CN107577843B - Method for evaluating characteristic coupling relation of collision waveform and constraint system - Google Patents
Method for evaluating characteristic coupling relation of collision waveform and constraint system Download PDFInfo
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Abstract
The invention discloses a method for evaluating the characteristic coupling relation of a collision waveform and a restraint system, which solves the problems of huge calculation amount and time consumption when a CAE simulation technology is used for researching the characteristic coupling relation of a vehicle body structure and a passenger restraint system, and comprises the following steps: 1. establishing an occupant response surface based on a single-degree-of-freedom model: 1) defining shape characteristic parameters of a double trapezoidal wave and a trilinear constraint stiffness curve, 2) solving an occupant response surface by using a single-degree-of-freedom model; 3) respectively averaging XY directions of the response surfaces; 2. analyzing the correlation between the occupant response and the collision waveform parameters: 1) collision waveform parameter definition supplement; 2) extracting collision waveform basic parameters and A from occupant response surfacevPerforming linear regression analysis on the corresponding relation; 3. evaluation of the coupling relation of the collision waveform and the characteristic of the restraint system: 1) establishing a comprehensive evaluation index alpha of a collision waveform; 2) establishing a comprehensive evaluation index beta of a constraint system; 3) a of comprehensive evaluation indexes of collision waveform and constraint system characteristicsoAnd (4) establishing.
Description
Technical Field
The invention relates to an evaluation method for the coupling effect of an automobile body structure and a restraint system, in particular to an evaluation method for the coupling relation between a collision waveform and the characteristics of the restraint system.
Background
Vehicle safety is determined by both the crashworthiness of the vehicle body structure and the occupant restraint system. At present, the whole vehicle safety development process is mainly to carry out constraint system matching after the anti-collision design of a whole vehicle structure. With the intensive research in these two fields, enterprises continue to develop crashworthiness structure and restraint system devices from various aspects. The design of the collision resistance of the vehicle body is in the early stage of a safety development process, and a direct relation with the injury of passengers cannot be established, so that the design basis is mainly the characteristics of large energy absorption, good front end structural rigidity and the like. Restraint system designs are in the later stages of safety development, and sometimes the phenomenon that passenger injury always stays high no matter how the restraint system parameters are matched occurs. The main reason for this phenomenon is that the lack of consideration of the characteristic coupling relationship between the vehicle body structure and the occupant restraint system in the conceptual design stage results in a disconnection between the design of the crashworthiness of the vehicle body and the design of the restraint system. If the design requirements of the crashworthiness of the vehicle body structure and the design requirements of the passenger restraint system are provided from the perspective of the coupling relation in the initial stage of safety design, the matching effect can be controlled integrally from the macroscopic view.
Since the characteristic coupling relation influence parameters of the vehicle body structure and the passenger restraint system are numerous and all the parameters interfere with each other, if all the parameter levels are put into the simulation model, the calculation amount is huge, and therefore, the study of the coupling relation through a simulation method is not facilitated. The scholars at home and abroad develop the study of the coupling relationship from the collision mechanics theory level to obtain a series of important conclusions, but no clear evaluation index exists. The method further strengthens the relation between theoretical research of the coupling relationship and engineering practice, and is of great significance for guiding the design of the crashworthiness of the vehicle body structure and the matching design of a constraint system.
Disclosure of Invention
The invention aims to solve the technical problems that the calculation amount is large and the time is consumed when the characteristic coupling relation between a vehicle body structure and a passenger restraint system is researched by a CAE simulation technology, and provides an evaluation method of the characteristic coupling relation between a collision waveform and the restraint system.
In order to solve the technical problems, the invention is realized by adopting the following technical scheme: the method for evaluating the coupling relation between the collision waveform and the characteristic of the restraint system comprises the following steps:
1) establishing an occupant response surface based on a single-degree-of-freedom model:
(1) defining shape characteristic parameters of a double trapezoidal wave and trilinear constraint stiffness curve:
the collision waveforms used in the method for evaluating the characteristic coupling relation between the collision waveforms and the restraint system are all equivalent double-trapezoidal waves, and the stiffness curves of the restraint system used in the method are all trilinear restraint stiffness curves;
(2) solving the occupant response surface by the single-degree-of-freedom model:
the evaluation method of the characteristic coupling relation of the collision waveform and the restraint system takes an occupant response surface as a data basis, wherein the response surface is used for quickly and accurately solving the acceleration response of an occupant by utilizing a single-degree-of-freedom model iterative algorithm to obtain the matching results of different collision waveform parameters and the rigidity parameters of the restraint system;
(3) the response surface XY directions are averaged separately:
averaging the occupant response planes in the X coordinate direction to obtain an average value of all occupant responses corresponding to each collision waveform, and using the symbol AvRepresents;
averaging the occupant response surface in the Y coordinate direction to obtain the average value of all the occupant responses corresponding to the stiffness of each restraint system, and using the symbol ArRepresents;
2) analyzing the correlation between the occupant response and the collision waveform parameters:
(1) supplementing the definition of collision waveform parameters;
(2) extracting collision waveform basic parameters and A from occupant response surfacevCorresponding relation, linearRegression analysis is carried out, and correlation coefficients are summarized;
3) evaluation of the coupling relation of the collision waveform and the characteristic of the restraint system:
on the basis of the correlation analysis of the impact waveform and the stiffness parameter of the constraint system, researching a quantitative evaluation method of the impact waveform, the characteristics of the constraint system and the coupling relation between the impact waveform and the constraint system;
(1) establishing a comprehensive evaluation index alpha of the collision waveform:
establishment of AvThe direct quantitative relation between the parameters of the collision waveform and the parameters of the collision waveform is defined as a function P, the parameters of the deviation constraint system only realize the preliminary individual quantitative evaluation of the collision waveform according to the parameters of the collision waveform, and the established comprehensive evaluation index of the collision waveform is marked as alpha;
(2) establishing a comprehensive evaluation index beta of a constraint system:
establishment of ArThe quantitative relation between the system and the stiffness parameter of the constraint system is defined as a function Q, the initial individual quantitative evaluation of the characteristics of the constraint system is realized only according to the stiffness parameter of the constraint system without collision waveform, and the comprehensive evaluation index of the established constraint system is beta;
(3) a of comprehensive evaluation indexes of collision waveform and constraint system characteristicsoEstablishing:
according to the occupant response surface, when AvAnd ArWhen the value is determined, there is a unique occupant response aoCorrespondingly, the passenger response a is considered as the passenger response a because the sorted passenger response surfaces show regular increasingoAnd AvAnd ArThere is an increasing functional relationship defined as function R, thus establishing a relationship between the individual quantitative evaluation and the overall coupling of the crash waveform and the characteristic of the restraint system, and the established comprehensive evaluation index of the crash waveform and the characteristic of the restraint system is marked as ao。
The shape characteristic parameters for defining the double trapezoidal waves and the trilinear constraint stiffness curve in the technical scheme are as follows:
G1the height of the first step is the acceleration value corresponding to the BC section; the duration of the first step is tBCIn units of g;
G2for the height of the second step, i.e. the acceleration value corresponding to the DE section, the duration of the second step is tDEIn units of g;
s1、s2、s3the slopes of the straight lines AB, CD and the rebound section EF respectively;
C1the unit is m, which is the crushing amount of the front end of the engine;
Cmaxthe maximum dynamic crushing amount of the front end structure of the vehicle body is m;
k1the slope of the OP section is the specific stiffness of the safety belt, and the OP section corresponds to the linear elongation stage of the safety belt;
GLis the force-limited acceleration;
k2the slope of the QR section is the rigidity of the safety airbag;
D1the movement displacement of the passenger relative to the vehicle body when the acting force of the safety belt reaches a limit value;
D2is the movement displacement of the occupant relative to the vehicle body when the airbag is activated.
