Method for screening and optimizing vehicle-mounted stretcher modification schemes

Abstract

The invention relates to the field of medical treatment, in particular to a method for screening and optimizing vehicle-mounted stretcher modification schemes. Through simulation experiments (static characteristic analysis, dynamic characteristic analysis, fatigue life evaluation, strength and rigidity check and the like), performance index data of the stretcher corresponding to each modification prefabrication scheme is obtained, and each modification prefabrication scheme is scored by using a prefabrication stretcher performance evaluation model; according to the method, the vehicle-mounted stretcher system refitting scheme is screened and optimized, optimization of the vehicle-mounted stretcher system refitting scheme can be ensured, the vehicle-mounted stretcher system refitting functionality and economic benefits are ensured, and the actual requirement for a vehicle-mounted stretcher is met.

Description

Technical Field

[0001] The present invention relates to the field of medical treatment, and particularly relates to a method for screening and optimizing the modification schemes of on-vehicle stretchers. Background Art

[0002] In rescue operations, an on-vehicle stretcher is a device specifically designed and installed in an ambulance for carrying and fixing injured and sick patients, and is one of the core equipments of an ambulance. Since the manufacturers of ambulances and on-vehicle stretchers are different and the manufacturing standards are inconsistent, the compatibility between an ambulance and an on-vehicle stretcher is extremely poor, resulting in a complex operation of the stretcher system installed in the ambulance, limited performance and adjustment functions, inability to meet the requirements of modern high-efficiency treatment, and serious reduction of the comprehensive efficiency of the transfer of injured and sick patients.

[0003] To solve the above problems and improve the compatibility between the on-vehicle stretcher and the ambulance, it is necessary to formulate multiple modification schemes for the specific models of ambulances to improve the on-vehicle stretchers in the ambulance (such as adding new functional components, etc.). Then, according to these modification schemes, the entities of the on-vehicle stretchers are transformed and tested. Finally, based on the test results, the advantages and disadvantages of each modification scheme of the on-vehicle stretcher are determined. This method not only requires the purchase of a variety of professional equipments and high-quality materials, but also requires professional technicians to modify and debug the on-vehicle stretcher, which is time-consuming and laborious. Moreover, during the modification process, once physical structure changes are made to the vehicle or the on-vehicle stretcher, such as cutting the interior decorative board of the vehicle and welding the stretcher fixing track, it will be very difficult to modify the on-vehicle stretcher again, and even cause the items to be scrapped.

[0004] How to quickly and accurately screen out suitable improvement schemes for the on-vehicle stretcher system has always been an urgent problem to be solved by those skilled in the art. Summary of the Invention

[0005] The purpose of the present invention is to provide a method for screening and optimizing the modification schemes of on-vehicle stretchers in view of the corresponding deficiencies of the prior art. By establishing a performance evaluation model for prefabricated stretchers and obtaining the performance index data of the stretchers corresponding to each prefabricated modification scheme through simulation experiments (static characteristic analysis, dynamic characteristic analysis, fatigue life evaluation, strength and stiffness check, etc.), the prefabricated stretcher performance evaluation model is used to score each prefabricated modification scheme, so as to realize the screening and optimization of the modification schemes of the on-vehicle stretcher system, and improve the functionality and economic benefits of the modification of the stretcher system.

[0006] The purpose of the present invention is achieved by the following scheme:

[0007] A method for screening and optimizing the modification schemes of on-vehicle stretchers includes the following steps:

[0008] 1) Combine the fuzzy evaluation algorithm and the analytic hierarchy process to establish a performance evaluation model for the prefabricated stretcher;

[0009] 2) Collect the physical data of the vehicle and the on-vehicle stretcher, and respectively construct finite element simulation models corresponding to the vehicle entity and the on-vehicle stretcher entity;

[0010] 3) In the simulation experiment, according to several prefabrication schemes for modification, adjust the finite element simulation model of the on-vehicle stretcher, and respectively combine the adjusted multiple finite element simulation models of the on-vehicle stretcher with the finite element simulation model of the vehicle to form several finite element simulation models of the prefabricated stretcher corresponding to each prefabrication scheme for modification;

[0011] 4) Evaluate the practicability of each prefabrication scheme for modification by using static characteristic analysis, dynamic characteristic analysis, fatigue life assessment, strength and stiffness check, and record the performance index data of each finite element simulation model of the prefabricated stretcher during the evaluation process. Combine the performance evaluation model of the prefabricated stretcher to score each finite element simulation model of the prefabricated stretcher;

[0012] 5) Take the finite element simulation model of the prefabricated stretcher with the highest score as the optimal simulation model to form the final modification scheme for the on-vehicle stretcher.

[0013] Preferably, in step 1), the specific method of combining the fuzzy evaluation algorithm and the analytic hierarchy process to establish a performance evaluation model for the prefabricated stretcher includes:

[0014] 1-1) Combine the actual requirements to establish a hierarchical structure model of the stretcher performance evaluation index system, use each performance evaluation index in the stretcher performance evaluation index system as the evaluation index set, and determine the evaluation grade set;

[0015] 1-2) Use the trapezoidal distribution method to calculate the membership function of each performance evaluation index, conduct single-factor fuzzy evaluation on each performance evaluation index, and establish a fuzzy relation matrix;

[0016] 1-3) Use the 1-9 scale method to compare the relative importance of each performance evaluation index in the criterion layer pairwise according to expert opinions or the subjective judgment of the decision maker, construct a pairwise comparison matrix, and obtain a consistency matrix based on these pairwise comparison matrices;

[0017] 1-4) Calculate the single-layer weight vector, conduct a consistency test, and conduct hierarchical single sorting;

[0018] 1-5) Calculate the combined weight vector, conduct a consistency test, and conduct hierarchical total sorting;

[0019] 1-6) Based on the combined weight vector and the fuzzy relation matrix, establish a judgment model matrix;

[0020] 1-7) Normalize the data in the judgment model matrix to obtain the membership degrees of each performance evaluation index, and form the performance evaluation results of the prefabricated stretcher.

[0021] Preferably, in step 1-4), calculate the single-layer weight vector and perform a consistency test. The specific method for performing the hierarchical single sorting includes:

[0022] 1-4-1) Calculate the maximum eigenvalue, eigenvector, and consistency index of each consistency matrix;

[0023] 1-4-2) Calculate the random consistency index and consistency ratio based on several consistency indexes, and use the consistency index, random consistency index, and consistency ratio to perform a consistency test:

[0024] ① If the consistency ratio < 0.1, the consistency matrix passes the consistency test. Normalize each eigenvector to obtain the weight vector, and sort each evaluation index according to the weight vector;

[0025] ② If the consistency ratio ≥ 0.1, the consistency matrix fails the consistency test, and reconstruct the pairwise comparison matrix.

