The automotive industry is facing revolutionary changes. The traditional combustion engines are increasingly losing their importance. At the same time, autonomous driving will be the driving of the future and will change user scenarios and demands. The complexity of automotive interfaces has been rapidly evolving over the last decades in proportion to the increasing number of technical features. Parallel to these basic technological changes, the climate change and its dramatic consequences force the need for sustainable approaches replacing synthetic polymers by renewable bio-based and in the best case also bio-degradable materials. With this starting point, a team of experts from different disciplines at the Reutlingen University, Reutlingen/Germany, carried out an interdisciplinary research project called InBiO [1, 2].
The aim was to develop and realize a concept for an innovative, sustainable and user-friendly interior. As one element of the project, trim components made of bio-based materials such as cotton and wood were developed. An overall goal was to design a user-friendly interface, that reduces complexity without reducing functions. The bio-based materials integrate control and feedback functions that can be easily implemented in common CAN-bus systems used by the automotive industry.
The development aimed to produce a car for a persona that has been worked out by design researchers at the very beginning of the project: A 50-year-old male, manager of his own SME with a sizable income, a large, detached house, driving daily to work with his E-segment vehicle. He is enthusiastic for technical innovation and high-powered cars. An innovative bio-based interior therefore has to combine his demands for technical innovation with “green design cues” that allow him to present his environmentally-friendly attitude. Parallel to the definition of potential users, design researchers carried out subject group studies to identify most important interaction points in car interior to install control and feedback functions in an instrument panel. Starting from that, design researchers worked in interdisciplinary teams with researchers from the areas of textile technology, computer science and chemistry.
At a first sight, all disciplines had separate work packages in the development. The designers defined the personas, they developed a user-friendly concept that, e.g. guarantees an intuitive control of instruments and reduces confusing complexity of the panels and last but not least developed the product in shape, geometry and product language. Textile technologists identified bio-based, more sustainable materials, basically textiles or textile composites that can be used as alternatives for the common products used for trim components. As the bio-based textiles have to integrate control and feedback functions, the textile materials had to be equipped with electronic functions and therefore flexible conductors or circuit paths, respectively. Parallel to that bio-based materials replacing traditional synthetic polymers have to fulfill the same requirement. Both tasks, turning bio-based textiles in smart textiles as well as customizing the usage requirements, were working packages of the chemists. As that complete instrument panel has to communicate with a car’s electronic system, the computer scientists had to develop the integration of the textile electronic components into the CAN-bus system of a car. To allow driving tests with probands close to reality, the complete system was then integrated in a driving simulator.
As an example: Finding the “best bio-based material” is not a task for textile technology only. As it is not only a question of material properties but furthermore a question of the acceptance by the potential customers and the suitability for the design concept . At the same time, chemistry has to guarantee that the bio-based material can be transformed into a smart textile simultaneously fulfilling the general requirement of automotive industry. Another example involves equipping the bio-based substrates with circuit paths that has to be carried out in cooperation between chemistry, textile technology and computer science. Involving all disciplines from the very beginning of the research work is a key aspect for interdisciplinary collaboration. Such an approach reduces the number of loops in the development and leads to less failed attempts.
The search and investigation for appropriate bio-based materials led to a huge number of interesting materials to be used for the trim components. 4 materials were chosen after balancing the material properties and the identified customer expectations. These materials were cotton fabric, cork, leather and a product called Nuo, which is a veneer laminated to a textile fabric before it is laser-cut. The cutting provides drapability and translucency of the composite. Fig. 1 shows a corresponding sample. The backlight can be used to provide feedback information as well as to create a certain product personality.
Cotton fabrics were chosen for the areas where control functions have to be integrated into the panels due to their perceived naturalness and haptics, which were rated favorably in the proband test. Therefore, switching functions as well as conductor tracks had to be established. 2 basic approaches were followed for this purpose. Either the switches were realized by embroidering the components with conductive yarns or by screen-printing with flexible conductive polyurethanes. Both approaches worked, in the end the demonstrator was equipped with textile electronics based on the screen-printed switches and conductor tracks. To give an impression, Fig. 2 shows 2 samples from preliminary tests. 2 identical circuit were realized based on either embroidered (right) or printed (left) switches and conductor tracks.
