PRINCIPLES OF HYDRAULIC SYSTEMS DESIGN
Pages : 314
Size : 5 MB
This book was intended to provide knowledge of
hydraulic components, their operating characteristics and available circuit
arrangements to assist in the design of hydraulic systems for a range of
applications. For some circuits it is important to predict the dynamic per-
formance of the overall system particularly where closed loop control is
being employed. For this purpose and to provide a general understanding
of how parameters vary transiently analytical methods are developed that
provide techniques for studying the dynamics of systems. In this second
edition these features have been retained and expanded upon so as to eval-
uate the performance of some hydrostatic transmission examples.
In the period since the first edition there has been a considerable
expansion in the use of digital computers for control purposes which has
been accompanied by developments in the instrumentation field and use
of electromechanical valves. This technology often involves closed loop
control methods for example, the control of motor speed in a hydrostatic
transmission. This raises issues of dynamic performance and stability,
areas that are expanded in this second edition.
It is useful to have an understanding of the mechanical losses in
pumps and motors and a section has been added to model frictional pro-
cesses in a typical hydrostatic motor which shows the effects of friction on
torque and mechanical efficiency.
Independently operated valves for pumps and motors are not a new
technological development but their use is becoming more apparent
because of the options that are available for displacement control. The
advantages of this technology are that conventional distributor valves and
displacement change mechanisms are avoided which eliminates their fric-
tional and volumetric losses and consequently results in increased efficiency
particularly at reduced displacement. The design aspects of servo
systems to provide this important feature are discussed.
There has been a considerable development of industrial standards
particularly in the fields of the determination of dangerous failure possi-
bilities and system safety. These standards are referred to where applicable
and discussed in the final chapter on systems management. Relevant stan-
dards are listed in the Appendix.