Page 113 - Fluid Power Engineering

Hydraulic Transmission Lines 87

model describes with good precision the first dominant mode of the
line resonance from the point of view of the resonance frequency and
magnitude.
When dealing with fluid power systems, there is an increased
need for the simplest line model to reach a reasonably acceptable
simulation program of the whole system. The distributed parameter
models are more precise. However, these models, in general, might
complicate the total system model in an unacceptable way.
It is a common practice to simplify the hydraulic power system
model in one of the following ways:
• The transmission lines behavior is assumed negligible,
whenever possible.
• The line inertia is sometimes added to that of the neighboring
moving parts.
• The line capacitance (the effect of oil compressibility and wall
deformation) is added to that of the attached actuator or
neighboring valve cavity.
Therefore, the development of system models, incorporating a
lumped parameter description of transmission lines, carries the physical
structure of the line, without complicating the mathematical description
and the simulation programs.