الفهرس 
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Abstract
Hydraulic systems are characterized by their ability to import large forces
at high speeds and are used in many industrial motion systems, also, in
applications where good dynamic performance is important. Hydraulic
systems are also common in aircraft, where their high power-to-weight ratio
and precise control makes them an ideal choice for actuation of flight surfaces.
Electro hydraulic flow control valves, either proportional or servo (EHSV),
are used in industry in a wide number of applications like machine tools,
testing equipment, mining machinery, fatigue testing, flight simulation, paper
machines, ships and electromagnetic marine engineering, injection molding
machines, robotics, steel and aluminum mill equipment and autonomous
manufacturing systems. These systems have favorable size to power ratio,
precise and accurate control, and ability to apply very large forces. Servo
hydraulic systems offer several other benefits over their electrical counter
parts. For example, hydraulic systems are mechanically “stiffer”, resulting in
higher machine frame resonant frequencies for a given power level, higher
loop gain and improved dynamic performance.
These investigations focus on the static and dynamic performance of a
linear hydraulic system (displacement control system) under different
operating conditions in case of connecting a flow control servo valve. High
technology is used for measuring and recording the experimental results,
which achieves accurate evaluations. Experiments have been conducted under
no-load. Then, system has been loaded by 5560 N and the experiments are
repeated. Supply pressure has been changed from 10 up to 50 bar.
Experiments have been conducted without connecting springs to the system,
then repeated in case of connecting springs with stiffness 32 N/mm. Effect of
temperature variation of hydraulic oil on system performance has been
investigated beginning from 28 oC up to 40 oC and 50 oC.
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It is concluded that increasing temperature of hydraulic oil requires higher
power in order to achieve the same supply pressure at low temperature.
Accordingly, an increase in the flow rate occurs. The values of pressure decay
at low temperature are less than the values at high temperature, also the
pressure decay for the case of connecting flow control servo valve is less than
in case of connecting PDFCV at the same conditions.
The dynamic performance of the system is affected by different operating
conditions. The frequency increases by increasing the temperature and by
decreasing the load, while connecting springs to the system decreases
frequency. In addition, bandwidth frequency increases by increasing
temperature and decreases by increasing the load and connecting springs to the
system.