[0026] Preferably, in step 1-5), calculate the combined weight vector and perform a consistency test. The specific method for performing the hierarchical total sorting includes:

[0027] 1-5-1) According to the constructed pairwise comparison matrix, calculate the maximum eigenvalue, eigenvector, and consistency index of each pairwise comparison matrix;

[0028] 1-5-2) Calculate the random consistency index and consistency ratio based on several consistency indexes, and use the consistency ratio to perform a combined consistency test:

[0029] ① If the consistency ratio < 0.1, the hierarchical total sorting passes the consistency test. Calculate the combined weight vector of the scheme layer with respect to the overall goal, and sort each performance evaluation index of the scheme layer according to the combined weight vector;

[0030] ② If the consistency ratio ≥ 0.1, the hierarchical total sorting fails the consistency test, and reconsider the model or readjust the element values of the pairwise comparison matrix with a high consistency ratio.

[0031] Preferably, the data in the judgment model matrix is obtained according to the following formula:

[0032] I = S × R

[0033] In the formula, I is the stretcher performance index in the judgment model matrix, S is the weight vector of the performance evaluation index, and R is the fuzzy relation matrix.

[0034] Preferably, in step 4), the practicability of each prefabrication and modification plan is evaluated by means of static characteristic analysis, dynamic characteristic analysis, fatigue life assessment, strength and stiffness check, and the performance index data of each finite element simulation model of the prefabricated stretcher is recorded during the evaluation process. The specific method for scoring each finite element simulation model of the prefabricated stretcher by combining the performance evaluation model of the prefabricated stretcher includes:

[0035] 4-1) Establish several scenarios, each of which contains a different typical working condition, and place each finite element simulation model of the prefabricated stretcher under each typical working condition;

[0036] 4-2) Adopt the static analysis method of vehicle finite element to conduct static characteristic analysis on each finite element simulation model of the prefabricated stretcher, and calculate and record the allowable stress of each finite element simulation model of the prefabricated stretcher under each typical working condition respectively;

[0037] 4-3) Adopt the finite element modal dynamics analysis method to conduct dynamic characteristic analysis on each finite element simulation model of the prefabricated stretcher, and calculate and record the natural frequency and vibration mode of each finite element simulation model of the prefabricated stretcher under each typical working condition respectively;

[0038] 4-4) Combine the fatigue analysis software to conduct fatigue life assessment on each finite element simulation model of the prefabricated stretcher, and calculate and record the damage and life of each finite element simulation model of the prefabricated stretcher under each typical working condition respectively;

[0039] 4-5) Calculate and check the stiffness and strength of each finite element simulation model of the prefabricated stretcher under static conditions respectively;

[0040] 4-6) Take the allowable stress obtained in step 4-2), the natural frequency and vibration mode obtained in step 4-3), the damage and life obtained in step 4-4), and the stiffness and strength obtained in 4-5) as the performance index data of the corresponding finite element simulation model of the prefabricated stretcher, and use the performance evaluation model of the prefabricated stretcher to score each finite element simulation model of the prefabricated stretcher.

[0041] Preferably, the specific method for scoring each finite element simulation model of the prefabricated stretcher by using the performance evaluation model of the prefabricated stretcher includes:

[0042] 4-6-1) Normalize the performance index data of each finite element simulation model of the prefabricated stretcher, and calculate the percentage of each performance index data in the total performance index data of the corresponding finite element simulation model of the prefabricated stretcher respectively;

[0043] 4-6-2) Convert each percentage calculated in step 4-6-1) into an integer real number and use it as the weight score of each performance index of the corresponding finite element simulation model of the prefabricated stretcher.

[0044] 4-6-3) Combine the weight scores calculated in step 4-6-2) with the prefabricated stretcher performance evaluation model, calculate the scores of each performance index of the prefabricated stretcher finite element simulation model, sum up the scores of each performance index, calculate the total scores of each prefabricated stretcher finite element simulation model, and determine the superiority and inferiority levels.

[0045] Preferably, in step 4-5), the specific methods for calculating and checking the stiffness and strength of each prefabricated stretcher finite element simulation model under static conditions include:

[0046] 4-5-1) In each prefabricated stretcher finite element simulation model, simplify the stretcher's support arm into a cantilever beam in material mechanics, perform mesh division on the stretcher's support frame, and load each prefabricated stretcher finite element simulation model.

[0047] 4-5-2) Calculate the bending moment normal stress and deflection values of the stretcher support arm in each prefabricated stretcher finite element simulation model respectively.

[0048] 4-5-3) According to the bending moment normal stress and deflection values calculated in step 4-5-2), judge whether the strength and stiffness of the stretcher support arm of each prefabricated stretcher finite element simulation model meet the requirements in the following way:

[0049] If the bending moment normal stress < the yield stress of the stretcher support arm material, the stiffness of the support arm meets the requirements;

[0050] If the bending moment normal stress ≥ the yield stress of the stretcher support arm material, the stiffness of the support arm does not meet the requirements;

[0051] If the deflection value < the deflection threshold, the strength of the support arm meets the requirements;

[0052] If the deflection value ≥ the deflection threshold, the strength of the support arm does not meet the requirements;

[0053] 4-5-4) Set constraints and loads on the stretcher support frame in each prefabricated stretcher finite element simulation model, and use the static analysis method to calculate the deformation and maximum equivalent stress of the stretcher support frame in each prefabricated stretcher finite element simulation model respectively.

[0054] 4-5-5) According to the deformation and maximum equivalent stress calculated in step 4-5-4), judge whether the strength and stiffness of the stretcher support frame of each prefabricated stretcher finite element simulation model meet the requirements in the following way:

[0055] If the maximum deformation ≤ the deformation threshold, the stiffness of the support frame meets the requirements;

[0056] If the maximum deformation > the deformation threshold, the stiffness of the support frame does not meet the requirements;

[0057] If the maximum equivalent stress ≤ the yield strength of the material, the strength of the support frame meets the requirements;

[0058] If the maximum equivalent stress > the yield strength of the material, the strength of the support frame does not meet the requirements;

[0059] 4-5-6) Load the cross-moving guide rail bearing pins, and calculate the shear stress of each single bearing pin in the finite element simulation model of each prefabricated stretcher;

[0060] 4-5-7) According to the calculated shear stress of each single bearing pin, judge the shear strength check of the cross-moving guide rail bearing pins of each prefabricated stretcher finite element simulation model in the following way:

[0061] If the shear stress < the allowable shear stress of the material, the shear strength of the cross-moving guide rail bearing pin meets the requirements;

[0062] If the shear stress ≥ the allowable shear stress of the material, the shear strength of the cross-moving guide rail bearing pin does not meet the requirements.

[0063] Preferably, the range of the deflection threshold is 10 - 11 mm.

[0064] Preferably, the range of the deformation threshold is 8 - 9 mm.

[0065] The beneficial effects of the present invention are as follows:

[0066] ① By setting multiple thresholds, the present invention can ensure that the strength of the material used for the prefabricated stretcher meets the standards of the vehicle-mounted stretcher and meets the requirements for the material strength when the vehicle-mounted stretcher actually bears patients;

[0067] ② By setting the prefabricated stretcher under several typical working conditions and conducting static analysis and fatigue life analysis on the vehicle-mounted stretcher under typical working conditions for comparison, the present invention can achieve a comprehensive analysis of the use performance and safety reliability of the vehicle-mounted stretcher to ensure that the modification and addition plan of the vehicle-mounted stretcher can adapt to most road conditions;

[0068] ③ The present invention takes into account objective indicators, subjective indicators, scientifically distributes weight coefficients, establishes a performance evaluation model for the prefabricated stretcher, and uses a combination of empirical assignment, functional requirement assignment, and analytic hierarchy process statistical assignment to assign weights to the performance indicators of the prefabricated stretcher, so as to comprehensively and efficiently score the prefabricated stretcher to ensure the optimization of the modification and addition plan.

