66 results about "Electromagnetic field computation" patented technology

An electromagnetic positioning and navigation device for a transcranial magnetic stimulator is composed of an electromagnetic positioning and navigation module (1), a coil gesture control module (2), a three-dimensional seat (3), an image collection and processing module (4), an electromagnetic calculation module (5), a display module (6) and a transcranial magnetic stimulator coil (7). The electromagnetic positioning and navigation module (1) is connected with the coil gesture control module (2) and the three-dimensional seat (3), and the coil gesture control module (2) is installed on the transcranial magnetic stimulator coil (7). The image collection and processing module (4) can rebuild a three-dimensional head model of a patient in the image space to mark therapeutic targets. The electromagnetic positioning and navigation module (1) records space position and coil gesture of the head (8) of the patient and conducting alignment on head positions in the image space and the sensor space and the position of the transcranial magnetic stimulator coil (7). Induction field distribution of the head of the patient is displayed in the display module (6) by means of calculation of the electromagnetic calculation module (5).

An irregular mesh mapping method used in electromagnetic field-flow field-temperature field coupling calculation comprises the following steps of 1 establishing a flow field-temperature field calculation model; 2 reading node coordinate values of discrete units of the model; 3 re-establishing a geometric model of a research object in the electromagnetic field calculation, performing model discrete to form a triangular finite element mesh and performing electromagnetic field value calculation; 4 mapping power consumption onto units in a temperature field; 5 obtaining a mapping correction factor; using power consumption densities of the units as loads to be loaded into the temperature field for solution and calculation, and obtaining a temperature result; accordingly obtaining the power consumptions of the units in the temperature field. By adopting the irregular mesh mapping method used in the electromagnetic field-flow field-temperature field coupling calculation, data transfer of different types of meshes can be adopted in different physical fields, the mesh number is greatly decreased, and the calculation time and the calculation accuracy are shortened and improved.

The invention discloses an automatic implementation method for a high-uniformity magnet shim coil design. The method comprises the following steps of: measuring the magnetic field intensity distribution within a region range by utilizing a nuclear magnetic resonance probe, and fitting the first 10-order components of the magnetic field expanded according to spherical harmonics by utilizing a least square method so as to obtain the intensity value of the shimming quantity of each order; inputting a shimming intensity numerical value, selecting an algorithm, and then storing the shimming intensity numerical value and the algorithm; assigning the stored numerical value and algorithm to a shimming code module; loading a Radia three-dimensional electromagnetic field calculation packet into the shimming code module and carrying out optimal computation on the optimization model; optimizing the calculation result, calculating shim coil shape parameters, a coil three-dimensional structural drawing and an error iteration path by virtue of a linear programming method or a particle swarm optimization based on an analytical method; and manufacturing a shim coil according to the calculated specific coil shape parameters and coil three-dimensional topological structure. The method disclosed by the invention can be used for achieving the purposes of simplicity in operation and high precision.

An aircraft engine face radar cross section analysis is computed using a finite element based approach. A finite element model is only created for a periodic slice of the aircraft engine face. The system matrix of the finite element model is then transformed into a series of independent modes in a block diagonal matrix using a Discrete Fourier Transform. Each of the independent modes is then solved using an “infinite” pipe arrangement to remove the effects of rim scattering and the incident wave. The solved independent modes are summed together to determine the scattered electromagnetic field for the aircraft engine face. The scattered electromagnetic field is then used to calculate the radar cross section of the aircraft engine face.

The invention relates to a method for acquiring surface heat transfer coefficient of an end winding of a large-sized synchronous generator stator, belongs to the technical field of motors, aims to solve the problems that load of the existing large-sized synchronous generator is increasing so that heating of the end winding of the generator worsens increasingly while the surface heat transfer coefficient of the end winding is difficult to determine. The method includes: acquiring a two-dimensional fluid system simulation model, a three-dimensional end electromagnetic field calculation model and a three-dimensional end fluid and heat transfer coupling calculation model, solving by corresponding solvers to obtain boundary conditions and load of the three-dimensional end electromagnetic field calculation model and transmitting the conditions and load to a three-dimensional end fluid and heat transfer coupling solver; allowing the three-dimensional end fluid and heat transfer coupling solver to calculate to obtain the surface heat transfer coefficient of the stator end winding according to the boundary conditions and load of the three-dimensional end electromagnetic field calculation model and attributes of materials. The method is applicable to calculating the surface heat transfer coefficient of the end winding of the large-sized synchronous generator stator.

