Standard Architecture of PCS7

DCS (Distributed Control System)

A distributed control system (DCS) is a control system for a process or plant, wherein control elements are distributed throughout the system. This is in contrast to non-distributed systems, which use a single controller at a central location. In a DCS, a hierarchy of controllers is connected by communications networks for command and monitoring.

A DCS typically uses custom designed processors as controllers and uses both proprietary interconnections and standard communications protocol for communication. Input and output modules form component parts of the DCS. The processor receives information from input modules and sends information to output modules. The input modules receive information from input instruments in the process (or field) and the output modules transmit instructions to the output instruments in the field. The inputs and outputs can be either analog signal which are continuously changing or discrete signals which are 2 state either on or off Computer buses or electrical buses connect the processor and modules through multiplexer or de multiplexers. Buses also connect the distributed controllers with the central controller and finally to the Human–machine interface (HMI) or control consoles.

Application

Distributed control systems (DCSs) are dedicated systems used to control manufacturing processes that are continuous or batch-oriented, such as oil refining, petrochemicals, central station power generation, fertilizers, pharmaceuticals, food and beverage manufacturing, cement production, steelmaking, and papermaking. DCSs are connected to sensors and actuators and use set point control to control the flow of material through the plant. The most common example is a set point control loop consisting of a pressure sensor, controller, and control valve. Pressure or flow measurements are transmitted to the controller, usually through the aid of a signal conditioning input/output (I/O) device. When the measured variable reaches a certain point, the controller instructs a valve or actuation device to open or close until the fluidic flow process reaches the desired set point. Large oil refineries have many thousands of I/O points and employ very large DCSs. Processes are not limited to fluidic flow through pipes, however, and can also include things like paper machines and their associated quality controls (see quality control system QCS), variable speed drives and motor control centers, cement kilns, mining operations, ore processing facilities, and many others.

A typical DCS consists of functionally and/or geographically distributed digital controllers capable of executing from 1 to 256 or more regulatory control loops in one control box. The input/output devices (I/O) can be integral with the controller or located remotely via a field network. Today’s controllers have extensive computational capabilities and, in addition to proportional, integral, and derivative (PID) control, can generally perform logic and sequential control. Modern DCSs also support neural networks and fuzzy application. Recent research focuses on the synthesis of optimal distributed controllers, which optimizes a certain H-infinity or H-2 criterion.

DCSs are usually designed with redundant processors to enhance the reliability of the control system. Most systems come with displays and configuration software that enable the end-user to configure the control system without the need for performing low-level programming, allowing the user also to better focus on the application rather than the equipment. However, considerable system knowledge and skill is required to properly deploy the hardware, software, and applications. Many plants have dedicated personnel who focus on these tasks, augmented by vendor support that may include maintenance support contracts.

DCSs may employ one or more workstations and can be configured at the workstation or by an off-line personal computer. Local communication is handled by a control network with transmission over twisted -pair, coaxial, or fiber-optic cable. A server and/or applications processor may be included in the system for extra computational, data collection, and reporting capability.

What is PCS7?

The process control system SIMATIC PCS 7 is an integral component of Totally Integrated Automation (TIA). Totally Integrated Automation, is the unique platform offered by Siemens for unified and customer-specific automation in all sectors of the production, process and hybrid industries.

SIMATIC PCS 7 takes care of the standard process control tasks. You can also use SIMATIC PCS 7 to automate secondary processes such as filling, packaging or input and output logistics for a production location.

Process data are available across the enterprise via the connection of the automation level to the IT system. The enables you to centrally execute evaluation, coordination and optimization of manufacturing and business processes.

The modular architecture of SIMATIC PCS 7 is based on selected hardware and software components. The PCS 7 plant is linked to the enterprise information network via standardized interfaces based on international industrial standards for data exchange.

PCS 7 is a process control system with many automatic functions to assist you during configuration. It enables you to create a project fast and conveniently. You will get to know some of these automatic functions in this Getting Started. At the same time, PCS 7 provides the advanced user many options for creating individual, project-specific solutions customized to the requirements at hand.

PCS 7 is a process control system that supports you during configuration with numerous automatic functions so that you can create a project quickly and conveniently. You will get to know some of these automatic functions when you work through this Getting Started. When you have become an advanced user, you will also find that PCS 7 provides a variety of options with which you can create individual and project-specific solutions tailored to your specific requirements. These individual solutions are, of course, not part of this Getting Started – for more information in this direction, you can refer to the configuration manuals once you are familiar with the basic functionality.

 

Basic structure of a PCS 7 plant

The modular architecture of SIMATIC PCS 7 is based on selected hardware and software components from the standard range of SIMATIC programs. The PCS 7 plant can be incorporated into the company-wide information network using interfaces based on international industrial standards for data exchange - such as Ethernet, TCP/IP, OPC or OLE DB communication. 