The definition supplement of the collision waveform parameters in the technical scheme refers to that:
1) step ratio i: two step heights G for defining equivalent double trapezoidal wave2And G1The ratio of the two is a step ratio;
2) width ratio w: the width ratio is the crushing amount C of the front end of the engine1And maximum dynamic crushing amount CmaxThe ratio of (A) to (B);
3) average stiffness KAE: the average rigidity is the second-order height G of the equivalent double trapezoidal wave2And maximum dynamic crushing amount CmaxThe ratio of (A) to (B);
4) energy density ratio a: the energy density ratio is the ratio of the energy absorbed by the front end of the engine to the total energy absorbed by the front end structure of the vehicle body;
in the formula, v0Is the collision velocity in m/s; g1Is the height of the first step, unitIs g; t is tCIs the engine collision time in units of s; s1The slope of the straight line AB section is in g/s;
5) wave form centroid (t)o，Go): the waveform centroid is the centroid of the geometric shape enclosed by the acceleration-time curve and the time axis, and the abscissa of the centroid is called the centroid time toThe centroid ordinate is called centroid acceleration Go；
Wherein t is time and unit s;
is the vehicle body acceleration in g.
The technical scheme is that the single-degree-of-freedom model for solving the occupant response surface refers to the following steps:
(1) solving the single-degree-of-freedom model of the response surface simplifies the vehicle and the passengers into concentrated mass blocks M and M respectively, simplifies the crushing process of the vehicle body structure in collision into the compression process of the spring stiffness K, and approximates the compression process to equivalent double trapezoidal waves; the deformation process of the restraint system in collision is simplified into a compression process of the spring stiffness k, and the spring stiffness k is approximate to trilinear restraint stiffness; the passenger performs forward deceleration movement under the common vibration action of the two spring vibration systems, so that the response magnitude of the passenger is determined by the coupling relation of the two spring vibration systems;
(2) 3204 different double-trapezoid waveforms and 3136 trilinear constraint rigidities can be obtained according to the set shape parameter range and step length; carrying out one-to-one combination on the obtained double-trapezoid waveforms and the rigidity of the constraint system, and rapidly carrying out passenger response solution on each combination by utilizing the existing single-degree-of-freedom model iterative algorithm to obtain the matching results of about 1000 thousands of different double-trapezoid waveforms and different rigidities of the constraint system;
(3) with the numbers of different double-trapezoidal waveforms from 1 to 3204 as X coordinates, the numbers of different restraint system rigidities from 1 to 3136 as Y coordinates, and the peak of the acceleration of the occupant as Z coordinates, the peak response surface of the acceleration of the occupant under the conditions of different crash waveforms and different restraint system rigidities in combination can be drawn, and is referred to as the occupant response surface for short.
The establishment of the comprehensive evaluation index alpha of the collision waveform in the technical scheme refers to the following steps:
establishing a waveform average response AvDetermining a function P according to the direct quantitative relation between the function P and the parameters of the collision waveform, realizing the primary individual evaluation of the collision waveform, and adopting a multiple regression method to approximately construct AvA functional relationship P with a collision waveform parameter;
centroid acceleration G among collision waveform parametersoTime t when the vehicle body displacement reaches the maximum dynamic crushing amountEAverage stiffness KAEHeight G of the second step2The correlation with the occupant response is high, but in consideration of the importance of the basic parameters of the collision waveform, G is selected1、G2Time t when the engine contacts the barrierC、tE、Go、KAEPerforming multiple regression analysis on the six collision waveform parameters; considering the complexity of waveform parameters and the relationship between the waveform parameters, the technical scheme constructs a multiple quadratic regression model, and respectively uses x as the six parameters for convenient description1、x2……x6Six variables represent, corresponding to dependent variable AvThe expression of the multivariate quadratic regression model is as follows:
wherein a is0Is a constant term of1、a2……a6Is a coefficient of a first order term(1,1),a(1,2)……a(6,6)Is a quadratic coefficient; rejecting less influential items by regression analysis, where tCThe items are completely eliminated, 7 items which have large influence on the regression result are left,are each G1、G2、G1G2、tE、tE 2、Go、KAE；
By comparing A of different collision waveformsvThe size of the collision waveform can be evaluated to make AvDimensionless and ArChemotaxis, min-max standardization method, for AvPerforming standardization processing to obtain a dimensionless impact waveform evaluation index, defining the dimensionless impact waveform evaluation index as an 'impact waveform comprehensive evaluation index', and expressing the dimensionless impact waveform evaluation index by using a symbol alpha, wherein the calculation method of the impact waveform comprehensive evaluation index alpha comprises the following steps:
determining A from occupant response surfacevThe maximum value is 79.28g, the minimum value is 36.70g, and according to the formulas (7) and (8), the calculation formula of alpha is obtained as follows:
alpha is distributed between 0 and 1, and the smaller the value, the better the corresponding collision waveform from the viewpoint of the acceleration of the passenger; however, when the collision waveform parameter is out of the usual range, a is larger than 1 or smaller than 0.
The establishment of the comprehensive evaluation index beta of the constraint system in the technical scheme refers to the following steps:
establishment of ArDetermining a function Q through a direct quantitative relation with the stiffness parameter of the constraint system, and realizing the primary individual evaluation of the characteristics of the constraint system; approximation of Structure A also Using multiple regressionrA functional relationship Q with a stiffness parameter of the constraint system;
selecting all stiffness parameters k of the constraint system because the stiffness parameters of the constraint system are less1、k2、GL、D2Constructing a multiple quadratic regression model, and respectively using the four parameters as y for convenient description1、y2、y3、y4Four variables are expressed, and the corresponding dependent variable is ArThe expression of the multivariate quadratic regression model is as follows:
wherein b is0Is a constant term, b1、b2、b3、b4Is a coefficient of a first order term, b(1,1)、b(1,2)……b(4,4)Is a quadratic coefficient; rejecting less influential items by regression analysis, where parameter D2Is completely removed, and remains 7 items which have great influence on the regression model and are respectively k2、k1 2、k2 2、GL 2、k1k2、k1GL、k2GL；
By comparing A of stiffness of different restraint systemsrThe size can realize the evaluation of the rigidity of the constraint system, so as to make ArDimensionless and AvChemotaxis, min-max standardization method, for ArThe standardized processing is carried out to obtain the evaluation index of the dimensionless constraint system characteristic, the evaluation index is defined as a comprehensive evaluation index of the constraint system and is expressed by a symbol beta, and the calculation method comprises the following steps:
determining A from occupant response surfacerA maximum value of 69.12g and a minimum value of 44.60 g; from equations (10) and (11), β is calculated as:
beta is distributed between 0 and 1, and the smaller the value is, the better the corresponding rigidity of the restraint system is from the viewpoint of the acceleration of the passengers; however, situations where β is greater than 1 or less than 0 may occur when the constraint system stiffness parameter is outside the usual range.
