Integrated Motion On EtherNet/IP: Maximizing Network Performance

Copyright © 2014 Rockwell Automation, Inc. All Rights Reserved.

PUBLIC INFORMATION

AD19 - Integrated Motion On EtherNet/IP: Maximizing Machine Performance


This session is focused at helping designers of EtherNet/IP based motion systems to: Understand the fundamental principles behind the core

technology (CIP Motion) and its relationship to time Discover how the use of time in the architecture allows for

determinism and provides a platform for high performance control Gain insight into infrastructure selection, network arrangement

and how devices with ‘CIP Sync’ technology can also be applied to a high performance, deterministic control solution

Session Description


Keeping it all in perspective

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This presentation focuses on the fundamentals of CIP Motion and CIP Sync technologies and the relationship of time and position in the system. It correlates these basic parameters of a CIP Motion architecture against the network infrastructure and helps the designer to understand how to apply best practices for an infrastructure which communicates the proper timing and positioning information in these systems.

However given this, the variations introduced by networking infrastructure are measured in nanoseconds and microseconds. Fluctuations introduced by the network are usually negligible compared to other boundaries in the system:

Compliance and backlashMechanical system time constantsSystem Tuning


EtherNet/IP - Enabling/DrivingConvergence of Control and Information

4

Industrial Network Convergence

Converged Plantwide EtherNet/IPIndustrial Network Model

Corporate Network

Sensors and otherInput/Output Devices

Motors, DrivesActuators

SupervisoryControl

Robotics

Back-Office Mainframes andServers (ERP, MES, etc.)

OfficeApplications,Internetworking,Data Servers,Storage

Human MachineInterface (HMI)

SafetyController

Traditional – 3 TierIndustrial Network Model

Corporate Network

Sensors and otherInput/Output Devices

Controller

Motors, DrivesActuatorsRobotics

Back-Office Mainframes andServers (ERP, MES, etc.)

OfficeApplications,Internetworking,Data Servers,Storage

Control NetworkGateway

Human MachineInterface (HMI)

SupervisoryControl

Camera

Phone

Industrial NetworkIndustrial Networks

SafetyI/OI/O

Controller


CIP Motion coordinates devices in a manner that’s similar to our own methods for coordinating meetings and events All members (devices) have clocks

to compare time to an absolute base and scale

A destination (position) is targeted for the event

A time (timestamp) is set for when the event shall occur

A message is sent to each member (device) to meet at the given place at the pre-determined time Not all messages might arrive at

precisely the same time!

Birthday Party!Cafeteria12:00 pm

Fundamental Principal of CIP Motion Control


Cafeteria

CIP Motion coordinates devices in a manner that’s similar to our own methods for coordinating meetings and events All members (devices) have clocks to

compare time to an absolute base and scale



A message is sent to each member (device) to meet at the given place at the pre-determined time Not all messages might arrive at

precisely the same time! But all members arrive in the proper

position at the proper time for the event to take place!

Fundamental Principal of CIP Motion Control


Motion Task

Target Time =Tctr0 + 2*CUP

Tctr0

Servo Update Period

Course Update Period (CUP)

Delivering Command Position with Time Stamp allows Drive to Compute a Trajectory to hit the Command Position at the Target Time.

Tctr1 Tctr2

Drive Task

Fine Interpolation Polynomial Target Time

Target CommandPosition

Last Target Time

Last CommandPosition

Motion Task

Drive Task

Controller

Drive

AxisRotation

Command Position Targeting Using Time Stamp

KPI-1 = Tracking Error = Command Position (N-2) – Actual Position (N)


How is time synchronized in the system?Precision Time Protocol (PTP) Overview

Creates a master/slave hierarchy of clocks in the network

Best Master selection Grandmaster transmits accuracy

properties with Announce msg Slaves pick best master

Synchronization timing messages Between master and slave Frequency Synchronization

Sync, Followup Msgs Phase / Delay Measurements

Slave to Master Delay_Req, Delay_Resp Msgs

Master Clock Slave ClockTS

TS

Delay = (D1 + D2) / 2 time

TS

TS

TS

TS

TS Time Stamp

D1

D2


If clocks are off, members don’t know that their clocks are different from others against which they are coordinating All members (devices) continue

to compare time to an absolute base and time scale



A message is sent to each member (device) to meet at the given place at the pre-determined time

Birthday Party!Cafeteria12:00 pm

What happens if the clocks are off?


Cafeteria

If clocks are off, members don’t know that their clocks are different from others against which they are coordinating All members (devices) continue to

compare time to an absolute base and time scale.



