system efficiency is the electric drive system (EDS). Usually, the comparison of different EDS is limited to comparing loss maps and visualizing their differences. Since loss maps are not easy to handle, a simple model of the efficiency characteristics can be helpful to identify the best component for the specific application. This paper proposes a simplified physics-based approach to model the loss characteristics of an EDS based on polynomial functions. The EDS consists of a permanent magnet synchronous machine (PMSM) and an inverter (INV). The developed model achieves good accuracy for both, the base-speed region and the field-weakening region. The modeled losses are dependent on DC-bus voltage in motor as well as in generator mode. The proposed method allows the description of the EDS efficiency characteristic by only few scalar coefficients and increases thereby the comparability of different EDS.

5. Thermal Management

   1. Frontmatter

   2. Plausibility Assessment and Validation of Deep Learning Algorithms in Automotive Software Development

      Felix Korthals, Marcel Stöcker, Stephan Rinderknecht

      Zusammenfassung

      The implementation of artificial intelligence (AI) systems in automotive software development still is an obstacle. Despite of accelerating scientific research and big wins in this field, the practical application is only possible in restricted environments or non safety critical components. There is a need to develop methods to verify the robustness and safety of AI software modules. The data based generation of deep learning (DL) algorithms creates black box models, which properties inhibit a validation as it is done for deterministic algorithms following ISO 26262. This paper introduces methods to assess the plausibility of AI model outputs. A description of the training data domains for a robust training is accomplished by means of one-class support vector machines (OCSVMs). This anomaly detection process encloses valid data within a DB, to be able to verify model outputs during operation. A further categorization of the training data domain into 20, equally spaced sub-domains led to best results in detecting implausible model calculations.

   3. Waste Heat Recovery from Cabin Exhaust Air by Use of Heat Pump

      Nobuaki Miyaji, Jörg Kleemann

      Abstract

      Reducing the energy consumption required for heating ventilation and air conditioning for passenger compartment is one of the key challenge for the thermal management system of electric vehicles to extend the driving range. Particularly at low ambient temperature the power demand for cabin heating increases and drains the battery capacity at the cost of the driving range. Due to the high air exchange rate of the vehicle cabin to the environment, a large share of the heated air is released unused into the environment via the rear exhaust vent as warm exhaust air. Consequently, the heat contained in the cabin air remains unused. A new approach considered in this study is to use the thermal energy in the cabin air as a heat source for a heat pump system to reduce the heating power required to heat the fresh intake air from the ambient. In vehicles with rear air-conditioning systems, the basic components, evaporator and fan, are already present. In this study, the potential of waste heat recovery from cabin exhaust air is demonstrated with the help of simulation and evaluated for various boundary conditions. Limiting effects on the performance are identified and critically discussed.

6. Fuel Cell

   1. Frontmatter

   2. Holistic Design of Innovative Cathode Air Supply for Automotive PEM Fuel Cells

      Michael Harenbrock, Alexander Korn, Andreas Weber, Eva Hallbauer

      Abstract

      Providing clean air for PEM fuel cells is crucial to prevent premature degradation of the stack caused by harmful gases poisoning platinum catalysts. For this purpose, special activated carbon mixtures are used that reliably adsorb target gases such as NO_x, NH₃ and SO₂. Basic investigations in research projects create the basis for the application-oriented design of the filter elements. To prevent flooding of components in the cathode air path including the stack, water separators are used at various positions in the overall system. The components in the air path are designed according to the temperature and pressure requirements prevailing in the application, with sensors and actuators enabling system control and management. Applying optimized silencers, disturbing noises, e.g. from the compressor, can be reduced or even eliminated. Central system components such as humidifiers and heat exchangers positioned in charge air lines can be efficiently integrated into the overall system. Additional water separators to protect the turbine and prevent the discharge of liquid water from the tailpipe in the cathode exhaust path, as well as a reservoir, are advantageously integrated into the overall system using plastics technology. This holistic approach enables acoustically optimized and compact cathode air paths for PEM fuel cells.

