Written
by: Paul Wacker, ICOM Product Manager, Industrial
Automation Group, Advantech
With
the rapid advances in machine automation in the
past decade, and the continuing quest by industrial
OEM equipment suppliers and manufacturers to increase
throughput while simultaneously increasing resulting
product quality, machine vision continues to play
an important role in maximizing productivity, efficiency,
and most importantly quality. With the help of gigabit
Ethernet, levels of performance and flexibility
are being achieved, that were not possible as recently
as a few years ago.
For
those not familiar with the term Machine Vision,
it is the application of computer image processing
to industry and manufacturing. Overwhelmingly, it
is the preferred means for visual inspections that
require high-speed, high-magnification, repetitive
operation, and repeatability of measurements.
Traditionally,
these systems have been based on analog cameras
or commercial technologies not well adapted to the
needs of industrial systems. Such systems generally
consist of an analog camera connected to a special
PC-installed interface card (called a "frame
grabber") or a first generation digital camera
connected via CameraLink, USB or FireWire (IEEE
1394) interface. Often, special lighting is often
required, which generally consists of a strobe light,
triggered by an external photoelectric sensor.
While
acceptable for office, laboratory, and light industrial
environments, these technologies are not well suited
for industrial applications. First and foremost
is the distance limitation of 5m to 10m for analog
and first generation digital cameras. Such constraints
limit the use of machine vision to small systems,
or worse, they compromise the location of the PC,
putting it in a location that may cause premature
failure or that is difficult to service and maintain.
Finally, the use of proprietary interfaces and the
lack of standardization between component manufacturers
make it difficult if not impossible to select best
of breed components and successfully integrate them
into vision systems.
These
obstacles and the emergence of gigabit Ethernet
prompted a number of camera manufacturers to work
with the Automated Imaging Association to develop
the standard now known as Gig-E
Vision. This new standard allows extremely fast
image transfer, over relatively long distances,
using low cost standardized cables. It also allows
seamless operability between hardware and software
from different manufactures, with a more flexible
architecture, and the ability to scale with the
technological advancement of Ethernet.
All
of this is possible due to the continued advancement
of Ethernet technology, and its tremendous commercial
success. Standardized in June of 1998, gigabit Ethernet
offers similar characteristics to well known Fast
Ethernet (10/100Base-TX), but it is 10-times faster.
Initially deployed in local area network backbones
and server connectivity, the decreasing cost of
gigabit Ethernet, has significantly expanded its
use in recent years.
Gigabit
Ethernet has a maximum transmission speed of 1 Gbps
(or 1000 Mbps); using familiar RJ45 connectors attached
to inexpensive Cat6 (or Cat5e) unshielded twisted
pair cabling, capable of connections of up to 100m.
More importantly though, is the ability of gigabit
Ethernet to carry a larger data payload of 9000
bytes as compared to the 1500 bytes data payload
of previous generations of Ethernet. These "Jumbo
Frames" allow more efficient transmission of
large blocks of data, such as images, while reducing
processing overhead by attached cameras and PCs.
For
all but the simplest of applications, Gig-E Vision
systems require an Ethernet switch as a central
connection point for cameras and PCs. Industrial
Ethernet switches like the EKI-2725
provide a central connection point for PC-based
vision systems and Gig-E cameras.
Utilizing
gigabit Ethernet, distances between any two components
is at least 100m, a ten-fold improvement over previous
machine vision technologies. With a single Ethernet
switch placed between a Gig-E camera and a PC, distances
of 200m can be achieved. For longer distances, fiber
optic cabling may be employed, along with the appropriate
Ethernet switch or media converter.
A
more interesting result of the adoption of gigabit
Ethernet for Gig-E Vision is the introduction of
networking to machine vision systems. Connections
between PCs and cameras are no longer point-to-point
connections - they are networked. This means it
is possible to create systems consisting of multiple
cameras and multiple PCs. While the advantages of
connecting multiple cameras to a single PC, without
the need for multiple frame grabber cards is obvious,
Gig-E Vision allows video images from a single camera
to be simultaneously sent to multiple PC for distributed
image processing.
Like
many industrial technologies, Machine Vision spans
a wide range of market segments and applications.
Several of the market segments showing strong growth
for gigabit Ethernet include automated inspection
equipment, medical imaging, intelligent traffic
systems, optical character recognition, and public
security systems. All of these segments share a
need for fast acquisition of high resolution images
that are processed by PC-based systems.
As
an illustration of the capabilities of Gig-E Vision
system capabilities, consider its use for automated
inspection of product on high-speed beverage bottling
line. To ensure quality and safety of the finished
product, each bottle must be inspected to ensure
product level, proper label application, and secure
bottle cap installation. Operating as speeds of
hundreds of bottles per minute, this is an obvious
Gig-E vision application.
The
use of Gigabit Ethernet and an industrial Ethernet
switch allows multiple cameras to be connected to
a single PC-based vision processing system. Since
food and beverage equipment needs periodic sanitary
wash down, Ethernet (with allowable distances up
to 100m) allows the cameras to be placed in optimum
locations, with the PC located where it can be best
protected from caustic solutions and machine vibration.
Connected
by Gigabit industrial Ethernet switches like the
Advantech EKI-2725, Gig-E Vision compliant cameras
and PC-based vision processing software, provide
high speed image processing to OEM equipment suppliers
and manufacturers, with the flexibility, ease of
deployment, and cost-effectiveness required for
today's machine vision applications.
Preparing
for the Fiber Future
While copper UTP cabling will continue to dominate
Local Area Network systems in the near future, fiber
optic cabling is expected to become the predominant
cabling media for resistance electromagnetic noise
applications, long distance communications, and
high speed transmission needs.
According
to the Structured Cabling Systems Market, Fiber
cabling shipments will exceed copper UTP cabling
shipments beginning in 2008 (see below).
Advantech's
EKI switches not only provide Gigabit and fiber
optic ports, but also enable ultra fast network
recovery times to establish redundant Gigabit X-Ring
backbones and intelligent network management functions,
such as QoS, IGMP Snooping/GMRP, VLAN, Port Trunking,
SNMP V1/V2c/V3, IEEE 802.1X, and https/SSL, along
with advanced security features.
