A novel four-degree-of-freedom compactor-soil coupling model

A novel four-degree-of-freedom (4-DOF) compactor–soil coupling model is proposed to investigate the nonlinear dynamic characteristics of vibratory compactors. The model integrates the dynamics of the frame, oscillator, and eccentric block while introducing three constitutive relationships—viscoelastic, viscoelastic–plastic, and separation models—to represent the unloading, loading, and jumping stages of the compaction process. This stage-dependent framework enables a unified description of the complete vibration–compaction cycle. The Melnikov method is employed to determine the threshold conditions for chaotic motion, revealing that the transition from periodic to chaotic behavior strongly depends on excitation frequency and soil plasticity. The results indicate that the switching model, which alternates between viscoelastic and viscoelastic–plastic states, more accurately captures the actual dynamic response than single-phase models. Furthermore, the effect of random noise on the system response is analyzed, showing that increasing noise intensity amplifies nonlinear coupling and leads to stochastic–chaotic vibrations. To mitigate instability, a delayed feedback (DF) active suspension control strategy is introduced. Numerical simulations demonstrate that the DF control effectively suppresses chaotic oscillations, attenuates resonance peaks, and enhances the robustness of the system under strong random disturbances. The proposed model and control approach provide a comprehensive theoretical foundation for understanding nonlinear compaction dynamics and improving the design and performance of intelligent compaction systems.