   3. Ion Exchanger for Fuel Cell Coolant Loop as Customer Independent Market Product

      Simon Leininger, Andreas Wildermuth, Martin Bublinski, Marion Kauck

      Abstract

      Fuel cells will play an important role in reducing CO₂ emissions from transport, especially for heavy duty use cases. Current fuel cell systems have an electrical efficiency of ~50%. The remaining 50% of energy lead to heat generation, which have to be removed by the coolant loop at very high flow rate. In order to ensure a robust running system and to avoid electric shorts, the electrical conductivity in the fuel cell stack has to be kept low. By using the ion exchange technology, ions, which are released by several components in the coolant loop, are separated. In addition to highly-efficient ion removal, low pressure drop, mechanical robustness and costs are the challenges in the development of such ion exchangers. MANN + HUMMEL has developed a customer independent design, which is available as market product and covering most of current system requirements. This paper summarizes the product design and testing on ion exchange resin and product basis as well as the MANN + HUMMEL market product approach to reduce systems costs by standardization of components. Furthermore, a brief outline of a particle filter for a FC coolant loop is given.

7. Functional Layout

   1. Frontmatter

   2. Traceable and Efficient Validation of Mechatronic Products – A Conflict of Objectives?

      Simon Boog, Claas Kürten, René Maguin

      Abstract

      A great challenge in advanced engineering of mechatronic products in automotive applications is an efficient way to solve a conflict of objectives: On the one hand a high degree of flexibility is necessary due to frequent changes of requirements. On the other hand, keeping the traceability is required to guarantee Automotive SPICE (ASPICE) conformity. A particular challenge is the use of a heterogeneous verification tool landscape from various specialized suppliers. Most of the test runs require setups with flexibly scalable measurement devices from additional suppliers.

      MAHLE encounters this challenge by deriving project specific test cases out of a global requirements database which are used consistently at each system integration level of a mechatronic product. Simulations for Model-in-the-Loop (MiL) and Software-in-the-Loop (SiL) as well as Hardware-in-the-Loop (HiL) and dyno testing use the same test procedures out of a superordinate automation database which does not differentiate between the levels of system integration and maturity. This leads to standardized test procedures at all system-specific, model-based verification steps and allows a comparability of the results after standardized post-processing during advanced engineering. In this paper, for the first time a comparison of the results between multiple integration levels with heterogeneous tools is presented on the example of an electric traction drive system. Thus, quick V-model iteration loops with instant findings about the mechatronic product in development are enabled.

   3. Optimization of EMI Filter with Consideration of the Noise Source Impedance for DC/DC Converter

      Achim Vedde, Martin Neuburger, Konstantin Spanos, Hans-Christian Reuss

      Abstract

      Due to limited space and the focus on cheap and effective power electronics in automotive vehicles, the demand for fast switching devices has increased drastically. Such fast switching devices produce high electromagnetic interference (EMI) emissions which result in a gain of size and weight of EMI filters to comply with the electromagnetic compatibility (EMC) requirements. Due to uncertainties, the EMI filters used are often oversized. The goal of this paper is to show how an EMI filter is designed that fulfills the requirements in a way that smaller components can be chosen. Therefore, a passive EMI filter for a 400 V to 12 V DC/DC converter is created. A common method used to calculate the L and C filter components is to find the minimum required corner frequency and determine appropriate parts. However, this is a simplification of the filter design. In reality the source and load impedances also influence the design. Those impedances are often defined as 50 Ω. But the real source and load impedances of the system deviate from 50 Ω. In order to achieve effective filtering of the emissions, the knowledge of the noise source impedance is a very important factor in calculating the exact insertion loss of the filter. In this paper, the value of the impedance is estimated by analyzing the emission paths of the DC/DC converter. Then the influence of the impedance on the filter design is shown. With that knowledge, an improved EMI filter is created and demonstrated with measurements.