[0069] The advantages of the present invention are as follows:

[0070] ① Aiming at the modification problem of a vehicle-mounted stretcher system, the present invention provides a method for screening and optimizing the modification scheme of a vehicle-mounted stretcher, which can reduce the cost and time consumption when screening the modification scheme of a prefabricated stretcher, and fully evaluate the modification scheme of the vehicle-mounted stretcher, thereby ensuring the optimization of the modification scheme and the functionality and economic benefits of the modification of the vehicle-mounted stretcher system;

[0071] ② The present invention provides an optimization scheme for the modification scheme of the vehicle-mounted stretcher by performing static analysis and dynamic analysis on the prefabricated stretcher, and can further optimize the optimal modification scheme to a certain extent, so that the optimized modification scheme can meet the actual demand for the vehicle-mounted stretcher.

[0072] Glossary

[0073] AHP: It is a hierarchical weighted decision analysis method proposed by applying network system theory and multi-objective comprehensive evaluation. Based on an in-depth analysis of the nature, influencing factors and their internal relationships of complex decision-making problems, it uses less quantitative information to make the decision-making thinking process mathematical, thereby providing simple decisions for complex decision-making problems with multiple objectives, multiple criteria or unstructured characteristics. It is a decision analysis method that combines qualitative and quantitative methods to solve complex multi-objective problems.

[0074] Trapezoidal distribution method: It is a common method for determining the membership function. The membership function is mainly used in the field of fuzzy mathematics to quantify the degree to which an element belongs to a fuzzy set.

[0075] Computer Aided Engineering (CAE) fatigue analysis technology: It is an advanced technical means to estimate and analyze the fatigue life of structures under alternating loads with the help of computer software and related numerical simulation methods.

[0076] Modification: refers to adding parts or changing the structure of the stretcher on the original basis. For example, adding medical equipment mounting points, improving fixtures, optimizing comfort configuration, etc., the purpose is to enhance its function, enhance adaptability, and improve patient comfort, but it must follow safety principles and be implemented by professionals in accordance with regulations.

[0077] Finite element static analysis of the whole vehicle: mainly used to evaluate the structural response of the whole vehicle when it is at rest and subjected to various static loads

[0078] Main excitation frequency: It refers to the external excitation frequency acting on a structure (such as a prefabricated stretcher) or system that can cause significant vibration response. When the frequency of the external excitation is close to or equal to the natural frequency of the structure (obtained through modal analysis), resonance occurs, and at this time, the external excitation frequency has a particularly important impact on the structure, and this frequency is the main excitation frequency.

[0079] Stress-life curve: That is, the S-N curve, which is a curve used to describe the fatigue life of materials under different external stresses. Description of the drawings

[0080] Figure 1 This is the flowchart of the present embodiment;

[0081] Figure 2 This is the flowchart for establishing a three-level quantitative performance evaluation model of the prefabricated stretcher in the present embodiment;

[0082] Figure 3 This is a schematic diagram of the three-level quantitative evaluation structural model and index system of the prefabricated stretcher performance in the present embodiment;

[0083] Figure 4 This is the flowchart for collecting target entity data information in the present embodiment;

[0084] Figure 5 This is a schematic diagram of the fine model of the whole vehicle in the present embodiment;

[0085] Figure 6 This is a schematic diagram of adding textures and materials to the on-vehicle stretcher and the target vehicle in the present embodiment;

[0086] Figure 7 This is a schematic diagram of the simulation effect of the ambulance cabin and the on-vehicle stretcher model of the target vehicle in the present embodiment;

[0087] Figure 8 This is a schematic diagram of the tetrahedral mesh division result of the prefabricated stretcher support frame in the present embodiment;

[0088] Figure 9 This is the flowchart for generating the finite element model of the prefabricated stretcher in the present embodiment;

[0089] Figure 10 This is the flowchart for processing the secondary performance indicators of the stretcher in the present embodiment;

[0090] Figure 11 This is the operation flowchart of the response time of the stretcher in the present embodiment;

[0091] Figure 12 This is a schematic diagram of calculating the weights and scores of the primary performance indicators of the stretcher in the present embodiment;

[0092] Figure 13 This is a schematic diagram of the relationship between the prefabricated stretcher and the vehicle body and the top view of the modeling in the present embodiment;

[0093] Figure 14 Schematic diagram of typical working conditions of this embodiment;

[0094] Figure 15 Schematic diagram of the stress-life curve of the prefabricated stretcher in this embodiment;

[0095] Figure 16 Five-block diagram of fatigue durability analysis of the prefabricated stretcher in this embodiment;

[0096] Figure 17 Schematic diagram of the stress nephogram and displacement diagram after optimizing the prefabricated stretcher under typical working conditions in this embodiment, Figure 17 a is the horizontal bending condition, Figure 17 b is the ultimate bending and torsion condition, Figure 17 c is the braking condition, Figure 17 d is the emergency turning condition, Figure 17 e is the motor traction condition, Figure 17 f is the tilting condition;

[0097] Figure 18 Schematic diagram of the overall structure mode of the prefabricated stretcher in this embodiment;

[0098] Figure 19 Schematic diagram of the vibration mode of each order in this embodiment. The left figure is before optimization and the right figure is after optimization, Figure 19 a is the first order, Figure 19 b is the second order, Figure 19 c is the third order, Figure 19 d is the fourth order, Figure 19 e is the fifth order;

[0099] Figure 20 Schematic diagram of the cross-sectional view of the upper and lower stretcher arms of the prefabricated stretcher in this embodiment;

[0100] Figure 21 Schematic diagram of the life nephogram of the prefabricated stretcher under typical working conditions in this embodiment, Figure 21 a is horizontal bending, Figure 21 b is ultimate bending and torsion, Figure 21 c is braking, Figure 21 d is emergency turning, Figure 21 e is motor traction, Figure 21 f is the tilting condition;

[0101] Figure 22 Schematic diagram of the end structure of the prefabricated stretcher and the transverse movement guide rail in this embodiment;

[0102] Figure 23 Schematic diagram of the constraints and load distributions of the support frame of the prefabricated stretcher in this embodiment;

[0103] Figure 24 This is a schematic diagram of the total deformation nephogram and equivalent stress nephogram of the prefabricated stretcher support frame in this embodiment. Figure 24 a is a schematic diagram of the total deformation nephogram. Figure 24 b is a schematic diagram of the equivalent stress nephogram.

[0104] Figure 25 This is a flow chart of the present invention. Detailed implementation manners

[0105] As Figures 1 to 25 shown, a method for screening and optimizing the modification scheme of a vehicle-mounted stretcher includes the following steps:

[0106] 1) Combine the fuzzy evaluation algorithm and the analytic hierarchy process to establish a performance evaluation model for the prefabricated stretcher.

