Planetary gearboxes are designed to reduce speed while increasing load capacity in power transmission systems. This study simulates the dynamics of the eighteen- degree-of-freedom planetary gearbox with timevarying mesh stiffness using MATLAB/Simulink software. We derive the dynamic equations to analyze the impact of worn bearings on the vibration output of the gearbox. The simulation and experimental analysis techniques are utilized for fault detection, focusing on time signals and velocity spectrum's. The looseness of the bearings affects the vibrations of both the gearbox body and its gears. In this investigation, we simulate the classification of bearing looseness in the planetary gearbox and compare the results with experimental validations. This comparison demonstrates how worn bearings can influence the failure of a planetary gearbox and affect the amplitude of rotational speed frequencies. The primary aim of this research is to detect bearing failure using only the amplitude of harmonic vibration at rotational speed, without any new failure frequency excitation.
