Automated distribution systems speed material handling
United Sortation Solutions (USS) organized automation into a consolidated platform for material handling applications using embedded PCs, human machine interfaces, I/O modules, programming software, and industrial Ethernet networking in their machines to help customers to pick, pack, and ship goods more quickly. This is part of the Control Engineering March 2015 cover story.
United Sortation Solutions (USS) organized automation into a consolidated platform for material handling applications. Advancements in embedded PCs, human machine interfaces, I/O modules, programming software, and industrial Ethernet networking help companies that need to package and ship goods nearly in real time, fueled by a growing demand from online shopping. These demands placed on today's warehousing and distribution operations are intense. Vendors with online and brick-and-mortar storefronts of all sizes are under increasing pressure by customers to pick, pack, and ship goods more quickly. USS, based in Owings Mills, Md., provides highly automated distribution systems for retailers and warehouses. [This is part of the Control Engineering March 2015 cover story.]
The company's systems are designed to be flexible and compact for implementation in facilities with space-restricted layouts. The USS portfolio of material handling equipment has many standard offerings that can be customized to each application, including: vertical lifts, stackers/de-stackers, the advanced EuroSort bomb-bay flat sorters and, newly introduced at the MODEX 2014 trade show, the Sweeper Sorter. This system is focused on small- to medium‑sized distribution centers and can handle small items, such as health and beauty supplies, cell phones, eyeglasses, and contact lenses, rapidly sorting them into totes, cartons, or chutes.
Industrial Ethernet helps sorting
USS has more than a decade of experience developing advanced material handling technologies. However, the automation and control technologies incorporated by the company haven't always been synchronized with system designs. The company needed to restore balance to the automation technology it used for high-volume distribution applications—particularly in the areas of I/O and controller hardware.
"While our original control designs delivered the functionality and performance we needed, we had drifted into what we considered a hybridized I/O solution paired with stagnating traditional PLCs. The system was overcomplicated in its architecture and not as flexible as we needed," explained Jeff Zerr, director of engineering, USS. "A few years ago we kick-started a complete control-system overhaul with step one of the plans focused on replacing our remote I/O system."
To move its I/O technology forward, USS examined industrial Ethernet technologies. Eisenberg said USS determined that the EtherCAT Ethernet protocol "was even faster than what our requirements dictated; the microsecond-level performance is outstanding." With more than 65,000 possible EtherCAT devices in one system, the number of I/O points exceeds USS needs.
In addition to I/O installation practices, software programming for USS automation systems went under intense scrutiny. "We previously used numerous PLC programming environments and frequently switched platforms because no single software could do everything for us," Zerr explained. As we learned more about PC-based software, "we found that we could do all of our programming in one unified programming environment and build up libraries for our entire product line, from small timing machines up to giant sorters," Zerr said PC-based programming today is primarily done using Structured Text and Ladder Logic, and IT-oriented programming tools also are used. With standard Microsoft Visual Studio and Microsoft Windows OS in the mix, USS can use the PC-based control software "to put a wide range of IT tools to work without requiring complex, proprietary system add-ons."
With its Visual Studio integration, the PC-based control software 3 gives programmers a wide range of tools from IT/computer science disciplines such as C/C++ and .NET programming languages. "We have also begun implementing source code management and are building up comprehensive software libraries for all our solutions. Over time this will save us considerable programming and configuration time," Zerr added.
Control transform distribution systems
As USS moved to implement EtherCAT and PC-based control, the control hardware platform quickly took shape. Today, the control system architecture comprises embedded PCs that run the unified programming software and are connected to a compact "built-in" control panel with a compact 7-in. display. Machine operators can wear thin work gloves with the screens.
The I/O system is networked with EtherCAT, and related terminals and I/O modules and a safety I/O module to implement safety functionality. "EtherCAT ties everything together for USS," Eisenberg said. "It has become our all-purpose bus for all our machine lines, covering control, I/O, drives, and even safety."
USS integrates EtherCAT with a range of points per I/O terminal, including 16-channel terminals (digital input and output versions). The high-density terminals "work well by adding to installation flexibility and cabinet space-savings," Zerr explained. The 12-mm wide, erminals save a substantial amount of space compared to conventional methods of implementing 16 I/O channels. Also, depending on the amount of I/O required, we can easily switch to 2-, 4- or 8-channel EtherCAT terminals. Today, our I/O configurations are completely flexible, and our spare parts management has been simplified."