[0107] 2) Collect the physical data of the vehicle and the vehicle-mounted stretcher, and respectively construct finite element simulation models corresponding to the vehicle entity and the vehicle-mounted stretcher entity.

[0108] 3) In the simulation experiment, adjust the finite element simulation model of the vehicle-mounted stretcher according to several prefabricated modification schemes, and respectively combine the adjusted multiple finite element simulation models of the vehicle-mounted stretcher with the finite element simulation model of the vehicle to form several finite element simulation models of the prefabricated stretcher corresponding to each prefabricated modification scheme.

[0109] 4) Evaluate the practicability of each prefabricated modification scheme by using static characteristic analysis, dynamic characteristic analysis, fatigue life assessment, strength and stiffness checking methods, record the performance index data of each finite element simulation model of the prefabricated stretcher during the evaluation process, and score each finite element simulation model of the prefabricated stretcher in combination with the performance evaluation model of the prefabricated stretcher.

[0110] 5) Take the finite element simulation model of the prefabricated stretcher with the highest score as the optimal simulation model to form the final modification scheme of the vehicle-mounted stretcher.

[0111] According to the above method, the following is an embodiment:

[0112] 1) The specific method for combining the fuzzy evaluation algorithm and the analytic hierarchy process to establish a performance evaluation model for the prefabricated stretcher is as follows:

[0113] 1-1) Combine the actual requirements to establish a hierarchical structure model of the stretcher performance evaluation index system, use each performance evaluation index in the stretcher performance evaluation index system as the evaluation index set, and determine the evaluation grade set.

[0114] The specific structure of the hierarchical structure model of the stretcher performance evaluation index system is as follows:

[0115] Goal layer (A): Stretcher performance;

[0116] Criterion layer (B): B1: Response time, B2: Thrust, B3: Usability, B4: Static characteristics, B5: Dynamic characteristics, B6: Maintainability, B7: Satisfaction level;

[0117] Sub-criterion layer (C): Sub-criteria under B1: C11: Deployment time, C12: Withdrawal time; Sub-criteria under B2: C21: Longitudinal thrust, C22: Lateral thrust; Sub-criteria under B3: C31: Load weight, C32: Service life; Sub-criteria under B4: C41: Stress, C42: Displacement; Sub-criteria under B5: C51: Natural frequency, C52: Natural vibration mode; Sub-criteria under B6: C61: Power supply selection, C62: Repair method, C63: Domestic production rate; Sub-criteria under B7: C71: Applicability, C72: Safety;

[0118] Alternative layer (D): D1: Stretcher A, D2: Stretcher B, D3: Stretcher C.

[0119] The evaluation grades are: Excellent, Sub-excellent, Good.

[0120] 1 - 2) Using the trapezoidal distribution method, calculate the membership functions of each performance evaluation index, conduct single-factor fuzzy evaluation on each performance evaluation index, and establish a fuzzy relation matrix (assuming the indicators of Stretcher A are as shown in Table 1);

[0121] Table 1 Indicators of Stretcher A

[0122]

[0123]

[0124] 1 - 3) Using the 1 - 9 scale method, according to expert opinions or the subjective judgment of decision-makers, pairwise compare the relative importance between each performance evaluation index in the criterion layer, construct a pairwise comparison matrix, and obtain a consistency matrix based on these pairwise comparison matrices;

[0125] The consistency matrix of the criterion layer is:

[0126]

[0127] The consistency matrix of the sub-criterion layer is:

[0128]

[0129] 1 - 4) Calculate the weight vectors of the single layer (criterion layer and sub-criterion layer), conduct consistency tests, and perform single-layer ranking:

[0130] 1 - 4 - 1) Calculate the maximum eigenvalue, eigenvector, and consistency index of each consistency matrix;

[0131] 1-4-2) Calculate the random consistency index and the consistency ratio based on several consistency indicators, and use the consistency indicator, random consistency index, and consistency ratio for consistency testing:

[0132] ① If the consistency ratio < 0.1, the consistency matrix passes the consistency test. Normalize each eigenvector to obtain the weight vector, and sort each evaluation index according to the weight vector;

[0133] ② If the consistency ratio ≥ 0.1, the consistency matrix fails the consistency test, and reconstruct the pairwise comparison matrix.

[0134] The consistency test result of the criterion layer is: CI: 0.05189928113244168, CR: 0.03931763722154672

[0135] Then the criterion layer passes the consistency test, and the weight vector of the criterion layer is:

[0136] a = [0.37433994 0.16341446 0.16341446 0.08467469 0.08467469 0.04433364 0.16341446]

[0137] Sub-criterion layer:

[0138] The consistency test result of the sub-criterion layer under B1 response time is: CI: 0.0, CR: 0.0,

[0139] Then the sub-criterion layer under B1 response time passes the consistency test, and the weight vector of the sub-criterion layer under B1 response time: [0.75 0.25];

[0140] The consistency test result of the sub-criterion layer under B2 thrust is: CI: 0.0, CR: 0.0,

[0141] Then the sub-criterion layer under B2 thrust passes the consistency test, and the weight vector of the sub-criterion layer under B2 thrust: [0.66666667 0.33333333];

[0142] The consistency test result of the sub-criterion layer under B3 usability is: CI: 0.0, CR: 0.0,

[0143] Then the sub-criterion layer under B3 usability passes the consistency test, and the weight vector of the sub-criterion layer under B3 usability: [0.25 0.75];

[0144] The consistency test result of the sub-criterion layer under B4 static characteristics is: CI: 0.0, CR: 0.0,

[0145] Then the sub-criterion layer under the B4 static characteristics passes the consistency test, and the weight vector of the sub-criterion layer under the B4 static characteristics: [0.66666667 0.33333333];

[0146] The consistency test result of the sub-criterion layer under the B5 dynamic characteristics is: CI: 0.0, CR: 0.0,

[0147] Then the sub-criterion layer under the B5 dynamic characteristics passes the consistency test, and the weight vector of the sub-criterion layer under the B5 dynamic characteristics: [0.66666667 0.33333333]

[0148] The consistency test result of the sub-criterion layer under the B6 maintainability is: CI: 0.009285714285714274, CR: 0.015975369458127903,

[0149] Then the sub-criterion layer under the B6 maintainability passes the consistency test, and the weight vector of the sub-criterion layer under the B6 maintainability: [0.53968254 0.30952381 0.15079365];

[0150] The consistency test result of the sub-criterion layer under the B7 satisfaction is: CI: 0.0, CR: 0.0

[0151] Then the sub-criterion layer under the B7 satisfaction passes the consistency test, and the weight vector of the sub-criterion layer under the B7 satisfaction: [0.25 0.75];

[0152] That is to say, the weight vectors of the sub-criterion layers are: b1 = [0.75 0.25], b2 = [0.66666667 0.33333333], b3 = [0.25 0.75], b4 = [0.66666667 0.33333333], b5 = [0.66666667 0.33333333], b6 = [0.53968254 0.30952381 0.15079365], b7 = [0.25 0.75].