The invention provides an integrated circuit IBIS model extraction method and system based on an equivalent circuit model, and the method comprises the steps: obtaining multilayer integrated circuit layout information of a passive part of an integrated circuit, and setting extraction related parameters and simulation parameters; identifying a parallel plate field domain formed by a metal layer-medium of the passive part of the multi-layer integrated circuit, performing mesh generation, and calculating an electromagnetic field; defining a multiport network of the passive part, calculating scattering parameters of the multiport network of the passive part according to multiports of the passive part and the electromagnetic field of the multilayer integrated circuit, and converting the scattering parameters into an SPICE model of the passive part; if the model is the active model, combining the SPICE model of the active part and the passive SPICE model into a new SPICE model through coupling nodes; and converting the SPICE model into an IBIS model. The IBIS model extraction related parameters and simulation parameters of the IC packaging network can be set according to different requirements of users, and the method has the advantages of being high in IBIS model extraction integrity, high in extraction efficiency, high in simulation accuracy and the like.

The invention provides a one-dimensional vacuum Crank-Nicolson complete matching layer implementation algorithm based on bilinear transformation, and belongs to the technical field of numerical simulation. The method aims at stimulating limited memory space of a computer to be unlimited space. The one-dimensional vacuum Crank-Nicolson complete matching layer implementation algorithm is technological characterized in that plural stretched coordinate variables are converted from the frequency domain to the z domain through the bilinear transformation method, then the Crank-Nicolson time domain finite difference method is utilized for carrying out dispersion on the maxwell equation in the time domain, an explicit iteration equation of an electric field is deduced, and finally the value of the electromagnetic field component is obtained. The one-dimensional vacuum Crank-Nicolson complete matching layer implementation algorithm has the advantages of having unconditional stability, improving the electromagnetic field calculation speed and saving memory.

The invention provides an implementation algorithm for truncating a one dimensional Debye medium Crank-Nicolson perfectly matched layer, belongs to the technical field of numerical simulation, and aims to truncate a Debye dispersive medium by using the perfectly matched layer and simulate a limited memory space of a computer into an infinite space to simulate the propagation characteristic of electromagnetic wave in the Debye dispersive medium. The algorithm is characterized by comprising the following steps: a plurality of stretch coordinate variables are converted from a frequency domain to a z domain by using a bilinear transformation method, then a maxwell equation is dispersed in the time domain by using a Crank-Nicolson finite difference time domain method, an explicit iterative equation of an electric field is induced, and finally a value of an electromagnetic field component is solved. The algorithm has the advantages of unconditional stability and capabilities of improving the electromagnetic field calculation speed and saving memory.

A method for predicting the remaining service life of the T-shaped tail portion of a rotor of a pumped-storage power generation motor comprises the following steps that (1), an electromagnetic field calculation is carried out, wherein excitation source input, namely electromagnetic force, needed by structure field calculation, is obtained through the electromagnetic field calculation; (2) the structure field calculation is carried out; (3), a corrected S-N curve is drawn; (4) the fatigue life of the T-shaped tail portion of the rotor of the pumped-storage power generation motor is predicted through the corrected S-N curve obtained in the step (3) and calculation results of the step (1) and the step (2), and namely prediction of the remaining service life of the T-shaped tail portion of the rotor of the pumped-storage power generation motor is achieved. According to the method for predicting the remaining service life of the T-shaped tail portion of the rotor of the pumped-storage power generation motor, an accumulation effect, not considered in the field of electrical machinery, of multiple working conditions on fatigue failures and S-N curve correction both are used for evaluating the fatigue life of the T-shaped tail portion of the motor of the pumped-storage power generation motor, and accurate prediction of the fatigue life is achieved.

