Effect of Coulomb friction on nonlinear vibration isolation system

The effect of Coulomb friction and nonlinearity in a vibration isolation platform is studied in this paper, focusing on the analysis and design of nonlinear stiffness, friction force and damping characteristics to achieve an advantageous vibration isolation performance. The nonlinear isolation platform consists with connecting rods, springs, dampers and joints, which induce Coulomb friction forces in the joint parts. Considering the influence incurred by different structural parameters on system equivalent friction forces, the vibration isolation of the platform is studied. The proposed structure provides a remarkably powerful, practical and passive solution to realize the beneficial nonlinear stiffness and damping characteristics in vibration control. Since stiffness and damping properties are both asymmetrical nonlinear functions, and Coulomb friction is piecewise nonlinear function, Perturbation Method (PM) and Average Method (AM) are applied together to seek better solutions. The solutions by combination of PM and AM can accurately describe the responses and effect of Coulomb friction. The results not only show that much better vibration isolation performance and loading capacity can be easily achieved with nonlinear isolation platform by designing structural parameters, but also provide an accurate novel method to solve dynamic equation with nonlinear and piecewise functions.