Shulou(Shulou.com)11/24 Report--

This article comes from the official account of Wechat: knowledge Automation (ID:zhishipai), the original title: "Peng Yu | Virtual PLC towards a new horn for practical software definition automation", author: Peng Yu

What does the virtual PLC system look like? It has always sounded like a mysterious idea, but now there is a more landing action.

In Amazon's AWS partner Pavilion at this year's Hanover Expo in Germany, a start-up called Software Design Automation showed off a solution for virtualized PLC systems. The system of virtualized PLC can not only replace the hardware and software binding of traditional PLC through the digital twinning of CPU, but also run the software to deploy and manage the PLC group in the cloud, as well as the man-machine interface to manage the operation of the PLC group.

A nearly practical solution because hardware-based functions are being systematically replaced by software, software-defined technology and software-defined equipment are very common in the IT world. But can this concept be applied to the real-time control of industrial machinery and equipment? Although the idea sounds impractical, the answer is yes. The premise is that an appropriate framework must be put in place to program, deploy, and monitor the performance of virtualization automation assets.

The Munich-based startup named SDA is following in the footsteps of software-defined technology in the IT field, leading the OT field to create a software-defined automation (Software Defined Automation, SDA) solution. It virtualizes the traditional PLC hardware and manages it on this basis. Just like managing software assets. They developed the PLC operation suite for automation engineers, through the controller's digital twin virtual commercial PLC. For example, it could work closely with Bosch Rexroth and Tulip, a low-code supplier developed by Massachusetts. Alternatively, it can use Siemens hosted by GitHub or Bifu's open source PLC to implement ICaaS (Industrial-Control-as-a-Service).

This technology path to service through virtualization enables factory automation practitioners to benefit from hardware-independent remote connections, simplified collaborative PLC engineering, and virtual PLC with real-time deterministic behavior running on standard general-purpose IT hardware such as servers. Up to now, according to the data given by SDA, this virtual real-time controller achieves the actual effect of deterministic control cycle time < 10ms. This is probably the most practical solution for the commercialization of virtual PLC. This vPLC solution allows deterministic real-time control on virtual edge servers, combined with a comprehensive cloud-based vPLC management interface.

Along with cloud automation engineering solutions, it enables customers to increase flexibility, productivity, and security while acquiring vendor-specific industrial automation hardware. SDA's solution enables customers to migrate from traditional PLC to fully virtualized PLC controls that run on the VMware Edge edge computing stack on traditional IT servers close to the workshop. Automation engineers can continuously monitor vPLC through the cloud-based control panel, just like using traditional PLC. SDA's cloud-based application allows users to test, manage, and monitor instances of vPLC from a server located in the factory.

SDA Industrial Control as a Service breaks the proprietary silo in the control technology stack and enables the micro-service architecture above the real-time control layer to interact natively through API, just like any other modern enterprise information system-turning the factory into a software system. Virtualized PLC systems are implemented around existing cloud-based PLC management software (SDA TechOps), PLC code versions and collaborative software (SDA DevOps) authorized by Git, and software (SDA Virtual PLC) that virtualizes PLC on edge servers.

Automation engineers using SDA TechOps can now manage the PLC of vendors such as Siemens, Bosch Rexroth and Bifu, just like cloud-based software systems, where deployed code is completely transparent, code changes are fully traceable, and code refreshes can be performed automatically in minutes. SDA DevOps introduces Git-based version control for PLC to facilitate the transition to the collaborative approach of modern developers. Each project update is securely backed up, changes to individual objects are versioned, and displayed in structured text language and ladder language applications in a significantly deeper way through a simple web interface. These measures help automation engineering teams work together more efficiently, speed up development, and minimize risk. Once there is a new feature to deploy, press a button and deploy to the entire PLC system in a few minutes.

SDA's virtual PLC decouples real-time control from proprietary hardware through virtualization. SDA works with VMware, a well-known virtual machine software developer, to run virtual PLC on any x86 server, ensuring that each virtual PLC achieves a scan cycle time of < 10ms. Automation engineers can continuously monitor the operation of vPLC through cloud-based control panels, just like traditional PLC. Automation engineers can also debug and launch new Codesys controllers in minutes and pay a monthly fee for each virtual controller.

"this is a big change in the rules of the game in the industry," says Josef Waltl, founder of SDA, which makes automation the starting point for the transformation of the manufacturing business. Whether it is a large team of engineers driving the further development of automation complexity, or automation experts within the enterprise, they can manage all PLC remotely, instead of monitoring PLC like firefighters all day long. Work closely with equipment suppliers such as Bosch Rexroth and Tulip to provide customers with end-to-end solutions as a leading front-line operation. For example, any Edge IO from Tulip can be converted to PLC, as long as the first-line operating platform is integrated with the real-time controller through a simple API call without increasing the hardware cost.

This move will put industrial automation on a par with other industries in IT software development. The pace of automation can finally go a little faster.

Deep thinking on PLC Virtualization Virtualization has a concise definition: software whose external characteristics and behavior is consistent with specific hardware is actually virtualizing specific hardware. In the development of IT over the past 60 years, no other progress has provided more quantifiable benefits than virtualization, such as reducing costs, increasing flexibility, showing more scalability, improved reliability, improved performance, and so on. The impact of virtualization in the IT field is enormous.

