The two-DOF controllable close-chain linkage mechanism system is investigated in this paper. Based on the air-gap field of the non-uniform airspace of motors caused by the eccentricity of rotor, the electromechanical coupling relation in the real running state of motors is analyzed. The electromechanical coupling dynamic model of the system is established by means of the finite element method. The dynamic equation constitutes the basis on which the combination resonance characteristics of the system caused by electromagnetic parameter excitations of the two motors are analyzed by the multiple scales method. The first-order stationary solution is obtained under that condition, and the stability conditions of the stationary solution are also given. Finally, an experiment is presented. Results indicate that it is feasible and beneficial to explain some unexpected strong vibration phenomena in the high-speed operation of such multi-DOF controllable close-chain linkage mechanism using nonlinear combination resonance theories
