Description:
TECHNICAL FIELD OF THE INVENTION
The present invention generally relates to cloud-based control system, more particularly to a multi-tenant, horizontally scalable virtual-PLC (Programmable Logic Controller) system for real-world industrial automation applications.

BACKGROUND OF THE INVENTION
A typical industrial automation system consists of sensors, actuators and other installed hardware at the field level (Figure-1). The control level consists of decision making entities such as PLCs, PID controllers and variable frequency drives (VFDs). The supervisory level consists of human machine interaction (HMI) dashboards and supervisory control and data acquisition (SCADA) software’s. On top of the supervisory level resides the planning level consisting of manufacturing execution system and the highest echelon is occupied by the management level consisting of enterprise resource planning (ERP) solutions.

Prior arts relates to the field of virtual programmable logic controllers (PLCs) are:
EP3502901B1 discloses a method for monitoring and reconstructing a virtual programmable logic controller (PLC), wherein the method is applicable to a server cluster, each of a plurality of servers in the server cluster comprises at least one physical core on which at least two micro kernels are deployed, the micro kernels on the at least one physical core comprises a first group of the micro kernel on which a virtual PLC is deployed, a second group of the micro kernel on which a soft guardian is deployed, and a third group of the micro kernel without the virtual PLC and the soft guardian deployed thereon. The prior art is applicable to a server cluster. In contrast, the present invention doesn’t necessarily require one. The core essence of the present invention is the de-coupling of the control plane from the data plane to provide elastic scalability in terms of control, execution and real-time decision making. In a server cluster, as discussed in the prior art, physical resource provisioning in not entirely dynamic. But in the present invention, each EPIC instance is a self-contained independent virtual controlling module which is able to execute industrial control logic without the dependency on any other physical or virtual resources. Each EPIC instance is sufficient to replace one physical PLC CPU in totality and hence it necessarily doesn’t need to depend on any other resources apart from the physical signals conveying modules.

CN108319161B discloses an industrial SCADA system simulation platform which can realize Modbus/TCP, IEC 60870-5-104 and BACnet/IP protocols in an industrial SCADA system. The platform is divided into four parts: the system comprises a simulation module for simulating a virtual controlled object, a PLC honeypot, an SCADA server and a protocol communication module. The platform specifically simulates the network data flow of an industrial SCADA system including various typical industrial control protocols, adopts a PLC honeypot-based construction mode, simulates the network data flow with large node scale, multiple protocols and special interaction modes in a real industrial control system environment by realizing the response behavior of the PLC to an SCADA server and the control function of a controlled object, and realizes the complete communication process of data among a process monitoring layer, a field control layer and the controlled object in the industrial SCADA system.

CN109240197B discloses a monitoring and reconstruction method and a monitoring and reconstruction device of a software-defined PLC (programmable logic controller), which are used for rapidly reconstructing a virtual PLC under the condition of no power-off. The method comprises the steps that when a soft daemon monitors a virtual PLC fault, the working state of each physical core on each server in a server cluster and the working state of each microkernel on each physical core are obtained; determining a target microkernel according to the working state of each physical kernel on each server and the working state of each microkernel on each physical kernel; and sending a reconfiguration instruction to the target microkernel, wherein the reconfiguration instruction is used for instructing to reconfigure the virtual PLC on the target microkernel.

CN106444616A discloses a filling production line control system based on the virtual-reality technology. The filling production line control system comprises a virtual simulation system, remote equipment and a PLC control system, wherein the virtual simulation system is bidirectionally connected with the remote equipment, and the remote equipment is bidirectionally connected with the PLC control system. The beer filling production line control system based on the virtual-reality technology has the advantages that animated simulation of a beer production line filling process can be performed, a control strategy can be applied to each process or object in a virtual environment through the interaction module of the virtual environment and an entity PLC so as to intervene and control a virtual production line, animated demonstration is updated in real time after the control measure is applied, the optimal control strategy and scheme of the production line can be determined fast, the filling process is fast and stable, the process is strict, and the system is promising in market prospect.

