Comprehensive evaluation method for motor oil cooling system

Abstract

The invention discloses a comprehensive evaluation method for a motor oil cooling system. S1, collecting the temperature of each component in the motor in a natural cooling state; s2, collecting the temperature and flow of each component in the motor in an oil cooling state; s3, defining evaluation indexes; s4, calculating an evaluation value of the motor oil cooling system according to the evaluation index; wherein each component comprises a rotor axial middle large magnetic steel, a rotor axial middle small magnetic steel, a front bearing outer ring, a rear bearing outer ring, a winding front end part and a winding rear end part; the performance of the cooling system is judged according to the calculated evaluation value of the motor oil cooling system, and the method is more convenient.

Description

Technical Field

[0001] The invention relates to the technical field of motor oil cooling, in particular to a comprehensive evaluation method for a motor oil cooling system. Background Art

[0002] Oil cooling is the mainstream cooling method for high-performance motors. However, since the design of the oil cooling system is closely related to the temperature, efficiency and other performance of the motor, it is necessary to quantitatively evaluate the oil cooling system when designing the motor. In the prior art, the motor cooling system is evaluated by the experimental method of embedded thermocouples and shell window openings. The evaluation indicators include local temperature and cooling oil flow state. The evaluation indicators are single and cannot fully reflect the performance of the motor oil cooling system. Summary of the invention

[0003] The purpose of this section is to summarize some aspects of embodiments of the present invention and briefly introduce some preferred embodiments. Some simplifications or omissions may be made in this section and the specification abstract and the invention title of this application to avoid blurring the purpose of this section, the specification abstract and the invention title, and such simplifications or omissions cannot be used to limit the scope of the present invention.

[0004] In view of the above and / or existing problems in the evaluation of the motor oil cooling system in the prior art, the present invention is proposed.

[0005] The technical problem solved by the present invention is that the performance of the motor oil cooling system cannot be fully reflected.

[0006] Therefore, an object of the present invention is to provide a comprehensive evaluation method for a motor oil cooling system, which comprehensively evaluates the cooling system through multiple evaluation indicators to more completely reflect the performance of the motor oil cooling system.

[0007] In order to solve the above technical problems, the present invention provides the following technical solutions: a comprehensive evaluation method for a motor oil cooling system, comprising the following steps:

[0008] S1 collects the temperature of each component in the motor under natural cooling state;

[0009] S2 collects the temperature and flow of each component in the motor under oil cooling;

[0010] S3 defines the evaluation indicators;

[0011] S4 calculates the evaluation value EI of the motor oil cooling system according to the evaluation index i ;

[0012] Among them, the various components include a large magnetic steel and a small magnetic steel in the middle of the rotor axial direction, a front bearing outer ring, a rear bearing outer ring, a front end portion of the winding, and a rear end portion of the winding.

[0013] As a preferred solution of the comprehensive evaluation method of the motor oil cooling system in the present invention, the step of defining the evaluation index is specifically as follows:

[0014] Calculate the front bearing cooling oil flow deviation d bf ,

[0015] Calculate the bearing cooling oil flow deviation d br ,

[0016] Calculate the cooling oil flow deviation d at the front end of the winding br ,

[0017] Calculate the cooling oil flow deviation d at the rear end of the winding wr ,

[0018] Calculate the large magnet cooling oil flow deviation d b ,

[0019] Calculate the small magnet cooling oil flow deviation d s ,

[0020] Among them, Q i is the general cooling oil demand, p h is the heating power of the heating component, ρ is the cooling oil density, c is the specific heat capacity of the cooling oil, and ΔT is the temperature rise of the cooling oil;

[0021] Calculate the cooling efficiency η of the large magnetic steel in the middle of the rotor axial direction Cb ,

[0022] Calculate the cooling efficiency η of the small magnetic steel in the middle of the rotor axial direction Cs ,

[0023] Calculate the cooling efficiency η of the front bearing Cf ,

[0024] Calculate the bearing cooling efficiency η Cf ,

[0025] Calculate the cooling efficiency η of the front end of the winding Cwf ,

[0026] Calculate the cooling efficiency η of the front end of the winding Cwr ,

[0027] Under natural cooling, the temperatures of the rotor axial middle large magnetic steel, small magnetic steel, front bearing outer ring, rear bearing outer ring, front end of the winding, and rear end of the winding are T Nb 、T Ns 、T Nf 、T Nr 、T Nwf and T Nwr ;

