Networked Control Systems Lecture Notes

Networked Control Systems Lecture Notes

Laura Giarr´e

Networked Control Systems: Introduction

I Course Objectives I Rules

I Materials

I Tentative scheduling

L. Giarr´ e- Networked Control Systems 2020-2021 - 2

Course Objectives

I To learn how to identify and control a networked system, both theoretically and practically.

I To understand the model and the algorithms to be used in a network of agents and sensors.

I Estimation theory, Graph theory, consensus theory, information theory is essential for distributed control and identification. I Understands the limitations of the current state-of-the-art and

trends in NCSs

Course Objectives

I To learn how to identify and control a networked system, both theoretically and practically.

I To understand the model and the algorithms to be used in a network of agents and sensors.

I Estimation theory, Graph theory, consensus theory, information theory is essential for distributed control and identification. I Understands the limitations of the current state-of-the-art and

trends in NCSs

L. Giarr´ e- Networked Control Systems 2020-2021 - 3

Course Objectives

I To learn how to identify and control a networked system, both theoretically and practically.

I To understand the model and the algorithms to be used in a network of agents and sensors.

I Estimation theory, Graph theory, consensus theory, information theory is essential for distributed control and identification.

I Understands the limitations of the current state-of-the-art and

trends in NCSs

Course Objectives

I To learn how to identify and control a networked system, both theoretically and practically.

I To understand the model and the algorithms to be used in a network of agents and sensors.

I Estimation theory, Graph theory, consensus theory, information theory is essential for distributed control and identification.

I Understands the limitations of the current state-of-the-art and trends in NCSs

L. Giarr´ e- Networked Control Systems 2020-2021 - 3

Tests and Grading

Grading Homeworks: 10%+ Presentation of a paper and discussion:

20% + Implementation of a project: 70%

Materials

I Slides and Videos I Reference books:

I Lectures on Network Systems. Francesco Bullo. CreateSpace Independent Publishing Platform, Mar 10, 2018 - Network analysis (available online @

http://motion.me.ucsb.edu/book-lns/)

I Graph Theoretic Methods in Multiagent Networks di Mehran Mesbahi Magnus Egerstedt (2010) di Princeton University Press

I L. Lyung System Identification Theory for the user 1998 I Themistoklis Charalambous Lecture notes Aalto Finland http://www.themistoklis.org/teaching.html ELEC-E8123:

Networked Control Systems

L. Giarr´ e- Networked Control Systems 2020-2021 - 5

Tentative Schedule

LEC DATES TOPICS

1 (2) 22/09 Rules and Introduction 2 (2) 24/09 Review of past material 3 (2) 29/09 Examples- homeworks 4 (2) 1/10 Review of past material 5 (2) 6/10 Examples- homework 6 (2) 8/10 Estimation

7 (2) 13/10 Example and exercises 8 (2) 15/10 Least square

9 (2) 20/10 Examples and exercises - Homeworks 10(2) 21/10 Consensus Algorithm

11(2) 27/10 Examples and exercises - Homeworks

Tentative Schedule

LEC DATES TOPICS

14 (2) 5/11 Information Theory 15 (2) 10/11 Examples and howeworks 16 (2) 13/11 Sampling theory

17 (2) 17/11 Examples and homeworks

18 (2) 19/11 Communication links, data theorems, and their effect on control

19 (2) 24/11 Examples

20 (2) 26/11 Stabilization of LTI systems over fading channels 21 (2) 1/12 Examples

22 (2) 2/12 Channel Scheduling and Access

in (Wireless) Networked Control Systems 23 (2) 10/12 Application and Homeworks

24 (2) 15/12 Identification

25 (2) 18/12 Examples and homeworks 26 (2) 22/12 Recap

L. Giarr´ e- Networked Control Systems 2020-2021 - 7

Networked Control Systems: Overview

I Introduction to the problem

I Applications

Where do we find sensors?