Hence there is a need to get rid of the hassle of changing the entire CPU and associated peripherals due limited physical work memory.

So, the present invention provides a virtual PLC system, which is free from the above-mentioned issues. Additionally, the virtual PLC system is implemented in a real world industrial automation setup. Extensive evaluations establish the system as a potent alternative to existent industrial PLC CPUs. The performance evaluation highlights the processing speed, scalability, interoperability and security features of the system and its ability to replace an existent industrial PLC in real-world applications. The prior art discloses a method for recreating a soft PLC in case any of the hard PLCs fail in a factory environment. Moreover, the soft computing in the prior art is limited to controlling a local plant using the soft PLC in an on-premise setting. The present invention implements a virtual PLC CPU hosted in a cloud accessible over the internet. It enables the user to control multiple physically distant plants using multiple instances of the EPIC. This enables rendering industrial control as-a-service. Unlike the prior art, the inventor of the present invention has also provided a method for cross-vendor and cross-protocol compatibility in rendering industrial control. The prior art discloses a method for monitoring and reconstructing a virtual PLC, however the present invention replaces a physical PLC CPU completely from the modern-day industrial automation setup. Only the signal marshalling modules and communication modules are necessary to convey sensor signals from the field to the virtual EPIC instance after which, the control execution takes place in the cloud and the actuation signals are conveyed back to the industrial shop-floor without the involvement of any control modules or PLCs.

OBJECT OF THE INVENTION
It is an object of the present invention to overcome the shortcomings of the prior art.

It is an object of the present invention to provide a virtual system for replacement of physical PLC system and eliminate the dependency on the performance and stability of a physical PLC CPU.

Yet another object of the invention is to provide EPIC architecture consists of a virtualized CPU in the cloud working in tandem with hardware input/output modules to execute control in the industrial setting.

Yet another object of the invention to control multiple physically distant industrial sites using a single EPIC (Emulated PLC in the Cloud) instance.

Still another object of the present invention is to eliminate the risk of loss of data and program by creating a back-up in cloud system.

SUMMARY OF THE INVENTION
The following disclosure presents a simplified summary of the invention in order to provide a basic understanding of some aspects of the invention. This summary is not an extensive overview of the present invention. It is not intended to identify the key/critical elements of the invention or to delineate the scope of the invention. Its sole purpose is to present some concept of the invention in a simplified form as a prelude to a more detailed description of the invention presented later.

In one aspect of the present invention there is provided

In another aspect of the present invention there is provided

Other aspects, advantages, and salient features of the invention will become apparent to those skilled in the art from the following detailed description, which, taken in conjunction with the annexed drawings, discloses exemplary embodiments of the invention.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
The above and other aspects, features and advantages of the embodiments of the present disclosure will be more apparent in the following description taken in conjunction with the accompanying drawings, in which:

Figure 1 depicts schematic diagram of conventional industrial automation system Vs industrial automation system with EPIC in accordance with an embodiment of the present invention.

Figure 2 depicts schematic diagram of industrial automation system with EPIC in accordance with an embodiment of the present invention.

Figure 3 depict architecture of the EPIC system in accordance with an embodiment of the present invention.

Figure 4 depicts comparison of scan cycle times for EPIC instance and physical PLC CPU (S7-400) in accordance with an embodiment of the present invention.

Figure 5 depicts comparison of response times for EPIC instance and physical PLC CPU (S7-400) with varying work memory ( in %) in accordance with an embodiment of the present invention.

Figure 6a depicts sequence diagram for end-to-end delay calculation in traditional PLC architecture in accordance with an embodiment of the present invention.

Figure 6b sequence diagram for end-to-end delay calculation in EPIC architecture in accordance with an embodiment of the present invention.

Figure 7 depicts end-to-end delay comparison between EPIC and physical S7-400 PLC in accordance with an embodiment of the present invention.

Figure 8a depicts multi-tenancy capabilities with one EPIC instance and 2 tenants in accordance with an embodiment of the present invention.

Figure 8b depicts variations in response time with increasing number of tenants and work memory utilization in accordance with an embodiment of the present invention.

