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Introduction to Control Systems
Prof. Marian S. StachowiczLaboratory for Intelligent Systems ECE
Department, University of Minnesota Duluth
January 19 - 21, 2010 ECE 3151 - Spring 2010
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Outline
1.1 Introduction 1.2 References for Reading1.3 History of
Automatic Control 1.4 Terms and Concepts1.5 The Control System
Design Process1.6 Applications1.7 Three Examples of the Use of
Feedback
Control Systems
Control Systems
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Introduction
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ControlThe word control is usually taken to mean :- regulate, -
direct, - command.Control Systems
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Control and politiciansControl is a sequence of decisions aimed
at the attainment of specified objectives in an environment of
uncertainty and presence of disturbances.Control Systems
Control Systems
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Control systemA control system is an arrangement of physical
components connected or related in such a manner as to command,
direct, or regulate itself or another system.Control Systems
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Control Systems
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InputThe input is the stimulus, excitation or command applied to
a control system.
Typically from external energy source, usually in order to
produce a specified response from the control system.Control
Systems
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OutputThe output is the actual response obtained from a control
system.
It may or may not be equal to specified response implied by the
input.Control Systems
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References for reading
R.C. Dorf and R.H. Bishop, Modern Control Systems,10th Edition,
Prentice Hall, 2008,Chapter 1.1 - 1.10
2. J.J. DiStefano, A. R. Stubberud, I. J. Williams, Feeedback
and Control Systems, Schaum's Outline Series, McGraw-Hill, Inc.,
1990Chapters 1, 2 Control Systems
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History of Automatic ControlControl Systems
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Prior to World War IIA main impetus for the use of feedback in
the United States was the development of the telephone system and
electronic feedback amplifiers by Bode, Nyquist, and Black at Bell
Telephone Laboratories.Control Systems
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Prior to World War IIThe Russian theory tended to utilize a
time-domain formulation using differential equations. Control
Systems
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World War IIDesign and construct:automatic airplane pilots,
gun-positioning systems, radar antenna control systems. Control
Systems
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Sputnik and space ageThe time-domain methods developed by
Liapunov, Minorsky, and others have met with great interest in the
last two decades.
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Resent timeRecent theories of optimal control developed by L.S.
Pontryagin in the former Soviet Union and R. Bellman in the United
States, and studies of robust systems, have contributed to the
interest in time-domain methods.Control Systems
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Terms and Concepts
Control Systems
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Control systemA control system is an interconnection of
components forming a system configuration that will provide a
desired system response.Control Systems
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Two Types of Control SystemsOpen LoopNo feedbackDifficult to
control output with accuracy
Closed LoopMust have feedbackMust have sensor on outputAlmost
always negative feedbackControl Systems
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Open-loop controlAn open-loop control system utilizes an
actuating device to control the process directly without using
feedback.
A common example of an open-loop control system is an electric
toaster in the kitchen.Control Systems
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Control Systems
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Closed-loop control
A closed-loop control system uses a measurement of the output
and feedback of this signal to compare it with the desired
output.
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Control Systems
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A person steering an automobile by looking at the autos location
on the road and making the appropriate adjustments. Control
Systems
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Control Systems
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Manual control systemIntelligent ControlGoal: Regulate the level
of fluid by adjusting the output valve.
The input is a reference level of fluid and is memorized by
operator.The power amplifier is the operator.The sensor is
visual.Operator compares the actual level with the desired level
and opens or closes the valve ( actuator).
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Intelligent Control
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The level of fluid in a tank control. *Intelligent Control
Intelligent Control
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Multivariable control systemControl Systems
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Control Systems
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Control Systems
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Control system of the national income.Control Systems
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A robot is a computer-controlledmachine.
Industrial robotics is a particular field of automation in which
the robot is designed to substitute for human labor. The Honda P3
humanoid robot.Control Systems
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Automation - The control of a process by automatic means.
Closed-loop feedback control system - A system that uses a
measurement of the output and compares it with the desired
output.
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Design-The process of conceiving or inventing the forms, parts,
and details of a system to achieve a specified purpose.Feedback
signal - A measure of the output of the system used for feedback to
control the system. Multivariable control system - A system with
more than one input variable or more than one output variable.
