| Flow field quality is an important indicator to measure the performance of wind tunnels.The nozzle section acts as the core section of the wind tunnel and directly affects the wind tunnel test flow field.The semi-flexible wall nozzle can realize the continuous adjustable Mach number,which is of great significance for reducing the economic cost of the wind tunnel nozzle and improving the operation efficiency of the wind tunnel experiment.In this paper,the multi-pivot multi-drive semi-flexible wall nozzle mechanism of a wind tunnel is taken as the research object.Based on the analysis of the current driving form and function of the semi-flexible nozzle RPR,the driving form of PRR is proposed,and the semi-flexible nozzle is carried out.Kinematics,dynamic and static performance analysis.Based on kinematics,a laryngeal error analysis model is established,and an error compensation algorithm is proposed to improve the motion accuracy of the laryngeal mechanism.The driving force and trajectory of each group of actuators are optimized to improve the accuracy of the mechanism profile.The simulation is verified to provide a theoretical basis for the precise molding of the machine surface.Under the constraint of space installation size and driving force,the length and angle of the laryngeal actuator are designed.According to the characteristics of the 3-PRR parallel actuator,the inverse equation of kinematics is established by coordinate transformation.The arc length remains constant during the deformation process of the plate to establish the inverse equation of the kinematic kinematics.Based on the static and dynamic characteristics theory,the static analysis of the RPR and PRR driving modes of the semi-flexible wall mechanism is carried out,and the stress and deformation of the two driving forms under three important working conditions are obtained,which proves that the PRR driving form stiffness is better than the RPR driving form.The modal and harmonic response analysis is performed on the semi-flexible wall mechanism,and the first six natural frequencies and vibration modes and lateral stiffness of the mechanism are obtained.Can guide the organization to use safely.In order to improve the motion accuracy of the laryngeal block,based on the kinematic equation of the laryngeal block,the 3-PRR mechanism error model is established by matrix differential method.The error influence factor method is used to analyze the influence of each error source on the end pose of the mechanism.The total transfer matrix performs singular value decomposition,and obtains the sensitivity calculation expression of each error source.By actively controlling the slider displacement to compensate the mechanism,this method can effectively reduce the influence of the error source on the end position of the mechanism,and can improve the mechanism.Motion accuracy and nozzle profile forming accuracy.Five-degree polynomial is used to plan the trajectories of each group of actuators.Based on the rigid-flexible coupling dynamics theory and combined with PATRAN/NASTRAN and ADAMS software,the rigid-flexible coupling dynamics simulation of throat and flexible plate is carried out.The rationality of trajectory planning method and mechanism design is verified,which provides a theoretical basis for synchronous and coordinated control of semi-flexible wall nozzle profile forming. |
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