On The 6-PSS Parallel Adjusting Mechanism For Space-borne SAR Antenna

With the continuous development of space science and technology,the high-altitude earth observation has made great progress,and the satellite antenna system plays an irreplaceable role.At the same time,the SAR antenna is developing towards large aperture and high flatness because of the development of Space-borne SAR technology and the increasing requirement for target detection,In this thesis,kinematics and dynamics of the antenna array position adjustment mechanism are analyzed and studied for the realization of the overall plane flatness of large-scale expandable SAR antennas.The main work of the paper are as follows:Firstly,according to the design index,the 6-PSS parallel mechanism is selected as the antenna array adjustment mechanism configuration.The Newton iteration method is used to solve the positive kinematics of the mechanism in the basic of inverse kinematics analysis.Based on the rigid body velocity projection theorem,the mechanism velocity Jacobian matrix is deduced in detail,and the explicit expression of the Jacobian matrix is obtained.The velocity and acceleration of the driving slider are solved on the basis of the Jacobian matrix.The polar coordinate search method is used to solve the flexible working space and reachable work of the parallel mechanism,verify that the workspace of the mechanism fully meets the requirements of the design index.Secondly,the error analysis model of 6-PSS parallel mechanism is established based on vector differentiation method.The error transfer matrix is obtained by fully differentiating the mechanism length equation.The Monte Carlo method is used to obtain the error distribution of the moving platform under the premise that the positioning error in each direction obeys the uniform distribution.The singular value decomposition(SVD)principle is used to solve the eigenvalues of the error transfer matrix,and three different mechanism error sensitivity indicators are defined.By analyzing the changes of the mechanism error sensitivity under different pose parameters,while providing a basis for the optimization of the mechanism parameters.Further,by analyzing the influence of the mechanism parameters on the global error coefficient of the mechanism and the condition number of the Jacobian matrix,an optimization model is established that the global error coefficient and the Jacobian matrix condition number mean value are used as the objective function,and the structural parameters of the mechanism are used as optimization variables,the artificial bee colony algorithm is used to solve the optimization model.The design parameters with higher dexterity and motion precision are obtained under the premise of satisfying the rotation range of the ball joint and the moving distance of the driving slider.Finally,the Lagrange method is used to establish the mechanism dynamics model,and the driving force acting on the driving slider is solved by combining the mechanism velocity Jacobian matrix and the virtual work principle.In order to overcome the impact of the mechanism during the movement process,the trajectory function method is used to plan the motion trajectory of the motion platform,and the corresponding curve of the motion platform and the position,driving force and power variation curve of the driving slider are obtained through numerical simulation.The parallel mechanism model is established in the 3D modeling software and imported into the dynamic simulation software to build a virtual prototype.The driving force and power curve of the driving slider are obtained through dynamic simulation.The dynamic performance of the system is summarized and compared with the numerical simulation results to verify the accuracy of the dynamic model.