[0028] Under oil cooling, the temperatures of the rotor axial middle large magnetic steel, small magnetic steel, front bearing outer ring, rear bearing outer ring, front end of the winding, and rear end of the winding are T Ob 、T Os 、T Of 、T Or 、T Owf and T Owr The cooling oil flow rates of the front bearing, rear bearing, front end of the winding, rear end of the winding, large magnetic steel and small magnetic steel in the middle of the rotor axial direction are Q respectively. bf , Q br , Q wf , Q wr , Q b and Q b ;

[0029] The front bearing cooling oil flow deviation d bf , Rear bearing cooling oil flow deviation d br , Winding front end cooling oil flow deviation d wf , Cooling oil flow deviation at the rear end of the winding d wr , Large magnetic steel cooling oil flow deviation d b , Small magnet cooling oil flow deviation d s , Cooling efficiency of the large magnetic steel in the middle of the rotor axial direction η Cb , Cooling efficiency of the small magnetic steel in the middle of the rotor axial direction η Cs , front bearing cooling efficiency η Cf , rear bearing cooling efficiency η Cr , Cooling efficiency of the front end of the winding η Cwf , Cooling efficiency of the rear end of the winding η Cwr , oil abrasive concentration C and motor efficiency η are used as evaluation indicators to evaluate the motor oil cooling system. i , i=1,2,…,11 represent the above evaluation indicators respectively.

[0030] As a preferred solution of the comprehensive evaluation method of the motor oil cooling system in the present invention, wherein: between step S3 and step S4, the following steps are also included:

[0031] Establish a comprehensive evaluation model for motor oil cooling system;

[0032] Construct a weighting matrix;

[0033] Determine the optimal and worst solutions of the evaluation indicators;

[0034] Calculate the Euclidean distance between the sample and the optimal solution and the worst solution.

[0035] As a preferred solution of the comprehensive evaluation method of the motor oil cooling system in the present invention, in step S4, according to the distance D between the sample value and the optimal solution, i o and the distance D between the sample value and the worst solution i w Calculate the motor oil cooling system evaluation value EI i ,

[0036] As a preferred solution of the comprehensive evaluation method of the motor oil cooling system in the present invention, the step of establishing a comprehensive evaluation model of the motor oil cooling system is specifically as follows:

[0037] A1 constructs original data;

[0038] A2 normalizes the raw data;

[0039] A3 builds the correlation coefficient matrix;

[0040] A4 finds the eigenvalues ​​and eigenvectors of the correlation coefficient matrix R;

[0041] A5 calculates the principal component contribution rate and cumulative contribution rate;

[0042] A6 calculates the principal component weights;

[0043] A7 establishes a comprehensive evaluation model according to the principal component contribution rate, cumulative contribution rate and principal component weight. As a preferred embodiment of the comprehensive evaluation method of the motor oil cooling system in the present invention, step A1 is specifically as follows:

[0044] The oil-cooled motor test data is constructed as the original data matrix X. Each row of the matrix X is the sample value of 11 evaluation indicators. There are n samples to be evaluated. The original data matrix can be expressed as:

[0045]

[0046] Step A2 specifically includes standardizing the original data in X. The standardized form is:

[0047]

[0048] In the formula, is the average value of each sample of the jth evaluation index, Var(x j) is the standard deviation of each sample of the jth evaluation index, and the standardized data matrix is ​​X'.

[0049] As a preferred solution of the comprehensive evaluation method of the motor oil cooling system in the present invention, in step A3, the correlation coefficient matrix R established is:

[0050]

[0051] As a preferred solution of the comprehensive evaluation method of the motor oil cooling system in the present invention, step A4 is specifically as follows:

[0052] Solve the characteristic equation |R-λI|=0, and the obtained eigenvalues ​​are arranged in order of size, λ1≥λ2≥…λ 11 >0, the corresponding eigenvector is,

[0053]

[0054] As a preferred solution of the comprehensive evaluation method of the motor oil cooling system in the present invention, step A5 is specifically as follows:

[0055] To determine the number of principal components, we need to calculate the contribution rate e of the i-th principal component. i And the contribution rate E of the first m principal components m ,

[0056]

[0057]

[0058] When the cumulative contribution rate of the first m principal components is greater than 80%, the first m principal components are selected to characterize the performance of the motor oil cooling system, and the load F of the xth principal component is i It is expressed as,

[0059] F i =a 11 X1+a 12 X2+…+a 111 X 11 , x=1,2,…,m.