[0153] 1 - 5) Calculate the combined weight vector, conduct a consistency test, and conduct a hierarchical total ranking;

[0154] 1 - 5 - 1) According to the constructed pairwise comparison matrix, calculate the maximum eigenvalue, eigenvector, and consistency index of each pairwise comparison matrix;

[0155] 1 - 5 - 2) Based on several consistency indices, calculate the random consistency index and the consistency ratio, and use the consistency ratio for combined consistency testing:

[0156] ① If the consistency ratio < 0.1, the hierarchical total ranking passes the consistency test. Calculate the combined weight vector of the scheme layer for the overall goal, and sort the various performance evaluation indicators of the scheme layer according to the combined weight vector.

[0157] ② If the consistency ratio ≥ 0.1, the hierarchical total ranking fails the consistency test. Reconsider the model or readjust the element values of the pairwise comparison matrix with a high consistency ratio.

[0158] Combined consistency index CI_combined: 0.0004119920373774074, combined random consistency index RI_combined: 0.58, combined consistency ratio CR_combined: 0.0007103310989265645, then the hierarchical total ranking passes the consistency test.

[0159] The combined weight vector is S = [0.28075496 0.09358499 0.108943 0.0544715 0.04085362 0.12256086 0.05644979 0.0282249 0.05644979 0.0282249

[0161] 0.02394134 0.01371913 0.00669573 0.04085362 0.12256086].

[0162] 1 - 6) Based on the combined weight vector and the fuzzy relation matrix, establish a judgment model matrix:

[0163] The data in the judgment model matrix is obtained according to the following formula:

[0164] I = S × R

[0165] Where I is the stretcher performance index in the judgment model matrix, S is the weight vector of the performance evaluation index, and R is the fuzzy relation matrix;

[0166] The performance index I of stretcher A = [0.24137149 0.40633433 0.35229418], indicating that the membership degree of stretcher A in "sub - optimal" is relatively prominent.

[0167] 1 - 7) Normalize the data in the judgment model matrix to obtain the membership degrees of the various performance evaluation indicators, forming the performance evaluation results of the prefabricated stretcher.

[0168] The performance index I of stretcher A is calculated to be in line with the normalization result itself, so no further normalization is required; if the calculation result does not conform to the normalization result, normalization processing is required.

[0169] It should be noted that the evaluation model matrix obtained in steps 1-6) contains three numbers corresponding to the evaluation levels (i.e., excellent, sub-excellent, and good) respectively. The values of these three numbers are the membership degrees corresponding to the three evaluation levels. The higher the membership degree corresponding to a certain level, the more the result conforms to a certain evaluation level. When the sum of the three values is not 1, it is necessary to normalize the data in the evaluation model matrix so that the sum of the three numbers in the evaluation model matrix is 1.

[0170] In this embodiment, according to the general performance standards, the reliability, safety, human-machine efficacy, electromagnetic compatibility, environmental adaptability, maintainability, etc. of the prefabricated stretcher entity model can be comprehensively evaluated and designed. The secondary and tertiary indicators under the primary indicators can follow the corresponding indicator items in the prefabricated stretcher performance evaluation model.

[0171] 2) Collect the entity data of the vehicle and the on-vehicle stretcher, and respectively construct the finite element simulation models corresponding to the vehicle entity and the on-vehicle stretcher entity (i.e., the vehicle finite element simulation model and the on-vehicle stretcher finite element simulation model);

[0172] 2-1) Collect the entity data of the target (a certain type) vehicle and the on-vehicle stretcher according to the following steps:

[0173] 2-1-1) Use devices such as cameras, video cameras, and infrared laser measuring instruments to record and survey the specific parameters and working conditions of the simulation target entities such as the vehicle body, the layout inside the cabin, the on-vehicle equipment and instruments, the stretcher structure, and the function operation of the target vehicle.

[0174] 2-1-2) Record and analyze the structure and use operation steps of the equipment and instruments, and analyze and infer the animation production process of the simulation target.

[0175] 2-1-3) Analyze the action phenomena during the unfolding and folding processes of the stretcher, clarify the operation connections between the components, and master the disadvantages of the existing stretcher, the structure of the modified stretcher entity model, and the requirements for the conversion of the working mode.

[0176] In this embodiment, by using the methods of on-site measurement and estimation, the overall appearance, front view, side view, top view, etc. of the equipment and components are taken as photos, which can be used as reference pictures for determining the contour features of the three-dimensional model during the construction process. This can reduce the difficulty of measurement and acquisition, reduce the workload and difficulty of modeling, and ensure that the appearance, size, contour features, internal composition, equipment components, and space layout of the established three-dimensional model have a high degree of similarity (realism). At the same time, the photos can be used as references for the texture materials and texture maps of the modeled objects to ensure the detailed features and simulated real effects of the model.

[0177] In this embodiment, when estimating the size of an object by means of an actual reference object with a size in a photo, the materials after photographing and filming can be uniformly classified and sorted, the unidentifiable points can be recorded and sorted out, and secondary supplementary shooting and reshooting can be carried out. For points that are difficult to measure, reference can be made to reference objects such as the instruction manual and drawings, such as the stretcher drawing (SolidWorks electronic version) and the part drawing (including the main section dimensions). However, when the photo does not match the drawing reference, the actual photo reference shall prevail.

[0178] 2-2) Construct a finite element simulation model of the vehicle-mounted stretcher and the vehicle:

[0179] 2-2-1) Use Autodesk 3DMax 3D modeling software to establish a feature model with the structural appearance characteristics of the vehicle-mounted stretcher and the target vehicle, and then make a fine model of the vehicle-mounted stretcher and the target vehicle according to the photo material in a 1:1 ratio.

[0180] 2-2-2) With the photo as a reference, use a combination of Photoshop, Substance Paint, and 3DMax to apply textures and add materials to the vehicle-mounted stretcher and the target vehicle.

[0181] In this embodiment, Autodesk 3DMax 3D modeling software, Substance Painter texture painting software, Unfold3D 3D model UV splitting software, etc. are all integrated in the Unity3D engine. It is possible to realize the establishment of a 3D model of the target vehicle and its vehicle-mounted stretcher, create bones for the stretcher model, set bone constraints, create weight maps, perform collision detection, perform animation binding, and perform animation testing. The established target vehicle and vehicle-mounted stretcher can fully display the structural composition of the stretcher and the vehicle body, and can meet the real-time simulation of the operation object in virtual simulation, the real-time simulation of the maintenance object in the virtual maintenance scenario, and support the user to complete the relevant information of human-computer interaction, support the movement of the virtual simulation object to be restricted by relevant components when performing running and disassembly operations, and support the corresponding data for relevant simulations of the virtual simulation object.

[0182] 2-2-3) Considering the limitations of the performance and storage space of the terminal device, as well as factors such as the reasonable allocation of resources, efficiency, and load during the virtual simulation operation, optimize the 3D models of the target vehicle and the vehicle-mounted stretcher.

[0183] In this embodiment, the three-dimensional models of the target vehicle and the on-vehicle stretcher are mainly processed by deleting redundant points, lines, and surfaces, invalid points, lines, and surfaces, reducing the number of model segments, adjusting the resolution of the texture file, and showing detailed features with textures. Then, the three-dimensional model is divided into multiple non-overlapping sub-models for export. For common model resources with the same appearance, such as walkie-talkies, seats, and vehicle tires, only one representative model can be selected during import.

