CHALLENGES AND APPROACH
The previous ECU-centric system
architecture with its point-to-point com-
munication infrastructure is no longer
an effi cient design approach. Automo-
tive electronic systems are becoming
truly distributed to achieve increased
system functionality by tightly coupling
ECUs. These changes encourage a signi-
fi cantly revised approach to automotive
system test. This shift in system design
is refl ected in the evolution of ISO26262
[1], derived from IEC61508 [2], with its
focus on functional safety assurance. It
has a huge impact on automotive test
platforms, Hardware-in-the-loop(HiL)
simulation, test platform provider. Audi
is responding to these challenges by
radically re-thinking the architecture of
the HiL test platform and defi ning a
next generation approach.
The new approach introduces the con-
cept of a HiL-Bus to integrate the functio-
nality of multiple existing HiL sub-sys-
tems and meet the needs of a function-
centric test environment.
FUNCTIONALITY THROUGH
DISTRIBUTED ECUS
We need to start by describing the shift
towards function-centric testing from the
perspective of automotive design. Here
are a few examples:
: A simple “air bag computer” fi res the
air bags at the time of a crash. This ECU
now becomes an integral element of a
complex safety sub-system with more
safety functions. The safety computer
has to have an automatic crash detec-
tion capability (“Audi pre-sense”) and it
has to perform fully automated braking
support, deploy the air bags, tension the
aU t H o rS
CONSTANTIN BRÜCKNER
is working in the department
Hardware-in-the-Loop Functional test at
audi aG in Ingolstadt (Germany).
BETTINA SWYNNERTON
is technical Manager eMea at real-time
Innovations Inc. in Sunnyvale (USa).
A NEW ARCHITECTURE FOR AUTOMOTIVE
HARDWARE-IN-THE-LOOP TEST
as automotive electronic system design evolves, so must the HiL testbench and automotive test platforms. the
fundamental functional design approach has been modular and eCU-centric, but the eCU count has steadily
increased. the next big shift is to achieve functionality through the integration of multiple eCUs. audi is responding
to these challenges by radically re-thinking the architecture of the HiL test platform and defi ning a next generation
approach. the new approach introduces the concept of a HiL-Bus to integrate the functionality of multiple existing
HiL sub-systems and meet the needs of a modular best-in-class test ecosystem. By using a data orientedapproach
the complexity of the testbench is reduced making it easier to integrate hardware and software products from
different vendors. one of the enabling technologies (Connext ddS) is developed by real time Innovations Inc.
DEVELOPMENT Hardware-In-tHe-Loop
4 0
Hardware-in-the-Loop
seat belts, close the windows and roof
and move seats into an upright position.
: Dedicated ECUs for radio, navigation
or rear seat entertainment are evolving
into a “main entertainment unit.”
: Dedicated ECUs for the reading light,
interior light and body electronics are
combined into a “body control
module” and enriched with new capa-
bilities such as bending light, matrix
LED head light, camera-based night
vision and traffic sign detection.
This is a different way of looking at
vehicle development. It has a fundamen-
tal impact on the way in which the auto-
motive HiL test platform needs to be
designed. It requires a much more flexi-
ble and scalable test environment that is
capable of bringing together many diffe-
rent HiL simulation platforms into one
tightly integrated test platform.
A NEW HiL – DESIGN OBJECTIVE
The HiL test platforms available from the
ecosystem of platform suppliers for a wide
range of automotive sub-system simulati-
ons (such as powertrain, engine manage-
ment, braking and air bag deployment),
have evolved with the historic require-
ments of the stand-alone function-centric
ECUs. However, new test requirements of
the full car HiL simulation and function-
centric test environment need something
new and different to validate the func-
tions of future cars.
Audi identified that different HiL test
platforms from different suppliers offer
differing levels of fidelity with respect
to their simulation and test capabilities.
New highly integrated and distributed
functions need a highly distributed HiL
ecosystem. Multiple HiL sub-systems
provided by different suppliers have to be
tightly coupled to reflect the integrated
distributed function being tested,
1
. The
HiL suppliers may only be providing the
very best sub-system HiL simulation and
test capabilities for a fraction of the overall
function test objective. This would require
the automotive vendor to compromise the
full system test fidelity if they source the
entire platform from one supplier.
Why can’t the automotive company
select the best HiL-sub-systems and bus
simulations from across the industry to
build a new best-in-class function test HiL
platform? This is the question at the heart
of Audi’s research into their Modular HiL
Next Generation mHIL-NG project.
This project is looking beyond test
platforms; it wants to be able to bring
the advanced model-based and compu-
ter-aided development tools used in
actual ECU development into the HiL
ecosystem.
THE NEW HiL TEST CHALLENGES
Automotive HiL must stay ahead of the
developments in ECU integration, or at
least integrate existing ECU development
processes to keep pace with the rate of
change in automotive development.