[0060] As a preferred solution of the comprehensive evaluation method of the motor oil cooling system in the present invention, step A6 is specifically as follows:

[0061] The contribution rate of the i-th principal component to the first m principal components is used as the principal component weight.

[0062]

[0063] In step A7, the comprehensive evaluation model is: F = b1F1+b2F2+…+b m Fm =ω1X1+ω2X2+…+ω 11 X 11 .

[0064] As a preferred solution of the comprehensive evaluation method of the motor oil cooling system in the present invention, the weighted matrix is:

[0065]

[0066] The optimal solution A0 of the evaluation index is: o =[ω1x o1 ,ω2x o2 ,…,ω 11 x o11 ];

[0067] The worst solution A of the evaluation index w For A w =[ω1x w1 ,ω2x w2 ,…,ω 11 x w11 ];

[0068] The Euclidean distance D between the sample and the optimal solution i o for,

[0069] The Euclidean distance D between the sample value and the worst solution i w for, ω k Represents weight.

[0070] Compared with the prior art, the present invention has the following technical effects: the present invention comprehensively evaluates the oil cooling system of the motor through multiple indicators, thereby improving the accuracy of evaluating the cooling capacity of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0071] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative labor. Among them:

[0072] Figure 1 It is a flowchart of the present invention.

[0073] Figure 2 The flowchart of calculating the index weight in the present invention is shown in FIG. DETAILED DESCRIPTION

[0074] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with the accompanying drawings.

[0075] In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention may also be implemented in other ways different from those described herein, and those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0076] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The term "in one embodiment" that appears in different places in this specification does not necessarily refer to the same embodiment, nor does it refer to a separate or selective embodiment that is mutually exclusive with other embodiments.

[0077] Example 1

[0078] Reference Figure 1 and Figure 2 , this embodiment provides a comprehensive evaluation method for a motor oil cooling system, which can.

[0079] A comprehensive evaluation method for a motor oil cooling system comprises the following steps:

[0080] (1) Collecting the temperature of each component in the motor under natural cooling, including the large magnetic steel and small magnetic steel in the middle of the rotor axial direction, the outer ring of the front bearing, the outer ring of the rear bearing, the front end of the winding, and the rear end of the winding;

[0081] (2) Collect the temperature and flow of each component in the motor under oil cooling;

[0082] (3) Define the evaluation index, specifically, calculate the front bearing cooling oil flow deviation d bf ,

[0083] Calculate the bearing cooling oil flow deviation d br ,

[0084] Calculate the cooling oil flow deviation d at the front end of the winding br ,

[0085] Calculate the cooling oil flow deviation d at the rear end of the winding wr ,

[0086] Calculate the large magnet cooling oil flow deviation d b ,

[0087] Calculate the small magnet cooling oil flow deviation d s ,

[0088] Among them, Q i is the general cooling oil demand, p h is the heating power of the heating component, ρ is the cooling oil density, c is the specific heat capacity of the cooling oil, and ΔT is the temperature rise of the cooling oil;

[0089] Calculate the cooling efficiency η of the large magnetic steel in the middle of the rotor axial direction Cb ,

[0090] Calculate the cooling efficiency η of the small magnetic steel in the middle of the rotor axial direction Cs ,

[0091] Calculate the cooling efficiency η of the front bearing Cf ,

[0092] Calculate the bearing cooling efficiency η Cf ,

[0093] Calculate the cooling efficiency η of the front end of the winding Cwf ,

[0094] Calculate the cooling efficiency η of the front end of the winding Cwr ,

[0095] Under natural cooling, the temperatures of the rotor axial middle large magnetic steel, small magnetic steel, front bearing outer ring, rear bearing outer ring, front end of the winding, and rear end of the winding are T Nb 、T Ns 、T Nf 、T Nr 、T Nwf and T Nwr ;

[0096] Under oil cooling, the temperatures of the rotor axial middle large magnetic steel, small magnetic steel, front bearing outer ring, rear bearing outer ring, front end of the winding, and rear end of the winding are T Ob 、T Os 、T Of 、T Or 、T Owf and T Owr The cooling oil flow rates of the front bearing, rear bearing, front end of the winding, rear end of the winding, large magnetic steel and small magnetic steel in the middle of the rotor axial direction are Q respectively. bf , Q br , Q wf , Q wr , Q band Q b ;