Persons skilled in the art will appreciate that elements in the figures are illustrated for simplicity and clarity and may not have been drawn to scale. For example, the dimensions of some of the elements in the figure may be exaggerated relative to other elements to help to improve understanding of various exemplary embodiments of the present disclosure. Throughout the drawings, it should be noted that like reference numbers are used to depict the same or similar elements, features, and structures.

DETAILED DESCRIPTION OF THE PRESENT INVENTION
The following description with reference to the accompanying drawings is provided to assist in a comprehensive understanding of various embodiments of the present disclosure as defined by the claims and their equivalents. It includes various specific details to assist in that understanding, but these are to be regarded as merely exemplary. Accordingly, those of ordinary skill in the art will recognize that various changes and modifications of the various embodiments described herein can be made without departing from the scope and spirit of the present disclosure. In addition, descriptions of well-known functions and constructions may be omitted for clarity and conciseness.

All terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which various embodiments belong. Further, the meaning of terms or words used in the specification and the claims should not be limited to the literal or commonly employed sense but should be construed in accordance with the spirit of the disclosure to most properly describe the present disclosure.

The terminology used herein is for the purpose of describing particular various embodiments only and is not intended to be limiting of various embodiments. As used herein, the singular forms "a," "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" and/or "comprising" used herein specify the presence of stated features, integers, steps, operations, members, components, and/or groups thereof, but do not preclude the presence or addition of one or more other features, integers, steps, operations, members, components, and/or groups thereof.

Some terminologies used in the present invention:

1. MQTT stands for Message Queuing Telemetry Transport, which is a lightweight messaging protocol designed for small sensors and mobile devices with limited bandwidth. An MQTT broker is a server that acts as an intermediary for MQTT messages. It receives messages from clients (publishers) and routes them to other clients (subscribers) based on topics. Clients connect to the broker and publish messages to specific topics or subscribe to topics to receive messages. MQTT brokers handle the distribution of messages, ensuring that they reach the intended recipients efficiently and reliably.

2. MQTT Subscriber:

An MQTT subscriber is a client that connects to an MQTT broker to receive messages. Subscribers specify the topics they are interested in, and the broker delivers messages published to those topics to the subscribers. Subscribers can receive messages in real-time as they are published to the broker, making MQTT suitable for applications requiring low-latency communication and real-time updates. MQTT subscribers typically subscribe to one or more topics of interest and process messages accordingly.

3. OPC-UA Server:

OPC-UA (Open Platform Communications Unified Architecture) is a machine-to-machine communication protocol for industrial automation developed by the OPC Foundation. An OPC-UA server is a software application or component that exposes data and services using the OPC-UA protocol. OPC-UA servers provide a standardized way for clients to access real-time and historical data, as well as control and monitoring functionality, in industrial systems. Clients, such as OPC-UA clients or SCADA (Supervisory Control and Data Acquisition) systems, connect to OPC-UA servers to read data from sensors, control actuators, and exchange information with industrial equipment. OPC-UA servers offer features like authentication, encryption, and data modeling to ensure secure and reliable communication between clients and servers in industrial environments.

In summary, MQTT brokers facilitate communication between MQTT clients (publishers and subscribers) by routing messages based on topics, while MQTT subscribers receive messages published to specific topics. On the other hand, OPC-UA servers provide a standardized protocol for accessing data and services in industrial automation systems, enabling clients to interact with industrial equipment and exchange data securely and efficiently.

The present disclosure will now be described more fully with reference to the accompanying drawings, in which various embodiments of the present disclosure are shown.

In one embodiment present invention describes

According to one implementation of the present invention,

In an another embodiment the present invention describes to

In present invention, automation control level split into hardware control level and virtual control level (Figure-2). The present invention, decouple the control from the hardware dependencies and leverage the benefits of virtualized control to facilitate faster and more efficient decision-making. In present invention, the hardware constituents of control level are logically segregated into two levels. Specific controllers such as PIDs and VFDs occupy the hardware control level whereas the generic controller, i.e. the physical PLC is replaced with an equivalent virtualized controller hosted on cloud. This virtualized PLC, a sterm here as EPIC (Emulated PLC in the Cloud) are virtual control level.

