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Controlo por Computador 0-Course presentation 1
J. Miranda Lemos IST-DEEC, Área Científica de Sistemas, Decisão e Controlo
Controlo por Computador
Computer Control
Introduction to design for Cyber-Physical Systems
J. Miranda Lemos
Professor Catedrático do IST
2015
Controlo por Computador 0-Course presentation 2
J. Miranda Lemos IST-DEEC, Área Científica de Sistemas, Decisão e Controlo
Documents that support the course
Available at the course web page (Fénix):
Slides
Laboratory guide and auxiliary documents
Problems for self-study
Other (Solution to selected problems, papers, etc.)
Available at the IST Library (complements):
Franklin, Powell, Workman, Digital Control of Dynamic Systems.
Astrom, Wittenmark, Computer Controlled Systems
Other references
Controlo por Computador 0-Course presentation 3
J. Miranda Lemos IST-DEEC, Área Científica de Sistemas, Decisão e Controlo
Student evaluation and grading
Theory
o 2 tests (recommended) or 1 exam; Weight: 50%
o Minimum 9,3 in the test average or exam;
o No minimum in each test
o After succeeding in the tests it is possible to attend the exam.
Counts only the best. Not possible to recover individual tests
Lab
o 2 reports; Weight: 50%; No minimum grade. Accepted: grades from last 2 years
Final
o F=0,5 T+0.5 min(T+4, L)
o Approval: round(F) >= 10 and T >= 9,3
Controlo por Computador 0-Course presentation 4
J. Miranda Lemos IST-DEEC, Área Científica de Sistemas, Decisão e Controlo
What is the course about?
What do you expect to learn?
Why are you here?
Controlo por Computador 0-Course presentation 5
J. Miranda Lemos IST-DEEC, Área Científica de Sistemas, Decisão e Controlo
Computer Controlled Systems
u yD/A
A/D Sensor
Sistema a Controlar
Porto de Saída
Controlador
Porto de Entrada
Computador de Controlo
Actuator
Command
signal
Output
Physical
variable
Signal proportional to
the output variable
Command signal
(numeric)
Control Algorithm
Output port
Input port
Control computer
Plant to control
The subject of
this course
Controlo por Computador 0-Course presentation 6
J. Miranda Lemos IST-DEEC, Área Científica de Sistemas, Decisão e Controlo
Embedded Control Systems
Embedded control systems consist of an unit that comprise all the hardware
and software required to form a control system.
Microcontrollers form a first step towards embedded control systems.
Example of a microcontroller
Modern microelectronic technology provide the possibility of increasing the
degree of embedding, with units that can be embedded with the physical
systems themselves. Applications: electrical machines, automotive, …
Controlo por Computador 0-Course presentation 7
J. Miranda Lemos IST-DEEC, Área Científica de Sistemas, Decisão e Controlo
Cyber-Physical Systems
Cyber-physical systems combine physical parts of the system with
computational parts.
Example: A cyber physical spring
Linearmotor
Sensors
A B
Algorithm ina computer
From the signal read from the sensors
(displacement, force) the algorithm in the
computer computes the excitation of the
linear motor such that from A to B the
device behaves as a spring.
Controlo por Computador 0-Course presentation 8
J. Miranda Lemos IST-DEEC, Área Científica de Sistemas, Decisão e Controlo
An example of application to a medical device
Cyber-physical systems include:
Control
Communication
Fault tolerance and security
Reconfiguration
IEEE Control Systems Magazine
February 2015 (vol 35, nº 1) dedicated
to Cyberphysical security
Access through IEEExplore
Controlo por Computador 0-Course presentation 9
J. Miranda Lemos IST-DEEC, Área Científica de Sistemas, Decisão e Controlo
The ingredients
Models
Identification algorithms (from plant data to models)
Control algorithms (from models to systematic decision of the value of
manipulated variables)
Controlo por Computador 0-Course presentation 10
J. Miranda Lemos IST-DEEC, Área Científica de Sistemas, Decisão e Controlo
Models for Computer Controlled Systems
A model represents the way the system reacts to an input.
Models:
Transfer function and linear difference equation (linear)
𝑦(𝑘 + 1) = 0,5𝑦(𝑘) + 3𝑢(𝑘)
State-space (linear and non-linear)
In this course we mainly consider linear design, but some techniques can be
used to solve nonlinear problems.
t t
u y ?
Plant
Controlo por Computador 0-Course presentation 11
J. Miranda Lemos IST-DEEC, Área Científica de Sistemas, Decisão e Controlo
Identification: Building models from plant i/o data
Model: )2()1()2()1()( 1021 tubtubtyatyaty
Problem: A partir das amostras de u e y , estimar os parâmetros a bi j,
u y
ESTIMADOR
Sistema a
Identificar
Controlo por Computador 0-Course presentation 12
J. Miranda Lemos IST-DEEC, Área Científica de Sistemas, Decisão e Controlo
Controllers for computer controlled systems
Linear controllers
o State-space based
o Input/output based 𝑢(𝑘) = 𝑘1𝑦(𝑘) + 𝑘2𝑦(𝑘 − 1) + 𝑘3𝑢(𝑘 − 1)
Optimal control (Dynamic Programming).
How to go from A to B with a minimum effort?