The System/Components of PCS 7No.System/component In a PCS 7 plant, PC components are used for the following stations: 

-Engineering stations (ES)

-Operator stations (OS)

-Maintenance station (MS)

-BATCH stations (BATCH)

-Route Control stations (RCS)

-Stations for connecting SIMATIC PCS 7 to the SIMATIC IT environment -PCS 7 refers to these stations collectively as "PC stations". Important components in a PCS 7 plant

Configuration of PCS 7 Plant

Introduction & concept of ES (engineering station).

You configure and download all system components of PCS 7 with the engineering station:

-Operator stations, BATCH stations, Route Control stations, automation systems, central and distributed I/O.

-Engineering stations are PCs on which the PCS 7 engineering software is installed for the configuration of a PCS 7 project.

 

PC station for centralized plant-wide engineering.

-Configuration of the hardware

-Configuration of the communications networks

-Configuration of continuous and sequential process. Sequences using

-Standard tools.

-Configuration of discontinuous process sequences (batch Processes) with

-SIMATIC BATCH.

-Configuration of route controls with SIMATIC Route Control.

-Operator control and monitoring strategies.

-Compilation and downloading of all configuration data to all target automation system (AS), operator station (OS), BATCH station (BATCH) and Route Control station.

Maintenance Station

-The maintenance station is based on an operator station (OS). This OS focuses on Plant Asset

-Management" and enables diagnostics and maintenance of the plant.

-When the diagnostics structure is created in the plant hierarchy, an OS is assigned the functions for asset management. The OS functions can be

supplemented with diagnostics functions and program packages for a specific plant.

-Note: The Engineering Station is used as a Maintenance Client. The Maintenance Station accesses SIMATIC PDM when SIMATIC PDM is in use.

-PC station for diagnostics of all PCS 7 components. The diagnostic status is represented by hierarchically structured diagnostic pictures and communicated to the user in diagnostic messages.

-The maintenance station can be designed as a single-station or multiple-station system. The maintenance station (in the single station) or the MS client (multiple-station system) is preferably operated on an engineering station.

Operator station

-The operator station is used to operate and monitor the PCS 7 system in process mode.

-You connect the operator station to the plant bus to enable the required data communication with the automation system.

- Operator stations are PCs on which the PCS 7 OS software is installed.

-The operator station can be designed as a single-station system for smaller plants and less stringent requirements.

- In larger plants with more stringent requirements, the OS can be designed as a multiple-station system with OS servers and OS clients.

-PC station with human-machine interface for operating and monitoring of your PCS 7 plant in process mode.

-The operator station can be designed as a single-station system or multiple-station system.

 

 

Route control station

 -PC station for operation and monitoring of route controls for transporting materials

 -The route control station can be designed as a single-station system or multiple-station system.

Archive servers

- A PC station can be used as external archive server (Process Historian or central archive server CAS). This archive server is a node on the terminal bus. 

Automation station

The automation station carries out the following tasks:

- It registers and processes process variables from the connected central and distributed I/O and outputs control information and set points to the process.

- It supplies the operator station with the data for visualization.

- It registers actions on the operator station and forwards them to the process.

OS Server and OS Client

OS server

An OS server is connected to the automation systems and receives the process data. An OS server can have operator control and monitoring functionality only if a maximum of four OS clients access this OS server. By using more than one OS server, you have the option of distributing data over multiple OS servers. For example, for a large plant, you can store a plant unit on each OS server

The advantages of distributed systems are:

- Good scalability

- Isolation of plant units  

- Higher availability as a result of good scalability and isolation of plant units. PCS 7 supports simultaneous access of an OS server to several other OS servers (Server-Server communication).

OS client

OS clients are used in process mode for operator control and monitoring. OS clients access the data of the OS server, visualize this data and allow operators to control the process. Data from several OS servers is displayed in a process picture that is displayed on the OS client.

You can connect up to four process monitors to OS clients. This requires the use of multi-VGA cards.

The Open PCS 7 station is a PC on which servers for OPC or for OLE DB are installed. The architecture of the Open PCS 7 station is variable and can be flexibly adapted to a variety of plant sizes and requirements.

The Open PCS 7 station performs the following tasks

- It provides the PCS 7 data of the automation process via the OPC or OLE DB interface.

- It allows the client applications (OPC or OLE DB) to access the provided PCS 7 data.

- The Open PCS 7 station is connected to the terminal bus of the PCS 7 plant.

- In process mode, the Open PCS 7 station communicates with the automation systems via the operator station (OS server).

What is a PCS 7 Project?

Among other things, a PCS 7 project includes the following objects:

- Hardware configuration

- Blocks

- CFC and SFC charts

These objects always are always included – regardless of the number of operator stations, modules, and networking.

What Belongs to PCS 7?

The project is created with the Engineering System, generally abbreviated to ES. ES consists of various applications. All applications provide you with a graphic user interface for simple control and clear display of your configuration data. When you work through Getting Started, you will get to know the following applications:

SIMATIC Manager – the central application providing you with access to all other applications that you use to create a PCS 7 project. The SIMATIC Manager is the starting point for creating your entire project.

HW Configuration – configuration of the entire hardware of a system, for example CPUs, power supply, communications processors.

CFC and SFC Editor – for creating CFC charts and sequential controls

PCS 7 OS with various editors – for creating the OS configuration