A of comprehensive evaluation indexes of collision waveform and constraint system characteristics in the technical schemeoThe establishment of (A) means:
establishing occupant acceleration response aoAnd direct quantitative relation between the comprehensive collision waveform evaluation index alpha and the comprehensive restraint system evaluation index beta, so that integral coupling relation evaluation is realized according to the initial independent evaluation results of the collision waveform and the characteristics of the restraint system, and alpha and beta are respectively expressed by AvAnd ArIs obtained by a standardized process, sooAnd AvAnd ArMay be equivalent to aoAnd an increasing functional relationship R between α and β; the occupant response surface can be drawn according to the corresponding relation of alpha and beta to form alpha-beta-aoThe response surface is replaced by the grid for convenient observation, and the whole curved surface presents a better increasing trend;
approximate construction a by adopting curved surface fitting methodoAnd an increasing functional relationship R between alpha and beta, with alpha and beta as arguments, for alpha-beta-aoThe response surface is fitted with a quadratic surface as shown in equation (13), where c0、c1、c2、c3、c4、c5Obtaining coefficient values of each item through a least square method for each item of the coefficient;
ao＝c0+c1α+c2β+c3α2+c4αβ+c5β2 (13)
since the coefficients of the squared terms of α and β are close to 0, the surface fitting equation can be simplified as:
ao＝280.5+335.1α+161.8β+168αβ (14)
the coefficient of determination R of the fitting result2And the fitting precision is high and reaches 0.986.
Compared with the prior art, the invention has the beneficial effects that:
1. according to the method for evaluating the characteristic coupling relationship between the collision waveform and the restraint system, the characteristic coupling relationship between the collision waveform and the restraint system can be evaluated through the comprehensive collision waveform evaluation index alpha and the comprehensive restraint system evaluation index beta, and a link with a problem in the design process of the collision waveform and the restraint system parameters can be found visually.
2. The invention relates to an evaluation method for characteristic coupling relation of collision waveform and restraint system to establish alpha-beta-aoThe response surface is fitted with a curved surface, the passenger acceleration peak value can be estimated through the collision waveform comprehensive evaluation index alpha and the restraint system comprehensive evaluation index beta, the method is simple and convenient, and the error of calculation with a single-degree-of-freedom model is controlled to be 10%.
Drawings
The invention is further described with reference to the accompanying drawings in which:
FIG. 1 is a flow chart of a method for evaluating a coupling relationship between a collision waveform and a characteristic of a restraint system according to the present invention;
FIG. 2-a is a schematic diagram of a vehicle body-passenger single degree of freedom solution model in the method for evaluating the characteristic coupling relationship between a collision waveform and a restraint system according to the invention;
FIG. 2-b is a schematic diagram of a double trapezoidal wave adopted by a vehicle body-passenger single degree of freedom solution model in the method for evaluating the characteristic coupling relationship between a collision waveform and a restraint system according to the invention;
FIG. 2-c is a schematic diagram of a trilinear stiffness curve adopted by a vehicle body-passenger single degree of freedom solution model in the method for evaluating the characteristic coupling relationship between a collision waveform and a restraint system according to the present invention;
FIG. 3-a is a schematic diagram of time domain equivalent double-trapezoid waveform parameters in the method for evaluating the characteristic coupling relationship between a collision waveform and a restraint system according to the present invention;
FIG. 3-b is a schematic diagram of a displacement domain equivalent double-trapezoid waveform parameter in the method for evaluating the characteristic coupling relationship between a collision waveform and a constraint system according to the present invention;
FIG. 4 is a schematic diagram of trilinear constraint stiffness characteristic parameters in the method for evaluating the characteristic coupling relationship between a collision waveform and a constraint system;
FIG. 5 is a schematic diagram of a method for evaluating a coupling relationship between a collision waveform and a characteristic of a restraint system according to the present invention;
FIG. 6 is the bookThe invention relates to an alpha-beta-a evaluation method of a characteristic coupling relation between a collision waveform and a constraint systemoA response surface map;
FIG. 7 is a diagram illustrating six double-trapezoidal waveforms extracted in the method for evaluating the characteristic coupling relationship between a collision waveform and a restraint system according to the present invention;
FIG. 8 is a corresponding relationship between a comprehensive evaluation index α of a collision waveform and a peak acceleration of the chest of an occupant in the evaluation method of a characteristic coupling relationship between a collision waveform and a restraint system according to the present invention;
FIG. 9 is a corresponding relationship between a comprehensive evaluation index β of the restraint system and a peak chest acceleration of the occupant in the evaluation method of the characteristic coupling relationship between the collision waveform and the restraint system according to the present invention;
FIG. 10 is a diagram illustrating the relationship between peak chest acceleration of an occupant in the method for evaluating the coupling relationship between crash waveforms and the characteristics of a restraint system according to the present invention.
Detailed Description
The invention is described in detail below with reference to the attached drawing figures:
referring to fig. 1, the steps of the method for evaluating the coupling relationship between the collision waveform and the characteristic of the restraint system according to the present invention are as follows:
1. establishment of passenger response surface based on single-degree-of-freedom model
1) Shape characteristic parameters for defining double trapezoidal wave and trilinear constraint stiffness curves
Referring to fig. 3-a to 3-b, the collision waveforms used in the method for evaluating the characteristic coupling relationship between the collision waveform and the restraint system are all equivalent double trapezoidal waves, and A, B, C, D, E, F in fig. 3-a is a characteristic point of the equivalent double trapezoidal waves; wherein: a is a collision occurrence point, and the corresponding time is 0; b is a point where the front longitudinal beam touches the barrier; c is the contact point of the engine and the barrier, and the corresponding time is tC(ii) a D is a point where the upper edge beam touches the barrier; e is the point that the displacement of the vehicle body reaches the maximum dynamic crushing amount, and the corresponding time is tE，tEAnd the maximum dynamic crushing time tmaxEqual; f is a collision end point;
G1the first-stage acceleration value is the acceleration value corresponding to the BC section; first of allThe duration of the step acceleration being tBCIn units of g;
G2is a second-order acceleration value, i.e. an acceleration value corresponding to the DE segment, the duration of the second-order acceleration being tDEIn units of g;
s1、s2、s3the slopes of the straight lines AB, CD and the rebound section EF respectively;
C1the unit is m, which is the crushing amount of the front end of the engine;
Cmaxthe maximum dynamic crushing amount of the front end structure of the vehicle body is m.
