220 results about "Numerical stability" patented technology

A method of digitally correcting the raw output voltage from a Capacitive Voltage Transformer (CVT) with the intent to remove transient components impacting on transient accuracy of protection function. A typical CVT is represented using three parameters in the linear CVT model. A digital filter designed based on the three parameters and incorporating a dedicated mechanism to ensure numerical stability of the former. A method of self-adjusting the said filter based on system events and performed after the method has been deployed in the field and supplied from a specific CVT.

The invention discloses a CT imaging system and a method. The method includes: conducting common CT scanning on an object to obtain a common CT image, then determining an area-of-interest in the image, making use of a photon counting detector to perform CT scanning on the area-of-interest from multiple energy windows, and then re-establishing a high resolution image of the area-of-interest. The photon counting detector is employed to collect the photon counting projection data of multiple energy windows, so that decomposition of multiple basis functions can be carried out, the energy spectrum can have high discrimination, and the numerical stability can be good.

The invention discloses a topological optimization method based on a meshfree RKPM (reproducing kernel particle method) for a thermal structure of an anisotropic material. The method comprises a step of establishing a meshfree RKPM thermal stiffness matrix of the structure of the anisotropic material with a transformation matrix method, and the step comprises the following sub-steps: (1) solving dynamic influence domain radius of each calculation point according to coordinate information of input nodes and Gaussian points; (2) solving relative density of each RKPM node according to an RAMP (rational approximation of material properties) material interpolation model; (3) searching Gaussian points in a design domain, and establishing thermal conductivity tensor of each node according to the thermal conductivity of the anisotropic material, an orthotropic factor and a material direction angle; (4) taking a dot product of a thermal conductivity coefficient matrix and a geometric matrix of each node as an RKPM thermal stiffness matrix of the node; (5) forming the integral RKPM thermal stiffness matrix in the design domain. According to the method, topological optimization of the thermal structure of the anisotropic material is performed on the basis of the meshfree RKPM, the transformation matrix method and the RAMP material interpolation model, and the numerical stability is high.

A calibration method based on star field for the star-sensitive sensor includes such steps as creating a posture conversion array of star-sensitive sensor, creating the distortion model of star-sensitive sensor, and eliminating the least square parameters.

The invention puts forward a finite-element reconstruction method for space weighting of auto-fluorescence imaging. The method uses a diffuse optical tomography (DOT) technique to precisely reconstruct optical parameters of main biological tissue. The method limits a possible real light-source region, and divides a whole reconstruction region into a light-source possible region and a light-source impossible region so as to improve the numerical stability and effectiveness of reconstruction problems and reduce the ill-conditioned property of BLT reconstruction problems. In order to avoid famous 'Inverse Crime' problems, the method adopts a Monte Carlo (MC) random method to simulate the process of transmitting light in the biological tissue. Then the invention puts forward a finite-element method based on a space-weighting unit and adopts a tolerant algorithm for linear constrained optimization problems to reconstruct light-source information.

The invention provides a multi-robot cooperative positioning algorithm based on a square root unscented kalman filter. The multi-robot cooperative localization algorithm comprises the following steps: 1, providing a dynamic model for automatically positioning multiple moving robots according to kinematical equations of the robots and measurement equations based on relative positions; and 2, by adopting an SR-UKF filter algorithm, wholly updating the system state by taking the relative positions as input, thereby achieving cooperative positioning of the multiple moving robots. By adopting the algorithm provided by the invention, the positioning precision and the real-time requirements of a system can be both considered, the calculation complexness is reduced, the time of the algorithm is greatly shortened, the semi-positive definiteness and the value stability of a covariance matrix are ensured, and technical support is provided for cooperative positioning of later multiple moving robots.

The invention discloses a FastSLAM method based on particle proposal distribution improvement and adaptive particle resampling. The method comprises the steps that 1, a square root transformation unscented Kalman filter is utilized to estimate optimal particle proposal distribution, and the pose state of a robot is sampled; 2, a square root volume Kalman filter is utilized to update feature map information corresponding to each particle; 3, an adaptive particle resampling method based on relative entropy is utilized to determine the quantity of particles needed at the current moment; 4, the pose stat of the robot and guidepost feature map information are determined according to a particle set obtained after resampling. A traditional FastSLAM algorithm is improved from the two aspects of quality and quantity of the sampling particles at the same time, thus, the numerical stability and accuracy of the algorithm in the estimation process are enhanced, and the quality of the sampling particles is improved; in the particle resampling process, the least quantity of the needed particles is dynamically determined according to estimation uncertainty, and therefore the calculation efficiency of the algorithm is improved.

