2015_ODVA_Conference_Leurs-Conversion-of-Fieldbusses-FINAL ...

Conversion of Fieldbusses regarding Industrial Internet of Things

Ludwig Leurs

Bosch Rexroth AG

October 14, 2015

2

Overview

• Development of fieldbusses in Factory Automation

• Requirements from Industrial Internet of Things / Industrie 4.0

• Future impact of Time Sensitive Networks on Industrial Ethernet

Technical Track 2015 Industry Conference & 17th Annual Meeting www.odva.org

© 2015 ODVA, Inc. All rights reserved. 2

3

History of Fieldbusses

1980s

• Replacement of hardwired I/O connection to reduce wiring cost

• Data exchange between automation controllers

• Synchronized motion systems


© 2015 ODVA, Inc. All rights reserved.

4

Central I/O



PL

CIO

Ra

ck 1

IO R

ack 2

Pa

ralle

l bus

Pa

ralle

l bus

Cab

ine

t1

IO R

ack 4

IO R

ack 5

Para

llel bus

Pa

ralle

l bus

Cab

ine

t2

IO R

ack 3

Serial connection

N -times

I/O via Fieldbus



6

DeviceNet

• Introduced in 1995

• Based on CAN (ISO11898)

– widely used in vehicles

• Variety of application

– Master / Slave

– Client / Server

– Peer to Peer

– Cyclic, Change of State

– Unicast or Multicast

• Object oriented design

• Routing and bridging



7

Controller to Controller Communication

• Automation driven by automotive industries

• The 1980s: CIM, MAP/MMS driven by GM, initial point of Industrie 4.0

• Vertical integration

• Profibus/FMS was defined as a subset of MMS, main use C2C

• PC used for HMI and control Ethernet, TCP/IP



8

CNC, RC and Motion Control

• First applied in machine tools

• High precision and fast control loops needed

– Local control loops preferred

– Distribution of control loops depends on application

• Commissioning mostly online



9

Servo drive control loops



Momentum / current control

loop

Speed control loop

Position control loop

U,IXcmd

Xcrnt

ncmd

ncrnt

d/dt

indirect direct feedback

Classical analog speed control interface ±10V

Position control interface(Standard interface forSERCOS)

Momentum/current control(used for non-cartesian systems, e.g. robotics)

+

-

+

-

+

-

10

CNC, RC and Motion Control

• First applied in machine tools

• High precision and fast control loops needed

– local control loops preferred

– Distribution of control loops depends on application

• Commissioning mostly online

• First digital interface: Sercos

– Fiber optics for EMC

– TDMA for real time high precision timing

– Initially only drives

– Specialized for synchronized motion



11

Differences in Application Properties

• Different usage different properties

• Offline configuration EDS

• Machine only working with all drives error if one is missing



I/O C2C Motion

Offline configuration X

Online configuration X

Config at connection X X

Cycle time 5-10ms 5-100ms 0.5-4ms

Synchronization < ±5% - <1µs

Browse X

12

Migration to Ethernet

• Reasons and requirements

– Data rate insufficient in fieldbusses

– Eliminate separate interface for commissioning

– Enable IT integration into devices

• Web server

– Diagnostics

– Change settings

• Firmware download

• SNMP

• How to become Ethernet deterministic



13

Real Time Behavior (1)

• Traditional Ethernet using CSMA/CD is not deterministic

– Collision is detected and packets are repeated after random time

– But can be made deterministic by a Master/Slave MAC layer (PowerLink)

• Switched Ethernet and packet prioritization achieves soft real time behavior

– Packet delay up to 122 µs per hop

– Still danger of overload and switches not supporting enough priorities

– Not suitable for synchronized motion

– Synchronized motion can be achieved using synchronization with IEEE1588

• Ultra low latency and Ethernet

– Scheduled transfer (TDMA) and multi-device packets (Sercos, Profinet IRT)

– Future: Time Sensitive Networks (TSN)

13Electric Drives and Controls | 20.06.2012 | DC-IA/PJ-ETH | © Bosch Rexroth AG 2012. Alle Rechte vorbehalten, auch bzgl. jeder Verfügung, Verwertung, Reproduktion, Bearbeitung, Weitergabe sowie für den Fall von Schutzrechtsanmeldungen.