The present invention is a virtualized CPU in the cloud working in tandem with hardware input/output modules to execute control in the industrial setting.

There are no work memory constraints as in physical CPUs and also no limit to the number of input/outputs that can be connected to an EPIC instance. Further, EPIC instances are capable to communicate with other physical devices working on different protocols and architectures thereby fostering vendor-independent cross-architecture interoperability.

Other advantages include ability to dynamically enhance and upgrade CPUs to facilitate faster program execution, providing backward integration to legacy hardware (such as digital and analog input and output modules, non-IP based sensors, controllers and actuators) encompassing them within a cloud based PLC architecture.

Using the existent automation system architectures, all program executes from a single location/ plant/industry within a physical CPU located at the site. The invented EPIC system utilized to control multiple physically distant industrial sites using a single EPIC instance.

The existing physical PLCs have poor fault tolerance. Once irrevocably affected, the programs are lost and consistent online backup remains elusive. The invented EPIC system totally eliminate the risk of loss of data and program as it creates a back-up in cloud system.

The present invention discloses a system for emulating Programmable Logic Controllers (PLCs) in a cloud environment to enhance industrial automation processes. The system comprises a cloud layer hosting an EPIC instance running a virtualized PLC Central Processing Unit (CPU) and a Message Queuing Telemetry Transport (MQTT) broker. An edge layer includes a gateway device running an MQTT subscriber and an OPC-UA server (master). A physical layer comprises field devices, remote I/O stations with a protocol conversion unit (slave), an interface module, and physical cards for capturing digital and analog inputs and setting digital and analog outputs. Communication between the EPIC instance and the edge device over the internet is secured using an encryption scheme based on OpenSSL.

The integrated virtual PLC system in the EPIC network reduces the scan cycle time and response time significantly, even at high work memory usage. It can emulate the latest versions of available PLC CPUs without requiring hardware modifications, supporting increasing work memory requirements elastically. The system allows sharing a single virtual CPU to execute programs from multiple different plants/factories, enabling cost-effective and efficient operation. The EPIC system provides practically infinite work memory and load memory for program execution, along with multi-tenancy support, without modifying associated hardware. Furthermore, the PLC communication peripherals (Input/Output Cards) function as a Common Controller for any other physical PLC architectures, enhancing interoperability and compatibility in industrial automation environments.

Table-1 shows the comparison between the EPIC architecture and standard industrial automation framework are:
Item Traditional Setup
PLC CPU Physical CPU EPIC Instance
Power Supply For CPU, I/O Cards and
Communication Processor Only for I/O Cards and
Communication Processor
Digital I/O Cards Physical Modules Physical Modules
Analog I/O Cards Physical Modules Physical Modules

The system developed in the present invention is:
(a) A cloud virtual machine instance consisting of a virtualized PLC CPU and a MQTT broker
(b) An edge gateway device running a MQTT subscriber and an OPC server (master) and,
(c) Field components consisting of a protocol conversion unit (slave), an interface module and physical cards for capturing digital and analog inputs and setting digital and analog outputs.
(d) OpenSSL based encryption scheme to secure the communication between the EPIC instance and the Edge device over internet.

Scan cycle time: Scan cycle time i.e. sum of time taken to check input status (input scan), execute the program (logic execution) and update output status (output scan) are compared between EPIC system and physical S7-400 CPU and illustrated in figure 4.

Particulars Physical S7-400 CPU EPIC system Early response by EPIC system
Bit Operation 7.5 nS 2.0 nS 5.5nS
Word operation 7.5 nS 4.0 nS 3.5nS
Fixed point operation 7.5 nS 3.8 nS 3.7nS
Floating point operation 15.0 nS 10.0 nS 5.0 nS
Hybrid operation 21.0 nS 15.5 nS 5.5nS
Table 2

Total response time: Total response time of a PLC CPU i.e. the difference in time between instant when the inputs are set to the instant when the output is generated by the PLC are compared between EPIC system and physical S7-400 CPU and illustrated in figure 5.

