Stability and frequency response of hydro-mechanical shakers in vibration rigs

An analytical study on the stability and frequency response of hydromechanical shakers used for generating vibrational signals to drive a vibration rig is presented. The analytical expressions for stability are derived based on linearized flow characteristic equations and taking into account the effect of fluid inertance and resistance in the connecting pipes. It was shown that the size of the connecting pipes and their elasticity influence the stability of the shaker. Simple expressions are derived for the amplitude ratio and phase angle against frequency for both open and closed loop frequency response of the hydromechanical shaker based on Duffing's linearization scheme. The analytical expressions derived for stability and frequency response can be directly used for selecting and/or specifying the hydromechanical shaker which best meets a given set of requirements.