A far electromagnetic field estimation method includes assuming a measurement surface, setting a plurality of measurement points on the measurement surface, and measuring electromagnetic fields at the plurality of measurement points. The measurement surface in combination with a ground plane forms a closed surface surrounding a radiation source. A virtual observation point is outside a space formed inside the closed surface. Further, electromagnetic fields at a plurality of mirror image measurement points on a mirror image measurement surface having a plane-symmetrical relationship with the measurement surface are calculated on the basis of the electromagnetic fields at the plurality of measurement points. Then, a far electromagnetic field at the virtual observation point is estimated on the basis of the electromagnetic fields at the plurality of measurement points and at the plurality of mirror image measurement points.

The invention discloses a determination method for magnetic hysteresis characteristics and depletion characteristics of a transformer in a DC magnetic bias state. The determination method comprises the following steps: creating a lamination iron core model; dissecting the lamination iron core model to obtain finite elements; initializing the magnetic vector position and the electric current density of each node; under consideration of a hysteresis effect, combining the finite elements to obtain electromagnetic field result; combining a fixed point technology with a harmonic wave convergence technology to process the obtained magnetic reluctivity data of the magnetic density data; obtaining the data in one-one correspondence to the harmonic wave in sequence to form second harmonic wave data; if the second harmonic wave data do not converge, repeat such steps until the convergent second harmonic wave data is obtained. The determination method is broad in application rage, high in stability, and suitable for large-scale DC magnetic bias analysis, so as to provide important reference for power transformer production and manufacture.

The invention discloses a calculation method for an electric field under the crossing area of an alternating current-direct current power transmission line, and relates to the field of the high-voltage power transmission technology and electromagnetic field calculation. The calculation method comprises the following steps that: calculating the nominal electric field of each space joint at a certain moment, initializing space charge density, calculating a synthesis electric field, applying a method of characteristics to update space charge density distribution on an electric field line, calculating space charge density corresponding to different moments on the space node, and carrying out convergence judgment so as to obtain the electric field under the crossing area of the alternating current-direct current power transmission line. The calculation method disclosed by the invention has the characteristics of accurate calculation result and small calculation workload.

The invention relates to a wireless power transmission magnetic coupling system structure parameter optimization method based on SSP compensation. The method includes: establishing an electromagneticfield calculation model of the single-turn planar spiral coil; obtaining the coupling coefficient of the single-turn planar spiral coil model and the single-turn average inductance of the transmittingcoil and the receiving coil by taking the maximum coupling coefficient between the transmitting coil and the receiving coil as a target; establishing a multi-turn coil magnetic coupling system simulation model to obtain a coupling coefficient and single-turn average inductance of the transmitting coil and the receiving coil at the moment, and comparing the coupling coefficient and the single-turnaverage inductance with a result obtained by the single-turn planar spiral coil model until difference values are smaller than a preset value; and finally, according to the number of turns of the transmitting and receiving coils and the parallel compensation capacitance value, obtaining transformer leakage inductance model resistance and inductance and compensation network parameters of the magnetic coupling system, and configuring circuit parameters. The method enables the system to obtain the minimum winding loss on the premise of guaranteeing the same output index.

The invention relates to the technical field of a permanent magnet generator, in particular to a permanent magnet wind generator with multiple fields. Road coupling simulation method to establish theinner watershed-solid domain-outer watershed solving domain model, unstructured mesh partitioning; Applying material attributes according to the actual physical properties of each component; the initial constraint conditions of numerical simulation are collected, and the results are applied in the form of inlet conditions and rotating mechanical excitation. The initial boundary temperature and IHGinternal heat source are applied to compute and analyze the flow field and temperature field, and the flow is completed. The two-way exchange process of heat transfer, wall temperature and heat transfer coefficient on the solid contact surface realizes the generator flow. Thermal bi-directional coupling; The temperature distribution is applied to the electromagnetic field calculation, and the dynamic magnetic field variation is obtained by simulating the alternating magnetic field. The electromagnetic loss is returned to the heat source in the IHG. Numerical simulation results are obtained byrepeated iterations in the coupled flow field. The invention has the advantages of accurate and intuitive results, and can make up the limitation of the existing experimental means.