Referring to fig. 4, the stiffness curves of the restraint system used in the method for evaluating the characteristic coupling relationship between the collision waveform and the restraint system are all trilinear restraint stiffness curves. O, P, Q, R in FIG. 4 is the characteristic point of "trilinear restraining stiffness", where O is the collision occurrence point; the point P is an action point of the safety belt force limiting device; the point Q is the starting point of the safety airbag; the R point is the maximum relative displacement point.
k1The slope of the OP section is the specific stiffness of the safety belt, and the OP section corresponds to the linear elongation stage of the safety belt;
GLis the force-limited acceleration;
k2the slope of the QR section is the rigidity of the safety airbag;
D1the movement displacement of the passenger relative to the vehicle body when the acting force of the safety belt reaches a limit value;
D2is the movement displacement of the occupant relative to the vehicle body when the airbag is activated.
2) Single degree of freedom model solution passenger response surface
The method for evaluating the characteristic coupling relation of the collision waveform and the restraint system takes the response surface of an occupant as the data base. The response surface is a matching result of different collision waveform parameters and the stiffness parameters of the restraint system, which is obtained by utilizing a single-degree-of-freedom model iterative algorithm to quickly and accurately solve the acceleration response of the passenger.
(1) With reference to fig. 2-a to 2-c, solving the single degree of freedom model of the response surface simplifies the vehicle and the passenger into concentrated mass blocks M and M, respectively, and simplifies the collapse process of the vehicle body structure in collision into the compression process of the spring stiffness K, and approximates to an equivalent double trapezoidal wave; the deformation process of the restraint system in collision is simplified into a compression process of the spring stiffness k, and the spring stiffness k is approximate to trilinear restraint stiffness; the passenger performs forward deceleration movement under the common vibration action of the two spring vibration systems, so that the response magnitude of the passenger is determined by the coupling relation of the two spring vibration systems.
(2) From the set shape parameter ranges and step sizes, 3204 different double trapezoidal waveforms and 3136 trilinear constraint stiffnesses can be obtained, see table 1. The obtained double-trapezoid waveforms and the rigidity of the restraint system are combined in a one-to-one mode, the existing single-degree-of-freedom model iterative algorithm is utilized to quickly solve the passenger response of each combination, and the matching results of about 1000 thousands of different double-trapezoid waveforms and different rigidities of the restraint system are obtained, as shown in table 2, wherein a in the table0Is the peak of the occupant acceleration.
TABLE 1 Range and step size of shape parameters
TABLE 2 matching results of different crash waveform parameters and stiffness parameters of the restraint system
(3) With the numbers of different double-trapezoidal waveforms from 1 to 3204 as X coordinates, the numbers of different restraint system rigidities from 1 to 3136 as Y coordinates, and the peak of the acceleration of the occupant as Z coordinates, the peak response surface of the acceleration of the occupant under the conditions of different crash waveforms and different restraint system rigidities in combination can be drawn, and is referred to as the occupant response surface for short.
3) Averaging the XY directions of the response surfaces
Averaging the occupant response planes in the X coordinate direction to obtain an average value of all occupant responses corresponding to each collision waveform, and using the symbol AvRepresents; averaging the occupant response surface in the Y coordinate direction to obtain the average value of all the occupant responses corresponding to the stiffness of each restraint system, and using the symbol ArAnd (4) showing.
2. Analysis of correlation between occupant response and crash waveform parameters
1) The definition of the crash waveform parameters is supplemented as follows:
(1) step ratio i: two step heights G for defining equivalent double trapezoidal wave2And G1The ratio of the two is a step ratio;
(2) width ratio w: the width ratio is the crushing amount C of the front end of the engine1And maximum dynamic crushing amount CmaxThe ratio of (A) to (B);
(3) average stiffness KAE: the average rigidity is the second-order height G of the equivalent double trapezoidal wave2And maximum dynamic crushing amount CmaxThe ratio of (A) to (B);
(4) energy density ratio a: the energy density ratio is the ratio of the energy absorbed by the front end of the engine to the total energy absorbed by the front end structure of the vehicle body;
in the formula, v0Is the collision velocity in m/s; g1Is the height of the first step in g; t is tCIs the engine collision time in units of s; s1The slope of the segment AB is shown in g/s.
(5) Wave form centroid (t)o，Go): the waveform centroid is the centroid of the geometric shape enclosed by the acceleration-time curve and the time axis, and the abscissa of the centroid is called the centroid time toThe centroid ordinate is called centroid acceleration Go；
Wherein t is time and unit s;
is the vehicle body acceleration in g.
2) Extracting collision waveform basic parameters and A from occupant response surfacevThe correlation, which is shown in table 3, was analyzed by linear regression using Origin mapping software and the correlation coefficients were summarized;
TABLE 3 Collision waveform parameters with AvCorrelation
As can be seen from Table 3, Go、tE、KAE、G2The correlation with occupant response is high.
3. Evaluation of collision waveform and constraint system characteristic coupling relation
On the basis of the correlation analysis of the impact waveform and the stiffness parameter of the constraint system, a quantitative evaluation method of the impact waveform, the characteristics of the constraint system and the coupling relation between the impact waveform and the constraint system is researched. A. thevAlthough the crash waveform can be approximately characterized, the calculation process still requires the intervention of constraint system parameters. Establishment of AvThe direct quantitative relation between the parameters and the collision waveform, as shown in the formula 1 and the function P, can be separated from the parameters of the constraint system and only realize the preliminary independent quantitative evaluation of the collision waveform according to the parameters of the collision waveform; establishment of ArThe quantitative relation between the system and the stiffness parameter of the constraint system can be separated from the collision waveform to realize the preliminary individual quantitative evaluation of the characteristic of the constraint system only according to the stiffness parameter of the constraint system in a form shown by a function Q of a formula 2;
Av＝P(G1,G2,tE,tC,...) (4)
Ar＝Q(k1,k2,GL,D1,...) (5)
according to the occupant response surface, when AvAnd ArWhen the value is determined, there is a unique occupant acceleration response aoAnd correspondingly. The occupant response a can be considered as the occupant response surface after sequencing shows regular increasing increase on the wholeoAnd AvAnd ArAn increasing functional relation exists between the collision waveform and the characteristic of the constraint system, and the relation between the independent quantitative evaluation and the overall coupling can be established in the form of a function R shown in formula 3;
ao＝R(Av,Ar) (6)
referring to fig. 5, the above functional relationship is determined to establish the whole evaluation method of the coupling relationship, which mainly includes the following steps:
(1) determining a function P by adopting a multiple regression method, so as to realize preliminary independent evaluation of the collision waveform according to the collision waveform parameters;
(2) determining a function Q by adopting a multiple regression method, so as to realize the primary individual evaluation of the characteristics of the constraint system according to the stiffness parameters of the constraint system;
(3) and determining a function R through a surface fitting function of MATLAB software, so as to realize the evaluation of the overall coupling relation according to the collision waveform and the initial individual evaluation result of the characteristics of the constraint system.
