Disclosure of Invention
The invention provides a method for checking arrangement of a driving shaft of a passenger vehicle based on a Matlab program, which has better calculation accuracy and can effectively improve the arrangement and checking efficiency of the driving shaft, and aims to solve the problem of low working efficiency caused by the fact that great energy is consumed to carry out arrangement and checking on the driving shaft and the calculation of the shaft length of the driving shaft in the process of arranging a power assembly of the passenger vehicle with a front driving shaft in the prior art.
In order to achieve the purpose, the invention adopts the following technical scheme:
a passenger vehicle driving shaft arrangement checking method based on a Matlab program comprises the following steps:
s1, establishing a mathematical model of the limit values of the inner node displacement and the inner node rotation angle, and obtaining the value range of the length L of the driving shaft;
s2, establishing a mathematical model of the limit value of the outer joint rotation angle, and correcting the value range of the length L of the driving shaft obtained in the step S1 according to the obtained limit value range of the included angle between the outer joint axis and the shaft rod;
s3, establishing a mathematical model of the offset condition of the contact point displacement of the inner joint bearing, and correcting the value-taking range of the length L of the driving shaft obtained in the step S2 according to the limit value range of the contact point displacement of the bearing;
s4, selecting the optimal solution of the driving shaft length L according to the result of the step S3.
Preferably, step S1 includes the steps of:
establishing a coordinate system, wherein the abscissa is displacement, the ordinate is an inner pitch angle, the displacement is sequentially connected into straight lines according to known points 1, 2, 3, 4 and 5 provided by a supplier to form a limit value mathematical model, and linear equations of the straight lines L1, L2 and L3 are solved through the coordinates of the known points; the straight lines L1, L2 and L3 are obtained according to design experience;
setting a theoretical inner node of a left driving shaft as O1, an actual inner node of the driving shaft as Ot, an outer node of the driving shaft as Mli and any point on the outer node of the driving shaft as Mlo;
setting the axial length of a driving shaft, namely the distance between Mli and Ot as L, making an MliH perpendicular O1Ot extension line passing through Mli and at a point H, setting an angle MliOtH as theta, O1Ot as t, namely an inner node rotation angle position theta, and setting the displacement of an inner node as t;
according to the known coordinates of O1Ot and Y axis in the space coordinate system in parallel and the coordinates of O1(x1, y1, z1), Mli (xi, yi, zi) and Mlo (xo, yo, zo), the coordinates of the H point are (x1, yi, z1) according to the space geometrical relation, and the parametric equation of t and theta is solved:
let the equation of the straight line L be: theta is equal to kt + b,
substituting equations (1) and (2) into the equation of line L yields the following equation:
Wherein f (L) represents a series of straight line groups that are parallel to the model boundary straight lines; l obtained when f (L) is 0 is a boundary point.
Preferably, step S1 further includes the steps of:
derivation of f (l) yields:
when k < 0, F' (L) < 0, F (L) is a decreasing function; if the root of f (L) ═ 0 is Lx3, substituting the coordinates (t, theta) corresponding to all the points on the left side of the straight line L3 into f (L), wherein f (L) < 0, and obtaining the value range of L which is L > Lx 3;
when k is more than 0, because theta is less than 30 degrees, k is more than 0.1 and L is more than 300 in the actual engineering, the method obtains
I.e. F' (L) > 0, to obtain F (L) as an increasing function; if the calculated roots of f (L) ═ 0 are Lxb1 and Lxb2 by substituting k and b in the equations of the straight lines L1 and L2, respectively, the coordinates (t, θ) corresponding to all points on the right side of the straight lines L1 and L2 are substituted into f (L), and if f (L) < 0, the value range of L is L < min (Lxb1, lxb 2);
finally, the value range of the obtained L is Lx3 < L < min (Lxb1, lxb 2).