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Negative feedback -The output signal is fed back so that it
subtracts from the input signal.
Open-loop control system - A system that utilizes a device to
control the process without using feedback.
Optimization -The adjustment of the parameters to achieve the
most favorable or advantageous design. Control Systems
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Positive feedback -The output signal is fed back so that it adds
to the input signal.
Process -The device, plant, or system under control.
Productivity -The ratio of physical output to physical input of
an industrial process.
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Robot - Programmable computers integrated with a
manipulator.
Synthesis - The combining of separate elements or devices to
form a coherent whole.
System - An interconnection of elements and devices for a
desired purpose. Control Systems
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The Control System Design Process
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Design is the process of conceiving or inventing the forms,
parts, and details of a system to achieve a specified purpose.
Engineering designControl Systems
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Engineering design
Trade-off The result of making a judgment about how to
compromise between conflicting criteria.Control Systems
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Control system engineers are concerned with understanding and
controlling segments of their environment, often called systems, to
provide useful economic products.Control Systems
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GoalsTwin goals of understanding and controlling are
complementary because effective systems control requires that the
systems be understood and modeled.Control Systems
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Control engineeringControl engineering is based on the
foundations of feedback theory and linear system analysis, and it
integrates the concepts of network theory and communication
theory.Control Systems
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Given a process, how to design a feedback control system?Three
steps:
Modeling. Obtain mathematical description of the systems.
Analysis. Analyze the properties of the system.
Design. Given a plant, design a controller based on performance
specifications.
The course spans each of these steps in that sequence.
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The basis for analysis of a system is the foundation provided by
linear system theory, which assumes a cause-effect relationship for
the components of a system.Control Systems
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Control Systems
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Design examples
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Rotating disk speed controlControl Systems
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Step 1. Control goal
Design a system that will held a rotating disk at a constant
speed. Ensure that the actual speed of rotation is within a
specified percentage of desired speed.Control Systems
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Step 2. Variable to be controlled
Speed of rotation discControl Systems
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Step 3. Control design specification
Design a system that will ensure that the actual speed of
rotation is within a specified percentage of desired speed.Control
Systems
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Step 4 Preliminary system configurationControl Systems
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Step 4 Preliminary system configurationControl Systems
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With precision components, we could expect to reduce the error
of the feedback system toone-hundredth of error of the open-loop
system.
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Insulin delivery system
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The blood glucose and insulin concentrations for a healthy
person.Control Systems
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Step 1. Control goal
Design a system to regulate the blood sugar concentration of a
diabetic by controlled dispensing of insulin.Control Systems
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Step 2. Variable to be controlled
Blood glucose concentrationControl Systems
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Step 3. Control design specification
Provide a blood glucose level for the diabetic that closely
approximates the glucose level of a healthy person.Control
Systems
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Step 4 Preliminary system configurationsControl Systems
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A drug-delivery system implanted in the body uses an open-loop
system, since miniaturized glucose sensors are not yet
available.Control Systems
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Disk drive read systemControl Systems
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Control Systems
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Step 1. Control goal
Design a system that will held the position the reader head to
read the data stored on a track on the disk.Control Systems
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Step 2. Variable to be controlled
Position of the reader headControl Systems
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Step 3. Control design specification
Design a system that will ensure that the head : - flies above
the disk at a distance of less than 100 nm, - with the position
accuracy is 1 m,- with speed from track to track 50 msControl
Systems
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Step 4 Preliminary system configurationControl Systems
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E 1: Controlling the position of a missile launcher from a
remote locationThe input is the desired angular position of the
missile launcher, The control system consists:of potentiometer,
power amplifier, motor, gearing between the motor and the missile
launcher,missile launcher.Control Systems
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A position open loop controlThe input is the desired angular
position of the missile launcher, and the control system consists
of potentiometer, power amplifier, motor, gearing between the motor
and missile launcher, and missile launcher.
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A position closed loop controlShould an error exists, it is
amplified and applied to a motor drive which adjusts the
output-shaft position until it agrees with the input-shaft
position, and the error is zero.