1) Establishment of comprehensive evaluation index alpha of collision waveform
This step is mainly to establish the average response A of the waveformvAnd determining a function P through a direct quantitative relation between the function P and the collision waveform parameters, and realizing the primary independent evaluation of the collision waveform. The technical scheme adopts a multiple regression method to approximate a structure AvAs a function of the parameters of the crash waveform P.
Among collision waveform parameters Go、tE、KAE、G2The correlation with the response of the passenger is high, but the technical scheme selects G in consideration of the importance of basic parameters of the collision waveform1、G2、tC、tE、Go、KAEPerforming multiple regression on the six collision waveform parametersAnd (6) analyzing. In consideration of the complexity of waveform parameters and the relationship between the waveform parameters, the technical scheme constructs a multiple quadratic regression model. For convenience of description, the six parameters are respectively represented by x1、x2……x6Six variables represent, corresponding to dependent variable AvThe expression of the multivariate quadratic regression model is as follows:
wherein a is0Is a constant term of1、a2……a6Is a coefficient of a first order term(1,1),a(1,2)……a(6,6)Is a quadratic coefficient. Rejecting less influential items by regression analysis, where tCThe entries are completely eliminated, leaving 7 entries that have a large impact on the regression results, with each entry and the corresponding coefficients shown in table 4.
TABLE 4 Collision waveform parameter quadratic regression correspondence terms and coefficients
The analysis results of the multiple quadratic regression model are shown in table 5. The judgment coefficient is close to 1, the F statistic is large, and the tested P value is 0, so that the regression result is better.
TABLE 5 analysis results of the Secondary regression model of the parameters of the Collision waveform
AvRepresenting the average level of the crash waveform by comparing A's of different crash waveformsvThe size can realize the quality evaluation of the collision waveform. To make AvDimensionless and ArThe chemotaxis is the same, the technical scheme adopts a min-max standardization method to AvStandardizing to obtain dimensionless evaluation index of collision waveform, and definingThe "collision waveform comprehensive evaluation index" is represented by the symbol α. The method for calculating the comprehensive evaluation index alpha of the collision waveform comprises the following steps:
determining A from occupant response surfacevThe maximum value was 79.28g and the minimum value was 36.70 g. According to equations (7) and (8), the α calculation equation is obtained as:
α is distributed between 0 and 1, and a smaller value corresponds to a better collision waveform only from the viewpoint of acceleration of the occupant. However, when the parameters of the collision waveform are beyond the usual range determined by the present solution, a greater than 1 or less than 0 may occur.
2) Establishment of comprehensive evaluation index beta of constraint system
This step is mainly based on the establishment of ArDetermining a function Q through a direct quantitative relation with the stiffness parameter of the constraint system, and realizing the primary individual evaluation of the characteristics of the constraint system; the step also adopts a multiple regression method to approximate the structure ArAnd a functional relationship Q with a stiffness parameter of the restraint system.
Because the stiffness parameters of the constraint system are less, all the stiffness parameters k of the constraint system are selected in the technical scheme1、k2、GL、D2And constructing a multiple quadratic regression model. For convenience of description, these four parameters are respectively represented by y1、y2、y3、y4Four variables are expressed, and the corresponding dependent variable is Ar. The expression of the multivariate quadratic regression model is as follows:
wherein b is0Is a constant term, b1、b2、b3、b4Is a coefficient of a first order term, b(1,1)、b(1,2)……b(4,4)Is a quadratic coefficient. Rejecting less influential items by regression analysis, where parameter D2The regression model was completely eliminated, leaving 7 items that had a large effect on the regression model, each item and the corresponding coefficient being shown in table 6.
TABLE 6 constraint system stiffness parameter quadratic regression corresponding items and coefficients
The analysis results of the multiple quadratic regression model are shown in table 7. The judgment coefficient is close to 1, F statistic is large, and the tested P value is 0, so that the regression result is good.
TABLE 7 analysis results of the quadratic regression model for stiffness parameters of the constraint system
ArRepresents the average level of stiffness of the restraint system, A by comparing the stiffness of different restraint systemsrAnd the quality evaluation of the rigidity of the constraint system can be realized by the size. To make ArDimensionless and AvChemotaxis of Mega, min-max normalization method used herein, for ArThe standardized processing is carried out to obtain the evaluation index of the dimensionless constraint system characteristic, the evaluation index is defined as a comprehensive evaluation index of the constraint system and is expressed by a symbol beta, and the calculation method comprises the following steps:
determining A from occupant response surfacerThe maximum value was 69.12g and the minimum value was 44.60 g. From equations (10) and (11), β is calculated as:
the beta is distributed between 0 and 1, with smaller values corresponding to better restraint system stiffness from the occupant acceleration point of view only. However, situations where β is greater than 1 or less than 0 may occur when the constraint system stiffness parameter is outside the usual range determined by the present solution.
3) A of comprehensive evaluation indexes of collision waveform and constraint system characteristicsoEstablishment of (2)
The collision waveform and the characteristic of the restraint system can be respectively and independently evaluated preliminarily through the comprehensive evaluation index alpha of the collision waveform and the comprehensive evaluation index beta of the restraint system. The ultimate occupant protection is, however, determined by both the crash waveform and the restraint system characteristics. Even if the crash waveform is well designed, if the corresponding poor characteristics of the restraint system are met, the good occupant protection effect is probably not achieved totally, and the good crash waveform is only a precondition for ensuring the compatibility and matching of the restraint system. The same good restraint system behavior is only a prerequisite for a consistent matching of the crash waveforms.
This step essentially establishes the occupant acceleration response aoAnd the direct quantitative relation between the collision waveform comprehensive evaluation index alpha and the restraint system comprehensive evaluation index beta, so that the overall coupling relation evaluation is realized according to the initial individual evaluation results of the collision waveform and the restraint system characteristics. Since alpha and beta are respectively represented by AvAnd ArIs obtained by a standardized process, sooAnd AvAnd ArMay be equivalent to aoAnd an increasing functional relationship R between a and β. The occupant response surface can be drawn according to the corresponding relation of alpha and beta to form alpha-beta-aoThe response surface is replaced by a grid for easy observation, and the whole curved surface presents a better increasing trend as shown in fig. 6.
The technical scheme adopts a curved surface fitting method to approximate a structure aoAnd an increasing functional relationship R between a and β. With alpha and beta as independent variables, for alpha-beta-aoThe response surface is fitted with a quadratic surface as shown in equation (13). Wherein c is0、c1、c2、c3、c4、c5Is the coefficient of each item. The values of the coefficients obtained by the least squares method are shown in table 8.
ao＝c0+c1α+c2β+c3α2+c4αβ+c5β2 (13)
TABLE 8 alpha-beta-aoResponse surface quadric surface fitting result
Since the coefficients of the squares of α and β are close to 0, the surface fitting equation can be simplified as:
ao＝280.5+335.1α+161.8β+168αβ (14)
the coefficient of determination R of the fitting result2And the fitting precision is high and reaches 0.986.
