Public
DELIVERABLE REPORT
DELIVERABLE N0: D3.4
DISSEMINATION LEVEL: PUBLIC (PU)
TITLE: DEMONSTRATOR OF A MISSION ADAPTABLE HYBRID-ON-DEMAND
DRIVELINE INSTALLED IN A TRACTOR SEMI-TRAILER VEHICLE
DATE: 31.08.2017
VERSION: FINAL
AUTHOR(S): GUNTER NITZSCHE, SEBASTIAN WAGNER (FHG IVI)
REVIEWED BY: BIRGER QUECKENSTEDT (SCB), ALFREDO SELAS (BOSCH),
RAMANAN KARTHIK (VOLVO)
APPROVED BY: COORDINATOR – PAUL ADAMS (VOLVO)
GRANT AGREEMENT N0: 605170
PROJECT TYPE: THEME 7 TRANSPORT – SST GC.SST.2012.1-5: INTEGRATION AND
OPTIMISATION OF RANGE EXTENDERS ON ELECTRIC VEHICLES
PROJECT ACRONYM: TRANSFORMERS
PROJECT TITLE: CONFIGURABLE AND ADAPTABLE TRUCKS AND TRAILERS FOR
OPTIMAL TRANSPORT EFFICIENCY
PROJECT START DATE: 01/09/2013
PROJECT WEBSITE: WWW.TRANSFORMERS-PROJECT.EU
COORDINATION: VOLVO (SE)
PROJECT MANAGEMENT: UNIRESEARCH (NL)
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Executive summary
The objective of the EU-funded project TRANSFORMERS is to design, develop, and demonstrate truck-
trailer concepts for long-haulage applications featuring high energy efficiency. Therefore,
TRANSFORMERS combines a modular approach for mission rightsizing by means of hybridization and
a trailer design that addresses simultaneously aerodynamics and load efficiency improvements. The
overall goal is to achieve a 25% higher load efficiency (in energy/km.tn) in a real world application,
while taking the needs to maintain road infrastructure and traffic safety into account.
A key innovation of TRANSFORMERS is the so-called Hybrid-on-Demand-Driveline (HoD-Driveline).
For the first time, this system enables an augmentation of conventionally driven trucks and tractors to
fully functional mission-adaptable hybrid vehicles, simply by coupling them to an innovative trailer
equipped with an electric driveline. Hence, the HoD-Driveline concept is applicable to many kinds of
truck-trailer combinations.
In addition to the HoD-Driveline concept TRANSFORMERS has developed a pre-standardisation HoD-
Framework document. The objective of this framework is:
to ensure the interoperability of the HoD-Driveline concept with today’s and with future trucks
featuring advanced energy management capabilities,
to provide a slim common interface between trucks and trailers, that requires only minimal
changes to the existing standard interface.
Deliverable D3.21 describes a first holistic draft of the pre-standardisation Hybrid-on-Demand
Framework document including:
Specification of the logical and E/E-architecture of the HoD-Driveline,
Specification of the necessary interfaces, and
Specification of the functions of affected electronic control units.
This deliverable summarizes the key findings regarding the HoD framework in Chapter 5.2 including
the lessons learned during demonstrator implementation and real world testing. Throughout the
whole development process, the HoD-Framework was continuously refined. Primarily, the changes
affected the interfaces defined in D3.2. Several signals were added, e.g. due to safety and optional
man-machine interface requirements.
Based on the HoD framework specifications deliverable D3.4 shows that the HoD system is
successfully integrated and running in a truck-semitrailer vehicle. The key achievements reported in
this deliverable are:
Electric driveline tested in the trailer,
Successful overall commissioning of HoD semitrailer with two trucks proving interoperability,
Proof of technical feasibility of the initial technical approach, and
Proof of the applicability of the HoD Framework.
1 Access to D3.1 and D3.2 or parts of it can be granted upon request. Please contact the project
coordinator. It is currently under discussion to make D3.2 available via EUCAR.
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Contents
Contents .............................................................................................................................. 3
List of Acronyms ................................................................................................................... 4
1 Introduction ................................................................................................................... 5
1.1 Scope ..................................................................................................................... 5
1.2 Context ................................................................................................................... 6
1.3 Technical background / system overview ..................................................................... 6
2 Overall HoD Framework System Architecture ...................................................................... 7
2.1 ECU Functionalities ................................................................................................... 7
2.1.1 VCU .................................................................................................................... 7
2.1.2 TDMS .................................................................................................................. 8
2.1.3 TEBS ................................................................................................................... 8
2.1.4 EMG-ECU ............................................................................................................. 9
2.1.5 ESU-ECU .............................................................................................................. 9
2.2 HoD Interfaces ......................................................................................................... 9
3 Demonstrator driveline ................................................................................................... 10
3.1 TDMS .................................................................................................................... 11
3.2 Self-contained ESU .................................................................................................. 11
3.3 EMG and EMG inverter ............................................................................................. 12
3.4 Gearbox with integrated Clutch ................................................................................. 12
4 Commissioning and Test Results ...................................................................................... 13
4.1 Clutch operation ...................................................................................................... 15
4.2 Brake blending ........................................................................................................ 16
4.3 On-road testing ....................................................................................................... 17
5 Conclusions ................................................................................................................... 20
5.1 General Findings ..................................................................................................... 20
5.2 HoD-Framework ...................................................................................................... 22
5.3 Lessons Learnt ........................................................................................................ 23
6 Acknowledgment ........................................................................................................... 24
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List of Acronyms
Akronym Description
ABS Anti-lock Braking System
ASR see TCS
CC Cruise Control
DA Destination Address
EBS Electronic Braking System
EBSI Electronic Braking System Interface
ECU Electronic Control Unit
EMG Electric Motor Generator of the trailer
EMGI Electric Motor Generator Interface
ESU Energy Storage Unit of the trailer
ESUI Energy Storage Unit Interface
HoD Hybrid-on-Demand
HoDD Hybrid-on-Demand-Driveline
HoDF Hybrid-on-Demand-Framework
HV High Voltage
ICE Internal Combustion Engine
LV Low Voltage
MMI Man Machine Interface
PDU Protocol Data Unit (see e.g. ISO 11992 Part 3)
PF PDU Format
PS PDU Specific
PTO Power Take-Off
PTCH Positive Temperature Coefficient Heater
RCP Rapid Control Prototyping
SA Source Address
SLOT Scaling, Limit, Offset and Transfer function definitions in J1939
TCS Traction Control System
TDMS Trailer Driveline Management System
TEBS Trailer Electronic Braking System
TEMS Trailer Energy Management System
TDN Trailer Drivetrain Network
VCU Vehicle Control Unit
VCUI Vehicle Control Unit Interface
VDC Vehicle Dynamics Control
VEMS Complete Vehicle Energy Management System
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1 Introduction
1.1 Scope
This document describes the key developments and commissioning steps for the electric/electronic
and functional integration of the Hybrid-on-Demand (HoD) driveline in the truck-semitrailer vehicle
combination. The TRANSFORMERS project built one HoD semitrailer. After the functional integration,
this semitrailer is able to operate with two different trucks provided by the OEMs involved.
