Automation Lecture 6

8/13/2019 Automation Lecture 6

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Automation Lecture 6.


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1. Generation Control systems

Controller

Process

SensorsActuators

Field

Central Control System


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2. Generation Control Systems

Controller

Process

SensorsActuators

Field


Standard Signals

Analog: 0-20mA

Analog: 4-20mA

Analog: 0-10V

Digital: 0, 24V


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3. Generation Control Systems

Process


Field Standard SignalsAnalog: 0-20mA

Analog: 4-20mA

Analog: 0-10V

Digital: 0, 24V

SensorsActuators

Process Control Station

A/D D/A

OPERATORTREND, Logging


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4. Generation Process Control

Systems


Standard SignalsAnalog: 0-20mA

Analog: 4-20mA

Analog: 0-10V

Digital: 0, 24V

Sensors

Process

A/D

Actuators


D/A

Actuators

Standard SignalsAnalog: 0-20mA

Analog: 4-20mA

Analog: 0-10V

Digital: 0, 24V


Sensors


Field

A/D D/A

Interface to Higher

Hierarchy System


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5. Generation Process Control

System

Actuators


Sensors


Process

Sensors


Field


Actuators

Interface to Higher

Hierarchy System

FIELD BUS


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HART

20mA

4mA

t

4mA

20mA

t

Standard 4-20mA analoge signal

HART

FSK (Frequence Shift Keying)

Analoge + Digital

"0" - 2200Hz

"1" - 1200Hz

Upp=1mA


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HART


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ISO/OSI model


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Physical layer

Standard RS232 RS423 RS422 RS485

Mode Grounded Grounded Differential Differential

Maximal client number1 Tr.

1 Rec.

1 Tr.

10 Rec.

1 Tr.

10 Rec.

32 Tr.

32 Rec.

Max cable length ~12 m. ~1000 m. ~1000 m. ~1000 m..

Max data speed 20kb/s 100kb/s 10Mb/s-100Kb/s 10Mb/s-100Kb/s

Max outgoing voltage +/-25V +/-6V -0.25V ; +6V -7V ; +12V

Transmitter voltage

levelsLoaded

+/-5V to

+/-

15V

+/-3.6V +/-2.0V +/-1.5V

Transmitted voltage Unloaded +/-25V +/-6V +/-6V +/-6V

Loaded impedance (Ohms) 3k to 7k >=450 100 54

Receiver voltage level +/-15V +/-12V -10V; +10V -7V ; +12V

Receiver sensity +/-3V +/-200mV +/-200mV +/-200mV


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Full Duplex RS-485


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Half Duplex RS-485


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MODBUS protocol

Modbus is a serial communications protocolpublished by Modiconin 1979

for use with its programmable logic controllers(PLCs). It has become a de

factostandardcommunications protocol in industry, and is now the most

commonly available means of connecting industrial electronicdevices. The

main reasons for the extensive use of Modbus over other communications

protocols are:

- it is openly published and royalty-free

- it can be implemented in days, not months
http://en.wikipedia.org/wiki/Communications_protocolhttp://en.wikipedia.org/wiki/Modiconhttp://en.wikipedia.org/wiki/Programmable_logic_controllerhttp://en.wikipedia.org/wiki/De_factohttp://en.wikipedia.org/wiki/De_factohttp://en.wikipedia.org/wiki/Standardhttp://en.wikipedia.org/wiki/Industryhttp://en.wikipedia.org/wiki/Electronicshttp://en.wikipedia.org/wiki/Electronicshttp://en.wikipedia.org/wiki/Industryhttp://en.wikipedia.org/wiki/Standardhttp://en.wikipedia.org/wiki/De_factohttp://en.wikipedia.org/wiki/De_factohttp://en.wikipedia.org/wiki/Programmable_logic_controllerhttp://en.wikipedia.org/wiki/Modiconhttp://en.wikipedia.org/wiki/Communications_protocol


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Example of MODBUS network

architecture


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Master-Slave protocol

http://www.modbus.org/docs/Modbus_over_serial_line_V1_02.pdf


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MODBUS communication

http://www.modbus.org/docs/Modbus_Application_Protocol_V1_1b.pdf


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MODBUS Transaction



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http://www.sea.siemens.com/step/downloads.html


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Increased plant availability

Hot swapping

In the event of a fault, electronic modules areeasily replaced during operation with the

equipment live (hot swapping).The station

remains functional, and the plant therefore

remains available there is no need for costly

shutting down and starting up of the plant.

While the components are being replaced, thewiring remains intact. Coding of the modules

prevents mistakes when replacing them.

Redundancy

To increase plant availability, the system offers a

system-wide redundancy concept. ET 200 I/Odevices are connected with two interface

modules to the two PROFIBUS lines of a high-

availability automation system. If the active

system fails, the standby system takes over the

functions immediately so that standstill can be

avoided.

Automation Lecture 6

Documents

Transcript of Automation Lecture 6