SPRING 2010
即時控制系統設計Design of Real-Time Control Systems
Lecture 31Real-Time Communications for Control Applications
Feng-Li LianNTU-EE
Feb10 – Jun10
NTUEE-RTCS31-RTComm-2Feng-Li Lian © 2010Introduction
04/12/03
Real-Time Control Systems• Controlled by one Computer Processor
– Centralized control systems
– Real-time operating systems
• Controlled by one Communication Medium– Distributed control systems
– Real-time communications
Centralized Control System Distributed Control System
NTUEE-RTCS31-RTComm-3Feng-Li Lian © 2010Introduction
Real-Time Communications
Networks for Control Applications & Automation
Comparison• Static properties
• Dynamic properties
04/12/03
NTUEE-RTCS31-RTComm-4Feng-Li Lian © 2010Networks for Data and Control
Amstron & Wittenmark 97 02/16/03
ni.comni.com
Industrial Bus HierarchyIndustrial Bus Hierarchy
Enterprise
Control
Fieldbus
Devicebus
SensorbusNN NN
NN NN
Fisher
Control PanelFlow
Pressure Alarm ConditionsSTOP
Temperature
Control PanelFlow
Pressure Alarm ConditionsSTOP
Temperature
NTUEE-RTCS31-RTComm-6Feng-Li Lian © 2010Introduction
03/25/04Proposed Network Hierarchy for Open Control, Contemporary Controls
NTUEE-RTCS31-RTComm-7Feng-Li Lian © 2010Introduction
03/25/04Hirschmann Network Systems: Distributed Communication Architecture © Siemens, 2000
8
TIA – Totally Integrated Automation
System bus
Operator terminals
Terminal bus
Engineeringsystem
OS server for multi-user systems,server for BATCH flexible
On-siteoperator panel
Warehouse– CORNERSTONE– SAP Client
Operator station OSas single-user system
Main-frame
Ethernet
Fiber-optic cable
Fiber-optic cable
Ethernet
I/O Block
Sensor
I/O
Hart
MicroMaster
Chip-card
GPS
I/O FieldbusI/O Fieldbus
Coupler
P
SIMOVERTMICROMASTER
SIEMENS
ooo
NTUEE-RTCS31-RTComm-9Feng-Li Lian © 2010Networked Control Systems (NCS)
Definition:• Control systems with physically distributed processing
power and network communication of control signals
02/28/01
...Machine
Tool
A CS
Assembly Line
Discrete-Event/Cell Network
Continuous-Variable/Device Network
Information/System Network
Automatic Material Handling
A CS A CS
Factory ControllerFactory Controller
Cell / SupervisoryController
Cell / SupervisoryController
EquipmentEquipment
Standardized Sensor Bus
EquipmentController
EquipmentController
NTUEE-RTCS31-RTComm-10Feng-Li Lian © 2010Introduction: Networks in Use (1)
In-Vehicle Network Systems
Source: ITS Data Bus Forum
• CAN
• J1850
• J1939
• IDB 1394
02/28/01
NTUEE-RTCS31-RTComm-11Feng-Li Lian © 2010
Network at Tractor and Implement
Source: BioSystems Engineering, Oklahoma State Univ.
Protocols:
• J1850
• J1939
Introduction: Networks in Use (2)
02/28/01
NTUEE-RTCS31-RTComm-12Feng-Li Lian © 2010
Distributed Manipulation Systems
Source: Professor Luntz, ME, Univ. of Michigan, Carnegie Mellon Univ
Source: USA Today
Protocols:• RS232• RS485
Introduction: Networks in Use (3)
02/28/01
NTUEE-RTCS31-RTComm-13Feng-Li Lian © 2010
Advanced Manufacturing Systems
NSF-ERC/EMS, Univ. of Michigan.
