Conversion of Fieldbusses regarding
Industrial Internet of Things

Ludwig Leurs
Bosch Rexroth AG
October 14, 2015

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

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History of Fieldbusses

1980s
•

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

Data exchange between automation controllers•

Synchronized motion systems

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Serial connection

Parallel bus
Parallel bus

IO Rack 4
IO Rack 5

Cabinet 2

Parallel bus
Parallel bus

IO Rack 1
IO Rack 2

Cabinet 1

PLC

IO Rack 3

Central I/O

N -times
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4I/O via Fieldbus

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DeviceNet••

Introduced in 1995Based on CAN (ISO11898)– widely used in vehicles•

Variety of application–––––••

Master / Slave
Client / ServerPeer to PeerCyclic, Change of State
Unicast or Multicast

Object oriented design
Routing and bridging

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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 C2CPC used for HMI and control  Ethernet, TCP/IP

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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

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8Servo drive control loops
Position control interface(Standard interface forSERCOS)

Xcmd

Classical analog speed control Momentum/current control
interface ±10V
(used for non-cartesian systems,e.g. robotics)

ncmd+-Position control
loop+-Speed control
loop+-Momentum /current control
loop

U,I
indirectXcrnt

directfeedback

ncrnt
d/dt

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9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

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10Differences in Application Properties•••

Different usage  different properties
Offline configuration  EDS
Machine only working with all drives  error if one is missing
I/O
Offline configuration

C2CX

Online configuration
Config at connection

XXX

Cycle time

5-10ms5-100ms0.5-4ms

Synchronization< ±5%-<1µsBrowse
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X
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11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

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12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)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.

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13

Real Time Behavior (2)Software Architecture

Performance1

Real Time Class

Besteffort

Real Time

2
Besteffort

Real Time

3
Besteffort

Real Time

TCP/UDPTCP/UDPIP

IP

Prioritizing

Scheduling

Ethernet MAC

Ethernet MAC

Ethernet MAC

e.g. Modbus, FF HSEProfinet RT, EtherNet/IP

Profinet IRT, Sercos,
PowerLink, EtherCAT

TCP/UDPIP

Adapted from: J. Jasperneite, FH Lemgo
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.

Market Requirements
Ford Motor Company

Future: Individual products
in mass production

High variation of products, minimum buffers
ToyotaMinimum product variation

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SmartFactory Demo Line•••Product: card holder
Product contains
individualmanufacturing steps
and quality dataPlan to use Machine
Data Model of ODVA
Machinery SIG

6/23/2015 | Ludwig Leurs | © Bosch Rexroth AG 2015. All rights reserved, also regarding any disposal, exploitation, reproduction, editing, distribution, as well as in the eventof applications for industrial property rights.

1616

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

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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

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Cloudbrowse
file://host/dev.eds

S-0-0017

18

TSN Standards Overview••

Set of Standards
Time Synchronization

1588– 1588, 802.1AS, 801.2ASrev•Latency reduction

Qat

AS
Rev

1722

– 802.1Qbu, 802.3br– 802.1AB (LLDP)•AS1733

Qcc

Qca

Scheduling traffic

3br

TSNQci– 802.1Qbv•Qbu

Redundancy

QAB– 802.1CB

QchQav

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CB

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Qbv
Legend:TSN
AVB
EthernetTransport

1919

Time Synchronization
••

•

•

Nearly all systems use somevariant of IEEE1588
Transparent clocks have been
introduced to minimize degradingof accuracy over hop count
Redundancy issues have beensolved by sophisticated methods

GrandMasterTransp.
ClockTransp.
Clock

Ord.
Clock

Daisy chain degrades accuracy
 Optimum is star topologytOnly Sercos uses
synchronization by telegram
MasterNode

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2 PortNode2 Port
Node2 Port
Node20Latency Reduction – Frame Preemption
••

•

•

Long frames can‘t be interrupted in
traditional Ethernet
Qbu (Frame Preemption) and 3br(Interspersing Express Traffic)
solve thisMaximum 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

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12…

2…

21

2…

3…

3

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Latency Reduction – Scheduled Traffic•Problem: large number of hops
– Scheduling can reduce latency
significantly•

IEEE802.1Qbv Time aware
shaper– Block non-express traffic in theguard window immediately
before cycle start•

Queue:
time criticaltraffic

Queue:
best effort traffic

Queue:
…
…

TAS

CBS

CBS

CBS

Transmission
Gate Open

Transmission
Gate Close

Transmission
Gate Close

Transmission
Gate Close

Gate control list
T01: OCCC
T02: COCC
T03:.COOO….
T79: Repeat

Transmission selection

Only in large networks– Probably not in EtherNet/IP– Needed in Sercos

Queue: rate
constrained
trafficCycle start112

Non express traffic blocked

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Redundancy••

Industrial networks support
redundancy alreadyChange to 802.1CB would
introduce different procedures

EtherNet/IP
Beaconprotocol– Incompatibilities•

No need, if no requirement fromapplication
SercosMasterprimary channel

P1

P2

P1 = Port1P2 = Port2

P1

P2

P2

secondary channel

P1

P2

slave 1
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slave 2

P1

slave 323

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 insignificantlyTransmission time1)
Delay per hop2)
1)2)

Packet size

100Mbit/s

1 Gbit/s

64

6.7µs

0.67µs

1518

123µs

12.3µs

1.5µs

1.5µs

Topology matters!

Including Start of Frame and Inter Packet Gap
1 µs node delay and 0.5µs accounting for 100 m cable length

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100Mbit/s versus 1Gbit/s – cut through•Total delay with Cut through– Transmission time important at
100Mbit/s– Node delay dominant at 1Gbit/st D  t DN  n  ttr

300µst DN : Node Delay250

ttr : transmission time
200
100M-64B

150

1000M-64B
100M-1518B

100

1000M-1518B
500110 20 30 40 50 60 70 80 90 100
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100Mbit/s versus 1Gbit/s – store & forward•Total delay with store & forward– 100Mbit/s:

14,000.0

t D  t DN  n  ttr

12,000.0

t DN : Node Delay

10,000.0

ttr : transmission timeµs• Transmission time dominant forlarge packets• Large number of hops lead tolarge delay• Not useful for closed loop control• But for small packets only systems
may be acceptable• TSN Frame preemption would behelpful8,000.0

1000M64B

6,000.0

100M1518B
4,000.0

1000M1518B

2,000.00.0– 1Gbit/s

1• Small packets: node delay andtransmission time in same range
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100M64B

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10 20 30 40 50 60 70 80 90 100
Number of Hops

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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
helpfult D  t DN  n  ttr

300µs

t DN : Node Delay250

ttr : transmission time200

100M64B

150

1000M64B
100M1518B

100

1000M1518B
50– 1Gbit/s• Small packets: node delay andtransmission time in same range

01

10
Number of Hops

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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)

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THANK YOU