A message is sent to each member (device) to meet at the given place at the pre-determined time Members will arrive at the right

place…. But at the wrong time…. ….this results in positioning error…

PositioningError

12:00 12:00

11:50 11:50


Copyright © 2014 Rockwell Automation, Inc. All Rights Reserved. 11

ReferenceAxis Clock

= 3:00

FollowerAxis Clock

thinks it’s 3:00

Time

Posit

ion

PositionError


KPI-2 = Registration Position Skew


How would clocks become offset?

Network infrastructure is a potential filter to the distribution of time in a system.

Although time is metered precisely from the master clock……it may not be precisely delivered through the infrastructure distribution depending on traffic loading and infrastructure configuration…

3:01 3:02 3:03 3:04 3:05 3:06 3:07 3:08

3:01 3:02 3:03 3:04 3:05 3:06 3:07 3:08

KPI-3 = Registration Time Skew


How would clocks become offset?

13

M

S

Introduction of random, large volumes of data in a non-prioritized manner

Introduction of large packet sizes1500 bytes @ 100MBits/sec = 120 usecs

Non-PTP Enabled Switch


Device Clock Filtering Not user configurable

Topological Arrangement

Time Re-phasing Mechanisms Boundary Clock Transparent Clock

Traffic Prioritization QoS – Quality of Service DSCP - Differentiated Services

Code Point CIP Prioritization (ODVA

Specification) IGMP Snooping

Management of Multi-Cast Traffic

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Typically Managed Switch Other Mechanisms

How do I protect time in the system?


Advantages: Ability to segment network (minimize network latency and jitter) Network diagnostics and security features Some provide security protocols Some run loop prevention protocols Some deliver Quality of Service (QoS) Some multicast management (IGMP) Some support precision time protocol (PTP)

Disadvantages: Higher initial cost than an unmanaged switch Some technical knowledge needed for setup

Managed Switches

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Does this mean I can’t use an unmanaged switch?

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No! You can use an unmanaged switch as long as you understand some key principles….


Advantages: Simplified design and deployment Ideal for small, isolated networks Lower initial investment than a managed switch

Disadvantages: No diagnostics No security No loop prevention No QoS or prioritization of some traffic at the expense of other traffic No PTP or adjustment to time stamp after passing packet No IGMP Snooping capability for multicast traffic management

Unmanaged Switches

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Using Multiple Unmanaged Switches in a Large System…

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Multiple Unmanaged Switches in a Large SystemJitter at 0% Network Loading…

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With no network load, there was little difference between test cases

0

500

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0 2000 4000 6000 8000 10000 12000 14000

Clock Jitter (Nanoseconds)"Golden" Axis (Connected directly w/o switch

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Clock Jitter (Nanoseconds)Axis Switch 1

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Multiple Unmanaged Switches in a Large SystemJitter at 40% Network Loading…

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0200400600800

1000120014001600

0 2000 4000 6000 8000 10000 12000 14000


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0 2000 4000 6000 8000 10000 12000 14000


020406080

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010203040506070

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Multiple Unmanaged Switches in a Large System Jitter at 80% Network Loading…

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0

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Same Test Using PTP Managed SwitchJitter at 80% Network Loading…

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0

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25000

0 2000 4000 6000 8000 10000 12000 14000


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30000

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100001500020000250003000035000

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05000

100001500020000250003000035000

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Copyright © 2014 Rockwell Automation, Inc. All Rights Reserved. 23

16 Axis Star, Linear K6500, Stratix 8000 Switch 16 Axis Star, K350, Stratix 2000 Switch

So what do these numbers really mean?

Average System Clock Jitter (Max) ~ 35 nanoseconds

0.000000035s x 6000 RPM/ 60s/min = 0.0000035 Revs

Note: Sample from Axis 2

Average System Clock Jitter (Max) ~ 1.8 microseconds

0.0000018s x 6000 RPM/ 60s/min = 0.00018Revs

Note: Sample from Axis 1, off switch 1

Multiply your application speed by this value to determine position error due to network jitter


PUBLIC INFORMATION

Maximizing Machine PerformanceTopology Design Considerations


What’s new since last year?

