99 results about "Runge–Kutta method" patented technology

The invention discloses a high-precision integrated navigation positioning method for an underwater glider. The method comprises the steps that output of an inertial measurement unit (IMU) is subjected to rough processing and fine processing; higher-precision data is obtained; data obtained by dead reckoning based on a Runge-Kutta method (RK4) is combined; adaptive Kalman filtering (AKF) and unscented Kalman filtering (UKF) are conducted; the filtered data is fed back to the IMU; an accumulative error of the IMU is corrected; and relatively accurate information such as position, speed and gesture is finally output. The autonomous navigation method for the underwater glider has the advantages of high precision, real-time performance, stability, and the like, so that a whole navigation system can stably operate at long endurance, high precision and low power consumption, the current position and gesture information of an underwater aircraft can be obtained rapidly and accurately, and navigation path and position parameters can be provided for the underwater aircraft.

A real-time detection method of a soft abrasive flow abrasive group comprises the following steps: 1) establishing a phase-field model two-phase interface mixed energy equation according to the distribution condition of the soft abrasive flow abrasive group, also establishing a control equation of the phase-field function evolution, finally approximating a viscous phase and a surface pressure phase by a traditional second order center difference scheme, performing spatial discretization reconstruction of the control equation by a fifth order WENO scheme, performing discretization in the time direction by a Runge-Kutta method with a TVD property, and thus solving the two-phase interface to obtain a theoretical model of the abrasive group distribution; 2) performing real-time image processing of the distribution area of the abrasive group in a constraint channel obtained by a soft abrasive flow image acquisition device according to the obtained theoretical model of the abrasive group distribution, and thus extracting a contour feature of the abrasive group distribution area to obtain the change condition of the abrasive group dynamic boundary. The invention effectively detects the distribution condition of the soft abrasive flow abrasive group.

The invention provides a rapid trajectory optimization method of a rocket power lowering landing process, discloses a fuel optimal power lowering landing rapid trajectory planning method, and belongsto the field of rocket guidance. An implementation method includes the steps that dynamics modeling and dimensional normalization are conducted on power lowering flying, and a three-dimensional dimensionless dynamics equation is established; an independent variable of the dynamics equation is changed from the time to the height; by introducing constraints required for power lowering flying, an optimal control problem of fuel optimal power lowering landing is established; a nonlinear dynamics equation in the original optimal control problem is treated as a linear dynamics equation; a part of the nonlinearity is retained and transformed into a constraint, a non-convex constraint is convexified, and a convex optimal control problem is established; the convex optimal control problem is discretized at non-uniform discrete points by using a four-order Runge-Kutta method, and a second-order cone programming problem is established; and the second-order cone programming problem is solved iteratively until converging, and trajectory planning of power lowering landing flying can be achieved. According to the rapid trajectory optimization method, the advantage of high efficiency is achieved, and the safety and the reliability of landing of the rocket power lowering stage can be improved.

The invention discloses an axial symmetry DC magnetic bias simulation model for an extra-high voltage transformer, which belongs to the technical field of safe operation of electrical equipment in an extra-high voltage AC network. Through establishment of an equivalent axial symmetry simulation model of an actual three-dimensional model of the extra-high voltage transformer, a complicated magnetic field model is equivalent to a simple two-dimensional magnetic field model and dynamic inductance parameters are obtained; a load DC magnetic bias circuit model of the extra-high voltage transformer is established; current parameters are obtained through a four-order Runge-Kutta method; a time domain field-circuit coupling method is adopted to realize rapid calculation of the load DC magnetic bias of the extra-high voltage transformer; the simulation proves the high precision and high efficiency of analysis of DC magnetic bias through the extra-high voltage transformer to bring convenience to a large amount of researches on a DC magnetic bias problem of the transformer and help to safe and stable operation of the transformer.

