Development of an open vehicle platform for the mobility of the future
Dr. Michael Lahres
Mercedes-Benz Group AG
Dr. Michael Lahres ist Maschinenbauingenieur und leitet das Projekt FlexCAR ab dem 1. August 2021. Er ist verantwortlich für die Außendarstellung und vertritt FlexCAR gegenüber dem Projektträger und den Partnern.
An open vehicle platform for the mobility of the future
Smartphones have fundamentally changed the way we use telephony. Extensive office and data communication is possible from anywhere and at any time. Standardized and open software interfaces (API) enable third-party providers to offer new applications based on existing hardware. This is where the FlexCAR project (10/18 to 09/23), funded by the Federal Ministry of Research and Education, comes in, in which a research demonstrator was developed with a standardized autonomous vehicle platform that allows new technological features to be implemented directly from the research stage according to the plug-and-play principle and enables validation with regard to future application potential.
1. The vision
The vision of the FlexCAR joint project is to transfer this development to future mobility concepts. Suppliers, but also new market participants such as start-ups or developer communities, are invited to provide services and components for platform operators (OEMs) or directly for end customers throughout the entire vehicle life cycle. Interfaces must be defined on the hardware and software side for this purpose. They must be as easy to use as possible ("plug & play"), but still fulfil the highest cybersecurity requirements.
2. The objective
The aim of the FlexCAR project is to develop a cyber-physical vehicle platform with open hardware and software interfaces. The implementation of self-reflective, self-describing and service-orientated components on this platform makes it possible to design a vehicle that can be updated and upgraded throughout its entire life cycle, both in the software and hardware areas, right up to complete, automatic reconfigurability and safeguarding of the overall system. In order to demonstrate the feasibility of the concept and to show how the car of tomorrow will be created and designed, the FlexCAR joint project is analysing the open interface issues over the course of the project using typical vehicle scopes. These vehicle scopes include the development of individual, future-oriented components in an exemplary, scaled-down innovation network and their utilisation in a research and experimentation platform.
3. The topic areas within the project
Topic areas FlexCAR. Image: Mercedes-Benz AG
Four topic areas form the framework of FlexCAR's activities
Topic area 1 - "Rolling Chassis" is developing an electrically powered research platform controlled via 5G with accessible and open software and hardware - the Rolling Chassis. The platform serves as a unit carrier and common basis for the individual FlexCAR technologies. This is extended by a base plate, which creates an interface to the interior and is available to TB 2 for various use cases and interior studies.
The focus of topic area 2 - "Interior and cyber-physical entry" builds on the topics of topic area 1. Interior-related use cases are considered here, focussing on the areas of "Working while driving" and "Relaxing while driving". For example, if a customer books a journey via an app, this request is sent and processed via 5G. A vehicle is assigned according to the customer's requirements and the customer is provided with details of the time and place. The vehicle arrives at the agreed location at the agreed time and keeps an eye out for the customer. Contact can be made with the vehicle via outward-facing cameras. Only authorised persons are granted access and the journey can be billed accordingly. The future interaction between passengers and autonomous vehicles is therefore also an important focus during the journey.
In topic area 3 - "Flexible product and production concepts", the FlexCAR production concept is being developed in close collaboration with the Fluide Production (FluPro) project. Drive and energy modules are to become the focus of production engineering considerations here; for example, the issues of suitable sheet metal or structural profiling within the framework of the chassis. With the help of standardised interfaces, the rolling chassis is part of the cyber-physical production system and can be used as a further use case during production, for example as a driverless transport system, thus replacing current transport and conveyor technology in the factory.
Topic area 4 - "Open development process for modular vehicles" deals with the implementation of one of the key criteria of FlexCAR: the open development process. The aim is to develop and implement open interfaces for hardware and software, allowing new business models to be established. FlexCAR is therefore much more than just a new vehicle concept. It offers a research platform for the centralised development and production of modular vehicle systems.
