Load adaptive sliding mode control of electromagnetic quasi-zero stiffness isolators

Quasi-zero-stiffness (QZS) isolators have excellent vibration isolation performance in the low-frequency range. However, in complex excitation environments, such as load mismatch condition, vibration isolation performance and corresponding stability deteriorate. To improve the vibration isolation performance of electromagnetic zero-stiffness isolators (E-QZS) and reduce the sensitivity to load, a load adaptive sliding mode control method of E-QZS is proposed. The theoretical model of an electromagnetic zero-stiffness isolator is established and a sliding mode control is designed. The range of gain coefficients for stable operation is determined using Lyapunov's theorem. Additionally, we have devised a load-adaptive control law and conducted a corresponding stability analysis. Through simulation and experimental research, the results demonstrate that setting appropriate gains can enhance vibration isolation performance by 90%. Furthermore, the introduction of a load-adaptive sliding mode controller effectively reduces the impact of sudden load changes on isolation performance, thereby improving the robustness of the isolation system.