The following tasks were performed for both trucks:
implementing, testing and commissioning of a truck gateway that provides the necessary
vehicle control unit interface (VCUI) signals,
connecting the semitrailer with each truck electronically,
commissioning and debugging the VCUI including the gateways,
step-wise commissioning of all functional/control systems (e.g. clutch control, torque control
etc.),
overall system integration/commissioning and
steadily debugging and optimization.
Figure 1 shows an overview of the whole system. It consists of an electric motor/generator (EMG), an
energy storage unit (ESU), a transmission/clutch unit between motor and drive axle, and a main
Trailer Drivetrain Management System (TDMS) as well as several auxiliary ECUs. TRANSFORMERS
implemented this concept in the tested HoD semitrailer.
Figure 1: Logical system architecture of the HoD-Framework
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1.2 Context
Today’s trucks are designed and optimized towards a limited set of use cases. In contrast, future
trucks should provide optimized transport efficiency for each mission. Within this context, the
driveline is a key component featuring a promising potential for optimizing energy and, as a result,
transport efficiency on a transport mission basis.
Work package WP3 of the TRANSFORMERS project develops an innovative, highly efficient, and
mission-adaptable driveline for tractor-semitrailer vehicles. This so-called Hybrid-on-Demand-
Driveline (HoDD) enables hybridization of trucks by coupling them to a trailer with a built-in electric
drivetrain2. The key features are:
Fully functional hybrid driveline by coupling a conventional driven truck with a HoD-Trailer,
Electric driveline within the trailer including Electric Motor Generator (EMG) and Energy
Storage Unit (ESU),
Configurable trailer driveline for mission adaption by an interchangeable ESU,
Slim communication interface between truck and trailer in order to limit changes to the truck
to the maximum possible extent.
To support a fast dissemination of the HoDD concept a corresponding pre-industrial standard is
developed as well. This so called Hybrid-on-Demand-Framework (HoDF) shall ensure compatibility
and interoperability of different trucks and trailers by defining a system architecture as well as
communication, electric and, where necessary, mechanical interfaces.
Furthermore, the HoDF proposes interface definitions for trailer drivetrain components such as Electric
Motor/Generators (EMG) and Energy Storage Units (ESU) in order to provide a new level of planning
certainty for component manufacturers and to enable lively commercial competition.
The framework is summarized in D3.2. It will be reused and further refined in the EU-co-funded
project AEROFLEX. In addition, the framework shall be made available to EUCAR and suitable trailer
manufacturers associations. This is the first step towards presenting it to ISO, in this case ISO TC22-
SC31 WG4, via appropriate national mirror groups - potentially via the German VDA mirror group on
brakes and steering systems. The document could also be shared with other research groups.
This document focuses on the main development steps and tests performed to integrate the electric
drivetrain into the truck-semitrailer combination.
1.3 Technical background / system overview
In general, the HoD framework considers two vehicle combinations:
Case A. Standard truck without holistic Vehicle Energy Management System (VEMS) is
coupled to the HoD-Trailer (Figure 2),
Case B. Future truck with HoDF-compliant Vehicle Energy Management System is coupled to
a HoD-Trailer (Figure 3).
This distinction is necessary, because standard trucks are not designed for operation with driven
trailers. Hence, for Case A the trailer driveline is only activated in predefined scenarios, to avoid
interferences with vehicle dynamics and advanced fuel-saving technologies, like e.g. gear shifting
strategy, weight estimation, cruise control strategy, or ECO-Roll. In contrast to that, the truck’s VEMS
is fully responsible for operating the trailer driveline in Case B applications.
For a comprehensive description of the framework’s capabilities and features including considered
vehicle combinations and operating conditions/vehicle states of each case refer to deliverable D3.1
and D3.23.
Due to the very high complexity of Case B and limitations of readily available truck-semitrailer
interfaces like, e.g. ISO11992 and J1939, TRANSFORMERS demonstrates Case A only, where the
trailer itself is responsible for the energy management. In order to provide the intended system
2 For further details and background information, refer to the TRANSFORMERS deliverable D3.1 and D3.2.
3 Access to D3.1 and D3.2 or parts of it can be granted upon request. Please contact the project
coordinator.