Example 1
M6 vehicle type collision waveform and constraint system characteristic coupling relation evaluation
The present embodiment evaluates the collision waveform, the characteristic of the restraint system and the coupling relationship between the two of the M6 vehicle model according to the method for evaluating the coupling relationship between the collision waveform and the characteristic of the restraint system. The collision waveform parameters and the stiffness parameters of the restraint system of the M6 vehicle model are shown in a table 9. The evaluation method comprises the following steps:
TABLE 9M6 vehicle type collision waveform and restraint system stiffness parameter
1. Establishing passenger response surface based on single-degree-of-freedom model
3204 different double-trapezoidal waveforms and 3136 trilinear constraint stiffnesses can be obtained according to the value ranges and step lengths of the shape parameters of the equivalent double-trapezoidal wave and trilinear stiffness curves set in table 1. The obtained double-trapezoid waveform and the rigidity of the constraint system are combined one to one, and the existing single-degree-of-freedom model iterative algorithm is utilized to quicklyThe occupant response solution is carried out on each combination to obtain the matching results of about 1000 million different double-trapezoid waveforms and different stiffness of the restraint system, as shown in table 2, wherein a0Is the peak of the occupant acceleration.
With the numbers of different double-trapezoid waveforms from 1 to 3204 as X coordinates, the numbers of different restraint system rigidities from 1 to 3136 as Y coordinates, and the peak value of the acceleration of the passenger as Z coordinates, the peak value response surface of the acceleration of the passenger under the conditions of different collision waveforms and different restraint system rigidities can be drawn, and is referred to as the passenger response surface for short
Averaging the occupant response planes in the X coordinate direction to obtain an average value of all occupant responses corresponding to each collision waveform, and using the symbol AvAnd (4) showing. Averaging the response surface in the Y coordinate direction to obtain the average value of all responses corresponding to the stiffness of each constraint system, and using the symbol ArAnd (4) showing.
2. Analysis of correlation between occupant response and crash waveform parameters
Extracting crash waveform basic parameters (G) from occupant response surfaces1、G2、C1、Cmax、tC、tE、i、w、KAE、a、Go、to) And AvFor the correspondence, linear regression analysis was performed and the correlation coefficients were summarized as shown in table 3. As can be seen from Table 3, Go、tE、KAE、G2The correlation with occupant response is high.
3. Evaluation of collision waveform and constraint system characteristic coupling relation
1) Construction AvAnd collision waveform parameter (G)1、G2、tE、GO、KAE) The functional relationship P (multiple quadratic regression model) of (a), the analysis results are shown in table 5:
TABLE 5 analysis results of the Secondary regression model of the parameters of the Collision waveform
Standardized by min-maxMethod of using formula (5) to AvAnd carrying out standardization processing to obtain a dimensionless comprehensive evaluation index alpha of the collision waveform. Determining A from occupant response surfacevThe maximum value was 79.28g and the minimum value was 36.70 g. Obtaining an alpha calculation formula as a formula (9) according to the formulas (7) and (8);
the collision waveform comprehensive evaluation index α of the M6 vehicle type can be calculated by using formula (9) according to the parameters in table 9:
2) construction ArAnd constraint system stiffness parameter (k)1、k2、GL) The functional relationship Q (multiple quadratic regression model) of (1), the analysis results are shown in Table 6:
TABLE 6 constraint system stiffness parameter quadratic regression corresponding items and coefficients
For A, using min-max normalization, according to equation (7)rAnd carrying out standardization treatment to obtain a dimensionless comprehensive evaluation index beta of the constraint system. Determining A from occupant response surfacerThe maximum value was 69.12g and the minimum value was 44.60 g. From equations (10) and (11), β is calculated as equation (12):
the comprehensive evaluation index beta of the restraint system of the M6 vehicle model can be calculated by using the formula (12) according to the parameters in the table 9:
3) approximate construction of passenger acceleration response a by adopting curved surface fitting methodoAnd an increasing functional relation R between the comprehensive evaluation index alpha of the collision waveform and the comprehensive evaluation index beta of the restraint system. With alpha and beta as independent variables, for alpha-beta-aoThe response surface is subjected to quadratic surface fitting, and the surface fitting formula is shown as (13), wherein c0、c1、c2、c3、c4、c5Is the coefficient of each item. The coefficient values obtained by the least square method are shown in table 8;
TABLE 8 alpha-beta-aoResponse surface quadric surface fitting result
The square terms of alpha and beta are cut off, and the surface fitting formula is as follows:
ao＝280.5+335.1α+161.8β+168αβ (14)
using alpha-beta-aoThe curved surface fitting equation (14) of (4) can calculate the acceleration response a of the passenger of the M6 vehicle modelo：
Calculated expressions of alpha and beta, and alpha-beta-aoThe surface fitting formula can be directly applied to the evaluation of any vehicle type;
as can be seen from the evaluation of the coupling relationship between the collision waveform and the restraint system characteristics of the M6 vehicle model, the peak value of the acceleration of the occupant is 580.74M/s2Exceeding 50g indicates a poor match between the crash waveform and the restraint system characteristics of the vehicle type. Beta is smaller than alpha, and is worse than the collision waveform, and the collision waveform can be optimized to be reduced subsequentlyPeak occupant acceleration.
Example 2
The present embodiment further verifies the three ranking indexes of the present invention in Madymo software by using a simulation model of the M6 occupant restraint system.
Six double trapezoidal waveforms with α of 0, 0.2, 0.4, 0.6, 0.8, 1, respectively, were selected from 3204 collision waveforms, as shown in fig. 8. Six of the 3136 restraint system stiffnesses corresponding to β of 0, 0.2, 0.4, 0.6, 0.8, 1, respectively, are selected, and their restraint system parameters are shown in table 9.
TABLE 9 conversion of constraint System stiffness parameters to constraint System parameters
And sequentially taking the selected six waveforms as an acceleration field of an M6 passenger restraint system simulation model, keeping the restraint system unchanged, and obtaining a corresponding passenger chest acceleration response curve through simulation calculation. According to the relationship between alpha and the peak value of the acceleration of the chest of the passenger, as shown in fig. 8, the two have high consistency.
And (3) sequentially adjusting the restraint system parameters of the simulation model of the M6 passenger restraint system into six groups of restraint system parameter values in the table 9, keeping the collision waveform unchanged, and obtaining a corresponding passenger chest acceleration response curve through simulation calculation. According to the relationship between beta and the peak value of the acceleration of the chest of the passenger, as shown in fig. 9, the two have high consistency.