Electronic textile circuit realized on a cotton fabric by embroidering the switches and conductor tracks (right) and the same assembly realized by printing the switch and the conductor tracks on a wool felt (left)
Based on the results of preliminary experiments, trim components were equipped with electric circuits. The center console is exemplarily shown in Fig. 3. As a lot of functions have to be controlled via switches, functions have been clustered in 3 groups: climate, media and options. The needed cluster can be activated by a pre-selection button. The 3 defined clusters lead to that. Every button or switch can control 3 functions depending on the pre-selection. Fig. 3 shows the center console of the demonstrator in 2 production stages. The photograph on the left shows the console before it is upholstered with the cover fabric.
The multi-layer arrangement of cotton fabrics screen-printed with conductor paths can be observed. The console shows big openings for the display, the storage tray and the gear shift. Moreover, smaller openings in the area where the 12 buttons are placed (if compared to the right photograph) can be identified. These opening will be backlighted to get a feedback on which function of the activated cluster is available in the selected setting. The right photograph shows the same console after the cover fabric has been fixed. The dots and symbols on the cover fabric have no electronic functionality as all electronic functionality is located in the screen-printed fabrics below.
Left: Multi-layer assembly of cotton fabric, showing the printed conductor tracks for the instruments in the center console. Right: Final assembly of the center console. The top layer is a cotton fabric embroidered with symbols and dots to display the positions of the switches and controllers.
The switches and controls in the textile instrument panels (steering wheel, center console “touchscreen”) were connected to the vehicle electronic system that is schematically depicted in Fig. 4. That scheme shows the general setup of the driving simulator in which all trim components were integrated. This integration in a driving simulator allows to check for proper operation of the trim components on the one side. On the other hand, it will support the designers for the ongoing investigation and evaluation of the usability and acceptance by the potential customers.
Block diagram of the driving simulator. The electronic textile elements to be integrated are the textile “touchpad” and the switches in the steering wheel.
What has been described herein can only provide a rough overview about some of the basic aspects of the project. It can only highlight some single development steps and is far away from a complete report of all the work and knowledge that has been achieved within this project. Fig. 5 shows the 1:1 demonstrator as result of this work. The upper photograph shows an overview of the cockpit. All components except the ventilation parts were designed and realized within the project work. The surfaces of the crash pad and the upper part of the steering wheel are made of wood (Nuo) and can be backlighted. The lower part of the crash pad is draped with leather. The light surfaces in the steering wheel as well as the center console are made of cotton fabrics. These surfaces cover interactive textiles with switching or control functions which are also based on cotton fabrics. The material around the InBiO-logo in the steering wheel is made of cork. The lower photograph in Fig. 5 shows a close-up of the steering wheel. The switches are integrated in the multi-layered assembly of electronic textiles. The backlighted symbols show the driver which functions can be controlled by the switches.
Completely assembled interior components developed in this project (upper photograph). The lower photograph shows a close-up of the steering wheel.
The demonstrator that has been realized in about 2 years work is an actual example of the developments in the fields of smart or electronic textiles addressing the use of sustainable materials as technical textiles for user-friendly HMI systems. The work on this demonstrator is ongoing, further projects on these topics are in progress.Acknowledgements
The authors acknowledge the financial support of the European Regional Development Fund (ERDF) and the German Ministry of Science, Research and Art of the Federal State Baden-Württemberg for the Project InBiO (FEIH_KMU_1098885). References
 Tchouboun Kemajou, C.; Gerbig M.; Wehr, F.; Walzer, T.; Luccarelli, M.; Nebel, K.; Martinez-Madrid, N.; Textor, T.: Development of a bio-based and interactive interior with a user-centred design, Book of Abstracts, ADDITC 2019, Dresden/Germany
 Wehr, F.; Luccarelli, M.: Using Personas in the Design Process. Towards the Development of Green Product Personality for In-Car User Interfaces. In: Proc. Int. Conf. Eng. Des. (Proceedings of the Design Society: International Conference on Engineering Design), 2019, S. 2911-2920. DOI: 10.1017/dsi.2019.298
 Luccarelli, M.: Material Perception in Alternative Fuel Car Interiors. Increasing Marketability through Green Design Cues., in Proceedings of the 30th International Electric Vehicle Symposium, EVS30, Stuttgart/, Germany.
NUO = registered trademark
Team of Researchers:
M. Gerbig, C. Tchouboun Kemajou, T. Walzer, F. Wehr, M. Luccarelli, N. Martinez Madrid, K. Nebel, T. Textor
Reutlingen University – Schools of Textiles & Design and Computer Science