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P1.2 Manual control systemControl Systems
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Fluid-flow controlP1.2In the past, control systems used a human
operator as part of a closed-loop control system. Sketch the block
diagram of the valve control system shown in Fig. P1.2
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P1.3 Chemical composition controlComplete the control feedback
loop, and sketch a block diagram describing the operation of the
control loop. Control Systems
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Control Systems
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P1.8 Student-teacher learning process
Construct a feedback model of the learning process and identify
each block of the system. Control Systems
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Inverted pendulum controlE1.11 Sketch the block diagram of a
feedback control system. Identify the process, sensor, actuator,
and controller.The objective is keep the pendulum in the upright
position ( = 0), in the presence of disturbances. Control
Systems
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Control Systems
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ApplicationsControl engineering is not limited to any
engineering discipline but is equally applicable to:
aeronautical,chemical,mechanical,computer science and engineering ,
civil engineering,electrical engineering.Control Systems
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Mechatronic systemsControl Systems
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Questions ?
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Control Systems
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Control Systems
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Control SystemsThe design of control systems is a specific
example of engineering design. The goal of control engineering
design is to obtain the configuration, specifications, and
identification of the key parameters of a proposed system to meet
an actual need.
Control Systems
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Control SystemsThe design process consists of seven main
building blocks, which are arrange into three groups:Establishment
of goals and variables to be controlled, and definition of
specifications against which to measure performanceSystem
definition and modelingControl system design and integrated system
simulation and analysis
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Control Systems
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Design 1Control Systems
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Design 2Control Systems
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Design 3Control Systems
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Open-loop and closed-loop systems
* **Attainment- the achievement of the goals that somebody has
set.Prime minister of GB in 1970s (IFAC )*Figure: 01-01 represents
a block diagram of a process or component to be controlled. The
input - output relationship represents the cause-effect
relationship of the process, which represents a processing of the
input signal to provide an output signal variable, often with power
amplification.***The eminent mathematicians and applied
mechanicians in the former Soviet Union inspired and dominated the
field of control theore. Therefore the Russian theory tended to
utilize a time-domain formulation using differential equations.
*******A microwave oven set to operate for a fixed time.*Figure:
01-21
**The system in Figure: 01-22 is a negative feedback control
system, because the output is subtracted from the input and the
difference is used as a the input signal to the controller.
*Figure: 01-07a-c, An example of a closed-loop control system is
a person steering an automobile (assuming his eyes are open) by
looking at the autos location on the road and making the
appropriate adjustments.*Figure: 01-08. Manual control system for
regulating the level of fluid in a tank by adjusting the output
valve. The operator views the level of fluid through a port in the
side of the tank. The input is a reference level of fluid that the
operator is instructed to maintain (this reference is memorized by
the operator). The power amplifier is the operator, and the sensor
is visual. The operator compares the actual level with the desired
level and opens or closes the valve ( actuator), adjusting the
fluid flow out, to maintain the desired level.*Figure:
01-04*Figure: 01-10, A three-axis control system for inspecting
individual semiconductor wafers with a highly sensitive
camera.*Figure: 01-11 Coordinated control system for a
boiler-generator. This is an example of the importance of measuring
many variables, such as oxygen, temperature, pressure, and
generation, to provide information to the computer for control
calculations.Another important industry, the metallurgical
industry, has had considerable success in automatically controlling
its processes.A hot-strip steel mill is controlled for temperature,
strip width, thickness, and quality.*Figure: 01-13. It has become
interesting and valuable to attempt to model the feedback processes
prevalent in the social, economic, and political spheres.*Figure:
01-09***Open-loop control system - The output has no effect upon
the signal to the process.* ********Figure: 01-15**Many modern
devices employ a rotating disk held at a constant speed. A CD
player requires a constant speed of rotation in spite of motor wear
and variation and other components changes.
