A three-dimensional dimension chain calculation method based on one-dimensional dimension chain algorithm

Abstract

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

[0001] The invention belongs to the technical field of automobile precision design, and relates to a three-dimensional dimension chain calculation method, and specifically to a three-dimensional dimension chain calculation method based on a one-dimensional dimension chain algorithm. Background Art

[0002] In the structure of a part or a machine, there are always some interrelated dimensions. These interrelated dimensions are connected in a certain order to form a closed dimension group, which is called a dimension chain. The dimension chain consists of closed loops and component loops: the closed loop is the dimension naturally formed after assembly, and is also the target dimension required by the dimension chain calculation; other dimensions are called component loops, and their changes will affect the closed loop.

[0003] In the actual production and manufacturing process of automotive parts, it is difficult to produce perfect parts. The actual manufactured parts often deviate from the ideal design (manufacturing tolerance), and the parts will also have positioning deviations (assembly tolerances) during the assembly process. These deviations continue to accumulate during the assembly process and eventually accumulate into product dimensional deviations.

[0004] Automobiles are usually composed of 14,000 to 20,000 parts. Due to the complexity of automobile products, assembly dimension chains are mostly spatial, not unidirectional. Therefore, during the vehicle model development stage, the component loops and closed loops of the target dimension chain that need to be analyzed are often not in a single direction. This requires the introduction of three-dimensional dimension chain calculation.

[0005] For the calculation of three-dimensional dimension chain, most OEMs in the automotive industry will use computer software such as 3DCS and VSA for analysis. However, firstly, it is a prerequisite that a digital model must be available, and secondly, the modeling time is long and the workload is large (vehicle-level modeling is often required), and it is impossible to quickly obtain the calculation results of a specific dimension chain.

[0006] In the early stage of a vehicle project (where there is a styling CAS surface but no 3D data for components), existing technology can only calculate a one-dimensional dimension chain; if this algorithm is used to calculate a three-dimensional dimension chain, it can only be approximated and the result is not accurate. Summary of the invention

[0007] In order to solve the above problems existing in the prior art, the present invention provides a three-dimensional dimension chain calculation method based on a one-dimensional dimension chain algorithm, which can quickly and relatively accurately calculate the three-dimensional dimension chain during the vehicle model project development stage.

[0008] The objective of the present invention is achieved through the following technical solutions:

[0009] A three-dimensional dimension chain calculation method based on a one-dimensional dimension chain algorithm comprises the following steps:

[0010] Step 1: Clarify the directions of the target dimension chain: clarify the directions of the component loops and closed loops of the target dimension chain, and approximately integrate these direction vectors to obtain several groups of direction vectors related to the calculation of the target dimension chain;

[0011] Step 2: Calculate the dimension chain in each direction separately;

[0012] Step 3, calculate the influence coefficient of each direction mentioned above respectively;

[0013] Step 4: Substitute the influence coefficient to obtain the calculation result of the target dimension chain.

[0014] Furthermore, the step 2 includes the following process:

[0015] 2.1) Chain link sorting: When calculating the dimension chain in a certain direction, assume that the target dimension chain is also in that direction; sort out the assembly relationship related to that direction according to the calculation method of the one-dimensional dimension chain, and list the related chain links in order;

[0016] 2.2) Chain link tolerance assignment: If a chain link is consistent with the calculation direction, the tolerance value is assigned normally; if a chain link is in other calculation directions, the tolerance value of the chain link is assigned to 0;

[0017] 2.3) Except for the target dimension chain direction, the dimension chain in each direction should be a complete closed loop.

[0018] Furthermore, the influence coefficient calculation in step 3 adopts the vector dot product method:

[0019] Suppose there are two vectors in three-dimensional space and Define their dot product as the following real number:

[0020]

[0021] Assume the angle between the two vectors is θ, have:

[0022]

[0023] make are all unit vectors, that is, Substituting into the above two equations, we have:

[0024] cosθ=x1x2+y1y2+z1z2 (1)

[0025] Formula (1) is the calculation formula for the influence coefficient of a certain direction on the target dimension chain;

[0026] Assume that the unit direction vectors of n directions except the target direction in step 1 are The angles between them and the target direction are θ1, θ2, θ3, ..., θ n ; Let the unit direction vector of the target direction be

[0027] The influence coefficients of each direction on the target direction are μ1, μ2, μ3, ..., μ n That is:

[0028]

[0029]

[0030]

[0031] …

[0032]

[0033] Among them, μ n is a real number, and μ n ∈[0, 1].