A transcranial magnetic stimulation (TMS) coil positioning device includes a stimulation coil (1), a coil position tracking module (2), a head fixing frame (3), a head position tracking module (4), athree-dimensional mobile seat (5), a camera (6), a coil rotating device (7), a control system (8), an image processing module (9), an electromagnetic field calculation module (10), and a display (11).The image processing module (9) reconstructs the three-dimensional head model of a patient in an image space. The electromagnetic field calculation module (10) obtains the optimal coil position and angle by inversion according to the position of a nerve fiber to be activated in a target treatment target area. The control system (8), by means of the camera (6), the coil position tracking module (2), the coil rotating device (7), the head position tracking module (4), the head fixing frame (3) and the three-dimensional mobile seat (5), adjusts the relative position and angle of the stimulationcoil (1) and a patient head (12) to a target position and a target angle.

An electromagnetic wave analyzer that accurately calculates electromagnetic waves emanating from a given wave source, without the need for assessing accuracy in other than the wave source domain. An analysis condition receiver receives analysis conditions including position parameters specifying observation points, as well as frequency parameters specifying frequencies to be analyzed. Upon receipt of analysis conditions, a Fourier transform processor transforms time-series electromagnetic current data to produce frequency-specific electromagnetic current data for each frequency specified by the frequency parameters. Based on the frequency-specific electromagnetic current data, an electromagnetic field calculator calculates the electric field at each observation point specified by the position parameters, by integrating electric fields produced by electric and magnetic currents in each small volume of the electromagnetic wave source.

The invention relates to a piecewise linear cyclic convolution-based one-dimensional left-handed material Crank-Nicolson perfectly matched layer realizing algorithm, belongs to the technical field of numerical simulation, and aims at shortening the left-handed material FDTD computational domain and simulating the finite memory spaces of computers into infinite spaces. The algorithm is technically characterized by comprising the following steps: in the process of transforming plural stretching coordinate variables from a frequency domain to a time domain, eliminating the second-order differential in the stretching variables by utilizing a piecewise linear cyclic convolution method so as to remarkably decrease the number of imported auxiliary variables and optimize the memory; dispersing a time domain Maxwell equation by utilizing a Crank-Nicolson time domain finite difference method so as to derive an explicit iterative equation of an electric field; and finally solving the value of an electromagnetic field component. The algorithm has the advantages of providing unconditional stability, improving the electromagnetic field calculation speed and saving the memory.

A sensor system for a sub-sea oil and gas well includes a casing, a transmit coil, a receive coil, and a processor. The casing defines an interior space through which a drilling pipe string transits. The transmit coil is coupled to the casing and is configured to conduct a current pulse and induce an electromagnetic field within the interior space. The electromagnetic field corresponds with the current pulse and interacts with the drilling pipe string. The receive coil is coupled to the casing and is configured to detect the electromagnetic field, including perturbations of the electromagnetic field due to the drilling pipe string's interaction therewith. The processor is coupled to the transmit coil and the receive coil. The processor is configured to compute a diameter of the drilling pipe string based on the current pulse and the electromagnetic field detected by the receive coil.

The invention relates to a two-dimensional dispersive medium Crank-Nicolson complete matching layer implementation algorithm based on a DG algorithm and belongs to the technical field of numerical simulation.The method aims at reducing a two-dimensional dispersive medium FDTD computational domain and simulating limited memory space of a computer into infinite space.The implementation algorithm is technically characterized in that in the process that a two-dimensional modified Maxwell equation with plural stretching coordinate variables is converted into the time domain finite difference from the frequency domain, an auxiliary differential equation method is utilized, and based on the Douglas-Gunn (DG) algorithm, an iteration equation with coefficients being block tridiagonal matrixes is approximately decomposed into two iteration equations with coefficients being tridiagonal matrixes, wherein the two iteration equations can be efficiently solved, and therefore computational efficiency is obviously improved.The implementation algorithm has the advantages of achieving unconditional stability, increasing the electromagnetic field computational speed and saving memory.

