21. Internationales Stuttgarter Symposium: Automobil- und Motorentechnik

Von Andreas Wagner

Band I
In einer sich rasant verändernden Welt sieht sich die Automobilindustrie fast täglichmit neuen Herausforderungen konfrontiert: Der problematischer werdende Rufdes Dieselmotors, verunsicherte Verbraucher durch die in der Berichterstattungvermischte Thematik der Stickoxid- und Feinstaubemissionen, zunehmendeKonkurrenz bei Elektroantrieben durch neue Wettbewerber, die immer schwierigerwerdende öffentlichkeitswirksame Darstellung, dass ein großer Unterschiedzwischen Prototypen, Kleinserien und einer wirklichen Großserienproduktion besteht.Dazu kommen noch die Fragen, wann die mit viel finanziellem Einsatz entwickeltenalternativen Antriebsformen tatsächlich einen Return of Invest erbringen, wer dienotwendige Ladeinfrastruktur für eine Massenmarkttauglichkeit der Elektromobilitätbauen und finanzieren wird und wie sich das alles auf die Arbeitsplätzeauswirkenwird.Für die Automobilindustrie ist es jetzt wichtiger denn je, sich den Herausforderungenaktiv zu stellen und innovative Lösungen unter Beibehaltung des hohenQualitätsanspruchs der OEMs in Serie zu bringen. Die Hauptthemen sind hierbei,die Elektromobilität mit höheren Energiedichten und niedrigeren Kosten der Batterienvoranzutreiben und eine wirklich ausreichende standardisierte und zukunftssichereLadeinfrastruktur darzustellen, aber auch den Entwicklungspfad zum schadstofffreienund CO2-neutralen Verbrennungsmotor konsequent weiter zu gehen. Auch dasautomatisierte Fahren kann hier hilfreich sein, weil das Fahrzeugverhalten dann –im wahrsten Sinne des Wortes - kalkulierbarer wird.Dabei ist es für die etablierten Automobilhersteller strukturell nicht immer einfach,mit der rasanten Veränderungsgeschwindigkeit mitzuhalten. Hier haben Start-upseinen großen Vorteil: IhreOrganisationsstruktur erlaubt es, frische, unkonventionelleIdeen zügig umzusetzen und sehr flexibel zu reagieren. Schon heute werdenStart-ups gezielt gefördert, um neue Lösungen im Bereich von Komfort, Sicherheit,Effizienz und neuen Kundenschnittstellen zu finden. Neue Lösungsansätze,gepaart mit Investitionskraft und Erfahrungen, bieten neue Chancen auf dem Weg derElektromobilität, der Zukunft des Verbrennungsmotors und ganz allgemein für dasAuto der Zukunft.

• Sprache: Deutsch
• Herausgeber: Springer Vieweg
• Erscheinungsdatum: 13. Mai 2021
• ISBN: 9783658334666

Buchvorschau

Mobility

© Springer Fachmedien Wiesbaden GmbH, ein Teil von Springer Nature 2021

M. Bargende et al. (Hrsg.)21. Internationales Stuttgarter SymposiumProceedingshttps://doi.org/10.1007/978-3-658-33466-6_1

MobiLab – The Mobility Living Lab at the University of Stuttgart

Wolfram Ressel¹  

(1)

University of Stuttgart, Keplerstr. 7, 70174, Stuttgart, Germany

Wolfram Ressel

Email: [e-mail]

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.

Keywords

MobilityCar-free campusMobility living lab

1 Introduction

MobiLab - under this headline the University of Stuttgart first developed a vision of a nearly car-free university campus Stuttgart-Vaihingen. But MobiLab is more than a vision. In this year the first measures take place to implement MobiLab, going along with several research activities. That´s why the initial concept of MobiLab was both: A visionary mobility concept for the campus Stuttgart-Vaihingen and a living lab for research, development and testing in the area of new mobility related technologies. MobiLab in its first phase was the result of an idea competition on an emission-free campus held by the Ministry of Science, Research and Art of the State of Baden-Württemberg. In this idea competition the University of Stuttgart got awarded in the category University in an Urban Context.

What forms finally this innovative mobility and research concept? The basic idea of MobiLab 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 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 forms a multifaceted living lab with the three main research topics research vehicle, research street and research multi-storey car park.

In this moment MobiLab is in its second phase, financed for additional two years by the Ministry of Science, Research and Art of the State of Baden-Württemberg to act as a lighthouse for the transformation to car-free university campuses.

As part of these lighthouse activities Mobilab widened its perspective and is now covering the whole University of Stuttgart. The overall approach for the University is led by the objective to avoid the release of mobility-based CO2-emissions of the University of Stuttgart (daily mobility of students and employees (commuting), study trips, business trips) until 2035 completely.

With this MobiLab is now 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.

The Offer of the Mobility Living Lab Campus Stuttgart-Vaihingen.

2 Climate Neutrality 2035

2.1 Concept

The objective to reduce the mobility-related release of CO2 as much as possible and to reach climate neutrality until 2035 is part of the sustainability strategy of the University of Stuttgart and is implemented in the strategic development plan of the University.

Figure 1 shows the approach intended to be followed with respect to mobility (daily mobility of students and employees (commuting), business trips).

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Fig. 1.

Climate target 2035 mobility

To reach the settings for the different means of transport the University of Stuttgart intends to implement the following measures and incentives:

Daily mobility of students and employees (commuting)

Reduction of car trips, e.g. with parking management, support of carpools, support of cycling, car-free campus Stuttgart-Vaihingen.

Incentives to use electric vehicles, e.g. by offering loading stations, preferential parking spaces for electric vehicles.

Business trips

Business trips with cars only allowed with electric or hydrogen powered cars.

No flights anymore in Germany, strict rules for flights in Europe, reduction in the overall number of flights.

Additional compensation of the remaining release of CO2 due to flights.

2.2 The Mobility Manager at the University of Stuttgart

As a first step to change the mobility related to the University of Stuttgart with the beginning of 2021 the position of a Mobility Manager at the University of Stuttgart was established, financed in a first step by MobiLab. The main task of the Mobility Manager is to address the students and the employees of the University of Stuttgart and to accompany them on the way to reduce the release of CO2 and to find sustainable ways of mobility. This has to be done in an open and communicative approach. Additionally, the Mobility Manager supports MobiLab.