[0097] The front bearing cooling oil flow deviation d bf , Rear bearing cooling oil flow deviation d br , Winding front end cooling oil flow deviation d wf , Cooling oil flow deviation at the rear end of the winding d wr , Large magnetic steel cooling oil flow deviation d b , Small magnet cooling oil flow deviation d s , Cooling efficiency of the large magnetic steel in the middle of the rotor axial direction η Cb , Cooling efficiency of the small magnetic steel in the middle of the rotor axial direction η Cs , front bearing cooling efficiency η Cf , rear bearing cooling efficiency η Cr , Cooling efficiency of the front end of the winding η Cwf , Cooling efficiency of the rear end of the winding η Cwr , oil abrasive concentration C and motor efficiency η are used as evaluation indicators to evaluate the motor oil cooling system. i , i=1,2,…,11 represent the above evaluation indicators respectively;

[0098] (4) Calculate the weight of each evaluation index, which specifically includes the following steps:

[0099] (401) Establish a comprehensive evaluation model for motor oil cooling system:

[0100] A1 constructs the original data. The oil-cooled motor test data is constructed into the original data matrix X. Each row of the matrix X is the sample value of 11 evaluation indicators. There are n samples to be evaluated. The original data matrix can be expressed as:

[0101]

[0102] A2 standardizes the original data in X. The standardized form is:

[0103]

[0104] In the formula, is the average value of each sample of the jth evaluation index, Var(x j ) is the standard deviation of each sample of the jth evaluation index, and the standardized data matrix is ​​X';

[0105] A3 establishes the correlation coefficient matrix R,

[0106] A4 finds the eigenvalues ​​and eigenvectors of the correlation coefficient matrix R, solves the characteristic equation |R-λI|=0, and arranges the obtained eigenvalues ​​in order of size, λ1≥λ2≥…λ 11>0, the corresponding eigenvector is,

[0107]

[0108] A5 To determine the number of principal components, we need to calculate the contribution rate e of the ith principal component. i And the contribution rate E of the first m principal components m ,

[0109]

[0110] A6 calculates the weight of the principal components: When the cumulative contribution rate of the first m principal components is greater than 80%, the first m principal components are selected to characterize the performance of the motor oil cooling system, and the load F of the i-th principal component i It is expressed as,

[0111] F i =a 11 X1+a 12 X2+…+a 111 X 11 , i=1,2,…,m;

[0112] The contribution rate of the i-th principal component to the first m principal components is used as the principal component weight.

[0113]

[0114] A7 establishes a comprehensive evaluation model F based on the principal component contribution rate, cumulative contribution rate and principal component weight, F = b1F1+b2F2+…+b m F m =ω1X1+ω2X2+…+ω 11 X 11 ,ω k is the weight;

[0115] (402) Construct a weight matrix A,

[0116] (403) Determine the optimal solution and the worst solution of the evaluation index: The optimal solution A0 of the evaluation index is, A o =[ω1x o1 ,ω2x o2 ,…,ω 11 x o11 ];

[0117] The optimal solution of the evaluation index A w For A w =[ω1x w1 ,ω2x w2 ,…,ω 11 x w11 ];

[0118] (404) Calculate the Euclidean distance between the sample and the optimal solution and the worst solution, and the Euclidean distance D between the sample and the optimal solution i o for,

[0119] The Euclidean distance D between the sample value and the worst solution i w for,

[0120] (5) According to the distance D between the sample value and the optimal solution i o and the distance D between the sample value and the worst solution i w Calculate the motor oil cooling system evaluation value EI i ,

[0121] The present invention quantitatively evaluates the motor oil cooling system through multiple indicators such as temperature, flow rate, efficiency, etc., constructs multiple oil-cooled motor test data into an original data matrix X, and obtains a standardized data matrix X′ after the matrix is ​​standardized. Then, a correlation coefficient matrix R is constructed through the transposed matrix of X′ and the X′ matrix, and the eigenvalue and eigenvector of the correlation coefficient matrix R are obtained. The number of principal components can be obtained by calculating the contribution rate of the ith principal component and the contribution rates of the first m principal components. When the cumulative contribution rates of the first m principal components are greater than 80%, it can be considered that the first m principal components can be used to characterize the performance of the motor cooling system. Finally, a comprehensive evaluation model F is established through the principal component contribution rate, the cumulative contribution rate and the principal component weight, and a strengthening matrix A is further constructed. The cooling system is comprehensively evaluated through multiple evaluation indicators by calculating the Euclidean distance between the sample and the optimal solution and the worst solution, so as to more completely reflect the performance of the motor oil cooling system and further calculate the evaluation value of the motor cooling system.

