Industrial Networks

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Summary

Introduction to Industrial Communication

Modbus

CANopen

Ethernet Modbus TCP/IP

EtherNet / IP

2

EtherNet / IP

Profibus

Introduction to Industrial

Communication

What is Communication?

4

Smoke signals Telegraph Digital exchange

Why Communication?

Same Radio models (ID)

Transmit by Air

Same Frequency

5

Radio must be Switched on

Same Language

Do not speak in the same time

Acknowledge the message

Items Mandatory to Communicate

Transmitter Receiver

Medium

Language

Translator

Collision

6

Transmitter Receiver

Id = 3

Id = 4

Id = 2

Acknowledgement

Industrial Communication

Serial link

Digital data

01

7

Wired Solution

Analogue speed

command 0-10 V

Communication Solution

Industrial Communication (Cont.)

Diagnostic

8

Easiness of Replacement

OSI Model for Machine Communication

Layer Train Example Machine

Application Same Language? Protocol

Presentation Radio AM or FM? Format Conversion

9

Session Radio ON? History + Organisation

Transport Message Received?End to End Routing

Control

Network Same Frequency? Address

Data Link Who speaks first? Access Control

Physical Air (radio waves) Coverage? Hardware

OSI Model: Encapsulation Principle

Clothes Suitcase Name Tag Dest. tag Airplane

10

Market Requirements

1 s

1

minute

1 Kb

1 Mb Information System

PC - Servers

Level 3Company

Data bus

Level 2Process Production management

Files in N x seconds

11

RESPONSE

TIME

REQUIRED

1 ms

1 s

1 bit

AMOUNT

OF DATA TO BE

TRANSMITTED

Process

Field bus

Production managementPLCs - GUI

Level 1Machines

Device bus

Monitoring and controlVariable speed drives

Automation islands

Reaction detection

Digital actuators sensors

Level 0Components

Sensor busN x bits in N x ms

N x words in N x 10 ms

N x 10 words in N x 100 ms

Positioning of The Main NetworksR

e

s

p

o

n

s

e

t

i

m

e

Machine

CANopen*

Fipio

Sercos,,

Sensor

AS-i*

Interbus S

Process

Fipway

DeviceNet

12

Exchange volume

Management

Fipio

1 bit byte K byte M byte

Profibus FMS

Fipway

Ethernet TCP/IP*

Modbus +

Profibus DP / PA

Modbus*

Choice of a Network

APPLICATION

LAYER 7

Medium access: master-slave, token ring, random access?

Language: Modbus, CANopen?Process data: Client-server, producer-consumercontent, periodicity?

Service data: Accessible variables, max. size?

13

Medium: twisted pair, coaxial cable, optical fibre?

LINK

LAYER

2

1PHYSICAL

LAYER Topology: bus, star, tree, grid?

Max. no. of devices: 2, 31, 63, 127?

Max. distance between devices: 100 m, 1 km, 15 km?

Medium access: master-slave, token ring, random access?

Addressing: address 1, 5, general distribution?

Transmission control: parity check, CRC, delimiters?

Flow control: NACK, XON-XOFF, inhibit time?

Terminology

Half / Full duplex

14

PLC I/OCOLLISION

PLC I/O

TRANSMIT

TRANSMIT

Terminology (Cont.)

Kbps

= Kilobits (1024 bits) per second (binary) but

kbps

= kilobits (1000 bits) per second (decimal)

KBps

15

KBps

= Kilobytes (1024 bytes) per second (binary)

kBps

= kilobytes (1000 bytes) per second (decimal)

Terminology (Cont.)

Differential Signal

16

Terminology (Cont.)

Cyclic Exchange / Implicit Exchange

Process data / high priority

Data exchanged between device periodically on demand.

Managed automatically / defined in configuration

17

Acyclic Exchange / Explicit Exchange

Configuration or diagnostic data / low priority

Data exchanged only on request

Managed by the application / request to be programmed

Medium & Physical Layer

18

Medium & Physical Layer

Cabled link

Fiber optic link

19

Radio links

Common Medium

Coaxial cable

The coaxial cable has excellent electrical

properties and is suitable for high speed

transmission.

Twisted pair(s) wires

Easy to install, and the least expensive.