The invention discloses a lithium-ion battery SoC (State-of-Charge) estimation method based on improved and self-adaptive dual unscented-Kalman-filters. The method mainly comprises the following steps: 1) establishing a state filter and a parameter filter of a lithium ion power battery based on an equivalent circuit model; 2) coupling the state filter and the parameter filter of the lithium ion power battery based on the equivalent circuit model, and building dual unscented-Kalman-filters; and 3) inputting operation parameters of a to-be-detected lithium ion power battery into the dual unscented-Kalman-filters, and carrying out parameter correction and stage-of-charge (SoC) estimation on a lithium ion power battery equivalent circuit model. According to the method in the invention, the effectiveness of cholesky decomposition is guaranteed, the problem that iteration is stopped due to the fact that a covariance matrix is indefinite caused by reasons such as an initial value error, noisedisturbance, calculation module floating point error and the like is overcome, and the numerical stability of the filtering process and the robustness of the algorithm are enhanced.

The invention belongs to numerical simulation of discharge of a Tokamak device in the field of magnetic confinement controlled nuclear fusion, and relates to a simulation method for controlling a newclassic tearing mode through resonance magnetic disturbance in Tokamak. According to the current data in the Tokamak upper coil assembly, the Biot-Savart law is used for solving an induced magnetic field; integrating is performed to obtain an expression of a polar magnetic flux corresponding to the induced magnetic field according to approximation of a large ring diameter ratio; a Fourier transform pseudo-spectrum method is utilized to transform magnetic flux into components of different moduli to obtain three-dimensional distribution of the components in a tokamak median form, the three-dimensional distribution is coupled into a magnetofluid equation, and the Crank-Nicosolson method is utilized to solve the evolution of the magnetic field with the resonance magnetic disturbance along with time, so that the influence of the magnetic field on the new classical tearing mode is studied. The method can simulate the physical processes of new classic mode locking, inhibition, field penetration and the like of the tearing mode, is high in calculation efficiency and relatively good in numerical stability, and is an efficient numerical method capable of accurately simulating an experiment.

The invention relates to the space cruising autonomous navigation method based on plural globe route sign. It includes the following steps: programming the navigation using minor planet table, processing navigation minor planet image, and determine the autonomous path. The center of figure of plural minor planet determines the path of craft. The error of craft path is very low. The location error could be closed to 100Km and the speed error could be bellow 0.3m/s. It could satisfy the path accuracy request of the detector.

The invention discloses a method for estimating the state of a three-phase four-wire low-voltage distribution network and belongs to the technical field of three-phase state estimation of distribution networks. The method comprises the following steps of firstly, by using a computer, inputting low-voltage distribution meter-reading electric data and a network structure which are acquired within any time section, and parameter information through a program, and initiating the data, the network structure and the parameter information; then calculating constant item parts of a node admittance matrix and a jacobian matrix; synthesizing a measuring equation and T-end point zero injection equation restriction, and taking a real part and an imaginary part of voltage as state variables to calculate unbalance amount, an index type weight function and the jacobian matrix; finally updating the state variables and performing astringency judgment to realize estimation on the state of the three-phase four-wire low-voltage distribution network. Active power and reactive power of a node can be independently calculated by the method, the adverse influence of bad data on an estimating result is prevented, and the method has the characteristics of high difference resistance, good astringency, good numerical stability and the like. The method is widely applied to the estimation on the state of the three-phase four-wire low-voltage distribution network.

The invention discloses a high-precision real-time stereoscopic visual positioning method utilizing the parallax space bundle adjustment. According to the invention, only a video streaming obtained by a stereo camera is utilized to carry out navigation positioning of a mobile robot, so that the high-precision real-time stereoscopic visual positioning method has complete autonomy; a U-SURF descriptor is utilized to carry out feature matching, so that the high-precision real-time stereoscopic visual positioning method has strong robustness on illumination variation, motion blur and large rotation and scale variation which are generated in the moving process; and due to the utilization of a parallax space bundle adjustment optimizing method, an autonomous navigation vehicle can also be subjected to accurate real-time positioning when traveling for a long distance, so that the high-precision real-time stereoscopic visual positioning method has the advantages of low degree of dependence on an optimal initial value, high convergence rate, high value stability and the like and compared with a stereoscopic visual positioning method utilizing the bundle adjustment, the high-precision real-time stereoscopic visual positioning method has higher positioning precision and higher speed. The integral stereoscopic visual positioning method disclosed by the invention has high calculating speed and can be operated on line in real time.

A stable and accurate reactor physics thermotechnical coupling calculating method can simultaneously obtain statuses of a neutronics field, a fluid field and a heat transfer field; all variables are simultaneously updated in an iteration process, so the method has better value stability when compared with a conventional coupling method; the method uses a simultaneous time-space neutron diffusion equation and a thermotechnical equation discrete equation to obtain a novel nonlinear equation group with larger scale; using a Newton iterative method to resolve values of the novel nonlinear equation group, wherein the Newton iterative method needs to calculate a Jacobian matrix of the equation group in each iteration step, so physics thermotechnical coupling calculation is difficult. The novel method builds a value relation between the diffusion equation and thermotechnical equation, and explicit calculation can provide the Jacobian matrix, so problems caused by approximation calculation f the Jacobian matrix can be prevented; in addition, the novel method inherits Newton method characteristics, and hopes to provide faster convergence speed.

