Pressure flow frequency characteristics of a sharp-edged cylindrical choke are studied. It is pointed out and proved experimentally that the flow characteristics in the cylindrical choke are quite similar to those in the sudden contraction tube as shown in the author's previous paper. Thus, a mathematical model for the frequency characteristics of a cylindrical choke is proposed. The oscillatory volume flow rate is obtained from the measurements center-line velocity using a laser Doppler velocimeter, and experiments on the frequency characteristics are carried out. It is shown that the theoretical results coincided very well those obtained experimentally.

View full abstract

In this reserch, influences of mean value of input signal on the frequency response of a hydraulic servomotor are elucidated analytically and experimentally.
In the analysis, according to the amplitude levels of load pressure, the nonlinear flow characteristics for spool valve are approximated with three different forms. Using the harmonic balance method, the frequency responses are calculated theoretically
Influence of mean value of input signal are quantified by the equivalent damping factor ζ.
Except for the case of very small spool displacement, theoretical, experimental and simulated results show a good agreement, leading to the following conclusions: (1) For small amplitude of sinusoidal component X₁, the influence of mean value X₀ on the frequency response is remarkable.
(2) The equivalent damping factor is increased with an increase in X₀, taking its peak value at the natural frequency of the actuator.
(3) At the natural frequency, ζ is approximately proportional to X₀ in the domain of X₀ > X₁, taking a constant value (non Zero) at X₀→0.

View full abstract