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Mechatronics

MechanicalTechnology

ElectricalTechnology

ComputerTechnology

MechanicalSoftware

ElectricalSoftware

ElectroMechanical

Mechatronics with Experiments

Second Edition

Sabri Cetinkunt

MECHATRONICS

SECOND EDITION

MECHATRONICSwith Experiments

SABRI CETINKUNTUniversity of Illinois at Chicago, USA

This edition first published 2015© 2015 John Wiley & Sons Ltd

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MATLAB® is a trademark of The MathWorks, Inc. and is used with permission. The MathWorks does notwarrant the accuracy of the text or exercises in this book. This book’s use or discussion of MATLAB® softwareor related products does not constitute endorsement or sponsorship by The MathWorks of a particularpedagogical approach or particular use of the MATLAB® software.

Library of Congress Cataloging-in-Publication Data

Cetinkunt, Sabri.[Mechatronics]Mechatronics with experiments / Sabri Cetinkunt. – Second edition.

pages cmRevised edition of Mechatronics / Sabri Cetinkunt. 2007Includes bibliographical references and index.ISBN 978-1-118-80246-5 (cloth)

1. Mechatronics. I. Title.TJ163.12.C43 2015621.381–dc23

2014032267

A catalogue record for this book is available from the British Library.

ISBN: 9781118802465

Set in 10/12pt Times by Aptara Inc., New Delhi, India

1 2015

http://www.wiley.com

CONTENTS

PREFACE xi

ABOUT THE COMPANION WEBSITE xii

CHAPTER 1 INTRODUCTION 1

1.1 Case Study: Modeling andControl of Combustion Engines 16

1.1.1 Diesel EngineComponents 17

1.1.2 Engine Control SystemComponents 23

1.1.3 Engine Modeling withLug Curve 25

1.1.4 Engine ControlAlgorithms: EngineSpeed Regulationusing Fuel Map and aProportional ControlAlgorithm 29

1.2 Example: Electro-hydraulicFlight Control Systems forCommercial Airplanes 31

1.3 Embedded Control SoftwareDevelopment for MechatronicSystems 38

1.4 Problems 43

CHAPTER 2 CLOSED LOOPCONTROL 45

2.1 Components of a DigitalControl System 46

2.2 The Sampling Operation andSignal Reconstruction 48

2.2.1 Sampling: A/DOperation 48

2.2.2 Sampling Circuit 48

2.2.3 MathematicalIdealization of theSampling Circuit 50

2.2.4 Signal Reconstruction:D/A Operation 55

2.2.5 Real-time ControlUpdate Methods andTime Delay 58

2.2.6 Filtering andBandwidth Issues 60

2.3 Open Loop Control VersusClosed Loop Control 63

2.4 Performance Specifications forControl Systems 67

2.5 Time Domain and S-domainCorrelation of Signals 69

2.6 Transient ResponseSpecifications: Selection ofPole Locations 70

2.6.1 Step Response of aSecond-Order System 70

2.6.2 Standard Filters 74

2.7 Steady-State ResponseSpecifications 74

2.8 Stability of Dynamic Systems 76

2.8.1 Bounded Input–BoundedOutput Stability 77

2.9 Experimental Determination ofFrequency Response 78

2.9.1 GraphicalRepresentation ofFrequency Response 79

2.9.2 Stability Analysis inthe FrequencyDomain: NyquistStability Criteria 87

2.10 The Root Locus Method 89

2.11 Correlation Between TimeDomain and Frequency DomainInformation 93

2.12 Basic Feedback Control Types 97

2.12.1 Proportional Control 100

2.12.2 Derivative Control 101

2.12.3 Integral Control 102

2.12.4 PI Control 103

2.12.5 PD Control 106

2.12.6 PID Control 107

2.12.7 PracticalImplementation Issuesof PID Control 111

2.12.8 Time Delay in ControlSystems 117

2.13 Translation of Analog Controlto Digital Control 125

2.13.1 Finite DifferenceApproximations 126

2.14 Problems 128

v

vi CONTENTS

CHAPTER 3 MECHANISMS FORMOTION TRANSMISSION 133

3.1 Introduction 133

3.2 Rotary to Rotary MotionTransmission Mechanisms 136

3.2.1 Gears 136

3.2.2 Belt and Pulley 138

3.3 Rotary to Translational MotionTransmission Mechanisms 139

3.3.1 Lead-Screw andBall-ScrewMechanisms 139

3.3.2 Rack and PinionMechanism 142

3.3.3 Belt and Pulley 142

3.4 Cyclic Motion TransmissionMechanisms 143

3.4.1 Linkages 143

3.4.2 Cams 145

3.5 Shaft Misalignments andFlexible Couplings 153

3.6 Actuator Sizing 154

3.6.1 Inertia Match BetweenMotor and Load 160

3.7 Homogeneous TransformationMatrices 162

3.8 A Case Study: AutomotiveTransmission as a “GearReducer” 172

3.8.1 The Need for aGearbox“Transmission” inAutomotiveApplications 172

3.8.2 AutomotiveTransmission: ManualShift Type 174

3.8.3 Planetary Gears 178

3.8.4 Torque Converter 186

3.8.5 Clutches and Brakes:Multi Disc Type 192

3.8.6 Example: AnAutomaticTransmission ControlAlgorithm 194

3.8.7 Example: Powertrainof Articulated Trucks 196

3.9 Problems 201

CHAPTER 4

MICROCONTROLLERS 207

4.1 Embedded Computers versusNon-Embedded Computers 207

4.2 Basic Computer Model 214

4.3 Microcontroller Hardware andSoftware: PIC 18F452 218

4.3.1 MicrocontrollerHardware 220

4.3.2 MicroprocessorSoftware 224

4.3.3 I/O Peripherals of PIC18F452 226

4.4 Interrupts 235

4.4.1 General Features ofInterrupts 235

4.4.2 Interrupts on PIC18F452 236

4.5 Problems 243

CHAPTER 5 ELECTRONICCOMPONENTS FORMECHATRONIC SYSTEMS 245


5.2 Basics of Linear Circuits 245

5.3 Equivalent Electrical CircuitMethods 249

5.3.1 Thevenin’s EquivalentCircuit 249

5.3.2 Norton’s EquivalentCircuit 250

5.4 Impedance 252

