18 results about "Euler equations" patented technology

The invention discloses a freight spaceship reentry recovery attitude cooperative control method. The method comprises the following steps: S1, determining key attitude indexes in a freight spaceship reentry recovery process; s2, collecting atmospheric environment parameters in a reentry process, and meanwhile, obtaining earth gravitational field distribution data to provide environment input for a subsequent attitude control algorithm; s3, based on the Newton's second law and the Euler equation, establishing a kinetic model of the freight spaceship, establishing an attitude kinematics model by adopting a quaternion method or an Euler angle method, and establishing an execution mechanism model for a propulsion system of the freight spaceship; through sub-filter local estimation and main filter global weighting, noise and abnormal values are effectively filtered, attitude estimation precision is improved, instruction distribution adopts a pseudo-inverse method in combination with a weighted least square method, an initial instruction is obtained through the pseudo-inverse method, then secondary optimization is performed in combination with execution mechanism constraints, instruction oversaturation is avoided, and attitude estimation accuracy is improved. Extra redundant execution mechanisms are not needed, and the hardware cost is reduced.

The invention discloses a multiphase fluid compressible and weak compressible mode mutual conversion numerical simulation method, and relates to the technical field of underwater explosion bubble full-time-history simulation, the method adopts a compressible Euler equation to carry out numerical simulation at the initial stage of underwater explosion, i.e., the initial stage of condensed phase charge detonation and bubble expansion; at the later stage of bubble expansion, converting a compressible Euler equation into a weak compressible hypothesis method for processing by judging whether the density change of a fluid grid unit exceeds a set threshold value or not; and in the bubble shrinkage stage, the compressible Euler equation is adopted again for numerical simulation, and underwater explosion bubble full-time-history numerical simulation is achieved. A volume fraction method is adopted in the equation solving process, the MUSCL reconstruction format and the HLLC numerical flux calculation format are coupled, and the prediction precision, stability and robustness of the overall numerical calculation method are improved.

The invention relates to a four-axis unmanned aerial vehicle PID control system parameter setting method based on a Harris eagle optimization algorithm, and belongs to the field of embedded systems. According to the method, the limitation that traditional PID parameter setting depends on artificial experience, efficiency is low and global optimum is difficult to approach is broken through, and autonomous and efficient optimization of the parameters of the PID controller of the unmanned aerial vehicle is achieved by introducing the Harris eagle optimization algorithm and utilizing the collaborative hunting strategy and the self-adaptive escape energy mechanism of the Harris eagle optimization algorithm. The method comprises the following steps: firstly, establishing a six-degree-of-freedom kinetic model of the four-axis unmanned aerial vehicle based on a Newton-Euler equation, taking parameters of an inner ring PID controller and an outer ring PID controller as optimization variables, and designing a multi-target fitness function fusing ITAE indexes, overshoot and adjustment time; then, executing intelligent search in a parameter space by utilizing a Harris eagle algorithm; dynamically switching global exploration and local development through escape energy, and gradually approaching an optimal parameter; and finally, the optimized parameters are deployed to a flight control system, and high-precision robust control over the attitude and the position in the complex disturbance environment is achieved.

The application provides a method for testing and visualizing analysis of sound wave generation and propagation process, comprising the following steps: S1, installing acceleration sensors at different positions of a mechanical structure generating intense vibration, measuring vibration state of the mechanical structure, and characterizing vibration features of the mechanical structure based on vibration acceleration data of the acceleration sensors at different positions and interpolation; S2, calculating normal sound wave speed variables of particles at the surface of the mechanical structure in air or water medium based on normal acceleration fluctuation variables of the vibration features of the mechanical structure; S3, using linear Euler equation to describe evolution states of energy dissipation, sound scattering and sound reflection of the normal sound wave speed variables in the propagation process; and S4, performing data visualizing analysis based on the evolution states. The application improves the design capability of noise suppression of mechanical equipment, and enables intuitive observation of the generation and propagation states of sound waves by using visualizing analysis.

