An open and shut case for the benefits of Web-accessible plant operations
At a recent automation show in Paris, France, manufacturing engineers crowded around a computer screen that was remotely diagnosing faults in a servo drive. Using a standard Web browser, the engineers jogged the axis, ran profiles, and watched the movement of the drive 300 miles away in Sophia, France, over live Web camera feed. When a random fault occurred, the demonstrators easily diagnosed a broken feedback connection on the motor.
The most impressive part of the experience, however, was realizing that the entire process was accomplished using proven, readily available commercial technology that allows components from different manufacturers to be mixed and matched freely, easily, and inexpensively. The technology demonstration won awards in the Business Solutions and the Integration and Comprehensive Solutions categories at the Automation Europe show.
The system features programmable logic controllers (PLCs) with embedded Web servers that enable users to work with information in graphic form, as well as servo drives communicating with controllers over a SERCOS-compliant (Serial Realtime Communication System) fiber-optic link.
The backbone of the entire system is a TCP/IP-enabled Ethernet—rather than a proprietary—network, which makes it possible to share factory floor information throughout the enterprise over an Intranet and around the world over the Internet.
The result is a "transparent factory" that allows anyone with proper security clearance and network access to pull information from the PLC, display it on custom Web pages and change the parameters from anywhere in the world.
Using a servo drive with integrated SERCOS support, diagnostic data from the amplifier is combined with the diagnostic data from the PLC-based motion control and displayed on a Web page as graphical elements. Drive and motion parameters and even the PLC program itself can be modified—and the system retested—over the Internet without ever leaving the browser environment.
That’s a marked departure from traditional proprietary plant networks (Interbus, Profibus, ControlNet, etc.), which provide a heavily customized, one-way architecture that collects production and diagnostic data, interprets it, and displays it on a Web server.
These types of systems provide users with no means to react to the data and send back commands that are then automatically implemented. The prevalence of such one-way systems has, in fact, inhibited the deployment of more open Internet technology in manufacturing.
Truly open, Ethernet-based systems that employ innovative uses of open servos, SERCOS, and the ability to embed a Web site directly into a PLC module could trigger two major directional changes for the industry: users will have the ability to remotely access machine control and diagnostic functions; and users will be able to use their existing PCs and laptops as operator interfaces, reducing the number of interfaces required on the factory floor.
Many users can use this new open system technology to help eliminate unscheduled equipment downtime. For example, if a user can remotely monitor increases in amplifier current draw, commonly caused by overheated bearings, the user can predetermine bearing failure. By significantly reducing downtime, users could potentially add tremendous value to their equipment without any significant incremental investment.
The web-enabled modules could allow users to remotely access all of their machinery and modify production parameters. Any authorized network subscriber could adjust machine throughput to meet raw material constraints or make modifications to manufactured product based on orders. This ability to customize production enables the end user to minimize raw material and inventories of finished goods.
Maintenance staff who have access to remote start-up support can upload their PLCs with pertinent information such as technical drawings, electrical specifications and other vital information to ensure smooth operation with maximum production. OEMs could minimize their on site start-up personnel after machine installation, and control engineers could spend more time at the OEM facility, adding value to future designs.
Machine operators can use the system to display statistical summaries. Any network subscriber could customize a Web page within the PLC platform to display production data in a manner that is meaningful to that user. Because the data is displayed graphically, an end user could make modifications with any standard Web browser without requiring a great deal of specialized training.
Today any complex machine requires its own stand-alone human-machine interface (HMI) so that operators can make changes, monitor processes and input or extract key information. With a web-enabled module, users can turn any computer or laptop into a HMI. Authorized personnel can dial up the PLC’s Web address and access real-time machine data and/or change machine parameters using a standard Web browser. Operator screens designed with a standard HTML editor or by adding Java applets from within the browser can translate data into usable information and allow operators to manipulate virtual knobs and dials just as they would manipulate the real things. By taking advantage of Internet browser technology, anyone with proper clearance can access and read the information in a PLC without special proprietary knowledge — and they can then issue instructions to change the PLC-controlled processes. Users get the advantages of a PLC with the user-friendly graphic interfaces of a Web browser.
Remote motor diagnostics will become possible when web-enabled PLC motion modules and servo amplifiers are both SERCOS-rated. These systems should feature a fibre optic ring which takes full control of amplifier and motors. When the PLC address is dialed up, the user can access the motion module remotely and poll the amplifier.
This approach, which Schneider Electric is calling the "Transparent Factory," is made possible by segmenting Ethernet networks to eliminate the speed and determinism issues of the past. Intelligent bridge and router technologies form a path to extract information while providing determinism and speeds of 100 MB, 1 GB, and even faster speeds in some applications. Because Ethernet is the backbone of choice for many business applications, transporting data between applications and systems is no longer an expensive and error-prone task. Using proven commercial technologies and international standard protocols such as SERCOS, Transparent Factory takes advantage of off-the-shelf items such as Ethernet cards, hubs, routers, and Web browsers, thereby lowering the costs associated with training, support, and infrastructure procurement. The open architecture also allows a factory’s automation environment to evolve with technology.
With this approach, the factory floor is no longer a remote, desolate island of proprietary networks that can communicate with the business world only through expensive, customized hardware and software. Instead, automation equipment is a natural extension of the massive world network that links virtually every other business system. And the availability of open, SERCOS-based servo systems extends the reach of those systems all the way down to individual drives. The combination of Ethernet-based Internet access and SERCOS-accessible drives on the factory floor could forever change the industrial automation landscape.
Angelo Sanfilippo is a Motion Specialist at Schneider Electric.
You can reach him at firstname.lastname@example.org.
(A version of this article first appeared in the July 2000 issue of Motion Control magazine.)