The first activity of the Mobility Manager was to launch a survey among the students and employees to understand their needs for mobility, their mobility behavior and how they rate several measures to shift their mobility to a more sustainable manner.

In 2022 the University of Stuttgart will offer its students and employees an app-based service to form carpools. This will be done in close co-operation with other big employers in Stuttgart, aiming also to form comprehensive carpools.

3 The Car-Free Campus Stuttgart-Vaihingen

3.1 The University Campus Stuttgart-Vaihingen

The campus Stuttgart-Vaihingen of the University of Stuttgart is located in the South-West of Stuttgart, the capital of the state of Baden-Württemberg (see Fig. 2). On three sides it is surrounded by green, but in the East, it adjoins several smaller residential areas. Therefore, it is not possible to enlarge the campus beyond its present boarders even if there is a high pressure to grow. The Campus Stuttgart-Vaihingen is one of the two main sites of the University of Stuttgart.

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Fig. 2.

Location of the campus Stuttgart-Vaihingen

Besides the University of Stuttgart, the HdM (Hochschule der Medien), several Fraunhofer-institutes, the site Stuttgart of the German Aerospace Center (DLR) and numerous other institutions are located on the campus. Additional there is a huge number of student dormitories in combination with several amenities of student´s life. In total there are around 23.000 students studying and nearly 7.000 employees working on the campus.

In public transport the regional train (S-Bahn) station Universität is located centrally offering short travel times to both the main station and the airport of Stuttgart. In road traffic the campus is directly linked to both the regional motorway network and to downtown Stuttgart. On the campus nearly 4.000 parking spaces are available.

3.2 The Mobility of Students and Employees

To understand the daily travel behavior from home to the campus and back home as well on the campus of both the students and the employees at the beginning of the summer term 2019 (April 2019) an online survey was conducted including all students and employees on the campus.

The students travel in average on 3.7 days per week to the campus. The average trip length from their place of residence to the campus is 17 km, resulting in an average travel time of 43 min.

The employees are working in average on 4.3 days per week on the campus. The average trip length from their place of residence to the campus is around 19 km, resulting in an average travel time of 40 min.

The campus is good accessible by public and private transport. The good accessibility in public transport is reflected in the mode choice of the students and the employees (s. Fig. 3). The students use mainly public transport which carries 80% of their transport performance. The employees use public and private transport to the same extent. But in comparison with the residents of Stuttgart or the State of Baden-Württemberg the car usage is clearly lower.

../images/510426_1_De_1_Chapter/510426_1_De_1_Fig3_HTML.png

Fig. 3.

Modal split of students and employees

3.3 Concept

Overview

The vision of MobiLab is to transfer the campus Stuttgart-Vaihingen to a more or less car free campus. All parking will be concentrated in a central multi-storey car park on top of the B14 motorway at the Southern edge of the campus. This multi-storey car park as well as the already existing regional train station Universität will be connected to the campus by autonomous shuttles. An e-scooter rental system on the campus will support the shuttles and improve the mobility on the campus. To connect the campus to neighboring destinations the bike rental system RegioRadStuttgart was introduced on the campus in 2020.

The area covered by the former parking facilities on the campus will be partly used for new buildings and partly to improve the urban quality of the campus to make it more attractive for employees and students.

There are many components necessary to introduce this mobility concept on the campus Stuttgart-Vaihingen which still must be explored and tested. Here MobiLab is changing to a living lab, the MobiLab Living Lab, where all necessary technologies will be provided. Furthermore, the MobiLab Living Lab will cooperate with many other research activities inside and outside of the University of Stuttgart and offer the campus Stuttgart-Vaihingen as a test bed. Doing this MobiLab is also acting as an incubator for start-ups. A first start-up is already founded based on MobiLab.

To introduce the vision of MobiLab the University of Stuttgart integrates all important players on the campus in the development and implementation of MobiLab: the various universities, research institutes and service providers as well as the students, the employees and visitors. The emission- and car-free campus can only get reality by an interdisciplinary cooperation of different faculties, like transport planning, automotive engineering, electrical engineering, renewable energies, urban planning or social sciences, and an active integration in teaching.

Parking

Figure 4 shows the 3-stage approach of MobiLab related to parking.

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Fig. 4.

3-stage approach parking

In a first stage, most likely in spring 2022, the parking management will be introduced on the campus. Parking management means that students, employees and visitors will have to pay a parking fee, either as a monthly flat rate or as a daily parking fee. The monthly parking fee for the students will be cheaper than the fee for the employees. Following the idea of MobiLab not all the scattered numerous car parks will be administered but the whole campus will be seen as one big car park. Therefore, at the three road entrances to the campus barriers will be installed (s. Fig. 5). Behind the barriers all public streets will be closed and dedicated to private streets.

../images/510426_1_De_1_Chapter/510426_1_De_1_Fig5_HTML.png

Fig. 5.

The three entrances to the campus Stuttgart-Vaihingen

This is already a first important step to the car-free campus. All external car traffic, not related to the campus, will be excluded from the campus.

As table 1 shows, after the implementation of stage 1 of the parking management a parking demand of around 2.900 parking lots remains. Therefore, in stage 2 (not earlier than 2023) two multi-storey car parks will be built as an interim solution until the central parking on top of the B14 motorway will be built which is expected not earlier than 2030.

Table 1.

Parking demand (no. of parking lots)

All multi-storey car parks will be designed as research car parks:

Mobility hub in the ground floor (stop of Campus Shuttle, RegioRadStuttgart docking station, bicycle parking, bicycle maintenance area, area for e-scooter rental).

Charging for electric cars (plug-in, inductive charging).

Solar panels on the roof, interim storage of electric energy and demand management.

The two interim multi-storey car parks will be designed in such a way that they can be easily dismantled.

Cycling

In cooperation with the City of Stuttgart, the regional bike rental system.

RegioRadStuttgart was expanded to the campus including nine docking stations and offering 72 bicycles and pedelecs. This will increase the accessibility of the campus by bike. The implementation of RegioRadStuttgart on the campus Stuttgart-Vaihingen is the result of a strong initiative of the student´s association stuvus.

In general, the infrastructure for cycling on the campus Stuttgart-Vaihingen has to be improved. First of all, there is a lack of clearly indicated cycle paths. MobiLab will help via the implementation of the parking management scheme, where all public streets will be closed and dedicated to private streets. The second issue to be addressed is parking for bicycles. Here MobiLab intends to build demonstrators for different types of bicycle parking facilities, including at the high end an automatic bicycling parking tower with a capacity of around 120 bicycles.