And (3) combining 6 collision waveforms and 6 groups of restraint system parameters into 36 coupling conditions in a crossed manner, sequentially substituting the coupling conditions into an M6 passenger restraint system simulation model, and obtaining 36 groups of passenger chest acceleration curves through simulation calculation. The peak value of the acceleration curve of the chest of each passenger is extracted and drawn into a response surface, as shown in fig. 10, the integral trend of the response surface obtained by the fitting formula is basically consistent, and the error of the peak value of the acceleration of the chest of the passenger is controlled to be 10%.
Claims (7)
1. A method for evaluating the coupling relation between collision waveforms and characteristics of a constraint system is characterized by comprising the following steps:
1) establishing an occupant response surface based on a single-degree-of-freedom model:
(1) defining shape characteristic parameters of a double trapezoidal wave and trilinear constraint stiffness curve:
the collision waveforms used in the method for evaluating the characteristic coupling relation between the collision waveforms and the restraint system are all equivalent double-trapezoidal waves, and the stiffness curves of the restraint system used in the method are all trilinear restraint stiffness curves;
(2) solving the occupant response surface by the single-degree-of-freedom model:
the evaluation method of the characteristic coupling relation of the collision waveform and the restraint system takes an occupant response surface as a data basis, wherein the response surface is used for quickly and accurately solving the acceleration response of an occupant by utilizing a single-degree-of-freedom model iterative algorithm to obtain the matching results of different collision waveform parameters and the rigidity parameters of the restraint system;
(3) the response surface XY directions are averaged separately:
averaging the occupant response planes in the X coordinate direction to obtain an average value of all occupant responses corresponding to each collision waveform, and using the symbol AvRepresents;
averaging the occupant response surface in the Y coordinate direction to obtain the average value of all the occupant responses corresponding to the stiffness of each restraint system, and using the symbol ArRepresents;
2) analyzing the correlation between the occupant response and the collision waveform parameters:
(1) supplementing the definition of collision waveform parameters;
(2) extracting collision waveform basic parameters and A from occupant response surfacevPerforming linear regression analysis on the corresponding relation, and summarizing correlation coefficients;
3) evaluation of the coupling relation of the collision waveform and the characteristic of the restraint system:
on the basis of the correlation analysis of the impact waveform and the stiffness parameter of the constraint system, researching a quantitative evaluation method of the impact waveform, the characteristics of the constraint system and the coupling relation between the impact waveform and the constraint system;
(1) establishing a comprehensive evaluation index alpha of the collision waveform:
establishment of AvThe direct quantitative relation between the parameters of the collision waveform and the parameters of the collision waveform is defined as a function P, the parameters of the deviation constraint system only realize the preliminary individual quantitative evaluation of the collision waveform according to the parameters of the collision waveform, and the established comprehensive evaluation index of the collision waveform is marked as alpha;
(2) establishing a comprehensive evaluation index beta of a constraint system:
establishment of ArThe quantitative relation between the system and the stiffness parameter of the constraint system is defined as a function Q, the initial individual quantitative evaluation of the characteristics of the constraint system is realized only according to the stiffness parameter of the constraint system without collision waveform, and the comprehensive evaluation index of the established constraint system is beta;
(3) alpha of comprehensive evaluation index of collision waveform and constraint system characteristicsoEstablishing:
according to the occupant response surface, when AvAnd ArWhen the value is determined, there is a unique occupant acceleration response aocCorrespondingly, the passenger acceleration response a is considered as the passenger response surface after sequencing shows regular increasing increase on the wholeocAnd AvAnd ArAn increasing function relation exists between the collision waveform and the characteristic of the constraint system, the relation is defined as a function R, so that the relation between the independent quantitative evaluation and the overall coupling of the collision waveform and the characteristic of the constraint system is established, and the established comprehensive evaluation index of the collision waveform and the characteristic of the constraint system is marked as alphao。
2. The method for evaluating the characteristic coupling relationship between the collision waveform and the restraint system according to claim 1, wherein the shape characteristic parameters defining the double trapezoidal wave and trilinear restraint stiffness curves are as follows:
G1the height of the first step is the acceleration value corresponding to the BC section; the duration of the first step is tBCIn units of g;
G2for the height of the second step, i.e. the acceleration value corresponding to the DE section, the duration of the second step is tDEIn units of g;
s1、s2、s3the slopes of the straight lines AB, CD and the rebound section EF respectively;
C1the unit is m, which is the crushing amount of the front end of the engine;
Cmaxthe maximum dynamic crushing amount of the front end structure of the vehicle body is m;
k1the slope of the OP section is the specific stiffness of the safety belt, and the OP section corresponds to the linear elongation stage of the safety belt;
GLis the force-limited acceleration;
k2the slope of the QR section is the rigidity of the safety airbag;
D1the movement displacement of the passenger relative to the vehicle body when the acting force of the safety belt reaches a limit value;
D2is the movement displacement of the occupant relative to the vehicle body when the airbag is activated.
3. The method for evaluating the coupling relationship between the collision waveform and the characteristics of the restraint system according to claim 1, wherein the definition of the collision waveform parameters is supplemented by:
1) step ratio i: two step heights G for defining equivalent double trapezoidal wave2And G1The ratio of the two is a step ratio;
2) width ratio w: the width ratio is the crushing amount C of the front end of the engine1And maximum dynamic crushing amount CmaxThe ratio of (A) to (B);
3) average stiffness KAE: second step height G with average rigidity of equivalent double trapezoidal waves2And maximum dynamic crushing amount CmaxThe ratio of (A) to (B);
4) energy density ratio a: the energy density ratio is the ratio of the energy absorbed by the front end of the engine to the total energy absorbed by the front end structure of the vehicle body;
in the formula: v. of0Is the collision velocity in m/s; g1Is the height of the first step in g; t is tCIs the engine collision time in units of s; s1The slope of the straight line AB section is in g/s;
5) wave form centroid (t)o，Go): the waveform centroid is the centroid of the geometric shape enclosed by the acceleration-time curve and the time axis, and the abscissa of the centroid is called the centroid time toThe centroid ordinate is called centroid acceleration Go；
In the formula: t is time, unit s; is the vehicle body acceleration in g.
4. The method for evaluating the coupling relationship between the collision waveform and the characteristic of the restraint system according to claim 1, wherein the solving of the occupant response surface by the single-degree-of-freedom model comprises the following steps:
(1) solving the single-degree-of-freedom model of the response surface simplifies the vehicle and the passengers into concentrated mass blocks M and M respectively, simplifies the crushing process of the vehicle body structure in collision into the compression process of the spring stiffness K, and approximates the compression process to equivalent double trapezoidal waves; the deformation process of the restraint system in collision is simplified into a compression process of the spring stiffness k, and the spring stiffness k is approximate to trilinear restraint stiffness; the passenger performs forward deceleration movement under the common vibration action of the two spring vibration systems, so that the response magnitude of the passenger is determined by the coupling relation of the two spring vibration systems;
(2) 3204 different double-trapezoid waveforms and 3136 trilinear constraint rigidities can be obtained according to the set shape parameter range and step length; carrying out one-to-one combination on the obtained double-trapezoid waveforms and the rigidity of the constraint system, and rapidly carrying out passenger response solution on each combination by utilizing the existing single-degree-of-freedom model iterative algorithm to obtain the matching results of 1000 ten thousand different double-trapezoid waveforms and different rigidity of the constraint system;
(3) with the numbers of different double-trapezoidal waveforms from 1 to 3204 as X coordinates, the numbers of different restraint system rigidities from 1 to 3136 as Y coordinates, and the peak of the acceleration of the occupant as Z coordinates, the peak response surface of the acceleration of the occupant under the conditions of different crash waveforms and different restraint system rigidities in combination can be drawn, and is referred to as the occupant response surface for short.