5.4.1 Concept of Impedance 252

5.4.2 Amplifier: Gain, InputImpedance, andOutput Impedance 257

5.4.3 Input and OutputLoading Errors 258

5.5 Semiconductor ElectronicDevices 260

5.5.1 SemiconductorMaterials 260

5.5.2 Diodes 263

5.5.3 Transistors 271

5.6 Operational Amplifiers 282

5.6.1 Basic Op-Amp 282

5.6.2 Common Op-AmpCircuits 290

5.7 Digital Electronic Devices 308

5.7.1 Logic Devices 309

5.7.2 Decoders 309

5.7.3 Multiplexer 309

5.7.4 Flip-Flops 310

5.8 Digital and Analog I/O andTheir Computer Interface 314

5.9 D/A and A/D Converters andTheir Computer Interface 318

5.10 Problems 324

CONTENTS vii

CHAPTER 6 SENSORS 329

6.1 Introduction to MeasurementDevices 329

6.2 Measurement Device LoadingErrors 333

6.3 Wheatstone Bridge Circuit 335

6.3.1 Null Method 336

6.3.2 Deflection Method 337

6.4 Position Sensors 339

6.4.1 Potentiometer 339

6.4.2 LVDT, Resolver, andSyncro 340

6.4.3 Encoders 346

6.4.4 Hall Effect Sensors 351

6.4.5 Capacitive GapSensors 353

6.4.6 MagnetostrictionPosition Sensors 354

6.4.7 Sonic Distance Sensors 356

6.4.8 Photoelectic Distanceand Presence Sensors 357

6.4.9 Presence Sensors:ON/OFF Sensors 360

6.5 Velocity Sensors 362

6.5.1 Tachometers 362

6.5.2 Digital Derivation ofVelocity from PositionSignal 364

6.6 Acceleration Sensors 365

6.6.1 InertialAccelerometers 366

6.6.2 PiezoelectricAccelerometers 370

6.6.3 Strain-gauge BasedAccelerometers 371

6.7 Strain, Force, and TorqueSensors 372

6.7.1 Strain Gauges 372

6.7.2 Force and TorqueSensors 373

6.8 Pressure Sensors 376

6.8.1 Displacement BasedPressure Sensors 378

6.8.2 Strain-Gauge BasedPressure Sensor 379

6.8.3 Piezoelectric BasedPressure Sensor 380

6.8.4 Capacitance BasedPressure Sensor 380

6.9 Temperature Sensors 381

6.9.1 Temperature SensorsBased on DimensionalChange 381

6.9.2 Temperature SensorsBased on Resistance 382

6.9.3 Thermocouples 383

6.10 Flow Rate Sensors 385

6.10.1 Mechanical Flow RateSensors 385

6.10.2 Differential PressureFlow Rate Sensors 387

6.10.3 Flow Rate SensorBased on Faraday’sInduction Principle 389

6.10.4 Thermal Flow RateSensors: Hot WireAnemometer 390

6.10.5 Mass Flow RateSensors: Coriolis FlowMeters 391

6.11 Humidity Sensors 393

6.12 Vision Systems 394

6.13 GPS: Global Positioning System 397

6.13.1 Operating Principles ofGPS 399

6.13.2 Sources of Error inGPS 402

6.13.3 Differential GPS 402

6.14 Problems 403

CHAPTER 7 ELECTROHYDRAULICMOTION CONTROL SYSTEMS 407


7.2 Fundamental PhysicalPrinciples 425

7.2.1 Analogy BetweenHydraulic andElectrical Components 429

7.2.2 Energy Loss andPressure Drop inHydraulic Circuits 431

7.3 Hydraulic Pumps 437

7.3.1 Types of PositiveDisplacement Pumps 438

7.3.2 Pump Performance 443

7.3.3 Pump Control 448

7.4 Hydraulic Actuators: HydraulicCylinder and Rotary Motor 457

7.5 Hydraulic Valves 461

7.5.1 Pressure ControlValves 463

7.5.2 Example: MultiFunction HydraulicCircuit with PoppetValves 469

7.5.3 Flow Control Valves 471

viii CONTENTS

7.5.4 Example: A MultiFunction HydraulicCircuit usingPost-PressureCompensatedProportional Valves 482

7.5.5 Directional,Proportional, andServo Valves 484

7.5.6 Mounting of Valves ina Hydraulic Circuit 496

7.5.7 PerformanceCharacteristics ofProportional and ServoValves 497

7.6 Sizing of Hydraulic MotionSystem Components 507

7.7 Hydraulic Motion Axis NaturalFrequency and Bandwidth Limit 518

7.8 Linear Dynamic Model of aOne-Axis Hydraulic MotionSystem 520

7.8.1 Position ControlledElectrohydraulicMotion Axes 523

7.8.2 Load PressureControlledElectrohydraulicMotion Axes 526

7.9 Nonlinear Dynamic Model ofOne-Axis Hydraulic MotionSystem 527

7.10 Example: Open CenterHydraulic System – Force andSpeed Modulation Curves inSteady State 571

7.11 Example: HydrostaticTransmissions 576

7.12 Current Trends inElectrohydraulics 586

7.13 Case Studies 589

7.13.1 Case Study: MultiFunction HydraulicCircuit of a CaterpillarWheel Loader 589

7.14 Problems 593

CHAPTER 8 ELECTRICACTUATORS: MOTOR AND DRIVETECHNOLOGY 603


8.1.1 Steady-StateTorque-Speed Range,Regeneration, andPower Dumping 606

8.1.2 Electric Fields andMagnetic Fields 610

8.1.3 Permanent MagneticMaterials 622

8.2 Energy Losses in ElectricMotors 629

8.2.1 Resistance Losses 631

8.2.2 Core Losses 632

8.2.3 Friction and WindageLosses 633

8.3 Solenoids 633

8.3.1 Operating Principles ofSolenoids 633

8.3.2 DC Solenoid:ElectromechanicalDynamic Model 636

8.4 DC Servo Motors and Drives 640

8.4.1 Operating Principles ofDC Motors 642

8.4.2 Drives for DCBrush-type andBrushless Motors 650

8.5 AC Induction Motors and Drives 659

8.5.1 AC Induction MotorOperating Principles 660

8.5.2 Drives for ACInduction Motors 666

8.6 Step Motors 670

8.6.1 Basic Stepper MotorOperating Principles 672

8.6.2 Step Motor Drives 677

8.7 Linear Motors 681

8.8 DC Motor: ElectromechanicalDynamic Model 683

8.8.1 Voltage AmplifierDriven DC Motor 687

8.8.2 Current AmplifierDriven DC Motor 687

8.8.3 Steady-StateTorque-SpeedCharacteristics of DCMotor Under ConstantTerminal Voltage 688

8.8.4 Steady-StateTorque-SpeedCharacteristic of a DCMotor Under ConstantCommanded CurrentCondition 689

