*4.1. E/E-Architecture for EVs*

The physical architecture as well as the electrical and electronics (E/E) architecture will be the keys to manage the increased complexity of the third generation of EVs, which will require a faster increase in electronics, software, and communication capabilities.

The new generation of electric and autonomous driving vehicles is evolving towards a distributed connection of smart sensors, ECUs, and actuator control units (ACUs), up to one hundred devices for a premium car, with stringent requirements in terms of bandwidth, functional safety, and security. In addition, the complexity of the software, stored in the non-volatile memories of the ECUs, is continuously growing [34]; today, the number of software code lines on a premium car is reaching 100 million. Security against cyberattacks is a recent but very important issue in the transportation world. As vehicles are evolving towards autonomous driving, and the vehicle-to-X (vehicle, infrastructure, road, or pedestrian) connections and on-board vehicles networking allow for access to every ECU in a car, then a remote cyberattack can force failure in any of the key functions of a vehicle, like the control of propulsion, braking, steering, and so on. To illustrate the importance of automotive security, recent studies forecast investments in this field of up to 11 billion by 2021. By 2020, some estimates forecast that 40% of the cost of a car will be in wiring and connections. Cybersecurity issues of digitized and electrified vehicles are discussed in Section 5.

A seamless hierarchical E/E architecture for the next generation of cars is shown in Figure 9. In this architecture, the central computing platform partition the main software functions offering high performance and fulfil the highest security and safety requirements.

**Figure 9.** A powerful integration platform enable a seamless hierarchical electrical and electronics (E/E) architecture.

The advantages of this platform, shown in Figure 9, are that each ECU class has specific requirements, such that the classification is requirements-based and the system level optimization is the focus. BMW has introduced a service-oriented architecture (SOA), similar to the one in Figure 9, for the next generation of E/E architecture, with hierarchy enabled testing against interfaces using agile methods for system complexity reduction.

#### *4.2. Power Train Design and Component Trends of EVs*

The majority of European automotive manufacturers have already decided to introduce 48 V technology to reduce the consumption of their fleets and to meet the new European CO2 boundaries, which will came into force from 2021. In the near future, plug and play or start–stop systems, 48 V systems, and high-voltage electrification will all occur together in most fleets. A strong worldwide global trend towards plug-in hybrids has emerged. For instance, in China, all-electric vehicles are particularly in demand.

In Europe, 48 V systems still have their development core, although many automotive manufacturers have now recognized their advantages, and global programs have been introduced immediately after that. An analysis of the extra costs of HEVs proves that 48 V mild HEVs are only 30–50% as cost-intensive as high-voltage HEVs [35]. As such, the 48 V system represents an intelligent and, in particular, affordable supplement to full and plug-in hybrids vehicles. In addition, 48 V systems can be integrated more easily into existing vehicle powertrains and architectures, but a fewer extensive modifications are also required. Consequently, it can be anticipated that the 48 V voltage level will very quickly become established in the market.

Furthermore, to make use of hybridization, the additional 48 V system also makes it possible to have a choice of electrical components in the vehicle at higher voltages. This is significant, because the number of electrical components is continuing to expand dramatically, especially in the mid-size and luxury car markets [1,35]. In addition to that, high-power components work more efficiently at higher voltages, and converting them to the 48 V on-board power system also decreases the load on the 12 V system. Market predictions highlight the fact that 25% of newly registered cars will have an electrified powertrain by 2025, as can be seen in Figure 10, and that almost half of these vehicles will use 48 V technology.

**Figure 10.** Market forecast electrified powertrain by 2025 (source: Continental).

As can also be seen in Figure 10, beginning with the year 2020 onwards, a global potential of up to four million of 48 V systems could be deployed.

Because of the different options to mechanically connect and integrate the 48 V electrical machines (usually as a starter generator in 48 V technology) into the drivetrain, and the different types of 48 V electrical machines available for selection, several powertrain topologies are achievable. The powertrain topology chosen significantly influences the performance and characteristics with which the aforementioned functions can be implemented, as well as the costs involved. Carmakers and automotive suppliers are currently analyzing and evaluating four major powertrain topologies [36–38]. Depending on the e-machine architecture, the topologies vary in relation to their potential for energy recovery and electrical boost capacity.