A year’s worth of new testing has been completed The latest products have been tested

3 Key Performance Indicators Tracking Error Registration Time Skew Registration Position Skew

More data to back up our previous recommendations Specific cell-based automation network guidelines intended for

performance


Topology #1Baseline Topology

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Point I/O™ Adapters ArmorBlock™ I/OKinetix® 5500 or

Kinetix 6500 Drives

PowerFlex Drives

PanelView™ Plus

Plant Network

(Any)Switch

CIP Encoders

Metric 0% Load 20% Load 40% Load

Tracking

RegPos

RegTime

CompactLogix™ L36ERM

Switch Topology QoS PTP

Embedded Linear Direct Yes Yes

(16) axes were tested in this topology


Topology #2: Linear InterposingUnmanaged (No QoS, No PTP)

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CMX L36ERM

Plant Network

Stratix 2000

PanelView Plus

Point I/O Adapters ArmorBlock I/OKinetix 5500 or

Kinetix 6500 Drives

CIP Encoders

PowerFlex® Drives


Tracking

RegPos

RegTime


Stratix 2000 Star/Linear No No



Topology #2a: Linear DirectUnmanaged (QoS, PTP in place)

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Plant Network

Stratix 2000

PanelView Plus


Kinetix 6500 Drives

CIP Encoders

PowerFlex Drives

CMX L36ERM





Tracking

RegPos

RegTime


Topology #3: Linear InterposingLow-Level Managed (No QoS, No PTP)

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PanelView Plus

Plant Network

Stratix 5700 Lite


Kinetix 6500 Drives

PowerFlex Drives

CMX L36ERM


Stratix 5700 Lite Star/Linear No No

CIP Encoders



Tracking

RegPos

RegTime


Topology #3a: Linear DirectLow-Level Managed (QoS, PTP in place)

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PanelView Plus

Plant Network

Stratix5700™

Lite


Kinetix 6500 Drives

PowerFlex Drives

CIP Encoders

CMX L36ERM





Tracking

RegPos

RegTime


Topology #4: Linear InterposingMid-Level Managed (QoS, No PTP)

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PanelView Plus

Plant Network


Kinetix 6500 Drives

PowerFlex Drives

Stratix 5700 Full

ControlLogix L36ERM


Tracking

RegPos

RegTime


Stratix 5700 Full Star/Linear Yes No

(16) axes were tested in this topology CIP

Encoders


Topology #4a: Linear DirectMid-Level Managed (QoS, PTP in place)

36

PanelView Plus

Plant Network

Point I/O AdaptersKinetix 5500 or

Kinetix 6500 Drives

PowerFlex Drives

Stratix 5700 Full

CIP Encoders

ArmorBlock I/O

ControlLogix L36ERM





Tracking

RegPos

RegTime


Topology #5: Linear InterposingFully Managed (QoS and PTP)

37

PanelView Plus

Plant Network

Stratix 5700

Full/PTP

PowerFlex Drives

Point I/O AdaptersKinetix 5500 or

Kinetix 6500 Drives

CIP Encoders

ArmorBlock I/O

CMX L36ERM


Stratix 5700 Full/PTP Star/Linear Yes Yes



Tracking

RegPos

RegTime


Topology #6: STAR InterposingFully Managed (QoS and PTP)

38

PanelView Plus

Plant NetworkPowerFlex

Drives

Point I/O Adapters

CIP Encoders

ArmorBlock I/O

Stratix 5700

Full/PTP

ControlLogix L36ERM


Stratix 5700 Full/PTP Star Yes Yes

Kinetix 5500 orKinetix 6500 Drives

(8) axes were tested in this

topology


Tracking

RegPos

RegTime


Topology #7: STAR InterposingMid-Level Managed (QoS, No PTP)

PanelView Plus

Plant NetworkPowerFlex

Drives

Point I/O Adapters ArmorBlock I/O

Stratix 5700 Full

39


Stratix 5700 Full Star Yes No

CIP Encoders

Kinetix 5500 orKinetix 6500 Drives


Tracking

RegPos

RegTime

CIP Encoders

Did not test beyond (8) axes in this

topology

ControlLogix L36ERM


Lessons Learned/Confirmed

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For devices that include an embedded Ethernet switch: Connect these devices directly to a controller (GM) when possible

without an interposing switch Use a PTP-capable switch if connected between GM and PTP-

sensitive devices Place any non-PTP capable switches at the end of the line of

embedded switch products

Stratix 5700

Full/PTP Any Switch


Lessons Learned/Confirmed

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For single-port Ethernet products (like Kinetix 350 drives): For 1-4 axes, offer a Stratix 2000 unmanaged switch* For 5-8 axes, offer a Stratix 5700 Full managed switch* Over 8 axes, offer a Stratix 5700 Full (PTP) managed switch Use 1783-ETAP devices for ring topologies with Kinetix 350 drives

* The application must not be marginal in terms of dynamics and accuracy requirements

Stratix 2000

Kinetix 350 Drives

Single Switch; no cascading

ControlLogixL36ERM



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Integrated Motion On EtherNet/IP: Maximizing Network Performance