Research On The Optimal Design And Error Of A Six-degree-of-freedom Mechanism For A Test Device

With the increasing demand of flight simulation test,the existing test equipment has been unable to meet the needs of the test.Therefore,developing a set of flight test equipment suitable for a simulated flight test has become one of the core issues of simulated flight test.Based on the original six-degree-of-freedom mechanism of the flight test simulator,a set of six-degree-of-freedom mechanism of the flight test simulator is redesigned and optimized.And the kinematics,dynamics,static error and vibration error of the device are studied.Firstly,this paper introduces the support structure of the original model.According to the technical requirements of a simulated flight test device,the strength and stiffness of the original mechanism are analyzed.According to the analysis results,it is identified that the Z axis vertical plate and X axis shaft are the weakest parts of the static stiffness of the whole machine,and the Z axis vertical plate is designed for error prevention.Finally,the response surface of the simplified model is optimized.In the case of meeting the technical indicators,the machine’s deformation in all directions is reduced as much as possible,and the error of the mechanism is reduced from the root,and the position accuracy of the end of the mechanism is improved.Secondly,based on the original model support mechanism of the flight test simulator,the D-H method which can describe the relationship of coordinate transformation is used to establish the kinematics model of the mechanism.And completes the forward kinematics solution of the mechanism,and establishes the foundation for the following static error analysis.According to the Lagrange function based on energy,the dynamic model of the mechanism is deduced,and the dynamic simulation of the virtual prototype of the six-degree-of-freedom mechanism is carried out in Adams Finally,the correctness of the dynamic model is verified and the dynamic parameters of the mechanism are obtained,which provides guidance for the selection of the mechanism.Thirdly,the static error model of the mechanism is established by D-H parameters in the kinematics model,and the relationship between X-axis end pose error and D-H parameter error are obtained.And a verification scheme is designed to verify the differential motion error model.Then the geometric error parameters are identified by the iterative summation of the least square method.In the process of using the least square method,the Jacobian matrix is decomposed into singular values to simplify the solution and improve the calculation accuracy.The kinematics model corrected by geometric error parameters is used to compensate the errors,which can effectively improve the pose accuracy of the mechanism end.Finally,the vibration error of the end of X axis body in the mechanism is analyzed.The X-axis body is regarded as an axially moving flexible cantilever beam,and the vibration response equation of the axially moving cantilever beam is derived by considering the dead weight effect and the aerodynamic load.Taking the X-axis body as an example,taking the X-axis body as an example,the vibration law of the end of X-axis body is studied under different velocities and different vehicle model masses.Comparing the vibration response results of the homogeneous cantilever beam modal function and the end-concentrated mass cantilever beam modal function,the equivalence of the two under certain conditions is obtained.It laid the foundation for improving the position accuracy of the mechanism through vibration suppression.