Tech Briefs Magazine - December 2023 - MD-7

ments. Remote valve terminals are used
to shorten pneumatic tubing and reduce
the number of bends, both of which increase
the performance of pneumatic
actuators by shortening cycle times and
reducing the likelihood of leaks.
Remote I/O modules and valve terminals
connect
to the PLC via the
industrial Ethernet network. Common
industrial protocols are EtherNet/IP,
PROFINET, EtherCAT, and Modbus
TCP. Industrial Ethernet networks reduce
the number of hard-wired connections
in the control cabinet, increase
the amount of diagnostic information
that can be acquired from the machine,
and pave the way for predictive maintenance
programs.
The approach of connecting fieldlevel
sensors and actuators to the PLC
via remote I/O modules and remote
valve terminals on the industrial
Ethernet network is well-adopted in industry,
but some challenges remain.
Challenges with the Existing
Approach
Manufacturers of remote I/O modules
and valve terminals provide software
tools to machine builders to ease
integration efforts. These software tools
include electronic data sheets and device
libraries, sample code and function
blocks, and configuration tools. At the
beginning of the integration process,
these software tools must be downloaded
and installed, then the user interfaces
must be learned. These steps take time
and effort on the part of the machine
builder or controls engineer.
Additionally, it is common to use remote
I/O modules and valve terminals
from different manufacturers. This compounds
the problem because each manufacturer
supplies a different set of configuration
tools, tailored to the functionality
of their devices. Controls engineers
are tasked with repeating the download,
install, learn, and configure steps of this
process for each manufacturer's devices.
Every remote I/O module and valve
terminal that connects directly to the industrial
Ethernet network requires a
unique network address. Each network
address in a machine incurs costs for the
machine builder in two ways. First, the
network hardware itself, essentially a twoport
Ethernet switch in every module and
terminal, has a cost to it that is hidden
inside the purchase cost of the compoMotion
Design, December 2023
nent. Second, small and medium-size
PLCs that are otherwise sufficient to manage
the full machine control often come
with a limited number of available network
addresses.
As machine builders look to increase
the benefits of digitalization by increasing
the number of devices that connect
directly to the Ethernet network, they
frequently must upgrade PLCs to more
expensive versions with a greater number
of available addresses.
An Improved Approach to System
Design
By reducing the number of integration
tools and network addresses needed to
build decentralized I/O and pneumatic
valve systems, machine builders can overcome
these remaining challenges. An
effective method to do this is to introduce
a dedicated bus interface into the
decentralized system architecture.
The bus interface acts as a gateway between
the industrial Ethernet network
and the remote I/O modules and valve
terminals. The bus interface connects directly
to the industrial Ethernet network.
The remote I/O modules and valve terminals
connect to the bus interface. The
connection of the modules and terminals
to the bus interface can be through a
physical backplane or over shielded,
high-quality cables. In both cases the
communications that pass between the
modules, terminals, and bus interface are
A remote valve terminal with on-board I/O is ready to connect to the industrial Ethernet network via a network
connection at the left side of the terminal. Remote terminals with IP65/IP67 ratings can be mounted anywhere
on the machine, which increases performance and flexibility for the machine builder. (Image: Festo Corporation)
PLC or machine controller
Remote I/O modules
Pneumatic valve terminals
Industrial
Ethernet
network:
Proximity sensors
Inductive sensors
Stack lights
Pneumatic cylinders, position sensors
Linear motion control
Rotary motion control
Typical layout of automation components in a machine, using a conventional approach to remote I/O modules
and valve terminals. Each module and terminal connect directly to the industrial Ethernet network, which requires
six points of integration into the PLC program and six available network addresses. (Image: Festo Corporation)
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Tech Briefs Magazine - December 2023

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