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functionality and properly respond to driver demands the trailer only needs to read signals from the
truck’s VCU.
For compatibility reasons with legacy trucks, sending signals back to the truck is avoided. The system
implementation proved that this is possible in principle. However, for monitoring and test driver
feedback purposes (MMI) signals like, e.g. HoD driveline state, ESU state of charge, and system
errors, are transmitted to the truck.
Figure 2: Structure of the HoD-Driveline for a HoD-Trailer coupled to a standard truck
(Case A)
Figure 3: Structure of the HoD-Driveline for a HoD-Trailer coupled to a VEMS-Truck
(Case B)
2 Overall HoD Framework System Architecture
TRANSFORMERS developed a multi-domain system architecture that in principle supports both Case A
and B applications while taking key features like interoperability, mission-based rightsizing,
modularity, and interchangeability on component level into account. This section describes the overall
system architecture of the demonstrator, which is as close as possible to Case A as described in D3.2.
As an introduction for the subsequently described details, Figure 1 shows the logical system
architecture and the scope of the HoD system. The key component is the TDMS with its built-in TEMS.
It controls the trailer driveline depending on information received from trucks VCU, ESUs, EMGs, and
TEBS. The individual functions of the system components as well as the interfaces between the
components are described in the subsequent sections.
2.1 ECU Functionalities
This section provides a high-level description of the ECU functions. Due to the different capabilities
and features of HoD Case A and B the functionalities of the VCU is different as well. Nevertheless, the
TDMS, ESU-ECU, and the EMG-ECU are in principle the same for both cases.
2.1.1 VCU
2.1.1.1 Case A
In Case A the truck VCU is assumed to be state of the art, which means they are not able to control
the HoD-driveline in detail. Instead, the TDMS is in charge of managing the trailer drivetrain based on
parameters/signals received from the truck. The truck and its VCU need to provide the following
functions:
Detect whether a standard or an HoD-Trailer is connected to the truck,
Implementation of trailer retarder control according to ISO 11992-2, and
Implementation of the Case A VCU-Interface as specified in HoD framework description.
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2.1.1.2 Case B
In Case B the truck is equipped with a comprehensive VEMS, which is able to use the trailer driveline
as a propulsion and energy recuperation device. Hence, the trucks VCU is in charge of controlling the
trailer drivetrain as a braking and propelling device, and the VEMS performs the entire vehicle energy
management by using all devices available. The tasks of the VCU are:
Detect whether a standard or a HoD-Trailer is connected to the truck,
Implement the Case B VCU-Interface as specified in HoD framework description,
Reads all necessary information describing the drivetrain capabilities from TDMS,
Optimizes the energy flow of the entire vehicle, and
Engage all driving and braking devices available according to the results of the energy
optimization.
2.1.2 TDMS
The TDMS encapsulates the complexity and the component diversity of the HoDD and provides an
easy to use interface for trucks/tractors. This approach ensures a broad interoperability between
different trucks/tractors and trailers/semitrailers.
The TDMS enables the trailer driveline, only if a truck with the required VCU- and EBS-Interfaces is
detected. The interface detection is mandatory because they provide the necessary truck parameters
for driving and braking via the electric driveline of the trailer. Based on the “handshake” result, the
TDMS continues with Case A or Case B operation. Otherwise, the trailer driveline remains disabled4.
The applied energy management strategy of Case A itself is not part of the HoDF. However, since
standard trucks were designed without knowledge of driven trailers, using the trailer driveline for
energy recuperation and driving is limited to a set of predefined scenarios.
In general the functionality of the TDMS is independent of Case A and B operation mode. The tasks
are:
Implement the VCU- and EBS-Interface,
Detect the capabilities of the truck via VCU- and EBS-Interface handshakes,
If applicable, decide whether to use Case A or B operation mode or to disable the driveline,
Implement a Case A operation mode based on a basic energy management strategy
Implement a Case B operation mode that encapsulates the internal structure and
implementation diversity of the HoDD by providing a device interface, which reports overall
nominal, maximal, and current driveline performance parameters to the VCU,
Limit EMG driving and braking to approved driving scenarios, and
Ensure the intrinsic safety of the HoDD by monitoring and if required shutting down the
trailer driveline components.
2.1.3 TEBS
The Trailer-EBS is a central component for the safety of the vehicle combination. According to German
homologation authorities and the current requirements of ECE Regulation R13 (Revision 6, released
on 24. 06. 2009) it must be in charge of performing all braking actions including HoD-recuperation
within the trailer. The detailed safety investigations revealed further that not only HoD-braking must
be approved by the TEBS but also propulsion from the HoDD.
This approval is not only necessary for safety reasons but also for not disturbing internal monitoring
and error handling functions of the TEBS. The tasks that need to be added to state of the art
electronic braking systems are:
Safely disable the HoD-Driveline in any emergency situation (ABS-events, TSC-events,
emergency braking etc.),
Implement the brake-blending function that prefers braking via HoDD instead of using
service brakes,
Implement a mechanism for receiving and approving brake and driving requests of the TDMS
via EBS interface, and
4 This functionality is not implemented in the demonstrator vehicle. It implements Case A only.
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Due to safety reasons, the TEBS should be able to prohibit EMG propulsion and braking
directly without involving the TDMS.
