4/25/2008 | 7 MINUTE READ

What's Driving Factory Control?

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Smaller controllers, industrial controllers with built-in HMI, more powerful industrial computers, and Ethernet, Ethernet, Ethernet-these are the latest developments driving factory control.


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For today's factory controllers, small is beautiful, and most likely powerful and graphic, too. Both programmable logic controllers (PLC) and industrial computers now come in small sizes packed with features, from standard building blocks with low I/O count that can easily be expanded, to a variety of human/machine interfaces (HMI; i.e., displays) for entering and reviewing control programs and for monitoring operations, to a plethora of data communications links. One of those links is Ethernet, nowadays typically wireless Ethernet.


More microPLCs

Generally, the smaller the controller or computer, the fewer components inside, the smaller its power requirements, and the smaller the amount of heat it generates. And the devices are getting smaller. Take the CP1L Series, for example, from Omron Industrial Automation (Schaumburg, IL; www.omron247.com). These microPLCs have 14, 20, 30, or 40 I/O built-in (expandable to 160 I/O). The CP1L operates at 0.55 microseconds/LD instruction and 4.1 microseconds/MOV instruction. All models support positioning and motion control with four high-speed encoder inputs for counters that use two-axis differential phase control or four-axes single-phase control, and two high-speed pulse outputs for two-axis control. Measuring 4.3 x 5.9 x 3.3 in. (H x W x D), the CP1Ls go for $294 to $518, depending on options.

Want a physically smaller microPLC? Measuring 2.8 by 3.5 by 2.8 in. (W x H x D), the Durus microPLCs from GE Fanuc Intelligent Platforms (Charlottesville, VA; www.gefanuc.com) are for simple applications requiring less than 44 I/O. The controller can output 8 amps per point (2 amps inductance) and includes up to 15 timers. Execution speed is 10 milliseconds per cycle. Communications options include Profibus DP Slave, DeviceNet Slave, Modbus RTU Slave, and Ethernet Server. The controller comes with built-in backlit LCD and keypad. Besides showing controller status, the display lets people program the controller in situ. (It can also be programmed through an external unit.) Available programming languages are ladder logic and function block diagram. It can hold up to 200 lines (4 cells wide per rung) or 99 function blocks. 

This brings up an interesting point: On-machine/on-controller displays are sprouting everywhere on the factory floor. Why? Displays are affordable, the processors to generate the graphics are affordable and readily available, and the displayed information invaluable. Color displays, say officials at Israeli-based Unitronics (www.unitronics.com; sold through Integrated Drives & Controls in Ann Arbor, MI), enable machine and production line builders "to show more details on the operator panels, to display vivid, attention-grabbing alarms, and, in general, to brighten up their systems." Case in point: The Unitronics Vision350 is a PLC with a 3.5-in., 256-color TFT touchscreen. The PLC has 1 MB of ladder logic memory, features scan times of 155 sec per 1K of typical application, and offers up to 38 onboard digital and analog I/Os (expandable to 166 I/O). It features Ethernet connection via TCP/IP, GSM/SMS/GPRS, Modbus, CANopen and UniCAN. The HMI has 3.5 MB dedicated to storing and displaying images and fonts.


More industrial computers

The design strategy for industrial computers has mostly been to slap in the fastest, preferably coolest-running, central processor possible. Here's some background regarding processors, specifically multi-core processors (MCPs), which have run consumer desktop computers for a few years now. Lately, they've been appearing in industrial computers. This is good news; MCPs probably offer more benefits to the factory floor than to home or office environments. First, MCPs are generally fast processors. Applications scream along quite nicely. Second, each core can run at a lower frequency than a conventional single-core processor. This uses less power, and generates less heat. Third, multiple cores more efficiently distribute power both within the CPU and to other devices controlled by the CPU. For instance, individual cores can be turned off when not in use. Last, multiple cores can be multitasked. Individual cores can be dedicated to simultaneously run different tasks, such as machine control and safety monitoring.

At one time, "industrial computers" seemed to be an oxymoron. Nowadays, some auto-mated systems require a ruggedized high-end workstation near the control system to perform control logic and to generate some sort of display based on the I/O. Other automated systems eschew the box, eschew rackmounts, and run from the entire computer seated into any available PCI slot within an existing controller cabinet.

