Hydrostatic Transmissions and Actuators: Operation, Modelling and Applications / Edition 1

by Gustavo Costa, Nariman Sepehri

Overview

Hydrostatic Transmissions and Actuators takes a pedagogical approach and begins with an overview of the subject, providing basic definitions and introducing fundamental concepts. Hydrostatic transmissions and hydrostatic actuators are then examined in more detail with coverage of pumps and motors, hydrostatic solutions to single-rod actuators, energy management and efficiency and dynamic response. Consideration is also given to current and emerging applications of hydrostatic transmissions and actuators in automobiles, mobile equipment, wind turbines, wave energy harvesting and airplanes. End of chapter exercises and real world industrial examples are included throughout and a companion website hosting a solution manual is also available.

Hydrostatic Transmissions and Actuators is an up to date and comprehensive textbook suitable for courses on fluid power systems and technology, and mechatronics systems design.

Product Details

ISBN-13:	9781118818794
Publisher:	Wiley
Publication date:	09/28/2015
Pages:	416
Product dimensions:	6.90(w) x 9.88(h) x 1.00(d)

About the Author

Gustavo Koury Costa graduated in 1992 with a bachelor degree in Mechanical Engineering and has been teaching Fluid Power for 19 years at his current institution. He also holds a Doctorate degree in Computational Fluid Dynamics, having spent one year as a Postdoctoral Fellow at the University of Manitoba Fluid Power and Tele-Robotics Research Laboratory.

Nariman Sepehri is a professor in Mechanical Engineering. He holds five patents and has published over 100 journal articles on various aspects of fluid power, including systems, manipulation, diagnosis and control. His current research focuses on self-healing, energy-efficient and reliable fluid power systems with applications to aircraft, hydraulic tele-manipulators and off-highway equipment. He is a Fellow and has served as Chair of the Fluid Power Systems and Technology Division of the American Society of Mechanical Engineers (ASME). He has served on editorial boards of eight journals including the International Journal of Fluid Power.

