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Networked Control Systems Theory and Its Application
Shanbin Li, PhD student NCS Research Group National Laboratory of Industrial Control Technology Zhejiang University
2013-9-10
ZJU-NLICT-NCS Research Group By Shanbin Li
11
Methodology One: Scheduling Part
Revise network MAC protocol
Ye, Walsh, Bushnell 2000 introduce a scheduling protocol PCSMA/CA (Prioritized-CSMACA) based on IEEE 802.11 wireless standard. For the first time, they proposed and validated several new algorithms, a constant penalty, an estimated error order and a lag first order for dynamically scheduling the traffic of wireless networked control systems.
Methodology Two: Control Part
Augmented deterministic discrete-time method
Halevi and Ray，1988 proposed a method to control a linear plant over periodic delay network Liou and Ray，1990 introduced a method to analyze the systems with multi-rate sampling sensor and control
2013-9-10
kh
(k 1)h
8
ZJU-NLICT-NCS Research Group By Shanbin Li
Vacant Sampling and Packet loss
Sensor node
yk
Controller node
Packet loss or message rejection
2013-9-10
Partly Digital Partly Analogous Completely Distributed
ZJU-NLICT-NCS Research Group By Shanbin Li 4
Introduction
h
Actuator
u (t )
Plant
y (t )
2013-9-10
ZJU-NLICT-NCS Research Group By Shanbin Li
2
Introduction
What is networked control system? ? Do you know the fundamentals of NCS? Network has its positive side ,what is negative side?
2013-9-10
ZJU-NLICT-NCS Research Group By Shanbin Li
3
Development history of control system
Analogous control system Centralized digital control system Decentralized control system Fieldbus control system (FCS) Networked control system (NCS) by Gregory C. Walsh 1998 Integrated communication and control systems (ICCS) by Ray Asok 1988
Actuator node
Vacant sampling
Plant input
uk
(k 1)h
kh
(k 1)h
9
2013-9-10
ZJU-NLICT-NCS Research Group By Shanbin Li
State-of-the-arts of NCS
2013-9-10
ZJU-NLICT-NCS Research Group By Shanbin Li
6
QoS-parameters of network considered in the control loop
Time-delay
It varies with network topology, network protocol, network load, network bandwidth and package size Its value may be bounded, unbounded, time-varying, constant and random
2013-9-10
ZJU-NLICT-NCS Research Group By Shanbin Li
1
Networked Control Systems Theory and Its Application
Introduction State-of-the-arts of NCS Our results Current focus Future work Summary Questions and remarks
2013-9-10
ZJU-NLICT-NCS Research Group By Shanbin Li
10
Methodology One: Scheduling Part
Revise network MAC protocol
Walsh ,Ye, Bushnell 1999 introduce an novel protocol TOD (Try-OnceDiscard) and scheduling method MEF (Maximum-Error-First) based on the MATI (Maximal-Allowable-Transfer-Interval) which is denoted as . In TOD, the node with the greatest weighted error from its last report value will win the competition for the network resource .If a data packet fails to win the competition for network access, it is discarded and new data is used next time. Again, the MATI constraint ensures at least one such transmission every . This protocol can be realized by using CAN.
P-CSMA-CA:
Level 1: highest priority, time-critical aperiodic data that is burst and cannot bear any loss, retransmission is required when the formal transmission is unsuccessful ; Level 2: time-critical periodic that can tolerate some loss, data that has not been sent will be discarded Level 3: lowest priority, consists of noncritical data which requires data integrity.Retransmission is implemented. If collisions occur, a random back-off is adopted .
2013-9-10
ZJU-NLICT-NCS Research Group By Shanbin Li
13
Methodology One: Scheduling Part Shaping
2013-9-10
ZJU-NLICT-NCS Research Group By Shanbin Li
14
Sensor
ca tk
Network
sc tk
Controller Estimator
2013-9-10
Reference
ZJU-NLICT-NCS Research Group By Shanbin Li
5
Definition of NCS
NCS is a completely distributed and networked real-time feedback control system. It is an integration of sensors, controllers (+estimators), actuators and communication network of certain local field and is used to provide data transmission between devices in order that users of different sites can realize resource sharing and coordinating manipulation.
Packet losses
2013-9-10
ZJU-NLICT-NCS Research Group By Shanbin Li
7
Normal Sampling
Sensor node
yk
Controller node
sc tk
ca tk
Actuator node
uk
uk
Plant input
(k 1)h
Methodology One: From the view of guaranteeing network QoS. Quality of This is a scheduling methodology. Performance
Methodology Two: From the view of guaranteeing system QoP. This is a control methodology. Methodology Three: QoS and QoP co-consideration. This is an integrated scheduling and control methodology.
12
2013-9-10
ZJU-NLICT-NCS Research Group By Shanbin Li
Methodology One: Scheduling Part
Sampling time scheduling
Hong, 1995 presented a scheduling method of network bandwidth allocation and sampling period decision for multi-loop NCSs in virtue of the notion “window”, namely the service window of each transmission data in network. Hong & Kim 2000 extended this method to random delay networks such as CAN Kim, Kwon, and Park 1996, 1998 enhanced the concept of sampling time scheduling to develop another algorithm for multi-dimensional NCS.
