Controls Definition & MES to Controls Data Flow Possibilities

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Controls Definition &

MES to Controls Data Flow

Possibilities

Rewritten and Published February 2000

Purpose

This paper creates a functional architecture for the data flow possibilities and composition of the MES to Controls layers in an integrated enterprise. A definition of Controls, detail of information shared, and expected benefits of integrating Controls to MES/ERP systems are included. Control System Definition

MESA defines a Control System as being "responsible for measurement, monitoring, and manipulation of production, people, products, and processes" within the environs of the process or shop floor. Within this definition, Controls would include automated process control systems, such as Programmable Logic Controllers (PLCs) and Distributed Control Systems (DCS); specific-purpose automation, such as Barcode Readers and Radio Frequency Identification products; and software-based controllers, such as those found within motion control, robotic control, numeric control, and open "soft" PLCs. Controls also include discrete products, such as sensors, drives, motors, and transducers that can supply real time information into the PLC- or DCS-based systems. Context

MESA White Paper Number 2, "MES Functionalities & MRP to MES Data Flow Possibilities," defines the communications, data types, and data flow between the Enterprise Business Systems and Factory Floor Information Systems. The ERP/MRP environment is

transaction-based. Data is exchanged in direct response to scheduling, routing, or production planning requirements. Contrast that with Controls where decisions are made in seconds or fractions thereof in response to process, operator,

or materials operations needs. This difference of a real-time environment and real time response requirements affects most transactions and executions that occur in the Controls layer.

Background: MES Defined

MESA International defines MES as "systems that deliver information enabling the optimization of production activities from order launch to finished goods. Using current and accurate real-time data, MES guides, responds to, and reports on plant activities as they occur. The resulting rapid response to changing conditions, coupled with a focus on reducing non-value added activities, drives effective plant operation and processes." Manufacturing Execution Systems (MES), as defined by AMR, are "information systems that reside on the plant floor between the planning systems in offices and direct industrial controls at the process itself."

There are 11 MES functions:

● Resource Allocation and Scheduling ● Operations/Detail Scheduling ● Dispatching Production Units ● Document Control ● Data Collection/Acquisition ● Labor Management ● Quality Management ● Process Management ● Maintenance Management ● Product Tracking and Genealogy ● Performance Analysis

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Each function contributes to the collection of data required to monitor, track, cost, and control product manufacture in real time.

As MES is a manufacturing-oriented system, it must interact and share information with other manufacturing applications. These applications include front-end business systems, such as Sales Support, Supply Chain Management, and

Enterprise Resource Planning; and manufacturing-focused systems, such as Product/Process

Engineering and Controls. Relevant data residing in the MES can be integrated with these systems to better track, monitor, and reconcile the plant processes.

The Controls environment impacts the creation of the products from material release and

manufacture through test and final processing stages. Coupled with an MES, the user has total shop floor control and feedback.

Emerging Automation Trends

This diagram (figure 2) models the data access from a Control system.

Five functional areas in an Automation hierarchy-ERP, MES, Supervisory Control, Controls

(Automation Systems) and Sensors/Devices have converged into a less structured model based on the acceptance of open systems and software standards, such as XML, COM/DCOM, Java and Corba.

These standards have streamlined both data acquisition and analysis, and have eliminated many of the boundaries that existed between the MES, business system, and plant floor layers. KEY: MES = Manufacturing Execution Systems SSM = Sales & Service Management SCM = Supply Chain Management ERP = Enterprises Resources Planning

P/PE = Product & Process Engineering

CONTROLS = PLC, DCS, line & machine

control

MES provides an information hub that links to and

sometimes between all of these systems. MES overlaps with other manufacturing system types, which also overlap with each other. For example, scheduling may appear in both MES and SCM; labor management in MES, SSM, and the HR function or ERP; document control in MES and P/PE; and process management in both MES and Controls. Degrees of overlap vary by industry and implementation.

MES Context Model

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Now, a common database and data model can be used throughout the enterprise.

Focus of the Control Systems

The control layer concerns inputs and outputs, or status points, of the process. These points can be relayed as they occur, trended as part of the functionality within the Controls themselves, or they can be stored in real-time historical databases for analysis, all to assure that the product or process is progressing within defined limits. These steps keep the Control Systems' focus on the process or operation itself-assuring that all of the people, equipment, and resources involved within the process are correctly and fully utilized.