4. The results
4.1 Drive and alternating storage systems
As part of the FlexCAR research project, a mobile, updateable and upgradeable platform was built as a rolling chassis, which essentially consists of three individual modules. These three individual modules, which are divided into two identical drive modules (DRIVE modules) at the front and rear and a storage module (energy module) in the centre of the chassis, form the basis for the rolling chassis. Pre-equipped with drive components and E/E scopes in the DRIVE modules, these can then be joined together with the Energy module. Together with the integrated energy storage unit, the energy module forms the centrepiece of the chassis. Different energy storage systems (battery or fuel cell) and associated components can be integrated into it. By largely standardising the interfaces and contact points, the DRIVE modules and Energy modules can be combined to create a flexible drive platform.
The different energy storage systems are integrated using customised support structures. The interfaces between the individual modules for electrical and electronic components are largely standardised via connector systems and connections. Findings from the "Wiring harness innovation initiative", an open cooperation network of actively involved industry representatives who are working on various pre-competitive topics as part of the ARENA2036 research campus, have been incorporated into this process.
4.2 Floor module structure, interior set-up and use cases
Another research focus of the FlexCAR project was the design, demonstration and evaluation of new interior concepts for the autonomous mobility of the future. In order to optimise the use of driving time in automated or autonomous vehicles, use case work plays a particularly important role.
The hardware interface between the rolling chassis and the subject area of the interior is the interior module. This has a self-supporting frame construction into which seat rails with additional side rails have been integrated. This rail system can be used to create various seat constellations and positions, as well as to attach different interior components and position them independently of the seats. The "mobile work 2036" user study was designed to analyse different technologies for the consumption and processing of digital content. To this end, the interior module was equipped with two seats and two interactive digital work surfaces. The first interactive surface consists of two HPL panels with a touch-sensitive film laminated between them. With the help of three projectors, which are realistically suitable for installation in the car due to their design, an interactive interior surface was created.
Rolling chassis with interior module and seats (components from Mercedes-Benz V-Class production vehicle, V447). Graphic: Mercedes-Benz AG
4.3 Exterior and interior concept developments
The change in usage models for vehicles towards autonomous driving and shared mobility is directly related to the change in mobility needs and user behaviour, and therefore demands more flexibility and adaptivity from the vehicle of tomorrow. The FlexCAR research project focussed on a homogeneous research platform that can be used to save both development time and costs. Modern, cyber-physical approaches make it possible to implement production aspects and product topics in customer-centred designs in the exterior and interior that map various use cases.
The focus was on two different main use cases that demonstrate the flexibility of the rolling chassis. The Peoplemover Use Case focusses on the transport of 4 passengers who use the shuttle as a combination of "Working while driving autonomously" and "Relaxing while driving autonomously". The Luxury Car Use Concept serves to illustrate and analyse future autonomous high-class mobility, with "Relaxing while driving autonomously" taking centre stage. These use cases require different exterior and interior designs (see Fig. 5 and Fig. 6), which we created and analysed in virtual reality. Specific features were built in hardware, but the majority were represented digitally as 3D models and analysed cyberphysically. Specific use cases of this research were the testing of different boarding concepts, as well as communication and interaction in the interior between the passenger and the autonomous shuttle.
Interior concept for Peoplemover Use Case. Graphic: HdM Stuttgart & exterior concept design for Peoplemover Use Case. Graphic: DLR Stuttgart
4.4 Cyberphysical visualisation technology
As part of FlexCAR, the Hochschule der Medien (Media University) focussed on making autonomous vehicles and the vehicle interior of the future tangible. Driverless autonomous driving of SAE level 5 was considered with a focus on first-time users and early adopters. The focus here was on creating transparency between the passenger and the autonomous vehicle. By creating AI transparency and breaking down the actions of the autonomous vehicle using innovative human-machine interfaces, the aim was to create a positive user experience for end users during autonomous driving.
The implementation of tracking real vehicle elements and their synchronisation with a virtual 3D environment is well advanced. A virtual autonomous journey through a simulated city with various parameters (e.g. weather, time of day, traffic volume, etc.) has been realised. The next steps included finalising the interior and exterior of the autonomous shuttle as well as test drives to iteratively adapt the prototype. Furthermore, performance optimisations and the expansion of the current status to include elements from project partners (e.g. luggage systems, mobile working or boarding concepts) were also carried out.