The application provides a sound flow coupling calculation method and device based on a Galbrun equation. The method provided by the application comprises the following steps: obtaining a Galbrun equation based on Euler equations of an ideal fluid under no external force, in combination with Euler disturbance, Lagrange disturbance and mixed disturbance relationship; the Galbrun equation represents the coupling effect of a flow field and a sound field; obtaining flow field data of a non-uniform flow field based on Navier-Stokes equations, in combination with a k-ε turbulence model in a RANS model; introducing a perfect matched layer for sound wave propagation simulation in an unbounded region, and constructing boundary conditions suitable for the Galbrun equation through geometric transformation, complex variable definition and coordinate conversion; performing weak transformation on the Galbrun equation, embedding the boundary conditions, combining the flow field data, adopting triangular finite elements for discretization processing, constructing a global linear algebraic equation group and solving, and obtaining discrete solutions of sound field parameters.

The application provides a shock wave front capturing method and system based on a physical information neural network, and relates to the technical field of computational fluid dynamics. The method comprises the following steps: obtaining target space-time coordinate data corresponding to a target explosion wave in a propagation process; inputting the target space-time coordinate data into an explosion shock wave front prediction model to obtain shock wave front information corresponding to the target explosion wave in the propagation process, which is output by the explosion shock wave front prediction model, wherein the explosion shock wave front prediction model is constructed based on an improved physical information neural network; and a physical loss function of the improved physical information neural network is constructed according to the Rayleigh-Hugoniot relation and compressible Euler equations with an artificial viscosity term. The application reduces the calculation complexity of the shock wave front while ensuring the prediction accuracy.

The application discloses a curve determination method for point-by-point integration of a centrifugal pump and belongs to the technical field of centrifugal pumps. u The curve determination method for point-by-point integration of the centrifugal pump is a parameterized modeling method based on Euler equation and momentum conservation, the inlet and outlet boundaries of the v r curve are calculated according to design requirements, a smooth transition curve is constructed by combining flow channel geometry and angle of attack constraints, the curve is constructed by dynamic correlation of streamline arc length through nonlinear interpolation, and the relationship between the streamline arc length and the curve is established; the centrifugal pump blade profile can be designed according to the given design conditions and the streamline arc length s through the parameterized method.

The invention discloses a parafoil system flight path tracking and anti-interference control method based on constant period sliding mode control, and the method comprises the steps: carrying out the stress analysis of a parafoil system, building a translation three-degree-of-freedom model and a rotation three-degree-of-freedom model of the parafoil system according to a Newton-Euler equation, and taking the models as a flight path tracking control basis; based on a sliding mode control principle, designing a basic sliding mode controller of the parafoil system, and obtaining a sliding mode control law by constructing a sliding mode surface and designing an approaching law so as to realize finite time stable tracking of a system state variable; for the inherent buffeting and overshoot problems of sliding mode control, a saturation function is introduced to replace a sign function, and a continuous and smooth switching law is designed in a sliding mode surface neighborhood to realize sliding mode control law optimization; and designing a constant period disturbance observer, estimating and compensating the total disturbance of the system in real time, and performing feedforward compensation on an observation value to a sliding mode control law, thereby enhancing the robustness and anti-interference performance of the system. The method has good trajectory tracking performance and anti-interference capability.

The invention discloses a compressible multi-component flow high-precision algorithm based on a pharmacology format, and the algorithm comprises the steps: S1, building an Euler equation as a control equation for a compressible multi-component flow problem, and introducing mixture parameters to describe a multi-phase interface; s2, a C-GKFS based on a simplified Maxwellian distribution function is adopted to carry out discretization on an Euler equation; and S3, reconstructing the non-viscous flux and the viscous flux in the C-GKFS by adopting a WENO-THINC format to obtain a high-order non-oscillation result. According to the compressible multi-component flow high-precision algorithm based on the kinematics format, by adopting the high-order target basically-oscillation-free hyperbolic tangent interface capture (TENO-THINC) format, the C-GKFS calculation precision is improved, and the compressible multi-component flow problem can be accurately and efficiently simulated.