2.1.4 EMG-ECU
The task of the EMG-ECU is to control the EMG internally and provide an easy to use interface for the
TDMS that encapsulates EMG complexity and diversity. This functionality should ideally be integrated
in the inverter controller, which belongs to the electric machine. Nevertheless, it was implemented as
separate control unit in the demonstrator vehicle for easier adaptation. The required functions are:
Implement the high-level EMG-Interface as specified in the HoD framework description
including a digital signals used by the TEBS to disable EMG braking and driving,
Ensure the intrinsic safety of the EMG,
Measure and report internal EMG data like e.g. voltages, currents, torques,
Perform all low level functions to
o put the EMG into operation,
o operate the EMG, and
o shutdown the EMG
Perform internal error management and provide error reporting, and as an option
Implement an EMG cooling control system.
2.1.5 ESU-ECU
The task of the ESU-ECU is to control the ESU internally and provide an easy to use interface for the
TDMS that encapsulates ESU complexity and diversity. This functionality should ideally be integrated
in the battery management system itself. Nevertheless, it was implemented as separate control unit
in the demonstrator vehicle for easier adaptation. The required functions are:
Implement the high-level ESU-Interface as specified in the HoD framework description,
Ensure the intrinsic safety of the ESU,
Monitor and report the ESU health status,
Measure and report internal ESU data like e.g. voltages, currents, state of charge,
Perform all low level functions to
o put the ESU into operation,
o operate the ESU, and
o shutdown the ESU
Perform internal error management and provide error reporting, and as an option
Implement an ESU thermal management system (cooling and heating).
2.2 HoD Interfaces
The ECUs above exchange the necessary information by means of CAN-based communication
interfaces. Subsequently, these interfaces are described briefly:
VCU-Interface (VCUI): Is the interface between VCU and TDMS. This interface provides two
modes to ensure interoperability with standard/legacy and VEMS trucks. If the TDMS detects a
standard truck, the VCUI switches to unidirectional mode. The TDMS only reads signals from
the VCU, which enables retrofitting solutions. If the TDMS detects a truck compliant to Case B
of the HoD framework, the VCUI is also sending messages to the truck. The TDMS reports trailer
driveline performance/capability parameters to the VCU and receives driving/recuperation
requests in return.
EMG-Interface (EMGI): Is the interface between TDMS and EMG. This interface is part of the
HoD framework to support the development of compliant EMGs. During operation, the TDMS
controls the EMG power-flow according to performance/capability parameters reported by the
EMG used.
ESU-Interface (ESUI): Is the interface between TDMS and ESU. This interface is part of the
HoDF to support the development of framework compliant ESUs. During operation, the TDMS
controls the ESU power-flow according to performance/capability parameters reported by the
ESUs available.
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EBS-Interface (EBSI): Is the interface between TDMS and EBS of the trailer. The trailer EBS
provides a brake-blending functionality, which receives brake requests from the truck EBS and
distributes them between service brakes and electric braking (recuperation by EMG). Therefore,
the TDMS reports brake-related performance/capability parameters and receives brake requests
from the EBS of the trailer. Furthermore, the trailer EBS sends additional signals like e.g. ASR
and VDC events via EBS-Interface.
3 Demonstrator driveline
The demonstrator driveline E/E-Architecture is designed according to the logical architecture
described in the HoD framework (see Figure 1) in order to prove the concept in general. Due to
findings in the project like, e.g. signal availability, required efforts and available resources,
TRANSFORMERS focuses on demonstrating Case A only.
Figure 4 shows the details of the specific implementation including the technologies used for the
interfaces. The implementation follows the HoD framework proposal to the maximum possible extent.
This includes already defined and widely adopted communication protocols like ISO11992 and J1939.
The only nonconformity in communication protocols is the VCU interface. Instead of implementing
ISO11992 Part 3, a J1939 bus is used. The main reason is the flexibility and a far greater pre-defined
signal pool that enables more experimental freedom and a faster development process during the first
implementation of the system. Nevertheless, TRANSFORMERS achieved a solution that can be
implemented with the already existing signals of ISO11992 Part 3 as well. The Case A functionality
remains the same. The only drawback is a limited driver feedback mainly resulting from missing
signals like e.g. ESU state of charge, HoD status, and applied torque.
The following sections describe the details of key components of the demonstrator implementation. In
particular, these are:
TDMS,
ESU,
EMG and EMG inverter, and
Gearbox with Clutch.
Chapter 5 of this report summarizes the conclusions and lessons learned from the demonstrator
implementation with respect to the HoD framework.
TRANSFORMERS developed constitutive parts of ESU, Control Box, EMG, and EMG inverter. The
gearbox/clutch and the trailer axle are third party products. All components are installed, functionally
integrated, and tested in the semitrailer and the two trucks respectively.
TDMSVCU
Truck EBSTrailer
EBS
ISO11992-2
EBS-Interface(J1939)
HoD Signal Routing
Existing Interfaces
VCU-Interface(J1939)
Gate-way
ESU EMG
Trailer Drivetrain Network(J1939)
Figure 4: Overall System Architecture of the truck-semitrailer demonstrator vehicle
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3.1 TDMS
As defined in the framework the TDMS-ECU is the central trailer drivetrain management system,
which implements all high-level control functions. Even though a high-performance rapid control
prototyping system is used all functions of the TDMS can be easily transferred to automotive ECUs.
The TDMS-ECU is mounted in a water-resistant box on the left main beam of the trailer. It can be
easily accessed and maintained. The ECU is connected to the trailer EBS, the ESU-ECU, the EMG-ECU
and the truck by means of the respective communication interfaces.
In general, the implemented functions follow the component task description of section 2.1.2.
However, the demonstrator neglects all Case B related functions and the detection of truck
capabilities. In future, the system can be augmented to Case B with reasonable efforts.
