Research On Dynamic Analysis Method Of Rigid-flexible-thermal Coupling For Spaceborne Large-aperture Antenna

With the rapid development of informationization and networking,large-aperture antennas widely used on spacecraft play a key role.Large-aperture antenna as one of flexible appendages is subjected to strong heat flow from solar radiation from shadows to sunshine,resulting in thermal deformation of flexible antenna array,which leads to the coupling between satellite body,antenna array and thermal load.The traditional flexible multi-body system dynamics analysis method based on the hypothesis of small deformation cannot accurately describe the large-scale and large-flexibility dynamics modeling.Absolute Nodal Coordination Formulation(ANCF),which has the innate advantage of describing large-flexibility and large-deformation,is widely used in the flexible multi-body dynamics system.In this paper,the ANCF displacement field interpolation principle is used to phase the temperature field.By interpolating with the same format,a unified shape function of temperature field and displacement field is realized,and a thin plate element integrated with temperature description is constructed.Based on this element,the whole satellite model is constructed by assembling the large aperture antenna array and the satellite body.The thermal-dynamic coupling behavior caused by the thermal flux from the solar radiation is analyzed.The rigid-flexiblethermal coupling behavior includes the rotation of the rigid satellite,the thermal deformation of the large aperture flexible antenna array and the solar radiation heat flux,thermal radiation dissipation and the internal heat source caused by the deformation of antenna array.Based on the element dynamic equation obtained by virtual work principle,the element mass matrix,generalized external force and its Jacobian matrix to the node coordinates,generalized damping force and its Jacobian matrix to the node coordinates are derived.Taking the solution of element mass matrix as an example,the volume integral method of element is given,and the dynamic system linear and non-linear constraints of thin plate element are dealt with separately.Based on the first law of thermodynamics,the heat conduction equation of thin plate element is given,and the heat boundary condition is applied.The finite element discretization of the heat conduction equation is carried out.The relevant tables of the thermodynamic system,such as the element heat capacity matrix,the heat conduction matrix,the thermal radiation matrix,the heat flux vector from solar radiation are derived and checked.Based on the principle of virtual work,the equivalent equation of virtual work is formulated by generalized damping force multiplied by virtual displacement and virtual power multiplied by time microelement.The power of inner heat source of element caused by internal damping of material is derived.At the same time,the generalized thermal stress corresponding to the thermal strain of the element caused by temperature change is deduced.A rigid-flexible-thermal coupled dynamic solver for thin plate element based on generalized-alpha method is developed to verify the thermal expansion,the existence of damping,the conservation of total energy and the relationship between mechanical energy and internal energy.Based on the ANCF thin plate element with integrated temperature description,the antenna array model of large aperture satellite antenna is established.The whole satellite-antenna model is assembled by combining the satellite body of approximate rigid body described by reference node.For the antenna with initial bending configuration,the initial elastic force,damping force and thermal stress are removed,and the reference node with complete position coordinates and gradient vector coordinates described by natural coordinates method are introduced.The gradient mode length and gradient direction of the reference node are constrained to ensure that the internal strain of the reference node is always zero.Dynamic and heat loads are applied to the satellite body and antenna array,respectively.The large aperture satellite antenna complete rigid-flexible-thermal coupled dynamic model is constructed,and its dynamic behavior is analyzed.