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 discloses a robust digital audio watermark embedding and detection method based on polar harmonic transform. Advantages of great frequency domain localization features, multi-scale, redundancy and translation invariance, the features of non-stationary of greatly describing signals and maintaining the shape of the signals and the same length of audio frequency of each sub-band after decomposition with that of the original audio frequency of nonsubsampled wavelet transform are utilized; then great numerical stability of polar harmonic transform is also utilized, and watermarks are embedded in stable torque values to resist the normal signal attack; and then the synchronization code technology is combined. The experimental results indicate that normal signal processing can be resisted and the desynchronization attack can also be effectively resisted so that the method has great imperceptibility and robustness. Besides, the method also has advantages of being simple in design and easy to realize.

The method is capable of carrying out transient state emulation for hybrid power supply network by mixing tree and network in any proportion quickly. Comparing with general emulation method, the invention can treat irregular topological structure and multiple power supply source, considering input of resistance, capacitance, and inductance as stray parameter so as to provide high precision of emulation. Pretreatment technique and quick argument elimination technique based on incomplete Cholesky decomposition is adopted in the invention. Advantages are: raising efficiency greatly, high precision of emulation and stability of data, emulation of network of power source/ground wires in large scale independent on topology. The invention is also applicable to passive clock line, bus and signal network in IC.

The invention discloses a simulation method for the evolution of an electron cyclotron current profile in a tokamak. In the process of numerically simulating the evolution of the electron cyclotron wave drive current profile in the tokamak device, a drive current source is firstly described by using a Gaussian function; the evolution of the drive current under a specific magnetic field configuration is calculated according to a convection equation determined by a Fisch-Boozer theory; the magnetic field configuration under the correction of the drive current is calculated; the evolution of thedrive current continues to be calculated under the magnetic field configuration; and the simulation effect of long-term evolution is achieved through repeatedly calculating. The method disclosed by the invention has the beneficial effects that the evolution of the electron cyclotron wave-driven current profile under a real three-dimensional magnetic field configuration is realized; the drive current profile can be obtained at any time; in the meanwhile, the spatial distribution situation of the drive current can be more accurately described through the convection equation determined by the Fisch-Boozer theory; the calculation efficiency is high; the numerical stability is strong; and the method is a stable and efficient numerical simulation method.

The present invention discloses a self-adaptive finite element optical source rebuilding method based on single spectrum or mixed spectrum measurement. A prior feasible optical source area and a prior forbidden optical source area are confirmed by the optical characteristic parameter and the dissection structure information of a target rebuilding area. Partial gridding is optimized and decomposed by single spectrum or mixed spectrum light flux measurement data at the boundary of the target rebuilding area to be combined with multilevel self-adaptive finite element and a posteriori error estimation method, so as to obtain a fluorescent optical source inside the target rebuilding area. Therefore, based on the single spectrum or mixed spectrum boundary measurement data, the method of the present invention adopts the prior feasible optical source area to reduce the morbidity characteristic of bioluminescence tomography and ensures that the present invention can confirm the only solution; the self-adaptive finite element method is used for balancing gridding partitioning degree, algorithm efficiency and value stability and the partial gridding is optimized according to the posteriori error estimation, which improves quality, efficiency and robustness of the fluorescent optical source rebuilding.

The invention discloses a power distribution network fault positioning method based on algebraic relation description and the complementary theory, and the method comprises the following steps: collecting current out-of-limit information of each feed switch of a power distribution network through employing a main station, defining current state characteristic values of the switches, and determining whether each feed line has a permanent fault or not through employing the current state characteristic values of the switches; carrying out the positioning of a feed line fault segment according to the current state characteristic information uploaded by the feed switches; enabling the main station to send a switching-off command to an automatic switch at the feed line fault segment according to the positioning result of the feed line fault segment. The method employs algebraic relation modeling and an approaching relation theory. Compared with a matrix method, the method is easier for the consideration of fault tolerance, gets rid of dependence on a swarm intelligence algorithm based on logic relation modeling optimization fault positioning method, can employ conventional linear optimization to achieve the positioning of the feed line fault region, is good in numerical stability, is higher in fault positioning efficiency, and is suitable for the online fault positioning of a large-scale power distribution network.

The invention provides a background grid adaptive segmenting method in a DC resistivity no-unit method. The method comprises the following steps of determining distribution condition of medium, abnormal member, landform, electrode and the like in a two-dimensional ground electric model, establishing a DC resistivity no-unit method calculating domain, and utilizing an irregularly distributed node discrete ground electric model; covering the calculating domain by means of a small number of rough and simple initial quadrangular grids, setting a control value which guides adaptive segmentation, and performing adaptive segmentation by the background grid according to the control value and a node distribution condition; arranging ng Gaussian integration points xg in each background grid, and obtaining a no-unit method equation set of the region; solving the equation set for obtaining a node electric field value, and calculating the vision resistivity parameter of a viewing point. The methodcan be based on any node distribution discrete model. High adaptability for any complicated ground electric model is realized. The background grid adaptive segmenting method improves value stability and computing efficiency in routine DC resistivity no-unit method forward calculation.