Abstract: The complete stiffness model of antenna subreflector adjusting mechanism (SAM) is constructed based on influence coefficient method of parallel mechanism and principle of virtual work. The model considers comprehensively the impact of elastic deformation of active-passive joint and external force/moment and gives the specific transposed form of the second order influence coefficient. The axial line stiffness model of single branched chain is constructed considering the effect of hooke hinge and spherical hinge on branch rod axial stiffness. The complete stiffness matrix of SAM is solved by introducing varying parameter on condition that the fixed platform is movable, which solves fully the stiffness matrix calculation problem of SAM in any spatial position and orientation. Through the comparative analysis among the simplest stiffness model, mechanism stiffness model and whole stiffness model, the micro-displacement curve of SAM moving platform center is mapped with the change of varying parameter in the SAM initial configuration, and the correctness is verified by the finite element analysis software at two limit configurations. The research content lays an important theory basis for the structural design and precision compensation of large radiotelescopeantenna SAM.

Key words: Complete stiffness model, Influence coefficient, Micro-displacement curve, Subreflector adjusting mechanism