[0122] Example 2

[0123] This embodiment provides a comprehensive evaluation method for a motor oil cooling system. This embodiment is based on the previous embodiment and illustrates the method of the present application through actual experiments.

[0124] Specifically, the present invention is used to comprehensively evaluate different oil cooling systems of the same permanent magnet synchronous motor.

[0125] Table 1 shows the experimental data of three oil cooling systems for a certain type of motor

[0126]

[0127]

[0128] The original data matrix of the evaluation index is as follows:

[0129]

[0130] Original data normalized matrix:

[0131]

[0132] Correlation coefficient matrix:

[0133]

[0134] The contribution rate of each principal component is: 97.14, 2.85, 0, 0, 0, 0, 0, 0, 0, 0. The cumulative contribution rate of the first two principal components is greater than 80%. Therefore, the first two principal components are selected to evaluate the motor oil cooling system, and the weight of each indicator is calculated as follows:

[0135] ω1=0.3, ω2=0.3, ω3=0.29, ω4=0.29, ω5=-0.29, ω6=-0.27, ω7=-0.3, ω8=-0.28, ω9=-0.29, ω 10 =-0.27,ω 10 =-0.27,ω 11 =0.3;

[0136] The comprehensive evaluation values ​​of the three motor oil cooling systems are: EIA=0.6182, EIB=0.6863, EIC=0.4223. Therefore, the performance of oil cooling system C is the best, followed by oil cooling system A, and oil cooling system B is the worst.

[0137] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

Claims

1. A comprehensive evaluation method for a motor oil cooling system, characterized in that: It includes the following step; S1 collects the temperature of each component in the motor under natural cooling state; S2 collects the temperature and flow of each component in the motor under oil cooling; S3 defines the evaluation indicators; S4 calculates the evaluation value EI of the motor oil cooling system according to the evaluation index i ; Among them, the various components include a large magnetic steel and a small magnetic steel in the middle of the rotor axial direction, a front bearing outer ring, a rear bearing outer ring, a front end portion of the winding, and a rear end portion of the winding.

2. The comprehensive evaluation method for the motor oil cooling system according to claim 1, characterized in that: The specific steps to define the evaluation indicators are as follows: Calculate the front bearing cooling oil flow deviation d bf , Calculate the bearing cooling oil flow deviation d br , Calculate the cooling oil flow deviation d at the front end of the winding br , Calculate the cooling oil flow deviation d at the rear end of the winding wr , Calculate the large magnetic steel cooling oil flow deviation d b , Calculate the small magnet cooling oil flow deviation d s , Among them, Q i is the general demand for cooling oil, p h is the heating power of the heating component, ρ is the cooling oil density, c is the specific heat capacity of the cooling oil, and ΔT is the temperature rise of the cooling oil; Calculate the cooling efficiency η of the large magnetic steel in the middle of the rotor axial direction Cb , Calculate the cooling efficiency η of the small magnetic steel in the middle of the rotor axial direction Cs , Calculate the cooling efficiency η of the front bearing Cf , Calculate the cooling efficiency of the bearing η Cf , Calculate the cooling efficiency η of the front end of the winding Cwf , Calculate the cooling efficiency η of the front end of the winding Cwr , Under natural cooling, the temperatures of the rotor axial middle large magnetic steel, small magnetic steel, front bearing outer ring, rear bearing outer ring, front end of the winding, and rear end of the winding are T Nb , T Ns , T Nf , T Nr , T Nwf and T Nwr ; Under oil cooling, the temperatures of the rotor axial middle large magnetic steel, small magnetic steel, front bearing outer ring, rear bearing outer ring, front end of the winding, and rear end of the winding are T Ob , T Os , T Of , T Or , T Owf and T Owr The cooling oil flow rates of the front bearing, rear bearing, front end of the winding, rear end of the winding, large magnetic steel and small magnetic steel in the middle of the rotor axial direction are Q respectively. bf , Q br , Q wf , Q wr , Q b and Q b ; The front bearing cooling oil flow deviation d bf , Rear bearing cooling oil flow deviation d br , Winding front end cooling oil flow deviation d wf , Cooling oil flow deviation at the rear end of the winding d wr , Large magnetic steel cooling oil flow deviation d b , Small magnet cooling oil flow deviation d s , Cooling efficiency of the large magnetic steel in the middle of the rotor axial direction η Cb , Cooling efficiency of the small magnetic steel in the middle of the rotor axial direction η Cs , front bearing cooling efficiency η Cf , rear bearing cooling efficiency η Cr , Cooling efficiency of the front end of the winding η Cwf , Cooling efficiency of the rear end of the winding η Cwr , oil abrasive concentration C and motor efficiency η are used as evaluation indicators to evaluate the motor oil cooling system. i , i=1,2,…,11 represent the above evaluation indicators respectively.