Protocols:• DeviceNet• Ethernet• Remote I/O
Introduction: Networks in Use (4)
02/28/01
NTUEE-RTCS31-RTComm-14Feng-Li Lian © 2010
Beverage Packaging & Food Processing
Anchor Products Corporate, New Zealand
Rhode Island Beverage Packaging Plant
Source: Open DeviceNet Vendor Association
Protocols:• ControlNet• DeviceNet• Ethernet• Profibus
Introduction: Networks in Use (5)
02/28/01
NTUEE-RTCS31-RTComm-15Feng-Li Lian © 2010
Automobile Production at OPEL, Germany
Final Assembly: Marriage of chassis and body
Computer Integrated Manufacturing
Source: Profibus
Protocols:ControlNet, DeviceNet, Ethernet, Profibus
Introduction: Networks in Use (6)
02/28/01
NTUEE-RTCS31-RTComm-16Feng-Li Lian © 2010
Beer Brewing at Germany
Source: Profibus
Introduction: Networks in Use (7)
Protocols: ControlNet, DeviceNet, Ethernet, Profibus
02/28/01
NTUEE-RTCS31-RTComm-17Feng-Li Lian © 2010
Orange Picking Robot
Introduction: Networks in Use (8)
05/18/03Cavalieri, Stefano, Mirabella 97
NTUEE-RTCS31-RTComm-18Feng-Li Lian © 2010Network Protocol: Data Networks & Control Networks
04/12/03Raji 94
NTUEE-RTCS31-RTComm-19Feng-Li Lian © 2010Network Protocol: Command- & Status-Based Systems
04/12/03Raji 94
NTUEE-RTCS31-RTComm-20Feng-Li Lian © 2010Network Protocol: Network Topology
04/12/03Bennett 94
(a) bus
(b) star
(c) tree
(d) ring
(e) mesh
NTUEE-RTCS31-RTComm-21Feng-Li Lian © 2010Network Protocol: Network Topology
03/25/04Hirschmann Network Systems: Distributed Communication Architecture
NTUEE-RTCS31-RTComm-22Feng-Li Lian © 2010Network Protocol: ISO-OSI 7-Layer Model
Physical
Data Link
Network
Transport
Session
Presentation
Application
Node A
Physical
Data Link
Network
Transport
Session
Presentation
Application
Node B
Communication Medium
NTUEE-RTCS31-RTComm-23Feng-Li Lian © 2010
data
Network Protocol: Message Framing
Layer Framing
data 1 of 3 data 2 of 3 data 2 of 3
data 1 of 3 data 2 of 3 data 3 of 3
data 1 of 3 data 2 of 3 data 2 of 3
data 1 of 3 data 2 of 3 …data 1 of 3 data 2 of 3 …
data 1 of 3 data 2 of 3
110010011011010101010101010101 110010011011111001010101010101
……Physical
Data Link
Network
Transport
Session
Presentation
Application
NTUEE-RTCS31-RTComm-24Feng-Li Lian © 2010Network Protocol: ISO-OSI 7-Layer Model
Physical
Data Link
Network
Transport
Session
Presentation
ApplicationReal data to send to another network device (IE, FTP, telnet, email)
Encoding data (different computers have different coding systems)
Token management (task exchange), synchronization (checkpoint)
Layer Functions
Split data into packets, and manage to the connect (TCP)
Add addressing for switching and routing (IP, ROUTER/GATEWAY)
Add error detection, flow control, and physical addressing (Medium Access Control, BRIDGE/SWITCH)
Transmits data over the medium (i.e., cable: fiber, twisted pair, etc. HUB/REPEATER)
NTUEE-RTCS31-RTComm-25Feng-Li Lian © 2010Network Protocol: ISO-OSI 7-Layer Model
Physical
Data Link
Network
Transport
Session
Presentation
Application
– Data objects
– Standardized networking structures – Networking structures
– Data interpretation– Authentication
– Network Management
Layer Control Networking Requirements
– End-to-end ACK
– Duplicate detection
– Automatic retries– Addressing, unicast, multicast, broadcast
– Routers– MAC, collision
avoidance/detection
– Framing, data encoding
– Priority
– Media transceivers
ni.comni.com
7 Application
6 Presentation
5 Session
Application layers
4 Transport
3 Network
2 Data link
1 Physical
Datatransport
layers
7 Application
6 Presentation
5 Session
Application layers
4 Transport
3 Network
2 Data link
1 Physical
Datatransport
layers
Typical Industrial NetworksTypical Industrial Networks
NTUEE-RTCS31-RTComm-27Feng-Li Lian © 2010Network Protocol: Physical Layer
$75-
200
$20-
75
$30-
50
$50-
150
$50-
100
$10-
30Node cost
-
0.05-
20
0.5-
30
Infrared
-
1.2-
9.6
50-
10,000
Radio
Medium-
highMedium
None-
LowLow
Installation cost
1-
100,000
300-