*To obtain disk rotation, we will select a DC motor as the
actuator because it provides a speed proportional to the applied
motor voltage. For the input voltage to the motor, we will select
an amplifier that can provide the required power.*In next chapters,
we will have the tools to quantitatively describe the control
design specifications using a variety of steady-state performance
specifications and transit response specifications, both in the
time-domain and in the frequency domain.*Given the design goals,
variables to be controlled, and control design specification we can
now propose a preliminary system configuration.An open-loop system
would use a battery source to provide a voltage that is
proportional to the desired speed as shown in Fig. 1.21a. This
voltage is amplified and applied to the motor. *Figure: 01-21*The
system in Figure: 01-22 is a negative feedback control system,
because the output is subtracted from the input and the difference
is used as a the input signal to the controller.The feedback
control system would use a tachometer as a sensor that provides an
output voltage proportional to the speed of its shaft. The error
voltage is generated by the difference between the input voltage
and the tachometer voltage.as shown in Fig. 1.22a.We expect the
feedback system to be superior to the open-loop system because the
feedback system will respond to errors and act to reduce them.With
precision components, we could expect to reduce the error of the
feedback system to one-hundredth of error of the open-loop
system
**Automatic system can be used to regulate blood pressure, blood
sugar level, and heart rate. *Figure: 01-23. The blood glucose and
insulin concentrations for a healthy person.**In next chapters, we
will have the tools to quantitatively describe the control design
specifications using a variety of steady-state performance
specifications and transit response specifications, both in the
time-domain and in the frequency domain.*Given the design goals,
variables to be controlled, and control design specification we can
now propose a preliminary system configuration.An open-loop system
would use a preprogrammed signal generator and miniature motor pomp
to regulate the insulin delivery rate as shown in Fig. 1.24 a. The
feedback control system would use a sensor to measure the actual
glucose level and compare that level with the desired level, thus
turning the motor pump on when it is required as shown in Fig. 1.24
b*Figure: 01-24 Open-loop system for drug delivery, in which
mathematical models of the dose-effect relationship of the drugs
are used.The best solutions rely on individually, pocket-sized
insulin pumps that can deliver insulin according to a preset time
history. More complicate systems will use closed-loop control for
the measured blood glucose level.
**Sequential design example will be considered in each chapter
our textbook.*Figure: 01-26 Designers are now considering employing
disk drives to perform task historically delegated to CPU.Three
areas are under investigation: off-line error recovery, disk drive
failure warning, storing data across multiple disk drives.Note: The
disk rotates at a speed between 1800 and 7200 rpm. *To obtain disk
rotation, we will select a DC motor as the actuator because it
provides a speed proportional to the applied motor voltage. For the
input voltage to the motor, we will select an amplifier that can
provide the required power.*In next chapters, we will have the
tools to quantitatively describe the control design specifications
using a variety of steady-state performance specifications and
transit response specifications, both in the time-domain and in the
frequency domain.*Given the design goals, variables to be
controlled, and control design specification we can now propose a
preliminary system configuration.This proposed closed-loop system
uses a motor to actuate (move) the arm to the desired location on
the disk.*Figure: 01-27***The previous example is modified by
introducing a position feedback loop.*Figure: 01-08. Manual control
system for regulating the level of fluid in a tank by adjusting the
output valve.The operator views the level of fluid through a port
in the side of the tank. The input is a reference level of fluid
that the operator is instructed to maintain (this reference is
memorized by the operator). The power amplifier is the operator,
and the sensor is visual. The operator compares the actual level
with the desired level and opens or closes the valve ( actuator),
adjusting the fluid flow out, to maintain the desired level.The
reference is a desired level of fluid that operator is instructor
to maintain.The actuator is the valve that opens or closes the
fluid flow outThe sensor is visual.The controller is the
operator*P1.3 In a chemical process control system, it is valuable
to control the chemical composition of the product. To do so, a
measurement of the composition can be obtained by using an infrared
stream analyzer,as shown in FigureP1.3.The valve on the additive
stream may be controlled.*Figure: 01-27-04UNP1.3*P1.8 The
student-teacher learning process is inherently a feedback process
intended to reduce the system error to a minimum. With the aid of
Figure1.3, construct a feedback model of the learning process and
identify each block of the system. *Figure:
01-27-02UNE1.11**Figure: 01-16**Figure: 01-27-07UNP1.6*Figure:
01-27-08UNP1.9*Figure: 01-27-11UNP1.18The design of control systems
is a specific example of engineering design. The goal of control
engineering design is to obtain the configuration, specifications,
and identification of the key parameters of a proposed system to
meet an actual need.The design process consists of seven main
building blocks, which are arrange into three groups:Establishment
of goals and variables to be controlled, and definition of
specifications against which to measure performanceSystem
definition and modelingControl system design and integrated system
simulation and analysis
**