4.5 New profile structures for the FlexCAR chassis
The rolling chassis developed in the FlexCAR project is a mobile, upgradeable and modular vehicle platform that can be powered purely by electricity or a fuel cell. The current FlexCAR prototype follows a highly integrative concept approach, which was optimised in a second step through flexible, demand-oriented production concepts. The focus here was on the further development of the energy storage module (energy module), which formed the framework structure for the high-voltage storage system and for the fuel cell with hydrogen tanks. New requirements resulting from the structural change in the automotive industry towards sustainable, electric mobility and from shorter development and product life cycles were taken into account. The profile structures developed here should be as weight-optimised as possible, easily recyclable, designed to meet requirements and easily adaptable.
The simulative optimisation of the energy module made of extruded aluminium profiles with regard to a modular design while simultaneously meeting approval-relevant crash requirements, in particular the side pole test, showed that a weight reduction of the sill with improved crash behaviour can be achieved by introducing local reinforcement structures. The intelligent combination of different aluminium alloys not only ensures the required properties of the components between ductility and extrudability, but also that the sill profile guarantees system integrity even in the event of massive deformations. The two insert profiles in the sill, which are modularly integrated into the sill depending on the configuration, are made of a high-performance HSA6® aluminium alloy with very good recyclability and therefore make a significant contribution to weight reduction and sustainability.
In order to fulfil the crash requirements even in pure sheet metal construction, the crash-relevant profiles were joined together from several bent sheets using laser beam welding to form a multi-chamber profile. By using the innovative TRUMPF multi-focus technology, the formation of pores in the weld seam was largely avoided, enabling gas-tight weld seams. In some cases, the sheets were positioned using plug-in connections. This enables flexible joining with little need for fixtures. The elimination of the flange also saves weight.
In conventional production, the corner joint is usually manufactured as a separate component, e.g. as a cast part, and usually has to be reworked at great expense due to fitting problems. In this project, the corner node was realised by intelligently nesting the sheet metal profiles using a new type of bonding technology. For this purpose, an LMD seam, the height of which corresponds exactly to the gap dimension between the profiles, was applied to one of the profiles to be bonded and the profiles were then joined together. In this way, it was possible to compensate for tolerances in the gap dimension on the one hand and to ensure a constant gap dimension everywhere on the other. The constant gap dimension and secure positioning thus enable reliable adhesive injection and a reliable connection of the profiles without critical heat input.
4.6 Sensor integration on the FlexCAR
The integration of sensors in the rolling chassis of the FlexCAR project was intended to realise a vehicle that can be updated and upgraded. This includes the sensor technology for autonomous driving as well as the use of sensors for structural monitoring and the integration of additional functions.
The vehicle's internal wheel speed and steering angle sensors and the IMU were used in an approach for estimating the driving status and localisation. The speed, alignment and position prediction from an inertial navigation system was combined in an Unscented Kalman Filter (UKF) with the observations from a wheel speed-based odometry model and a gravity-based position calculation. This system could be supplemented by position observation from 5G positioning or infrastructure camera-based localisation. Lidar and camera are used in FlexCAR for environment modelling, localising the vehicle and detecting objects in the immediate vicinity.
4.7 Implementation of printed control element with integrated RFID component recognition
In order to be able to manufacture electrical components such as a control element for a vehicle cost-effectively, they usually have to be produced in large quantities. At the same time, however, these components should also be able to be integrated into the corresponding vehicle interior in the most visually appealing way possible in terms of color and design, which results in a correspondingly high number of variants. With the help of additive manufacturing processes, the design, surfaces and colors of components can be freely designed during production on the same machine. It is also possible to freely position printed conductor paths in the component and integrate printed sensor elements. Wireless verifiability is desirable to ensure that the correct component is and has been installed in the respective vehicle with a high number of component variants.