But there is a need for actions not only on the campus but also in the access to the campus. The campus Stuttgart-Vaihingen has to be integrated in the local and regional cycling networks, especially to the planned cycle highway network, and at least one completely paved cycling connection from downtown Stuttgart to the campus is necessary.

E-Scooter System Campus Vaihingen

Researchers at the University of Stuttgart are currently developing a self-driving autonomous e-scooter (s. Fig. 6). These e-scooters use an advanced control system to drive to the next port of call without the need for a driver. A distribution algorithm optimizes the availability of the e-scooters on the campus. In detail the autonomous e-scooters fulfill the following functions:

Balancing.

Autonomous driving without passenger.

Active navigation.

Optimal distribution of the fleet.

Autonomous driving to charging stations.

Automatic parking with automatic charging.

../images/510426_1_De_1_Chapter/510426_1_De_1_Fig6_HTML.png

Fig. 6.

Simulation of autonomous e-scooters (with and without passengers)

As soon as they are available the autonomous e-scooters will be integrated in the e-scooter rental system offered on the campus. An autonomous e-scooter will replace ten conventional e-scooters in such an e-scooter rental system.

For parking and charging of the autonomous e-scooters a bicycle parking tower (s. chapter Cycling) will be adapted to the specific needs of the autonomous e-scooters.

Campus Shuttle

Intelligent autonomous shuttles connect the central parking facility and the regional train station with the campus. This scenario, named Campus Shuttle, will be real on the campus Stuttgart-Vaihingen in future.

Campus Shuttle integrates different sizes of autonomous (mini) buses, which may have a capacity of six, twelve or 40 seats. Actually, the University of Stuttgart offers the campus Stuttgart-Vaihingen as a test bed for field tests with autonomous shuttles and intelligent shuttle services.

In a first step a traditional line operation will be implemented with a fixed time table and several stops along a circle around the campus (s. Fig. 7). In a second step an on-demand service will be tested. To call the shuttle via smartphone a specific app will be implemented.

../images/510426_1_De_1_Chapter/510426_1_De_1_Fig7_HTML.png

Fig. 7.

Alignment campus shuttle

Additionally, the shuttle will be used to test several approaches in the area of energy storage and electric actuation. Some parts of the so called research street will be prepared for inductive charging while driving.

4 The Mobility Living Lab Campus Stuttgart-Vaihingen

The University of Stuttgart shapes with MobiLab the vision of an emission-free campus Stuttgart-Vaihingen. The campus will be a research campus - the Mobility Living Lab -, where climate-neutral, electric and intelligent mobility will be tested (s. Fig. 8). This Mobility Living Lab will be formed by the components research vehicle, research street and research multi-storey car park. The Mobility Living Lab offers students, lecturers and researchers a versatile test bed in the areas of sustainable mobility based on renewable energy, of autonomous driving and of artificial intelligence. It forms a living lab for diverse institutes from transport planning, automotive engineering, computer science, electrical and information engineering and social sciences.

../images/510426_1_De_1_Chapter/510426_1_De_1_Fig8_HTML.png

Fig. 8.

The mobility living lab campus Stuttgart-Vaihingen

The research vehicles will be the autonomous e-scooter and the autonomous shuttle.

Due to the innovative concept to introduce parking management as an area-wide approach behind the barriers all roads on the campus will be part of the research street and will be open for several research activities. These activities include the implementation of equipment for inductive charging, but also field tests of the co-existence of traditional bicycles, autonomous e-scooters, autonomous shuttles and traditional vehicles on the same street.

The research multi-storey carparks will be equipped with several specific features as already described in chapter parking.

Again, all research activities are not limited to the basic ideas of MobiLab. The Mobility Living Lab MobiLab offers the campus Stuttgart-Vaihingen for all interested in mobility-related research.

5 Outlook

The implementation of MobiLab already started. This is done in a strong cooperation with the mobility concept which in parallel is under elaboration in this moment. The mobility concept deals with the present mobility and transport needs on the campus Stuttgart-Vaihingen to be solved, while MobiLab shapes the future of the campus. The mobility concept integrates the activities of MobiLab and prepares their implementation.

The parking management on the campus Stuttgart-Vaihingen will start in spring 2022. It is strongly influenced by MobiLab and forms an important first step for the implementation of MobiLab.

RegioRadStuttgart is already implemented on the campus Stuttgart-Vaihingen.

The first prototype of the autonomous e-scooter is already under operation and able to stabilize itself while driving.

In 2022 the operating test of the campus shuttle will start.

MobiLab itself is an inter-disciplinary research network, including the administration of the University of Stuttgart. Now MobiLab has to be integrated in the University of Stuttgart in a broad approach aiming to connect all mobility and transport related research activities within the University of Stuttgart.

In parallel MobiLab is also integrated in several European networks also offering them the campus Stuttgart-Vaihingen as a Mobility Living Lab and a test bed for a wide variety of mobility related test applications.

But also, in teaching MobiLab offers many possibilities to get integrated in lectures, exercises or case studies. First master theses in the framework of MobiLab are already finished.

MobiLab is integrated in the sustainability-related activities of the University of Stuttgart giving advice to the administration of the University but also supporting students and researchers with their ideas.

Additional MobiLab widens its perspective and will take care for the whole University of Stuttgart. In this moment a monitoring instrument for both daily trips to the university and back home and for business trips of the employees is available. In a first step regular reports will be published to the students and employees to raise awareness on the respective mobility behavior. In a second step the University of Stuttgart will publish verifiable objectives to reduce the ecological footprint of the university and will take measures to fulfill these objectives.

MobiLab gives already advice for new buildings. It recommends to provide parking facilities for bicycles (plus showers for the cyclists!) and areas for the e-scooter rental system or to make as much as possible use of the roof or the façade to produce renewable energy which can be used for charging of electric vehicles.

All these activities opened the awareness of the University of Stuttgart to limit such considerations not only on mobility but also to work on the sustainability of the stock of existing and planned buildings.