Shanbin Li, PhD student NCS Research Group National Laboratory of Industrial Control Technology Zhejiang University
2013-9-10
ZJU-NLICT-NCS Research Group By Shanbin Li
11
Methodology One: Scheduling Part
Revise network MAC protocol
Ye, Walsh, Bushnell 2000 introduce a scheduling protocol PCSMA/CA (Prioritized-CSMACA) based on IEEE 802.11 wireless standard. For the first time, they proposed and validated several new algorithms, a constant penalty, an estimated error order and a lag first order for dynamically scheduling the traffic of wireless networked control systems.
Methodology Two: Control Part
Augmented deterministic discrete-time method
Halevi and Ray，1988 proposed a method to control a linear plant over periodic delay network Liou and Ray，1990 introduced a method to analyze the systems with multi-rate sampling sensor and control
2013-9-10
kh
(k 1)h
8
ZJU-NLICT-NCS Research Group By Shanbin Li
Vacant Sampling and Packet loss
Sensor node
yk
Controller node
Packet loss or message rejection
2013-9-10
Partly Digital Partly Analogous Completely Distributed
ZJU-NLICT-NCS Research Group By Shanbin Li 4
Introduction
h
Actuator
u (t )
Plant
y (t )
2013-9-10
ZJU-NLICT-NCS Research Group By Shanbin Li
2
Introduction
What is networked control system? ? Do you know the fundamentals of NCS? Network has its positive side ,what is negative side?
2013-9-10
ZJU-NLICT-NCS Research Group By Shanbin Li
3
Development history of control system
Analogous control system Centralized digital control system Decentralized control system Fieldbus control system (FCS) Networked control system (NCS) by Gregory C. Walsh 1998 Integrated communication and control systems (ICCS) by Ray Asok 1988
Actuator node
Vacant sampling
Plant input
uk
(k 1)h
kh
(k 1)h
9
2013-9-10
ZJU-NLICT-NCS Research Group By Shanbin Li
State-of-the-arts of NCS
2013-9-10
ZJU-NLICT-NCS Research Group By Shanbin Li
6
QoS-parameters of network considered in the control loop
Time-delay
It varies with network topology, network protocol, network load, network bandwidth and package size Its value may be bounded, unbounded, time-varying, constant and random
2013-9-10
ZJU-NLICT-NCS Research Group By Shanbin Li
1
Networked Control Systems Theory and Its Application
Introduction State-of-the-arts of NCS Our results Current focus Future work Summary Questions and remarks
2013-9-10
ZJU-NLICT-NCS Research Group By Shanbin Li
10
Methodology One: Scheduling Part
Revise network MAC protocol
Walsh ,Ye, Bushnell 1999 introduce an novel protocol TOD (Try-OnceDiscard) and scheduling method MEF (Maximum-Error-First) based on the MATI (Maximal-Allowable-Transfer-Interval) which is denoted as . In TOD, the node with the greatest weighted error from its last report value will win the competition for the network resource .If a data packet fails to win the competition for network access, it is discarded and new data is used next time. Again, the MATI constraint ensures at least one such transmission every . This protocol can be realized by using CAN.
P-CSMA-CA:
Level 1: highest priority, time-critical aperiodic data that is burst and cannot bear any loss, retransmission is required when the formal transmission is unsuccessful ; Level 2: time-critical periodic that can tolerate some loss, data that has not been sent will be discarded Level 3: lowest priority, consists of noncritical data which requires data integrity.Retransmission is implemented. If collisions occur, a random back-off is adopted .
2013-9-10
ZJU-NLICT-NCS Research Group By Shanbin Li
13
Methodology One: Scheduling Part Shaping
2013-9-10
ZJU-NLICT-NCS Research Group By Shanbin Li
14
Sensor
ca tk
Network
sc tk
Controller Estimator
2013-9-10
Reference
ZJU-NLICT-NCS Research Group By Shanbin Li
5
Definition of NCS
NCS is a completely distributed and networked real-time feedback control system. It is an integration of sensors, controllers (+estimators), actuators and communication network of certain local field and is used to provide data transmission between devices in order that users of different sites can realize resource sharing and coordinating manipulation.
Packet losses
2013-9-10
ZJU-NLICT-NCS Research Group By Shanbin Li
7
Normal Sampling
Sensor node
yk
Controller node
sc tk
ca tk
Actuator node
uk
uk
Plant input
(k 1)h
Methodology One: From the view of guaranteeing network QoS. Quality of This is a scheduling methodology. Performance
Methodology Two: From the view of guaranteeing system QoP. This is a control methodology. Methodology Three: QoS and QoP co-consideration. This is an integrated scheduling and control methodology.
12
2013-9-10
ZJU-NLICT-NCS Research Group By Shanbin Li
Methodology One: Scheduling Part
Sampling time scheduling
Hong, 1995 presented a scheduling method of network bandwidth allocation and sampling period decision for multi-loop NCSs in virtue of the notion “window”, namely the service window of each transmission data in network. Hong & Kim 2000 extended this method to random delay networks such as CAN Kim, Kwon, and Park 1996, 1998 enhanced the concept of sampling time scheduling to develop another algorithm for multi-dimensional NCS.