Nowadays, sensors appear (almost) everywhere

I Our smartphones (magnetometer, GPS, gyroscope, accelerometer, proximity sensor, ambient light sensor, ...) I (Wireless) industrial automation

I Infrastructure monitoring and control I Automated vehicles

I Intelligent transportations systems

I Wireless sensor and actuator networks in rescue operations I ...

L. Giarr´ e- Networked Control Systems 2020-2021 - 9

Where do we find sensors?

Nowadays, sensors appear (almost) everywhere

I Our smartphones (magnetometer, GPS, gyroscope, accelerometer, proximity sensor, ambient light sensor, ...) I (Wireless) industrial automation

I Infrastructure monitoring and control I Automated vehicles

I Intelligent transportations systems

I Wireless sensor and actuator networks in rescue operations

I ...

Applications: Network Information processing

I Exploiting everything connected: information processing on a global scale

Motivation

Applications: networked information processing

Exploiting everything connected: information processing on a global scale ^{L. Giarr´} e- Networked Control Systems 2020-2021 - 10

Applications: network information processing

I Exploiting everything connected: information processing on a large

scale, e.g., google traffic information:

Applications: Wide area sensing and monitoring

I Sensor networks (with applications in, e.g., machine-to-machine communication for security, surveillance and environmental management)

I A water quality monitoring technology in a wide area is developed to detect water pollution in streams, rivers and coastal areas I Water pollution data from water quality sensors are transmitted

between the field servers with the sensors and finally, to the base station (sink) through a designed self-organizing autonomous wireless sensor network

L. Giarr´ e- Networked Control Systems 2020-2021 - 12

Applications: Micro-Electro-Mechanical Systems

I Micro-Electro-Mechanical Systems (MEMS) ¹ are extensively used in smartphones, wearable devices, and other electronic devices, owing to its enhanced electrical performance at high frequencies. The MEMS market is expected to gain popularity as the consumer electronics industry is shifting its focus from traditional sensors to MEMS technology ² I In current and future generations of MEMS, there can be as many as

10 ⁴ − 10 ⁶ actuators or sensors on a single chip, and their aim is to control

one or more dynamical systems by deploying a shared network for data

exchange

Applications: Autonomous/automated cars

Source: www.networkworld.com/article/3147892/internet/one-autonomous-car-will-use-4000-gb-of-dataday.html

I Self-driving cars will soon create significantly more data than people

L. Giarr´ e- Networked Control Systems 2020-2021 - 14

Applications: Intelligent transportation systems

I Interconnecting vehicles and infrastructure for safety and

efficiency

Applications: Smart Energy Networks

I Distributed energy management in smart energy networks, e.g.,

I Distributed optimal power dispatch (OPD) ³ problem

3 OPD aims at managing real power generation to control the frequency to be close to the rated value (usually 50Hz).

L. Giarr´ e- Networked Control Systems 2020-2021 - 16

From sensing to decisions and control

I Ongoing challenge: transform networked sensor data to effective decisions

I Network limitations determine how to sense, process and act on data

I In this course, we will focus on the following concepts:

I Minimum rates required to stabilize a networked-constrained control system for different channels

I How is the data transmitted (quantization) given the data rate

Introduction

I The feedback loop of a NCS is closed via a communication network

I NCSs are spatially distributed systems wherein the control loops are closed through a communication network 1.2. The need for research on wireless networked control systems 5

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Figure 1.2: Block diagrams of networked control systems with a plant P, a sensor

S, a controller C, and an actuator A. In the figure, (a) illustrates that a controller is going to be designed for a given abstraction of network and plant whereas (b) shows that both a controller and communication protocol is going to be designed for a given plant.

Throughout this thesis, we propose new analysis and design frameworks to improve the performance guarantees of wireless networked control systems. Specifi- cally, Chapter 3 develops a co-design framework in which we jointly optimize the communication protocol (how wireless nodes forward data packets over multiple unreliable hops to guarantee a certain level of latency and end-to-end packet delivery rate) and the control algorithms. Chapter 4 determines the optimal number of retransmission attempts to minimize the expected control loss of the closed-loop control system. In addition, it demonstrates whether or not the maximal number of retransmissions depends on the control architecture (e.g., time- or event-driven).