The invention provides a three-dimensional numerical simulation method for ship large-scale rolling motion, which comprises the following steps of reading a grid file to carry out ship hydrostatic calculation; calculating an influence coefficient matrix of boundary integral equation for Taylor expansion boundary element method; solving velocity potential of laminated modes and its spatial first and second derivatives and mj terms; carrying out the green's function in time domain and its spatial derivative solution; calculating a roll damping coefficient; carrying out the irregular wave decomposition, linear superposition into incident wave time calendar; carrying out the direct time-domain disturbance wave force calculation by taylor expansion boundary element method; calculating incidentwave force and hydrostatic recovery force; modeling a large-scale motion forecasting equation; using the fourth-order runge-kutta method to solve the motion equation step by step to evaluate the nonlinear motion of the ship in the top wave or oblique wave; and carrying out the numerical simulation and characteristic statistics of ship large amplitude motion in irregular waves. The method of the invention can predict the large amplitude motion of a container ship in regular waves and irregular waves, and can be used for numerical simulation and characteristic statistics of the large amplitude motion of a ship in irregular waves.

The present invention discloses a predictive interpolation algorithm for a high-speed and high-precision parameter curve. The predictive interpolation algorithm comprises the following steps of S1, calculating the parameter value of each interpolation point of a parameter curve according to the Runge-Kutta method; S2, according to the constraint condition of the machining precision and the normal acceleration, adjusting the feeding speed of the interpolation point in the self-adaptive manner; S3, according to the deviation between a theoretical value and an actual value for the feeding step length, correcting parameters; S4, finding out the extreme point of the feeding speed and subjecting the curve to predictive segmentation; S5, according to the extreme point of the feeding point, sequentially subjecting each prospective interpolation interval to acceleration and deceleration control. According to the technical scheme of the invention, based on the Runge-Kutta method, interpolation parameters are calculated, so that the high-order derivation of the parameter curve is not required. Therefore, the algorithm complexity is reduced and the real-time performance of the algorithm is improved. Based on the relationship between the extreme point of the speed and the length of the interpolation interval, the feeding speed during the rough interpolation process is planned for a second time. Therefore, the fluctuation of the feeding speed is reduced, and the machining precision is improved.

The invention relates to an observing method of a rotor flux linkage in a vector control system of an induction motor. The observing method comprises the steps of conducting digital filter processing on acquired current signals and voltage signals by an FPGA (Field Programmable Gate Array), and removing noise interference, obtaining a three-phase current value, establishing a induction motor vector type dynamic mathematical model, constructing an observer in a full-order flux linkage state, conducting discretization on the observer in the full-order flux linkage state by adopting a high-precision four-order Runge-Kutta method, conducting real-time processing on the discretized data by utilizing a DSP (Digital Signal Processor) to realize the rotor flux linkage observation, calculating rotor flux linkage components psi r alpha and psi r beta under an alpha-beta coordinate system to complete the magnetic field orientation subjected to vector control, and determining the magnetic field orientation subjected to vector control through a formula. According to the observing method provided by the invention, the rotor flux linkage can be accurately observed under the alpha-beta coordinate system in the full revolving range without any switching mechanism; and the effectiveness and the stability of the vector control are ensured, the inhibition capability to the parameter change of the induction motor and the noise interference of the current detection is strong, and the robustness of the whole control system is promoted effectively.

The invention provides a pollution propagation mode visual analysis method and system based on time sequence particle tracking. The pollution propagation mode visual analysis method includes the steps: firstly, meteorological factors are comprehensively considered, and a Runge-Kutta method is adopted to track the motion trails of air pollutant particles, and an air pollution propagation model is constructed, and a pollution source is inspected through MIC correlation, influence frequency and a conveying mean value; then the air quality feature vectors of the target station is clustered by adopting an SF-kmediods algorithm to extract a propagation mode; and finally, a visual analysis system including a map, a thermodynamic diagram, a radar map and other views is designed and achieved, and an air pollution propagation mode is explored from multiple perspectives, and an analyst is assisted in making a more reliable air joint treatment scheme.

