Experimental and theoretical analysis of auto-parametric stability of pendulum with viscous dampers

An experimental analysis of a dynamic absorber on a tower represented by a spherical auto-parametric pendulum is carried out. Stability of the motion in a vertical plane of two pendulum configurations is analysed with regard to the semi-trivial solution. Three different types of the resonance domain are investigated. Their main properties depend significantly on dynamic parameters of the pendulum and of the external excitation amplitude. A special experimental frame is developed. It contains a pendulum supported by the Cardan joint and excited by a shaker. There are two magnetic units attached to the frame and to the supporting axes of rotation. They are able to reproduce linear viscous damping for both degrees of freedom. The stability of the system is analysed experimentally and compared with theoretical results. The analytical, numerical and experimental studies result in several recommendations for designers of these devices. © 2011 Institute of Thermomechanics AS CR, v.v.i.