Stochastic control
Counteract stochastic disturbances
Predictive control (MPC, Receding Horizon Control)
Make decisions about control moves based on predictions over a sliding
horizon and cost optimization
Controlo por Computador 0-Course presentation 13
J. Miranda Lemos IST-DEEC, Área Científica de Sistemas, Decisão e Controlo
A mosaic of possible application areas
From aerospace to agriculture there is no limit to the areas where you can
apply the techniques studied in this course:
Get data with sensors,
Identify a model from data,
Design a controller from the model,
Connect your controller to the sensors and the actuators to obtain on-line (real time) decisions to manage the process.
Controlo por Computador 0-Course presentation 14
J. Miranda Lemos IST-DEEC, Área Científica de Sistemas, Decisão e Controlo
More (unconventional) application areas
Traffic control in communication networks
Computers and computing systems
Medical systems (figure refers to control of anesthesia)
Security of networked control systems o Mars path finder o Large power systems o Integrated circuits
Controlo por Computador 0-Course presentation 15
J. Miranda Lemos IST-DEEC, Área Científica de Sistemas, Decisão e Controlo
Schematic view of a networked control system under attack
Teixeira et al., Secure Control Systems, IEEE Control Systems Magazine, Feb 2015, 36(1):24-45
Physicalplant
Feedbackcontroller
Anomalydetector
Attack Attack
Communicationnetwork
Communicationnetwork
u(k)+u(k)
y(k)+y(k)
y(k)
y(k)u(k)
u(k)
||residue|| > Threshold => alarm
Controlo por Computador 0-Course presentation 16
J. Miranda Lemos IST-DEEC, Área Científica de Sistemas, Decisão e Controlo
A global view of engineering
The course on Computer Control provides an integration tool to the different
components of engineering design.
Understandthe process
Modelling,Controller
design
Communications
Instrumentation,sensors andtransducers
Basicphysico-chemicalphenomena
Computerarchitecture
Electronics,embedded systems
Productionobjectives
Energyoptimization
Processoptimization
Interface withmanagement
Qualityrequirements
Controlo por Computador 0-Course presentation 17
J. Miranda Lemos IST-DEEC, Área Científica de Sistemas, Decisão e Controlo
What type of course is this?
Boltzman: Nothing is more practical than a good theory.
FundamentalConcepts
Designinsight
Thiscourse
Basic conceptsMathematical manipulationsAlgorithm deductionAlgorithm propertiesAnalysis tools (stability, convergence)
Design optionsModel structure choiceSpecificationsController structure choice
Options: The noblepart of engineering
Controlo por Computador 0-Course presentation 18
J. Miranda Lemos IST-DEEC, Área Científica de Sistemas, Decisão e Controlo
Conclusion
The course on Computer control provides
A top view on design that combines o Physical systems o Information technology
The basic tools from Systems, Decision and Control A wide range of applications, with strong socio-economic impact can be addressed by mastering the course. The course follows a structure and content that is common to all the reference engineering schools in the world.
Controlo por Computador 0-Course presentation 19
J. Miranda Lemos IST-DEEC, Área Científica de Sistemas, Decisão e Controlo
Syllabus
1. Structure of computer controlled systems
2. Models for computer controlled systems
3. Model Identification
4. Controller design
a) Linear state variables feedback
b) Output feedback with polynomial methods
c) Stochastic control and Model Predictive Control (MPC)
d) Dynamic Programming
1st Test
2nd
Test
Controlo por Computador 0-Course presentation 20
J. Miranda Lemos IST-DEEC, Área Científica de Sistemas, Decisão e Controlo
Previous knowledge required
Basic knowledge about signals and systems, including
o Time and frequency representation of signals
o Laplace transform
o Transfer function, Bode diagrams and frequency response
Basic knowledge about calculus and differential equations
Basic course on Control as given in the first cycle of MEEC
Strong interest on the topic
Controlo por Computador 0-Course presentation 21
J. Miranda Lemos IST-DEEC, Área Científica de Sistemas, Decisão e Controlo
Laboratory project: Computer control of a flexible robot joint
Objective: Drive the motor such that the tip of the flexible bar tracks a
reference.
Part 1: System identification to obtain a model suitable to controller design
Part 2: Controller design and testing
MD/A
A/D 0
A/D 1
PA
Shaftangular position
Bardeflection
Gear box
Direction ofzero angularposition
Controlo por Computador 0-Course presentation 22
J. Miranda Lemos IST-DEEC, Área Científica de Sistemas, Decisão e Controlo
Main difficulty: What is the order of the system?
A continuum of metal yields an infinite dimensional model.
We need a finite dimensional model for controller design!
M
M
M
M
2nd order
4th order
6th order
8th order
Controlo por Computador 0-Course presentation 23
J. Miranda Lemos IST-DEEC, Área Científica de Sistemas, Decisão e Controlo
Physical Laws Plant i/o data
Basic principlemodels
Data basedmodels,fitted to data
Model orderreduction andapproximation
Overallplant model
This course
Experi-ments
Identifi-cation
i/o data
Model
NoModelvalid?
Yes
Specifi-cations
Controllerdesign
Verifica-tion
Design CycleApproaches to model building
La
b. P
art
1
La
b P
art
2
Controlo por Computador 0-Course presentation 24
J. Miranda Lemos IST-DEEC, Área Científica de Sistemas, Decisão e Controlo
Reprodução de uma gravura de Francisco Goya (1746-1828)
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