Electric Drives and Controls | 20.06.2012 | DC-IA/PJ-ETH | © Bosch Rexroth AG 2012. Alle Rechte vorbehalten, auch bzgl. jeder Verfügung, Verwertung, Reproduktion, Bearbeitung, Weitergabe sowie für den Fall von Schutzrechtsanmeldungen.

Adapted from: J. Jasperneite, FH Lemgo

Real Time Behavior (2)

Software Architecture

Real Time Class

Best-effort

Real Time

TCP/UDP

IP

Ethernet MAC

1

e.g. Modbus, FF HSE

Best-effort

Real Time

TCP/UDP

IP

Ethernet MAC

2

Profinet RT, EtherNet/IP

Prioritizing

Best-effort

Real Time

TCP/UDP

IP

Ethernet MAC

3

Profinet IRT, Sercos,

PowerLink, EtherCAT

Scheduling

Performance

Market Requirements

15Technical Track 2015 Industry Conference & 17th Annual Meeting www.odva.org


Ford Motor Company

Minimum product variation

High variation of products, minimum buffers

Toyota

Future: Individual products in mass production

16

SmartFactory Demo Line• Product: card holder

• Product contains

individual

manufacturing steps

and quality data

• Plan to use Machine

Data Model of ODVA

Machinery SIG

166/23/2015 | Ludwig Leurs | © Bosch Rexroth AG 2015. All rights reserved, also regarding any disposal, exploitation, reproduction, editing, distribution, as well as in the event

of applications for industrial property rights.

17

Ubiquitous availability of information

• Every information at any place at any time

• Wireless is the key

– Already available via mobile devices

– In some applications also at device level

• CIP is ready

– Objects and services

– Bridging and routing

– Future extension

• DeviceNet of Things

• EtherNet/IP in resource constrained devices

• I/O-Link integration



18

Discovery Service

• IIoT needs information to be found online

• OPC (and OPC UA) offers a browse service

• Industrial systems based on offline configuration

EDS files

• Systems originating from online configuration

built in object directory, e.g. Sercos: S-0-0017,

Parameter structure contains units, names, data

type, …

• Solution: link to EDS from device



Cloud

file://host/dev.eds

S-0-0017

browse

19

TSN Standards Overview

• Set of Standards

• Time Synchronization

– 1588, 802.1AS, 801.2ASrev

• Latency reduction

– 802.1Qbu, 802.3br

– 802.1AB (LLDP)

• Scheduling traffic

– 802.1Qbv

• Redundancy

– 802.1CB


© 2015 ODVA, Inc. All rights reserved. 19

CB

QbvQ

3brTSN

Qbu

Qci

Qca

Qcc

ASRev1722

Qav

Qch

AS1733

Qat

1588

Legend:TSNAVBEthernetTransport

AB

20

Time Synchronization

• Nearly all systems use some

variant of IEEE1588

• Transparent clocks have been

introduced to minimize degrading

of accuracy over hop count

• Redundancy issues have been

solved by sophisticated methods

• Only Sercos uses

synchronization by telegram



MasterNode

2 PortNode

2 PortNode

2 PortNode

t

Grand-Master

Transp. Clock

Transp. Clock

Ord. Clock

Daisy chain degrades accuracy

Optimum is star topology

21

Latency Reduction – Frame Preemption

• Long frames can‘t be interrupted in

traditional Ethernet

• Qbu (Frame Preemption) and 3br

(Interspersing Express Traffic)

