1225 results about "Vertical coordinate" patented technology

The invention discloses a dynamic automatic drive lane-changing trajectory planning method based on real-time environment information. A rollover limitation trajectory vertical coordinate, an optimal trajectory and a collision avoidance trajectory terminus security area are calculated; the relation between the rollover limitation trajectory vertical coordinate and the security area is compared, the positional relation between the optimal trajectory vertical coordinate and the security area is further compared, and then lane-changing decision-making is conducted. According to the dynamic automatic drive lane-changing trajectory planning method based on the real-time environment information, and a polynomial trajectory equation which dose not depend on time is adopted to represent a lane-changing trajectory curve, so that the problem that hypotheses of a speed and an accelerated speed are too strong is avoided; furthermore, collision avoidance algorithm and rollover prevention algorithm which are based on reaction time are introduced to guarantee security of lane-changing; then the optimal trajectory in a safe trajectory cluster is determined through real-time speed adjusting; and finally, an optimal lane-changing trajectory of real-time dynamic state is output through a trajectory generation module to guide an autonomous vehicle to complete a lane-changing behavior, and therefore a set of complete dynamic autonomous vehicle lane-changing trajectory planning module is built.

An excavator 3D integrated laser and radio positioning guidance system (Ex_3D_ILRPGS) comprising: a mobile radio positioning system receiver configured to obtain 2D horizontal coordinates of the excavator, a bucket-to-machine-body positioning system configured to obtain coordinates of the boom, the stick and the bucket of the excavator, a laser detector configured to receive at least one laser beam and configured to provide a local vertical coordinate with a substantially high accuracy, and an on-board navigational system configured to receive and to integrate the 2D horizontal coordinates of the excavator obtained by the mobile radio positioning system receiver, the coordinates of the boom, the stick and the bucket of the excavator obtained by the bucket-to-machine-body positioning system, and the local vertical coordinate obtained by the laser detector, and configured to guide the cutting edge of the bucket of the excavator with substantially high vertical accuracy.

The invention discloses an obstacle detecting method and an obstacle detecting device used for a vehicle-mounted radar system. The obstacle detecting method is implemented by the specific steps of: detecting a first point cloud data set of calibration objects arranged at a plurality of preset positions, and detecting a first two-dimensional data set of the calibration objects; calibrating the vehicle-mounted radar system based on a preset installation position, the first point cloud data set and the first two-dimensional data set, so as to obtain a calibrated steering angle difference, a calibrated displacement difference and a calibrated vertical coordinate; detecting second point cloud data of an obstacle, and detecting second two-dimensional data of the obstacle; converting the second two-dimensional data into a laser radar coordination system based on the calibrated steering angle difference, the calibrated displacement difference and the calibrated vertical coordinate, so as to obtain converted third-dimensional coordinates; and merging the second point cloud data and the converted third-dimensional coordinates, so as to determine a position of the obstacle. Through the implementation of the obstacle detecting method and the obstacle detecting device, the obstacle can be precisely detected by effectively utilizing a laser radar and a millimeter-wave radar simultaneously.

The invention discloses a method and a system for implementing original handwriting. The method for implementing the original handwriting includes acquiring track coordinates of the handwriting in real time; computing the movement speed of the original handwriting according to horizontal coordinate position parameters and vertical coordinate position parameters which are acquired in real time; determining the widths of drawn tracks according to a preset pen type and acquired pressure parameters, using corresponding drawing points as starting points, filling track patterns with the corresponding widths in cross directions of forward directions of the tracks, dynamically adjusting the quantities of grids at the edges of the patterns according to the computed movement speed when the edges of the track patterns are drawn, and performing anti-aliasing processing on the edges of the track patterns according to the quantities of the grids at the edges of the track patterns. According to the technical scheme, the method and the system have the advantages that the quantities of the grids which are used for smoothly changing the edges of the track patterns are dynamically adjusted according to a handwriting movement speed characteristic of the original handwriting, so that the smoothness, the accuracy and the fluency of the track patterns are effectively balanced, and the user experience is improved.

An improved method of estimating an earth model utilizes an acoustic Full Waveform Inversion (FWI) of seismic data in a pseudo-time coordinate system, in which the earth model m({tilde over (m)}) is parameterized with two lateral coordinates (x,y) and a vertical coordinate ({tilde over (z)}) which expresses vertical travel time of acoustic signals used to generate the seismic data.