The invention discloses an electromagnetic force density transferring method used among special-shaped grids in magnetic field-structure field coupling calculation. The electromagnetic force density transferring method comprises the following steps: an electromagnetic field calculation finite element model is built; the shapes and the sizes of the grids are determined according to the magnetic field distribution characters of research objects; magnetic field numerical calculation on the research objects is preformed to obtain the current density J and the magnetic induction intensity B of each unit respectively; a geometric model of the research objects in the structural field calculation is re-built again; the model is discretized into finite element girds, wherein the shapes and the sizes of the finite element grids are different from those of an electromagnetic field; the coordinates Mi (xi i, eta i, zeta i) of the gravity center of each unit of the finite element model in a structure field are read; corresponding points Mi' (xi, yi, zi) of the gravity center of each unit in the structure field are found according to the coordinate values; the J and B of the Mi' (xi, yi, zi) are obtained by interpolating; electromagnetic force density f at each point is obtained based on a formula that f is equal to J*B; the f value of each gravity center point is read to be used as load to be applied to each unit in the structure field for calculation to obtain a stress distribution result. The data transmission among the grids of different types can be realized in the magnetic field and the structure field; the calculation time is shortened and the calculation precision is improved.

The invention discloses an electromagnetic field prediction method of a three-dimensional FEM mixed with a two-dimensional FMM. The electromagnetic field calculation method of the three-dimensional FEM mixed with the two-dimensional FMM is innovatively provided for the first time; the method comprises the steps of FEM calculation, two-dimensional FMM analysis, scattered field superposition and thelike. the indoor electromagnetic field distribution of the urban housing under the radiation condition of each related electromagnetic radiation source is simulated; according to the method, the capacity of the FEM for processing complex materials and structural targets and the capacity of the two-dimensional FMM for processing super-electric large targets or environments are fully combined, andan efficient and feasible means is provided for achieving civil hot spot problems such as indoor and outdoor electromagnetic field distribution prediction of high-rise buildings. Compared with a traditional high-frequency method for electromagnetic field prediction, the technology is higher in calculation precision and efficiency, and the scale of solvable problems is larger; and two-dimensional modeling is adopted for the high-rise buildings, so that the complexity that three-dimensional modeling needs to be adopted in a traditional method is solved, and rapid two-dimensional generation of urban high-rise building groups can be automatically realized.

The invention relates to a one-dimension left-handed material Crank-Nicolson perfectly matched layer realizing algorithm based on an auxiliary differential equation, and belongs to the technical field of numerical simulation. The method aims at reducing the left-handed material FDTD (Finite-Different Time-Domain) computational domain, and simulating a computer finite memory space into an infinite space. The one-dimension left-handed material Crank-Nicolson perfectly matched layer realizing algorithm has the technical characteristics that in a process of converting a plurality of stretched coordinate variables from the frequency domain to the time domain, the second-order differential in the stretched variables is eliminated by an improved auxiliary differential equation method, so that the number of the introduced auxiliary variables is obviously lowered, and a memory is optimized; then, a time domain Maxwell equation is subjected to discretization by a Crank-Nicolson time domain finite differential method; an explicit iteration equation of an electric field is deduced out; and finally, a value of an electromagnetic field component is obtained. The one-dimension left-handed material Crank-Nicolson perfectly matched layer realizing algorithm has the advantages that the unconditional stability is realized; the electromagnetic calculation is accelerated; and the memory is saved.

The invention relates to a CAE-based simulation optimization method of a motor for a power automobile. The method comprises the following steps: providing a virtual motor; carrying out static electromagnetic field analysis on the virtual motor, and calculating static electromagnetic parameters of the virtual motor according to a static electromagnetic field calculation model; performing transientelectromagnetic field analysis on the virtual motor, and calculating transient electromagnetic parameters of the virtual motor according to a transient electromagnetic field calculation model; judgingwhether the static electromagnetic parameters and the transient electromagnetic parameters of the virtual motor are in an electromagnetic parameter threshold range or not; if yes, vibration noise analysis is conducted on the virtual motor, vibration noise is calculated according to a vibration noise calculation model, whether the vibration noise is within the vibration noise threshold range or not is judged, and if yes, motor initial parameters are stored to serve as motor design parameters to design the motor. The method disclosed by the invention not only meets the conditions of common motors, but also meets the condition of low vibration noise, and adopts the modes of parameter linkage, scanning characteristics and the like, thereby greatly shortening the development period and savingmanpower and material resources.

