=Paper=
{{Paper
|id=Vol-1675/paper4
|storemode=property
|title=Interfacing Real-Time Systems for Advanced Co-Simulation -- The ACOSAR Approach
|pdfUrl=https://ceur-ws.org/Vol-1675/paper4.pdf
|volume=Vol-1675
|authors=Martin Krammer,Nadja Marko,Martin Benedikt
|dblpUrl=https://dblp.org/rec/conf/staf/KrammerMB16
}}
==Interfacing Real-Time Systems for Advanced Co-Simulation -- The ACOSAR Approach==
https://ceur-ws.org/Vol-1675/paper4.pdf
Interfacing Real-Time Systems for Advanced
Co-Simulation – The ACOSAR Approach
Martin Krammer, Nadja Marko, and Martin Benedikt
VIRTUAL VEHICLE Research Center, Inffeldgasse 21a, 8010 Graz, Austria
{firstname.secondname}@v2c2.at
http://www.v2c2.at
Abstract. Virtual system development is getting more and more impor-
tant in a plenitude of industrial domains to reduce development times,
stranded costs and time-to-market. Co-simulation is a particularly promis-
ing approach for modular and interoperable development. In practice
the integration and coupling of real-time systems (especially systems of
distributed hardware-in-the-loop systems and simulations) still requires
enormous efforts. The aim of the ACOSAR project is to develop both
a non-proprietary Advanced Co-simulation Interface (ACI) for real-time
system integration and an according integration methodology. These pro-
posals shall act as a substantial contribution to international standard-
ization as the Functional Mock-up Interface (FMI) standard laid the
foundations for simulations of physical systems. The results of ACOSAR
will lead to a modular, considerably more flexible, as well as shorter
system development process for numerous industrial domains and will
enable the establishment of new business models.
Keywords: co-simulation, simulation, real-time, ACI, FMI, integration
1 Introduction
With this paper the ACOSAR project is introduced. ACOSAR is the abbrevia-
tion for “Advanced Co-Simulation Open System Architecture". It is an ITEA 3
framework project. ITEA is the EUREKA cluster programme supporting inno-
vative, industry-driven, pre-competitive research and development projects in
the area of software-intensive systems and services (SiSS). SiSS are a key driver
of innovation in Europe’s most competitive industries, such as automotive, com-
munications, healthcare and aerospace1 . ACOSAR is the first project of its kind
being proposed and approved in Austria. It is led by VIRTUAL VEHICLE, a
renowned automotive research center located in Graz, Austria. As of April 2016,
the project is in the midst of its first year. Table 1 shows the key project facts
at a glance.
ACOSAR responds to a strong market request in a plenitude of industrial
domains: a consistent, seamless (virtual) system development and validation. In
order to achieve this, ACOSAR uses a modular co-simulation approach, sup-
porting flexible system development by its modular characteristics, to integrate
1
http://www.itea3.org
Name ACOSAR: Advanced Co-Simulation Open System Architecture
Framework ITEA 3
Funding National funding agencies, total budget 7.9 million e
Consortium 15 partners from 3 countries (Austria, France, Germany)
Structure 3 OEMs (Porsche, Renault, and Volkswagen)
1 supplier of automotive systems, components (Bosch)
4 industry providers (AVL, AVL-AST, ETAS and dSPACE)
2 simulation tool vendors (Siemens PLM Software, ITI)
3 SMEs (MEDS, TWT, and ITI)
1 research center (VIRTUAL VEHICLE)
3 academic (Leibniz University Hannover, RWTH Aachen, and Ilmenau
University of Technology)
Leader VIRTUAL VEHICLE Research Center, Austria
Period September 2015 – August 2018
Website http://www.acosar.eu
Table 1. The ACOSAR project at a glance.
domain-specific subsystems. In development stages, where real-time (RT) sys-
tems have to be integrated into simulation environments, huge configuration
effort is still necessary due to complex system topologies, large numbers of sig-
nals, and numerous different parameters of algorithms for signal processing.