© Springer Fachmedien Wiesbaden GmbH, ein Teil von Springer Nature 2021

M. Bargende et al. (Hrsg.)21. Internationales Stuttgarter SymposiumProceedingshttps://doi.org/10.1007/978-3-658-33466-6_2

Self-Propelled Trailers – An Approach to Type Approval

Rüdiger Freimann¹  , Sebastian Maier² und Alessandro Sannia¹

(1)

Erwin Hymer Group SE, Holzstraße 19, 88436 Bad Waldsee, Germany

(2)

FKFS, Pfaffenwaldring. 12, 70569 Stuttgart, Germany

Rüdiger Freimann

Email: [e-mail]

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.

Keywords

TrailerPropelled trailersElectric vehiclesEV reach

1 Introduction/Motivation

Electric powered vehicles today are optimized to handle electric power highly efficiently. They feature low loss bearings and aerodynamic design. And they have to carry additional weight at about 10 kg/kWh installed battery capacity. With the resulting in average to 700 kg on top. Thus by often working in an old chassis platform and brake set-up taking away towing capacity. Maybe at least this is why we see today trailer hitches only with high power cars often even with reduced towing capacity in the order of the battery weight.

Towing a caravan is a real challenge for EVs. The bulky caravan completely spoils all aerodynamic achievements of the towing car. Published tests with an electric vehicles towing a caravan are showing a cut down of the reach nearly by halve [1]. To compensate for this loss of reach, the battery capacity simply has to be doubled. But which car manufacturer has doubled the fuel tank, just to be able to tow? Our proposed solution is to put the additional required motive power and energy where and when it is needed, on the trailer. Once we had assumed that, there were many other advantages on the hand. An autonomous mover function on the camp ground, a traction support in rough terrain, a trailer stability system by torque vectoring, a zero emission energy autarky in standstill or while driving, and others more. Prototypes are already running and are proving our assumption. Getting a type approval is the next big step.

2 Trailer Type Approval Today

Homologation framework and requirements are not harmonized across the world, de-spite decades of efforts. The concept of trailer itself proves to be very different from Europe to USA, where the first provides a very strict and binding regulation and the second a much more open one.

2.1 European Union

The homologation requirements for motor-vehicles and trailers are defined in the European Union by Regulation 2018/858/EU.

Trailers are defined as "any non-self-propelled vehicle on wheels designed and constructed to be towed by a motor vehicle"¹.

They are divided in 4 categories according to their mass (Gross Vehicle Weight when fully laden)²:

O1 up to 750 kg

O2 above 750 kg and up to 3,500 kg

O3 above 3,500 kg and up to 10,000 kg

O4 above 10,000 kg

Further criteria are defined to categorize the trailers also with regards of their design and usage (for instance, the trailer-caravans are defined as special purpose vehicles under the code SO and must also comply with the ISO 3833:1977 standard).

Within a common definition of O category vehicle, each category must comply with different technical requirements. Exceptions are also defined for special purpose trailers.

So far, the EU Regulations are still valid in the United Kingdom (being converted into national laws by the Great Repeal Act after the Brexit) and are generally implemented into national laws also by the EFTA Countries³ and usually recognized by many other non-European countries, as Turkey.

2.2 United Sates

Vehicle construction and safety requirements are defined in the US by a set of Federal Motor Vehicle Safety Standards (FMVSS), issued by the NHTSA (National Highway Traffic Safety Administration).

The definition of trailer is also provided by an FMVSS, as a motor vehicle with or without motive power, designed for carrying persons or property and for being drawn by another motor vehicle.⁴

Similarly, also the specific definition of trailer-caravan doesn’t make any reference to the presence of motive power: Recreation vehicle trailer means a trailer, except a trailer designed primarily to transport cargo, designed to be drawn by a vehicle with motive power.

The biggest difference with the European (UN ECE) definition is therefore that the US already consider that a trailer may have its own motive power.

3 Electric Driven Trailer/Caravan [2]

3.1 Functional Requirements

For the development of our e-caravan, several functional requirements needed to be considered. A full reach loss compensation has been a primary target. A trans-alp journey has been chosen as a representative route to define the requirements for the electric powertrain and the battery capacity. Simulations have shown that the combined energy consumption of car and trailer for a trip between Isny (Germany) and Arco (Italy) will amount to approximately 146 kWh. In addition to 80–100 km/h travel speed, a torque vectoring function shall allow the caravan to increase the stability of both car and trailer while driving. When moving on its own on the campground, the caravan should be able to mount curbs.

Another important requirement for a quick market approach is an independence of the trailer’s control system from the towing vehicle: Both, all necessary sensors including the trailer motion control (TMC) and the actuators need to be located in the caravan. This way, the e-caravan is compatible with most all towing vehicles, including older cars.

The addition of a battery electric powertrain opens up several other new use cases for the trailer. One of them is an integration of the e-caravan into home energy concepts as a storage device for superfluous energy, e.g. from solar collectors during peak times. Afterwards, the energy can be released back into the house’s power supply or fed into the grid. This requires charging electronics that are capable of managing bidirectional power flows and of communicating with the wall box. Another benefit of the battery is the caravan’s autarky from the power supply on the trip or at campgrounds. Assuming up to 1.5 kW of average electric consumption, the planned setup of the battery can last for several days of all electric autarky. This could be further extended by installing solar panels on roof and awnings.

3.2 Electric Drive Concept

In line with its Next Generation Mobility strategy, ZF aspires to offer electric mobility solutions for vehicles of all kinds. This includes even the electrification of trailers. As early as 2016, the Group constructed an innovation prototype for agricultural machines. As part of the development process, it retrofitted a drive axle equipped with two electric motors normally used in city buses for a tractor-trailer. The goal here was to improve traction management, in particular, using the single electric drive and to lend the tractor trailer greater tractive force in difficult terrain, such as steep inclines or in mud, without having to increase performance in the tractor drive. ZF has now transferred this expertise to the development of the e-caravan.

The detailed requirement profile from above provided the data to configure the ideal drive. In the case of e-caravan, the main task is to actuate the trailer or to brake it in such a way that the target traction on the trailer hitch is maintained at all times. Additional software components have to control a torque vectoring for stability control while driving and independent maneuvering at the campground.

In addition to the electric drive system, ZF also provides the associated control concept for e-caravan. Its fundamental purpose is to control the torque for the two individually adjustable electric motors. An additional challenge was to be independent of the towing vehicle and therefor act as a small standard trailer. Accordingly, only those towing car signals are available to the control system, which are transmitted via the standard trailer connector. A central ECU in the caravan called the Trailer Mobility Controller (TMC) generates the target values and vectors for torque control using the data from a sensor set which monitors the forces between the trailer and the towing vehicle.