Interaction between the Control and MES layers is dynamic. Control information/status can be accessed as it is created, satisfying SPC and SQC needs. It can also be batched or stored within a database for later examination to meet labor tracking, maintenance, or process analysis needs. The Control layer can query the MES for status changes-recipe, material, work order updates, work-in-process status, or other operating instructions.

It is important to note that MES is not concerned just with continuous process. Critical Control layer information exists within discrete manufacturing processes, such as those found within the automotive or electronics industries. In these industries, MES looks at the bills of material tracking, routing, yields, and the associated quality parameters.

The Control layer is the final layer in the office-to-factory-floor paradigm. Information needs from the business systems (material utilization to WIP to final package counts to shipping information) are all based upon available information from the Control layer. To gather this information, software such as drivers, data inquiry tools,

transaction/database mapping, and object

interfaces, along with the plethora of factory-floor network architectures and/or hardware drivers, are required to access the data that already exists in various forms.

Implementing MES: Data Flow

Possibilities

So how does MES function in a typical factory? Most of the components described within the MES to Controls layer already exist. Figure 3 describes the operations, interactions, and data flow

between the ERP (Business), MES (Execution), and Controls layers.

From the left in figure 3, you can see the ERP system. ERP systems work with a time horizon of days, weeks, months, and years--that is the 100x time factor. The ERP system notes product usage, customer orders, and materials requirements, and sends requests to the Execution (MES) layer to build more products or inventory to fulfill customer orders.

The MES systems are responsible for carrying out the product manufacture, and all operations associated with the creation of those products. Recipes or product design details can be stored at the MES layer, which supplies the "how to build" instructions for the Control layer. These

instructions are used for both labor and physical devices. As the MES systems work in short time spans (one day, one shift, one hour, minute or second) but not in the speeds associated with Controls, the time factor is 10x.

Once the instructions, programs, documents, software, and other manufacturing requirements for support systems are transmitted, the Controls layer is then responsible for carrying out the process. The Controls function uses all of the resources on the factory floor (hardware, software, and people) in a manner consistent with the goal of producing a product that meets or exceeds desired specifications.

Controls work in real-time. Their time factor of 1x (less than a second) means that there are always operations occurring to refine or correct the process to maintain desired tolerances or outputs. The "Equipment," "People, " and "Devices" carry out the finite instructions for the process output. Drill-down inquiries, or status indicators, from the Execution layer can spontaneously access

information created on an as-needed basis for process control.

Bilateral inquiries can emerge from either layer. These inquiries are used to measure

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progress-to-plan, to communicate unscheduled changes, or to announce alarms, events or changes that have occurred.

MES serves as a two-way window into the

manufacturing process, integrating and facilitating key information flows and commands between Controls and business planning systems for total resource and enterprise management. MES can be the cornerstone in achieving the

ERP/MES/Control Integrated Enterprise of tomorrow.

Object Distribution Models for

MES to Controls

There are two standardization efforts for software/object distribution - CORBA for Unix and COM/DCOM for the Windows NT platform. MESA International participates in a consortium to create a working model that utilizes both software standards for MES object distribution, as detailed on the next page in figure 4.

Most Controls products are designed to interface with other applications, and have built-in software interfaces utilizing either COM/DCOM or

CORBA, so the object distribution model created by NIIP-SMART will be extendible down to the hardware layer.

Soft Control: A New Means for

Distributing and Control

The newest evolution within the Controls world is to create "soft" or "open" software-based versions of traditional hardware-based automation

equipment. The soft controller has implementations in Programmable Logic Controllers (PLC), I/O, Motion, and Operator Interface. Most prevalent are PLC-based soft controllers. Normally running on Windows NT, they can either run as a service on top of the NT operating system, or within the operating system, essentially "taking control" of the processor. Real-Time Enterprise Management

(MES in an Enterprise Data Flow)

Manufacturing Execution System

Control System (or Manual Operation) ERP/MRPII

System Work

Orders Control ParametersOperator Instructions

Checks Resources

Creates Manufacturing Plan Releases Work Orders Tracks WIP

Displays Operator Instructions

Updates ERP System Order Status

WIP Status Quality Data

Build History _{Operation/Job Status} Machine/Operator Status Process Values Customer Orders Equipment People Devices Time Factor 100 X 10 X 1X Work Instructions figure 3

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The importance of Soft/Open Control is:

· No hardware restrictions to proprietary drivers, configurations, or manufacturers

· Can co-exist with legacy control products · Provides a "cleaner" method of data acquisition using Microsoft Foundation Class or Java-class objects

· Eliminates proprietary/manufacturer specific networks

Benefit of Soft/Open Control

for MES

The benefit of a software-based Controller is data acquisition and integration into the supervisory and business systems, such as MES and ERP. Using the same standards created for object distribution (COM/DCOM or CORBA), soft control can seamlessly imbed real-time process data into these business applications.

