ESE406/505-MEAM513: Lecture 1 Introduction to Feedback and Control Ali Jadbabaie January 11, 2005 Goals: Give an overview of the course; describe course structure, administration Define feedback/control systems and learn how to recognize main features Describe what control systems do and the primary principles of control Reading (available on course web page): Astrom and Murray, Analysis and Design of Feedback Systems, Ch 1 “For the Spy in the Sky, New Eyes”, NY Times, June 2002.
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Transcript
ESE406/505-MEAM513: Lecture 1 Introduction to Feedback and Control
Ali Jadbabaie
January 11, 2005
Goals:Give an overview of the course; describe course structure, administration Define feedback/control systems and learn how to recognize main featuresDescribe what control systems do and the primary principles of control
Reading (available on course web page): Astrom and Murray, Analysis and Design of Feedback Systems, Ch 1“For the Spy in the Sky, New Eyes”, NY Times, June 2002.
January 11, 2005 2
Course AdministrationAnnouncements :
•First class is on Tuesday January 13th 2004 in Towne 313 from 12:00-1:30pm.
Course Description: This course is an introduction to analysis and design of feedback control systems, including classical control theory in the time and frequency domain. Modeling of physical, biological and information systems using linear and nonlinear differential equations. Stability and performance of interconnected systems, including use of block diagrams, Bode plots, Nyquist criterion, and Design of feedback controllers. Suggested pre-requisites: Basic course on ordinary differential equations and linear algebra. For Systems Engineering Students: knowledge of ESE 210 (SYS 200) material.For EE students: Knowledge of signals and systems (ESE 325)Instructor:
•Feedback Control of Dynamic Systems, by Franklin, Powell and Emami Naieni, 4th Edition, Prentice Hall, 2002. Other References:
•Modern Control Engineering, 4th Edition, by K. Ogata, Prentice Hall, 2001 •Modern Control Systems, 9th Edition, by Dorf and Bishop, Prentice Hall, 2001. •Automatic Control Systems, by B. Kuo, Prentice Hall, 1995.
Course Notes and Links Reading material for the class will be posted on blackboardRequired reading sources
•R. M. Murray (ed), Control in an Information Rich World: Report of the Panel on Future Directions in Control, Dynamics, and Systems, SIAM, 2002. Available online at http://www.cds.caltech.edu/~murray/cdspanel/ •K. J. Åström and Richard M. Murray, Analysis and Design of Feedback Systems, Preprint, 2004. Online access on blackboard•J. Doyle, B. Francis, and A. Tannenbaum, Feedback Control Theory, McMillan, 1992. Online access on blackboard
•Grading : Homeworks : 20% Midterm I: 35% Midterm II : 45% •Teaching assistants: Nima Moshtagh , Ali Ahmadzadeh
January 11, 2005 3
Controls Course Sequence
ESE406/505-MEAM513 – Introduction to the principles and tools of control and feedbackSummarize key concepts, w/ examples of fundamental principles at work Introduce MATLAB-based tools for modeling, simulation, and analysis Introduction to control designProvide knowledge to work with control engineers in a team setting
ESE500 – Linear Systems TheoryDetailed description of state space concepts.Rigorous analysis and synthesis of time invariant and time varying
systems.
ESE 617/MEAM 613- Nonlinear Systems
• Tools and algorithms for analysis and design of nonlinear control systems
SpringFall
January 11, 2005 4
What is Feedback?
Miriam Webster: the return to the input of a part of the
output of a machine, system, or process (as for producing changes in an electronic circuit that improve performance or in an automatic control device that provide self-corrective action) [1920]
Feedback = mutual interconnection of two (or more) systemsSystem 1 affects system 2System 2 affects system 1Cause and effect is tricky; systems
are mutually dependent
Feedback is ubiquitous in natural and engineered systems
Terminology
System 2
System 1
System 2System 1
System 2System 1
ClosedLoop
OpenLoop
January 11, 2005 5
What do these two have in common?