The invention relates to a two-dimensional vacuum Crank-Nicolson complete matching layer implementation algorithm based on an auxiliary differential equation and belongs to the technical field of numerical simulation.The method aims at reducing a vacuum FDTD computational domain and simulating limited memory space of a computer into infinite space.The implementation algorithm is technically characterized in that in the process that a two-dimensional modified Maxwell equation with plural stretching coordinate variables is converted into the time domain finite difference from the frequency domain, a Douglas-Gunn (DG) algorithm is utilized, an iteration equation with coefficients being block tridiagonal matrixes is approximately decomposed into two iteration equations with coefficients being tridiagonal matrixes, wherein the two iteration equations can be efficiently solved, and computational efficiency is obviously improved.The implementation algorithm has the advantages of achieving unconditional stability, increasing the electromagnetic field computational speed and saving memory.

The invention provides an impulse function expression for describing lightning return stroke channel base current. An impulse function, which can be regarded as the modification of a double exponential function, can fully reflect standard-specified lightning current waveform characteristics and also overcomes the adverse factors of the base current models of the double exponential function and a Heidler function in lightning return stroke electromagnetic field calculation, not only is a first-order derivative continuous when t is equal to 0, but also the impulse function has an explicit time integral expression, and thereby a lightning return stroke electromagnetic field can be conveniently analytically calculated. In addition, in order to accurately obtain parameters which are used by the impulse function to represent the standard waveform of lightning current, a waveform nonlinear curve fitting method can be adopted.

The invention provides a three-dimensional analytical calculation method for electromagnetic torque of a permanent magnet eddy current coupling. The three-dimensional analytical calculation method includes the steps: based on a sub-domain method electromagnetic field calculation model, firstly, enabling a permanent magnet eddy current coupling to be equivalent to four sub-domains of a permanent magnet array, an air gap, a conductor and a conductor back iron under a rectangular coordinate system; then calculating specific forms of coefficients related to the harmonic order in the magnetic vector potential expressions of the conductor and the conductor back iron field domain; and finally, obtaining an electromagnetic torque value under the given air gap and slip ratio. According to the three-dimensional analytical calculation method, the three-dimensional eddy current paths in the conductor and the conductor back iron are effectively simulated, and the established three-dimensional electromagnetic field calculation model is close to the actual situation, and the electromagnetic torque of permanent magnet eddy current couplers of various topological structures under the working conditions of different slip speeds, air gaps and the like can be accurately and rapidly predicted.

There is provided a method of predicting the response of an induction logging tool along an arbitrary trajectory in a three-dimensional earth model, wherein the method comprises a confinement of the electromagnetic field computations to a limited domain of the geology surrounding the induction logging tool. The magnetic field at a receiver coil is considered as a superposition of a primary background constituent and a secondary constituent. A single spherical scatterer approximation is used for the second constituent.

The invention proposes a time domain finite-difference method implemented by using a digital signal processing technique, which is used for the field of design and application of electromagnetic field software. A Courant-Friendrich-Levy time stability condition can be broken through by using the time domain finite-difference method with a hidden alternative direction; in order to simplify the whole electromagnetic calculation process, matrixes and vectors in a hidden time domain finite-difference equation are arranged according to the requirement of digital signal processing, and a discrete difference equation is pre-processed; and for a parallel technology, the time domain finite-difference method with the hidden alternative direction is completed by combining the digital signal processing technique according to a time discrete signal flow chart so as to calculate an electromagnetic field numerical value. With the method proposed by the invention, the electromagnetic field calculation efficiency can be improved; compared with a traditional time domain finite-difference method, the method has the advantages that a Courant-Friendrich-Levy (CFL) factor is appropriately selected, and the calculation efficiency can be improved by 3 to 5 times; and moreover, the method proposed by the invention can be effectively combined with a telescopic coordinate completely-matching layer, unbounded transmission of simulated electromagnetic wave can be achieved, and the method can be more widely applied.