Nonlinear dynamics near resonances of a rotor-active magnetic bearings system with 16-pole legs and time varying stiffness

•The nonlinear dynamic behaviors of a rotor-AMB system with 16-pole legs are studied.•Comparison of the electromagnetic force resultants is given.•The nonlinear equations of motion are constructed for the rotor-AMB system.•The effects of different parameters on the frequency-response curves are analyzed.•The chaotic motions of the rotor-AMB system are analyzed.