The MES system based on SOA and its application

With the further application of MES, the requirements of the system integration of manufacturing enterprises are more and more high. According to statistics, the global 40% of IT budget is applied to system integration, and the system integration problem in the MES is more prominent, this is because, MES is a enterprise ERP system and the bottom of the automation system integration of the middle-tier management software, mainly for the production of workshop, quality, Equipment and other aspects of detailed planning, information feedback and data analysis, is a link between the software, ERP systems and automation systems need to achieve two-way information integration, receive the production plan of the workshop ERP issued, and detailed planning and task allocation, to the ERP system feedback production, quality and other information, Control the automation system, read the corresponding data, and analyze it. Mes involves the low-level hardware system, real-time database and other specialized technology, belongs to a kind of complex integration technology. Because of the heterogeneity of data structure and information system, it is still very difficult to manage the discrete manufacturing workshop information and control process. The vertical integration between the high-level ERP system and the underlying control system is difficult to achieve. The existing solution can be integrated through static process logic programming in MES system, but the integration method is often lack of adaptability and extensibility. Thus, this integration approach does not meet the needs of today's dynamic manufacturing environment.

Service-oriented architecture or service-oriented architecture SOA is a software system architecture that is implemented by connecting independent functional entities that can accomplish specific tasks in order to address the need for business integration in an Internet environment. SOA (service-oriented system) adopts service-oriented business modeling technology and Web service technology, which realizes loose coupling between systems and realizes the integration and synergy between systems. The essential idea of Web services and SOA is to make information system individuals to form collaborative work on the basis of communication. Thus, internet-based manufacturing that integrates SOA can implement distributed information systems that can integrate static or dynamic shop-floor management systems into the entire enterprise architecture. Based on the SOA architecture, MES system not only integrates the whole enterprise application system tightly, but also realizes the dynamic application combination to meet the needs of the current dynamic manufacturing environment. Rockwell Automation's Factorytalk integrated production and Performance Suite delivers an soa-based MES solution that integrates all common requirements into the Factorytalk service platform and becomes a unified factory production model by applying an SOA architecture. This paper introduces the key technologies related to SOA and describes how to implement an integrated, extensible and universal MES system using SOA, and introduces the application of MES system in Jiujiang Changhe Automobile assembly MES system as an example.

Key Technologies

1.SOA

SOA services have a platform-independent self-describing XML document. The Web Service Description Language WSDL is the standard language used to describe the service. SOA services communicate with messages, which are often defined using XML schemas, also known as XSD (XML Schema definition). Communication between consumers and providers or consumers and services is much more common in environments where providers are not known. Communication between services can also be viewed as a key business document for internal processing within an enterprise. Within an enterprise, SOA services are maintained through a registry (registry) that acts as a directory list (directory listing) role. The application looks for and invokes a service at the registry center.

Unified description, Discovery, and integration of UDDI (Universald Escription,discovery,and integration) is the standard for service registration. Each SOA service has a quality of service QoS (QualITy of services) associated with it. Some of the key elements of QoS include security requirements (such as authentication and authorization), reliable communication, and the policy of who can invoke the service. As shown in Figure 1, the basic SOA architecture includes the interaction of Support service requesters and service providers, such as soap, WSDL, UDDI, and the specification for Web service discovery. A service provider typically uses WSDL to describe the Web services it provides and then publishes the WSDL description, and the service requester can obtain the WSDL description through a UDDI or other registry, requesting that the service be performed by sending a SOAP message to the service provider. The key of an SOA based MES system is how to describe the service reasonably, not to the UDDI, and the service requester to invoke the service discovery engine to find the service that needs to be used.

2.ESB

Enterprise Service Bus ESB (Enterprise service buses) is a new method that can provide reliable and guaranteed message technology. The ESB middleware product leverages the Web service standard and the recognized reliable Message interface protocol, MOM. Common features of ESB products include connectivity to heterogeneous moms, the use of Web Service Description Language Interface WSDL Encapsulation MOM Protocol, and the ability to transfer Simple Object Application Protocol (SOAP) transport streams on the MOM Transport layer. Most ESB product support enables direct peer-to-peer communication between distributed applications through the middle tier, such as integration agents.

The advent of the ESB has changed the traditional software architecture and offered a more inexpensive solution than traditional middleware products. At the same time, it can eliminate the technical differences between different applications, so that different application servers coordinate operation and realize the communication and integration between different services. Functionally, the ESB provides event-driven and document-oriented processing patterns, as well as distributed operational management mechanisms that support content-based routing and filtering, have the ability to transmit complex data, and provide a range of standard interfaces.

An ESB is not an application framework, nor is it a solution for an enterprise application, it is just a messaging module that invokes an enterprise service based on a message that can be embedded within an application framework, such as embedded within a spring container, or embedded in a workflow system. The ESB provides a framework and an easy way to implement an integrated MES system.