Dynamic response and parameter identification of an impact oscillator with a one-sided elastic constraint.

Impact systems are common in engineering and exhibit inherently nonlinear and nonsmooth dynamics due to intermittent contact and elastic deformation. This study investigates the dynamic response and parameter identification of an impact oscillator with a one-sided elastic constraint. A custom experimental rig was developed to generate controlled vibro-impact responses, and a piecewise-smooth mathematical model was formulated to capture the unilateral contact dynamics. Two complementary parameter identification strategies, a genetic-algorithm-based optimisation and a backbone-curve fitting method derived from harmonic balance principles, were employed to estimate key system parameters, including impact stiffness, damping, and gap, using both displacement-frequency and time-domain data. The identified parameters agreed consistently with theoretical predictions across repeated experimental trials, demonstrating the repeatability of the proposed identification framework for the stable periodic responses observed under the forward stepped-sine excitation tests. Overall, the study provides an experimentally supported framework for identifying nonlinear characteristics of impact oscillators, with potential applications in structural dynamics, vibration mitigation, and biomedical diagnostics.