wilamowski-b-m-irwin-j-d-industrial-communication-systems-2011

15-6 Industrial Communication Systems
The proxy functionality enables the representation of the field device (FD) application data in context
of the object model used in the VAN domain. This mechanism also allows all relevant devices’ data of a
certain physical device without VAN capabilities to be represented as a VAN-VD. This device is visible
within the VAN domain, although it has not been connected to the VAN directly.
It can be seen that the VAN-AD and the VAN-PD offer an integration path to combine different
communication technologies in a given automation application, thus to handle the heterogeneity of
participating communication networks.
15.2.3 VAN System Architecture
The properties of a VAN can be represented by a block scheme (Figure 15.5). Blocks are logical components
offering specific VAN functionality.
Single devices do not offer all possible properties, since they are context specific. Thus, only the necessary
blocks have to be allocated to a VAN device, depending on the device type and communication profile.
To classify the block functions, one can distinguish
• Used standards (communication technologies, Internet protocol suite, adopted safety, security,
and time synchronization standards)
• VAN-specific functions; the configuration of these functions is stored in application service elements
(ASEs)
Since the object-oriented ASEs contain the data for the VAN functionality, they are crucial components
of the VAN system architecture. All attributes of an ASE can be accessed via Web services by
uniformly defined Get and Set services. The access rights are defined in the access control list (ACL).
VAN system
management
app. proc.
VAN
security
AP 1-n
VAN
PnP
AP
Param.
Config.
Web
application
Web server
VAN runtime
object
dispatcher
VAN autom.
app. proc. 1-n
Runtime
object model
VAN safety
app. proc.
Safety layer
Runtime
object model
VAN routing
IP address
mapping
Routing
Address
mapping
Runtime
object model
VAN
proxy
app. proc.
VD
object mode
VAN device- and
network management
VAN
MIB
VAN
runtime
object
tunnel
Native
Tunnel
VAN common communication
Application service elements (ASEs)
Internet protocolsuite
Web services over virtual
automation networks
Access control list (ACL)
VAN heterogeneous network technologies adaptation layer
VAN network technology layer
Security
Time
sync.
To access points, automation- or proxy devices (AP, AD, PD)
Technology
standards
VAN specific services communication
VAN communication stack
PROFIBUS
INTERBUS
AS-Interface,
ZigBee.......
To Virtual Devices
(VD)
FIGURE 15.5 VAN system architecture (AP, application process; MIB, management information base). (From
Specification of the Open Platform for Automation Infrastructure, Deliverable D02.2-2: VAN Open Platform API-
Specification, European Integrated Project VAN FP6/2004/IST/NMP/2-016969 VAN Virtual Automation Networks,
2006. With permission.)
© 2011 by Taylor and Francis Group, LLC