A method for analyzing a severe accident of a PWR nuclear power plant comprises: 1. calculating a behavioral characteristic of an early-stage core and a stress-strain characteristic of a fuel assembly of a severe accident; 2. calculating core melting; 3. calculating a core debris bed characteristic; and 4. analyzing and calculating a configuration of a melting matter in a head of a pressure vessel, wherein, a heat transfer between the melting matter and a surrounding material is calculated by a Runge-Kutta method at first, then steam flow that is released from the melting matter to the core during a cooling convection process is calculated, then mass and energy exchange between particles of the melting matter and a surrounding environment is calculated, and finally heat flow from a debris hard shell is calculated according to an inner temperature of the hard shell. Based on analysis of the mechanism and sequence of the severe accident of the large pressurized water reactor, management strategies and mitigation measures for severe accidents applicable to pressurized water reactors in our country are put forward, and technical support is offered for formulation of safety strategies of severe accidents of nuclear power plants in our country.

The invention discloses an electric power system transient stability calculation method based on a semi-implicit Runge-Kutta method. The method includes: establishing a dynamic element model for transient stability simulation calculation of the power system; forming a whole system differential algebraic equation set; inputting raw data and information, carrying out tide calculation, obtaining an operation parameter initial value before system disturbance; calculating an initial value of the state variable; generating a Jacobian matrix and a network admittance matrix of each dynamic element; performing system disturbance judgment; generating a Jacobian matrix of the differential equation set of the whole system; solving and obtaining the value of each state variable at the next moment; carrying out machine network alternate iterative computation, obtaining an operation parameter value at the next moment until a convergence condition is met, and taking the operation parameter value as aninitial value to calculate the next step length. The calculation is simple and stable, the larger step length can be used, the problem that the numerical stability and the calculation efficiency of the algorithm are difficult to consider at the same time in the transient stability simulation calculation is solved, and the method is more efficient, accurate and stable.

The invention provides a transient energy function method in consideration of VSG inverter current limitation. The method comprises the steps that a current limitation model of an inverter is built; the power-angle characteristic under inverter current saturation is obtained; a system power-angle model in consideration of inverter saturation under a VSG strategy is built; an improved inverter current saturation element model is built, and a relation of an improved power angle and an unsaturated power angle is obtained; main parameters of electric parts are input; a Runge-Kutta method is used for solving a rotor motion equation to obtain delta(t) and dotted delta(t) of a VSG rotor, so that a fault trajectory is obtained, wherein delta(t) represents a relation of the system power angle and time, and dotted delta(t)=w(t) represents a relation of the system angular velocity and time; transient energy Vcl and critical energy Vcr of the system at the fault clearing time are obtained; the obtained transient energy Vcl and critical energy Vcr of the system at the fault clearing time are compared, if Vcl is smaller than or equal to Vcr, the system is stable, otherwise, the system is not stable; critical fault-clearing time is solved.

The invention provides a boundary processing technology when the flow field calculation is performed by a WENO difference method. The consistent high accuracy can be achieved when the flow field calculation is performed and the complicated boundary can be processed. The boundary processing technology mainly comprises step 1, grid division, wherein grids are divided into an internal area and a boundary area, the boundary area only comprises a layer of grids, and accordingly the complicated calculation of the boundary area DG is minimized; step 2, space dispersion, wherein the space dispersion is performed on the internal area by the WENO finite difference method; step 3, boundary processing, wherein the space dispersion is performed on the boundary area by a DG method; step 4, coupling processing, wherein the coupling is performed on the boundary processing portion and the internal area and the derivative information is provided by the boundary area through DG polynomial approximation; step 5, time dispersion, wherein the time dispersion is displayed by a TVD-Runge-Kutta method; step 6, post-processing, wherein the visual stimulation is performed on a flow field result through commercial software such as Tecplot or Paraview.

The invention discloses an oil-immersed transformer cooling control method based on temperature rise and load rate. The method comprises the following steps: 1) collecting a transformer off-line and on-line data, 2) establishing a transformer hot spot temperature theta hs calculation model, and solving the current hot spot temperature theta hs of the transformer by adopting a Runge-Kutta method; 3) performing the sliding range processing on the real-time data of the transformer top oil temperature theta top, the winding hot spot temperature theta hs, and the load rate K, 4) formulating a cooling system control strategy; and 5) adjusting the operation mode of the cooling system, and improving the safety and reliability of the transformer. According to the method, input data are preprocessed, frequent switching caused by fluctuation of the temperature or the load of the transformer cooling system near the threshold value is avoided, and the safety and reliability of the cooling system and the transformer are improved. Meanwhile, the heat state evaluation accuracy of the transformer is improved by integrating various information, and a foundation is laid for fine management of the cooling system.