With the help of inkjet technology, an additively manufactured 2D demonstrator of a control element (dimensions 100x50x1 mm³) with button and slider function was constructed. This consists of a semi-transparent black plastic, printed circuit and sensor elements and an electrical connection to a 16-pin ribbon cable. Furthermore, by selecting suitable printing parameters and strategies, the surface could be adapted optically and haptically to such an extent that the position of the button is visible but can also be felt with the finger. RFID tags (dimensions 57.1x5.95 x 1.3 mm³) were successfully integrated into inkjet-printed 3D objects and identified at a distance using an RFID reader. The data on the RFID tag can be displayed and rewritten as required via a user interface developed in the project.
4.8 Integrated onboard and offboard communication via 5G in the ARENA2036 architecture of the onboard and offboard network
Requirements for future vehicles are increasingly shifting from hardware to flexible software instances in order to be able to react to changing demands on computing resources through functional adaptations, updates or hardware failures. Flexibility in development plays just as important a role as adaptations via updates after the vehicle roll-out. The improvement of existing algorithms, the exchange with environmental sensors or the integration of external sensors beyond the system's own limits require a high degree of flexibility, which can be achieved by means of an open development platform and software-oriented architecture. Updates can already be carried out over-the-air via remote maintenance without workshop visits. In addition to control functions, remote access also enables the sharing of all onboard data for visualizations. Communication with external devices is also the minimum requirement for Vehicle-2-everything connectivity (V2X). Integrated but flexible onboard and offboard communication via 5G in the indoor ARENA2036 environment was necessary for the FlexCAR project.
The communication architecture of the rolling chassis comprises both internal communication (onboard) and external communication (offboard). Onboard communication describes the data exchange between all devices and instances that are installed on the rolling chassis. Information is exchanged via Ethernet. By using a software-oriented architecture (SOA), the software is no longer tied to a specific hardware and can be executed flexibly in the system. The SOA is implemented in the Rolling Chassis via the middleware Data Distribution Service (DDS), using RTI connext, among other things. The service interfaces are standardized in .idl format and are exchanged with additional information about Quality of Service (QoS). Onboard communication is therefore interoperable across software instances, programming languages and various operating systems. This ensures adaptive compatibility with Robot Operating System 2 (ROS2) or the AUTOSAR Adaptive Platform. A 5G connection to the indoor ARENA2036 production network was established for offboard communication. Communication within the ARENA2036 network took place via the Message Queing Telemetry Transport Protocol (MQTT).
Both DDS and MQTT work according to the publish-subscribe principle, but on the basis of different protocols. The protocols therefore had to be translated. To ensure full compatibility between the onboard and offboard systems, a DDS2MQTT bridge was developed by the IAT at the University of Stuttgart in collaboration with the Fraunhofer IAO. This can be used to route any messages from and to the vehicle. In addition to DDS and MQTT, the communication architecture also supports the User Datagram Protocol (UDP) for connecting embedded hardware. This made it possible, for example, to implement communication with the control unit for basic driving functions. A separate software bridge was also developed for this. The control of the driving functions, sensors and actuators, data processing and utilization is carried out internally by other specially developed software instances. The necessary computing power is provided by four Nvidia Jetson AGX Xavier modules. Due to the chosen architecture, the entire network communication of the rolling chassis functions as a closed unit both within the vehicle and via the indoor ARENA2036 network.
The rolling chassis communicates with the indoor ARENA2036 network via the 5G Stand Alone System (5G SA) of the ARENA2036 installed by Nokia. By means of two Pico Remote Radio Heads transmitting on the 5G Radio Interface, a radio coverage of 4000 m² can be achieved. A further Micro Base Station was also installed in the outdoor area in the ARENA2036 parking lot to enable uninterrupted cell switching of the radio cells. The core network was expanded into a broadband 5G core network. A 10 Gbit fiber optic cable covers the necessary bandwidths. The 5G network operates with a downlink of over 1 Gbit/s and 250 Mbit/s in the uplink, with optimized latencies (round trip) in the range of 8 - 15 ms.
