Research On Key Technology Of A 6-DOF Mechanism On Wind Tunnel

Wind tunnel test is scaling down the test object by a certain proportion and put it into the flow field of the test section.The relative principle of the movement is used to create artificial air flow simulation aircraft in various states in the air to obtain simulated experimental data and verify the performance of the aircraft.The essential part of aircraft research is indispensable.In order to improve the wind tunnel test capability of China and provide comprehensive data support for the development of new types of aircraft and rockets,a 6-degree-of-freedom(6-DOF)mechanism for simulating the movement trajectory of external objects separated from the parent aircraft is required.In order to meet the requirements of the wind tunnel test,this paper studies the kinematics,dynamics,error and dynamic stiffness analysis of the 6-DOF mechanism.Based on the 6-DOF mechanism design of the wind tunnel,the D-H parameter method was used to establish the relationship between the spatial description and the coordinate transformation of the mechanism.A kinematics model was established,and the forward kinematics solution was solved to verify the correctness of the solution in the three-dimensional model.For the characteristics of the series mechanism,the kinematic inverse solution of the 6-DOF mechanism of the wind tunnel was deduced by analytical method.Using Robotics Toolbox,the Kinematics forward and inverse solutions were simulated of the 6-DOF mechanism of the wind tunnel.The parameters of each joint motion curve were obtained,and the correctness of the established kinematics positive solutions and inverse solutions was verified,and the rationality of the structural design of the 6-DOF wind tunnel mechanism was also verified.Using the energy-based Lagrangian function to construct the dynamic model of the 6-DOF mechanism of the wind tunnel,and based on this,the virtual prototype of the 6-DOF mechanism of the wind tunnel is established in the ADAMS,and the dynamic simulation is performed.The force/torque,power,speed/angular velocity,acceleration/angular acceleration and other movement curves required to meet the wind tunnel performance indicators.For the error analysis of the mechanism,an error model is established for the mechanism based on the kinematics analysis.Then,the error of each joint is set and the error model is solved to predict the error value at the end of the mechanism.Then the error is identified and the error is determined by the nonlinear over-determined equations.It is solved by an improved least squares iteration to obtain the final parameter difference.Randomly choose 100 groups of poses,calculate the parameter error values from the new substitution,compare the errors before and after compensation,and make the final accuracy of the mechanism greatly improved.In order to improve the dynamic stiffness of the 6-DOF mechanism of the wind tunnel,the modal response analysis and harmonic response analysis of the 6-DOF mechanism of the wind tunnel were performed to find the weakest resonance point of the mechanism.Then,by rigidly processing each structural member and the joint surface,the degree of influence of the structural member on the resonance frequency of the entire mechanism is compared,and the structural members that have a large influence on the dynamic stiffness of the mechanism are identified.For the weak dynamic link of the mechanism,the sensitivity analysis method was used to optimize the design of the weak structural parts,and the dynamic stiffness of the 6-DOF mechanism of the wind tunnel was effectively improved.