A key finding is that safety functions are not necessarily centralized in the TDMS. Instead, EMG and
ESU should be intrinsically safe, and the TDMS is responsible for safety functions on system level.
3.2 Self-contained ESU
According to the HoD-Framework the ESU is designed as a self-contained unit with minimal signal
interfaces to the outside (see Figure 1). The ESU features only mechanical and electrical interfaces,
since the battery air cooling and heating system is already installed inside the ESU housing.
Therefore, the housing provides a sealed and a non-sealed section. The sealed section contains the
battery, ESU-ECU, water pump and water heater. The non-sealed sections contain the heat exchanger
and the cooling fans, see Figure 5.
ECUDC
DC
rela
ys
PTCH
ESU-conditioning Fans
ESU-conditoining PTC-Heater
ESU-conditioning-pump
ESU-ECULV-backup-batteryLV-DC/DC
below PTCH
ESU-conditioning heat exchanger sealed
non-sealed
ESU-battery
Connectors
Figure 5: Schematic inside view of ESU housing
The HoD Framework requires the ESU to have a power supply, a communication, and an HV interface
only. However, the demonstrator needed additional connectors. For example, due to limited voltage
compatibility of several passenger car components (heater, water pump) it was necessary to convert
the trucks supply voltage (24 V) to the standard passenger car voltage level (12 V). This voltage
converter is installed in the battery housing as well. The 12 V supply voltage is used to power all
battery auxiliaries but also the components of the external main Control Box. Hence, an additional
12 V supply voltage output connector is attached to the ESU. This additional connector is not
necessary in a series application if the auxiliaries and control hardware is compatible the 24 V truck
supply.
Furthermore, the EMG cooling system uses a HV fan (400 V) to control the cooling power. Hence, it is
necessary to have a stub from the main HV circuit to the fan. In TRANSFORMERS this stub is
branched off within the ESU housing and the EMG cooling fan is connected to it.
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Due to these two reasons, the TRANSFORMERS ESU features two additional connectors compared to
the original HoD Framework design. Both connectors are not required in a next generation system.
This proves the feasibility of the slim electrical and communication interface of the ESU as defined in
the HoD framework.
The ESU features an internal ESU-ECU that controls all battery related functions like the cooling and
heating system as well as key safety features like e.g. additional HV switches. Furthermore, it
provides a CAN-based HoD framework compliant ESU interface to the trailer drivetrain management
(TDMS) ECU. In the demonstrator, this ECU translates between the ESU interface and the proprietary
communication protocol provided by the battery.
TRANSFORMERS uses a separate ESU-ECU to implement a HoD-compliant ESU interface. This ECU
communicates with the TDMS and the proprietary ECU of the battery. In a potential series application
a separate ESU-ECU is not required if a HoD-compliant ESU is used, which implements the ESU
interface itself. This reduces the number of ECUs as well as the system complexity and costs.
3.3 EMG and EMG inverter
The electric motor/generator (EMG) is driven by an intelligent EMG inverter. Within this document,
this whole unit is called EMG. The inverter is mounted to the inner side of the left main beam. This
position ensures that the HV harness is safely covered beneath the trailer and between the massive
ladder frame. The selected mounting position also improves electromagnetic compatibility due to the
shielding properties of the ladder frame.
The motor/generator itself is directly attached to the gearbox, which is also mounted to the ladder
frame of the trailer. A HV harness connects the motor/generator with the EMG inverter, which
communicates with the EMG-ECU using a framework compliant CAN-based EMG interface.
TRANSFORMERS uses a separate EMG-ECU to implement a HoD-compliant EMG interface. Similar to
the battery, this ECU communicates with the TDMS and translates the messages to the proprietary
ECU of the battery. In a potential series application a separate EMG-ECU is not required if a HoD-
compliant EMG is used, which implements the EMG interface itself. This again reduces the number of
ECUs as well as the system complexity and costs.
While the TDMS-ECU manages the drivetrain as a whole, the EMG-ECU controls the EMG on system
component level. For example, when the TDMS requires a certain torque, the EMG-ECU sets the
required clutch state and executes the torque request at the EMG by communicating with the EMG
inverter.
3.4 Gearbox with integrated Clutch
A gearbox was installed to make sure that the EMG operates in its most efficient operating range
most of the time in long haulage applications. The ratio of the gearbox is 4:1. In addition, the driven
axle differential gearbox has a ratio of 2.93:1 resulting in an overall gear ratio between EMG and
wheels of 11.72:1. In future applications an application specific electric machine design could make
the gearbox obsolete, allowing for a reduction in both weight and cost.
The gearbox is equipped with a dog clutch. This is a reasonable technology with respect to wear and
maintenance efforts. Nevertheless, due to the underlying technical principle it is impossible to open
the clutch as long as torque is applied. This was identified as key drawback from a safety perspective,
e.g. if the opening process is too slow in certain safety critical situations. However, test drives showed
that the clutch opens fast enough to ensure the required safety level.
The safety issue can also be solved by using a friction clutch that opens in any situation independently
of the currently applied torque. This increases wear, maintenance efforts, and potentially decreases
the drivetrain efficiency. Hence, further investigations are necessary to select the most suitable clutch
technology.
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4 Commissioning and Test Results
All system modules described in chapter 3 are mechanically and electrically integrated into the trailer
(see Figure 6 and Figure 7). Based on this system installation a step-wise commissioning process was
performed in order to achieve the system integration of the electric HoD driveline on a functional
level.
TRANSFORMERS successfully performed the following steps:
1. Commissioning of ESU including all management functions like, e.g. cooling, heating, and
safety.
2. Commissioning of the EMG and the EMG inverter initially using an external HV supply, later
with the ESU in the trailer.