The invention discloses an optic disc projection location method synthesizing vascular distribution with video disc appearance characteristics, which comprises the following steps of: (1) extracting an interest retina fundus image region by use of a mask operation; (2) carrying out normalization enhancement on a fundus image based on an image observation model; (3) achieving extraction and segmentation of the fundus image by using a non-vascular structure inhibition operator and combining with a hysteresis multi-threshold processing technology; (4) setting a vertical window of double main blood vessel width to slide on a blood vessel segmentation image along the horizontal direction and calculating a vascular distribution degree D(x) at each horizontal position x to obtain a distribution degree curve of a horizontal projection, wherein the minimum value point of the curve is determined to be optic disc horizontal coordinate xod; (5) setting a rectangular window side length of which is equal to the optic disc diameter to slide up and down at the horizontal coordinate xod, estimating local region brightness IN(xod, y) and edge gradient information gN(xod, y) respectively, drawing a vertical projection curve reflecting a change of a characteristic value f(y)=IN(xod, y)*gN(xod, y), wherein a maximum value point of the curve is optic disc vertical coordinate yod. The method has a simple algorithm, a high success rate and excellent robustness.

The invention discloses a method for measuring the phase center of an antenna, which is based on moving reference points. The method provided by the invention mainly solves the measuring problems of manual operation and artificial judgment. The method includes the following steps: in the measuring system, a measured antenna is adjusted to face an original antenna and is taken as the zero point of a measuring angle; the horizontal direction and the vertical direction of a two-dimensional translation device are controlled to reset and taken as the datum reference point of the phase center test; related parameter information is input and all moving shafts are controlled automatically, thereby collecting the amplitude and phase data of the measured antenna; the horizontal deviation and the longitudinal deviation of the phase center can be worked out by using the least square method and then can be determined whether the deviation of the phase center meets the deviation requirements of the designed phase center of the antenna; if not, the reference point of the antenna can be changed by automatically adjusting the horizontal coordinate and the vertical coordinate of the two-dimensional translation device according to the deviation value; the test can be repeated again and again until the horizontal deviation and the longitudinal deviation meet the requirements; and the final changed reference point can be taken as the phase center of the measured antenna. The method provided by the invention can automatically and accurately measure the phase center of an antenna.

A vehicle detection apparatus detects vehicles traveling on a road with their lights turned on. The apparatus captures images of a road, detects a light spot from captured images, and detects a first vertical coordinate of the light spot in the images. The apparatus further calculates a distance to the light spot based on a horizontal length of the light spot in the images and detects a second vertical coordinate corresponding to the calculated distance, based on correlated data in which vertical coordinates and distances in an image are correlated in advance. The apparatus further calculates a pitching amount that indicates a difference between the first and second coordinates and determines whether or not the light spot originates from a vehicle, based on the pitching amount.

The invention provides a hypersonic velocity static wind tunnel nozzle design method and a hypersonic velocity static wind tunnel nozzle transition position determining method. The hypersonic velocity static wind tunnel nozzle transition position determining method comprises the steps that a Gulet logarithm N is determined according to the design requirements of a hypersonic velocity static wind tunnel nozzle; an axle wire of the hypersonic velocity static wind tunnel nozzle serves as an X axis, and the first formula shown in the specification is utilized for determining the vertical coordinate yT of a transition point, wherein the vertical coordinate yT of a transition point conforms to a second formula shown in the specification. According to the second formula, T is the transition point, the GT is the Gulet number of the point T, deltaT is the boundary layer thickness of the point T, RdeltaT is the boundary layer thickness Reynolds number of the point T, rT is the wall curvature radius of the transition point T, y'T is the first-order derivative of the y-axis coordinate of the transition point T, and y''T is the second-order derivative of the y-axis coordinate of the transition point T; according to the vertical coordinate yT of the transition point T, the horizontal coordinate xT of the transition point T is determined. According to the hypersonic velocity static wind tunnel nozzle design method and the hypersonic velocity static wind tunnel nozzle transition position determining method, the transition position of the hypersonic velocity static wind tunnel nozzle can be easily and accurately obtained, and the repeated debugging step in the design process of the hypersonic velocity static wind tunnel nozzle is omitted.

