Lean automation architectures

Technical advances lead to more efficient automation solutions.

11/25/2013


Figure 1: Traditional machine automation architecture has communications limitations. Courtesy: EatonFor decades, machine automation architecture has hardly changed. The basic makeup of control systems involved a programmable logic controller (PLC) with discrete and analog I/O running to the end devices, while an electronic operator interface (OI) provided an interface to set up, operate, and maintain the machine.

Technical advances in processing and communications are yielding new capabilities for machine automation. These communications advances are at both the device and enterprise level and are enabling a streamlined automation architecture (see Figure 1).

1) Device level networking enables direct connections to intelligent end devices on a machine and can remove I/O and wiring from the control cabinet. In addition to simpler construction, direct connection to smart devices improves diagnostics and helps to increase machine up time.

Figure 2: Streamlined machine automation: Communications advances are at the device and enterprise level and are enabling a streamlined automation architecture. Logic control, operator interface, device level communications, and enterprise level communica2) Enterprise level networking, with the emergence of industrial Ethernet technologies, enables machines to connect into the manufacturing enterprise. This can provide significant value in monitoring operational efficiency, notification and resolution of machine alarms, and remotely troubleshooting and upgrading the automation programs.

In addition to these operational advantages, these technology advances provide an opportunity to streamline the automation architecture into a simpler form shown in Figure 2 where the logic control, operator interface, device level communications, and enterprise level communications have been integrated into one automation component. 

For machine original equipment manufacturers (OEMs), advances in device and enterprise-level communications are enabling the combination of visualization and control, and a new level of connectivity. These changes are making it possible to design and build smarter machinery faster at a lower cost. These advantages can be achieved with:

  • An integrated development environment that allows faster machine design
  • Fewer components and wiring means reduced machine construction costs
  • Centralized remote access and administration, improving operation and reducing machine support costs.

Networks streamline automation

While somewhat overshadowed by advances in enterprise networking, device-level networks have continued to progress, enabling more cost-effective connection of even simple devices through a network to the logic control within the system. These advances have taken place both within the control cabinet and outside of it, to expand to the sensors and actuators mounted on the machine. The impact of moving from traditional I/O cards and wiring to simple device-level networking in a control cabinet can be seen in Figures 3 and 4.

Figure 3: Control cabinet before: Before industrial control networks or fieldbuses, control panel connections were hardwired using point-to-point wiring inside cabinets and home-run wiring to and from remote cabinets. Courtesy: EatonFigure 4: Control cabinet after: Device-level wiring systems use smart modules that connect standard motor control components via flat cable to a gateway module, which connects to a standard fieldbus on the PLC’s CPU. A device-level network like Eaton’s S

Device-level networks yield multiple advantages: reducing time to wire and commission the control panel, removing the I/O cards from the system, and improving operational diagnostic information for more reliable systems.

The move away from I/O to networking for connecting sensors, actuators, and human interface in machine control is a key enabler of a combined automation platform. Once the role of the I/O cards in a system is removed or significantly reduced, the value of having a separate PLC from the electronic operator interface (EOI) is also diminished. The processing power available in today’s microprocessors makes handling the operator interface task and the programmable logic control task manageable from one device. Further, as remote access is increasingly important, the case for a combined HMI-PLC is strengthened, changing the basic control system and enabling a leaner automation approach that combines logic, visualization, and connectivity.

HMI-PLC convergence

Figure 5: The historical complementary electronic operator interface (EOI) and programmable logic controller (PLC) relationship is shown. Courtesy: EatonThe manufacturing community stands to make significant productivity gains with the emergence of industrial Ethernet applied to the factory floor. The expanding capabilities of networks and the smart devices that can interface over it are driving improved diagnostics, faster troubleshooting, and overall improvements in machine reliability. With the information that Ethernet connectivity is enabling, there are more opportunities to reduce the time and costs involved in diagnosing and fixing issues before they cause downtime or delay commissioning. These changes also impact the automation systems on machines, demanding a fresh look at the automation architecture and the role of the PLC and HMI in that system.

To better understand the convergence of HMI-PLC functionality and equipment options, a historical perspective of the PLC and OI technology and development is useful. Traditionally, the PLC was developed to provide control, sequencing, and safety functionality for manufacturing processes, replacing systems that involved numerous devices—multiple control relays, timers and drum sequencers, and closed loop controllers. Largely, the I/O cards used to interface to the sensors, actuators, and simple operator interface devices such as push buttons and pilot lights made up the controller.

Figure 6: This diagram shows the emerging overlap of electronic operator interface (EOI) and programmable logic controller (PLC) features, as vendors of each vied to address new requirements for historical information, alarming, and security. Courtesy: EaThe electronic operator interface (EOI) was introduced to complement this simple PLC. By connecting to the PLC through a simple serial network connection, the EOI added the ability to present much richer information to the machine operator, replacing some of the simple push button and pilot lights in the process. This historical relationship between the EOI and PLC is shown in Figure 5.

With industrial Ethernet, the advent of remote access in the automation space means increased automation functionality including: historical data capture and exchange, alarm notification and management, and security administration. These features have been introduced into both the PLC and EOI and tend to overlap today, as vendors of both PLC and EOI equipment have vied to address new requirements for historical information, alarming, and security (see Figure 6).

More is not always better and redundancy in EOI and PLC feature sets has several downsides: the needless duplication of hardware (Ethernet is required on both devices), unnecessary complexity of programming (redundant alarm systems), and increased risks of security holes. Instead of two devices with overlapping functionality, one device with a feature set that covers requirements without duplication means less equipment to buy, program, and configure (see Figure 7).

Streamline architecture

Figure 7: Convergence of human machine interface (HMI), programmable logic controller (PLC), and connectivity. Instead of two devices with overlapping functionality, one device with a feature set that covers requirements without duplication means less equNetworking at the device and enterprise level is advancing and supporting new, streamlined automation architecture. Ultimately, this convergence can eliminate entire device levels and enable remote intelligence to reduce training costs, while empowering OEMs to take advantage of the best equipment from a range of suppliers.

Integrated architecture is enabling lean automation—boosting efficiencies and reducing waste—in terms of equipment and time. In a highly competitive business environment, providing best-in-class solutions that are intelligent, intuitive, and elegant delivers a real business advantage and yields control systems that are faster to design, commission, and maintain.

- Rich Harwell is advanced solutions manager at Eaton. Edited by Mark T. Hoske, content manager, CFE Media, Control Engineering and Plant Engineering, mhoske(at)cfemedia.com.

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