A next generation automotive HiL
must be able to deal with:
: increasing scale of ECU function
simulation
: increasing complexity of functional
test requirements
: integration of a wide variety of HiL
modules into function sets
: integration of ECU modeling platforms
for test validation and stimulation
: standardised and simplified interface
for user interaction and control
: signal measurement and stimulation
across different modules.
Perhaps the most significant decision
that Audi has made is to base the new
HiL architecture on an open standard
middleware or bus. The new distributed
functional test demands, and Audi’s qua-
litative objective (and motto), “Truth in
Engineering,” can only simultaneously
be met using open market-accessible
integration technology.
Audi searched for a software infra-
structure that is real-time capable,
scalable, field proven to be reliable and
an open standard. After researching
available options, Audi identified the
open standard DDS (Data Distribution
Service) from the OMG [3] and the con-
formant implementation from Real-Time
Innovations, which not only met these
criteria, but was also able to deliver the
required virtual bus architecture. RTI
Connext DDS is also demonstrably inte-
grated with leading modeling environ-
ments widely used in software
development.
A DATA-CENTRIC CORE
FOR THE HiL-BUS
At the 2013 VDI automotive electronics
conference in Baden-Baden, the keynote
[6] emphasised a huge change in the
automotive software development para-
digm. Specifically, to deal with the
complexity of future electronic systems
design, the industry must move to a
data-centric approach. Audi also noted
that viewing the integration bus as a
software databus was the only way
to bring the best-in-class elements of
existing proprietary HiL sub-system
suppliers together with the modeling
and development tools used in ECU
development.
Every HiL testbench or sub-system is
seen as a module. Each module either
produces or consumes data, and the
data is important to the test system. The
changing state of data represents chan-
ges in system or sub-system state. A
state change is at the core of being able
to understand and validate whether a
suite of ECUs meet a specific functional
objective. A data-centric system infra-
structure,
2
, makes state changes visi-
ble on the software bus by updating
data values, just as a database in an
enterprise system updates its rows and
columns. It sustains a real-time view of
the system-wide state that is immedia-
tely accessible to all sub-systems.
With a data-centric infrastructure in
place, Audi maintains control of the
communication infrastructure and can
decide how to evolve the HiL-Bus to
meet functional test needs in a simple
and elegant fashion. This sort of de-cou-
pling capability facilitates the evolution
of a true plug-and-play automotive test
platform. The ability to rapidly bring
together multiple HiL system suppliers
HiL
-Bus
HiL-Testbench
Vendor A
HiL-Testbench
HiL-Testbench
Vendor B
HiL-Testbench
Vendor C
HiL-Module
Vendor A
HiL-Module
Vendor B
HiL-Module
Vendor C
1
Audi HiL-Bus – Connecting Multi-Vendor
HiL Testbenches
41
03I2014 Volume 9
Hardware-in-the-Loop
into a single functional test environ-
ment has the potential for huge savings
in set-up time and cost and simultane-
ously supports the best-in-class modular
selection objective. Of course, it must
be simple and easy to connect different
supplier HiL solutions onto the HiL-Bus
to investigate multiple combinations of
HiL test platforms to derive the optimal
functional test platform.
The timing of when a signal change
in a module occurs is as important to a
real-time system as the fact that the
signal change occurred. To this end, the
DDS standard [4] includes Quality of
Service (QoS) capabilities that provide
the ability for applications to specify
their timing constraints and notify
applications if these constraints are not
satisfied. These real-time-capabilities
are important for measuring signals
across different HiL-modules.
AN OPEN BUSINESS MODEL
RTI Connext DDS is the implementation
of the open standard DDS that Audi
chose to work with. Apart from its vali-
dated real-time performance, its field
proven robustness and the depth of its
supporting development tools, RTI Con-
next DDS has one other key value: its
business model. As Stan Schneider (CEO
of RTI) stated in his keynote at a FACE
[5] technical symposium, „RTI is com-
mitted to an open architecture that
expands thedselection of applications
and reduces the cost of procurement,
system integration, upgrades and tech-
nology refresh, while significantly redu-
cing the total lifecycle cost“. To foster
an ecosystem of HiL simulation sup-
pliers we must maintain a low barrier to
entry for them to integrate to the Audi
HiL-Bus.
Audi provides data definitions to its
partners for interfacing to the HiL-Bus.
This lets them be part of a wider func-
tional Automotive HiL test platform, but
the HiL supplier still needs to connect
at the software infrastructure level. RTI
Connext DDS uses an Open Community
Source (OCS) licensing model. Through
OCS, any Audi partner can gain access
to the basic DDS software (including
source) at no charge and with royalty
free deployment. The software license
has none of the copyleft-style restric-
tions typical of many open source soft-
ware products. This makes the integra-
tion of new supplier-modules very easy
and comfortable.
