| Parabolic cylindrical antennas have been widely used in the fields of precipitation radar and earth observation.However,the existing deployable cylindrical antennas have the defects such as single structure and poor deploying performance.Therefore,a truss-type parabolic cylindrical deployable antenna structure is developed that combined with the advantages of light weight,easy folding and strong expansion of the truss mechanism in this paper.In addition,the structure design,shape-finding of cable net,mechanical performance and prototype experiment are deeply studied.The truss-type parabolic cylindrical antenna is composed of a square truss and a parabolic cylindrical cable net,and driven by the system of spring-cable.The truss is the main supporting structure and deployable mechanism of the antenna,which is formed by a series of folding parallelogram units.The size of the beam is optimized by analyzing the relationship between the structural parameters and the antenna's fundamental frequency and mass.According to the functional requirements,the synchronizing gear is assembled in the three-way joint to ensure the synchronism,and the pulley in the five-way joint ensures the smooth transmission of the driving cable.The kinematics model of truss is established,and the cubic polynomial is used to plan the deployment is an uniform acceleration-uniform speed-uniform deceleration process.The numerical simulation demonstrates that the symmetry of the structure and the motion relationship of the vertical rod.The parabolic cylindrical cable net is composed of the axial cable and the plane mesh alternately connected,and the plane mesh forms a symmetric parabola through the vertical cable tension.The connection method effectively reduces the coupling between the plane mesh and facilitates the surface precision.Regarding the shape-finding of cable net,on the one hand,the design of geometric shape is realized by the equal-length linear approximation,and the preloading tension is solved by combining the singular value decomposition and the linear optimization.On the other hand,considering the influence of truss deformation on the shape of cable net,and the first-order optimization algorithm in ANSYS is used to optimize the double-objective problem of the surface accuracy and the tension uniformity.The results show that the truss deformation is reduced by 69.86%,the surface accuracy is improved by 93.62%,and the tension uniformity is improved by 47%.The mechanical properties of the proposed structure are analyzed by simulation.Firstly,the working process of cable net is simulated by ADAMS,the results show that the final preload is stabilized at the set value after the various cable undergoes the relaxationstretching-tensioning process,and the cable net is tensioned to form a parabolic cylindrical.Secondly,modal analysis by ANSYS show that the fundamental frequency of the antenna is 5.0925 Hz,the low-order mode is the overall vibration,and the high-order mode is the local mesh vibration.Besides,the factors affecting the natural frequency are analyzed,and effective measures to improve the antenna vibration frequency are obtained.In order to verify the feasibility of the antenna structure scheme proposed in this paper,a experimental prototype with a size of 2054 mm ×1040mm ×475mm was produced,and the folding radio was measured to be 8.40.Based on the Goo Gol controller and Yaskawa servo motor to build the control system,the hardware circuit and control software of the system are specifically designed and developed.The development experiment of the prototype are carried out and the driving force are measured,the results show that the proposed structural is feasible and developable,but the driving is heavily affected by gravity and friction. |
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