Preferably, step S2 includes the steps of:
the pivot angle of the outer section of the driving shaft is set to be phi, and phi is less than phi0Said psi0To allow for the pendulum angle, the coordinates of Ot from step S1 are (x1, y1-t, z1), and the vector angle ψ is found from the space vectors MliMlo and OtMli:
conversion according to formula (3) gives:
wherein, in the formula (3), the | OtMli | is L; the value range of L is obtained by using an inequality (4).
Preferably, step S3 includes the steps of:
angular conversion displacement tθTan (θ) × λ/2, λ being a conversion coefficient determined by the inner node structure of the drive shaft;
the geometric relationship of the inner joint structure of the driving shaft is as follows:
when the angular conversion displacement is larger than 0, the bearing contact point displacement tz=t+tθ;
When the angular conversion displacement is less than 0, the bearing contact point displacement tz=t-tθ;
If the design requirement tzShould be at tmAnd tnIn between, let tz>tmAnd t isz<tn;
According to design requirements tzAnd selecting the value range of the L meeting the requirement.
Preferably, the straight lines L1, L2 and L3 in step S1 form a safety boundary, and the point coordinates (t, θ) of the inner node of the driving shaft during the slippage process of each working condition are within the safety boundary.
Preferably, the driving shaft outer pitch pivot angle psi is an included angle between an outer pitch axis and a driving shaft lever axis, and the allowable working pivot angle psi0Is 50 deg.
Preferably, the bearing contact point displacement tzThe displacement t converted from the inner joint displacement t and the inner joint rotation angleθIs calculated to obtain tzThe value range of (A) is from-20 mm to +20 mm.
Compared with the prior art, the invention has the beneficial effects that: the checking method of the invention establishes three mathematical models according to the space motion rule of the driving shaft: the mathematical model of inner node displacement and inner pitch corner, the mathematical model of outer pitch corner and the mathematical model of bearing contact point displacement to according to above mathematical model can be through the coordinate of some points in the known three-dimensional data, the value range of once only calculating the driving shaft length accurately, compare in traditional check-up process, work efficiency improves and is showing, at the in-process of whole car modularized design, has more obvious advantage and meaning.
Detailed Description
In order to more clearly illustrate the embodiments of the present invention, the following description will explain the embodiments of the present invention with reference to the accompanying drawings. It is obvious that the drawings in the following description are only some examples of the invention, and that for a person skilled in the art, other drawings and embodiments can be derived from them without inventive effort.
Example 1:
a passenger vehicle driving shaft arrangement checking method based on a Matlab program comprises the following steps:
s1, establishing a mathematical model of the limit values of the inner node displacement and the inner node rotation angle, and obtaining the value range of the length L of the driving shaft;
s2, establishing a mathematical model of the limit value of the outer joint rotation angle, and correcting the value range of the length L of the driving shaft obtained in the step S1 according to the obtained limit value range of the included angle between the outer joint axis and the shaft rod;
s3, establishing a mathematical model of the offset condition of the contact point displacement of the inner joint bearing, and correcting the value-taking range of the length L of the driving shaft obtained in the step S2 according to the limit value range of the contact point displacement of the bearing;
s4, selecting the optimal solution of the driving shaft length L according to the result of the step S3.
Further, step S1 includes the following steps:
as shown in fig. 1, a coordinate system is established, the abscissa is displacement, the ordinate is inner pitch angle, the displacement is sequentially connected into straight lines according to known points 1, 2, 3, 4 and 5 provided by a supplier to form a limit value mathematical model, and the linear equations of the straight lines L1, L2 and L3 are obtained through the coordinates of the known points; the straight lines L1, L2 and L3 are obtained according to design experience;
the limit boundary is a set of (t, theta) coordinates that can meet the technical requirements, and is generally provided by a supplier; the straight lines L1, L2 and L3 form a safety boundary, the safety boundary is generally obtained by offsetting a limit boundary by a certain safety amount, and point coordinates (t, theta) of the inner joint of the driving shaft in the sliding process of each working condition are all in the safety boundary.
