배관 압력을 이용한 방향제어밸브 위상각 대역폭 주파수 측정에 관한 연구

A Study on the Phase Bandwidth Frequency of a Directional Control Valve Based on the Hydraulic Line Pressure

Abstract

Spool displacement of a direction control valve is the standard signal to measure the bandwidth frequency of the direction control valve. When the spool displacement signal is not available, it is suggested in this study to use the metering hydraulic line as an alternative way to measure - 90 degree phase bandwidth frequency of the hydraulic direction control valve. Dynamics of the hydraulic line is composed of inertia, capacitance, and friction effects. The effect of oil inertia is dominant in common hydraulic line dynamics and the line dynamics is close to a derivative action in a range of high frequency; such as a range of bandwidth frequency of common directional control valves. Phase difference between spool displacement and line load pressure is nearly constant as a valve close to 90 degree. If phase difference is compensated from the phase between valve input and pressure, compensated phase may be almost same as the phase of spool displacement that is a standard signal to measure phase bandwidth frequency of the directional control valve. A series of experiments were conducted to examine the possibility of using line pressure in to measure phase bandwidth frequency of a directional control valve. Phase bandwidth frequency could be measured with relatively high precision based on metering hydraulic line technique and it reveals consistent results even when valve input, oil temperature, and supply pressure change.

Fig. 1 Schematic view to use the metering hydraulic line for measurement of the bandwidth frequency of a directional control valve

Fig. 2 Serial structure transfer function system

Fig. 3 Photographic view for the hardware part of the bandwidth frequency measuring device

Fig. 4 Time domain responses of valve input i, spool displacement x_v and the pressure p_Lv

Fig. 5(a) Phase frequency response of i→x_v

Fig. 8 Comparison between the phase bandwidth frequencies of ' ∡ i → x_v ' and ' ∡ i → p_Lv - '∡ x_v → p_Lv $ | $ _comp ' for $\phi$0.25 in hose

Fig. 9 Comparison between the phase bandwidth frequencies of ' ∡ i → x_v ' and ' ∡ i → p_Lv - ∡ x_v → p_Lv $ | $ _comp ' for $\phi$0.5 in hose

Fig. 10 Phase frequency responses of ' ∡ x_v → p_Lv ' for 2.5 V, 5 V and 9 V inputs

Fig. 11 Effect of the oil temperture variation on the bandwidth frequencies

Fig. 12 Effect of the supply pressure variation on the bandwidth frequencies

Fig. 5(b) Phase frequency response of x_v → p_Lv

Fig. 5(c) Phase frequency response of i →p_Lv

Fig. 6 Comprison between Phase frequency responses of '∡ i → x_v' and '∡ i → p_Lv - ∡ x_v → p_Lv '

Fig. 7 Comparison between the phase bandwidth frequencies of '∡ i → x_v ' and ' ∡ i → p_Lv - ∡ x_v → p_Lv $ | $ _comp ' for $\phi$0.011 m steel tube

Table 1 Parameters related to a hydraulic line and oil

Table 2 Specification of the metering hydraulic line system

Table 3 Error of the measured bandwidth frequencies for 3 metering hydraulic lines

Table 4 Error of the measured bandwidth frequencies for environmental factors