May
18, 1998 Design News
AUTOMATION
Software spurs automation optimization
Simplified interfaces are
key to system design versatility
by Ryan McDonald,
BridgeVIEW Product Specialist,
National Instruments, Austin, TX
Robotics are taking the automation of manufacturing
lines to new levels in industries ranging from automotive
to electronics, consumer goods, and telecommunications.
While the "human-less" factory does not yet
exist in the literal sense, more and more products are
built without manual labor.
While such systems have the potential to deliver tremendous
cost and quality benefits, there must be provisions
to continually monitor the behavior of the robots to
ensure their performance. Just as the concept of division
of labor was used to increase efficiency of manual assembly,
this same principle holds for robotics systems. A typical
manufacturing line may consist of several individual
components--specific stations handling isolated, specialized
tasks, including parts handling, pick-and-place, and
assembly.
In theory, robotics systems are implemented to increase
efficiency and throughput of processes. Robots, unlike
humans, require no sleep, so they will work incessantly,
24 hours a day, 7 days a week. And robotics systems
are experts at handling the same task again and again--repeatability
resulting in increased consistency and higher quality
end products. Finally, robots move faster than humans,
thereby increasing the speed of the assembly application.
To ensure these potential benefits of robotics are
realized, data must be continuously acquired from a
robotics system and analyzed for problems, as well as
for new ways to improve the line efficiency. While some
robotics systems continue to have proprietary interfaces,
trends in the industry today include the use of standard
programmable logic controllers (PLCs) with published
interfaces, direct interfaces such as Dynamic Data Exchange
(DDE), or, more recently, Object Linking and Embedding
(OLE) for Process Control (OPC) (see sidebar).
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Before OPC, would automation software and
hardware play together across individual interfaces?
Now OPC servers? standard interfaces permit
automation software packages with OPC capabilities
to communicate with any hardware. Thus developers
can concentrate on product features, not proprietary
device drivers.
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Line up! A leading cellular phone
manufacturer is implementing such an OPC system. Mike
Gorbutt, software developer for Applied Technical Solutions
(Dallas, TX), is developing the automation software
to monitor and control the cellular-phone manufacturing
lines. The two lines now in operation use Sony Factory
Automation (San Diego, CA) robotics controlled by Omron
(Schaumburg, IL) PLCs. National Instruments off-the-shelf
BridgeVIEW software communicates with the PLCs to acquire
error information and analyze station downtime.
"The name of the game is throughput," says
Gorbutt,which directly impacts the bottom line. "Keeping
track of the number of failures for particular stations
can be misleading, because some problems take more time
to solve. Thus, we keep track of not only the number
of faults for each station but also the amount of error
time," he notes. Thus the manufacturer can identify
which stations are having problems, and schedule operations
to re-train the robots.
Data gathering helps not only to analyze problems but
also in understanding the effectiveness of system changes.
Gorbutt explains, "When the technical support personnel
make changes to a station, they need to know if these
changes are successful. With this application, they
can easily compare what has happened on the line during
the previous minutes or hour, and compare that to events
at an earlier time or shift."
Later this year two additional lines will be installed.
These will use Rockwell Automation/Allen-Bradley (Bloomington,
MN) PLCs. By simply changing the communication from
one PLC interface to another, the software architecture
allows the manufacturer to use the same application.
Currently, Gorbutt is gathering historical line information
to improve the system and prepare for the next phase.
Into the new century. Trends in robotics
today, including the move toward distributed intelligence,
allow each part of the system to operate in its responsible
area and have knowledge of necessary information via
communications structures, such as Ethernet, DeviceNet,
or 1394. When combined with progress in automation toward
PC-centric solutions, future robotics systems will see
PCs building control and trajectory information and
then orchestrating, prioritizing, and distributing these
high-level instructions to the distributed intelligence.
Finally, the increased presence of open interfaces ultimately
will allow the most efficient combinations of automation
software, controllers, and robotics hardware.
OPC--the connection standard
OPC (Object Linking and Embedding (OLE) for Process
Control) is having a major impact on automation systems
today. The OPC Foundation, chartered with developing
the standard, consists of more than 150 companies committed
to developing a mechanism that allows different software
pieces to communicate with one another. OPC establishes
an open industry standard for plug-and-play interoperability
between disparate automation devices, systems, and software.
Built on Microsoft ActiveX, OLE Automation, and distributed
component object model technology (DCOM), OPC servers
and clients exchange real-time information between a
variety of systems including distributed control systems
(DCS), programmable logic controllers (PLCs), distributed
I/O systems, and smart field networks. This results
in OPC removing barriers between traditionally proprietary
manufacturing systems, easing integration of corporate-wide
automation and business systems.
Via the OPC interfaces, information is brought from
the robotics system to automation software for monitoring,
supervisory control, and statistical-process control.
The raw data or filtered results are then sent to the
enterprise business systems to record manufacturing
data for quality improvements and ISO-9000 compliance.
Before OPC, software vendors spent enormous efforts
to develop protocol drivers in order to communicate
with the vast array of hardware options available. This
not only resulted in software companies often duplicating
one another's work, but customers had to be concerned
about whether their preferred automation-software package
could communicate with their preferred type of hardware
(see figure). With the advent of OPC, automation software
packages having OPC client capabilities can communicate
with any OPC server software through a standard interface.
The result: customers can select both preferred software
and hardware with confidence that the two will communicate.
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