The invention provides a method for pre-estimating flight path of a wind tunnel free flight test model, and the method comprises the steps: 1, obtaining an attack angle - mechanics coefficient table of a flight model; 2, setting the initial attack angle value theta0 of a free flight test, a transmission position, and an initial transmission speed, obtaining the mechanics coefficient at the initial attack angle value theta0 through linear interpolation, and enabling the initial attack angle value theta0 and the corresponding mechanics coefficient to serve as an initial transmission parameter D0; 3, calculating and obtaining pre-estimated flight path data through a Runge-Kutta method after flight at the transmission position; 4, repeatedly carrying out the steps 2 and 3 when the pre-estimated flight path data does not meet the testing requirements, obtaining a new pre-estimated flight path, and carrying out step 4 till the new pre-estimated flight path meets the testing requirements. The method pre-estimates the flight path of free flight of a model in a wind tunnel, enables the flight path to stay for longer tie in an observation region, and obtains more effective information during testing.

The invention provides a simulation method applicable to a space tethered system of a stratospheric satellite system. The method comprises the steps of averagely dividing a tether to be a plurality of sections with the same length, building a mathematic model for the stratospheric satellite system, deriving a node constraint equation and solving a second derivative according to the position relationship between a node and each section of the tether, and performing integral solution on the equation by using a fourth-order Runge-Kutta method, so as to finish a simulation task for the tethered system of the stratospheric satellite system. According to the simulation method provided by the invention, with a view to the gravity and softness of the space tethered system, the accuracy and effectiveness for transferring the magnitude and direction of the control force by the space tethered system can guaranteed.

The invention provides a method of extracting a weak target signal in ocean current interference. The method comprises the following steps: ocean magnetic field variation information f0i is acquired; multi-scale decomposition is carried out on the f0i to obtain a signal f1i; a stochastic resonance method is adopted for the f1i; a fourth-order Runge-Kutta method is used for high-accuracy numerical value solution on a nonlinear stochastic resonance system; optimal stochastic resonance parameters are found out; the best resonance output data sequence f2i is solved; multi-scale decomposition is carried out on the f2i; different thresholds are selected in a main frequency band interval where the target signal is to rebuild a signal f3i through threshold processing; feature extraction is carried out on the f3i; and extracted feature parameters are matched and compared with a database for underground target motion. Abnormal target disturbance magnetic field features are screened from complex ocean background electromagnetic interference, a passing underwater moving target can be indirectly detected, discovered and recognized, and the underwater prediction and early warning ability can be effectively improved.

The invention discloses a tower crane anti-swing operation control method. The method comprises the steps that crane operating parameters are input; the crane transport time is equally divided into Nsegments, an accelerated speed curve on each segment is approached through a one-time straight line method, and a state curve is calculated through a four-step Runge-Kutta method; and an SQP optimization algorithm is adopted to optimize the control parameters of the segmented straight line, and the optimal accelerated speed control curve is obtained.

The invention relates to a method for constructing a measurement matrix of a compressed sensing magnetic resonance image based on a chaotic system, and relates to a method for constructing a measurement matrix of a magnetic resonance image. The purpose of the present invention is to solve the problem of poor incoherence characteristics of the measurement matrix constructed by the existing method. The present invention utilizes the Runge-Kutta method to solve the Rossler chaotic differential equations to obtain the track of the Rossler chaotic system; intercept a part of the x-y plane phase diagram of the Rossler chaotic system according to the FOV of k space as the chaotic measurement track curve; The maximum gradient amplitude of the gradient field of the magnetic resonance imaging scanner and the maximum conversion rate of the gradient magnetic field are used to calculate the time-optimal gradient waveform of the curve; the curve is rotated along the center of k-space, and the final chaotic measurement matrix is ​​obtained through multiple excitations . The measurement matrix of the invention has better non-coherence characteristics, and the reconstruction image obtained by using the measurement matrix constructed by the method of the invention has a better effect.

