Active pendulum vibration absorbers with a spinning support

Abstract

A novel pendulum vibration absorber with a rotational base is proposed for neutralization of vertical excitations. The characteristic frequency of the absorber can be dynamically tuned over a wide range by varying the rotational speed. The external disturbance is countered by the inertial force of the revolving mass, whose angular momentum is not affected by the external excitation. As a result minimal power is required to sustain the system in steady state. This paper first derives the characteristic frequency of the rotational pendulum as function of the rotational rate. A pair of symmetric pendulums are then installed on a primary structure subject to harmonic disturbances. It is shown how the pendulum absorber is capable of balancing the external excitation. Asymptotic stability of the linearized system is also proved. Numerical simulations are then conducted to illustrate the performance of the system. Finally a variant design resembling a fly-ball governor is presented; it has the merit of ensuring simultaneous motions of two symmetric rotational pendulums so that lateral oscillations are canceled. The proposed scheme is suitable for an active vibration control system where there is a constraint on the power or force capacity of a linear actuator.