[0184] 2-2-4) Perform mid-surface extraction, geometric cleaning, mesh generation, mesh quality inspection, definition of element and material properties, setting of connection relationships and loads, and assignment of element and material properties and boundary conditions to the three-dimensional models of the target vehicle and the on-vehicle stretcher. After debugging, a stretcher finite element simulation model that meets the calculation requirements is obtained.

[0185] In this embodiment, a hybrid modeling method combining geometric shape-based modeling technology and image-based modeling and rendering technology is used to construct the models of the target (a certain type) vehicle and the on-vehicle stretcher. It can vividly and intuitively reflect the different characteristics of the vehicle and the on-vehicle stretcher models from various angles while having a high sense of reality, and the fineness of the models can be adjusted as needed. It can achieve real-time rendering of large-scale scenes on ordinary computers. In addition, the same objects in the scene can use the same model, reducing the modeling workload. The models of each object can be displayed separately, which is conducive to the development of the interactive system.

[0186] 3) In the simulation experiment, adjust the on-vehicle stretcher finite element simulation model according to several prefabrication and modification schemes, and combine the adjusted multiple on-vehicle stretcher finite element simulation models with the vehicle finite element simulation model respectively to form several prefabricated stretcher finite element simulation models corresponding to each prefabrication and modification scheme.

[0187] In this embodiment, set the specific parameters and component materials of the stretcher and seat according to the prefabrication and modification scheme. When the components such as the stretcher and seat are dragged to the specified prefabricated hot spot position by the mouse and released, the components are added to the specified position in the three-dimensional scene. Then, set thresholds for each component through the parameter bar, and the parameters of each component can be adjusted within the threshold range. Finally, after all components are set, a prefabricated stretcher model can be comprehensively formed. These setting data will be saved and evaluated using the prefabricated stretcher performance evaluation model.

[0188] 4) Combine software such as Ansys Workbench and nCode, and evaluate the practicability of each prefabrication and modification scheme by using static characteristic analysis, dynamic characteristic analysis, fatigue life assessment, strength and stiffness checking methods. Record the performance index data of each prefabricated stretcher finite element simulation model during the evaluation process. The specific method of scoring each prefabricated stretcher finite element simulation model in combination with the prefabricated stretcher performance evaluation model is as follows:

[0189] 4-1) Establish several scenarios, each of which contains a different typical working condition, and place the finite element simulation models of each prefabricated stretcher under each typical working condition respectively;

[0190] In this embodiment, when performing static characteristic analysis, dynamic characteristic analysis, fatigue life assessment, strength and stiffness verification on the finite element simulation models of each prefabricated stretcher, each finite element simulation model of the prefabricated stretcher is in a fully loaded condition. At this time, both the upper and lower beds of the stretcher are in a loaded state (loaded with 220 kg). In this embodiment, the typical working conditions include horizontal bending, ultimate bending and torsion, braking, emergency turning, motor traction, stretcher tilting, bumpy vibration, etc.

[0191] 4-2) Adopt the vehicle finite element static analysis method to perform static characteristic analysis on the finite element simulation models of each prefabricated stretcher, and calculate and record the allowable stresses of the finite element simulation models of each prefabricated stretcher under each typical working condition respectively;

[0192] 4-2-1) Drive the finite element simulation models of each prefabricated stretcher to travel at a constant speed under each typical working condition respectively;

[0193] As Figure 14 shown, section Ⅰ is the horizontal bending condition and bumpy vibration road condition, section Ⅱ is the horizontal bending condition and bumpy vibration road condition, section Ⅲ is the ultimate bending and torsion condition and bumpy vibration road condition, section Ⅳ is the braking condition, and section Ⅴ is the emergency turning condition and bumpy vibration road condition.

[0194] In this embodiment, the finite element simulation model of the prefabricated stretcher (including the vehicle finite element simulation model and the stretcher finite element simulation model) travels at a constant speed on sections Ⅰ and Ⅱ (horizontal bending condition) shown in the figure. At this time, the road conditions are good, all wheels are on the ground, and it is basically affected by the braking force of symmetric vertical loads; when driving to section Ⅲ (ultimate bending and torsion condition) shown in the figure, the road conditions are irregularly uneven, and a certain wheel of the vehicle is in a suspended state, and it is basically affected by the braking force of asymmetric vertical loads; when braking on section Ⅳ (braking condition) shown in the figure, the influence of the longitudinal load braking force needs to be considered; when turning left or right on section Ⅴ (emergency turning condition) in the figure, the influence of the lateral load braking force (centrifugal force) needs to be considered; when driving on sections Ⅰ, Ⅱ, Ⅲ, and Ⅴ (bumpy vibration road conditions) shown in the figure, the vehicle body and stretcher system are in a bumpy vibration state, and the comprehensive influence of the real-time changes and combined actions of vertical loads, longitudinal loads, lateral loads, etc. needs to be considered. In addition, in the working condition where the stretcher is fully loaded and driven by the motor-driven slide to generate traction (motor traction condition), when lifting the wounded up and unloading them down (stretcher tilting condition), the longitudinal axis of the stretcher is in a state with a maximum inclination angle of 13.5 degrees of the upper frame.

[0195] 4-2-2) Collect the boundary conditions, loads, stress nephograms, and displacement diagrams of each finite element simulation model of the prefabricated stretcher under each typical working condition, and calculate and record the allowable stress of each finite element simulation model of the prefabricated stretcher under each typical working condition according to the boundary conditions, loads, stress nephograms, and displacement diagrams.

[0196] 4-3) Adopt the finite element modal dynamics analysis method to conduct dynamic characteristic analysis on each finite element simulation model of the prefabricated stretcher, and calculate and record the natural frequencies and vibration modes of each finite element simulation model of the prefabricated stretcher under each typical working condition.

[0197] In this embodiment, the main excitation frequencies include the excitation frequency generated by road surface unevenness (1.23 - 1.85 Hz), the excitation frequency generated by the engine idling (35 Hz), the excitation frequency generated by the transmission system (61.1 - 91.7 Hz), etc. The first 5 natural frequencies and their vibration modes of the prefabricated stretcher before and after optimization obtained from the free modal analysis are 3.39 - 50.22 Hz. The influence of its low-frequency response on the high-order modes is relatively small. Therefore, the first 5 natural modes of the stretcher are extracted for analysis and calculation, and optimization is carried out. The vibration modes of each order before and after optimization are as Figure 17 shown in Table 1.

[0198] Table 2 The first 5 natural frequencies and their vibration modes of the finite element simulation model of the prefabricated stretcher

[0199]

[0200] 4-4) Combine the fatigue analysis software nCode to conduct fatigue life assessment on each finite element simulation model of the prefabricated stretcher, and calculate and record the damage and life of each finite element simulation model of the prefabricated stretcher under each typical working condition.

[0201] The fatigue life refers to the number of cycles experienced by a material or structure from the start of bearing a load to the occurrence of fatigue failure under the action of an alternating load (also known as a cyclic load). In this embodiment, when the fatigue life exceeds 1.000E+7, it is considered that the life is infinite.