THE IMPORTANCE OF DECOUPLING
The other benefit of the real-time-capa-
ble data-centric infrastructure of the
HiL-Bus is the highly decoupled modular
development capabilities it supports and
enforces. It is very important in an open
architecture such as the HiL-Bus that
independent, modular development can
be advanced by contributing developers
and ecosystem partners. DDS acts as the
communication and real-time arbiter in
this software bus system. Its true peer-
to-peer architecture means that it sup-
ports an “any order” boot sequence. DDS
provides a discovery mechanism that
treats every modular participant as both
a sink (subscriber) and a source (publis-
her) of data (and thus state changes) to
the wider system of systems. By moving
the communication complexity into the
bus, Audi massively reduces the integra-
tion problems of connecting different
sub-systems developed by different part-
ner companies using different methodo-
logies. Now, integrators just have to cha-
racterise their data outputs and source
requirements and align them with the
Audi data model. Dr. Jan Effertz of VW
Research described the benefits of DDS
in their driver safety systems research
as, “Think about the data, not how to
communicate” [6]. Developers just place
data on the HiL-Bus or take it from the
HiL-Bus. They do not need to think
about how to communicate with a speci-
fic end-point which may have attendant
unique requirements for message
exchange,
3
.
Actuator
Display
App
Control
App
Sensor
Sensor
OMG Data Distribution Service (DDS)
Application
Application
Savings
Application logic
Application logic
Data caching and
state management
Message generation
and parsing
Message generation
and parsing
Data caching and
state management
Data-centric
middleware
Message-centric
middleware
Network
Message filtering
Message filtering
2
The OMG DDS databus architecture
3
Message-centric vs data-centric middleware [5]
DEVELOPMENT Hardware-In-tHe-Loop
42
TEST AUTOMATION
Automotive vendors such as Audi have
invested many years in their test automa-
tion environment. Those environments
include many proprietary setup tools
that meet the special needs of their
manufacturing and development organi-
sations, and an incumbent workforce
skilled with those tools. The introduction
of the HiL-Bus must embrace existing
user interfaces to the test platform and
make it simpler to develop new test
capabilities. Audi calls the abstraction
layer their “testbench manager.” Such
tools can be characterised by their data
use, and easily interfaced, unchanged,
onto the HiL-Bus,
4
, as simply as atta-
ching a plug adaptor for power when tra-
velling abroad.
The testbench manager is a software
library developed by Audi. It consists of
two parts: the HiL-Bus interface and the
test-bench manager itself. This library
is integrated in every sub-module of a
testbench,
5
, and enriched by vendor
specific glue code for accessing proprie-
tary module functions via the HiL-Bus.
REFERENCES
[1] ISo 26262, road Vehicles – Functional Safety,
part 1 – 10, 2011/11
[2] IeC 61508, Functional Safety of electrical/elect-
ronic/programmable electronic Safety-related Sys-
tems, part 1- 7, 2011/02
[3] object Management Group – data distribution
Service for real-time Systems v1.2 http://www.omg.
org/cgi-bin/doc?formal/07-01-01
[4] Kellerwessel, C.: Connectivity im Fahrzeug –
nutzen und Umsetzung. In: 16
th
International Kon-
gress „elektronik im Fahrzeug“, Baden-Baden, Ger-
many, 2013/16/10
[5] Schneider, S.: FaCe Consortium F2F meeting
June 42013 - http://online.wsj.com/article/pr-Co-
20130530-907778.html
[6] effertz, J.: Interview wrt ddS 18/04/12 https://
web2.sys-con.com/node/2251954
[7] Schacker, C.: data-Centric Middlewarehttp://
www.rti.com/docs/rtI_data_Centric_Middleware.
pdf
HiL-Module
Glue code
Proprietary software
HiL-Bus
Distributed abstraction layer
(testbench manager)
including HiL-Bus-interface
4
Testbench manager as distributed abstraction
layer
HiL-Modules
HiL-Operations
Application module
Glue code
PSM
DDS
Application module
Glue code
PSM
DDS
Application module
Glue code
PSM
DDS
Application module
Glue code
PSM
DDS
Application module
Glue code
PSM
DDS
Smartphone
Road
simulation
Sensor
simulation
Traffic
simulation
Driver
simulation
Tablet
Test automation
Experimental
software
Control station
Vendor A
Data logger
ECU
Manager
Tester
Tester
Application module
Glue code
PSM
DDS
Application module
Glue code
PSM
DDS
Application module
Glue code
PSM
DDS
Application module
Glue code
PSM
DDS
Virtual environment modules
ECU
ECU
ECU
ECU
ECU
Application module
Glue code
PSM
DDS
Application module
Glue code
PSM
DDS
Application module
Glue code
PSM
DDS
Application module
Glue code
PSM
DDS
Application module
Glue code
PSM
DDS
Application module
Glue code
PSM
DDS
Vendor A
Vendor B
Vendor B
Vendor C
5
Audi HiL-Bus based logical testbench
architecture
4 3
03I2014 Volume 9
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