Research On Establishment Of The Flexible Spacecraft’s Mecahnical Model And Its Dynamic Characterisitc

This paper is aimed at establishing the mechanical model of a flexible spacecraft equipped with a deployable antenna reflector attached to its central platform and analyzing its dynamic characteristic. By the time the spacecraft starts to shift in orbit, the central platform’s large motion can excite the antenna link arm’s structural vibration. Meanwhile due to the structural vibration the link arm will apply a distributing force whose direction and magnitude keep changing all the time to the platform, which will endanger the spacecraft’s attitude stability. Thus this paper’s research contents can make an important contribution to enhance of the spacecraft’s attitude stability and vibration reduction of its flexible attachments.This paper first built the spacecraft’s FEM model and calculated its mode shapes and natural frequencies in free boundaries, then stimulated its attitude adjustment movement on the method of rigid-flexible coupling by the software Adams. Nevertheless the FEM model has a high order which brings much difficulty in design of the spacecraft attitude control law, and the mechanical model from Adams is a kind of zero order rigid-flexible one which is helpless to calculate its dynamic responses in the case of high speed revolution. Then this paper established the one order rigid-flexible coupling simplified mechanical model of the spacecraft and obtained its dynamic responses in the high speed rolling case. In order to study the antenna reflector mass and link arm’s structure and material properties’ influence on the spacecraft’s dynamic responses, this paper calculated the mechanical model’s governing equation when the link arm’s density, elasticity modulus, cross section area and the mass of the antenna reflector were different values, then analyzed and obtained the influence rule.At last conclusions are obtained that in the process of the spacecraft’s attitude adjustment, the central platform’s large motion can cause flexible attachments’ structural vibration, whose magnitude can be centimeter-level and meanwhile the spacecraft’s movement can oscillate obviously due to flexible attachments’ disturbing forces; the spacecraft’s one order rigid-flexible coupling mechanical model can be used to calculate its dynamic responses in the case of high speed rolling, and its governing equations are rather brief which can be used in the design of the attitude control law; the antenna reflector and link arm’s physical properties have a significant influence on the spacecraft’s dynamic characteristic, which is beneficial to the improvement of the structure design and flexible attachments’ vibration suppression.