CN115146378B - Three-dimensional size chain calculation method based on one-dimensional size chain algorithm - Google Patents
Three-dimensional size chain calculation method based on one-dimensional size chain algorithm Download PDFInfo
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Abstract
本发明公开了一种基于一维尺寸链算法的三维尺寸链计算方法，包括以下步骤：明确目标尺寸链的各方向：明确目标尺寸链的组成环、封闭环的方向，并对这些方向向量进行近似整合，得到若干组与目标尺寸链计算相关的方向向量；分别单独计算上述各方向的尺寸链；分别计算上述各方向的影响系数；代入影响系数，得到目标尺寸链计算结果。本发明尤其适用在车型项目开发阶段，快捷而相对准确地计算三维尺寸链。
The present invention discloses a three-dimensional dimension chain calculation method based on a one-dimensional dimension chain algorithm, comprising the following steps: clarifying the directions of the target dimension chain: clarifying the directions of the component loops and closed loops of the target dimension chain, and approximately integrating these direction vectors to obtain several groups of direction vectors related to the target dimension chain calculation; separately calculating the dimension chains in the above directions; separately calculating the influence coefficients of the above directions; substituting the influence coefficients to obtain the target dimension chain calculation results. The present invention is particularly suitable for calculating the three-dimensional dimension chain quickly and relatively accurately in the vehicle model project development stage.
Description
Technical Field
The invention belongs to the technical field of automobile precision design, relates to a three-dimensional size chain calculation method, and in particular relates to a three-dimensional size chain calculation method based on a one-dimensional size chain algorithm.
Background
In the construction of a part or a machine there are always a number of interrelated dimensions which are connected in a sequence into a closed set of dimensions, which form a chain of dimensions. The size chain is composed of a closed ring and a component ring, wherein the closed ring is a size naturally formed after assembly and is also a target size required by size chain calculation, and other sizes are called the component rings, and the change of the size chain can influence the closed ring.
In the actual production and manufacturing process of automobile parts, perfect parts are difficult to manufacture, the actually manufactured parts often deviate from ideal design (manufacturing tolerance), positioning deviation (assembly tolerance) can be generated in the assembly process of the parts, the deviation is accumulated continuously in the assembly process, and finally, the deviation is accumulated into the dimensional deviation of a product.
An automobile is generally composed of 14000-20000 parts. Because of the complexity of automotive products, the assembly size chain is mostly spatial, rather than unidirectional, so that the component loops and closure loops of the target size chain to be analyzed are often not unidirectional during the development stage of the vehicle model. This requires the introduction of calculations of the three-dimensional size chain.
For three-dimensional dimension chain calculation, most of host factories in the automobile industry can analyze the three-dimensional dimension chain by means of computer software such as 3DCS, VSA and the like. However, the precondition is that the modeling time is long and the workload is large (modeling of the whole vehicle level is often needed), and the calculation result of a certain specific-size chain cannot be obtained quickly.
In the current period of the model item (the modeling CAS surface exists and the 3D data of the parts is not available), the prior art can only calculate a one-dimensional size chain, if the algorithm is used for calculating a three-dimensional size chain, only approximate calculation is carried out, and the result is not accurate.
Disclosure of Invention
In order to solve the problems in the prior art, the invention provides a three-dimensional size chain calculation method based on a one-dimensional size chain algorithm, which can calculate a three-dimensional size chain rapidly and relatively accurately in a vehicle model project development stage.
The invention aims at realizing the following technical scheme:
a three-dimensional size chain calculation method based on a one-dimensional size chain algorithm comprises the following steps:
The method comprises the steps of firstly, defining all directions of a target size chain, namely defining directions of a component ring and a closed ring of the target size chain, and approximately integrating the direction vectors to obtain a plurality of groups of direction vectors related to calculation of the target size chain;
Step two, respectively and independently calculating the dimension chains in all directions;
Step three, respectively calculating the influence coefficients of the directions;
and step four, substituting the influence coefficient to obtain a target size chain calculation result.
Further, the second step includes the following steps:
2.1 The chain links are combed, namely, the dimension chain in which direction is calculated, and the target dimension chain is assumed to be the direction, the assembly relation related to the direction is arranged according to the calculation method of the one-dimensional dimension chain, and the chain links related to the direction are listed in sequence;
2.2 Assigning a link tolerance, namely normally assigning a tolerance value if a certain link is consistent with the calculated direction, and assigning 0 if the certain link is in other calculated directions;
2.3 The size chain for each direction should be a complete closed loop except for the target size chain direction.
Further, the third influence coefficient calculation adopts a vector dot product method:
Two vectors are arranged in the three-dimensional space AndThe dot products of them are defined as the following real numbers:
an included angle theta between the two vectors is set, The method comprises the following steps:
Order the Are unit vectors, i.eThe substitution is carried out on the two formulas, namely:
cosθ=x1x2+y1y2+z1z2 (1)
the formula (1) is a calculation formula of a target size chain influence coefficient in a certain direction;
Setting the unit direction vectors of the n directions except the target direction in the first step as respectively The included angles between the target direction and the target direction are respectively theta 1、θ2、θ3、……、θn, and the unit direction vector of the target direction is set as
The influence coefficient mu 1、μ2、μ3、……、μn of each direction in the target direction is:
......