[0202] 4-4-1) According to the material characteristics of the prefabricated stretcher (the material of the prefabricated stretcher is Q235A), create the stress-life (S-N) curve (nCode DesignLife) of the prefabricated stretcher in Workbench Engineering data, as Figure 15 shown. In the figure, MPa represents the fatigue strength of the standard specimen of the material, and the corresponding value of MPa is the fatigue life calculated according to the number of cycles.

[0203] 4-4-2) By using CAE fatigue analysis technology, combining the stress and strain information provided by finite element analysis, and combining with the stress-life (S-N) curve of the prefabricated stretcher, the fatigue life distribution of components is accurately predicted by using fatigue theory and the five-frame model of fatigue analysis.

[0204] 4-4-3) By combining Miner's cumulative damage theory and the nCode DesignLife computer-aided software, the fatigue life of the prefabricated stretcher is calculated. The fatigue life under the horizontal bending condition can be obtained as 1.065E+07, the fatigue life under the ultimate bending and torsion condition is 2.652E+07, the fatigue life under the braking condition is 1.476E+07, the fatigue life under the emergency turning condition is 1.048E+07, the fatigue life under the motor traction condition is 1.052E+07, and the fatigue life under the stretcher tilting condition is 1.756E+07, all of which can meet the expected life requirements of the stretcher.

[0205] 4-5) In the static state, the specific methods for calculating and checking the stiffness and strength of each finite element simulation model of the prefabricated stretcher include:

[0206] 4-5-1) In each finite element simulation model of the prefabricated stretcher, the support arm of the stretcher is simplified into a cantilever beam in mechanics of materials, and the support frame of the stretcher is meshed by using the tetrahedral mesh division method. The size is set to 5 mm during meshing. The divided model has 572389 nodes and 289854 elements; load each finite element simulation model of the prefabricated stretcher:

[0207] 4-5-2) Calculate the bending moment normal stress and deflection value of the stretcher support arm in each finite element simulation model of the prefabricated stretcher respectively.

[0208] 4-5-3) According to the bending moment normal stress and deflection value calculated in step 4-5-2), judge whether the strength and stiffness of the stretcher support arm in each finite element simulation model of the prefabricated stretcher meet the requirements in the following way:

[0209] If the bending moment normal stress < the yield stress of the stretcher support arm material, the stiffness of the support arm meets the requirements;

[0210] If the bending moment normal stress ≥ the yield stress of the stretcher support arm material, the stiffness of the support arm does not meet the requirements;

[0211] If the deflection value < the deflection threshold, and the range of the deflection threshold is 10 - 11 mm, the strength of the support arm meets the requirements;

[0212] If the deflection value ≥ the deflection threshold, the strength of the support arm does not meet the requirements.

[0213] In this embodiment, the yield stress of the Q235 material for the support arm of the upper stretcher is 235 Mpa, and the safety factor is 3.2. The yield stress of the Q235 material for the support arm of the lower stretcher is 235 Mpa, and the safety factor is 2.19. According to the cross-sectional view of the support arm, as Figure 20 shown, calculate the bending moment normal stress and deformation of the support arms of the upper and lower stretchers of the prefabricated stretcher:

[0214] Support arm of the upper stretcher: Moment of inertia IZ = 440458×10E-12; Section modulus for bending resistance W = IZ / y = 14682E-9; The support arm is subjected to a uniform load q = 1100 / 0.57 = 1930 N / m; The support arm bears a bending moment M = 1100×1.965 / 2 = 1081 Nm; Bending moment normal stress σ = M / W = 73.6 Mpa; The deformation w of the support arm under the load = -FL3 / 3EIZ = -(1100×0.9833) / (3×216×10E9×440458×10E-12) = 3.79 mm.

[0215] Support arm of the lower stretcher: Moment of inertia IZ = 301152×10E-12; Section modulus for bending resistance W = IZ / y = 10038E-9; The support arm is subjected to a uniform load q = 1100 / 0.57 = 1930 N / m; The support arm bears a bending moment M = 1100×1.965 / 2 = 1081 Nm; Bending moment normal stress σ = M / W = 107.6 Mpa; The deformation w of the support arm under the load = -FL3 / 3EIZ = -(1100×0.9833) / (3×216×10E9×301152×10E-12) = 5.54 mm.

[0216] The bending moment normal stress of the support arm of the upper stretcher is 73.6 Mpa < 235 Mpa, and the deformation is 3.79 mm < the deflection threshold (10 - 11 mm). The strength and stiffness of the upper support arm of the prefabricated stretcher meet the design requirements;

[0217] The bending moment normal stress of the support arm of the lower stretcher is 107.6 Mpa < 235 Mpa, and the deformation is 5.54 mm < the deflection threshold (10 - 11 mm). The strength and stiffness of the lower support arm of the prefabricated stretcher meet the design requirements.

[0218] 4 - 5 - 4) Set constraints and loads on the stretcher support frames in each finite element simulation model of the prefabricated stretcher, and use the static analysis method to calculate the deformation and maximum equivalent stress of the stretcher support frames in each finite element simulation model of the prefabricated stretcher respectively;

[0219] In this embodiment, fixed constraints are applied to the positions where the side brackets are located, and the degrees of freedom in 6 directions are restricted respectively. A uniform force of 1930 N is applied to the 4 extended cross - beams (the length of the cross - beam is 983 mm) respectively, and it is uniformly distributed over a length of 570 mm. The application of constraints and loads on the support frame is asFigure 23 As shown. The calculated maximum deformation is 3.4 mm, which is located at the outer end of the lower stretcher support arm. The maximum equivalent stress of the support frame is 115 Mpa, which is located at the joint of the support arm and the side cabin wall frame, as Figure 24 shown.

[0220] 4-5-5) According to the deformation and maximum equivalent stress calculated in step 4-5-4), judge whether the strength and stiffness of the stretcher support frame of each prefabricated stretcher finite element simulation model meet the requirements in the following way:

[0221] If the maximum deformation ≤ deformation threshold, and the range of the deformation threshold is 8-9 mm, then the stiffness of the support frame meets the requirements;

[0222] If the maximum deformation > deformation threshold, then the stiffness of the support frame does not meet the requirements;

[0223] If the maximum equivalent stress ≤ the yield strength of the material, then the strength of the support frame meets the requirements;

[0224] If the maximum equivalent stress > the yield strength of the material, then the strength of the support frame does not meet the requirements.

[0225] In this embodiment, the maximum equivalent stress of the support frame is 115 Mpa < the yield stress of material Q235, which is 235 Mpa, and the maximum deformation is 3.4 mm < the deformation threshold (8-9 mm). The strength and stiffness of the support frame of the prefabricated stretcher meet the design requirements.

