Study On The Fuzzy Adjustment And Gravity Effect Of Cable Net Structure

The cable net structure is widely used in the aerospace field,and its surface precision RMS affects the antenna electrical performance.With the development of aerospace,there are more and more requirements and considerations for the cable net surface precision in engineering.The influence of uncertainty factors and ground gravity on the shape surface precision,and how to eliminate the influence of ground gravity,attract more and more attention.Therefore,this paper studies on the following three aspects:?1?The fuzzy shape adjustment method of uncertain cable net structure has been studied.Based on the related fuzzy mathematics research,the uncertainty of the cable net elastic deformation,the uncertainty of the thermal deformation,and the uncertainty of the tension measurement are ultimately equivalent to the fuzzy uncertainty of the cable tension.Combined with the related research on the force density,a fuzzy force density balance equation for cable nets was established.And based on this,a fuzzy optimization model for the surface precision of the cable net structure was established with the optimal target of the surface precision RMS.Finally,the circular truss cable net structure is taken as an example to calculate the fuzzy distribution of the RMS accuracy before and after adjustment,which verifies the effectiveness and reliability of the proposed fuzzy surface adjustment method.?2?The morphological analysis method of cable net structure under gravity has been studied.Based on the related research of catenary cable elements,an optimization model of solving element nodal forces is established to realize the high-precision nodal forces and element stiffness matrices for any catenary element.And,based on the knowledge of finite element grouping,the relationship between nodal force increment and nodal displacement increment of the cable composite structure is deduced.Then,an optimized form-finding model is established to solve the equilibrium state of the cable composite structure with the optimal target of the minimum joint force of free nodal forces.Finally,this paper takes a single cable element as an example to verify the efficiency,feasibility and high accuracy of the method for solving the nodal forces and element stiffness matrix of the cable.Using the simple orthogonal catenary cable combination structure example,the equilibrium state obtained by the optimization method of this paper is compared with the results obtained in the related references,and the accuracy,efficiency and reliability of the optimization method are verified.?3?The analysis method of the influence of gravity on the mesh reflective surface has been studied.Because the mesh processing,assembly and adjustment of the deployable antenna are all carried out on the ground,the deformation of the cable mesh surface caused by gravity can't be ignored.And it is of great significance to study how to eliminate the influence of gravity on the cable mesh surface.In this paper,the pre-tension design for gravitational mesh reflection surface is firstly performed to obtain the initial value of the solution of the gravity surface.Considering the influence of gravity deformation on the precision of the antenna surface,the force balance equation of high precision flexible cable net system is established by using catenary element.And then a shape-finding optimization model under gravity is established to find the equilibrium shape P₁ of the flexible cable net under gravity.Afterwards,an optimized shape-finding model after gravity removal is established to find the equilibrium shape P₂ after gravity removal.Finally,a numerical example was used to verify that the cable mesh surface P₁ under gravity was able to return to the ideal shape surface P₀ after the gravity was removed.In the absence of any gravitational unloading measures,the gravity-deformed surface P₁ can be used directly to guide the surface adjustment of the ground cable network,and this method can achieve the purpose of eliminating ground gravity effects.