[0034] Furthermore, in step 3, the unit direction vector of the target direction is It is measured in CATIA: any of the two cooperating counterparts involved in the target dimension chain is translated 1mm along the target direction, and the three-coordinate change values ​​Δx, Δy, Δz of any point on the part are measured, in mm, that is:

[0035]

[0036] To test it, we know from the Pythagorean theorem that the following relationship should be satisfied:

[0037] (Δx) 2 +(Δy) 2 +(Δz) 2 =1

[0038] Furthermore, in the step 4, the calculation result of the dimension chain in a certain direction is assumed to be ±δ1; it is multiplied by the influence coefficient μ1 of the direction, and the result ±δ1·μ1 is substituted into the chain link of the corresponding direction in the target dimension chain; the same is true for the other directions, and they are substituted into the corresponding chain links respectively; the final calculation result is the calculated value of the target dimension chain.

[0039] The present invention has the following beneficial effects:

[0040] The method of the present invention breaks through the limitation that three-dimensional dimension chain analysis must have a digital model, which is convenient for early verification and evaluation;

[0041] The method of the present invention is very simple to calculate and can ensure accuracy, which is suitable for beginners of dimensioning and avoids the complicated modeling process of software three-dimensional analysis;

[0042] The method of the present invention is more accurate in calculating the three-dimensional dimension chain than the simple one-dimensional dimension chain approximation algorithm;

[0043] The method of the invention has universal applicability and can be used to calculate three-dimensional dimension chains in various situations. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 The present invention is a flowchart of a three-dimensional dimension chain calculation method based on a one-dimensional dimension chain algorithm according to an embodiment of the present invention. DETAILED DESCRIPTION

[0045] The technical solution of the present invention is further described below in conjunction with embodiments:

[0046] Example

[0047] like Figure 1 As shown, a three-dimensional dimension chain calculation method based on a one-dimensional dimension chain algorithm includes the following steps:

[0048] Step 1: Clarify the directions of each component loop and closed loop of the target dimension chain:

[0049] Similar to the calculation of one-dimensional dimension chain, the first step of three-dimensional dimension chain is to clarify the assembly relationship of parts related to the target dimension chain and sort out the dimension chain rings; different from the calculation of one-dimensional dimension chain, the direction of the chain ring tolerance that affects the result of the target dimension chain may be in the X / Y / Z direction or in some other specific direction. Therefore, the first step is to clarify the direction of the component rings and closed rings of the target dimension chain, and to approximate the integration of these direction vectors to obtain several groups of direction vectors related to the calculation of the target dimension chain.

[0050] Step 2: Calculate the dimension chains of the above-mentioned component rings and closed rings separately:

[0051] 2.1) Chain link sorting: When calculating the dimension chain in a certain direction, assume that the target dimension chain is also in that direction; sort out the assembly relationship related to that direction according to the idea of ​​ordinary one-dimensional dimension chain, and list the chain links related to it in order. This embodiment gives an example of calculating the dimension chain in the X direction, as shown in Table 2.

[0052] 2.2) Link tolerance assignment: If a link is consistent with the calculation direction, the tolerance value is assigned normally; if a link is in another calculation direction (such as the link with remarks in the last column of Table 1), the tolerance value of the link is assigned to 0.

[0053] 2.3) For ease of reading and inspection, the dimension chain in each direction except the target dimension chain direction should be a complete closed loop.

[0054] Table 1 Calculation diagram of dimension chain in X direction

[0055]

[0056] The dimension chain in the target dimension chain direction also needs to be a complete closed loop, but the intermediate links should reflect the calculation results of the directions of the above-mentioned component loops and closed loops, as shown in Table 2. However, the tolerance assignment of these links is not a direct substitution of the calculation results of the dimension chain in each direction except the target direction, but needs to be multiplied by the influence coefficient of each direction.

[0057] Table 2 Calculation diagram of target direction dimension chain

[0058]

[0059] Step 3: Calculate the influence coefficients of the directions of the above-mentioned component rings and closed rings respectively

[0060] The meaning of the influence coefficient is: the contribution rate of the tolerance in a certain direction to the target dimension chain result. Its geometric meaning is the cosine value of the angle between the direction and the target dimension chain direction (set as θ), cosθ∈[0,1]. For example, when the direction is perpendicular to the target dimension chain direction, cos90°=0, that is, the contribution rate of the direction to the target dimension chain is 0%.