Drivetrain Cooling Li-Ion
Battery
Functional Framework
Smart Functions
FMU (e.g. adaptive coupling)
Simulation Simulation ACI Communication Layer
Environment Environment
FMU
(e.g. engine
testbench)
Wireless Wired Interprocess
Co-simulation Environment
(Co-) Simulation Environment Communication Communication Communication
(e.g. BlueTooth®) (e.g. CAN) (e.g. shared mem.)
Ordinary User PC or Computing Cluster
Communication Systems RT System
Proprietary Interface Functional Mockup Interface (FMI) Advanced Co-Simulation Interface
Fig. 1. The main idea behind ACI is strongly related to FMI, but ACI relates to a
completely different domain of application. In particular, FMI addresses integration
of simulation models (only) within the non-RT or the RT domain. In contrast, the
major focus of ACI is on integration of RT-systems into simulation environments by
interconnecting the RT with non-RT or RT domains.
August 2014 / Benedikt ACOSAR - Project proposal © VIRTUAL VEHICLE 3
2 Goals and Objectives
To enable effective and efficient RT-system integration, ACOSAR will provide
innovations on different levels. First, ACOSAR focuses on the specification of a
non-proprietary open RT-system interface, a so-called Advanced Co-simulation
Interface (ACI) for sharing relevant information for efficient and safe operation
of RT-systems, e.g. test beds. A communication architecture (including protocol)
will be defined, which will be independent of the used communication systems. A
functional framework for coupling strategies, highly efficient data transmission,
and support of semantic data processing will supplement this. These aspects are
illustrated in Figure 1. Furthermore, a comprehensive methodology for seamless
integration of RT-systems during verification, test and validation phases within
the development cycles of the classical V-process model will be defined. This
methodology will support already existing tool chains, model-based systems en-
gineering approaches, and methods for easy adaption of simulation tools from
early development phases to late ones. The latter is supported by a continuous
transfer of knowledge as progress in product development is made.
The open ACOSAR ACI not only will make it possible to extend cloud-
based simulation applications towards the RT domain, but also to select and
apply best-in-class RT-systems to compose a dedicated optimum overall system
for specific present problems with reduced error proneness (e.g. interconnection
of distributed HiL test beds for specific engineering purposes). Besides spread-
ing such kind of solutions for the benefit of other domains, this also will help to
improve the social acceptance of new technologies, e.g. autonomous driving. Fur-
thermore, research on smart functionality including adaptive coupling strategies
will be stimulated.
The major results of ACOSAR will be freely available.Thus, ACOSAR con-
tributes to interoperability and open access. It also supports competition and
will lead to a modular, more flexible, as well as much shorter system development
process and will enable new business models.
The transfer of project results into standardization is the key goal of ACOSAR.
Therefore, partners from relevant standardization committees (e.g. FMI/Modelica
Association, ASAM) are actively involved to jointly create solutions and exten-
sions to existing standards. To further bridge the gap between the automotive
domain and other domains, leading partners from e.g. aviation and rail will be
invited to ACOSAR as associated members. Not at least, ACOSAR’s innova-
tions will enable small and medium-sized enterprises (SME) and suppliers from
different domains (software tools, HiL systems, test beds,. . . ) getting access to
major industries, resulting in more competitive markets in the long term.
3 Related Work
The ACOSAR consortium reviewed numerous research projects, scientific pa-
pers and industry standards with respect to all relevant fields. This includes
topics like modeling and simulation of continuous, discrete and hybrid systems,
co-simulation and coupling mechanisms, communication systems, real-time ap-
plications as well as systems and safety engineering. The majority of these liter-
ature review results will be published in deliverable D1.1.
One of the most relevant standards considered for investigation is the func-
tional mock-up interface (FMI) standard [6]. Version two was released in 2014.
FMI is a tool-independent standard to support both model exchange and co-
simulation of dynamic models2 . Its main goal is to improve the exchange of
simulation models between suppliers and OEMs within the automotive industry.
Recent relevant publications include [8] on FMI-based distributed multi-
simulation, or [3] on requirements for hybrid co-simulation standards. Regarding
issues of coupling and practical applications of co-simulation, [9,1,2,12] were
taken into account. Publications covering industrial use cases are described
in [10,7,5,4].