3.3 Motion Controller

Such a control has never existed before, which is why it requires the development of a new sensor. The control goal lies in minimizing the forces on the vehicle’s trailer hitch. (See Fig. 1) The following general conditions must be met in the control algorithm:

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Fig. 1.

Trailer coordinate system

In longitudinal direction, the trailer should always be in drag (FH,x).

In transverse direction, no forces should be generated on the towing vehicle in order to keep additional side forces the rear car axle low (FH,y)

In the vertical direction (FH,z), the car rear axle load and lift forces have to be limited in order to protect the hitch structure or to guarantee a minimum side force at the rear wheels.

Accordingly, a multi-variable controller is necessary to adjust the force on the trailer hitch as follows:

3.4 Over all Vehicle Structure and Package

Taking all package, function and safety considerations into account, the e-Caravan structural concept (see Fig. 2) has to offers the following features:

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Fig. 2.

Schematic chassis of the eCaravan

A lightweight safety frame with a low center of gravity and a double frame (4 longitudinal beams) for better floor support and further weight reduction in the floor sandwich characterize the chassis.

The battery position can be adjusted to a specific floor plan, allowing a better weight distribution in the caravan.

In order to ensure a production line neutral assembly that matches a standard chassis, powertrain and battery will be pre-manufactured.

4 Activity of the VDA. Definition of propelled axle in a trailer: modifications to Regulations and Directives of the UN ECE and the EU

The UN ECE (United Nation Economic Commission for Europe) within the 1958 Agreement does the definition of the different wheeled-vehicle categories. However, none of the current definitions includes a trailer with propelled axle(s).

The most recent orientation of the European Union is to avoid the issue of new technical regulations and exploit as much as possible the existing UN ECE Regulations, bringing them into the European legislation by implementing acts.

Therefore, the introduction of a new concept of wheeled-vehicle – i.e. a trailer with propelled axle(s) – shall first be implemented by UN ECE and later adopted by the EU.

Changes of both UN ECE Regulations and EU Directives are discussed upon request of a member Country. In this case, the input comes from Germany and the discussion among the representatives of the manufacturers is held at the VDA.

4.1 The VDA

The VDA – Verband der Automobilindustrie (Association of the Automotive Industry) represents the main German manufactures of vehicles, automotive components and services. It’s member of the ACEA⁵ and is the privileged counterpart of the German government in the motor-vehicle matters.

The VDA is also member of the CLCCR⁶ and in this role is coordinating the development of a new regulatory definition for trailer with propelled axle(s).

4.2 UN ECE Regulations

Vehicle Regulation is one of the fields of competence of UN ECE, that support their definition and implementation within the so-called WP.29⁷, The WP.29 is participated by all the European (EU, EFTA and the UK) countries plus other non-EU countries, sharing the common target to reach a global harmonization among the wheeled-vehicles regulations, as Turkey, Japan, South-Korea, Australia. The basic principle is the mutual recognition of the agreements among the Countries, which are defined as Contracting Parties.

The definitions of wheeled vehicles are provided in the R.E.3⁸ and the S.R.1⁹.According to the both of them Trailer means any non-self-propelled vehicle, which is designed and constructed to be towed by a power driven vehicle.

The first step to introduce the concept of Trailer with Propelled Axle(s) is therefore to amend those definitions, deleting the attribute of non-self-propelled and adding the principle that a trailer is primarily designed to be towed, meaning that under certain specific condition it can move independently.

The proposal from the VDA will therefore be to amend the definition in the way that Trailer means any vehicle, which is primarily designed and constructed to be towed by a power driven vehicle.

This proposal will be introduced by the German Ministry of Transportation (as a representative of a Contracting Party of the 1958 Agreement) at the UN ECE GRSG¹⁰.

4.3 EU Regulations

The Regulation 2018/858/EU, defining the homologation requirements in the European Union, copies the same UN ECE definition: ‘trailer’ means any non-self-propelled vehicle on wheels designed and constructed to be towed by a motor vehicle […]¹¹.Once the UN ECE R.E.3 and S.R.1 will be amended, a similar modification shall be done also to the Reg. 2018/858/EU. Again Germany, as a Member State of the European Union, will have to propose this amendment.

The individual vehicles documents, whose structure is also defined by the Reg. 2020/683/EU¹², will require modifications as well. In fact, today a trailer doesn’t display data that will be relevant in the future as, for instance, power and torque of the motor(s) and it’s also crucial that an e-Trailer can be easily and clearly recognized.

5 e-Trailer: Legal Definition and Approval Requirements - Initiative of the BEM

As part of an initiative of the BEM (Bundesverband eMobilität, Federal Association for eMobility), as well as numerous cooperation partners from the motor vehicle and caravanning industry, efforts are currently being made to create the necessary approval requirements. The following gives a condensed overview of the current work progress.

5.1 Minimum Technical Requirements for an e-Trailer

In order to create a legal framework a definition of an e-Trailer was needed. The idea here was to make as few regulatory provisions as possible so as not to create unwanted restrictions with regard to possible technical implementations later on.

Based on the existing trailer categories O1-O4, in which trailers are subdivided according to weight¹³, we suggest an attribute to the categories O1-O4 for identifying e-Trailers. As a working title we like to introduce an OXe. (O1e < 0.75ton | O2e 0.75–3.5ton | O3e 3.5–10ton | O4e > 10ton). The suggested minimum requirements for e-Trailers are as follows:

Energy storage: An e-Trailer needs its own energy storage.

Powertrain: An e-Trailer needs its own powertrain.

Power requirement: A minimum continuous engine power of 5–7.5 kW / ton maximum weight allowed is required.

Energy requirement: A minimum continuous power of 0.2 kWh / kW engine power installed is required. (Categories O1e-O3e) A value of 0.1 kWh/ kW is required for Category O4e.

Behavior: An e-Trailer must not actively push and thereby trigger dangerous situations in terms of driving dynamics.

