Study on Dynamic Stability of a Torsional Isolator with Negative Stiffness Structures

Abstract

The dynamic stability of a novel passive torsional vibration isolator with negative stiffness structures (NSS) is investigated in this study. First, the structure and vibration isolation principle of the isolator are introduced. The isolator is composed of conventional linear springs and connecting rod spring structures in parallel, which offer negative stiffness, thus to obtain low dynamic stiffness. The nonlinear stiffness is derived and torque characteristics of the isolator are studied under different compression deformation of springs used in negative stiffness structures. A two degree of freedom (DOF) nonlinear mathematical model is built and its dynamic characteristics are analyzed by using the numerical method. Based on the theories of chaos and bifurcation, variations of system stability with excitation amplitude, frequency and system damping are investigated respectively. Analysis results reveal that, the isolation system exhibits complex nonlinear dynamic behavior, including the period doubling solution, chaotic solution, etc. The results also demonstrate that in the condition of heavy load and low frequency, the system tends to be unstable. Ranges of amplitude and frequency of fluctuating torque which can be stably isolated are obtained from the bifurcation diagrams. And the system damping could be designed so that undesirable bifurcation and chaotic behaviors can be avoided or greatly suppressed. The results of the study provide a useful insight into the analysis and design for the stable control.