10,000
0.06-
10,000
0.3-
2000Data rate
(kb/s)
10-
10,000
10-
10,000
10-
5,000
1-
1000
Range
(m)
Fiber Optics
CoaxialPower Line
Twisted Pair
Characteristics
Raji 94
NTUEE-RTCS31-RTComm-28Feng-Li Lian © 2010Network Protocol: Leading Arch for Distributed Control
Raji 94
NTUEE-RTCS31-RTComm-29Feng-Li Lian © 2010Introduction
03/25/04Hirschmann Network Systems: Distributed Communication Architectureni.comni.com
Capability HierarchyCapability Hierarchy
Level of functionality• Enterprise bus (Ethernet)• Control bus (HSE, ControlNet)• Fieldbus (Foundation Fieldbus, Profibus PA)• Device bus (DeviceNet, Profibus DP, Interbus-S)• Sensor bus (CAN, ASI, Seriplex, LonWorks)
Level of functionality• Enterprise bus (Ethernet)• Control bus (HSE, ControlNet)• Fieldbus (Foundation Fieldbus, Profibus PA)• Device bus (DeviceNet, Profibus DP, Interbus-S)• Sensor bus (CAN, ASI, Seriplex, LonWorks)
NTUEE-RTCS31-RTComm-31Feng-Li Lian © 2010Introduction
03/25/04Hirschmann Network Systems: Distributed Communication Architecture
NTUEE-RTCS31-RTComm-32Feng-Li Lian © 2010Worldwide most popular field busses
Interbus-S
Profibus (3 kinds)
LON
Ethernet
CANs
ASI
Manufacturing
Process control
Building systems
Plant bus
Automotive, Process control
Building Systems
Phoenix Contact
Siemens, ABB
Echelon, ABB
alle
CiA, OVDA, Honeywell
Siemens
Modbus obsolete point-to-point many
ControlNet plant bus Rockwell
Fieldbus Foundation, HART Chemical Industry Fisher-Rosemount, ABB
7%
26%
6%
50%
25%
9%
22%
14%
7%
Sum > 100%, since firms support more than one bus
Bus Application SponsorUser*
*Source: ISA, Jim Pinto (1999)
**European market in 2002: 199 Mio USD, 16.6 % increase (Profibus: 1/3 market share)**Source: Elektronik, Heft 7 2002
NTUEE-RTCS31-RTComm-33Feng-Li Lian © 2010Worldwide most popular field busses
Criterion WorldFIP CAN + LONTalk Seriplex ISP BITBUS
Perf. / Speed / Determinism Good Good Poor Medium Good Medium
Interoperability Good Medium Good Poor Good Medium
Cost and Tech. Leverage Medium Good Medium Poor Medium Medium
Product Availability Medium Good Good Medium Poor Good
Development and Impl. Cost Poor Good Medium Good Poor Good
Outlook Medium Good Good Good Medium Medium
Reliability Good Good Good Medium Good Good
Peer-to-Peer Capability Medium Good Good Poor Medium Poor
Memory Requirements Poor Good Medium Good Poor Medium
User Friend. / Tools Medium Medium Good Medium Medium Medium
Ownership Good Good Poor Poor Good Good
Instal. Base Sem. Mfg. / Proven Poor Medium Good Good Poor Good
Board Size Poor Good Medium Good Poor Good
Msg. Passing Capability Good Medium Good Poor Good Medium
Remaining Work Good Poor Good Poor Medium Medium
Table: Qualitative Candidate Analysis W.R.T. Selection Criteria(Selection criteria listed in order of importance)
Source: ANALYSIS OF SENSOR / ACTUATOR BUS INTEROPERABILITY STANDARD ALTERNATIVES FOR SEMICONDUCTOR MANUFACTURING James R. Moyne, Nader Najafi 1 , Daniel Judd 2 , and Allen Stock 3 University of Michigan, Center for Display Technology Manufacturing, Ann Arbor, MI 48109-2108, 1 IBM, 2 Arlington Laboratories, 3 SEMATECH / Advanced Micro Devices
NTUEE-RTCS31-RTComm-34Feng-Li Lian © 2010Worldwide most popular field busses
10
100
1000
10,000
10c 100 1000 10,000
Sensor BusSimple devicesLow costBus powered (?)Short messages (bits)Fixed configuration Not intrinsically safeTwisted pairMax distance 500m
Low Speed FieldbusProcess instruments, valvesMedium costBus-powered (2 wire)Messages: values, statusIntrinsically safeTwisted pair (reuse 4-20 mA)Max distance 1200m
High Speed FieldbusPLC, DCS, remote I/O, motors$$ Medium costNon bus poweredMessages: values, statusNot intrinsically safeShielded twisted pairMax distance 800m
Data NetworksWorkstations, robots, PCsHigher costNot bus powered Long messages (e-mail, files)Not intrinsically safeCoax cable, fiberMax distance miles
One bus type cannot serveall applications and all device types efficiently...