Said limits are chosen in a way, that Regulations that could later prevent certain technical implementation options are deliberately not included in the definition of an e-Trailer. This includes:

How to charge the system (which plug, wired/cable less, dc/ac charger)

Power train topology (one engine, wheel individual engines, number of powered axles)

Technical powertrain properties (high/low voltage drive system, power train safety features)

5.2 Advantages, Possibilities and the Proposed Principle of Weight Reduction…

e-Trailer enable the implementation of many interesting new possibilities, like e.g. increased comfort and new safety features, reduction in fuel consumption and CO2 emission of the towing vehicle, all due to its active drive system. Further possible is an autarkic use due to its own energy storage, use of weaker towing vehicles, use as energy buffer for the power grid and many more. In order to facilitate the market adoption of the e-Trailer category, thus also aide e-Mobility in general and ensure competitiveness with conventional trailers we propose the principle of weight reduction.

The idea behind it is as follows; due to the additional drive train and energy storage, the curb weight of the e-Trailer is significantly higher than that of conventional trailers. However, employing its active drive system, the e-Trailer will behave in fact like a much lighter trailer thus allowing a categorization in the newly proposed e-Trailer categories O1e-O4e. (In Sect. 5, we explain the needed process of validation and proof of safety in more detail.) Now for reduction, a weight is calculated using a formula that takes into account the built-in battery capacity and drive power. The result of which (G) then is deducted from the weight of the e-Trailer, which puts it in the same trailer category as a comparable conventional unpowered trailer. We propose the following equation:

$$ \frac{{BAT. ENERGY \left[ {kWh} \right]}}{{0{,}12\frac{kWh}{{kg}}}} + 22*\sqrt {DRV. POW.\left[ {kW} \right]} + DRV. POW. \left[ {kW} \right] = G\left[ {kg} \right] $$

(1)

Between the available energy and actual battery weight, we assume a linear relationship. Typical industrial values for the energy density are between 90-150Wh/kg. Our value represents the mean, this way more advanced technical solutions, which are able to achieve an energy density above average, receive a kind of weight bonus. For the second term, the engine power density, we assumed a quadratic relationship, which inverted results in a square root. The last term represents the weight of the inverter, cables and the cooling system, both assumed proportional to the engine power. Examples are as shown: For e.g. the lower end, with 10 kWh energy and 10 kW of power we get 160 kg of reduction. A larger system employing 100 kWh of energy storage and 100 kW of engine power, results in 1150 kg reduction. In both cases, the results show a good fit with existing systems.

5.3 … Consequences for Drivers Licenses and Allowed Towing Weights

As explained before, by factoring in the powertrain components and deducting their weight equivalent from the trailer, we effectively reduce the curb weight of the trailer. By doing this we touch regulations regarding driver license rules and allowed towing weights. The following diagram shows the described relationship.

As seen in the examples (see Fig. 3 blue and red dots), in every case the principle of weight reduction re-categorize the vehicle combination into a new driver license category. This allows a much larger proportion of drivers to actually eTrailers and enable a usage like normal trailers.

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Fig. 3.

Maximum allowed weight for vehicle, trailer, and driver license categories

6 Simulation Aided Proof of Safety

6.1 Test-Rides: Gathering Real-World-Test-Data of Trailer Driving Behavior

Getting a benchmark of state of the art trailers, an extended test procedure was carried out, using test ride scenarios with longitudinal, lateral and combined dynamic. Therefor the same trailer, without power train but with the same gross weight and center of gravity was tested. Trailer and towing vehicle were equipped with all required sensors for a comprehensive signal recording of important physical quantities (see Fig. 4).

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Fig. 4.

Car-trailer test setup – set of measured sizes

Knowledge and a benchmark about trailer driving behavior has been acquired.

6.2 Modelling: Trailer-Model Creation in CarMaker

As a base of simulation, a very detailed replication of the trailer without and with the electrical drive train was modelled in CarMaker (see Fig. 5). Central steps where:

Modeling and integration of the electric drive train into the trailer model.

Parameterization of parameters like dimensions, masses, moments of inertia, aero, chassis, tires, …

To generate reliable simulation results an extensive and precise tuning & validation process is necessary.

../images/510426_1_De_2_Chapter/510426_1_De_2_Fig5_HTML.png

Fig. 5.

Creation of the trailer model in CarMaker

7 Model Validation: Trailer-Model Tuning Process

The tuning & validation process for the created simulation model follows a detailed procedure shown below (see Fig. 6). First step is the simulation of all previously executed real world test-rides and second, comparing the result with measurement data. Now by tuning of the trailer parameters a model match is the goal.

../images/510426_1_De_2_Chapter/510426_1_De_2_Fig6_HTML.png

Fig. 6.

Workflow of the realized model tuning process.

CarMaker Model is successfully validated.

7.1 Proof of Safety: Combined Simulation & Test Ride approach

Authorities require a series of driving safety tests to confirm that the vehicle is ready for approval. These contain a series of test drives following established ISO standards. A common example here would be the Double Lane Change Maneuver. However, the extensive use of simulations of the towed trailer offer considerable advantages:

Extreme driving conditions and dangerous maneuvers can be simulated

Flexible and extended test design & test variation are possible in simulation

Simulations are an excellent advanced tool for function development

Having satisfactory results of the simulations, only a few test drives are needed to confirm the safety simulations.

As shown in the following figure (see Fig. 7), a subset of only some selected support points and boundary values are used as confirmation for the correctness of the simulations. The idea here was to choose those points, mixing DOE methods while still considering selected simulation results and given real world limitations for the test rides. That way we can ensure the best possible effort to result ratio while safely proofing safety.

../images/510426_1_De_2_Chapter/510426_1_De_2_Fig7_HTML.png

Fig. 7.

Principle of the combined simulation and test ride approach

8 Summary and Outlook

To efficiently use motion power and energy when and where it is needed, is a significant contribution to greenhouse gas reduction [3]. But bringing a new type of vehicles or even a significant change in a vehicle type definition into traffic is a challenge and that it is not only for autonomous driving. While in the US motion power on a trailer is included in the trailer definition, Europe explicitly restricts trailers to non-propelled vehicles. German initiatives in VDA and BEM are trying to overcome this ancient regulation within the next few years.

Finally implementing standards for a new type of vehicles will take some time, but to contribute to a global CO2 reduction we have to accelerate as much as we can. Before we release this new technology into traffic, we have also to consider how to monitor this new system in use and over time. A regular technical inspection by trusted authorities should be mandatory (TÜV-Regeluntersuchung). Firstly for the motion power devise to be kept compliant with the set conditions and safe mode operation but also to stay efficient for the CO2 reduction target.