8.9 Problems 691

CHAPTER 9 PROGRAMMABLELOGIC CONTROLLERS 695


CONTENTS ix

9.2 Hardware Components ofPLCs 697

9.2.1 PLC CPU and I/OCapabilities 697

9.2.2 Opto-isolatedDiscrete Input andOutput Modules 701

9.2.3 Relays, Contactors,Starters 701

9.2.4 Counters and Timers 704

9.3 Programming of PLCs 705

9.3.1 Hard-wired Seal-inCircuit 708

9.4 PLC Control SystemApplications 709

9.4.1 Closed LoopTemperature ControlSystem 709

9.4.2 Conveyor SpeedControl System 710

9.4.3 Closed Loop ServoPosition ControlSystem 711

9.5 PLC Application Example:Conveyor and Furnace Control 712

9.6 Problems 714

CHAPTER 10 PROGRAMMABLEMOTION CONTROL SYSTEMS 717


10.2 Design Methodology for PMCSystems 722

10.3 Motion Controller Hardwareand Software 723

10.4 Basic Single-Axis Motions 724

10.5 Coordinated Motion ControlMethods 729

10.5.1 Point-to-pointSynchronized Motion 729

10.5.2 Electronic GearingCoordinated Motion 731

10.5.3 CAM Profile andContouringCoordinated Motion 734

10.5.4 Sensor BasedReal-timeCoordinated Motion 735

10.6 Coordinated MotionApplications 735

10.6.1 Web Handling withRegistration Mark 735

10.6.2 Web Tension ControlUsing ElectronicGearing 738

10.6.3 Smart Conveyors 741

10.7 Problems 747

CHAPTER 11 LABORATORYEXPERIMENTS 749

11.1 Experiment 1: Basic ElectricalCircuit Components andKirchoff’s Voltage andCurrent Laws 749

Objectives 749

Components 749

Theory 749

Procedure 751

11.2 Experiment 2: TransistorOperation: ON/OFF Modeand Linear Mode of Operation 754

Objectives 754

Components 754

Theory 754

Procedure 756

11.3 Experiment 3: PassiveFirst-Order RC Filters: LowPass Filter and High Pass Filter 758

Objectives 758

Components 758

Theory 758

Procedure 760

11.4 Experiment 4: ActiveFirst-Order Low Pass Filterwith Op-Amps 762

Objectives 762

Components 762

Theory 762

Procedure 765

11.5 Experiment 5: Schmitt TriggerWith Variable Hysteresisusing an Op-Amp Circuit 766

Objectives 766

Components 766

Theory 767

Procedure 768

11.6 Experiment 6: Analog PIDControl Using Op-Amps 770

Objectives 770

Components 770

Theory 770

Procedure 774

11.7 Experiment 7: LED ControlUsing the PIC Microcontroller 775

Objectives 775

Components 776

x CONTENTS

Theory 776

Application SoftwareDescription 777

Procedure 777

11.8 Experiment 8: Force andStrain Measurement Using aStrain Gauge and PIC-ADCInterface 780

Objectives 780

Components 781

Theory 781


Procedure 785

11.9 Experiment 9: SolenoidControl Using a Transistor andPIC Microcontroller 787

Objectives 787

Components 787

Theory 787

Hardware 787


Procedure 788

11.10 Experiment 10: Stepper MotorMotion Control Using a PICMicrocontroller 790

Objective 790

Components 790

Theory 790


Procedure 793

11.11 Experiment 11: DC MotorSpeed Control Using PWM 794

Objectives 794

Components 794

Theory 794


Procedure 796

11.12 Experiment 12: Closed LoopDC Motor Position Control 799

Objectives 799

Components 799

Theory 799


Procedure 804

APPENDIX MATLAB®,SIMULINK®, STATEFLOW, ANDAUTO-CODE GENERATION 805

A.1 MATLAB® Overview 805

A.1.1 Data in MATLAB®

Environment 808

A.1.2 Program Flow ControlStatements inMATLAB® 813

A.1.3 Functions inMATLAB®: M-scriptfiles and M-functionfiles 815

A.1.4 Input and Output inMATLAB® 822

A.1.5 MATLAB® Toolboxes 831

A.1.6 Controller DesignFunctions: TransformDomain andState-Space Methods 832

A.2 Simulink® 836

A.2.1 Simulink® BlockExamples 843

A.2.2 Simulink®

S-Functions in CLanguage 852

A.3 Stateflow 856

A.3.1 Accessing Data andFunctions from aStateflow Chart 865

A.4 Auto Code Generation 876

REFERENCES 879

INDEX 883

PREFACE

This second edition of the textbook has the following modifications compared to the firstedition:

� Twelve experiments have been added. The experiments require building of electronicinterface circuits between the microcontroller and the electromechanical system,writing of real-time control code in C language, and testing and debugging thecomplete system to make it work.

� All of the chapters have been edited and more examples have been added whereappropriate.

� A brief tutorial on MATLAB®/Simulink®/Stateflow is included.

I would like to thank Paul Petralia, Tom Carter and Anne Hunt [Acquisitions Editor,Project Editor and Associate Commissioning Editor, respectively] at John Wiley and Sonsfor their patience and kind guidance throughout the process of writing this edition ofthe book.

Sabri CetinkuntChicago, Illinois, USA

March 19, 2014

xi

ABOUT THE COMPANION WEBSITE

This book has a companion website:

www.wiley.com/go/cetinkunt/mechatronics

The website includes:

� A solutions manual

xii

www.wiley.com/go/cetinkunt/mechatronics

http://www.wiley.com/go/cetinkunt/mechatronics

JWST499-c01 JWST499-Cetinkunt Printer: Yet to Come October 9, 2014 7:39 254mm×178mm

CHAPTER 1INTRODUCTION

THE MECHATRONICS field consists of the synergistic integration of three distincttraditional engineering fields for system level design processes. These three fields are

1. mechanical engineering where the word “mecha” is taken from,

2. electrical or electronics engineering, where “tronics” is taken from,

3. computer science.