Some of the most relevant research projects included AGeSys, ASTERICS,
AVANTI, INTO-CPS, MODELISAR, OPENPROD, ACORTA 1 and ACORTA 2,
Transformers and VeTeSS.
4 The ACOSAR Approach
4.1 Project Overview and Structure
An organizational overview is given in Figure 2. Work package (WP) 1 is named
"Open System Architecture Requirements". It builds the foundation for all sub-
sequent WPs and unifies the stakeholder’s views through specification of re-
quirements (for this approach see Section 4.4). WP 2 is titled "Real-time system
integration methodology". It focuses on system level activities, including sys-
tem modelling and configuration approaches, as well as tool integration issues.
WP 3 deals with "Simulation tool interfaces", and is targeted towards the needs
of software tool vendors. WP 4 specifies the "Real-time system interface", and
takes hardware and testing systems into account. WP 5 focuses on the "Commu-
nication protocol", which is used to interconnect multiple systems via commonly
used communication media. Finally, WP 6 is intended to condense the results
of WPs 3-5 and master the task of creating a first version of the ACI specifi-
cation. Industrial and scientific demonstrator applications are planned, set up
and assessed within WP 7 named "Application use-cases and assessment". Dis-
semination, standardization, and exploitation activities take place within WP 8,
throughout the entire run-time of the project. WP 9 is concerned with overall
project management activities.
4.2 Expected Outcomes of Workpackages and Deliverables
The outcome of WP 1 are sets of requirements (D1.1: Open system architec-
ture requirements) targeting different application levels and levels of abstraction.
They build on top of current standards, state-of-the-art technology, and best in-
dustry practices. The project’s 9 use cases of WP 7 support these steps. More
on this in Section 4.4. The use cases will be assessed in WP 7’s deliverable D7.1:
Documentation of use cases, tests, configurations, and measurement results, to
demonstrate the impact of ACOSAR’s developments.
WP 2 defines the understanding of system simulation in the project, and as-
sesses properties of interfaces and subsystems. If these can be described properly,
2
http://www.fmi-standard.org
ACOSAR
WP 9 - Project Management
Current standards Funded associated projects Associated member groups
FMI, ASAM XiL-API, XCP, etc. Modelisar, ACoRTA, etc. Aviation, Rail, Maritime, etc. WP 8 – Dissemination
& Exploitation
WP 1 – Open System Architecture Requirements
Interfacing Requirements System architecture Testing procedure
WP 2 – RT-System WP 3 – Simulation tool interface WP 6 – Advanced co-
Dissemination
Integration Methodology 1. Interface specification simulation interface (ACI)
tools
2. Prototype implementations (2015-2017)
MBSE for RT-System 3. Initial test and evaluation Framework for coupling
integration strategies
WP 4 – RT-System interface
Co-simulation system 1. Interface specification Specification for the Standardization
configuration 2. Prototype implementations overall ACI actions
3. Initial test and evaluation (2017-2019)
Tool-chain integration Commonly used
communication
WP 5 – Communication protocol media
1. Abstraction of bus system Exploitation
2. Prototype implementations plans and
ACI measures
3. Initial test and evaluation
(2016-2018)
WP 6 – Application Use-Cases and Assessment
Industrial applications
Scientific applications
16.10.2014 / Benedikt ACOSAR - HR/FRA Consortium © VIRTUAL VEHICLE 2
Fig. 2. ACOSAR Project Structure.
an investigation of means for system configuration and tool chain integration is
the next step. These results are consolidated in D2.1: Handbook on RT-system
integration methodology, which is jointly developed with WPs 3-5. WP 3 will
deliver D3.1: Specification of simulation tool interface, which aims at continuous
and discrete simulation as well as real time constraints for co-simulation. The
main output of WP 4 is D4.1: Specification of RT-system interface. It targets
real-time-systems and includes related possible test specifications. WP 5’s main
deliverable D5.1: Specification of communication architecture and communica-
tion protocol acts as a connector between WPs 2,3 and 4, from a communica-
tions point of view. The first version of the ACI specification, application guide
and test suite will be published in the project’s core deliverables D6.1, D6.2, and
D6.3.