Table of Contents

Preface xiii

Acknowledgements xvii

About the Companion Website xix

1 Introduction to Power Transmission 1

1.1 Transmission Ratio 1

1.1.1 Generalities 1

1.1.2 Definition 3

1.1.3 Classification 3

1.2 Mechanical Transmissions 4

1.2.1 Gear Trains 4

1.2.2 Gearboxes 6

1.2.3 Efficiency 8

1.2.4 Continuously and Infinitely Variable Transmissions 11

1.3 Hydraulic Transmissions 15

1.4 Hydrostatic Transmissions 19

1.4.1 Operational Principles 19

1.4.2 Formal Definition of Hydrostatic Transmissions 32

1.4.3 Classification of Hydrostatic Transmissions 34

1.4.4 Efficiency Considerations 40

1.5 Hydromechanical Power-Split Transmissions 40

1.5.1 General Classification 41

1.5.2 Transmission Ratio 42

1.5.3 Lockup Point 44

1.5.4 Power Relations 44

1.6 Mechanical and Hydrostatic Actuators 51

1.6.1 Mechanical Actuators 51

1.6.2 Hydrostatic Actuators 52

1.6.3 Hydrostatic Actuation Versus Valve Control 53

1.6.4 Multiple Cylinder Actuators 55

Exercises 56

References 57

2 Fundamentals of Fluid Flows in Hydrostatic Transmissions 59

2.1 Fluid Properties 59

2.1.1 Viscosity 59

2.1.2 Compressibility 64

2.2 Fluid Flow in Hydraulic Circuits 79

2.2.1 Flow Regimes 79

2.2.2 Internal Flow in Conduits 81

2.2.3 Flow Through Orifices 85

2.2.4 Leakage Flow in Pumps and Motors 87

2.2.5 Other Loss Models 93

Exercises 94

References 96

3 Hydrostatic Pumps and Motors 98

3.1 Hydrostatic and Hydrodynamic Pumps and Motors 98

3.2 Hydrostatic Machine Output 102

3.2.1 Average Input–Output Relations 102

3.2.2 Instantaneous Pump Output 104

3.2.3 Instantaneous Motor Output 112

3.2.4 Further Efficiency Considerations 116

3.3 Hydrostatic Pump and Motor Types 117

3.3.1 Radial Piston Pumps and Motors 117

3.3.2 Axial Piston Pumps and Motors 119

3.3.3 Gear Pumps and Motors 128

3.3.4 Vane Pumps and Motors 130

3.3.5 Digital Displacement Pumps and Motors 131

3.4 Energy Losses at Steady-State Operation 135

3.4.1 Energy Balances 135

3.4.2 Overall Efficiencies 138

3.4.3 Simplified Efficiency Equations 138

3.4.4 Efficiency Relations 139

3.5 Modelling Pump and Motor Efficiencies 141

3.5.1 Performance Curves 141

3.5.2 Volumetric Efficiency Modelling 144

3.5.3 Overall Efficiency Modelling 154

3.5.4 Mechanical Efficiency 160

Exercises 162

References 164

4 Basic Hydrostatic Transmission Design 166

4.1 General Considerations 166

4.1.1 Output Speed Control 166

4.1.2 Transmission Losses 167

4.2 Hydrostatic Transmission Efficiency 168

4.2.1 Energy Balance 169

4.2.2 Conduit Efficiency 171

4.2.3 Minor Pressure Losses 173

4.2.4 Practical Application 176

4.3 Transmission Output 183

4.4 Steady-State Design Applications 184

4.4.1 Case Study 1. Fixed-Displacement Motor and Variable-Displacement Pump 185

4.4.2 Case Study 2. Fixed-Displacement Pump and Variable-Displacement Motor 192

4.5 External Leakages and Charge Circuit 198

4.6 Heat Losses and Cooling 201

4.6.1 Sizing of the Heat Exchanger 201

4.6.2 Loop Flushing 203

Exercises 204

References 205

5 Dynamic Analysis of Hydrostatic Transmissions 207

5.1 Introduction 207

5.1.1 Pressure Surges during Transients 208

5.1.2 Mechanical Vibrations and Noise 211

5.1.3 Natural Circuit Oscillations 214

5.1.4 Resonance and Beating 217

5.1.5 Summary 219

5.2 Modelling and Simulation 219

5.2.1 Basic Equations 220

5.2.2 Case Study 1. Purely Inertial Load with a Step Input 223

5.2.3 Case Study 2. Variable Pump Flow 231

Exercises 240

References 241

6 Hydrostatic Actuators 243

6.1 Introductory Concepts 243

6.1.1 Circuit Operational Quadrants 243

6.1.2 Energy Management 244

6.1.3 Cylinder Stiffness 245

6.1.4 Double-Rod and Single-Rod Actuators 245

6.2 Hydrostatic Actuator Circuits 247

6.2.1 Design 1. Dual-Pump, Open-Circuit, Displacement-Controlled Actuator 247

6.2.2 Design 2. Dual-Pump, Closed-Circuit, Displacement-Controlled Actuator 249

6.2.3 Design 3. Dual-Pump Electrohydrostatic Actuator with Accumulators 251

6.2.4 Design 4. Circuit with an Inline Hydraulic Transformer 253

6.2.5 Design 5. Single-Pump Circuit with a Directional Valve 257

6.2.6 Design 6. Single-Pump Circuit with Pilot-Operated Check Valves 260

6.2.7 Design 7. Single-Pump Circuit with Inline Check Valves 263

6.2.8 Design 8. Energy Storage Circuit 267

6.2.9 Design 9. Double-Rod Actuator 273

6.3 Common Pressure Rail and Hydraulic Transformers 275

Exercises 281

References 282

7 Dynamic Analysis of Hydrostatic Actuators 283

7.1 Introduction 283

7.2 Mathematical Model 284

7.2.1 Basic Equations 284

7.2.2 Cylinder Friction 288

7.2.3 Pilot-Operated Check Valves 294

7.3 Case Study 298

7.3.1 Determination of the Pump Flow Period 299

7.3.2 Numerical Simulation 300

Exercises 304

References 306

8 Practical Applications 307

8.1 Infinitely Variable Transmissions in Vehicles 307

8.2 Heavy Mobile Equipment 310

8.3 Hybrid Vehicles 313

8.3.1 Definition 315

8.3.2 Electric Hybrids 315

8.3.3 Hydraulic Hybrids 316

8.3.4 CPR-Based Hybrids 321

8.4 Wind Turbines 323

8.4.1 Asynchronous Generators 324

8.4.2 Synchronous Generators 326

8.4.3 General Aspects of Power Transmission in Wind Turbines 328

8.4.4 Hydrostatic Transmission in Wind Turbines 329

8.5 Wave Energy Extraction 331

8.6 Aeronautical Applications 334

References 336

Appendix A Hydraulic Symbols 339

Appendix B Mathematics Review 345

B.1 The Nabla Operator (∇) 345

B.2 Ordinary Differential Equations (ODEs) 346

B.2.1 General Aspects and Definitions for ODEs 347

B.2.2 The Laplace Transform Method 351

References 360

Appendix C Fluid Dynamics Equations 361

C.1 Introduction 361

C.2 Fluid Stresses and Distortion Rates 363

C.3 Differential Fluid Dynamics Equations 365

C.3.1 Conservation of Mass 365

C.3.2 Conservation of Momentum 367

C.3.3 Navier–Stokes Equations in Cylindrical Coordinates 370

C.4 Control Volume Analysis 371

C.4.1 The Reynolds Transport Theorem 371

C.4.2 Mass and Momentum Conservation 373

C.4.3 Conservation of Energy 375

References 378

Index 379