This paper studies the dynamic response of the support beam under the unbalanced excitation of the rice threshing system. The differential equation of motion of the supporting beam under the action of harmonic force is established by the modal superposition method, and its dynamic response is analyzed. It is found that the initial vibration of the supporting beam will fluctuate greatly when it is excited by the unbalanced force. In response to this problem, the application of composite beams as

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... the support structure of the threshing system is proposed. The composite beam is mainly composed of uniform and isotropic Euler–Bernoulli beams that are parallel to each other, and the two beams are connected by elastic spring elements. Then, the vibration response of the composite beam structure under unbalanced forces is studied. The results show that the vibration of the composite beam is more stable when it is excited by the unbalanced drum. The overall vibration response amplitude is smaller than that with single support, and the vibration reduction effect is obvious. When the stiffness changes, the change trend of the response amplitude of beam 1 and beam 2 is opposite, that is, the stiffness increases, the vibration amplitude of beam 1 decreases, and the amplitude of beam 2 increases. This shows that the composite beam is suitable for the support structure of the harvester.