In the next-generation of EVs, power and efficiency are critical parameters, as the number of engine control units and ECUs within the cars grows exponentially. The electrical and electronic component's models, such as electrical machines, power electronic converters, and controllers, represent the e-drivetrain system components for closed-loop tests (HIL).

#### *4.3. High Voltage Battery Systems Technology and Battery Management*

The high voltage battery system is in fact the EV energy source subsystem. As it is one of the most important components of BEV, it may require special care and handling. For instance, in the case of DC fast charging, EV's BMS system and charging station should establish the bi-directional communication to exchange information such as the battery charging pattern, state of charge (SOC), temperature, and so on [39]. At present, the battery system is one of the most demandable and critical components of the EV system. Main issues include their weight, price, capacity, energy density, lifetime or degradation, electrical parameters, and dimensions [39–43]. For all of this, EV batteries' market segment is rapidly developing and increasing, and manufacturers and e-mobility stakeholders are conscious that batteries are crucial for the sector to be further development [1,39].

The most used battery technology for EV is Lithium-ion, as already highlighted in Section 2. This battery type can be designed using various cathode and anode materials such as lithium titanate, lithium–cobalt, oxide-based, or lithium–iron–phosphorus. Li-ion promises a high energy density, lifetime, and charging cycles [1,40–44]. Li-ion batteries are characterized by an energy density of 130 Wh/kg, a cell voltage of 3.7 V, and their expected number of cycles (e.g., 3000), assuming that the depth of discharge (DoD) is at 80% [39]. The highest practical energy density can be achieved within the cobalt cathode (120–180 Wh/kg). Battery development is crucial for further e-mobility development. The most urgent issues include increasing the energy storage capacity, allowing for high current charging, and extending cycle lifetime, as well as improving safety and reducing cost.

The BMS handles operation of the EV battery and its functionalities are very important for the optimal use and handling of high voltage batteries. It controls the charging and discharging cycles together with the on-board or off-board charger. The control strategy is in most cases arranged for extending the battery lifetime. BMS impedes also from deep discharge and wrong charging parameters. The main important BMS tasks can be summarized as follows:


The BMS system/unit contains three main subsystems, centralized, distributed, and modular parts. Centralized subsystem is based on wire connections and is a single controller connected to the battery cells. The distributed components of the BMS implies BMS on/off board battery chargers, in which each cell is equipped. Modular subsystem involves a few controllers, which carry out the operation of a certain number of cells. BMS needs to send the required data to other devices in the EV system. The main measures used for this purpose include CAN BUS, FlexRay, or direct wiring, although data transmission over the power bus or fast wireless communication based on IoT may be used.

#### *4.4. Electric Motors and Control*

It is imagined that the 48 V powertrain systems of all types will operate without the traditional 12 V generator, as the 48 V electrical machine takes over the generator function. Thanks to the higher voltage, the electrical machine's performance and efficiency will be improved. Differently from classic 12 V generators, electrical machines in new EV generations fulfil two different functions, as they work in both regimes, as generators and starters, or rather electrical motors, to support propulsion.

Key parameters of the powertrain system include the total system load, the charging status (SOC and SOH), and the dimensioning/size of the batteries. The energy management system controls the activation of individual functions and features, such as the charge, boost, or recovery modes, in the circumstances of the specific driving situations and conditions. While 12 V electric generators are employed, the claw-pole machines, because of their system design, the introduction of 48 V powertrain systems will lead to the coexistence of different technologies. Two electrical machine technologies are employed—synchronous and asynchronous/induction machines, as can be seen in Figure 11.

**Figure 11.** A block diagram with a short classification of electrical machines used in EV applications.

Synchronous machines are divided into different machines categories with excitation winding, of either the salient-pole or claw-pole rotor type, permanent magnet synchronous machines, and reluctance machines. The rotor of asynchronous or induction machines consists of a laminated core with uniform slotting accommodating either aluminum (copper) bars short-circuited by end-rings (the squirrel cage), or a three-phase winding (as in the stator) connected to some copper rings and fixed brushes—the wound rotor. Induction machines with squirrel-cage rotors are mostly used because of their robustness technology. The speed, efficiency, and power density of the machines may vary as a function of the active power and maximum current of their respective rectifiers. It is therefore difficult to classify any single machine as the best type. Furthermore, the automotive industry also requires additional important factors such as battery package space, costs, robustness, and standardization that need to be considered. This explains why different technologies will be used in the 48 V powertrain system.