Tornado Boeing 777
• Highly nonlinear, complicated dynamics!• Both are capable of transporting goods and people over long distances
BUT
• One is controlled, and the other is not.• Control is “the hidden technology that you meet every day”• It heavily relies on the notion of “feedback”
January 11, 2005 6
Example #1: Flyball Governor
“Flyball” Governor (1788) Regulate speed of steam engine Reduce effects of variations in load
(disturbance rejection) Major advance of industrial revolution
Financial SystemsMarkets and exchangesSupply and service chains
ESE
January 11, 2005 8
Control = Sensing + Computation + Actuation
SenseVehicle Speed
ComputeControl “Law”
ActuateGas Pedal
In Feedback “Loop”
GoalsStability: system maintains desired operating point (hold steady speed)Performance: system responds rapidly to changes (accelerate to 65 mph)Robustness: system tolerates perturbations in dynamics (mass, drag, etc)
January 11, 2005 9
A modern Feedback Control System
January 11, 2005 10
Two Main Principles of Control
Robustness to Uncertainty through FeedbackFeedback allows high performance in the
presence of uncertaintyExample: repeatable performance of
amplifiers with 5X component variationKey idea: accurate sensing to compare
actual to desired, correction through computation and actuation
Design of Dynamics through FeedbackFeedback allows the dynamics of a
system to be modifiedExample: stability augmentation for highly
Horizontal decompositionEach level is decentralized and asynchronous
January 11, 2005 35
IP IPIP IP IP
TCP
Application
TCP
Application
TCP
Application
RoutingProvisioningHorizontal decomposition
Ver
tica
l dec
ompo
siti
on• Entirely different from the telephone system, although the parts are essentially identical (VLSI, copper, and fiber)• The Internet is much more like biology and relies on feedback regulation at every level.• Only recently has a coherent theory of the Internet started to emerge and pay off.
January 11, 2005 36
Internet
Link
IP
TCP
Application
Simplify
DeviceBoard
Computer
OperatingSystem
IP
TCP
Application
Interface
January 11, 2005 37
Sources
Links
January 11, 2005 38
Hosts
Routers
packets
January 11, 2005 39
Hosts
Routers
packets
Hidden from the user
Files
January 11, 2005 40
Hosts
Routers
packets
January 11, 2005 41
Hosts
Routers
packets
January 11, 2005 42
Control Tools
Modeling Input/output representations for subsystems +
interconnection rulesSystem identification theory and algorithms Theory and algorithms for reduced order modeling
+ model reduction
AnalysisStability of feedback systems, including
robustness “margins”Performance of input/output systems (disturbance
rejection, robustness)
SynthesisConstructive tools for design of feedback systemsConstructive tools for signal processing and
estimation (Kalman filters)
MATLAB Toolboxes SIMULINK Control System Neural Network Data Acquisition Optimization Fuzzy Logic Robust Control Instrument Control Signal Processing LMI Control Statistics Model Predictive Control System Identification µ-Analysis and
Synthesis
January 11, 2005 43
Magic of Feedback
• Feedback is used to regulate the value of a quantity in a system to a desired level, by measuring the error, i.e., difference between the desired value and the sensed value.
•Sometimes the decision is based on the instantaneous value of error, and sometimes is based on the history of the error, and/or predictions on the future value of the error. Some times we use all three.
•The performance of a feedback system is measured based on the response to a “step” change in the reference, or in tracking a sinusoid.
• Feedback regulation will work even when the “components” are uncertain.
• The down side of using feedback is that It can cause instability It makes the design more complicated
• The main components of a feedback loop are sensing, decision/computation, and actuation.• We will use theory of differential equations, linear algebra and complex variables to analyze feedback systems.
January 11, 2005 44
Overview of the Course
Wk Tue/Thur
1 Introduction to Feedback and Control
2-3 System Modeling/Analysis, Review of ODEs, and Laplace Transform
4-5 Stability and Performance
6-7 Tests for stability
8-9 Root locus analysis. Design for time domain specs.
10-11
Frequency Domain Design: Bode plot.
12-14
Loop Analysis of Feedback Systems. Nyquist criterion
15 Fundamental Limits on Performance
16 Uncertainty Analysis and Robustness
January 11, 2005 45
Summary: Introduction to Feedback and Control
Sense
Compute
Actuate
Control =
Sensing + Computation +Actuation
Feedback PrinciplesRobustness to UncertaintyDesign of Dynamics
Many examples of feedback and control in natural & engineered systems:
BIO
BIOESE
ESE
CS
January 11, 2005 46
Summary
Feedback control is Every where you just have to look for it