Further, as shown in fig. 3, a theoretical inner node of the left driving shaft is O1, an actual inner node of the driving shaft is Ot, an outer node of the driving shaft is Mli, and any point on the outer node of the driving shaft (an end point of the outer node in fig. 4) is Mlo;
setting the axial length of a driving shaft, namely the distance between Mli and Ot as L, making an MliH perpendicular O1Ot extension line passing through Mli and at a point H, setting an angle MliOtH as theta, O1Ot as t, namely an inner node rotation angle position theta, and setting the displacement of an inner node as t;
according to the known coordinates of O1Ot and Y axis in the space coordinate system in parallel and the coordinates of O1(x1, y1, z1), Mli (xi, yi, zi) and Mlo (xo, yo, zo), the coordinates of the H point are (x1, yi, z1) according to the space geometrical relation, and the parametric equation of t and theta is solved:
let the equation of the straight line L be: theta is equal to kt + b,
substituting equations (1) and (2) into the equation of line L yields the following equation:
Wherein f (L) represents a series of straight line groups that are parallel to the model boundary straight lines; l obtained when f (L) is 0 is a boundary point.
Further, step S1 includes the following steps:
derivation of f (l) yields:
when k is less than 0 (corresponding to the equation L3), F' (L) < 0, F (L) is a decreasing function; if the root of f (L) ═ 0 is Lx3, substituting the coordinates (t, theta) corresponding to all the points on the left side of the straight line L3 into f (L), wherein f (L) < 0, and obtaining the value range of L which is L > Lx 3;
when k is greater than 0 (corresponding to the linear equations L1 and L2), since theta is less than 30 degrees in engineering practice, k is greater than 0.1, and L is greater than 300, the method is obtained
I.e. F' (L) > 0, to obtain F (L) as an increasing function; if the roots obtained by substituting k and b in the equations of the straight lines L1 and L2 into f (L) ═ 0 are Lxb1 and Lxb2, respectively, the coordinates (t, θ) corresponding to all points on the right side of the straight lines L1 and L2 are substituted into f (L), and if f (L) < 0, the roots obtained from L are substituted into f (L) < 0, and the roots obtained from L are substituted into LThe value range is L < min (Lxb1, lxb 2);
finally, the value range of the obtained L is Lx3 < L < min (Lxb1, lxb2)
Further, as shown in fig. 2, step S2 includes the following steps:
the pivot angle of the outer section of the driving shaft is set to be phi, and phi is less than phi0Said psi0To allow for the pendulum angle, the coordinates of Ot from step S1 are (x1, y1-t, z1), and the vector angle ψ is found from the space vectors MliMlo and OtMli:
conversion according to formula (3) gives:
wherein, in the formula (3), the | OtMli | is L; the value range of L is obtained by using an inequality (4).
The driving shaft outer pitch pivot angle psi is a included angle between an outer pitch axis and a driving shaft lever axis, and the outer pitch pivot angle psi is smaller than an allowable working pivot angle psi0Said allowable working pivot angle psi0Is generally taken to be about 50 ° or 50 °. In FIG. 2, the abscissa represents the wheel center oscillation position corresponding to the outer section of the driving shaft, and the ordinate represents the pivot angle psi under the corresponding operating conditioniAll psiiShould be at psi0Below the line.
Further, step S3 includes the following steps:
angular conversion displacement tθTan (θ) × λ/2, λ being a conversion coefficient determined by the inner node structure of the drive shaft;
the geometric relationship of the inner joint structure of the driving shaft is as follows:
when the angular conversion displacement is larger than 0, the bearing contact point displacement tz=t+tθ;
When the angular conversion displacement is less than 0, the bearing contact point displacement tz=t-tθ;
If the design requirement tzShould be at tmAnd tnIn between, let tz>tmAnd t isz<tn;
According to design requirements tzAnd selecting the value range of the L meeting the requirement.