The invention discloses a method for identifying modal parameters of a transformer coil. The method includes the following steps: vibration signals of all measure points of the transformer coil are collected; Fourier transformation is carried out on the vibration signals, and a vibration frequency response curve of the transformer coil is obtained; Fourier inversion is carried out, and free vibration signals of the transformer coil are obtained; wavelet conversion is carried out on the free vibration signals through Morlet wavelets, and a wavelet transformation time-frequency diagram is made; wavelet ridges are extracted from the wavelet transformation time-frequency diagram, and the vertical coordinate of each wavelet ridge is inherent frequency of each step of the transformer coil; the damping ratio of inherent frequency of all the steps is calculated; a coil vibration mode of the inherent frequency of each step is calculated. With the method, the mode parameters of the transformer coil can be accurately and efficiently identified. Design, manufacturing, coil deformation detection and state evaluation are convenient to carry out on a coil structure.

The invention relates to a spectral standardization-based coal quality on-line detection method, which can be used for coal quality on-line detection based on a laser induced plasma spectra principle. In the method, a calibrating model is established by using the intensity of an atomic characteristic spectral line after spectral standardization as a vertical coordinate and using the concentration of an element corresponding to the atomic characteristic spectral line as a horizontal coordinate. When the coal with unknown components is detected, the concentration of an element to be tested can be obtained according to the calibrating model after the spectral standardization. In the method, plasma temperature, electronic density, density ratio of ion to atom of the same element and a boltzmann's law are taken into consideration, so that the fluctuation of experiment parameters is compensated and the measuring precision is improved. The method can also be applied to the similar occasions requiring on-line real-time detection of chemical components.

The invention discloses a self-adaptive radar calibrating device for a sedan, which includes a base plate, wherein an upright column is vertically arranged on the base plate; a slideway is arranged on the upright column; a cross beam is connected with the slideway in a sliding way; the cross beam is connected with a driving mechanism; a vertical coordinate plate with a level is connected with the cross beam; and a laser hole is arranged in the coordinate plate. The self-adaptive radar calibrating device has a simple integral structure, is flexible and reliable to act, is convenient to operate, can correctly calibrate the radar in the ACC self-adaptive cruise control system.

The invention discloses a multiple digital watermarking method for geographic information system (GIS) vector data, and belongs to the field of geographic information copyright protection. The watermark embedding process of the method comprises the following steps of: reading and processing the data; embedding algorithms by an odd-even method; respectively embedding watermarks into a spatial domain, a discrete wavelet transform domain, a discrete cosine transform domain of horizontal coordinates and vertical coordinates by a low-order additive method and a least significant bit substitution method; adopting a zero-watermark algorithm; and storing watermark-containing data. The watermark extraction process of the method is the inverse process of the embedding process. A practical multiple digital watermark protection method is comprehensively integrated aiming at the common attack modes of the GIS vector data and according to the principle and anti-attack performance of each single algorithm. Various embedding modes are adopted and the specific embedding position of each watermark is controlled, so that embedding and extraction are non-interfering, conflicts are avoided, the advantages of each algorithm are exerted and complemented and the anti-attack capability of digital watermarks is greatly improved.

The invention discloses a calibration method of an on-board camera. The calibration method comprises the following steps of equipment installing, calibration site laying and image calibrating. The calibration method of the on-board camera is based on vanishing point detection. During distance measurement, coordinate transformation is conducted on the basis of a vertical coordinate YL of a vanishing point, it is avoided that re-calibration is conducted when the installation height and the pitch angle of a camera change, and operation is simple and convenient. In addition, a data calculation model is simplified, and reaction speed of an on-board computer is increased. The calibration method is unrelated to the pitch angle of an automobile, the corresponding relationship between a space coordinate and an image coordinate is rapidly calculated according to the vertical coordinate YL of the vanishing point on the road surface, distance measurement speed is high, and accuracy is high. The calibration method achieves automatic regulation of calibration data of the camera, and therefore resolves the problem that the measurement accuracy is insufficient when the camera is installed again or the pitch angle changes in a running process of the automobile.

The invention discloses a method for obtaining an underground three-dimensional density structure, relates to the field of geophysical prospection, and solves the technical problem that the underground three-dimensional density structure cannot be accurately obtained in the prior art. The method is characterized by comprising the following steps: determining the vertical coordinates, horizontal coordinates, depth, and 2D (two-dimensional) profile interval of a modeling area; carrying out gravity inversion modeling by adopting a Naive Bayesian classification method according to prior information and the modeling area, so as to obtain an initial geological model; constructing the initial geological model into a 2D geological model by adopting a discrete body simulation method; splicing and fitting the 2D geological model into a 3D geological model; performing visualization and structure interpretation treatment on the 3D geological model, so as to obtain the underground three-dimensional density structure . The method is mainly based on the Bayesian classification inversion principle, and is combined with the discrete body simulation technology, so as to realize accurate establishment of a weight density mode, and improve the accuracy of the obtained underground three-dimensional density structure.

