The purpose of this article is to investigate the motion characteristics and dynamic mechanisms of a resonance starting process in a free-piston engine generator. A nonlinear dynamic model of the resonance starting process is described, and extensive simulation results are presented, giving insight into the engine starting characteristics; the dynamic mechanism of the resonance staring process is also studied based on a reasonable analytical method for the dynamic mode. The research results indicate that the free-piston engine generator is a single degree of freedom self-excited dynamic system with variable damping and stiffness. The starting process has oscillation stability; the piston motion can be resonated first to large stroke length by a linear motor with low electromagnetic force and then tends to reach a stable state after a few cycles in the starting process. The final amplitude is determined by the energy balance between the motor thrust force and the friction load.
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