The file of mechatronics is not simply the sum of these three major areas, but can be definedas the intersection of these areas when taken in the context of systems design (Figure 1.1).It is the current state of evolutionary change of the engineering fields that deal with thedesign of controlled electromechanical systems. A mechatronic system is a computercontrolled mechanical system. Quite often, it is an embedded computer, not a generalpurpose computer, that is used for control decisions. The word mechatronics was first coinedby engineers at Yaskawa Electric Company [1,2]. Virtually every modern electromechanicalsystem has an embedded computer controller. Therefore, computer hardware and softwareissues (in terms of their application to the control of electromechanical systems) are partof the field of mechatronics. Had it not been for the widespread availability of low costmicrocontrollers for the mass market, the field of mechatronics as we know it todaywould not exist. The availability of embedded microprocessors for the mass market at everreducing cost and increasing performance makes the use of computer control in thousandsof consumer products possible.

The old model for an electromechanical product design team included

1. engineer(s) who design the mechanical components of a product,

2. engineer(s) who design the electrical components, such as actuators, sensors, ampli-fiers and so on, as well as the control logic and algorithms,

3. engineer(s) who design the computer hardware and software implementation to con-trol the product in real-time.

A mechatronics engineer is trained to do all of these three functions. In addition, the designprocess is not sequential with mechanical design followed by electrical and computer con-trol system design, but rather all aspects (mechanical, electrical, and computer control)of design are carried out simultaneously for optimal product design. Clearly, mechatron-ics is not a new engineering discipline, but the current state of the evolutionary processof the engineering disciplines needed for design of electromechanical systems. The endproduct of a mechatronics engineer’s work is a working prototype of an embedded com-puter controlled electromechanical device or system. This book covers the fundamental

Mechatronics with Experiments, Second Edition. Sabri Cetinkunt.© 2015 John Wiley & Sons, Ltd. Published 2015 by John Wiley & Sons, Ltd.Companion Website: www.wiley.com/go/cetinkunt/mechatronics

1

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2 MECHATRONICS

Mechatronics

Mechanicaltechnology

Electricaltechnology

Computertechnology

Mechanicalsoftware

Electricalsoftware

Electromechanical

FIGURE 1.1: The field of

mechatronics: intersection of

mechanical engineering,

electrical engineering, and

computer science.

technical topics required to enable an engineer to accomplish such designs. We define theword device as a stand-alone product that serves a function, such as a microwave oven,whereas a system may be a collection of multiple devices, such as an automated roboticassembly line.

As a result, this book has sections on mechanical design of various mechanismsused in automated machines and robotic applications. Such mechanisms are designs overa century old and these basic designs are still used in modern applications. Mechanicaldesign forms the “skeleton” of the electromechanical product, upon which the rest ofthe functionalities are built (such as “eyes,” “muscles,” “brains”). These mechanisms arediscussed in terms of their functionality and common design parameters. Detailed stressor force analysis of them is omitted as these are covered in traditional stress analysis andmachine design courses.

The analogy between a human controlled system and computer control system isshown in Figure 1.2. If a process is controlled and powered by a human operator, theoperator observes the behavior of the system (i.e., using visual observation), then makesa decision regarding what action to take, then using his muscular power takes a partic-ular control action. One could view the outcome of the decision making process as alow power control or decision signal, and the action of the muscles as the actuator signalwhich is the amplified version of the control (or decision) signal. The same functionali-ties of a control system can be automated by use of a digital computer as shown in thesame figure.

The sensors replace the eyes, the actuators replace the muscles, and the computerreplaces the human brain. Every computer controlled system has these four basic functionalblocks:

1. process to be controlled,

2. actuators,

3. sensors,

4. controller (i.e., digital computer).


INTRODUCTION 3

: Brain for decision making

S : Eye for sensing

: Muscles for actuation

ProcessInput

Input

Output

Output

(a)

(b)

Clock

CPUx = f(x, u)u = .......

DO,DAC

DI,ADC

Actuationsystem

Process

Sensors

A

A

S

C

C

FIGURE 1.2: Manual and automatic control system analogy: (a) human controlled,

(b) computer controlled.

The microprocessor (μP) and digital signal processing (DSP) technology had two impactson control world,

1. it replaced the existing analog controllers,

2. prompted new products and designs such as fuel injection systems, active suspension,home temperature control, microwave ovens, and auto-focus cameras, just to namea few.

Every mechatronic system has some sensors to measure the status of the process vari-ables. The sensors are the “eyes” of a computer controlled system. We study most commontypes of sensors used in electromechanical systems for the measurement of temperature,pressure, force, stress, position, speed, acceleration, flow, and so on (Figure 1.3). This listdoes not attempt to cover every conceivable sensor available in the current state of the art,but rather makes an attempt to cover all major sensor categories, their working principlesand typical applications in design.

Actuators are the “muscles” of a computer controlled system. We focus in depthon the actuation devices that provide high performance control as opposed to simpleON/OFF actuation devices. In particular, we discuss hydraulic and electric power actuatorsin detail. Pneumatic power (compressed air power) actuation systems are not discussed.


4 MECHATRONICS

Operator /communications

interfaces

Control computer (PLC)

Power source(Engine pump)

Actuators (Valves)Machine/process

(Mechanism)Sensors

FIGURE 1.3: Main components of any mechatronic system: mechanical structure, sensors,

actuators, decision making component (microcontroller), power source, human/supervisory

interfaces.

They are typically used in low performance, ON/OFF type control applications (although,with advanced computer control algorithms, even they are starting to be used in highperformance systems). The component functionalities of pneumatic systems are similar tothose of hydraulic systems. However, the construction detail of each is quite different. Forinstance, both hydraulic and pneumatic systems need a component to pressurize the fluid(pump or compressor), a valve to control the direction, amount, and pressure of the fluidflow in the pipes, and translation cylinders to convert the pressurized fluid flow to motion.The pumps, valves, and cylinders used in hydraulic systems are quite different to thoseused in pneumatic systems.