Dissemination and exploitation plans are made in context of WP 8’s D8.2
and D8.3, respectively. The executive board (project and WP leaders) deter-
mines strategies to ensure the quality of deliverables, review and assessment
criteria, as well as effective risk management throughout the project. This will
be documented in D9.1: Quality assurance and risk management plan.
4.3 Use Cases and Assessment
The ACOSAR partners contribute a total of 9 use cases to the project. On one
hand, they are used as a starting point for the requirements engineering process.
On the other hand, they help to assess the effectiveness of the ACI and analyze
the impact of related process modifications. Due to the large number of use
cases and their high variability within their configurations, a summary is given
as follows. Popular scenarios include the coupling of offline simulation platforms
with online real-time systems. Typical examples for real-time-systems are test
beds for engines or vehicle brake dynamometers. Related to that, the exchange
of single simulation models or software components with their real-time-system
counterparts is a beneficial approach for X-in-the-loop testing. In this context,
electronic control units (ECU) or virtual ECUs (vECU) are candidate platforms.
One use case also includes a driving simulator for human interaction evaluation.
Different analyses were conducted on these use cases. Elicited technical chal-
lenges include e.g. the exchange of simulation data between offline and online
simulation systems, or the integration of multiple ACI interfaces per device or
platform.
4.4 Requirement Engineering for ACI Specification
In WP 1 requirements for the ACI are collected and managed as they serve as
a basis for subsequent work packages. In order to capture requirements of the
entire project in a structured way, a project specific requirements engineering
process has been created. It contains the artifacts shown in Figure 3.
Project goals Use Cases
n n
m m
Core n m
ICT methods
requirements
Project Level n 1
WP Level m n
Technical n m Technical
requirements scenarios
Fig. 3. ACOSAR requirement process artifacts
Project Goals represent the main objectives that are described in the project
proposal. Together with ACOSAR’s industrial Use Cases they build the basis
for the specification of ACI requirements. Use Cases (from WP 7) describe RT
co-simulation scenarios for which ACOSAR partners want to achieve a solution.
They are going to be demonstrated at the end of the project.
ICT methods describe functions of co-simulation scenarios on an abstract
level of detail and mainly from a user’s point of view. The methods should on the
one hand help to get a common understanding about the ACI functions within
the project team and on the other hand be a basis for writing requirements
and Technical scenarios. After the definition of ICT methods, partner related
Use Cases are described in more detail by specifying Technical scenarios, which
represent detailed activities of the co-simulation scenario of the Use Case. Table 2
shows the used template for specification of Technical scenarios, next to an
example specification. As Technical scenarios are based on the abstract scenario
from the ICT method, the template contains (in addition to the concrete Use
Case) specific steps of the abstract scenario for traceability reasons.
ID UseCase3_SysInt03
Method name Define timing requirements
Rationale Define timing requirements for integration of RT systems
Goal Define RT requirements for coupling signals
Preconditions Co-simulation units and coupling signals are defined
Postconditions Timing requirements are defined
Abstract scenario 1. Define communication step size per coupling signal
2. Define tolerable violation of timing requirements
3. Define timing constraints
Notes
Technical scenario 1a. Coupling signal speed: 10 ms sample time
1b. Coupling signal control action: 10 ms sample time
2a. Coupling signal speed: 10 ms delay tolerable
2b. Coupling signal control action: no delay tolerable
3a. Controller model executes 10 times faster than wall-clock-
time
Table 2. Technical scenario
Based on ICT methods and Technical scenarios, the Core and Technical re-
quirements are derived. Core requirements are project requirements for the ACI
and represent the main functionality. They are derived from Project goals and
ICT methods. In contrast to Core requirements, Technical requirements are work
package related and represent a detailed, technical specification.
For writing requirements, EARS boilerplates [11] are used. The predefined
syntax of boilerplate based requirements helps writing good quality requirements
(uniform and comprehensible). The requirements serve as basis for future refer-
ence implementations as well as for the ACI specification.