Chapter 5 investigates how event-triggered communication from the controller to the actuator allows to reduce the network traffic (and, indirectly, the energy con- sumption of the network) while maintaining the same control performance. Finally, Chapter 6 presents a supervisory control structure that only needs a crude idea of the network state (or rather, on the network-induced end-to-end delays) to trigger the most appropriate controller from a multi-controller unit.

We would like to point out that this thesis focuses on challenges related to ensuring good performance of a networked control loop in the presence of information delays and losses. Networked control systems also pose a range of challenges that are not covered in this thesis, e.g., network security and resilience to structural changes (e.g., sensors and/or actuators that are added and removed). See, for example, the theses [8,9] and the references therein.

1.2. The need for research on wireless networked control systems 5

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Figure 1.2: Block diagrams of networked control systems with a plant P, a sensor

S, a controller C, and an actuator A. In the figure, (a) illustrates that a controller is going to be designed for a given abstraction of network and plant whereas (b) shows that both a controller and communication protocol is going to be designed for a given plant.

Throughout this thesis, we propose new analysis and design frameworks to improve the performance guarantees of wireless networked control systems. Specifi- cally, Chapter 3 develops a co-design framework in which we jointly optimize the communication protocol (how wireless nodes forward data packets over multiple unreliable hops to guarantee a certain level of latency and end-to-end packet delivery rate) and the control algorithms. Chapter 4 determines the optimal number of retransmission attempts to minimize the expected control loss of the closed-loop control system. In addition, it demonstrates whether or not the maximal number of retransmissions depends on the control architecture (e.g., time- or event-driven).

Chapter 5 investigates how event-triggered communication from the controller to the actuator allows to reduce the network traffic (and, indirectly, the energy con- sumption of the network) while maintaining the same control performance. Finally, Chapter 6 presents a supervisory control structure that only needs a crude idea of the network state (or rather, on the network-induced end-to-end delays) to trigger the most appropriate controller from a multi-controller unit.

We would like to point out that this thesis focuses on challenges related to ensuring good performance of a networked control loop in the presence of information delays and losses. Networked control systems also pose a range of challenges that are not covered in this thesis, e.g., network security and resilience to structural changes (e.g., sensors and/or actuators that are added and removed). See, for example, the theses [8,9] and the references therein.

1.2. The need for research on wireless networked control systems 5

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(a) (b)

Figure 1.2: Block diagrams of networked control systems with a plant P, a sensor

S, a controller C, and an actuator A. In the figure, (a) illustrates that a controller is going to be designed for a given abstraction of network and plant whereas (b) shows that both a controller and communication protocol is going to be designed for a given plant.

Throughout this thesis, we propose new analysis and design frameworks to improve the performance guarantees of wireless networked control systems. Specifi- cally, Chapter 3 develops a co-design framework in which we jointly optimize the communication protocol (how wireless nodes forward data packets over multiple unreliable hops to guarantee a certain level of latency and end-to-end packet delivery rate) and the control algorithms. Chapter 4 determines the optimal number of retransmission attempts to minimize the expected control loss of the closed-loop control system. In addition, it demonstrates whether or not the maximal number of retransmissions depends on the control architecture (e.g., time- or event-driven).

Chapter 5 investigates how event-triggered communication from the controller to the actuator allows to reduce the network traffic (and, indirectly, the energy con- sumption of the network) while maintaining the same control performance. Finally, Chapter 6 presents a supervisory control structure that only needs a crude idea of the network state (or rather, on the network-induced end-to-end delays) to trigger the most appropriate controller from a multi-controller unit.