Deriving inertial-aided deviations for autoland systems during GPS signal interruptions involving an inertial reference system and a GPS landing system can include converting position coordinates of an aircraft from the inertial reference system to runway, lateral, and vertical coordinates. After this conversion, the method calibrates runway distance and lateral distance based on the converted position coordinates from the inertial reference system using runway distance and lateral distance from the GPS landing system with a third-order calibration filter when the aircraft is below a first height above terrain and calibrates vertical distance based on the converted position coordinates from the inertial reference system using vertical distance from the GPS landing system with a second-order calibration filter when the aircraft is below the first height above terrain. The method uses the calibrated runway, lateral, and vertical distances for deviation computations when GPS signals are interrupted below a second height above terrain.

A combined radio and laser positioning system comprising: a network of ground based radio communication devices, a laser transmitter configured to generate at least one laser beam, and at least one user unit. Each user unit comprises a radio receiver configured to receive at least one ranging radio signal transmitted by at least one ground based radio communication device, a laser detector configured to receive at least one laser beam generated by the laser transmitter, and a processor configured to convert a set of data including: {a set of data transmitted by at least one ranging radio signal, and a set of data transmitted by said at least one laser beam} into position coordinates of the user unit, wherein a set of vertical coordinates of the user unit is obtained with a laser-assisted (LA) accuracy.

A conductive layer of a touch sensor and a pixel electrode conductive layer of a display panel are integrated to a touch display panel during the same fabrication. The touch sensor defines a plurality of sensor groups that are insulated from each other in a same conductive layer, and each of the sense groups is divided into a plurality of mutually-coupled first electrodes, a plurality of mutually-coupled second electrodes and a plurality of mutually-coupled third electrodes. The first electrodes and the third electrodes are insulated from each other and are horizontally interlaced. The first electrodes and the second electrodes are insulated from each other and are located on opposite sides of a horizontal symmetry axis. A gain for compensating a vertical coordinate of a touch position is introduced according to capacitance variances of the first electrodes and the second electrodes.

A vehicle guidance system for guiding motor vehicles comprising a central traffic control system, a plurality of roadside equipment, and an on-board vehicle guidance and control system. The central traffic control system includes horizontal memory for storing horizontal coordinates and direction information of a locality, vertical memory for storing vertical coordinates and direction information of the locality, transmitter means for transmitting the horizontal and vertical information of the locality, and a system control unit for controlling the continuous transmission of the horizontal and vertical information of the locality. The roadside equipment includes coordinates memory for storing the coordinates information of the roadside equipment, coordinates transmitter means for transmitting the coordinates information of the roadside equipment to the vehicle, receiver means for receiving destination information from the vehicle, and vehicle destination means for transmitting the coordinates information of the roadside equipment and the destination information of the vehicle to the central traffic control system. The on-board vehicle guidance and control system includes receiver means for receiving the horizontal and vertical coordinates information of the locality traffic control system, vertical coordinates memory for storing the vertical coordinates information of the locality, horizontal coordinates memory for storing the horizontal coordinates information of the locality, an on-board system control unit for controlling the reception and storage of the horizontal and vertical coordinates information of the locality, display feed memory for storing route direction information for reaching the destination of the vehicle, and display means for displaying the route direction information.

The invention provides a method for determining lost gas content in gas content of shale. The method comprises steps as follows: core samples are acquired from a shale gas underground site, lifted to the ground and placed into an analyzer, multiple parameters are acquired, the zero time, the lost time correction and the core sample weight are calculated before desorption of the core samples, the core samples are desorbed in the analyzer, data acquired during desorption are processed, the square root of acquired desorption time is used as a horizontal ordinate, the acquired desorbed gas content is used as a vertical coordinate, a fitted curve of the desorbed gas content is drawn, and the intercept value of the vertical coordinate of the fitted curve is the lost gas content.