frame size(bytes)
NTUEE-RTCS31-RTComm-35Feng-Li Lian © 2010Research Issues in Network Systems
Architecture:– Information/System Network (Information)
> Throughput Analysis, Flow Control, Database Management
– Discrete-Event/Cell Network (Control)> Correct & Safe Operation, Logic Control
– Continuous-Variable/Device Network (Instrumentation)> Real-Time Control & Processing
Static Parameters:– Medium Length– Node Number– Data Rate
Dynamic Parameters:Performance:
03/25/04
NTUEE-RTCS31-RTComm-36Feng-Li Lian © 2010Research Issues in Network Systems
Architecture:Static Parameters:Dynamic Parameters:
– Message Connection– Medium Access Control
Performance:– Network QoS
> Throughput> Network Utilization> Network Efficiency> Network Stability
– Network Delay> Message Period> Delay Statistics
03/25/04
NTUEE-RTCS31-RTComm-37Feng-Li Lian © 2010Microprocessor & Interfacing of Networked Device
Interface between network and sensor/actuator
Sensor/actuator
Network
Data Link Layer
Controller
microprocessorApplication
Layer Program
DeviceNet network interface card
NTUEE-RTCS31-RTComm-38Feng-Li Lian © 2010Components of Time Delay
Physical Layer
Data Link Layer
Application Layer
Node A Node B
Tpre
TwaitTpost
Tpre
TwaitTpost
Ttx
Ttx
Physical Layer
Data Link Layer
Application Layer
• Total end-to-end delay is the sum of– Pre-processing time: microprocessor– Waiting time: network protocol - MAC– Transmission time: data rate & length– Post-processing time: microprocessor
Depend on network protocol
and loading
Depend on network protocol
and loading
NTUEE-RTCS31-RTComm-39Feng-Li Lian © 2010Industrial Networks
3 main types of Medium Access Control (MAC)
• Ethernet:– EIB, EtherNet/IP, LonWorks, Modbus/TCP
• Token Passing:– BACnet, ControlNet, FDDI, MAP, P-Net, Profibus, SP50, WorldFIP
• Priority Based:– CAN, DeviceNet, SDS, CANOpen, CAN-Kingdom
NTUEE-RTCS31-RTComm-40Feng-Li Lian © 2010
Carrier Sense Multiple Access / Collision Detection (CSMA/CD)
• listen busy wait
• listen idle send
• collision backoff
Backoff algorithm• standard binary exponential backoff
• max collision = 16
• potential for lost data
Ethernet
• Random time delays
NTUEE-RTCS31-RTComm-41Feng-Li Lian © 2010Ethernet
Hirschmann Network Systems: Distributed Communication Architecture 03/25/04
NTUEE-RTCS31-RTComm-42Feng-Li Lian © 2010
Concurrent Time Domain Multiple Access (CTDMA) / Implicit Token Passing Bus
• a token rotating around the logical ring
• every device can listen to the network
• without token wait
• with token send messages
1 4
2 3
Token-Passing: ControlNet
• Bounded time delays
NTUEE-RTCS31-RTComm-43Feng-Li Lian © 2010
Carrier Sense Multiple Access / Arbitration on Message Priority (CSMA/AMP)
• a bit-synchronized bus
• devices and messages have different priorities
• listen busy wait
• listen idle send
• collision low-priority node backoff,high-priority node keep on sending
1 3
2
Priority Based: DeviceNet
• Constant time delays