A hydraulic pipe is a basic component of the aero hydraulic system, while high pressure and high speed lead to the enhancement of multiple field coupling effects, such as the structure, fluid, heat, and sound of the aero hydraulic pipe. A larger elastic deformation of the pipe and the more common unsteady flow of fluid can aggravate the vibration and noise of the hydraulic pipe system. Based on the 14-equation model of fluid-structure-interaction (FSI) vibration of aero hydraulic pipe, a model suitable for a wide Reynolds number range is proposed by comparing and analyzing various kinds of friction coupling models. This model is used for the FSI dynamic behavior analysis of aero hydraulic pipes, which improves the accuracy of FSI frequency-domain solutions under high Reynolds number conditions. Second, based on the 14-equation model of FSI vibration of aero hydraulic pipe and the transfer matrix method, the mathematical model of airframe deformation load of an aero hydraulic pipe is established, and the evolution law of the FSI dynamic behavior of the aero hydraulic pipe under different airframe deformation loads is analyzed. All the above analysis results were verified by the experimental analysis. The error of the analysis results of the FSI vibration frequency is smaller than 5% compared with the experimental results. The results show that the proposed method is feasible and effective for predicting the hydrodynamic behavior of the aero hydraulic pipes under load conditions. INDEX TERMS Hydraulic systems, vibrations, pipelines, fluid-structure-interaction (FSI).

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Abstract:In order to estimate the motion state of the hypersonic glide vehicle, a motion model based on the aerodynamic parameters of the prototype CAV-H and an observation model of GEO infrared early-warning satellite were established. The exponential weighted recursive least square method with forgetting factor was used to measure the early-warning satellite observation data with measuring error in angle to obtain a fitting parameter describing the polynomial of the target state, The method can focus on the local motion of the target, dilute the influence of the early observation data on the fitting parameters, reduce the estimation error caused by the target manoeuvring. The simulation result shows that the estimation of both position and velocity of the hypersonic glide vehicle is highly accurate. , but IMM needs parallel computing which is not conducive to rapid response in wartime. And the accuracy depends on the accuracy of the motion model. This paper describes the spatial motion of HGV with high order polynomials, fit discrete observations with errors from GEO infrared warning satellite with Exponential Weighted Recursive Least Squares (EW-RLS), Using interpolation to obtain the position and velocity of the observation time and its neighborhood, Provides foundation for rapid ballistic and tracking observations of HGV targets. Simulation of typical trajectoriesAfter HGV re-enters the atmosphere, it can use aerodynamic force to continuously transform kinetic energy and potential energy, Jump in vertical plane to get out of the warning system to track. Horizontal manoeuvres can also be used to circumvent the impact of defensive weapons [6], In this section, a three-dimensional motion model of HGV reentry segment with control conditions is established based on the published aerodynamic parameters of the US Army's CAV-H prototype, Typical reentry trajectories are simulated and analyzed, which will lay the foundation for subsequent research on reentry interception methods.

In this article, the hydraulic drive unit that drives the movement of the joint of a legged robot was researched, aiming at improving the control accuracy of the position-based impedance control system with dual input and single output. The state feedback control containing more state information of the system was adopted to replace the traditional output feedback and proportional-integral-derivative (PID) control, through the real-time calculation of the time-varying parameters of the servo valve flow, the nonlinear state space expression of the system was derived, the state feedback matrix and the input transformation amplifier were obtained and the full-dimensional state observer was designed. The experimental results show that the designed full-dimensional state observer can track the state variables of the actual system better. Compared with the traditional output feedback and PID control, state feedback control performs better in aspects of accuracy and system dynamics for the position-based impedance control system, which can further improve the compliance performance of the robot.