Hardware and software fundamentals for embedded computers, microprocessors, anddigital signal processors (DSP), are covered with applications to the control of electrome-chanical devices in mind. Hardware I/O interfaces, microprocessor hardware architectures,and software concepts are discussed. The basic electronic circuit components are discussedsince they form the foundation of the interface between the digital world of computersand the analog real world. It is important to note that the hardware interfaces and embed-ded controller hardware aspects are largely standard and do not vary greatly from oneapplication to another. On the other hand, the software aspects of mechatronics designsare different for every product. The development tools used may be same, but the finalsoftware created for the product (also called the application software) is different for eachproduct. It is not uncommon that over 80% of engineering effort in the development of amechatronic product is spent on the software aspects alone. Therefore, the importance ofsoftware, especially as it applies to embedded systems, cannot be over emphasized.

Mechatronic devices and systems are the natural evolution of automated systems. Wecan view this evolution as having three major phases:

1. completely mechanical automatic systems (before and early 1900s),

2. automatic devices with electronic components such as relays, transistors, op-amps(early 1900s to 1970s),

3. computer controlled automatic systems (1970s–present)

Early automatic control systems performed their automated function solely throughmechanical means. For instance, a water level regulator for a water tank uses a floatconnected to a valve via a linkage (Figure 1.4). The desired water level in the tank is setby the adjustment of the float height or the linkage arm length connecting it to the valve.The float opens and closes the valve in order to maintain the desired water level. All thefunctionalities of a closed loop control system (“sensing-comparison-corrective actuation”


INTRODUCTION 5

Inflow

Outflow

Tank

Sensor

Comparator

Actuator

FIGURE 1.4: A completely mechanical closed loop control system for liquid level regulation.

or “sensor-logic-actuation”) may be embedded in one component by design, as is the casein this example.

Another classic automatic control system that is made of completely mechanicalcomponents (no electronics) is Watt’s flyball governor, which is used to regulate the speedof an engine (Figure 1.5). The same concept is still used in some engines today. The enginespeed is regulated by controlling the fuel control valve on the fuel supply line. The valveis controlled by a mechanism that has a desired speed setting using the bias in the springin the flywheel mechanism. The actual speed is measured by the flyball mechanism. Thehigher the speed of the engine is, the more the flyballs move out due to centrifugal force.The difference between the desired speed and actual speed is turned into control action bythe movement of the valve, which controls a small cylinder which is then used to control thefuel control valve. In today’s engines, the fuel rate is controlled directly by an electricallyactuated injector. The actual speed of the engine is sensed by an electrical sensor (i.e.,tachometer, pulse counter, encoder) and an embedded computer controller decides on how

“Compare”

Oil underpressure

“Amplify”

Fuelsupply

Control valve

Close

Open

Cylinder

Engine Load

“Speed sensing”

Pilotvalve

FIGURE 1.5: Mechanical “governor” concept for automatic engine speed control using all

mechanical components.


6 MECHATRONICS

2

2

33

1

1

Xact

Weng

a

b

T

Lever

Valve

Cylinder

TP

FIGURE 1.6: Closed loop cylinder position control system with mechanical feedback used in

the actuation of the main valve.

much fuel to inject based on the difference between the desired and actual engine speed(Figure 1.9).

Figure 1.6 shows a closed loop cylinder position control system where the positionfeedback is mechanical. The command signal is the desired cylinder position and is gener-ated by the motion of the lever moved by the pilot, and converted to the actuation powerto the valve spool displacement through the mechanical linkage. The position feedback isprovided by the mechanical linkage connection between the cylinder rod and the lever arm.When the operator moves the lever to a new position, it is the desired cylinder position(position 1 to position 2 in the figure). Initially, that opens the valve, and the fluid flow to thecylinder makes the piston move. As the piston moves, it also moves the linkage connected tothe lever. This in turn moves the valve spool (position 2 to position 3 in the figure) to neutralposition where the flow through the valve stops when the cylinder position is proportionalto the lever displacement. In steady-state, when the cylinder reaches the desired position, itwill push the lever such that the valve will be closed again (i.e., when the error is zero, theactuation signal is zero). The proportional control decision based on error is implementedhydro-mechanically without any electronic components.

xvalve(t) = 1a⋅ xcmd(t) − 1

b⋅ xactual(t) (1.1)

Analog servo controllers using operational amplifiers led to the second major changein mechatronic systems. As a result, automated systems no longer had to be all mechanical.An operational amplifier is used to compare a desired response (presented as an analogvoltage) and a measured response by an electrical sensor (also presented as an analogvoltage) and send a command signal to actuate an electrical device (solenoid or electricmotor) based on the difference. This brought about many electromechanical servo controlsystems (Figures 1.7, 1.8). Figure 1.7 shows a web handling machine with tension control.The wind-off roll runs at a speed that may vary. The wind-up roll is to run such that nomatter what the speed of the web motion is, a certain tension is maintained on the web.Therefore, a displacement sensor on the web is used to indirectly sense the web tensionsince the sensor measures the displacement of a spring. The measured tension is thencompared to the desired tension (command signal in the figure) by an operational amplifier.The operational amplifier sends a speed or current command to the amplifier of the motorbased on the tension error. Modern tension control systems use a digital computer controllerin place of the analog operational amplifier controller. In addition, the digital controller may


INTRODUCTION 7

FIGURE 1.7: A web handling motion control system. The web is moved at high speed while

maintaining the desired tension. The tension control system can be considered a mechatronic

system, where the control decision is made by an analog op-amp, not a digital computer.

use a speed sensor from the wind-off roll or from the web on the incoming side in order toreact to tension changes faster and improve the dynamic performance of the system.

Figure 1.8 shows a temperature control system that can be used to heat a room or oven.The heat is generated by the electric heater. Heat is lost to the outside through the walls.A thermometer is used to measure the temperature. An analog controller has the desiredtemperature setting. Based on the difference between the set and measured temperature, theop-amp turns ON or OFF the relay which turns the heater ON/OFF. In order to make sure

Command signal

Thermometer

Electric heater

Op-Amp

FAN

Electricmotor

Relay

Relay

L N 110 VAC/1 Ph

TimerdelayDC power

supply

FIGURE 1.8: A furnace or room temperature control system and its components using analog

op-amp as the controller. Notice that a fan driven by an electric motor is used to force the air

circulation from the heater to the room. A timer is used to delay the turn ON and turn OFF time

of the fan motor by a specified amount of time after the heater is turned ON or OFF. A

microcontroller-based digital controller can replace the op-amp and timer components.