3. Commissioning of the clutch to enable opening and closing the clutch by the EMG-ECU
4. Combining ESU, EMG, EMG inverter and clutch system to a fully functional electric drivetrain
by means of the TDMS-ECU
5. Combining the HoD-Trailer with the HoD-Trucks and commissioning the whole combinations
6. Commissioning of the EBS interface and the corresponding brake blending functionality
These steps required extensive function and software development efforts for TDMS-ECU, EMG-ECU,
ESU-ECU, VCU-Gateway and EBS-ECU. Each of these ECUs were equipped with a specific operating
system, state machines, error handling routines, controller, management, and safety functions. A
very close cooperation with internal partners and external partners led to a successful commissioning
of the whole vehicle combination. Finally, the trailer was successfully registered with the HoD-system
installed. This paved the way for the start of public road testing (see Figure 8).
Figure 6: Schematic plan view of the TRANSFORMERS trailer with the locations of important
components
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Figure 7: EMG, cardan shaft, and drive axle mounted in the trailer
Figure 8: TRANSFORMERS combination during public road testing
Drive Axle
Cardan
Shaft
Gearbox
and EMG
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4.1 Clutch operation
One important aspect during the commissioning of the HoD driveline was the correct operation of the
dog clutch, which can decouple the EMG from the drive axle. Due to the use of a dog clutch, there is
no slip between input and output once the clutch is closed. Nevertheless, before closing it, a certain
slip is required to make sure that the claws of the input and output shaft are not staying face to face
all the time preventing the clutch closing. Hence, the clutch handling is quite complex.
Figure 9 shows real world torque and speed measurement data of the HoD trailer driveline while
driving. EMG speed and EMG torque is plotted against the time while performing a clutch closing
process. The EMG speed control mode is activated after t=68.4 s, which adjusts the EMG speed to the
desired slip in the clutch. In the next step, the control mode is switched to torque control and the
clutch is closed approx. at 69.2 s. Shortly after the EMG speed matches the wheel speed of the driven
axle, which means that the clutch successfully closed. Now the actual driving or braking torque could
be applied, which is not shown in this figure. For safety reasons the maximum torque of the speed
controller was limited. Further optimization of the clutch closing process including the speed controller
has the potential of reducing the closing time significantly.
This diagram also shows that all driveline components are working together properly in the vehicle
combination.
Figure 9: Speed and torque measurements during a clutch closing process in the moving
vehicle during commissioning
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4.2 Brake blending
In order to maximize the recuperation potential the EMG needs to be used for braking as much as
possible. So two modes of braking are possible:
1. Pure electric braking: This mode provides the highest recuperation potential. With an
additional switch/lever/function, the driver can activate the braking of the EMG separately
from all other braking devices on the truck. Furthermore, Volvo integrated pure electric
braking into the trucks engine brake controller.
2. Brake Blending: For braking with the service brakes a brake blending functionality was
implemented by Knorr Bremse in the trailer.
The brake blending functionality was developed together with Knorr-Bremse. Its basic principle is
sketched in Figure 10. The trailer receives a target deceleration (shown in green) via the EBS
communication with the truck. This target deceleration is always fulfilled by the EBS. It uses the EMG
(Share Retarder in blue) as much as possible. If the currently applied torque by the EMG is not
sufficient, the EBS adds the friction brakes (shown in red) to an extent necessary to fulfill the target
deceleration. If the EMG capability is reduced, e.g. when the SoC reaches high levels, the friction
brakes take over the whole braking power. In case of ABS events, the EMG is switched off
immediately and the standard ABS algorithm is applied to the friction brakes only.
Figure 10: Schematic operation of the trailer brake blending5
5 B.Meurer, R. Klement, B. Queckenstedt, J. Harder and M. Mederer, “E-mobility entering semitrailers –
new requirements and impact on future semitrailer brakes” in XXXIV International µ-Symposium Brake
Conference, Bad Neuenahr, 2015
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4.3 On-road testing
After successful commissioning of all subsystems, test drivers performed first test runs on closed
tracks in preparation for the public road testing. The focus was the safety and controllability.
Therefore, test drivers checked the vehicle behavior and stability by several handling tests like e.g.
full EMG braking and propulsion, jack-knifing and functional tests of the implemented safety measures
as well as performance tests under normal operating conditions. These tests successfully proved the
stability of the vehicle and the proper functioning of the HoD driveline as a whole.
The results paved the way for public road testing and the registration of the semitrailer with the HoD
system installed.
Figure 11 shows measurement results of a test run of about 300 km. It shows the usage of the EMG
for braking and driving on an undulating highway road. The driving torque is limited to 50% of the
maximum torque to achieve a longer assistance for the ICE. For higher vehicle speeds the braking
torque also does not reach the full torque anymore, because of the power limitation of the EMG.
Figure 11: Measurement data of a 300 km test run on public road
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Figure 12 shows a driving detail from the above full test cycle. The driver demands propulsion torque
(shown in blue) from the ICE. This triggers the clutch closing process as shown above. After
successful closing of the clutch, the EMG applies torque to the driven trailer axle (shown in green).
When no torque shall be applied by the EMG anymore the clutch opens to minimize the drag torque at 𝑡 ≈ 60 𝑠 and 𝑡 ≈ 120 𝑠.
Figure 12: Closer look on activation and deactivation of the driving torque of the EMG
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Figure 13 shows a braking scenario from the above test cycle during a downhill slope. Again a
retarder braking torque request to the EMG (shown in red) triggers closing of the clutch before
actually applying the EMG torque (shown in green). Intermediate releases of the braking request do
not instantaneously trigger the clutch to open again. The torque request needs to remain zero for a
certain time before opening the clutch.
