The Digital Twin – Enabling Realtime Closed Loop Manufacturing Optimization

By Bill Lydon, Contributing Editor, Automation.com

The Digital Twin has become one of the most powerful concepts of Industry 4. 0. The implementation of model-based, real-time, closed-loop monitoring, control, and optimization of the entire manufacturing and production process, the Digital Twin concept is helping organizations achieve real-time integrated manufacturing. The fundamental idea of the Digital Twin is to have a virtual model of the ideal manufacturing operations and processes, that will benchmark the actual production metrics in real time. The broadest implementation models include all of the factors that affect efficiency and profitability of production, including machines, processes, labor, incoming material quality, order flow, and economic factors.  This provides a wealth of information which organizations can use to identify and predict problems before they disrupt efficient production. The Digital Twin is a prominent example of a practical macro level closed-loop control that is now feasible with the advanced hardware, software, sensors, and systems technology now available.

A critical part of the creation of a digital twin is the need to have a complete information set, including the capture of real-time information with a wide range of sensors based on these requirements.  To facilitate this information collection, some common sensor strategies include:

Leveraging Existing Connected Sensors

This is typically the popular first step since it does not require physical installation of new sensors. What it does require is application engineering and a software project to link information to the IT network.  It may also require new software to be added to SCADA, PLC, HMI, DCS systems, in order to accomplish communication with enterprise and other systems.

Adding New Sensors to Existing PLC’s & Controllers

If there are unused sensor interfaces on the controller or available slots to add new interface cards, which can accommodate more sensors, then adding new sensors to existing controllers can be an option. This also requires application engineering in order to add these sensors to the program in the controller.  It may also require the addition of new software to to HMI, DCS systems in order to facilitate communication with enterprise and other systems.  In this strategy, there is a risk that making changes in these controllers and systems will create performance and operating issues, so it may require significant amount of systems and application engineering to ensure reliable operation.

Installing Edge Devices

In addition to practical concepts, like the Digital Twin, the Industrial Internet of Things (IoT) has led to companies bringing a wide range of edge devices to market. These edge devices are designed to capture information and communicate directly to enterprise systems and cloud applications, particularly Amazon Web Services and Microsoft Azure.   Many new sensors are not required to be part of the control & automation strategies in the plant, but are required to monitor operating parameters for a complete digital twin, and close the information loop. Edge devices typically connect directly to the IT network. The advantage to this is that they are non-intrusive having no or very  minimal impact on existing control software architecture. This can be an efficient way to communicate directly with production, maintenance and business systems.

Embracing Smart Sensors

There are new classes of smart sensors emerging that can communicate directly with production, maintenance and business systems. Wireless sensors can be an efficient way to acquire data with standard technology, including WirelessHART and ISA100, primarily used in process applications.   For discrete points, the IO-Link wireless version is an option.There are also a number of sensors that communicate over standard wireless ethernet Wi-Fi with various software interfaces.

OPC UA Can Help

OPC UA is emerging as a fundamental technology for implementing the Digital Twin. Digital FactoryOPC UA technology provides an efficient and secure infrastructure for the communications of contextual information, from sensor to business enterprise computing, for all automation systems in manufacturing and process control. OPC UA is leveraging the accepted international computing standards and putting automation systems on a level playing field with the general computing industry. OPC UA uses common computing industry standard Web Services, which are the preferred method for system communications and interaction for all networked devices.   The World Wide Web Consortium (W3C) defines a Web Service as "a software system designed to support interoperable machine-to-machine interaction over a network.” This is precisely the task of automation systems. OPC UA is being built into a number of sensors and other devices, in order to simplify the communication process.

A Path to Holistic Integration

With the implementation of the Digital Twin, manufacturers may be able achieve greater profits and competitiveness through Realtime Closed Loop Manufacturing Optimization. This is an example of holistic integration of all the factors of production, and though the Digital Twin is virtual, it represents one of the most tangible examples of the Industrial Industry of Things bringing value to today’s manufacturers.

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