We would like to point out that this thesis focuses on challenges related to ensuring good performance of a networked control loop in the presence of information delays and losses. Networked control systems also pose a range of challenges that are not covered in this thesis, e.g., network security and resilience to structural changes (e.g., sensors and/or actuators that are added and removed). See, for example, the theses [8,9] and the references therein.

1.2. The need for research on wireless networked control systems 5

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(a) (b)

Figure 1.2: Block diagrams of networked control systems with a plant P, a sensor

S, a controller C, and an actuator A. In the figure, (a) illustrates that a controller is going to be designed for a given abstraction of network and plant whereas (b) shows that both a controller and communication protocol is going to be designed for a given plant.

Throughout this thesis, we propose new analysis and design frameworks to improve the performance guarantees of wireless networked control systems. Specifi- cally, Chapter 3 develops a co-design framework in which we jointly optimize the communication protocol (how wireless nodes forward data packets over multiple unreliable hops to guarantee a certain level of latency and end-to-end packet delivery rate) and the control algorithms. Chapter 4 determines the optimal number of retransmission attempts to minimize the expected control loss of the closed-loop control system. In addition, it demonstrates whether or not the maximal number of retransmissions depends on the control architecture (e.g., time- or event-driven).

Chapter 5 investigates how event-triggered communication from the controller to the actuator allows to reduce the network traffic (and, indirectly, the energy con- sumption of the network) while maintaining the same control performance. Finally, Chapter 6 presents a supervisory control structure that only needs a crude idea of the network state (or rather, on the network-induced end-to-end delays) to trigger the most appropriate controller from a multi-controller unit.

We would like to point out that this thesis focuses on challenges related to ensuring good performance of a networked control loop in the presence of information delays and losses. Networked control systems also pose a range of challenges that are not covered in this thesis, e.g., network security and resilience to structural changes (e.g., sensors and/or actuators that are added and removed). See, for example, the theses [8,9] and the references therein.

I The use of a shared network to connect spatially distributed components, e.g., actuators, sensors and controllers, makes it possible to design large-scale systems

I The constraints in communication and the interaction between control and communication make the classical approaches not suitable

L. Giarr´ e- Networked Control Systems 2020-2021 - 18

Building blocks of NCSs

Sensors are the collectors of data.They are the simplest devices (e.g., electronic sensors, biosensors, chemical sensors) in the network and their number is usually large. They have to be cheap, and hence operate on low energy budget.

Actuators are the recipients of instructions and perform the action(s) prompted to them by a controller.

Controllers sensors transmit the system output to the controller

by putting the sensor measurement into a frame or a packet. The

control signal is encapsulated in a frame or a packet and sent to

the actuator via the network as well.

Building blocks of NCSs

Sensing and actuation in Industrial Internet

• Embedding sensors and actuators in machines (and other physical objects) brings them into the connected world

• Sensors are the collectors of data

• Actuators are the recipients of instructions and perform the action(s) prompted to them by a controller

14 Background

P

C

S

A P

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S A

Network

P

S A

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Figure 2.1: Block diagram of general networked control systems. Multiple control loops, with each loop consisting of a plant Piand a controller Cifor all i ∈ {1, �, N }, share a communication network. Each controller Cicommunicates with the sensor Si and the actuator Aiby sending messages over the shared communication network.

• Variable communication delays (latency). Data transmission over a wireless network takes an uncertain amount of time due to several reasons.

If multiple senders try using the same link, each of them has to wait for an uncertain amount of time before the link becomes available to initiate their data transfer. In addition, collisions – introducing an extra delay until packets can be successfully retransmitted – almost always happen in shared links.

Packet retransmissions are also used to improve reliability of lossy networks.

• Data rate (bandwidth). When different devices use a shared network re- source, the rate at which they communicate over this network is limited by the network capacity [30,33]. This limitation, in turn, imposes a constraint on the stability of closed-loop control systems. For example, the works [34–37]

have focused on identifying the minimal data rate required to stabilize a linear system.