This invention relates to a method and system for predicting the time-domain acoustic load on the surface of an aircraft, belonging to the field of aircraft detection technology. To address the problem of high-precision calculation of acoustic scattering in aircraft, this invention establishes a flow field calculation grid and an acoustic field grid; initializes the grid; calculates the Jacobian determinant and grid cell metric, and completes the grid coordinate system transformation; determines the convergence of the numerical solutions of the grid cells; iteratively solves the linear Euler equations at each time step using the Runge-Kutta method; obtains the flow field data and acoustic field data for each grid cell; performs filtering using a spatial filtering format to eliminate numerical artifacts, obtaining the filtered flow field data and acoustic field data for each grid cell; iteratively updates the flow field data and acoustic field data over time until the acquired acoustic load data stabilizes, outputting the time-domain data of the acoustic load on the aircraft surface, a flow field acoustic field cloud map, and a flow field cloud map. This invention balances computational efficiency and accuracy.

The invention discloses a lower limb exoskeleton control method with preset event triggering times, and belongs to the technical field of intelligent control and robots. The method comprises the following steps: according to a single-degree-of-freedom lower limb exoskeleton, constructing a kinetic model of the lower limb exoskeleton based on a Newton-Euler equation, and converting the kinetic model into a second-order nonlinear system; defining tracking error and auxiliary error variables; designing an event triggering mechanism with preset triggering times, constructing an ideal triggering interval, and introducing average residence time to constrain the upper bound of the triggering times, so that the triggering frequency is controllable; a fuzzy logic system is combined to approach system uncertainty, and a backstepping method is adopted to design an adaptive control law, an adaptive law and an adaptive threshold law; and the system is ensured to be consistent and finally bounded and stable by setting an average residence time condition. While the trajectory tracking precision is ensured, the communication burden is remarkably reduced, the triggering times can be preset and regulated, the method is suitable for a lower limb exoskeleton system with limited communication resources, and the practicability and the energy efficiency of the system are improved.

The invention discloses a flow-sound-control integrated active noise reduction simulation system and method, and belongs to the technical field of active noise reduction simulation. The system comprises a flow-sound coupling solving module, an ANC control algorithm embedding module and a closed-loop control coupling interface, the flow-sound coupling solving module is used for achieving native coupling simulation of a flow field and a sound field based on a linear Euler equation, and flow-sound coupling solving comprises grid topology construction, background flow field mapping, acoustic equation discrete solving and boundary condition construction; wherein the background flow field mapping is used for converting an original background flow field physical quantity into a physical quantity adaptive to the acoustic grid; the ANC control algorithm comprises an LMS algorithm and an FxLMS algorithm; and the closed-loop control coupling interface realizes real-time data interaction between the streaming sound coupling solving module and the ANC control algorithm embedding module to form a closed-loop system of sound field solving-control calculation-feedback regulation.

This invention provides a numerical solution method for weakly compressible aeroacoustics based on Roe Riemannian calculations, comprising the following steps: establishing a sound field computational domain; obtaining the ground-state flow field of the weakly compressible flow; mapping the ground-state flow field to the sound field computational domain; interpolating the center values ​​of the cells in the sound field computational domain to the interface between the cell and adjacent cells; calculating the mean value at the interface using Roe averaging; calculating the flux at the interface; and solving the acoustic control equations established using linearized Euler equations. This invention can be widely applied in the field of aerodynamic noise calculation technology.

The invention provides an acoustic streaming coupling calculation method and device based on a Galbrun equation. The method provided by the invention comprises the steps of obtaining a Galbrun equation based on an Euler equation of ideal fluid under the condition of no external force and in combination with Euler disturbance, Lagrange disturbance and a mixed disturbance relation; the Galbrun equation represents the coupling effect of the flow field and the sound field; based on a Navier-Stokes equation, in combination with a k-epsilon turbulence model in the RANS model, solving to obtain flow field data of the non-uniform flow field; a perfect matching layer is introduced for sound wave propagation simulation of an unbounded region, and boundary conditions suitable for the Galbrun equation are constructed through geometric transformation, complex variable definition and coordinate transformation; and carrying out weak transformation on the Galbrun equation, embedding the boundary condition, combining the flow field data, carrying out discretization processing by adopting a triangular finite element, constructing a global linear algebraic equation set, and solving to obtain a discrete solution of sound field parameters.