The ePC-Series from Nematron (Ann Arbor, MI; www.nematron.com) is an example of the first case. This unit combines industrial PC control with HMI-in a very thin box: mounted depth is less than 3 in. The low-end model comes with an Intel Celeron 1.86-GHz processor; the high-end, an Intel Core Duo 2.0-GHz processor and 2-GB system memory. These industrial PCs currently come in three LCD sizes: 15-in. XGA, 17-in. SXGA, and 19-in. SXGA. (A 5-wire analog resistive touchscreen is available.) All include a CompactFlash socket and extensive I/O, thereby eliminating bulky expansion slots and unreliable rotating CD-ROMs and floppies. The SATA hard drive can be removed without fiddling around with cable connections. For ports, each controller includes dual gigabit (10/100/1000), RS-422/485, PS/2, two RS-232, four USB 2.0, and video.

The newest single board computer (SBC) from MEN Micro Inc. (Sellersville, PA; www.men.de/default.asp?lang=1) exemplifies the other packaging approach for an industrial computer. The F18 is a 64-bit CompactPCI/cPCI Express SBC based on the latest multi-core Intel Core2 Duo architecture: the T7500 processor, which runs at 2.2 GHz and has 4-MB L2 cache, and the Mobile Intel 965GM Express chipset, which provides up to 500 MHz 256-bit graphics core. Add to that 4-GB soldered system memory. Digital image processing basically rivals any video game, whether the output is 2D/3D modeling, video and rendering (such as for vision and monitoring applications), scientific data and quality control processing, or just plain, but incredibly detailed and vivid mimic boards. The F18 supports Microsoft Windows (including Vista) and Linux operating systems, as well as the real-time operating systems QNX from QNX Software Systems and VxWorks from Wind River Systems. Prices start at $3,719.


Pervasive Ethernet

Then there's industrial Ethernet-wired and wireless. Rockwell Automation (Milwaukee, WI; www.ab.com/networks/architectures.html) has introduced a variety of industrial Ethernet switches and media integrated with technology from Cisco Systems (San Jose, CA; www.cisco.com). This co-branded line of managed switches extends Ethernet from the factory floor right up to enterprise-wide IT. Cisco Catalyst switch architecture provides time synchronization, prioritization, fault-tolerant ring networking, heavy-duty security (such as snooping and cut-through), and other high-performance networking capabilities. The switches can be configured using Allen-Bradley RSLogix 5000 programming software, and they automatically generate Logix tags for integrated diagnostics. The switches range from six to 26 ports (copper or fiber).

Many of these same ring, diagnostic, and security capabilities are also in a new Rockwell standalone three-port Ethernet module. This module lets single-port Ethernet devices to participate in linear and ring topologies. There are also Rockwell managed switches with four or eight copper ports (an optional fiber uplink exists for higher-level networks). Last, Rockwell has a new line of unmanaged industrial Ethernet switches. These don't require configuring. All together, Rockwell now supplies just about any type of Ethernet infrastructure: managed or unmanaged, modular or fixed, mesh or ring, embedded or separate.

Cisco, which is not usually associated with factory control, has its Industrial Ethernet 3000 Series Switches. These are ruggedized, easy-to-use, highly secure switches that support up to 150 different port configurations for both copper and fiber Ethernet deployments. These switches have security features such as access control, authentication support, and multilevel password protection.

Wireless factory-floor communications are now possible, despite the radio frequency interference so common there from the multitude of electrical equipment. As in consumer environments, wireless technology does away with punching through walls to run cable and to install connectors/terminators, thereby saving costs in interfaces, cabling, and associated installation time and labor. In industrial applications, wireless solves the problems related to physical distance and I/O requirements of individual and unique machines, controllers, and peripheral devices. As officials at GE Fanuc point out, "Wireless can support multiple users connected to multiple applications via multiple protocols on the same unit or the same network-simultaneously."

In October, GE Fanuc introduced TranSphere Wireless communications for industrial automation (www.gefanuc.com/as_en/products_solutions/controllers_io/transphere_wireless.html). These products support 2.4-GHz and 900-MHz frequencies, and include extended-range IP networking, wireless IP/Ethernet connectivity, and Ethernet and serial communications radio modems. The products support multiple layers of protection, including 128-bit data encryption, two-way authentication, and dynamic key rotation. The typical range for the low-end transceiver (TS 15; at least two are required) is 6 miles fixed or 1 mile mobile and moving. Data rates are 106 kilobaud. Another product, the TranSphere TS Wireless I/O module, integrates on-board analog and discrete I/O with wireless. These stackable modules use standard serial and Ethernet/IP protocols or regenerate I/O signals between PLCs, remote terminal units, and other control/monitoring devices. The TS I/O modules support Modbus Serial, Modbus TCP, DNP.3 serial/Ethernet, and DF1. The modules also have WeXP, a wireless connection based on 802.15.4, which lets expansion modules be located up to 2,500 feet from a base module.

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