The bearing contact point displacement tzThe displacement t converted from the inner joint displacement t and the inner joint rotation angleθIs calculated to obtain tzThe value range of (A) is-20 mm to +20mm, and the specific requirements are given by suppliers.
And according to the system modeling, analysis and optimization objective function, optimizing the drive shaft design by adopting an MATLAB/GUI function and an optimization function in an optimization tool box. MATLAB is very powerful to matrix data processing ability, and GUI is one kind in MATALB and establishes the graphical user interface, can utilize its own controlling part, realizes the visualization of drive shaft design process through the language c, has good human-computer interaction function.
The invention utilizes the GUI function and the optimization tool box of MATLAB to establish a drive shaft axial length fixed parameter optimization design program, and the main interface is shown in figure 4. The position of the outer node is determined along with wheel jump, coordinates of the outer node are generated to excel by three-dimensional software at one time and then are imported into design software, namely, the value range of the left driving shaft and the right driving shaft can be output, a user can select any solution in the value range, and the software calculates according to the solution and outputs the solution to a model corresponding to the excel to form a judgment image.
And (4) realizing a corresponding solving strategy through software according to the mathematical modeling of the driving shaft length optimization design.
Solving strategies of the mathematical models of the inner node displacement and the inner node rotation angle:
coordinates of Mli (xi, yi, zi) and Mlo (xo, yo, zo) of characteristic positions are generated in a cata suspension motion DMU model, corresponding t and theta matrixes can be obtained by substituting equations (1) and (2) into which coordinate matrixes are substituted, a matrix of a solution of L can be obtained by substituting data in the matrixes into three linear equations f (L) and 0, and a solution of L is obtained as [ Lx3] < L < min ([ Lxb1], [ lxb2 ]).
Solving strategy of the mathematical model of the outer joint rotation angle:
as known from design experience, the allowable conditions of the outer pitch angle are easy to realize, so that the value range of L calculated by solving an equation is very large, the final value is not significant, and a strategy of a trial-and-error method is adopted in calculation: and (3) in the mathematical model of the inner node displacement and the inner node rotation angle, taking an integer in the value range of the solved L to test the value, and taking out the value meeting the inequality (4) to obtain the inequality solution meeting the requirement.
Solving strategy of the mathematical model of the contact point displacement of the inner joint bearing:
in the solving process of the mathematical model of the contact point displacement of the inner bearing, a trial value method is needed to solve, and the trial value strategy is the same as the solving strategy of the mathematical model of the outer joint rotation angle.
The trial value process of the mathematical model of the outer joint corner and the mathematical model of the contact point displacement of the inner joint bearing is easy to realize in computer calculation, so the trial value range can be properly enlarged, and the condition of no solution can be solved for satisfying the safety solution of the mathematical model of the limit value inner joint displacement and the inner joint corner due to the solution of the L in the mathematical model of the inner joint displacement and the inner joint corner, and the safety value can be chosen according to the actual engineering relaxation.
The specific operation steps of the MATLAB software program are as follows:
step 1, filling input conditions required by drive shaft design into an EXCEL template, wherein the EXCEL template comprises the following contents:
a, the theoretical inner node space coordinate of the driving shaft, as shown in Table 1, is defined as left side O1 and right side O2;
b, in the suspension motion process, the rack stroke and the tire jumping stroke of the steering gear under each typical working condition, the corresponding coordinates of the node center point Mli of the outer joint of the left driving shaft and any point Mlo on the axis of the outer joint are shown in tables 2 and 3, and the spatial motion position of the table 2 and the coordinates of the relevant points of the outer joint of the table 3 are in one-to-one correspondence;
c, driving shaft inner pitch slip curve boundary points, as shown in Table 4, wherein safety variables are filled in according to design experience values;
d, driving shaft outer section allowable working swing angle limit value, as shown in table 5;
e, coefficients of the driving shaft angle conversion displacement formula, as shown in Table 6
TABLE 1
TABLE 2
Time of exercise
|
Steering (rack stroke)
|
Jumping (wheel jumping stroke)
|
20
|
|
|
30
|
|
|
……
|
|
|
120
|
|
|
130
|
|
|
……
|
|
|
230
|
|
|
……
|
|
|
TABLE 3
TABLE 4
TABLE 5
TABLE 6
Wherein, table 1 is determined by the overall arrangement speciality of the whole vehicle, tables 2 and 3 are input conditions of the speciality of the chassis before the arrangement of the engine room, and the information in tables 4, 5 and 6 is determined by the self-attribute of the driving shaft and is generally provided by a supplier.