The IP67‑rated Ethernet modules are also distributed for the length of USS machines. These are installed directly on the equipment, outside of electrical cabinets, and are designed to capably resist dust and moisture in industrial environments. The modules have freely configurable digital inputs or outputs in one device for maximum flexibility. One has eight configurable channels, and another module has 16 configurable channels. Another module has four analog outputs that can be individually parameterized and generate signals either in the -10 to +10 V or the 0/4 to 20 mA range.
Beyond basic I/O functionality, EtherCAT-based safety grew into the USS system redesign. Replacing numerous hardwired relay circuits, the safety I/O solutions in IP20 and IP67 protection are used to implement functional safety in USS systems.
"Most of the sorters we manufacture are quite long and safety devices are installed down the length of the equipment, so distributed safety I/O pays off quickly," Zerr said. "Networked safety gives us excellent flexibility, for both personnel safety and machine safety. Today, we easily handle how the machine responds depending on which safety device is activated, whether from pull cords, e‑stops, safety gates, limit switches, or whisker switches, to detect if an unsafe state has occurred or is developing. As we add safety equipment today, we simply add more" of the safety I/O.
Since distribution and warehousing facilities are hives of human activity, a robust safety system is a must-have on USS machines. Cost for the safety implementation varies by the number of safety devices required on the line. With programmable safety and safety I/O, "the more safety points you have, the better for our customers," Eisenberg explained. "We did a rough analysis on smaller systems where the decision to use safety I/O may be more difficult to make and determined we actually don't need to implement many safety devices before networked safety is well worth it."
Many IP20 EtherCAT I/O terminals in USS control cabinets are connected to the embedded PCs, including the safety terminals, reducing cabling and coupler needs. Capable of handling all levels of automation required by USS products, the embedded PCs are in three configurations: 1.5 GHz Intel Core i7 dual-core CPU, a 1.1 GHz Intel Atom Z510 processor, and a 1 GHz ARM Cortex-A8 processor. All three embedded PCs have very low heat dissipation, reducing cooling requirements in electrical cabinets, and are designed to endure an extreme operating temperature range (between -25 and 60 C). Two can leverage a full Microsoft Windows OS environment, "which we sometimes need, depending on the application, for specific file management requirements and advanced Windows functionality," Zerr said. An embedded PC with Microsoft Windows CE embedded OS offers "surprisingly high performance with low hardware costs. We run all our PLC, HMI, and motion control tasks on these embedded PCs."
For the drive system, USS uses EtherCAT-enabled servo drives connected to servomotors with one cable. Single- and dual-channel drive versions are used by USS, providing the choice to connect one or two servomotors per drive. USS frequently implements electronic gearing in PC-based control to coordinate the servomotors, which simplifies the mechanical designs of equipment and lowers material costs.
Profitable equipment, faster commissioning
After thorough testing and a successful initial implementation, USS has standardized on a PC- and EtherCAT-based control platform. "Whether implementing a stacker, lift, or sorter of any size," Eisenberg said. "To affirm our decision, USS recently conducted a thorough side‑by‑side comparison with a conventional PLC alternative. By our own measure, system scan times are now 100 times faster" using the PC-based control platform.
Not limiting benefits to performance and speed, the EtherCAT network also dramatically reduced USS wiring requirements. "EtherCAT has made our systems much more competitive with easy expandability," Zerr stated, citing performance increases and hardware and labor cost reductions. "In some cases, we've reduced our overall control system cost by approximately 90% using PC-based control and EtherCAT technology," Zerr said.
The convergence of automation and IT technology with unified programming software and PC-based control hardware has delivered a similar range of benefits to USS. "As our code continues its maturation," Eisenberg said, "I expect we will measure new software projects in terms of weeks instead of months and machine startup tasks taking days instead of weeks."
"Consolidation of all our machine programming into one feature-filled software environment also represents a significant technological step forward for USS." Now USS' automation and I/O systems are far better organized and streamlined to match the advanced material handling processes the company has established with its customers.
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