Design of a passive self-tuning lever-type vibration isolation system

Abstract

In this study, a novel self-tuning passive lever-type vibration isolation system for base excitations is described. Due to inertial coupling within the vibration isolation system, an antiresonance frequency is generated, which depends on the amplification ratio of the lever. At this frequency, the instant center of zero velocity of the lever coincides with the payload hinge point. As a result, the payload experiences minimum amount of vibration. When the excitation frequency changes, the system changes the lever ratio so as to bring the antiresonance frequency to coincide with the excitation frequency to suppress the output vibration. The designed mechanical system does not require any electronic sensors or actuators. The self-tuning operation is enabled by a vibro-impact type actuator powered by the input vibration rendering the system self-powered. This actuator is placed below the payload hinge and moves the lever in the appropriate direction to bring the instant center of zero velocity to the payload hinge position. Hence, the system achieves the optimum lever ratio for minimum vibration output. The equations of motion of the system are derived and the location of the instant center is obtained analytically. Then, multi-body dynamic simulations are carried out to verify the self-tuning response of the system. An experimental set-up incorporating a variable ratio lever, a softly suspended ground mass and a vibro-impact type actuator, is designed. Experimental results validate that the system always goes to antiresonance condition in the working frequency range.