References

1.

Frydenlund, S.: Norwegian electro mobile forum: 2019 – The very first test of three electric cars with caravans. https://​elbil.​no/​the-very-first-test-of-three-electric-cars-with-caravans/​. Accessed 10 Jan 2021

2.

Rüdiger, F., Gumpoltsberger, G., Gillich, U., Kaiser, R.: Stuttgarter Symposium 2019 – „New Vehicle Concepts for Mobile Vacation". Stuttgart, February 2019

3.

Bergk, F., Biemann, K., Kämper, C., Kräck, J., Knörr, W.: ifeu – Institut für Energie- und Umweltforschung Heidelberg GmbH - „Klimabilanz von Reisen mit Reisemobilen und Caravans", Heidelberg, August 2020

Fußnoten

1

Reg. 2018/858/EU, Art. 3, Point 17.

2

Reg. 2018/858/EU, Art. 4, Point 1, letter (c).

3

Norway and Switzerland.

4

Title 49 § 571.3.

5

Association des Constructeurs Européens d'Automobiles, or European Automobile Manufacturers Association.

6

International Association of the Body and Trailer Building Industry.

7

Working Party 29.

8

Consolidated Resolution on the Construction of Vehicles, Art. 1.5.

9

Special Resolution No. 1 concerning the Common Definitions of Vehicle Categories, Masses and Dimensions, Annex 1, Art. 2.

10

Working Party on General Safety Provisions.

11

Reg. 2018/858/EU, Art. 3, Point 17.

12

Reg. 2020/683/EU, Annex II, Part 1.

13

Reg. 2018/858/EU, Art. 4, Point 1, letter (c).

Pollutants I

© Springer Fachmedien Wiesbaden GmbH, ein Teil von Springer Nature 2021

M. Bargende et al. (Hrsg.)21. Internationales Stuttgarter SymposiumProceedingshttps://doi.org/10.1007/978-3-658-33466-6_3

Preview on Future Developments of Non-exhaust Emissions

Christof Danner¹   und Andreas Pein¹

(1)

AVL LIST GmbH, Hans-List-Platz 1, 8020 Graz, Austria

Christof Danner

Email: [e-mail]

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.

Keywords

Non-exhaust emissionsBrake dynoPMPLegislationTesting

1 History

Despite the significant imposition of non-exhaust emissions on public health, very low public policies target them directly. While emission standards for exhaust particles from motor vehicles are becoming more stringent worldwide, non-exhaust PM emissions are largely unregulated. As a result, the proportion of PM emissions from non-exhaust sources has increased in recent years due to the significant reductions in PM from exhaust emissions over this period. Non-exhaust emissions are expected to be responsible for the highest majority of PM emissions from road traffic in future years (Fig. 1).

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Fig. 1.

Motivation for the regulation of non-exhaust emissions, Source: Euro Brake 2019 (German Environment Agency), AVL, Fotolia

The work on the Brake Emission Legislation has already started in June 2014 with the informal document GRPE-69–23. Within this document UNECE (United Nations Economic Commission for Europe) agreed with the GRPE (Working Party on Pollution and Energy) decision to assign follow-up activities related to the emissions of particles from tires and brake wear to the PMP (Particle Measurement Program) informal working group. The following main work items have been identified:

i)

Investigation of typical driving patterns

ii)

Development of recommended measurement techniques and sampling procedures

The PMP group was therefore further divided in two Task Forces (TFs). TF1 was responsible for the development of a representative brake cycle, whereas TF2 is responsible for the measurement methodology. The results from TF1 have been published already in July 2018, describing the novel braking cycle in detail (Fig. 2).

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Fig. 2.

Organisation and status, Source: PMP, AVL

This WLTP based brake wear cycle – described by vehicle speed profile – consists of 303 stops within 10 different trips, separated by soak times to cool down the brake.

As the magnitude of the brake particle emission is highly depending on boundary conditions like bedding state or temperature a respective bedding procedure proposal has been elaborated as well as the air flow around the unit under test.

Another decision was taken in the selection of the testing environment: in the foreseen first step of the regulation the component brake is going to be evaluated in terms of particle emissions on a brake dyno.

The current main activity of Task Force 2 is the input of measurement results to elaborate the most stable measurement methodology for brake wear particles. Numerous laboratories around the globe will participate in a Round Robin in 2021 for the comparison of the different methods.

PMP will then – after a detailed analysis of the measurement campaigns – select the most promising approaches and will finally decide on a standard method (Fig. 3).

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Fig. 3.

Example of brake dyno for emission testing, Source: AVL & TU Ilmenau

In the first phase an application of this methodology is planned for light duty vehicles (up to 3500 kg), with propulsion by internal combustion engines. In this way the assessment of the brake emissions is narrowed to the component – without any influence of e.g. recuperative braking or other vehicle control strategies.

2 Basic Approaches to Reduce Brake Emissions

The central aim of all these activities is to reduce the emissions, whereas the measurement is just a tool to control the efficiency of the reduction or the boundaries for a vehicle certification.

Particle emission measurements is a well known field already from combustion engine development and the technology and tools for the respective tasks on brakes are following the same approach.

Subsequently an early engagement in this topic was logic – especially as the requirements for the sampling devices, particle counter etc. are similar.

AVL has done a lot of researches on these new topics already and for sure is member of the PMP as well.

So basically there are two ways to reduce particle emission of brakes:

1.

Avoidance

Due to physics reduction of speed transfers kinetic energy into another one, in case of friction braking this usually includes the production of a certain amount of particle emission, created within the friction zone disc/pad or drum/shoe. The number of particles, the size, composition etc. is depending on a lot of boundaries such as temperature, vehicle speed, original friction material composition, clamping force, …

The appearance of particles can be reduced by

Reduced friction braking

Recuperation via more or less sophisticated brake blending functions

Vehicle strategies (e.g. predictive driving) mainly to reduce speed in advance

Catching particles within the brake system (-- > drum brake)

New material of friction partners (disc, drum, pad)

Coatings of discs

Reduction of drag torque (e.g. by active pull back with Electro Mechanical Brakes)

In the future the general speed average on the roads will decrease and thus reduce the required brake energy

2.

Filtering

Regarding filtering there are again 2 basic approaches.