8. CO2-Strategies Passenger Cars for 2030

   1. Frontmatter

   2. Are Hybrid Powertrains the Right Solution to Meet EU-Emission-Targets in 2030

      Gerald Eifler

      Abstract

      In order to let even big and heavy SUV vehicles fulfill the emission targets of the future a PHEV-hybrid- drivetrain for propulsion is absolutely necessary. The restrictions of the new Euro-7-emission limits and the special WLTP-testing and -calculation regulations enforces special optimizing strategies of the hybrid drive which will be discussed intensively. On basis of WLTC- and RDE-measurements the presentation shows the optimum application of a hybrid drive which ensures an emission behavior within the legislation corridor.

9. Charging

   1. Frontmatter

   2. Energy and Automotive

      Ursel Willrett

      Abstract

      From the view of the energy provider integration of e-mobility into smart grid is important, which includes effective dynamic load management and the use of high voltage-batteries in the vehicle to store and feedback energy. The user expects sufficient and reliable charging points to recharge his electric vehicle everywhere and at any time. Professional solutions depend on local conditions and actual request for charging power and energy. For expansion of power grids several studies and recommendations exist already. If controlled charging is implemented expansion of the local distribution systems will be moderate. A communication system connects all partners in the system. It supports all functions for proper grid integration of electric vehicles and charging solutions: charging control, load management, authorization, billing system, bi-directional charging, e-roaming and value added services. Working together with enterprises in various sectors, the automotive industry is in a position to make a significant contribution to our transition to a clean-energy economy, with systems that also propel digitization. In doing so, we can effectively support our climate objectives at a national and international level. These system applications also offer great potential in the new business sectors of digitization.

   3. L3-BW: H2 Powered, Mobile Charging Station for Electric Vehicles

      Markus Kordel, Nicolas Muck, Tobias Schneider, Dirk Großmann, Jannik Briehl

      Abstract

      An ongoing market penetration of battery electric vehicles will demand charging infrastructure at places without access to energy grid (e.g. car parks at events, touristic infrastructure, campsites, parking lots at hiking spots). This demand exists for short time at events and seasonal at campsites. State of the art power supply are diesel powered energy sets to build up short term charging infrastructure. The DLR, together with Vector Informatik GmbH, develops a mobile charging station for electric vehicles, which can be refilled with gaseous hydrogen in order to provide local CO₂ free charging infrastructure without grid connection.

      This paper will present the concept of this charging station for applications in Baden-Wuerttemberg. Its features will be minimum two Type 2 charging plugs for electric vehicles and minimum two charging plugs for pedelecs, which will be integrated into a car trailer with maximum 750 kgs. The authors focus on the operating principle for the mobile charging station, the design and integration into the car trailer and the intelligent charging system. Finally, further applications will be derived from the “proof of concept” in the outlook.

   4. Reliability of Conventional Infrastructure in Context of Automated Driving illustrated by the SLAM Problem

      Marcel Vosshans, Cheng-Ting Tsai, Nils Mursinsky, Yichen Mao, Alexander Jäggle, Tobias Heisig, Thao Dang, Ralf Wörner

      Abstract

      With the appearance of the autonomy levels (according to SAE J3016), the responsibility of the driving ability is iteratively transferred to machine systems. An edge case is countered by a human driver with improvisation, while machines try to use known situations or given conditions to induce a human equivalent behavior. Such a system is based on landmarks like traffic signs, markings or structural conditions – the conventional road infrastructure. If there are not enough features to assign a situation, the system must fail. This infrastructural dependency, which future vehicles with increasing levels of autonomy must be able to cope with, was examined using the SLAM (Simultaneous Localization and Mapping) problem as an example. Two problems exist here: the landmark association and the diverging sensory inaccuracy. This contribution solves the association by proposing machine-readable traffic signs. The change of the conventional infrastructure allows the introduction of a conceptual fallback matrix, which in this context may lead to a decoupling of infrastructural dependency. This leads to the thesis that the vehicle of the future will no longer be defined by its engine power, but rather by its sensor technology and computing power to provide its autonomy.