8 MECHATRONICS

the relay does not turn ON and OFF due to small variations around the set temperature, theop-amp would normally have a hysteresis functionality implemented on its circuit. Moredetails on the relay control with hysteresis will be discussed in later chapters.

Finally, with the introduction of microprocessors into the control world in the late1970s, programmable control and intelligent decision making were introduced to auto-matic devices and systems. Digital computers not only duplicated the automatic controlfunctionality of previous mechanical and electromechanical devices, but also brought aboutnew possibilities for device designs that were not possible before. The control functionsincorporated into the designs included not only the servo control capabilities but also manyoperational logic, fault diagnostics, component health monitoring, network communica-tion, nonlinear, optimal, and adaptive control strategies (Figure 1.3). Many such functionswere practically impossible to implement using analog op-amp circuits. With digital con-trollers, such functions are rather easy to implement. It is only a matter of coding thesefunctionalities in software. The difficulty is in knowing what to code that works.

The automotive industry, the largest industry in the world, has transformed itself bothin terms of its products (the content of the cars) and the production methods of its productssince the introduction of microprocessors. Use of microprocessor-based embedded con-trollers significantly increased the robotics-based programmable manufacturing processes,such as assembly lines, CNC machine tools, and material handling. This changed the waythe cars are made, reducing the necessary labor and increasing the productivity. The prod-uct itself, cars, has also changed significantly. Before the widespread introduction of 8-bitand 16-bit microcontrollers into the embedded control mass market, the only electricalcomponents in a car were the radio, starter, alternator, and battery charging system. Engine,transmission, and brake subsystems were all controlled by mechanical or hydro-mechanicalmeans. Today, the engine in a modern car has a dedicated embedded microcontroller thatcontrols the timing and amount of fuel injection in an optimized manner based on theload, speed, temperaturem and pressure sensors in real time. Thus, it improves the fuelefficiency, reduces emissions, and increases performance (Figure 1.9). Similarly, auto-matic transmission is controlled by an embedded controller. The braking system includesABS (anti-lock braking system), TCS (traction-control system), DVSC (dynamic vehicle

Acceleratorpedal sensor Other

operatorinputs

Other enginesensors

SpeedsensorFuel

injections

ECU

Engine

FIGURE 1.9: Electronic “governor” concept for engine control using embedded

microcontrollers. The electronic control unit decides on fuel injection timing and amount in real

time based on sensor information.


INTRODUCTION 9

stability control) systems which use dedicated microcontrollers to modulate the control ofbrake, transmission and engine in order to maintain better control of the vehicle. It is esti-mated that an average car today has over 30 embedded microprocessor-based controllerson board. This number continues to increase as more intelligent functions are added tocars, such as the autonomous self driving cars by Google Inc and others. It is clear that thetraditionally all-mechanical devices in cars have now become computer controlled elec-tromechanical devices, which we call mechatronic devices. Therefore, the new generationof engineers must be well versed in the technologies that are needed in the design ofmodern electromechanical devices and systems. The field of mechatronics is defined as theintegration of these areas to serve this type of modern design process.

Robotic manipulator is a good example of a mechatronic system. The low-cost,high computational power, and wide availability of digital signal processors (DSP) andmicroprocessors energized the robotics industry in late 1970s and early 1980s. The roboticmanipulators, the reconfigurable, programmable, multi degrees of freedom motion mech-anisms, have been applied in many manufacturing processes and many more applicationsare being developed, including robotic assisted surgery. The main sub-systems of a roboticmanipulator serve as a good example of mechatronic system. A robotic manipulator hasfour major sub-systems (Figure 1.3), and every modern mechatronic system has the samesub-system functionalities:

1. a mechanism to transmit motion from actuator to tool,

2. an actuator (i.e., a motor and power amplifier, a hydraulic cylinder and valve) andpower source (i.e., DC power supply, internal combustion engine and pump),

3. sensors to measure the motion variables,

4. a controller (DSP or microprocessor) along with operator user interface devices andcommunication capabilities to other intelligent devices.

Let us consider an electric servo motor-driven robotic manipulator with three axes. Therobot would have a predefined mechanical structure, for example Cartesian, cylindrical,spherical, SCARA type robot (Figures 1.10, 1.11, 1.12). Each of the three electric servomotors (i.e., brush-type DC motor with integrally mounted position sensor such as anencoder or stepper motor with position sensor) drives one of the axes. There is a separatepower amplifier for each motor which controls the current (hence torque) of the motor. ADC power supply provides a DC bus at a constant voltage and derives it from a standardAC line. The DC power supply is sized to support all three motor-amplifiers.

The power supply, amplifier, and motor combination forms the actuator sub-systemof a motion system. The sensors in this case are used to measure the position and velocity

FIGURE 1.10: Three major robotic manipulator mechanisms: Cartesian, cylindrical, spherical

coordinate axes.


10 MECHATRONICS

FIGURE 1.11: Gantry, SCARA, and parallel linkage drive robotic manipulators.

of each motor so that this information is used by the axis controller to control the motorthrough the power amplifier in a closed loop configuration. Other external sensors notdirectly linked to the actuator motions, such as a vision sensors or a force sensors orvarious proximity sensors, are used by the supervisory controller to coordinate the robotmotion with other events. While each axis has a dedicated closed loop control algorithm,there has to be a supervisory controller that coordinates the motion of the three motors inorder to generate a coordinated motion by the robot, that is straight line motion, and so oncircular motion etc. The hardware platform to implement the coordinated and axis levelcontrols can be based on a single DSP/microprocessor or it may be distributed over multipleprocessors as shown. Figure 1.12 shows the components of a robotic manipulator in blockdiagram form. The control functions can be implemented on a single DSP hardware or adistributed DSP hardware. Finally, just as no man is an island, no robotic manipulator is an

Encoder Motor

Poweramp

Servoaxis

controller

Encoder Motor

Poweramp

Servoaxis

controller

Encoder Motor

Poweramp

Servoaxis

controller

Motion coordination communication bus

Coordination &supervisorycontroller

Operatorinterface

Motion controller

Othercommunication bus

Sensors-Proximity

Sensors-Vision

Sensors-Force

Powersupply

FIGURE 1.12: Block diagram of the components of a computer controlled robotic manipulator.