3. The comprehensive evaluation method for the motor oil cooling system according to claim 2, characterized in that: Between step S3 and step S4, the following steps are also included: Establish a comprehensive evaluation model for motor oil cooling system; Construct a weighting matrix; Determine the optimal and worst solutions of the evaluation indicators; Calculate the Euclidean distance between the sample and the optimal solution and the worst solution; In step S4, according to the distance D between the sample value and the optimal solution i o and the distance D between the sample value and the worst solution i w Calculate the motor oil cooling system evaluation value EI i , i=1,2,…,n.

4. The comprehensive evaluation method for the motor oil cooling system according to claim 3, characterized in that: The specific steps to establish a comprehensive evaluation model for the motor oil cooling system are: A1 constructs original data; A2 normalizes the raw data; A3 builds the correlation coefficient matrix; A4 finds the eigenvalues ​​and eigenvectors of the correlation coefficient matrix R; A5 calculates the principal component contribution rate and cumulative contribution rate; A6 calculates the principal component weights; A7 establishes a comprehensive evaluation model based on the principal component contribution rate, cumulative contribution rate and principal component weight.

5. The comprehensive evaluation method for the motor oil cooling system according to claim 4, characterized in that: Step A1 specifically includes: The oil-cooled motor test data is constructed as the original data matrix X. Each row of the matrix X is the sample value of 11 evaluation indicators. There are n samples to be evaluated. The original data matrix can be expressed as: Step A2 specifically includes standardizing the original data in X. The standardized form is: In the formula, is the average value of each sample of the jth evaluation index, Var(x j ) is the standard deviation of each sample of the jth evaluation index, and the standardized data matrix is ​​X'.

6. The comprehensive evaluation method for the motor oil cooling system according to claim 5, characterized in that: In step A3, the correlation coefficient matrix R established is:

7. The comprehensive evaluation method for the motor oil cooling system according to claim 6, characterized in that: Step A4 specifically includes: Solve the characteristic equation |R-λI|=0, and the obtained eigenvalues ​​are arranged in order of size, λ1≥λ2≥…λ 11 >0, the corresponding eigenvector is, 8. The comprehensive evaluation method for the motor oil cooling system according to claim 7, characterized in that: Step A5 specifically includes: To determine the number of principal components, we need to calculate the contribution rate e of the i-th principal component. i And the contribution rate E of the first m principal components m , When the cumulative contribution rate of the first m principal components is greater than 80%, the first m principal components are selected to characterize the performance of the motor oil cooling system, and the load F of the xth principal component is i It is expressed as, F i =a 11 X1+a 12 X2+…+a 111 X 11 ,x=1,2,…,m。 9. The comprehensive evaluation method for the motor oil cooling system according to claim 8, characterized in that: Step A6 specifically includes: The contribution rate of the i-th principal component to the first m principal components is used as the principal component weight. In step A7, the comprehensive evaluation model is: F = b1F1+b2F2+…+b m F m =ω1X1+ω2X2+…+ω 11 X 11 .

10. The comprehensive evaluation method for the motor oil cooling system according to claim 9, characterized in that: The weighting matrix is, The optimal solution A0 of the evaluation index is: o =[ω1x o1 ,ω2x o2 ,…,ω 11 x o11 ]; The worst solution A of the evaluation index w For A w =[ω1x w1 ,ω2x w2 ,…,ω 11 x w11 ]; The Euclidean distance D between the sample and the optimal solution i o for, The Euclidean distance D between the sample value and the worst solution i w for, i=1,2,…,n;ω k Represents weight.

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