Figure 13: Closer look on activation and deactivation of the braking torque of the EMG
The above real world measurement figures show the successful operation of the HoD driveline system
in the trailer together with the TRANSFORMERS trucks. All systems work as planned also for long test
cycles of more than 300 km.
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5 Conclusions
This chapter summarizes the conclusions drawn from the first-time implementation of a HoD
framework compliant hybrid mission adaptable driveline. The first section presents the key findings in
general. The second section provides a set of interface signals for the HoD framework that proved to
be sufficient for a successful and safe HoD system operation.
5.1 General Findings
The TRANSFORMERS project developed a concept for a mission-adaptable hybrid drivetrain for long-
haulage applications. The key feature is an electric drivetrain that is completely integrated in the
trailer instead of the truck. The project proofed the feasibility of this approach not only from a
technical but also from a homologation point of view.
Besides the technical implementation of the intended approach, the homologation for public road use
was a key challenge. This is mainly because current regulations and safety standards do not cover
electric drivelines within trailers or semitrailers.
A key issue is ECE R13, which currently does not allow selective braking of individual trailer axles,
because electric/recuperative wear-free braking is not considered for trailers. In contrast, braking of
individual truck axles is allowed, e.g. with the retarder or engine brake.
TRANSFORMERS proposes that ECE R13 should to be modified. In order to enable the maximum
recuperation potential of the HoD approach it should be allowed to apply individual brake forces to the
axles of a vehicle combination to a certain extent. This would pave the way for pure electric braking
as well as energy optimal brake blending. In theory, these two functions are able to foster the whole
recuperative braking potential available before engaging the energy wasting friction brakes. From a
safety perspective, no stability issues were identified during the test drives with the TRANFORMERS
system configuration and component sizing. Nevertheless, it might be necessary to limit or control the
torque at the wheels in order to ensure the driving stability. This is a question for further research
especially if more powerful EMGs are used in the trailer.
The implementation showed that a Case A compliant semitrailer can be applied to legacy/standard
trucks with reasonable efforts. In principle, only a gateway is required that provides a small set of
signals to the trailer already available in modern trucks. Hence, TRANSFORMERS proved that
retrofitting solutions are possible in principle even without defining new communication interfaces.
Figure 14 shows the final proposal for a mission adaptable modular HoD system that could be applied
in near future. This proposal already supports the installation of several ESUs and EMGs while the
interface to the truck potentially remains unchanged.
HoD Signal RoutingEnergy FlowExisting InterfacesScope of Framework
VCU
Truck EBS
Trailer EBS
EBS-Interface(J1939)
ISO11992-2
EMGn EMGn EMGn
ESUn
ESUn
EMG-Interface
ESU-Interface
Gate-way
VCU-Interface(ISO11992-3)
TDMSwith TEMS
Figure 14: Proposed HoD system architecture for Case A
Nevertheless, Case B is the most promising approach for the future. A holistic and predictive vehicle
energy management system (VEMS) would be able to consider all available drivetrain components
and auxiliaries to minimize the overall energy consumption. This approach is hardly feasible with the
existing truck-trailer interfaces – namely ISO11992. According to the HoD framework Case B needs a
new high-bandwidth interface with appropriate signal and message definitions for implementation.
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The advantage of the HoD framework proposal is that only a new high-bandwidth VCU interface needs
to be designed. All other interfaces can be implemented as described for Case A. Figure 15 shows the
final TRANSFORMERS proposal of a Case B modular mission-adaptable HoD drivetrain.
HoD Signal RoutingEnergy FlowExisting InterfacesScope of Framework
VCUwith
VEMS
Truck EBS
Trailer EBS
EBS-Interface(J1939)
ISO11992-2
EMGn EMGn EMGn
EMG-Interface
Gate-way
VCU-Interface(new)
TDMS
ESUn
ESUn
ESU-Interface
Figure 15: Proposed HoD system architecture for Case B
Besides these key findings, TRANSFORMERS summarizes further knowledge gain as follows:
The implementation phase proved that the HoD framework already provides reasonable
interfaces to EMG and ESU. A series application could require a more detailed and extended
specification. Nevertheless, the framework has the potential to support the development of
framework compliant components in future and can serve as a starting point for an industrial
standardization process.
The successful system integration of the HoD trailer with two trucks from different OEMs –
Volvo and DAF – proofed the interoperability of the proposed drivetrain concept. Every truck
that implements a HoD framework compliant VCU interface is potentially able to benefit from
the HoDD. Hence, it is possible to create a distributed hybrid drivetrain by coupling a
conventionally propelled truck with a HoD trailer.
It is feasible to integrate a high performance electric drivetrain in a semitrailer. The packaging
is challenging but easy compared to hybrid drivetrains completely integrated in trucks. In
particular it is possible to find significant space for the ESU beneath the trailer, which would be
challenging in a hybrid truck.
The EMC laboratory measurements showed that the HV system installation is compliant to
current regulations and requirements. Since the installation considered basic EMC rules and
HV installation guidelines, the HoD vehicle combination passed the EMC test at the first
attempt.
Even though the HoD Case A can operate without any man-machine-interface (MMI) it could
be necessary to provide some information to the driver. The demonstrator displays several
signals (see Error! Reference source not found. in section 5.2) in order to support the test
engineers with status and performance information. TRANSFORMERS concludes that this topic
needs further investigations, e.g. in follow-up projects like AEROFLEX.