So why didn't the virtualization trend rapidly extend to the OT world? In fact, the OT industry has spent about a decade observing whether virtualization can be used in industrial automation. People gradually find that there are more and more virtualized applications in OT environment, and more and more vendors fully support running SCADA and DCS platforms in virtualized environment. Recently, it has also been found that many DCS vendors have deployed virtual controller CPU when they need to improve the performance of their existing series of controllers or reduce controller costs for strategic customers. These virtual DCS controllers run on commercial IT hardware such as Windows or Linux servers. Typically, these virtualized DCS controller products do not appear in the product catalog and do not even have a title or inventory number.

As another important pillar of industrial automation, how will the PLC industry respond to the process of virtualization? In fact, if PLC is to be fully virtualized, it must virtualize all vendor-specific CPU, backplane, rack, IO modules, and related networks. It requires virtualizing the functions of running PLC CPU on a general industrial PC, or a cluster of PLC controllers that run centrally on general IT server hardware. With optical backplane, deterministic fieldbus and / or real-time Ethernet systems can be switched; similarly, virtualized IO modules can consider independent I / O terminal strips based on ARM. It is also necessary to support commercial redundant I / O modules / controllers and so on to form a virtual PLC software container.

So what benefits does this virtual PLC software container bring to the OT industry?

PLC is a kind of very mature industrial controller. Modicon PLC introduced in 1969 almost established its structure and shape from the very beginning, but modern PLC has not changed much in these aspects. This original design has stood the test of time. As for its functions and attributes, even the tender documents submitted by GM GM in 1968 are still not out of date. Its functional requirements are still an important part of modern PLC.

With the development of more than 60 years, PLC has become an evergreen tree of industrial control.

If we try to improve the performance of PLC by virtualizing PLC and make up for some of its shortcomings, the first thing to bear the brunt is to aim at reasonable application scenarios. There is no need for OEM machines that use a large number of small PLC to virtualize their PLC, and the result obviously outweighs the loss, unless a PLC cluster is formed when the machinery is concentrated in a workshop. The reliability of a PLC is high enough, and its anti-interference ability is strong enough. It can run normally for more than ten years in the harsh industrial environment, and the maintenance quantity is very small. It doesn't make much sense if virtualized PLC can be replaced functionally, but can't achieve its reliability, electromagnetic compatibility, and environmental adaptability. Especially for a number of occasions for the production of high-output, high-value products (such as cigarette machinery, high-speed filling machinery), once downtime brings great losses, the virtualization of PLC will outweigh the gain. Similarly, virtualized PLC does not have the opportunity to show its ability in high-tempo production and high-speed motion control, because for more than a decade from 2012 to now, the deterministic real-time control cycle of all the experiments and software products that explore virtual PLC has never crossed the threshold of 10ms.

Is this the insurmountable gap of virtual PLC? Whether this is the essence of virtual PLC operation remains to be seen.

How do you realize the value of virtualizing PLC? In an industrial environment, PLC has earned a reputation for being economical, reliable, robust, modular and easy to support. So can virtualization help PLC become faster, cheaper, and more robust? If enterprises count their company's OT assets and IT assets respectively, they will often find that OT equipment assets not only far exceed IT assets in quantity, but also exceed IT assets in value. For example, according to the statistics of one of the top three energy companies in the world, this multinational company with more than 50, 000 employees has more than twice its global OT equipment assets.

The reason is self-evident. There are many kinds of OT assets, and the degree of standardization and generalization is poor, while the equipment of IT assets has already been highly standardized and universal. In this sense, once PLC can be virtualized, people can operate on different brands of PLC systems such as Siemens, Schneider and Rockwell on the same PLC hardware. In this way, a PLC cluster can run in the form of software on a general-purpose IT server, or on an industrial PC, just like running multiple different Windows and Linux operating system environments in VMWare or VirtualBox. Full PLC virtualization will allow you to run Schneider Electric's Unity XL programming environment and then migrate to Rockwell Automation Studio 5000 or Siemens STEP 7 without changing any hardware assets on site. This prospect must be enough to attract more business managers, the key is that it must be practical and reliable enough.

How can Virtualization reduce OT costs? First, it will create a "PC compatible" version of PLC and open the door to more vendors. Later commercial equipment can still run on engineering tools originally provided by major suppliers of PLC. Second, customers will no longer be locked in a single supplier of all hardware. Over the years, fieldbus and other open standards have helped solve the problem of vendor locking to some extent. However, in the decades after the initial deployment, most of the hardware and software of many customers are still at the disposal of PLC / DCS vendors. The trace of binding is very obvious. Finally, it will also upend the electrical distributor model. The position of the middleman has become so precarious that it is no longer necessary to purchase PLC / DCS software and equipment through authorized dealers. Because the more general-purpose and commercialized hardware eliminates the demand for these middlemen, the profits made by middlemen serving these products will naturally be wiped out.

