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In the mid-term, the German post office Deutsche Post wants to move its entire short-range fleet over to electri-cally driven vehicles and has secured Streetscooter GmbH as its partner [1]. This is just one example of the way busi-nesses are equipping themselves for future tasks. However, it is not just the corporate world that has its sights set on electromobility; local authorities are also facing a major challenge. In many cities, the limit values for exhaust gases have not been respected for years, with the result that driv-ing bans are being discussed. Bans of this sort would have far-reaching consequences: Urban transport operators would not be able to carry any more passengers and shops would not receive any deliveries. To preserve the environ-ment and set a good example, the Netherlands has set it-self the aim of approving only electric buses for use in city traffic as of 2020. The Dutch city of Eindhoven currently operates approximately 50 articulated electric buses and

wants to further expand this fleet in the future. Local au-thorities in Germany are taking similar steps: Articulated electric buses are already in use in Hamburg. Sixty more are due to follow by 2020. And in the historic Old City of Re-gensburg, small electric vehicles are already being used for passenger transport.

The Challenges of ElectromobilityIn the face of the high demand for electric commercial ve-hicles, such as buses, manufacturers are being forced to make a move. Studies and prototypes already exist. How-ever, the market is demanding vehicles for everyday use. These must meet the requirements in terms of range, com-fort of travel and operation and must function as reliably as modes of transport that use conventional engines. This

Commercial Vehicles and ElectromobilityCharging AheadElectric cars, buses and trucks share the same problems: range, charging speed and charging infrastructure. Important steps have been taken. But how does charging work in detail?

Figure 1: Three different standards for electric charging are used around the world (Source: CharIN e.V.).

Figure 1

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try of the plug makes incorrect charging impossible. This is also prevented at the level of the protocol.

Release for Charging: The Control Pilot Signal The CP signal actually releases the charging operation (Figure 3). The carrier signal is the 1-kHz PWM signal. In a correct duty cycle, it refers to the high-level Ethernet com-munication which is implemented as a modulated signal in the bandwidth 3 – 30 MHz over the powerline. But why is such an intricate mechanism actually needed for charging? The vehicle must first identify itself at the charging station in order to exchange information such as payment details, charging status, type of charging and amount of charge consumed. As soon as authentication has been successfully concluded, the vehicle (master) draws electricity from the charging station (slave). The refueling standard for cars with internal combustion engines is implemented in the form of different refueling nozzle diameters. However, to charge an electric vehicle, today’s drivers also have to track down the “right” charging station. To ensure interoperability between the vehicle and the infrastructure, the standards ISO/IEC 15118, DIN 70121 and SAE J2847/2 are used in Europe and North America. These specify the charging communication and ensure that data is exchanged correctly before the actual charging op-eration starts.

Communication Between Charging Station and VehicleEmbedded software is required in order to implement the communication protocols defined in these standards. Vec-tor possesses many years of experience in implementing vehicle-internal network communication via, for example, CAN, LIN, FlexRay and Ethernet. That is why MICROSAR – Vector’s AUTOSAR basic software – has been extended to include modules that support communication between the vehicle and the charging infrastructure. Among other things, this extension, which is known as V2G (Vehicle to Grid, see Figure 4), contains the software component

is precisely the challenge raised by electromobility. For ex-ample, if the fuel level in a diesel vehicle starts to drop then the driver can simply stop at any gas station to refill quick-ly and easily. The ranges of e-vehicles are currently still very limited and the charging infrastructure leaves much to be desired. But who makes sure that a vehicle can recharge at any charging station? This is the responsibility of boards that standardize charging specifications, while also taking account of the circumstances typical of the various mar-kets. Europe and North America have adopted the Stan-dard Combined Charging System, while China uses GB/T 27930 and Japan uses CHAdeMO (Figure 1). The greatest differences between the standards lie in the plug/inlet combination, the underlying physical connection and the protocol used for communication between the vehicle and the charging infrastructure. While GB/T 27930 and CHAde-MO are based on the CAN vehicle bus, the CCS-2 standard relies on an Ethernet-based protocol named Powerline Communication (PLC).

Different Plugs for AC and DC ChargingAnother challenge for standardization lies in specifying a standardized plug. Unlike in the now widespread Automo-tive Ethernet standard 100BASE-T1, Powerline Communi-cation does not use a twisted wire pair. Instead, the so-called Control Pilot (CP) signal uses a single-wire cable. The plugs and inlets for AC and DC charging always contain three identical pins:

> Control Pilot (CP): Pulse width-modulated signal with modulated, higher-level protocol > Protective Earth (PE): Protective conductor and ground for CP > Proximity Pin or Plug Present (PP): An analog signal that confirms that a plug is present at the inlet and codes the current-carrying capacity of the cable (relevant for AC charging)

There are also further pins for AC charging and the faster DC charging. The CCS-2 plug (Figure 2) that is used in Eu-rope contains the following pins:

> For AC charging: Control Pilot, Protective Earth, Prox-imity Pin, L1, L2, L3, GND > For DC charging: Control Pilot, Protective Earth, Prox-imity Pin, DC+, DC-

Alternatively, an L-conductor and the ground (GND) of the AC plug can be used for DC charging at reduced capacity.