Infrastructure-based sensors for position and obstacle determination play an important role in the FlexCAR project, especially for indoor operation where no GPS signal is available. The position and location of the rolling chassis are determined externally to the vehicle and transmitted to the vehicle via the 5G air interfaces.
Four IP cameras installed in the hall of the ARENA2036 were used for localization by means of a camera system. Their video data is transmitted to a central control computer via 5G. Perception algorithms are implemented there to determine the position and orientation of the rolling chassis as well as the position of any obstacles. This is done using neural networks and inverse perspective mapping (IPM). The exact position of the obstacles is determined by a "footprint" determination using AND linking of the images from the various cameras. The detected positions and obstacles are transmitted to the rolling chassis with an accuracy of approx. 5 cm using the described communication architecture.
For the localization of mobile devices, Nokia Bell Labs has also set up a prototype system in the ARENA2036 hall that goes beyond the 5G network. These are measuring receivers that receive 5G uplink signals and transmit them to a server. On the server, the position of the mobile device is estimated from the measurements using special algorithms. The 5G positioning data is returned to the vehicle in real time.
The concept of the open development platform and its implications were examined in DXC's FlexCAR project. The software-defined approach of an open development platform promotes open source and crowd collaboration with the associated inherent innovation potential. At the same time, fundamental changes are taking place in digital lifecycle management and the software supply chain. New processes such as DevOps have been integrated into the vehicle industry, along with over-the-air (OTA) updates. To demonstrate the technical feasibility, DXC designed a pilot application for OTA software updates using Excelfore's eSync technology. As an example of embedded functions, DXC selected the object recognition system used on the rolling chassis. A new version of the object recognition software was used to successfully test an improvement in ADAS functionality through the OTA software update. In collaboration with the company Asvin, DXC investigated the integrity of cyber security in the ecosystem of multi-level supplier and OEM software chains. Using an automated end-to-end process chain with regard to development, provision/release and installation and the Asvin blockchain documentation, it was possible to demonstrate how a secure, auditable software supply chain can be implemented.
5. Starting points / follow-up projects
The selected focus topics show that these new innovative approaches and methods can be used to design future forms of mobility in a targeted, fast and efficient manner with regard to automated or autonomous driving using the FlexCAR research and experimentation platform. The developed software-oriented architectures offer a flexible assignment of programs to the FlexCAR hardware and thus raise the modularity of the FlexCAR concept to a new level, which, together with broadband communication, enables complete data exchange for the use of edge or cloud computing. The open FlexCAR research platform created with its new removable storage and production concepts and the embedding of VR/AR technology offers an ideal space for further research and development work, independent of model series and competition.
In Phase III, from 01/2024, selected aspects will be further researched in the follow-up project CARpulse in the Mobility 2036 funding priority on the Arena 2036 campus. These will deal with the further development of the software and hardware of this research and experimentation platform using selected demonstrator components, the visualization of selected issues using AR/MR/XR, as well as aspects of human crash modelling in autonomous driving.
"The FlexCAR research project impressively demonstrates how an autonomous research and experimental chassis can be connected to an autonomous transport system for indoor logistics applications and how a digitalized bus stop can be integrated into the 5G network."
Dr. Michael Lahres
Mercedes-Benz Group AG
"The mixed-reality-based visualization of future vehicle concepts in FlexCAR has shown huge potential for the future of product development using immersive media. Technical development here is only just beginning and will enable exciting new use cases with new hardware, such as the Vision Pro from Apple."
Prof. Dr. Ansgar R. S. Gerlicher
Institute for Mobility and Digital Innovation
Hochschule der Medien
"As a research platform, the FlexCAR offers the opportunity to test innovations quickly and efficiently. The cyber-physical representation using a mixed reality demonstrator makes them tangible for users."
Head of the Cyberphysical Entry and Interior topic in the FlexCAR project
Deutsches Zentrum für Luft- und Raumfahrt e.V
"In fluid production, the fast overtakes the slow"
Mercedes-Benz Group AG