The invention discloses a method for monitoring and predicting galloping of a transmission line in real time based on video analysis, which comprises the following steps of collecting an original image; carrying out image processing on the original image at a monitoring terminal, identifying characteristic target points, which are obtained after processing the original image, on the transmission line automatically, and acquiring position coordinates of the target points; analyzing the pre-processed image, acquiring position coordinates of the target points of the transmission line, and calculating the icing thickness of the line; calculating the number of continuous images between adjacent maximum values or minimal values according to vertical coordinates of the target points of continuous image files, and calculating the galloping frequency of the line according to the time interval of two adjacent images; and carrying out simulating and predicating analysis on the galloping condition of the transmission line in future. The method disclosed by the invention analyzes the galloping condition of the transmission line by using video image technologies, thereby avoiding installation of a large amount of hardware sensors on the transmission line, saving the expenditure of hardware, reducing extra hardware maintenance workload, and being convenient to manage.

An excavator 3D integrated laser and radio positioning guidance system (Ex_3D_ILRPGS) comprising: a mobile radio positioning system receiver configured to obtain 2D horizontal coordinates of the excavator, a bucket-to-machine-body positioning system configured to obtain coordinates of the boom, the stick and the bucket of the excavator, a laser detector configured to receive at least one laser beam and configured to provide a local vertical coordinate with a substantially high accuracy, and an on-board navigational system configured to receive and to integrate the 2D horizontal coordinates ofthe excavator obtained by the mobile radio positioning system receiver, the coordinates of the boom, the stick and the bucket of the excavator obtained by the bucket-to-machine-body positioning system, and the local vertical coordinate obtained by the laser detector, and configured to guide the cutting edge of the bucket of the excavator with substantially high vertical accuracy.

The invention discloses a coupling calculation method of deepwater gas-liquid two-phase flow circulating temperature and pressure. The coupling calculation method comprises the following steps: (1) calculating the vertical coordinate of a grid; (2) applying the initial condition; and (3) from the beginning of an original value, carrying out iterative calculation on node temperature and pressure data of drill string drilling fluid and annulus drilling fluid in sequence, until the temperature and the pressure reach the condition of convergence, finishing the iteration, and saving and outputting the last-time iterative calculation result as the final deep sea gas-liquid two-phase flow shaft temperature and pressure simulation result, wherein the iteration is named as a global iteration. The coupling calculation method improves the calculation precision.

A memory of a photographing field angle calculation apparatus has stored therein the position of each point captured by an imaging system as three coordinate values in horizontal, vertical, and depth directions when a photography space is photographed by the imaging system. A usage pixel value extraction means selects a plurality of points located in end portions in the horizontal direction of a range captured by the imaging system from those stored in the memory based on the vertical coordinate value, and extracts the horizontal and depth coordinate values of each of the selected points. A field angle calculation means calculates a horizontal photographing field angle when the photography space is photographed using the extracted horizontal and depth coordinate values.

When a horizontal-coordinate value or a vertical-coordinate value of a current touch point with reference to a point of origin defined at a touch-start point at which a drag operation on a touch screen starts is less than a threshold value, an X-direction movement amount reset unit or a Y-direction movement amount reset unit resets an amount of horizontal movement or an amount of vertical movement in the drag operation to zero. A scroll control unit scrolls the screen in accordance with the amount of horizontal movement and the amount of vertical movement as processed by the X-direction movement amount reset unit and the Y-direction movement amount reset unit.

The invention discloses a vision sensing-based laser-electric arc hybrid welding real-time automatic control device and a welding method thereof. A welding gun is connected with a laser head. The fused welding wire tip of a welding wire forms a molten drop in the welding process. A laser beam is irradiated to weldment, and a laser keyhole is formed. A high-speed camera is used for filming images of the fused welding wire tip and the laser keyhole. The high-speed camera is connected with an image processing industrial personal computer. The image processing industrial personal computer is connected with a combined welding head control device of the welding gun and a welding equipment control device of the welding gun. The image processing industrial personal computer controls the distance between the central point of the laser keyhole and the central point of the molten drop through the combined welding head control device of the welding gun and controls the vertical coordinate Y value of the central point of the fused welding wire tip through the welding equipment control device of the welding gun. By the adoption of the vision sensing-based laser-electric arc hybrid welding real-time automatic control device and the welding method thereof, the problems that in the prior art, the distance between the center of a molten drop and the center of a laser keyhole cannot be adjusted in real time, visualization of the adjusting process cannot be achieved, and accordingly the distance between the center of the molten drop and the center of the laser keyhole is too large or too small are solved.