The high-level protocols used for communication are identi-cal for AC and DC charging. It is therefore possible to charge a vehicle with alternating or direct current provided that the standard is supported by the vehicle. The geome-

Figure 2: Structure of the charging plug for AC or DC charging.

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vSCC: Vector Smart Charging Communication. This imple-ments the entire protocol sequence for smart charging as defined in the above-mentioned standards. It is also al-ready able to work together with the Powerline transceiver. AC and DC charging are supported for all vehicle manufac-turers by means of various protocols, such as External Iden-tification Means (EIM), Plug`n Charge (PnC) or Signal Lev-el Attenuation Characterization (SLAC). On this basis, it is possible to implement customer-specific functions such as Value Added Services (VAS) via HTTP and DNS in order to establish parallel, proprietary communication between the charging station and the vehicle and thus exchange addi-tional information. The functions for this Vehicle-to-Infra-structure communication are located above the Ethernet transport protocol and can therefore also be combined with existing OEM-specific software architectures. In this way, the vSCC component can be used without it being es-sential to switch over the entire communication to AUTO-SAR. The MICROSAR implementation contains the com-plete protocols for smart charging. They are configured via an AUTOSAR tool and are linked to other necessary compo-nents.At the physical level, special transceivers are needed for Powerline Communication. These are responsible for pro-cessing the high-level signal while, at the same time, a dig-ital input for low-level communication is connected to the microcontroller. In this case, the standards predefine pre-cise values for the edge steepness of the signals. Due to the high-frequency transfer rate at the Control Pilot, it is nec-essary to pay particular attention to the EMC radiation when designing the board for a charging ECU.

Figure 3: Low-level communication for AC and DC charging via the Control Pilot.

Figure 4: The MICROSAR.V2G embedded basic software for smart charging communication in accordance with DIN SPEC 70121 and ISO/IEC 15118.

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tacts. It is precisely this type of application that is currently undergoing specification in ISO/IEC 15118 Part 2, Edition 2 and it should be available as an international standard in mid-2018. In this case, the connection between the two partners is established fully automatically by means of wireless communication. The WiFi protocol 802.11n is used for this.

OutlookAlongside the minimization of emissions, the interoperabil-ity of all vehicles with the charging infrastructures of the various suppliers is an important element in ensuring the rapid success of electromobility. Every vehicle can “refuel” with electricity at every available charging station – just as easily as drivers now fill up at modern gas stations. The aim should be for charging standards to support and not slow down this change. The standards have now been defined and accepted by the manufacturers. The market already offers suitable solutions. Industry can get to grips with the challenges without reservations and make use of the avail-able components

Charging ECUs for Commercial VehiclesThe first charging ECUs for commercial vehicles are already available on the market. Vector’s VC36PLC-24 (Figure 5) implements Powerline Communication between the vehicle and charg spot. It is particularly suitable for small series productions as well as for prototype constructions and de-velopments. The ECU assumes a range of functions such as, for example, locking the plug at the inlet, plug tempera-ture monitoring, or the display of the charging status by means of LEDs. The hardware platform of the VC36PLC-24 can be used independently of vehicle manufacturer and is suitable for cabled (conductive) charging using the CCS-2 standard. The ECU can be supplied with a software archi-tecture that corresponds to the vehicle manufacturer or as a generic ECU for prototypes or development projects. This version implements both the low-level and high-level com-munication. This means that the ECU can be easily installed in any vehicle. The open, CAN-based J1939 interface for network connection is available to users without restric-tions.

Charging via Pantographs – The Better Plug?The current standard ISO/IEC 15118 focuses primarily on cabled charging at a charging station. Here, drivers must do a number of things themselves in order to establish the connection between the vehicle and the infrastructure. In this case, it makes no difference whether the vehicle is a car or a commercial vehicle. However, this standard also sup-ports electric charging via a pantograph located on the ve-hicle. To do this, the driver presses a switch to connect the pantograph to the charging mast. However, pantographs of this type take up space on the bus and have to be trans-ported by the vehicle, increasing its weight and conse-quently also its power consumption. One solution here takes the form of the so-called inverted pantograph, i.e. a system in which the main element is located in the fixed infrastructure and the vehicle is simply equipped with con-

Figure 5: The Vector ECU VC36PLC-24 offers an interface for stan-dardized communication of electrically powered commercial vehi-cles with the charging infrastructure. It supports DIN SPEC 70121 and ISO/IEC 15118.

B.Eng. Jonas LesererBusiness Development Manager for Embedded Software and Systems at Vector Informatik and responsible for small series ECUs.

Translation of a German publication in Elektronik Praxis, special issue Embedded Software Engineering, 11/2017

Image rights: Vector Informatik GmbHThe World Factbook (edited by Vector Informatik GmbH)

Literature References:[1] Press release Deutsche Post DHL (2014-12-09)