[0061] The influence coefficient can be calculated using the vector dot product method:

[0062] Suppose there are two vectors in three-dimensional space and Define their dot product as the following real number:

[0063]

[0064] Assume the angle between the two vectors is θ, have:

[0065]

[0066] make are all unit vectors, that is, Substituting into the above two equations, we have:

[0067] cosθ=x1x2+y1y2+z1z2 (1)

[0068] Formula (1) is the calculation formula for the influence coefficient of a certain direction on the target dimension chain in this calculation method.

[0069] Assume that the unit direction vectors of n directions except the target direction in step 1 are The angles between them and the target direction are θ1, θ2, θ3, ..., θ n; Let the unit direction vector of the target direction be It can be measured in CATIA. There are many measurement methods. Here is a method: translate any of the two cooperating counterparts involved in the target dimension chain by 1 mm along the target direction, and measure the three-coordinate change values ​​Δx, Δy, Δz (unit: mm) of any point on the part, that is,

[0070]

[0071] To test it, we know from the Pythagorean theorem that the following relationship should be satisfied:

[0072] (Δx) 2 +(Δy) 2 +(Δz) 2 =1

[0073] The influence coefficients of each direction on the target direction are μ1, μ2, μ3, ..., μ n That is:

[0074]

[0075]

[0076]

[0077] …

[0078]

[0079] Among them, μ n is a real number, and μ n ∈[0, 1].

[0080] Step 4: Substitute the influence coefficient to obtain the target dimension chain calculation result:

[0081] Taking the dimension chain in the first direction as an example, assume that the calculated result is ±δ1; now it needs to be multiplied by the influence coefficient μ1 in this direction, and the result (±δ1·μ1) is substituted into the chain link in the corresponding direction in the target dimension chain.

[0082] The same goes for the other directions, and the corresponding chain links are substituted in. The final calculation result is the calculated value of the target dimension chain.

Claims

1. A three-dimensional dimension chain calculation method based on a one-dimensional dimension chain algorithm, characterized in that: The following steps are involved: Step 1: Clarify the directions of the target dimension chain: clarify the directions of the component loops and closed loops of the target dimension chain, and approximately integrate these direction vectors to obtain several groups of direction vectors related to the calculation of the target dimension chain; Step 2: Calculate the dimension chain in each direction separately; Step 2 The process includes: 2.1) Chain link combing: When calculating the dimension chain in a certain direction, it is assumed that the target dimension chain is also in that direction; According to the calculation method of one-dimensional dimension chain, sort out the assembly relationship related to this direction, and list the chain links related to it in order; 2.2) Chain link tolerance assignment: If a chain link is consistent with the calculation direction, the tolerance value is assigned normally; if a chain link is in other calculation directions, the tolerance value of the chain link is assigned to 0; 2.3) Except for the target dimension chain direction, the dimension chain in each direction should be a complete closed loop; Step 3: Calculate the influence coefficient of each direction respectively; the influence coefficient calculation adopts the vector dot product method: Suppose there are two vectors in three-dimensional space and Define their dot product as the following real number: Assume the angle between the two vectors is θ, have: make are all unit vectors, that is, Substituting into the above two equations, we have: cosθ=x1x2+y1y2+z1z2 (1) Formula (1) is the calculation formula for the influence coefficient of a certain direction on the target dimension chain; Assume that the unit direction vectors of n directions except the target direction in step 1 are The angles between them and the target direction are θ1, θ2, θ3, ..., θ n ; Let the unit direction vector of the target direction be The unit direction vector of the target direction is It is measured in CATIA: any of the two cooperating counterparts involved in the target dimension chain is translated 1mm along the target direction, and the three-coordinate change values ​​Δx, Δy, Δz of any point on the part are measured, in mm, that is: To test it, we know from the Pythagorean theorem that the following relationship should be satisfied: (Δx) 2 +(Δy) 2 +(Δz) 2 =1 The influence coefficients of each direction on the target direction are μ1, μ2, μ3, ..., μ n That is: …… Among them, μ n is a real number, and μ n ∈[0, 1]; Step 4: Substitute the influence coefficient to obtain the target dimension chain calculation result: Assume that the calculation result of the dimension chain in a certain direction is ±δ1; multiply it by the influence coefficient μ1 of this direction, and substitute the result ±δ1·μ1 into the chain link of the corresponding direction in the target dimension chain; the same is true for the other directions, and substitute them into the corresponding chain links respectively; the final calculation result is the calculated value of the target dimension chain.

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