solve this

• Maximum delay by low priority

traffic can be reduced from 123µs

to 12µs @100Mbit/s

• But this still allows this delay to be

introduced at each hop



1 2 … 3 3…

…1 2 2 2…

22

Latency Reduction – Scheduled Traffic

• Problem: large number of hops

– Scheduling can reduce latency

significantly

• IEEE802.1Qbv Time aware

shaper

– Block non-express traffic in the

guard window immediately

before cycle start

• Only in large networks

– Probably not in EtherNet/IP

– Needed in Sercos



Queue: time critical

traffic

Queue: rate constrained

traffic

Queue:best effort traffic

Queue:……

Transmission Gate

Transmission Gate

Transmission Gate

Transmission Gate

Gate control list

T01: OCCCT02: COCCT03:.COOO….T79: RepeatTAS CBS CBS CBS

Transmission selection

Open Close Close Close

Cycle start

Non express traffic blocked

1 1 2

23

Redundancy

• Industrial networks support

redundancy already

• Change to 802.1CB would

introduce different procedures

– Incompatibilities

• No need, if no requirement from

application



slave 1

primary channel

Master

secondary channel

slave 2 slave 3

P1 P2 P1 P2 P2 P1

P1 P2 P1 = Port1

P2 = Port2

Beacon

protocol

EtherNet/IP

Sercos

24

100Mbit/s versus 1Gbit/s

• What happens going from 100 Mbit/s to 1Gbit/s?

– Transmission speed increases by factor 10

– Propagation delay stays constant (no increase in speed of light)

– Signal conversion delay decreases insignificantly



Packet size 100 Mbit/s

1 Gbit/s

Transmission time1) 64 6.7µs 0.67µs

1518 123µs 12.3µs

Delay per hop2) 1.5µs 1.5µs

1) Including Start of Frame and Inter Packet Gap

2) 1 µs node delay and 0.5µs accounting for 100 m cable length

Topology matters!

25

100Mbit/s versus 1Gbit/s – cut through

• Total delay with Cut through

– Transmission time important at

100Mbit/s

– Node delay dominant at 1Gbit/s



0

50

100

150

200

250

300

1 10 20 30 40 50 60 70 80 90 100

µs

Number of Hops

100M-64B

1000M-64B

100M-1518B

1000M-1518B

trDND tntt

on timetransmissi:trt

Delay Node:DNt

26

100Mbit/s versus 1Gbit/s – store & forward

• Total delay with store & forward

– 100Mbit/s:

• Transmission time dominant for

large packets

• Large number of hops lead to

large delay

• Not useful for closed loop control

• But for small packets only systems

may be acceptable

• TSN Frame preemption would be

helpful

– 1Gbit/s

• Small packets: node delay and

transmission time in same range



trDND tntt


Delay Node:DNt

0.0

2,000.0

4,000.0

6,000.0

8,000.0

10,000.0

12,000.0

14,000.0

1 10 20 30 40 50 60 70 80 90 100

µs

Number of Hops

100M64B

1000M64B

100M1518B

1000M1518B

27

100Mbit/s versus 1Gbit/s – store & forward

• Total delay with store & forward

– Low number of hops

– 100Mbit/s:

• Transmission time still important

• closed loop control

• But for small packets only systems

may be acceptable

• TSN Frame preemption would be

helpful

– 1Gbit/s

• Small packets: node delay and

transmission time in same range



trDND tntt


Delay Node:DNt

0

50

100

150

200

250

300

1 10

µs

Number of Hops

100M64B

1000M64B

100M1518B

1000M1518B

28

Summary

• Automation technology developed in several application fields

• Ethernet was introduced for transmission rate and IT connectivity

• ODVA uses COTS technology and supports internetworking in its

specification

• CIP is ready for the Industrial Internet of Things

• Discovery service could be added

• When TSN becomes available EtherNet/IP could be easier to apply in time

critical applications in the presence of IT traffic

• The formerly separated application fields can be merged into one network

(this is already true for EtherNet/IP)



THANK YOU

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