Bearing in mind that any of these aforementioned imperfections may deteriorate the closed-loop control performance, or even cause the control system to become unstable [30], it is crucial to know how these imperfections can affect the closed-loop system in terms of control performance and stability. The next section provides a brief summary of existing models of delays and losses.

(b) A networked control system; each controller aims to communicate with its Actuator and Sensor through a shared network.

1.2. The need for research on wireless networked control systems 5

P

C

Network S A

!"#$%

&$'"!%$&

P

C

S A

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&$'"!%$&

(a) (b)

Figure 1.2: Block diagrams of networked control systems with a plant P, a sensor S, a controller C, and an actuator A. In the figure, (a) illustrates that a controller is going to be designed for a given abstraction of network and plant whereas (b) shows that both a controller and communication protocol is going to be designed for a given plant.

Throughout this thesis, we propose new analysis and design frameworks to improve the performance guarantees of wireless networked control systems. Specifi- cally, Chapter 3 develops a co-design framework in which we jointly optimize the communication protocol (how wireless nodes forward data packets over multiple unreliable hops to guarantee a certain level of latency and end-to-end packet delivery rate) and the control algorithms. Chapter 4 determines the optimal number of retransmission attempts to minimize the expected control loss of the closed-loop control system. In addition, it demonstrates whether or not the maximal number of retransmissions depends on the control architecture (e.g., time- or event-driven).

Chapter 5 investigates how event-triggered communication from the controller to the actuator allows to reduce the network traffic (and, indirectly, the energy con- sumption of the network) while maintaining the same control performance. Finally, Chapter 6 presents a supervisory control structure that only needs a crude idea of the network state (or rather, on the network-induced end-to-end delays) to trigger the most appropriate controller from a multi-controller unit.

We would like to point out that this thesis focuses on challenges related to ensuring good performance of a networked control loop in the presence of information delays and losses. Networked control systems also pose a range of challenges that are not covered in this thesis, e.g., network security and resilience to structural changes (e.g., sensors and/or actuators that are added and removed). See, for example, the theses [8,9] and the references therein.

1.2. The need for research on wireless networked control systems 5

P

C

Network S A

!"#$%

&$'"!%$&

P

C

S A

!"#$%

&$'"!%$&

(a) (b)

Figure 1.2: Block diagrams of networked control systems with a plant P, a sensor S, a controller C, and an actuator A. In the figure, (a) illustrates that a controller is going to be designed for a given abstraction of network and plant whereas (b) shows that both a controller and communication protocol is going to be designed for a given plant.

Throughout this thesis, we propose new analysis and design frameworks to improve the performance guarantees of wireless networked control systems. Specifi- cally, Chapter 3 develops a co-design framework in which we jointly optimize the communication protocol (how wireless nodes forward data packets over multiple unreliable hops to guarantee a certain level of latency and end-to-end packet delivery rate) and the control algorithms. Chapter 4 determines the optimal number of retransmission attempts to minimize the expected control loss of the closed-loop control system. In addition, it demonstrates whether or not the maximal number of retransmissions depends on the control architecture (e.g., time- or event-driven).

Chapter 5 investigates how event-triggered communication from the controller to the actuator allows to reduce the network traffic (and, indirectly, the energy con- sumption of the network) while maintaining the same control performance. Finally, Chapter 6 presents a supervisory control structure that only needs a crude idea of the network state (or rather, on the network-induced end-to-end delays) to trigger the most appropriate controller from a multi-controller unit.

We would like to point out that this thesis focuses on challenges related to ensuring good performance of a networked control loop in the presence of information delays and losses. Networked control systems also pose a range of challenges that are not covered in this thesis, e.g., network security and resilience to structural changes (e.g., sensors and/or actuators that are added and removed). See, for example, the

theses [8,9] and the references therein.