Optical fiber

Cost of

the

medium

Low

20

The choice of the MEDIUM affects the transmission quality :

Speed

Length of the bus

Electromagnetic immunity

This is suitable for use in harsh industrial

environments. The transmission is reliable over long

distances. High

Examples of Physical Layer

RS232

Half or Full duplex, point-to-point link.

Max. length : 15 m, Max. speed : 20 Kbps

Using example : Connecting a device to a PC

RS422 Full-duplex (simultaneous bidirectional) multi-drop bus on 4

21

Full-duplex (simultaneous bidirectional) multi-drop bus on 4 wires.

Differential signal : good immunity to interference

Max. length : 1000 m at 100 Kbps, Max. speed : 12 Mbit/s

Maximum devices on the bus : 32

Using example : Interbus S fieldbus

RS485

Half-duplex (alternate bidirectional) multi-drop bus on 2 wires.

Same electrical characteristics as RS422A but on 2 wires.

Using example : Modbus, Profibus fieldbus

POINT-TO-POINT

GRIDRING

Example: PC - PLC

console connector link

Example: CANopen,

DeviceNet, Profibus-DP,

FIPIO, Modbus RS485

Various topologies

BUSBypass Chaining

Line termination resistors

22

STAR TREE

GRID

Example : Devices connected over

Ethernet via a HUB

Example: Interbus S Example:

Internet network

via routers

Example:

Intranet network

via hubs and switches

Data Link Layer

23

Master-Slave system

The master grants access to the medium

The slave can access the medium after being polled by the master

Polling

Do you have anything to say?

24

Response

Nothing to declare!

Used by Asi, FIPIO, Modbus, Profibus-DP and Uni-Telway

Can be used on CANopen and DeviceNet (by configuration)

MASTER SLAVE

Token Ring

Ring: the members of a ring are authorized to send data upon receipt of

the token.

Token: a group of bits passed from one node to another in ascending

order of address.

Address 2

25

Address 1 Address 3

Address 4

Used by Modbus Plus / Profibus in Multi Master mode

Data can be transmitted as soon as a silence is detected.

2 types of collision

Each device "listens" whilst it transmits

If the data received is different from the data sent, a collision occurs

Random access

26

2 types of collision

destructive

non-destructive

Random access with destructive collisions

Stop Stop

Waiting time 10sWaiting time 15s

27

Waiting time 5s

Random access with destructive collisions

Step-by-step operation in the event of a collision:

any messages in the course of transmission are stopped

a scrambling frame is sent: the frame is lost

a random wait time is observed

the message is resent

28

Stop

CSMA-CD = Carrier Sense Multiple Access - Collision Detection

Principle used by Ethernet and known as CSMA-CD

Random access with non-destructive

collisions

Stop

Dominant Recessive

29

Dominant Recessive

Dominant Recessive

Random access with non-destructive

collisions

The message remains valid, due to a system of dominant and recessive bits

the device with the lower priority stops its transmission (recessive bit)

the device with the higher priority completes its transmission

the device with the lower priority tries to send its message again as soon

as the medium is free

30

as the medium is free

CSMA-CA = Carrier Sense Multiple Access - Collision Avoidance

Principle used by CANopen and DeviceNet and known as CSMA-CA

StopDominant Recessive

Network, Transport, Session &

Presentation Layers

31

Network & Transport

Network Layer

Defines how to route a message

32

Transport Layer

Responsible for delivery the message

Ethernet Chapter

Session & Presentation

Session Layer

Establish or close a connection remotely

33

Presentation Layer

Present the message on a specific format

Wikipedia

Application Layer

34

Client Server Model

The CLIENT is an entity requesting a service on the network

The SERVER is the entity which responds to a request from a client

Request

35

Response

No problem, here is the whole file!

Please, can you send me the

configuration of motor starter no. 3 ?

SERVERCLIENT

Producer Consumer Model

The PRODUCER is a single entity which produces information.

The CONSUMER is an entity which use it (several entities can use the

same information).

I m going to miss

my train !!!

36

CONSUMER N1

my train !!!

CONSUMER N2

Let s go to see

a movie...

PRODUCER

It s 6 pm

Errors Detection

Undetected Errors Are Disturbing

Many Systems / Algorithms to Detect Errors

Parity bits, CRC checks, stuffing bits, timeouts, ACK slotsI

37

Performance Measurement

Hamming distance