Wherein μ n is a real number and μ n ε [0,1].
Further, in the third step, the unit direction vector of the target direction isThe method is measured in CATIA, wherein any one of two mutually matched opponent pieces related to a target size chain is translated by 1mm along the target direction, and three-coordinate change values delta x, delta y and delta z of any point on the piece are measured, wherein the units are as follows:
it is examined and, as known from the Pythagorean theorem, the following relationship should be satisfied:
(Δx)2+(Δy)2+(Δz)2=1
In the fourth step, the calculation result of the size chain in a certain direction is set to be + -delta 1, the calculation result is multiplied by the direction influence coefficient mu 1, the result + -delta 1·μ1 is substituted into the chain links in the corresponding direction in the target size chain, the other directions are respectively substituted into the corresponding chain links in the same way, and the final calculation result is the calculation value of the target size chain.
The invention has the following beneficial effects:
the method breaks through the limitation that the analysis of the three-dimensional size chain has a digital-analog function, and is convenient for early verification and evaluation;
The method is very simple and convenient to calculate, can ensure accuracy, is suitable for size beginners, and avoids complex modeling process of software three-dimensional analysis;
When the method calculates the three-dimensional size chain, the method is more accurate than a simple one-dimensional size chain approximation algorithm;
the method has universality and can be used for calculating three-dimensional size chains under various conditions.
Drawings
Fig. 1 is a flowchart of a three-dimensional size chain calculation method based on a one-dimensional size chain algorithm according to an embodiment of the present invention.
Detailed Description
The following is a further description of the technical solution of the present invention with reference to examples:
Examples
As shown in fig. 1, a three-dimensional size chain calculation method based on a one-dimensional size chain algorithm includes the following steps:
step one, defining the directions of each component ring and the closed ring of the target size chain:
The first step of the three-dimensional chain is to determine the assembly relation of the parts related to the target chain to finish the chain, similar to the calculation of the one-dimensional chain, and the direction of the chain tolerance affecting the result of the target chain may be the X/Y/Z direction or some other specific direction, unlike the calculation of the one-dimensional chain. Therefore, the first step should determine the directions of the component loops and the closed loops of the target size chain, and approximately integrate the direction vectors to obtain a plurality of groups of direction vectors related to the calculation of the target size chain.
Step two, respectively and independently calculating the dimension chains of the directions of the component rings and the closed rings:
2.1 The chain links are combed, namely, the dimension chain in which direction is calculated, the target dimension chain is assumed to be the direction, the assembly relation related to the direction is arranged according to the thought of the common one-dimensional dimension chain, and the chain links related to the direction are listed in sequence. The present embodiment gives an example in the X-direction dimension chain calculation, as shown in table 2.
2.2 If a link is identical to the calculated direction, normally assigning a tolerance value, and if a link is other calculated direction (such as the last chain with remarks in table 1), assigning a tolerance value of 0.
2.3 For convenient reading and inspection, the size chain in each direction should be a complete closed loop except for the target size chain direction.
TABLE 1 schematic representation of dimension chain calculation in X direction
The size chain in the target size chain direction needs to be a complete closed loop, but the middle chain ring should respectively reflect the calculation results of the directions of the above-mentioned component rings and the closed loop, as shown in table 2. However, the tolerance assignment of these links is not a direct substitution of the calculation result of the dimension chain in each direction except the target direction, but is a multiplication of the influence coefficient in each direction.
TABLE 2 target Direction dimension chain calculation schematic
Step three, respectively calculating the influence coefficients of the directions of the component rings and the closed ring
The influence coefficient means the contribution rate of the tolerance of a certain direction to the target size chain result. The geometric meaning is the cosine value of the included angle (set as theta) between the direction and the target dimension chain direction, cos theta epsilon [0,1]. For example, when the direction is perpendicular to the target size chain direction, cos 90+=0, i.e., the direction contributes 0% to the target size chain.
The influence coefficient can be calculated by using a vector dot product method:
Two vectors are arranged in the three-dimensional space AndThe dot products of them are defined as the following real numbers:
an included angle theta between the two vectors is set, The method comprises the following steps:
Order the Are unit vectors, i.eThe substitution is carried out on the two formulas, namely:
cosθ=x1x2+y1y2+z1z2 (1)
the formula (1) is a calculation formula of the influence coefficient of a certain direction on the target size chain in the calculation method.