(a) A classical control system

(via a communication network)

I Embedding sensors and actuators in machines (and other physical objects) −→ brings them into the connected world

L. Giarr´ e- Networked Control Systems 2020-2021 - 20

I The interplay between communication (wired or wireless) and control requires a new paradigm, since estimation/control interacts with communication in various ways:

I a critical transmission rate below which there does not exist any quantization and control scheme able to stabilize an unstable plant

I when a signal is transmitted over a digital network, the signal must be sampled, encoded in a digital format, transmitted over the network and finally the data must be decoded at the receiver side, thus inducing delays in the feedback loop I a critical packet-loss rate above which the mean state

estimation error covariance matrices of the Kalman filter will diverge

I the variable network conditions such as congestion and channel

quality may also induce variable delays due to the network

I These phenomena strongly imply that the network has significant effects on the control/filtering performance

I This raises new fundamental challenges in investigating NCSs from the perspective of unifying communication, estimation, and control

I Reliable transmission protocols such as TCP (handshake) not always appropriate for NCSs since data that are retransmitted are outdated and may not be useful - communication

protocols should be revised as well

L. Giarr´ e- Networked Control Systems 2020-2021 - 22

Applications: Wireless industrial automation

I Today’s industrial control systems use a multitude of spatially distributed sensors and actuators to monitor and control physical processes

I Traditionally, resorted to wired communication infrastructure

to exchange information among various system components

Applications: Wireless industrial automation

I Traditionally, resorted to wired communication infrastructure to exchange information among various system components

I Communication cabling: high set-up costs; subject to heavy wear and tear in industry robots and therefore requires frequent maintenance

I slow deployment

I impossible in certain scenarios

L. Giarr´ e- Networked Control Systems 2020-2021 - 24

Wired vs Wireless Communications

I New feature/trend in NCSs - use of wireless communications −→ Wireless NCSs (WNCSs)

X Cost reduction: faster & cheaper installations, more efficient monitoring and fault diagnosis X Flexibility: easy to add, replace and modify

wireless sensors; sensor and actuator nodes can be placed more appropriately; less restrictive maneuvers and control actions; more powerful control through distributed computations X Reliability: wear- and tear-free data transfer,

and fairly reliable communication without the use of expensive connectors

Wired vs Wireless Communication

• Common feature in Industrial Internet - use of wireless communications:


• Today’s industrial control systems use a multitude of spatially distributed sensors and actuators to monitor and control physical processes

• Traditionally resorted to wired communication infrastructure to exchange information among various system components

• High set-up and maintenance costs of physical wires, slow deployment, impossible in certain scenarios

✓ Cost reduction: faster & cheaper installations, efficient fault isolations

✓ Flexibility: easy to add, replace and modify wireless sensors

✓ Reliability: wear- and tear-free data transfer, and fairly reliable communication

Wired vs Wireless Communications

7 Complexity: systems designers and programmers need suitable abstractions to hide the complexity from wireless devices and communication

7 Security: wireless technology is vulnerable; security mechanisms needed for control loops

7 Reliability: systems should have robust and predictable behavior despite characteristics of wireless networks

L. Giarr´ e- Networked Control Systems 2020-2021 - 26

Example of a Wireless Networked Control System (WNCS)

Example of a wireless networked control system

UWB anchors:

placed in steady positions in the indoor space

quadrotor with an UWB tag

onboard computer: that serves

as the controller

Classical approach

Classical control approach

Positioning System desired Σ

position

error e k

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• Tested indoors with the fastest settings: 64 bit preamble length and bitrate 6.81 Mbits/sec which result in a message update rate of 30Hz.

• Mean response time: 200-300ms +

-

(¯

x, ¯ y)

Network Controller control

input

received position

actual position

L. Giarr´ e- Networked Control Systems 2020-2021 - 28

Classical approach

Classical control approach

Positioning System desired Σ

position

error e k

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(x

d , y d ) u

k (x, y)

• Tested indoors with the fastest settings: 64 bit preamble length and bitrate 6.81 Mbits/sec which result in a message update rate of 30Hz.