5 Exploitation & Innovation
The major innovations of ACOSAR will influence different economic, industrial
and scientific areas. Three potential fields of innovation can be identified.
1. ACOSAR features technological innovations by advancing solutions for inter-
operability problems. The considered communication architecture is based
on the ACI and allows the implementation of end user key knowledge. The
technological break-through results from dramatically shortened setup time
for verification and validation activities within the generic V-diagram.
2. ACOSAR enhances the overall product development process. By using the
ACI, the integration of real-time systems relies on information gathered ear-
lier during system design and specification phases as well as during the sys-
tem simulation phase. Therefore, a beneficial transfer of knowledge is intro-
duced into the development process.
3. Using ACIs functional framework, users are able to implement smart func-
tionalities in their real-time applications. For instance, crucial problems like
communication latency of cyber-physical systems (CPS) can be addressed
efficiently. This facilitates robust and accurate system development in a spa-
tial and temporal distributed development environment.
6 Outlook
In this paper we presented the ACOSAR project. Its primary goal is the develop-
ment of the advanced co-simulation interface (ACI). Progress towards this high
aim is already made, and the most significant results including the described
materials will be available to the public in Summer 2018.
References
1. Andersson, A., Fritzson, P.: Models for Distributed Real-Time Simulation in a Ve-
hicle Co-Simulator Setup. 5th International Workshop on Equation-Based Object-
Oriented Modeling Languages and Tools pp. 131–139 (2013), http://www.ep.liu.
se/ecp/084/016/ecp13084016.pdf
2. Benedikt, M., Hofer, A.: Guidelines for the Application of a Coupling Method
for Non-iterative Co-simulation. 2013 8th EUROSIM Congress on Modelling and
Simulation pp. 244–249 (2013), http://ieeexplore.ieee.org/lpdocs/epic03/
wrapper.htm?arnumber=7004951
3. Broman, D., Greenberg, L., Lee, E.A., Masin, M., Tripakis, S., Wetter, M.: Re-
quirements for hybrid cosimulation standards. Proceedings of the 18th Interna-
tional Conference on Hybrid Systems Computation and Control - HSCC ’15 pp.
179–188 (2015), http://dl.acm.org/citation.cfm?doid=2728606.2728629
4. Brückner, Swynnerton: Busbasiertes Architekturkonzept für Hardware-in-the-
Loop-Prüfstände. ATZ elektronik pp. 52–56 (04 2014)
5. Faure, C., Ben Gaid, M., Pernet, N., Fremovici, M., Font, G., Corde, G.: Meth-
ods for real-time simulation of Cyber-Physical Systems: application to automotive
domain. IWCMC 2011 - 7th International Wireless Communications and Mobile
Computing Conference pp. 1105–1110 (2011)
6. Functional Mock-up Interface for Model Exchange and Co-Simulation, Version 2.0
(2014)
7. Friedrich, M.: Parallel Co-Simulation for Mechatronic Systems. Ph.D. thesis, Tech-
nische Universität München (2012)
8. Galtier, V., Plessis, G., Renardi, L.: FMI-Based Distributed Multi-Simulation with
DACCOSIM. Spring Simulation Multi-Conference pp. 804–811 (2015)
9. Geimer, M., Krüger, T., Linsel, P.: Co-Simulation: gekoppelte Simulation oder
Simulatorkopplung. O+P Zeitschrift für Fluidtechnik pp. 4–8 (2006)
10. Hommel, M.: Parallelisierte Simulationsprozesse für virtuelles Prototyping in der
Automobilindustrie. Ph.D. thesis, Technische Universität Braunschweig (2006)
11. Mavin, A., Wilkinson, P.: Big Ears (The Return of "Easy Approach to Require-
ments Engineering"). In: Proceedings of the 18nd IEEE International Requirements
Engineering Conference. pp. 277–282 (2010)
12. Völker, L.: Untersuchung des Kommunikationsintervalls bei der gekoppelten Simu-
lation. Karlsruher Institut für Technologie (KIT), KIT Scientific Publishing (2010)