Step 2, importing the template information into a driving shaft design and analysis system, wherein the importing process is an import file module for running a program, the program automatically reads all information in the template, and the processing and calculation are carried out, and the process is as follows:
s21, reading the A, D, E information in the step 1, and checking the information with a theoretical range, if the information does not meet the requirement, suspending operation and reporting an error;
s22, reading A, B information in step 1: the coordinates of the outer node center and the point on the outer node axis are in one-to-one correspondence with the typical working conditions of suspension motion, the working conditions are numbered in the template, and the program correspondingly stores the serial numbers and the coordinates into fixed arrays in the data processing process. In the process of storage, the program judges invalid data, and the array finally used for calculation eliminates the invalid data. And the space coordinates of the right driving shaft under each working condition are obtained by utilizing the characteristic that the positions of the left outer joint and the right outer joint of the driving shaft are symmetrical.
S23, defining an inner joint rotation angle a, an inner joint displacement t and a driving shaft axial length L, setting a vertical line to a straight line O1Ot through O1, setting a foot to be H, setting an inner node to be Ot in the actual motion process of the driving shaft, and solving a parameter equation of a and t relative to L through a space triangle formed by space points Mli, O1 and H and Mli, Ot and H.
S24, reading the information in the step C to find out the limit range of the inner joint slip curve, wherein the range consists of three straight lines, and the equations of the three straight lines can be expressed by a and t;
and S25, combining the parameter equation in the step S23 and the linear equation set in the step S24 to form three equation sets related to L, finding a set of L values of L in the limit range of the slip curve through monotonicity judgment of a function related to the L equation, and defining the set as S.
S26, adding 20 to the maximum value of L in the set S, subtracting 20 from the minimum value to form a set Sa, obtaining an expression of the outer pitch swing angle relative to L through a linear vector formed by Mli and Mlo and a linear vector formed by Ot and Mli, substituting the set S1 into the expression to obtain a swing angle set N corresponding to the set Sa, comparing the set N with allowable swing angles, and excluding all L corresponding to the swing angles which do not meet the requirements, so that the rest parts in the set Sa are L sets meeting the requirements of the allowable working swing angles of the driving shaft, and the set is defined as S1.
S27, the bearing contact point displacement z is converted to an expression for L, and the relationship between z and L is provided by the drive spindle supplier, and is generally the relationship shown in table 6. Substituting the data in the Sa into the expression to obtain a set Z of the pivot angle corresponding to the set Sa, comparing the set Z with the allowable bearing contact point displacement, and excluding all L corresponding to the displacement which does not meet the requirement, so that the rest part in the set Z is the set L meeting the allowable working pivot angle requirement of the driving shaft, and the set is defined as S2.
And S28, respectively outputting the sets S, S1 and S2, wherein the intersection of the sets is a set of the axial length of the driving shaft, and the set is a feasible scheme in design. Repeating the above steps can also find a feasible solution for the right drive shaft. During the output of S1 and S2, the computational analysis system will make decisions on two sets: if the result of S1 is that the set is empty, it is indicated that the L value does not meet the requirement of the swing angle of the outer joint, the system calculates the corresponding working swing angle output as the reference by the self-output reference value, namely the maximum value and the minimum value of the extension range of the set S (the maximum value and the minimum value in the set are extended by 8 units); if the result of S2 is finally judged to be an empty set, which indicates that the L value of the bearing contact point displacement requirement is not met, the system calculates the corresponding bearing contact point displacement output as the reference by the self-output reference value, namely the maximum value and the minimum value of the extension range (extending the maximum value and the minimum value in the set by 8 units) of the set S.
