958
CHAPTER 29
FLUID POWER SYSTEMS
Andrew Alleyne
University of Illinois, Urbana–Champaign
Urbana, Illinois
1
INTRODUCTION
958
2 SYMBOLS AND TERMINOLOGY 959
3 SYSTEM COMPONENTS
961
3.1 Hydraulic Oils
961
3.2 Hydraulic Hoses
966
3.3 Hydraulic Pumps
968
3.4 Hydraulic Valves
974
3.5 Cylinders and Motors
982
3.6 Other Components
984
4 SYSTEM DYNAMIC BEHAVIOR
986
5 COMMON NONLINEARITIES
990
5.1 Saturations and Deadzones
990
5.2 Hysteresis and Asymmetry
990
5.3 Friction
991
REFERENCES
991
1
INTRODUCTION
The use of fluids for power delivery has been a part of human civilization for many centuries.
For example, much of the growth in the United States textile industry in the 1820s and 1830s
can be credited to the abundant supply of hydraulic power available in the northeastern
United States through lakes and man-made canals.1 Early hydraulic systems utilized gravi-
tational potential to convert the energy stored in the fluid to some type of useful mechanical
energy. Currently, fluid power systems are ubiquitous in our everyday society. All facets of
our lives are touched by some form of pressurized fluid distributing power. Simple trans-
portation examples would be fuel delivery systems or braking systems in cars and buses.
Many manufacturing systems also use fluid power for presses and other types of forming
applications. In fact, fluid power is seen as a vital and necessary component for many types
of engineering systems. This is particularly true in mobile applications where a power-
generation component, such as an internal combustion engine, is coupled to the fluid power
system. In these cases, the inherent power density advantages of fluid power make it a very
attractive choice over other types of actuation.
One key advantage of fluid power systems is the high power density available. This
means a very large force can be generated in a very compact space; something that is useful
for applications such as aircraft where weight and volume are at a premium. Another ad-
vantage is the ability to hold loads for long peri