The invention provides a Gamma correction system and a correction method thereof. The method includes the steps of selecting n gray scale values, calculating n first brightness values corresponding tothe n gray-scale values for each sub-pixel, forming n fitting points by taking the n gray scale values as the horizontal coordinates and the corresponding n first brightness values as the vertical coordinates, fitting the n fitting points to obtain a fitting curve of each sub-pixel, and finally, taking a fitting curve of which the total deviation of the n second brightness values and the n firstbrightness values corresponding to the sub-pixels is smaller than a threshold value as a fitting curve of the sub-pixel and storing the fitting curve into a memory. The brightness corresponding to thegiven gray scale value of each sub-pixel can be obtained according to the fitting curve. The gray scale value does not need to be stored, hardware resources are saved, and only n fitting points needto be fitted in the whole correcting process. The correcting time is greatly shortened.

The invention relates to a triaxial test method for shear strength property of a weak layer, a test device adopts a triaxial shear instrument, and test purposes are realized through the specific test sample preparation method: (1) test sample preparation-1: cutting a soil column on an undisturbed soil sample containing the weak layer along an included angle of 45 degrees in the vertical direction; (2) test sample preparation-2: cutting the soil column into the stipulated diameter; (3) taking out of a test sample: leveling two ends by cutting according to the stipulated height and weighing; and taking remaining oil for determining water content; (4) test sample saturation; (5) testing; and (6) data analysis: taking normal stress sigma as horizontal coordinate, and taking shear stress tau as vertical coordinate; taking an inclination angle of a connected straight line of positive stress sigma n and failure shear stress tau n () obtained under different ambient pressure conditions as an internal friction angle phi, and taking intercept on a longitudinal axial on the straight line as cohesive strength C; and obtaining the test result. By adopting the special soil sample preparation method and the analysis method, the uniformity of the shear stress and strain on the weak layer can be ensured and the main problems during testing of a direct shear apparatus can be effectively solved.

The invention relates to a three-dimensional fault line selection method based on random resonance and a transient current signal. The method comprises the following steps of: (1) after a power distribution network is faulted, recording the zero-sequence current iZn(t) and the fault phase current iXn(t) of each branch line fault, and computing transient zero-sequence current izn(t) and transient fault phase current ixn(t); (2) performing variable-scale bistable treatment on the transient zero-sequence current izn(t) and transient fault phase current ixn(t); (3) computing a cross correlation coefficient matrix M and an integrated correlation coefficient Mn among the transient characteristic zero-sequence current iczn(t) of the branch lines and selecting the line ln with the minimum Mn; (4) performing seven-layer db10 wavelet packet decomposition on the transient characteristic phase current icxn(t) of each branch line and computing simplified energy E*sn and simplified gravity center frequency f*gn; and (5) forming a three-dimensional coordinate system by using the simplified gravity center frequency f*gn as a horizontal ordinate, the simplified energy E*sn as a vertical coordinate, and a polarity parameter value as a longitudinal coordinate. Compared with a method in the prior art, the method is high in reliability and is not liable to suffer from external interference.

The invention provides a device and a method for testing a forming limit of a sheet material in a three-dimensional stress state, relating to the device and the method which are used for testing the forming limit of the sheet material. Aiming to the problems that the forming limit of the sheet material in the three-dimensional stress state is difficult to test and an influence of normal pressure to the forming limit is difficult to estimate, the device comprises an upper die and a lower die. In a test, a fluid medium is injected into the lower die, a test sample of the sheet material is placed, mold clamping force is applied, the fluid medium is injected into the upper die, and pressurized deformation is carried out by controlling pressure in the upper die and the lower die in sequence. Braking strains of the test sample of the metal sheet material can be calculated according to measured data before and after circular or square mesh deformation, namely epsilon 1=Ln[d1-d / d] and epsilon 2=Ln[d-d2 / d]; a plurality of groups of different limit strain data points can be obtained by changing a ratio of a long shaft to a short shaft of an oval cross section of a cavity; and the obtained data points can be connected or fitted by respectively using the epsilon 1 and the epsilon 2 as a transverse coordinate and a vertical coordinate, so as to obtain the sheet material forming limit curve at the three-dimensional stress state at a certain normal pressure condition to estimate the influence of the normal strain to the forming limit in the three-dimensional stress state.