INTRODUCTION 11

island. A robotic manipulator must communicate with a user and other intelligent devicesto coordinate its motion with the rest of the manufacturing cell. Therefore, it has one ormore other communication interfaces, typically over a common fieldbus (i.e., DeviceNET,CAN, ProfiBus, Ethernet). The capabilities of a robotic manipulator are quantified by thefollowing;

1. workspace: volume and envelope that the manipulator end effector can reach,

2. number of degrees of freedom that determines the positioning and orientation capa-bilities of the manipulator,

3. maximum load capacity, determined by the actuator, transmission components, andstructural component sizing,

4. maximum speed (top speed) and small motion bandwidth,

5. repeatability and accuracy of end effector positioning,

6. manipulator’s physical size (weight and volume it takes).

Figure 1.13 shows a computer numeric controlled (CNC) machine tool. A multiaxis vertical milling machine is shown in this figure. There are three axes of motioncontrolled precisely (i.e., within 1∕1000 in or 25 micron = 25∕1000 mm accuracy) in x,y and z directions by closed loop controlled servo motors. The rotary motion of each ofthe servo motors is converted to linear motion of the table by the ball-screw or lead-screw

××

××

HMI

CNC

DC PS

AMP E M

Coupling

Table

Linear encoder

Lead/ball screw

CNC Controller

X-axis motor/encoders

Z-axis motor/encoders

Y-axis motor/encoders

Operator interfacecontroller, DC PS,

amps

FIGURE 1.13: Computer numeric controlled (CNC) machine tool: (a) picture of a vertical CNC

machine tools, reproduced with permission from Yamazaki Mazak Corporation, (b) x-y-z axes of

motion, actuated by servo motors, (c) closed loop control system block diagram for one of the

axis motion control system, where two position sensors per axis (motor-connected and

load-connected) are shown (also known as dual position feedback).


12 MECHATRONICS

mechanism in each axis. The fourth motion axis is the spindle rotation which typicallyruns at a constant speed. Each axis has its own servo motor (i.e., brushless DC motor withposition feedback), amplifier and DC power supply. In high precision machine tools, inaddition to the position sensors integral to the servo motor, there are also linear positionsensors (i.e., linear encoders) attached to the moving part of the table on each axis in orderto measure the translational position of the table directly. Using this measurement, thecontroller can compensate for position errors due to backlash and mechanical transmissionerrors in the lead-screw/ball-screw. The CNC controller implements the desired motioncommands for each axis in order to generate the desired cut-shape, as well as the closedloop position control algorithm such as a PID controller. When two position sensors areused for one degree of motion (one located at the actuator point (on the motor shaft) andone located at the actuated-tool point (table)), it is referred to as dual position feedbackcontrol system. A typical control logic in dual-position feedback system is to use the motor-based encoder feedback in velocity loop, and load-based encoder feedback in position loopcontrol. Current state of the art technology in CAD/CAM and CNC control is such that adesired part is designed in CAD software, then the motion control software to run on theCNC controller (i.e., G-code or similar code which defines the sequence of desired motionprofiles for each axis) is automatically generated from the CAD file of the part, downloadedto the CNC controller, which then controls each motion axis of the machine in closed loopto cut the desired shape.

Figure 1.14 shows the power flow in a modern construction equipment. The powersource in most mobile equipment is an internal combustion engine, which is a diesel enginein large power applications. The power is hydro-mechanically transmitted from engineto transmission, brake, steering, implement, and cooling fan. All sub-systems get theirpower in hydraulic form from a group of pumps mechanically connected to the engine.These pumps convert mechanical power to hydraulic power. In automotive type designs,the power from engine to transmission gear mechanism is linked via a torque converter. Inother designs, the transmission may be a hydrostatic design where the mechanical power isconverted to hydraulic power by a pump and then back to mechanical power by hydraulicmotors. This is the case in most excavator designs. Notice that each major sub-system has itsown electronic control module (ECM). Each ECM deals with the control of the sub-systemand possibly communicates with a machine level master controller. For instance, ECM forengines deals with maintaining an engine speed commanded by the operator pedal. Asthe load increases and the engine needs more power, the ECM automatically commandsmore fuel to the engine to regulate the desired speed. The transmission ECM deals withthe control of a set of solenoid actuated pressure valves which then controls a set of clutchand brakes in order to select the desired gear ratio. Steering ECM controls a valve whichcontrols the flow rate to a steering cylinder. Similarly, other sub-system ECMs controlselectrically controlled valves and other actuation devices to modulate the power used inthat sub-system.

The agricultural industry uses harvesting equipment where the equipment technologyhas the same basic components used in the automotive and construction equipment industry.Therefore, automotive technology feeds and benefits agricultural technology. Using globalpositioning systems (GPS) and land mapping for optimal utilization, large scale farming hasstarted to be done by autonomous harvesters where the machine is automatically guidedand steered by GPS systems. Farm lands are fertilized in an optimal manner based onpreviously collected satellite maps. For instance, the planning and execution of an earthmoving job, such as road building or a construction site preparation or farming, can bedone completely under the control of GPSs and autonomously driven machines withoutany human operators on the machine. However, safety concerns have so far delayed theintroduction of such autonomous machine operations. The underlying technologies are


INTRODUCTION 13

Steeringcylinder

Steeringhinge joint

Liftcylinder

Tiltcylinder

BucketOperator cab

Back frameFrontframe

ECM

ECM

ECM

ECM

ECM

Powertrain

Radiator

Tool force& speed

Machine traction& speed

Brake Hydraulic Pneumatic Pneumatic + Hydraulic

Hydrostatic drive

Torque converter + Mechanical transmission

Implements Hydraulic Ground engaging tool (GET)

Power source(Diesel engine)

Tires

Tracks

Steering Hydraulic

Cooling fan

FIGURE 1.14: Block diagram controlled power flow in a construction equipment. Power flow

in automotive applications is similar. Notice that modern construction equipment has

electronic control modules (ECMs) for most major sub-systems such as engine, transmission,

brake, steering, implement sub-systems.

relatively mature for autonomous construction equipment and farm equipment operation(Figure 1.15).