Virtualization is obviously known for its flexibility and adaptability. Fully virtualized PLC can greatly improve the flexibility of OT, especially as the market is more and more inclined to small batch and multi-variety. The rapidity and flexibility of production line configuration is a key feature of intelligent manufacturing, and virtual PLC can fully meet this key point. It uses general IT equipment to enter the control link of the production line, which is undoubtedly to make low-cost hardware equipped with more advanced automation system, promote innovation in OT environment, and accelerate the coordination and debugging time of PLC cluster when changing varieties.

At the same time, create a virtual version of the running process and test the updated process according to real-time data to see the impact of the changes on the system, which is also an urgently needed feature for production switching. PLC virtualization can even switch seamlessly between vendors of automation hardware products. For example, a manufacturer who runs with one of Rockwell's products may transfer to Schneider Electric's system to prepare for the next product operation after they decide to change production direction. At this point, the virtualized PLC may not have to change the hardware or very little, but only need to make changes and deployment of the application software. Virtualization at all levels above L2 in an OT environment has made it easier to deploy patches, create backups, and support endpoint protection, so such actions are now targeted at the L2 level, that is, facility virtualization at the control layer.

Today, the processing power of most PLC CPU is far less than the CPU of the commercial IT. Even if you take a step back and adopt industrial PC as the CPU of PLC, you can still achieve considerable cost savings. Of course, industrial PC is not designed to have a life span of 10 to 15 years, as in the case of PLC CPU, but this risk can be offset by clustering and additional levels of redundancy. From the perspective of information security, virtualized PLC can get much more technical support than traditional PLC. For example, virtual containers can also allow software firewalls to control traffic to and from PLC; virtual container environments will run on Linux or Windows environments, which are more robust in terms of network security than traditional real-time operating systems (RTOS) deployed on PLC.

Of course, there are some challenges for PLC virtualization to become a reality. Among them, the most critical is how to address the certainty of PLC and the uncertainty of IT cloud services; how to solve the problem of functional security in the OT industry through the external characteristics and behavior of products with specific hardware and software bundles such as PLC through virtualization; and some basic challenges brought about by the performance-centric nature of IT virtualization. In addition, the virtualization of PLC also expects a number of suppliers, including traditional PLC vendors, to participate in this technological change, and the suppliers who turn this potential advantage into reality may become "VMWare in OT" and will have greater market influence.

Summary: the future-oriented judgment of DCS, SCADA and PLC, the three most commonly used basic systems in the field of OT, has shown the trend of virtualization, and has also attracted the attention of some domestic enterprises with strong technology sensitivity. For example, Huawei Zijin Lab cooperated with Baoxin and Shanghai Jiaotong University to try to carry out the experiment of virtual IP system with the support of deterministic PLC communication; CGN cooperated with Shanghai Jiaotong University and Huawei to use multiple hot backups of virtual controllers to replace one-to-one hardware backups for the virtualized DCS of the conventional island of nuclear power plants. With reference to the international and domestic exploration of virtualization in the field of OT, the author makes the following basic judgments:

Virtualization has great potential in the field of OT, especially the realization of low-cost software thermal redundancy and the flexibility and adaptability of PLC clusters to production process changes. In the case of a single PLC system or DCS system, this is not enough to attract the attention of management. But for a large enterprise, the cost advantages and performance advantages brought about by the changes of virtualized PLC / DCS have gained the interest and support of some far-sighted senior managers. This is the vast world and potential power of virtualization in the field of OT.

There are still some challenges for PLC virtualization to become a reality, the most important of which is how to solve the time certainty of PLC and the uncertainty of IT cloud services. Because PLC often has to face the control requirements of high tempo and high speed, it has to deal with applications with scanning time of the order of magnitude of 1ms. Relatively speaking, the virtualization of DCS and SCADA is not so demanding in this respect. Under the support of current technology, virtualized PLC can only implement applications of an order of magnitude of 10ms, so the application scenario of virtualized PLC should be limited. For example, creating a data acquisition system that meets the requirements of the industrial Internet using edge servers and edge I / O virtualization solutions can avoid the lack of time certainty caused by virtualized PLC. At the same time, there is no need to try to use virtual PLC to solve the problem of motion control.

At present, the more appropriate solution seems to be to implement the deployment and monitoring of virtualized PLC on cloud servers and the operation control of virtualized PLC on edge servers. This solution is suitable for large-scale PLC cluster systems.

On the whole, traditional PLC has a series of outstanding advantages, such as long-term reliable operation in harsh industrial environment, good ease of use, high degree of modularization, easy maintenance and so on. How to inherit and carry forward in the new situation needs to be honed and accumulated experience, which depends on the engineers and technicians who are rich in practical experience and can solve practical problems in the field of OT. In this sense, if virtual PLC wants to gain a firm foothold and carry forward in industrial control, we must pay attention to the role of existing traditional PLC practitioners. The technological reform of virtualized PLC is not only competent and promoted by pure software developers.

Brief introduction to the author Peng Yu: Shanghai Industrial Automation instrument Research Institute, PLCopen China Organization Editor Lin Xueping: general Manager of Beijing Lianxun Power Consulting Co., Ltd., part-time Professor of Jingyi College of Tianjin University

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