And S29, respectively storing working condition numbers, inner joint rotation angles, outer joint swing angles and bearing contact point displacement numbers corresponding to Sa, wherein the three numbers are defined as A, T, Zt.
And 3, filling the inner joint rotation angle, the outer joint swing angle and the bearing contact displacement corresponding to the selected driving shaft length scheme into a template, observing the position of the corresponding characteristic curve in the check model, and outputting a plurality of groups of images corresponding to L for comparison to find an optimal solution. The specific process is as follows:
s31, finding a reasonable L value through the set S, S1 and the set S2, inputting the value into a driving shaft design and analysis system, addressing the position of L in A, T, Zt by the system, sequentially outputting the numerical values of L in A, T, Zt corresponding to each working condition to corresponding positions in a corresponding EXCEL template, completing the process by a writing algorithm of MATLAB to EXCEL, and finally automatically displaying a characteristic curve in the EXCEL;
and S32, if the characteristic curve displayed above is not the optimal solution, respectively inputting the L of the multiple feasible schemes into the system, outputting the sheet in the EXCEL after the system processes, and comparing the sheet images corresponding to the L to find the optimal solution, namely the final scheme of the driving shaft length.
Taking the driving shaft parameters of the H7 four-wheel drive vehicle as an example, the specific data are as follows:
inner segment slip limiting model
(II) outer joint swing angle requirement
Allowable working swing angle
|
48 |
(III) Angle conversion Displacement requirement
The data obtained by importing the above templates and known condition data into software and solving the data is shown in fig. 5.
According to the result shown in fig. 5, the middle value of the range of the length of the left driving shaft is 450mm, and the characteristic value is output, as shown in fig. 6.
It can be seen from fig. 6 that the bearing contact point displacement is mostly positive, so it is considered to lengthen the drive shaft to 452mm and output a characteristic value, as shown in fig. 7.
Then, according to the result shown in fig. 5, the middle value 361mm of the range of the length of the right driving shaft is selected, and the characteristic value is output, as shown in fig. 8 (when the shaft length is 362mm, the image in the checking model is equivalent to 361mm, which can be judged by the image shift rule).
Finally, according to the result, the shaft length parameters of the four-wheel drive left and right driving shafts are selected to be 452mm and 361mm respectively.
The invention can complete the operation and check of 33 characteristic position working conditions required by the check specification at one time, and input the characteristic data into the check template to form an image. The adopted software program can calculate the value range of the length of the driving shaft, and the sharing of the driving shaft can be realized by taking an intersection in the modularized design, so that the cost of the whole vehicle is reduced; completing the determination time of the axle length parameters of the left front drive shaft and the right front drive shaft of a single vehicle type: the operation time of a designer is only 3 minutes, the operation time of a system background is about 7 minutes when an output file is formed, and compared with the traditional parameter setting process, the design efficiency is greatly improved.
The checking method of the invention establishes three mathematical models according to the space motion rule of the driving shaft: the mathematical model of interior nodal point displacement and interior pitch corner, the mathematical model of outer pitch corner and the mathematical model of bearing contact displacement to can once only calculate the value range of driving shaft length through the coordinate of some points in the known three-dimensional data according to above mathematical model, compare in traditional check process, work efficiency improves and is showing, at the in-process of whole car modularized design, has more obvious advantage and meaning.
The foregoing has outlined rather broadly the preferred embodiments and principles of the present invention and it will be appreciated that those skilled in the art may devise variations of the present invention that are within the spirit and scope of the appended claims.