Setting the unit direction vectors of the n directions except the target direction in the first step as respectively The included angles between the target direction and the target direction are respectively theta 1、θ2、θ3、……、θn, and the unit direction vector of the target direction is set as The method comprises the steps of translating any one of two matched opponent pieces related by a target size chain along a target direction by 1mm, and measuring three-coordinate change values delta x, delta y and delta z (unit: mm) of any point on the piece, namely:
it is examined and, as known from the Pythagorean theorem, the following relationship should be satisfied:
(Δx)2+(Δy)2+(Δz)2=1
the influence coefficient mu 1、μ2、μ3、……、μn of each direction in the target direction is:
......
Wherein μ n is a real number and μ n ε [0,1].
Substituting the influence coefficient to obtain a target size chain calculation result:
Taking the dimension chain in the first direction as an example, the calculation result is set as +/- 1, the calculation result is multiplied by the direction influence coefficient mu 1, and the result (+ -delta 1·μ1) is substituted into the chain ring in the corresponding direction in the target dimension chain.
The other directions are the same and are respectively substituted into the corresponding links. And the final calculation result is the calculation value of the target size chain.
Claims (1)
1. The three-dimensional size chain calculation method based on the one-dimensional size chain algorithm is characterized by comprising the following steps of:
The method comprises the steps of firstly, defining all directions of a target size chain, namely defining directions of a component ring and a closed ring of the target size chain, and approximately integrating the direction vectors to obtain a plurality of groups of direction vectors related to calculation of the target size chain;
Step two, respectively and independently calculating the dimension chains in all directions, wherein the step two comprises the following processes:
2.1 The chain links are combed, namely, the dimension chain in which direction is calculated, and the target dimension chain is assumed to be the direction, the assembly relation related to the direction is arranged according to the calculation method of the one-dimensional dimension chain, and the chain links related to the direction are listed in sequence;
2.2 Assigning a link tolerance, namely normally assigning a tolerance value if a certain link is consistent with the calculated direction, and assigning 0 if the certain link is in other calculated directions;
2.3 The size chain of each direction should be a complete closed loop except for the target size chain direction;
Calculating influence coefficients of the directions respectively, wherein the influence coefficients are calculated by a vector dot product method:
Two vectors are arranged in the three-dimensional space AndThe dot products of them are defined as the following real numbers:
an included angle theta between the two vectors is set, The method comprises the following steps:
Order the Are unit vectors, i.eThe substitution is carried out on the two formulas, namely:
cosθ=x1x2+y1y2+z1z2 (1)
the formula (1) is a calculation formula of a target size chain influence coefficient in a certain direction;
Setting the unit direction vectors of the n directions except the target direction in the first step as respectively The included angles between the target direction and the target direction are respectively theta 1、θ2、θ3、……、θn, and the unit direction vector of the target direction is set as
The unit direction vector of the target direction isThe method is measured in CATIA, wherein any one of two mutually matched opponent pieces related to a target size chain is translated by 1mm along the target direction, and three-coordinate change values delta x, delta y and delta z of any point on the piece are measured, wherein the units are as follows:
it is examined and, as known from the Pythagorean theorem, the following relationship should be satisfied:
(Δx)2+(Δy)2+(Δz)2=1
the influence coefficient mu 1、μ2、μ3、……、μn of each direction in the target direction is:
......
Wherein μ n is a real number and μ n ε [0,1];
substituting the influence coefficient to obtain a target size chain calculation result:
setting the calculation result of the size chain in a certain direction as +/- 1, multiplying the calculation result by the direction influence coefficient mu 1, substituting the result +/- 1·μ1 into the links in the corresponding direction in the target size chain, substituting the rest directions into the corresponding links respectively, and finally obtaining the calculation result of the target size chain.
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| CN106202742A (en) * | 2016-07-14 | 2016-12-07 | 北京理工大学 | The method and device that a kind of dimensional chain for assembly generates |
| CN108108555A (en) * | 2017-12-19 | 2018-06-01 | 北京理工大学 | A kind of fitted position the chain calculation method, device and equipment |
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| US6826510B2 (en) * | 2002-11-14 | 2004-11-30 | General Electric Company | Method, system and computer product for performing geometric dimension and tolerance stack-up analysis |
| CN114638055B (en) * | 2022-03-31 | 2025-03-14 | 重庆长安新能源汽车科技有限公司 | A method and tool for calculating the contribution of one-dimensional dimensional chain links |
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| CN106202742A (en) * | 2016-07-14 | 2016-12-07 | 北京理工大学 | The method and device that a kind of dimensional chain for assembly generates |
| CN108108555A (en) * | 2017-12-19 | 2018-06-01 | 北京理工大学 | A kind of fitted position the chain calculation method, device and equipment |
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