Passive filtering:

already emitted particles are thrown into the filter (installed consecutively after the brake caliper) just by their momentum/mass

after sales parts are already available – e.g. Mann&Hummel

Active filtering:

abraded particles are sucked actively from the disc/drum surface as far as possible and led to a filter

quite efficient systems are available or under development – e.g. from Tallano (tamic system)

All of these methods and approaches have been evaluated according to a lot of criteria as shown in Fig. 4 – such as Degree of particle reduction or Packaging requirements regarding the impact on the development of the complete vehicle.

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Fig. 4.

Measures for the reduction of brake emissions, Source: AVL

Some of the mentioned measures can reduce the particle emissions of the friction brake dramatically – just by an optimal utilization of available hardware (e.g. recuperation) or via pure software (e.g. predictive driving) without the necessity of additional components – at the same time increasing the electrical range as synergies.

A disadvantage of less friction braking on the other hand is the increased risk of corrosion of brake discs. According to brake wiping functions the discs could be polished – but the better solution would be non-corroding parts – e.g. coated discs (e.g. iDisc) or new materials on both sides of the friction area like the Al-MC disc from Floby including dedicated pads.

Drum brakes are in the game again for lower performance requirements after years of absence – with some advantage regarding particle emission – the design itself can encapsulate the particles within the brake on the one hand and it is better protected against corrosion. Furthermore drum brakes have got a lower drag torque than conventional disc brakes.

At this point electromechanical brakes are showing another advantage besides actuation speed and system integration – due to the working principle they are able to eliminate drag torque completely by the possibility to lift the pads actively from the disc.

The previously mentioned points can be realized short term – some of them are already in the market.

Another fact will reduce the brake emissions implicitly – the average driving speed on our roads will decrease over the next decades – let it be via legislation, traffic situation or autonomous driving. As the emission of particles is dramatically increasing with high temperatures, less high speed brake maneuvers will have a big impact on all kinds of non-exhaust emissions – in particular for brake emissions even more in combination with recuperative braking.

The relevance of these reduction measures for the actually planned regulation and cycle has been assessed as well – stating that all intelligent vehicle strategies and functions will not reduce brake emissions within the cycle as they will not show their potential with just the component except maybe the drag torque (Fig. 4).

The thresholds for brake particle emissions have not yet been set, but it can be expected that their magnitude will be in the range of the respective exhaust emissions.

So in the vehicle all brake emissions, that cannot be avoided, have to be filtered in some way – actively or by a passive filter.

Passive filtering is already available on the after sales market – e.g. from M&H, integration effort and costs are manageable, a certain impact on e.g. brake cooling can be expected, the effectiveness of filtering has to be proved on an emission dyno under the defined WLTP conditions.

Active filtering is also under development (or even available) by e.g. Tallano. The reduction potential of these systems is clearly higher when particles do not even leave the friction area, but they are causing a bigger integration effort within the vehicle development process.

An expected roadmap for the relevance and efficiency of the measures has been elaborated based on the researches and seen trends (Fig. 5. showing the respective exhaust emission limits in the y-axis).

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Fig. 5.

Expected Roadmap for the efficiency of the different measures per vehicle category, Source: AVL, Strategy Engineers.

The necessity of adding filtering systems into vehicle systems in the future is highly depending on the non-exhaust legislation and their maximum permissible values of particle emission.

3 Impacts

All these measures will not only influence the emission of particles, but especially in combinations they will have interactions with other vehicle properties, will influence calibrations and already running systems.

The pressure to fulfill emission regulation, will have an impact on brake performance, NVH behavior, brake dust, corrosion or maintenance (Fig. 7), so big testing and measuring campaigns will be initiated and the demand for brake testing capacity will dramatically increase (Fig. 6).

../images/510426_1_De_3_Chapter/510426_1_De_3_Fig6_HTML.png

Fig. 6.

Impact and Interactions of the measures for reduction of brake emissions on vehicle development, Source: AVL

../images/510426_1_De_3_Chapter/510426_1_De_3_Fig7_HTML.png

Fig. 7.

Emission brake dyno at AVL Graz

In the end every single vehicle variant has to be validated and certified within the development process, after having found the best compromise regarding all properties. For the vehicle manufacturer this means to verify a huge matrix of different configurations, as e.g. the pad material has to meet other requirements from market to market. The biggest drivers here are diverse customer expectations and priorities – mainly regarding performance, dirty wheels or life time.

Due to the fact, that the worldwide market for combustion engine testbeds will simultaneously decrease, AVL is preparing conversion kits and services to modify an engine dyno to a brake emission dyno, which will save a lot of effort as most of the infrastructure and components of already available and approved test facilities can be reused.

The complete test cell, controls, dyno itself, exhaust air system, even the intake air conditioning system can be used for the brake emission measurements.

The conversion of already existing test cells means lower planning and application effort as well as investment to increase the required test capabilities within a shorter time.

The complete equipment for the measurement of brake emissions is available as a product, derived from the worldwide known exhaust emission units (Fig. 8).

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Fig. 8.

APC xAPP – particle counter; Source AVL

4 Frontloading

A worldwide trend for pushing more and more development to earlier phases can be seen over the last decades within more and more fields to be able to get at least indicative results even without hardware being available.

Thus AVL is also providing tools for brake simulation – not only for performance, thermal behavior and NVH, but also for brake wear.

Brake wear depends on several effects at the brake pad like temperature, pressure, relative velocity, frictional coefficients and other. Therefore we are working on a simulation method based on the pressure distribution of the pad/Disk interface (see picture). This iterative method is available for simulating the wear effect regarding deformation of the pad surface. The wear effect has to be adjusted by testing results. This tool will be developed towards prediction of abrasive behavior of known pad/disk combinations. To achieve a realistic behavior of the pads, detailed FEM-models are necessary. These models contain all relevant parts around the pads, including contact modelling and the fixture to the testing rig. Integration of real suspension situation is possible.

Simulating the brake emissions themselves in detail is a huge challenge as the composition of the brake pad itself is a strict secret of their manufacturers. Furthermore depending on the resulting temperatures within the friction zone some of the components are additionally modified when leaving the contact zone, which makes the simulation still much more complex, but we are on the way …

Models contain detailed setup of brake parts to get a realistic pressure behavior at the pad/disk interface.

Fig. 9 shows a