Soft Control also allows data sharing in a number of disparate applications. For example, a Word document, Spreadsheet, and a Quality Control application can theoretically all share the same data, from the same source, be that a PLC, DCS system, or barcode reader.

Lastly, Soft Controllers can act as a data server or client via OPC - OLE for Process Control. OPC builds on OLE by allowing Control Systems to standardize on certain data/object definitions, and

also to standardize on their method of distribution. OPC can theoretically minimize data integration at both the Control and MES layers.

Fieldbuses are the last level of data acquisition for MES to Controls.No discussion of Controls would be complete without a cursory overview of factory floor- level sensor/device and field networks. These digital networks serve to link industrial equipment with both the controllers and peer-level devices, either on a scanned, exception, or polled event basis.

For data transmission, Ethernet has been gaining in favor. Long used in business applications, there are moves underway to increase Ethernet's packet size and transmission rates to meet the speed and information needs of Controls. Ethernet normally runs with TCP/IP communication layers, which define how a piece of information travels from one machine to another (IP) and a reliable connection between two running processes (TCP).

Agent

MES Future Technology Model

Subcontractors

MES Object Model Object Request Broker

(i.e. CORBA, COM/DCOM)

Firewalls Application Resource Negotiator Workflow Management Knowledge Management Data Mediator Product Data Management Agent Agent Legacy Application Legacy Application Agent Application Application

MES is incrementally evolving toward a consistent object model, along with the rest of the software industry. In this future information systems model, MES uses an object request broker to pass manufacturing events to workflows, agents, and external systems (SCM, ERP, Legacy, SSM, P/PE, Controls, Data Warehouse) through data mediation. Unique plant business policy is represented as sets of rules within knowledge management

which can initiate manufacturing events. Firewalls

Manufacturing Agent

Agent

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Components and Definition of

Terms

Components of the Control layer

The components of the Controls layer include, but are not limited to:

· controllers(programmable controllers, computers, robots, and Distributed Control Systems or DCS);

· sensing devices (limit switches, photoelectric controls)

· CNC (Computerized Numeric Controllers),

· motion control

· user/operator interfaces · display devices

· specialty software(including human/machine interface, quality systems, control programming software, and automatic identification configurators)

· intelligent input devices, such as smart transducers, or barcode and radio frequency identification.

In addition, the Control layer would include factory networks for both devices and

peer/control products, along with an information bus and associated middleware/interface software for sending Control-layer information into the ERP and MES layers.

Definition of Terms

COM:Component Object Model is a binary component used in several objects (programs) which may be combined to produce desired results - originated by Microsoft.

DCOM: Distributed Component Object Model is a highly optimized protocol extending COM to networks and was also originated by Microsoft

HMI:Human/Machine Interface are software systems that graphically depict the status of machines, controls, and equipment that reside on the factory floor. HMI can also be hardware, such as an operator message display, that

communicates the condition of the equipment or process/operation, or it can provide work instructions. HMIs include pushbutton stations, software, display stations, and message displays.

OLE: Object Linking and Embedding, from Microsoft, controls how objects may interrelate. Objects can be linked or embedded.

OPC:OLE for Process Control is a communication

standard for Control Equipment based on OLE concepts. The foundation's goal is to develop an open and interoperable interface standard based on the functional requirements of OLE/COM and DCOM technology that fosters greater

interoperability between automation/control applications, field systems/devices, and business/office applications.

PC-Based Control:Control functions performed within a personal computer and related software.

Recipes:Control or Process instructions that include work instructions (what and how to build), equipment instructions (what and how to use), operator instructions (who to use,

when/how to use, safety, data collection, scheduling), machine instructions (which to use and how), and scheduling instructions (when to build).

Soft/Open Control:Software-based dedicated controllers that use an "open" operating system (Windows NT or Linux, a real time Unix-derivative operating system). Benefits include lower hardware cost, reduced set up time, wider choices of suppliers, and a "cleaner" method of data acquisition using either Java or Microsoft-class objects.

User Interface Data:Data necessary to communicate machine or process status to operators.

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Created by: MESA International 303 Freeport Road Pittsburgh, PA 15215 USA +1.412.781.9511 Fax: +1.412.781.2871 E-mail: [email protected] http://www.mesa.org

Controls Definition & MES to Controls Data Flow Possibilities