Aerospace Actuators 1

Jean-Charles Maré is Professor Emeritus at Institut Clément Ader, Toulouse, France. His teaching, covering both initial and continuing education, focuses on aerospace actuation systems. His research, often conducted in collaboration with industry, addresses system architectures, preliminary design and virtual prototyping of onboard actuation systems.

Introduction xi
Notations and Acronyms xv
Chapter 1. General Considerations 1
1.1. General information 1
1.1.1. Definitions. 1
1.1.2. Need and power flow 3
1.1.3. Actuation functions 5
1.1.4. Actuation needs and constraints 10
1.1.5. Classification and regulatory framework 17
1.1.6. Development cycle 21
1.2. Primary and secondary power transmission functions for actuators 24
1.2.1. Primary functions 25
1.2.2. Secondary functions 27
1.2.3. Signal approach and power approach 29
1.2.4. Types of actuators 29
Chapter 2. Reliability 35
2.1. Risks and risk acceptance 35
2.2. Dependability 39
2.2.1. Fault to failure 40
2.2.2. Fight against failures 41
2.3. Response to failure for aerospace actuators 42
2.3.1. Resistance to failure 42
2.3.2. Tolerance to failure 43
2.3.3. Examples 45
2.4. Redundancy 47
2.4.1. Static redundancy 50
2.4.2. Dynamic redundancy 53
2.5. Combination of redundancy principles 57
2.6. Feared events and failure rates in actuation 58
2.7. Fundamentals of reliability calculation 58
2.7.1. Variables used in reliability calculation 59
2.7.2. Generic failure rate models 62
2.7.3. Reliability of element associations 64
2.8. References and short glossary pertaining to reliability 67
Chapter 3. General Concepts for Hydraulic Power Solutions 69
3.1. Hydraulic power actuation 69
3.1.1. Units and reference values 69
3.1.2. Energy transport by a liquid 70
3.1.3. Historical evolution of power and pressure use 74
3.2. Potential advantages and disadvantages of hydraulic technology 80
3.2.1. Advantages 80
3.2.2. Disadvantages 82
3.3. Architectural concepts 84
3.3.1. Power architecture for hydraulic actuation 84
3.3.2. Design rules and recommendations 85
Chapter 4. Hydraulic Fluid and Its Conditioning 91
4.1. Needs, constraints and evolutions 91
4.1.1. Opportunities and constraints in hydrostatic power transmission 91
4.1.2. Range of operational temperature and fire resistance 93
4.2. Actual hydraulic fluid 97
4.2.1. Physical properties 99
4.3. Fluid conditioning 101
4.3.1. Fluid in sufficient quantity 101
4.3.2. Avoid gas pollution and cavitation 103
4.3.3. Isolation of solid pollution 104
4.3.4. Thermal management 108
4.3.5. External leakage collection 112
4.3.6. Monitoring and maintaining the fluid in working conditions 112
4.3.7. Impact on the design and operation of hydraulic systems 114
4.4. Energy phenomena caused by the fluid 119
4.4.1. Hydraulic resistance 119
4.4.2. Hydraulic capacitance 120
4.4.3. Hydraulic inertia 122
4.4.4. Speed of sound in the hydraulic fluid 122
Chapter 5. Hydromechanical Power Transformation 123
5.1. General considerations 123
5.2. Functional perspective 129
5.3. Technological shortcomings 130
5.3.1. Energy losses 130
5.3.2. Compressibility of the hydraulic fluid 134
5.3.3. Wall deformation 134
5.3.4. Pulsations 134
5.3.5. Charging 136
5.3.6. Drainage 136
5.4. Pump driving 137
5.4.1. Driving performed by main engines: engine-driven pump 138
5.4.2. Driving performed by an electric motor: electric motor pump (EMP) or alternative current motor pump (ACMP) 139
5.4.3. Driving performed by a hydraulic motor: PTU 140
5.4.4. Driving performed by dynamic air: ram air turbine or air-driven pump 141
5.4.5. Driving performed by a gas turbine: solid propellant gas generator or monofuel emergency power unit (MEPU) 142
5.4.6. Blow-down fluid pressurization 144
5.5. Hydraulic motors 144
Chapter 6. Power Metering in Hydraulics 147
6.1. Metering principles 147
6.2. Power-on-demand 150
6.2.1. Energy losses at partial power 150
6.2.2. Metering by pump drive adjustment 151
6.2.3. Metering by displacement adjustment 152
6.2.4. Closed hydraulic circuit, open hydraulic circuit 158
6.3. Metering by hydraulic restriction 159
6.3.1. Functional configuration 160
6.3.2. Types of distribution 165
6.4. Impact of restriction configuration and properties on the metering function 167
6.4.1. Fixed hydraulic restriction 167
6.4.2. Variable hydraulic restriction 170
6.5. Servovalves 186
6.5.1. Architecture 186
6.5.2. Incremental improvements of servovalve performances 189
6.5.3. Power supply of the electromagnetic motor 191
6.5.4. Pilot stages concepts 191
6.5.5. Functional bias 198
6.5.6. Direct drive valve 199
6.5.7. Application to wheel braking 203
Chapter 7. Power Distribution and Management in Hydraulics 207
7.1. Power distribution and management 207
7.2. Providing power 209
7.2.1. Transporting fluid 209
7.2.2. Isolating 213
7.2.3. Sequencing user power supplies 215
7.2.4. Merging sources 216
7.2.5. Sharing sources 217
7.2.6. Storing/restoring energy 219
7.2.7. Adjusting the pressure level 222
7.3. Protecting 223
7.3.1. Protecting against overpressure/overload 223
7.3.2. Protecting against cavitation and outgassing 226
7.3.3. Protecting against overconsumption 228
7.4. Managing the load 230
7.4.1. Locking the load in position 231
7.4.2. Ensuring irreversibility 231
7.4.3. Releasing the load 232
7.4.4. Damping the load 234
7.5. Monitoring 238
Chapter 8. Architectures and Geometric Integration 239
8.1. Introduction 239
8.2. Arrangement of actuation functions 239
8.3. Architectures and routing 241
8.3.1. Architectures of power networks 241
8.3.2. Routing of power networks 250
8.3.3. Architecture of actuators 250
8.4. Integration of components and equipment 259
8.4.1. In-line integration 259
8.4.2. Manifold integration 260
8.4.3. Sub-system integration 263
8.5. Integration of actuators in the airframe 265
8.5.1. Controls 265
8.5.2. Structural integration 268
Appendix 275
References 279
Index 291