Dynamic Analysis And Error Research Of Special 5-DOF Hybrid Mechanism

With the rapid development of our country's aerospace industry,the demand for high-performance wind tunnels is also increasing.As the key equipment of wind tunnel test,the performance of the model support device directly affects the accuracy and credibility of the test results.Due to the existence of objective reasons such as complex working conditions,large external loads,and high precision requirements,driving error problems has always been difficult points in the development of model support devices.In view of the fact that the model support device of a certain wind tunnel cannot meet the test requirements,this paper developed a set of series-parallel five-degree-of-freedom hybrid mechanism,and studied its kinematics,dynamics,static error and elastic deformation error.While realizing the accurate driving of the mechanism,research has been carried out on how to effectively reduce the pose error at the end of the mechanism.The research results are of great significance for improving the test capability of the wind tunnel.The main work of this paper is as follows:(1)Analyzing the design requirements of the mechanism.Based on the comparative analysis of the related configurations,the specific structures of positioning with series mechanism and directionality with parallel mechanism are determined.(2)The construction of the kinematics model of the mechanism is completed by using methods such as homogeneous transformation matrix,closed vector equation and rod length conditions,and its correctness is verified through simulation experiments.Based on the results of kinematic analysis,the speed and acceleration of each part of the mechanism are analyzed by using the theory of motion influence coefficient,and the Jacobian matrix reflecting the speed mapping relationship of the mechanism is obtained.Combined with Newton-Euler method,the dynamic model of the mechanism is established,and the more complicated two-degree-of-freedom parallel rotating platform is analyzed.The theoretical derivation is verified by virtual prototype technology,which provides theoretical support for the design and control of the mechanism.(3)The error sources of the mechanism are analyzed and summarized,and the static error model of the mechanism is established based on 18 geometric errors modeling methods and matrix method.The first-order sensitivity function method is used to analyze the transmission law and accumulation effect of each error source in the mechanism.Aiming at the problem that the linear error source is inconsistent with that of the angle error source in the analysis process,a solution of adding the angle error weight coefficient is proposed,which realizes the identification of the main error sources of the mechanism,and lays the foundation for the static error prevention of the mechanism.(4)Based on the finite element method,using SOLIDWORKS and ANSYS software for co-simulation,and the overall stiffness coefficient matrix of the mechanism under different positions and orientations is obtained.The BP neural network is used to build the mapping model between the mechanism's pose and the stiffness coefficient matrix.Based on this model,the elastic deformation error at the end of the mechanism is predicted,and the forward kinematics compensation method is used to compensate the elastic deformation error at the end of the mechanism,which lays a foundation for the further improvement of the pose accuracy of the end of the mechanism.