PLC Work memory (%) Physical S7-400 CPU EPIC system Early response by EPIC system
5% 10 mS 1 mS 9 mS
10% 16mS 1 mS 15mS
15% 24mS 2mS 22mS
20% 33mS 3mS 30mS
25% 45mS 5mS 40mS
30% 54mS 10mS 44mS
35% 61mS 14 mS 47mS
40% 66mS 17mS 49mS
45% 71mS 27mS 44mS
50% 74mS 35mS 39mS
55% 79mS 38mS 41mS
60% 82mS 44mS 38mS
65% 85mS 51mS 34mS
70% 88mS 53mS 35mS
75% 94mS 55mS 39mS
80% 102mS 57mS 45mS
85% 109mS 58mS 51mS
90% 115 mS 60 mS 55 mS
95% 225 mS 90 mS 135 mS
Table 3

End-to-end delay: Figure 7 illustrates the end-to-end delay comparison between the EPIC architecture and an industrial PLC (Siemens S7-400) with varying work memory %. It is observed that even though there is an additional delay due to communication between the edge device and the EPIC instance in the present architecture, yet, owing to the faster processing of the EPIC CPU in comparison to the S7-400 CPU and the ,the end-to-end delay in EPIC is much lower compared to the physical PLC. (Sequence Diagram for end-to-end delay is given in figure 6a & 6b)

Multi-tenancy: In cloud computing paradigm, multi-tenancy allows subscribers to share computing resources. With traditional physical PLC CPUs, multi-tenancy is impossible to achieve. But with the virtualized EPIC instances, it is possible to share a single virtual CPU to execute programs of multiple different plants/factories. This is a novel approach to serve multiple physically separated sites providing PLC based control through an utility computing model.

Industrial application program consuming 70% load memory and 27% work memory in the S7-400 CPU, consumes only 0.01% work memory and negligible load memory in the EPIC instance.

The following advantage can be list out from the present invention
• Enabling PLC control as-a-service to support multiple (physically distant) industries with a single EPIC instance
• Practically infinite load and work memory
• Easy backward compatibility to migrate non-IoT based industrial automation architectures towards industry 4.0 and industry 5.0

Industrial applicability
• Possibility of remote commissioning and remote troubleshooting through efficient human resource reuse
• Secured and assured data delivery
• Inclusion of small industries and MSMEs by extending much cheaper PLC control as a utility service and saving huge investment of setting up a traditional PLC architecture.
• Interoperability to remove vendor dependency
, Claims:
1. A system for emulating PLCs in a cloud environment, comprising:
A cloud layer including an EPIC instance running a virtualized PLC CPU and a MQTT broker;
An edge layer comprising a gateway device running a MQTT subscriber and an OPC-UA server (master);
A physical layer comprising field devices, remote I/O stations with a protocol conversion unit (slave), an interface module, and physical cards for capturing digital and analog inputs and setting digital and analog outputs; and
An encryption scheme based on OpenSSL to secure communication between the EPIC instance and the Edge device over the internet.

2. The system of claim 1, wherein the integrated virtual PLC system, as EPIC network, reduces the scan cycle time from 3.5 nS to 10 nS.

3. The system of claims 1 and 2, wherein the integrated virtual PLC system adapted to reduce the response time by 5 mS when work memory is at 5% and by 135 mS when work memory is at 95%.

4. The system of claims 1 to 3, wherein the integrated virtual PLC system emulates the latest version of available PLC CPUs without requiring any modification to the hardware, enabling support for increasing work memory requirements elastically.

5. The system of claims 1 to 4, wherein the integrated virtual PLC system adapted to facilitate sharing a single virtual CPU to execute programs from multiple different plants/factories.

6. The system of claims 1 to 5, wherein EPIC system enables practically infinite work memory and load memory for program execution and multi-tenancy support without modifying associated hardware.

7. The system of claims 1 to 6, wherein the PLC communication peripherals (Input/Output Cards) function as a Common Controller for any other physical PLC architectures.