The chemical process industry involves many large scale computer controlled plants.The early application of computer controlled plants was based on a large central computercontrolling most of the activities. This is called the centralized control model. In recentyears, as microcontrollers became more powerful and low cost, the control systems for largeplants have been designed using many layers of hierarchy of controllers. In other words,


14 MECHATRONICS

GPS antenna

Radio communicator

Display

GPS receiver

FIGURE 1.15: Semi-autonomous construction equipment operation using global positioning

system (GPS), local sensors and on-vehicle sensors for closed loop sub-system control.

the control logic is distributed physically to many microcomputers. Each microcomputeris physically closer to the sensors and actuators it is responsible for. Distributed controllerscommunicate with each other and higher level controllers over a standard communicationnetwork. There may be a separate communication network at each layer of the hierarchicalcontrol system. The typical variables of control in process industry are fluid flow rate,temperature, pressure, mixture ratio, fluid level in tank, and humidity.

Energy management and control of large buildings is a growing field of applicationof optimized computer control. Home appliances are more and more microprocessor con-trolled, instead of being just an electromechanical appliances. For instance, old ovens usedrelays and analog temperature controllers to control the electric heater in the oven. The newovens use a microcontroller to control the temperature and timing of the oven operation.Similar changes have occurred in many other appliances used in homes, such as washersand driers.


INTRODUCTION 15

Micro electromechanical systems (MEMS) and MEMS devices incorporate all of thecomputer control, electrical and mechanical aspects of the design directly on the siliconsubstrate in such a way that it is impossible to discretely identify each functional component.Finally, the application of mechatronic design in medical devices, such as surgery assistivedevices, robotic surgery, and intelligent drills, is perhaps one of the most promising field inthis century.

Computer controlled medical devices (implant and external assistive, rehabilitationequipment) have been experiencing exponential growth as the physical size of sensing andcomputing devices becomes very tiny such that they can be integrated with small actuatorsas implant devices for human body. The basic principle of the sensing-decision-actuationis being put to many uses in embedded computer controlled medical devices (also calledbio-mechatronic devices, Figure 1.16). In time these devices will be able to integrate agrowing set of tiny sensors, and make more sophisticated real-time decisions about what (ifany) intervention action to take to assist the functioning of the human body. For instance,implant defibrillators and pace-makers for heart patients are examples of such devices. Apace-maker is a heart implant device that provides electrical pulses to the heart musculesto regulate its rate when it senses that the heart rate has fallen below a critical level. The

Pacemaker:

Pacemaker

Heart

CPU

Battery

Leads are used to “sense”heart condition

Leads to send electricalpulses to stimulate heartwhen needed

SuperiorVena Ca

Aorta PulmonaryArtery

PulmonaryVein

MitralValve

AorticValve

LeftAtrium

RightAtrium

RightVentricle

LeftVentricle

PulmonaryValve

TricuspidValve

Inferior Vena Cava

Embedded tiny microcontrollerand battery

FIGURE 1.16: Example of an embedded computer controlled medical device: a

bio-mechatronic device. The pulse generator houses the battery (electrical power source) and a

tiny embedded computer. The electrical wires between the heart and the pulse generator

(pace-maker) are for both sensing the heart condition (sensor cables) and actuating the heart

beat by electrical pulse signal shocks to the heart muscle. The sensing-decision-actuation

functions are integrated via the pulse generator and electrical signal leads. Wapcaplet, Yaddah

[GFDL (www.gnu.org/copyleft/fdl.html) or CC-BY-SA-3.0

(http://creativecommons.org/licenses/by-sa/3.0/)], via Wikimedia.

http://www.gnu.org/copyleft/fdl.html

http://creativecommons.org/licenses/by-sa/3.0/


16 MECHATRONICS

pace-maker senses the heart rate, and if the heart rate is below a critical rate, it sendselectrical pulses to the heart in order to increase the heart rate. The sensing and actuationcomponents are interfaced to the heart through electrical wires. The embedded computer,battery (electrical power source for the pulse power) and pulse generator circuit is oneintegrated unit which is implanted under the skin somewhere close to the heart.

In addition, many computer controlled orthopeadic devices are in the process ofdevelopment as implanted aid devices as well as rehabilitative devices. For example, inartificial hand devices, the embedded computer senses the desired motion signals in theremaining muscles which are sent from the brain, then interprets them to actuate themechanical hand like it would function in a natural hand. The compact electromechanicaldesign of the hand mechanism, its integrated actuation and sensing (position and forcesensors) devices are electromechanical design problems. Measurement and interpretationof the desired motion signals from human brain to the residual muscles and, based on thatinformation, determining the desired motion of the hand is an intelligent signal processingand control problem (see National Geographic Magazine, …. issue).

1.1 CASE STUDY: MODELING AND CONTROLOF COMBUSTION ENGINES

The internal combustion engine is the power source for most of the mobile equipmentapplications including automotive, construction, and agricultural machinery. As a result,it is an essential component in most mobile equipment applications. Here, we discuss themodeling and basic control concepts of internal combustion engines from a mechatronicsengineering point of view. This case study may serve as an example of how a dynamic modeland a control system should be developed for a computer controlled electromechanicalsystem. Basic modeling and control of any dynamic system invariably involves use ofLaplace transforms. As a result, detailed analysis using Laplace transforms is minimizedhere in this introductory chapter.

We will discuss the basic characteristics of a diesel engine from a mechatronicsengineer’s point of view. Any modeling and control study should start with a good physicalunderstanding of how a system works. We identify the main components and sub-systems.Then each component is considered in terms of its input and output relationship in modeling.For control system design purposes, we identify the necessary sensors and controlledactuators. With this guidance, we study

1. engine components – basic mechanical components of the engine,

2. operating principles and performance – how energy is produced (converted fromchemical energy to mechanical energy) through the combustion process,

3. electronic control system components: actuators, sensors, and electronic control mod-ule (ECM),

4. dynamic models of the engine from a mechatronics engineer’s point of view,

5. control algorithms – basic control algorithms and various extensions in order to meetfuel efficiency and emission requirements.

An engine converts the chemical energy of fuel to mechanical energy through thecombustion process. In a mobile equipment, sub-systems derive their power from theengine. There are two major categories of internal combustion engines: (i) Clerk (two-stroke) cycle engine; (ii) Otto (four-stroke) cycle engine. In a two-stroke cycle engine,there is a combustion in each cylinder once per revolution of the crankshaft. In a four-stroke cycle engine, there is a combustion in each cylinder once every two revolutions ofthe crankshaft. Only four-stroke cycle engines are discussed below.

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