+ -

(¯

x, ¯ y)

Network Controller control

input

received position

actual

position

WNCSs approach

desired Σ position (x _d , y _d )

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+

- error

e _k

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Challenges:

• Synthesize communication-aware controllers, i.e., controllers that account for communication impairments

Communication- aware controller

• Design control-aware communication protocols

• Design filtering and prediction methods to make the performance more robust to noise

(¯ x, ¯ y)

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Filtering

Networked control systems’ approach

received position (ˆ

x, ˆ y)

estimated

position Network

Positioning System control- aware

(x, y)

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u _k

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control

input actual

position

Challenges:

I Synthesize communication-aware controllers, i.e., controllers that account for communication impairments

I Design control-aware communication protocols I Design filtering and prediction methods to make the

performance more robust to noise

L. Giarr´ e- Networked Control Systems 2020-2021 - 29

Brief history of NCSs

I Centralized point-to-point control system: Research of NCSs was primarily fueled by point-to-point communications.

Components are connected via hardwired connections and the systems are designed to bring all the information from the sensors to a central location where decisions are taken. Not suitable to meet new application requirements in terms of:

I modularity

I decentralization of control I integrated diagnostics

I quick and easy maintenance and low cost

Brief history of NCSs

I Network protocols for industrial control: a serial bus for high-speed communications - can improve the efficiency, flexibility and reliability of NCSs through reduced wiring and distributed intelligence, and so reduce the installation, reconfiguration and maintenance time and costs. Controller Area Network (CAN) bus ⁴ was designed by Bosch to fulfill the communication between components within a vehicle. Other industrial network protocols including Foundation Fieldbus and DeviceNet were developed about the same time period.

4 A CAN bus is a bus standard to allow components to communicate with each other in applications without a host computer. It is a message-based protocol, designed originally for multiplex electrical wiring within automobiles, in which data transmission uses a lossless bit-wise arbitration method to compare the components’ IDs and resolve the contention between the components that attempt to transmit simultaneously.

L. Giarr´ e- Networked Control Systems 2020-2021 - 31

Applications: Information networks in vehicles

I Automobiles: modern cars contain several electronic control

units (ECU); some of these form independent subsystems, but

communication among others is essential, e.g., a subsystem

may need to communicate with other subsystems, transmit

control signals to actuators or receive measurement from

sensors.

I Subsequently:

I In network protocols for industrial control (such as CAN), each component is effectively allocated only a small portion of the channel and, hence, the low resolution feedback can only supply very limited information, and might induce large information loss.

I In-vehicle networking, in which computing and communication resources are shared, engineers will have to deal with issues related to scheduling, congestion, data loss and network delays.

I High-end luxury vehicles contain more that 4.8 kilometers and nearly 90 kilograms of wiring (!), and the resulting number of connectors creates a reliability nightmare. The increasing demand for high-end infotainment solutions have led vehicle manufacturers and suppliers to realize that CAN alone will no longer be sufficient to cater for every application.

L. Giarr´ e- Networked Control Systems 2020-2021 - 33

I Wireless communication technology:

I reliability and the time determinism of data transmissions are more difficult to guarantee

I The assumption that the data collected are accurate, timely, and lossless is no longer valid for such systems

The shift from wired to wireless communication channels has

highlighted important potential application advantages as well

as several challenging problems for current research.

Overview

I World is increasingly more information-rich and performance-driven.

I Growing recognition: networked feedback and cyber-physical systems.

I Control and communication, the two cornerstones of modern technologies, should be integrated ever more closely, and that the design of new engineering systems and networks can benefit from the fusion of control and communication theories.

I Many challenges unexplored in the past:

I In a NCS, the sensor and actuator signals are transmitted through certain communication links. Since information transmission cannot be ideal and is in general noisy and constrained, the communication constraints and transmission losses are likely to impede control performance

L. Giarr´ e- Networked Control Systems 2020-2021 - 35