An electrohydraulic vibration exciter using a two-dimensional valve

Abstract

A scheme for an electrohydraulic vibrator excited by a two-dimensional valve is proposed, which significantly extends the frequency range compared to that of vibrators excited by conventional servo valves. In the two-dimensional valve, the rotary motion of the spool coordinates the relative motion of the grooves on the spools area with respect to the windows on the sleeve which in turn, alternates the oil flowrate into and out of the chambers of the hydraulic cylinder (motor) and subsequently excites the piston (rotor) to vibrate. The linear motion of the two-dimensional valve spool is used to vary the peak flowrate and thus the amplitude of the output vibration. The frequency of the vibration excited by the two-dimensional valve is related to the rotary speed of the spool and the number of the grooves on the spool area (windows on the sleeve). This configuration extends the frequency of the hydraulic vibrator by increasing the number of the grooves on the spool area (windows on the sleeve) and the rotary speed of the spool which are in the perfect lubrication of oil.

A model of the two-dimensional vibrator is developed and compared to its experimental counterpart. The vibration excited by the two-dimensional valve is influenced by pressure saturation, the elastic force, and the hydraulic resonance. There is a critical valve linear opening, beyond which the output force (torque) reaches a saturation value in both a positive and negative sense. Both simulation and experimental results show that at lower frequencies the ascent and descent slopes of the output force show some inconsistency which becomes more significant above the critical valve linear opening but drops off with a reduction in the valve linear opening. In a higher frequency range, the vibration excited by the two-dimensional valve is mainly influenced by hydraulic resonance. As the input frequency approaches the hydraulic resonant frequency, the output excited vibration essentially becomes the hydraulic resonance. Therefore, the effective frequency range of the hydraulic vibration is not only decided by the frequency bandwidth of the two-dimensional valve, but is influenced by the hydraulic resonance. Nevertheless, the study does provide an access to the high-frequency excitation of the hydraulic vibration.

Keywords

two-dimensional valve electrohydraulic vibration exciter modelling

Get full access to this article

View all access options for this article.

References

McConnell

K. G.

Vibration testing—theory and practice (John Wiley & Sons, New York 1995).

Harris

C. M.

Shock and vibration handbook (McGraw-Hill, New York 1988).

Fox

L. G.

‘Electrodynamic shaker fundamentals.’

Sound Vibration 31 (4) (1997): 14–23

Merritt

H. E.

Hydraulic control systems (1967): 67–86 (Wiley, New York).

Ruan

Burton

Ukrainetz

‘An investigation into the characteristics of a two dimensional 2D flow control valve.’

Trans. ASME J. Dyn. Syst., Meas. Control 124 (2002): 214–220

Ruan

Burton

‘Bulk modulus of air content oil in a hydraulic cylinder.’ ASME International Mechanical Engineering Congress and Exposition, 2006, paper 15854, Fluid Power Control System Technology, vol. 7, 2006.

Ruan

Burton

Ukrainez

‘Direct actuated digital servo valve.’

In Proceedings of the Ninth Scandinavian International Conference on Fluid power, Linköping, Sweden, 1–3 June 2005, pp. 450–461.