5. The method for evaluating the coupling relationship between the collision waveform and the characteristics of the restraint system according to claim 1, wherein the establishment of the comprehensive evaluation index α of the collision waveform is as follows:
establishing a waveform average response AvDetermining a function P according to the direct quantitative relation between the function P and the parameters of the collision waveform, realizing the primary individual evaluation of the collision waveform, and adopting a multiple regression method to approximately construct AvA functional relationship P with a collision waveform parameter;
centroid acceleration G among collision waveform parametersoTime t when the vehicle body displacement reaches the maximum dynamic crushing amountEAverage stiffness KAEHeight G of the second step2G is selected in consideration of the importance of the basic parameters of the collision waveform, although the correlation with the occupant response is high1、G2Time t when the engine contacts the barrierC、tE、Go、KAEPerforming multiple regression analysis on the six collision waveform parameters; considering the complexity of waveform parameters and the relationship among the waveform parameters, a multiple quadratic regression model is constructed, and the six parameters are respectively used as x for convenient description1、x2......x6Six variables represent, corresponding to dependent variable AvThe expression of the multivariate quadratic regression model is as follows:
wherein a is0Is a constant term of1、a2......a6Is a coefficient of a first order term(1，1)，a(1，2)......a(6，6)Is a quadratic coefficient; by passingRegression analysis rejects less affected items, where tCThe items are completely eliminated, and 7 items with large influence on the regression result are left, namely G1、G2、G1G2、tE、tE 2、Go、KAE；
By comparing A of different collision waveformsvThe size of the collision waveform can be evaluated to make AvDimensionless and ArChemotaxis, min-max standardization method, for AvPerforming standardization processing to obtain a dimensionless impact waveform evaluation index, defining the dimensionless impact waveform evaluation index as an 'impact waveform comprehensive evaluation index', and expressing the dimensionless impact waveform evaluation index by using a symbol alpha, wherein the calculation method of the impact waveform comprehensive evaluation index alpha comprises the following steps:
determining A from occupant response surfacevThe maximum value is 79.28g, the minimum value is 36.70g, and according to the formulas (7) and (8), the calculation formula of alpha is obtained as follows:
alpha is distributed between 0 and 1, and the smaller the value, the better the corresponding collision waveform from the viewpoint of the acceleration of the passenger; however, when the collision waveform parameter is out of the usual range, a is larger than 1 or smaller than 0.
6. The method for evaluating the coupling relationship between the collision waveform and the characteristics of the constraint system according to claim 1, wherein the establishment of the comprehensive evaluation index β of the constraint system is as follows:
establishment of ArDetermining a function Q through a direct quantitative relation with the stiffness parameter of the constraint system, and realizing the primary individual evaluation of the characteristics of the constraint system; approximation of Structure A also Using multiple regressionrFunctional relationship Q with stiffness parameter of constraint system；
Selecting all stiffness parameters k of the constraint system because the stiffness parameters of the constraint system are less1、k2、GL、D2Constructing a multiple quadratic regression model, and respectively using the four parameters as y for convenient description1、y2、y3、y4Four variables are expressed, and the corresponding dependent variable is ArThe expression of the multivariate quadratic regression model is as follows:
wherein b is0Is a constant term, b1、b2、b3、b4Is a coefficient of a first order term, b(1，1)、b(1，2)......b(4，4)Is a quadratic coefficient; rejecting low-impact items by regression analysis, where parameter D2Is completely removed, and remains 7 items with large influence on the regression model, wherein the items are respectively k2、k1 2、k2 2、GL 2、k1k2、k1GL、k2GL；
By comparing A of stiffness of different restraint systemsrThe size can realize the evaluation of the rigidity of the constraint system, so as to make ArDimensionless and AvChemotaxis, min-max standardization method, for ArThe standardized processing is carried out to obtain the evaluation index of the dimensionless constraint system characteristic, the evaluation index is defined as a comprehensive evaluation index of the constraint system and is expressed by a symbol beta, and the calculation method comprises the following steps:
determining A from occupant response surfacerA maximum value of 69.12g and a minimum value of 44.60 g; from equations (10) and (11), β is calculated as:
beta is distributed between 0 and 1, and the smaller the value is, the better the corresponding rigidity of the restraint system is from the viewpoint of the acceleration of the passengers; however, situations where β is greater than 1 or less than 0 may occur when the constraint system stiffness parameter is outside the usual range.
7. The method for evaluating the coupling relationship between the collision waveform and the characteristics of the restraint system according to claim 1, wherein the collision waveform and the characteristics of the restraint system are evaluated on the basis of αoThe establishment of (A) means:
establishing occupant acceleration response aocAnd direct quantitative relation between the comprehensive collision waveform evaluation index a and the comprehensive restraint system evaluation index beta, so that integral coupling relation evaluation is realized according to the initial independent evaluation results of the collision waveform and the characteristics of the restraint system, and alpha and beta are respectively expressed by AvAnd ArIs obtained by a standardized process, soocAnd AvAnd ArMay be equivalent to aocAnd an increasing functional relationship R between α and β; the occupant response surface can be drawn according to the corresponding relation of alpha and beta to form alpha-beta-aocThe response surface is replaced by the grid for convenient observation, and the whole curved surface presents a good incremental trend;
approximate construction a by adopting curved surface fitting methodocAnd an increasing functional relationship R between alpha and beta, with alpha and beta as arguments, for alpha-beta-aocThe response surface is fitted with a quadratic surface as shown in equation (13), where c0、c1、c2、c3、c4、c5Obtaining coefficient values of each item through a least square method for each item of the coefficient;
aoc＝c0+c1α+c2β+c3α2+c4αβ+c5β2 (13)
since the coefficients of the squared terms of α and β are close to 0, the surface fitting equation can be simplified as:
aoc＝280.5+335.1α+161.8β+168αβ (14)
coefficient of determination R of fitting result2The fitting precision is high and reaches 0.986.
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| CN108647464B (en) * | 2018-05-18 | 2019-08-09 | 吉林大学 | The design method of conceptual phase restraint system |
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| CN109596365A (en) * | 2018-12-27 | 2019-04-09 | 重庆长安汽车股份有限公司 | A kind of sled test method for simulating offset collision |
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