In principle, the HoDD enables pure electric driving for the vehicle combination. Tests proofed
the feasibility. Further investigations are required for future implementation. Currently,
TRANSFORMERS assumes that only Case B can provide this feature since this feature requires
additional signals to be sent from truck to trailer that are currently not available in ISO 11992.
Dedicated test drives proved that at least one trailer axle can be propelled safely assuming the
performance parameters of the demonstrator driveline. For example, it was not possible to
jack-knife the combination. It must be investigated if this statement holds true for drivelines
with higher performance as well.
Since the TDMS mechanically disconnects the HoDD in all driving stability events (ESP, ABS
intervention, etc.) the system does not influence the vehicle stability by its operation.
Brake manufacturers can adapt their EBS and provide a break-out CAN interface that
transmits the necessary data originally sent from truck to trailer based ISO11992 part 2. This
is important since ISO11992 part 2 defines a point-to-point connection between truck and trailer EBS, which prohibits connecting other devices.
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Brake manufacturers are able to implement brake blending based on the EBS interface
described in the HoD framework. The project proved the feasibility of two braking strategies.
The first one evenly distributes the driver brake request among the three trailer axles and is
completely in line with current regulations. The second one is significantly more efficient since
it uses recuperative braking at the HoD axle to a maximum possible extent before applying
the service/friction brakes. Even though the second strategy recuperates more energy, current
regulations in principle do not cover different/selective brake torques at the trailer. Since this
is a requirement for the trailers service brake, there is a legal grey area if it comes to
recuperative braking devices.
5.2 HoD-Framework
During the commissioning of the HoD vehicle combinations, it was not necessary to refine key ECU
functionalities defined by the HoD framework. Nevertheless, the initial interface definitions required
several additional signals.
Especially in the trailer, some control functions can be located in different ECUs resulting in design
freedom for the electric driveline in the trailer. For example, the clutch control can be part of the EMG
system or the TDMS. While the first option enables a better functional encapsulation, the second
option is more flexible in terms of energy management and optimization. For the control functions in
question further investigations are needed to determine the best solution. This still could change the
signals of the involved interfaces. The changes are expected to be rather small, and straightforward
to implement.
The HoD-Framework is going to be used and refined in the follow-up project AEROFLEX. Furthermore,
it is planned to make the framework available to EUCAR and trailer manufacturer associations.
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5.3 Lessons Learnt
Subsequently, this section summarizes the lessons learnt during the course of the project:
Integrating a battery in a semitrailer is comparably easy. The integration of a HoDD is a
challenge especially because of:
o unavailable key components like light weight driven trailer axles,
o construction changes and regulatory constraints (current regulations do not really
allow pure electric braking). It is questionable if suitable and affordable components
and regulation are available in near future.
A reasonable alternative would be to install the battery on the trailer and the e-driveline into
the truck. OEMs develop e-drivelines for trucks anyhow. This approach would ease the
packaging problem, reduce the overall system complexity and costs (fewer electronic devices),
and is expected to be in line with current regulations. The downsides are
o a robust HV connection between truck and trailer needs to be established
o the trailer does not provide a driven axle that could improve traction capabilities e.g.
on slippery roads
If traction on the trailer is not a key feature for the customer, the recuperated energy could be
used for powering, e.g. trailer cooling units or providing energy for hotel functions like heating
venting and air conditioning during resting times. This would result in a significantly smaller
ESU. The power rating and size of the EMG is expected to be smaller as well. Further
investigations are necessary for a business case investigation.
The HoD framework proposes slim interfaces for ESUs and EMGs. If these could be
standardized, the market introduction of compatible devices can be accelerated. This holds for
the HoD distributed driveline but also for hybrid drivelines completely installed in the truck.
Current regulations do not consider recuperative braking in trailers. Efforts should be put into
adapting mainly ECE R13 in order to enable innovative recuperation solutions. Pure e-braking
at single axles is the most critical point since it enables a significantly higher recuperation
potential (approx. factor 3-5).
For safety and efficiency reasons (drag torque) TRANSFORMERS disconnects the EMG
mechanically by means of a clutch. It would be very interesting to investigate solutions that do
not need this clutch, e.g. by using a separately excited electric machine. Such solutions would
result in lower costs, less complexity, less weight while maintaining the safety of the system.
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6 Acknowledgment
This project is co-funded by the 7th FP (Seventh Framework
Programme) of the EC - European Commission DG Research
http://cordis.europa.eu/fp7/cooperation/home_en.html
http://ec.europa.eu
PROJECT PARTICIPANTS:
VOLVO VOLVO TECHNOLOGY AB(SE)
BOSCH ROBERT BOSCH GMBH
DAF DAF TRUCKS NV
FEHRL FORUM DES LABORATOIRES NATIONAUX EUROPEENS DE RECHERCHE ROUTIERE
FHG FRAUNHOFER-GESELLSCHAFT ZUR FOERDERUNG DER ANGEWANDTEN FORSCHUNG E.V
IFSTTAR INSTITUT FRANCAIS DES SCIENCES ET TECHNOLOGIES DES TRANSPORTS, DE
L'AMENAGEMENT ET DES RESEAUX
IRU IRU PROJECTS ASBL
P&G PROCTER & GAMBLE SERVICES COMPANY NV
SCB SCHMITZ CARGOBULL AG
TNO NEDERLANDSE ORGANISATIE VOOR TOEGEPAST NATUURWETENSCHAPPELIJK ONDERZOEK (NL)
UNR UNIRESEARCH BV (NL)
VEG VAN ECK BEESD BV
VIF KOMPETENZZENTRUM - DAS VIRTUELLE FAHRZEUG, FORSCHUNGSGESELLSCHAFT MBH
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