The invention provides a model predictive flux linkage control-based direct torque control method for a switched reluctance motor. The direct torque control method at least comprises the following steps of measuring a current of a stator, a rotating speed of a rotor, a position of the rotor and a voltage of a direct-current link through sensors; calculating flux linkage of the stator and a torqueof a motor at a K moment; through a hysteresis ring controlled by the torque, comparing a torque value at the current K moment with a torque value set by a PI ring, and selecting out three to-be-selected voltage vectors; substituting the to-be-selected voltage vectors into a second-order Runge-Kutta method formula to predict the current of the stator at the K+1 moment; predicting a flux linkage value of the stator at the K+1 moment through the current of the stator at the K+1 moment; comparing a predicted flux linkage value psi k+1 of the stator at the K+1 moment with a given flux linkage value psi ref; selecting a Uk+1 voltage vector for minimizing an evaluation function through the evaluation function; sending a switch signal corresponding to the selected optimal voltage vector to a three-phase asymmetric bridge converter; and performing control on the switched reluctance motor.

The invention discloses a hydrostatic rotary table kinematic error modeling and computing method. The method comprises the steps that a single oil pad theoretical model based on the reynolds equation works out pressure distributions of a prepressing oil pad and a bearing oil pad during kinematic error considering, and then integration is carried out on pressure distributions to obtain bearing force Fy, Fi and Fj of the prepressing oil pad and the bearing oil pad; the oil film thickness of each oil pad is simplified to be the oil film thickness of the center of the oil pad, rotary table machining contour errors are considered and form functions in a fitting mode, and the oil film thickness and speed of each oil pad are determined according to the geometrical relationship between the oil film thickness of the oil pads; a kinetic equilibrium equation of the rotary table is built; the kinetic equation of the rotary table is solved in the Matlab software through the Runge-Kutta Method, so that influences of main parameters such as the rotary table rotating speed, the machining contour errors and the like on the kinematic error are obtained, and a reasonable range is provided for the hydrostatic rotary table machining precision.

The invention relates to a mine gyro clinometer strapdown inertial navigation system attitude calculation and zero-speed correction method, wherein the measurement data of an attitude sensor is used as input information, the mechanical arrangement equation of a strapdown inertial navigation system is solved through different orders of Runge-Kutta methods, the attitude angle information and the position information of a current drill bit are real-timely output, and the cumulative error of the strapdown inertial navigation system is eliminated through a zero-speed correction algorithm. According to the present invention, the gyroscope and the accelerometer are used as the measurement unit of the strapdown inertial navigation system, the mechanical arrangement equation of the strapdown inertial navigation system is solved through the different orders of the Runge-Kutta methods, the attitude angle information and the position information of the current drill bit are real-timely output, the magnetometer is used as the external assisted measurement device to eliminate the cumulative error produced after the long-time work of the strapdown inertial navigation system, and the combination navigation of the multi-sensor is achieved through the zero-speed correction algorithm, such that the accuracy of the drill bit trajectory measurement can be improved.

The invention provides a partial discharge signal detecting method based on a coupled Duffing oscillator, comprising the following steps: obtaining a to-be-detected digital signal after passing a to-be-detected signal through an A/D converter; inputting the to-be-detected digital signal into a coupled Duffing oscillator system; using the fixed-step-size fourth-order Runge-Kutta method to solve thedifference of the state variable between oscillators; and regarding the difference of the state variable between oscillators as a partial discharge signal in the to-be-detected signal. The method ofthe invention adopts the Duffing oscillator system composed of three oscillators, achieves the strong noise suppression capability and can effectively detect the partial discharge signal; the coupledoscillator is solved by initial value recursion, the operation speed is better than that of the existing method, and the method is suitable for real-time operation and has an advantage in the on-linedetection system of the discharge signal; and the narrow signal detection capability is superior to that of the existing detection method.