The invention provides a shock wave front capturing method and system based on a physical information neural network, and relates to the technical field of computational fluid mechanics, and the method comprises the steps: obtaining corresponding target space-time coordinate data of a target explosive wave in a propagation process; and inputting the target space-time coordinate data into an explosive shock wave front prediction model to obtain shock wave front information corresponding to the target explosive wave output by the explosive shock wave front prediction model in the propagation process, the explosive shock wave front prediction model is constructed based on an improved physical information neural network; the physical loss function of the improved physical information neural network is constructed according to a Rayleigh-Rayleigh Newton relationship and a compressible Euler equation with an artificial viscosity item. According to the method, the calculation complexity of the shock wave front is reduced, and meanwhile, the prediction precision is ensured.

This invention discloses a method for generating waves with accurate dispersion, comprising: determining model calculation parameters based on the basic parameters of the ocean region to be simulated; constructing a numerical model of ocean waves with accurate dispersion based on the model calculation parameters; and generating ocean waves with accurate dispersion using the numerical model of ocean waves. The numerical model of ocean waves includes: obtaining an integral-differential governing equation set based on the Euler equations and free surface boundary conditions through continuous Taylor expansion and Fourier transform; the governing equation set includes a continuity equation and a momentum equation; embedding physical process correction terms into the momentum equation based on the governing equation set with embedded physical process correction terms; and performing numerical discretization using the finite difference method based on the governing equation set after embedding the physical process correction terms, wherein time discretization uses a prediction-correction scheme and spatial discretization uses a higher-order difference scheme to achieve the generation of waves with accurate dispersion.

The present disclosure relates to the technical field of compressor analysis, and particularly provides a method and device for evaluating the flow stability of a compressor under thermal shock distortion, the method comprising: constructing Euler equations of a compressor to be evaluated; obtaining small disturbance equations of the compressor based on small disturbance assumption and the Euler equations, and solving the small disturbance equations based on flow field data in a thermal shock process to obtain small disturbance solutions of the compressor, the small disturbance equations being determined based on an assumption that disturbance amplitude variation of small disturbance is consistent with thermal shock distortion disturbance variation or an assumption that thermal shock distortion disturbance is periodic disturbance; determining boundary conditions of blades in the compressor based on a disk model and parallel compressor theory, and determining a system stability characteristic equation of the compressor according to the boundary conditions and the small disturbance solutions; and determining a flow stability evaluation result of the compressor according to a solving result of the system stability characteristic equation. The present disclosure reduces the difficulty of evaluating the flow stability of the compressor under thermal shock distortion.

The invention provides a dynamic base airborne photoelectric tracking system frame deep coupling dynamics modeling method, and belongs to the technical field of automatic control, and the method comprises the steps: building a machine body coordinate system, an outer frame coordinate system and an inner frame coordinate system, and building a conversion relation between the coordinate systems through the rotation around a shaft; the space-time mapping relation of the multi-stage motion of the machine body, the outer frame and the inner frame under different coordinate systems is constructed, and an airborne photoelectric tracking system kinematics model is established by representing the angular rates and the angular acceleration rates of the inner and outer frames; on the basis of a Newton-Euler equation, representing a stress motion law of the inner and outer frames, and establishing an airborne photoelectric tracking system dynamics model; and finally, distinguishing known items and unknown items of multi-source interference according to sensor measurement information, and obtaining a deep coupling frame model of the airborne photoelectric tracking system under the movable base through coordinate transformation. According to the invention, precise visual axis control of a photoelectric tracking system carried by a high-dynamic aircraft under multi-stage motion coupling is facilitated.