[0226] 4-5-6) Apply load to the cross-slide guide bearing pins, and calculate the shear stress of a single bearing pin in each prefabricated stretcher finite element simulation model respectively:

[0227] 4-5-7) According to the calculated shear stress of a single bearing pin, judge the shear strength check of the cross-slide guide bearing pins of each prefabricated stretcher finite element simulation model in the following way:

[0228] If the shear stress < the allowable shear stress of the material, then the shear strength of the cross-slide guide bearing pin meets the requirements;

[0229] If the shear stress ≥ the allowable shear stress of the material, then the shear strength of the cross-slide guide bearing pin does not meet the requirements;

[0230] When the stretcher is moved out along the cross-slide guide to the farthest distance from the side cabin wall, the self-weight of the wounded and the stretcher (total about 220 kg) is borne by 4 bearing pins in the slideway, and the shear strength of a single bearing pin needs to be checked. The stretcher end structure and the cross-slide guide are as Figure 22 shown, where the cross-slide guide is located in the middle of the stretcher bed and the support arm, and the diameters of the 4 bearing pins connecting the cross-slide guide and the stretcher bed are 25 mm and the lengths are 2.5 mm.

[0231] Then each bears a load of 550N, τ = 550 / (25*2.5) = 8.8Mpa ≤ 178Mpa (the allowable shear stress of 45 steel), and the cross - slide guide bearing pin meets the design requirements.

[0232] 4 - 6) Combining the allowable stress obtained in step 4 - 2), the natural frequency and vibration mode obtained in step 4 - 3), the damage and life obtained in step 4 - 4), and the stiffness and strength obtained in 4 - 5), the specific method for scoring each finite - element simulation model of the prefabricated stretcher using the prefabricated stretcher performance evaluation model includes:

[0233] 4 - 6 - 1) Normalize the performance - index data of each prefabricated stretcher performance evaluation model. See Tables 2 and 3 for details, and calculate the percentage of each performance - index data of the prefabricated stretcher performance evaluation model in the total sum of the corresponding prefabricated stretcher performance - index data;

[0234] Table 3 Secondary - index data of the finite - element simulation model of the prefabricated stretcher

[0235]

[0236] Table 4 Index - data conversion table of the finite - element simulation model of the prefabricated stretcher

[0237]

[0238] 4 - 6 - 2) Convert each percentage calculated in step 4 - 6 - 1) into an integer real number, and use it as the weighted score of each performance index of the prefabricated stretcher;

[0239] In this embodiment, the performance - index data of each prefabricated stretcher all rely on simulation experiments. In actual applications, more performance - index data can also be obtained through calibration experiments, expert evaluations, etc., and these performance - index data are incorporated into the consideration scope to further improve the evaluation accuracy. Among them, except for the three indicators of stretcher deployment time, retraction time, and total weight, the larger the value of other indicators, the better the effect. Special processing is required for these three indicators whose values are inversely proportional to the effect. In addition, for the decimal points that appear in calculating the proportion of stretcher indicators, three decimal places need to be retained and then converted into an integer.

[0240] 4 - 6 - 3) Combine the weighted scores calculated in step 4 - 6 - 2) with the prefabricated stretcher performance evaluation model, calculate the scores of each performance index of the prefabricated stretcher (including secondary - index and primary - index scores. See Tables 4 and 5 for details), sum up the scores of each performance index, calculate the total score of each prefabricated stretcher, and determine the superior - inferior grade.

[0241] In this embodiment, the primary indicators of the prefabricated stretcher are stretcher response time, stretcher usability, stretcher maintainability, satisfaction, stretcher dynamic characteristics, stretcher static characteristics, and stretcher thrust. Calculate the scores of each primary indicator respectively, and calculate the total score of the prefabricated stretcher according to the following formula:

[0242] Total score = stretcher response time score * stretcher response time proportion + stretcher usability score * stretcher usability proportion + stretcher maintainability score * stretcher maintainability proportion + satisfaction score * satisfaction proportion + stretcher dynamic characteristics score * stretcher dynamic characteristics proportion + stretcher static characteristics score * stretcher static characteristics proportion + stretcher thrust score * stretcher thrust proportion;

[0243] Table 5 Calculation of secondary indicator scores of stretcher A

[0244]

[0245] Table 6 Calculation of primary indicators and overall performance scores of stretcher A

[0246]

[0247] In this embodiment, Unity3D can also be used for processing and optimization. By adding operations such as light sources, skyboxes, audio effects, camera settings, and environmental scene loading, virtual simulation demonstrations of the appearance, layout, working process (such as the retraction and stop of the stretcher model), and evaluation results of the stretcher can be realized.

[0248] 5) Take the prefabricated stretcher finite element simulation model with the highest score as the optimal simulation model to form the vehicle-mounted stretcher plus the final modification plan. (In fact, take the prefabrication modification plan corresponding to the prefabricated stretcher finite element simulation model with the highest score as the vehicle-mounted stretcher plus the final modification plan)

[0249] The above are only the preferred embodiments of the present invention and are not used to limit the present invention. Any modifications made by those skilled in the art without departing from the spirit of the present invention fall within the protection scope of the present invention.

Claims

1. A method for screening and optimizing vehicle-mounted stretcher modification schemes, characterized in that: The following steps are involved: 1) Combining fuzzy evaluation algorithm and analytic hierarchy process, a prefabricated stretcher performance evaluation model is established; 2) Collecting the entity data of the vehicle and the vehicle-mounted stretcher, and constructing the finite element simulation models corresponding to the vehicle entity and the vehicle-mounted stretcher entity respectively; 3) In the simulation experiment, the vehicle-mounted stretcher finite element simulation model is adjusted according to a number of modification and prefabrication schemes, and the adjusted multiple vehicle-mounted stretcher finite element simulation models are respectively combined with the vehicle finite element simulation model to form a number of prefabricated stretcher finite element simulation models corresponding to each modification and prefabrication scheme; 4) Static characteristic analysis, dynamic characteristic analysis, fatigue life assessment, strength and stiffness verification are used to evaluate the practicality of each modification and prefabrication scheme, and the performance index data of each prefabricated stretcher finite element simulation model during the evaluation process are recorded, and each prefabricated stretcher finite element simulation model is scored in combination with the prefabricated stretcher performance evaluation model; 5) The prefabricated stretcher finite element simulation model with the highest score is used as the optimal simulation model to form the vehicle-mounted stretcher plus the final modification plan.

2. The method for screening and optimizing the modification scheme of the vehicle-mounted stretcher according to claim 1, characterized in that: In step 1), the specific method of establishing the prefabricated stretcher performance evaluation model by combining the fuzzy evaluation algorithm and the hierarchical analysis method includes: 1-1) In combination with actual needs, a hierarchical structure model of the stretcher performance evaluation index system is established, each performance evaluation index in the stretcher performance evaluation index system is used as an evaluation index set, and an evaluation level set is determined; 1-2) Using the trapezoidal distribution method, the membership function of each performance evaluation index is calculated, and a single factor fuzzy evaluation is performed on each performance evaluation index to establish a fuzzy relationship matrix; 1-3) Using the 1-9 scaling method, based on expert opinions or subjective judgments of decision makers, the relative importance of each performance evaluation index at the criterion level is compared pairwise, a pairwise comparison matrix is ​​constructed, and a consistency matrix is ​​obtained based on these pairwise comparison matrices; 1-4) Calculate the single-layer weight vector, perform consistency check, and perform hierarchical single sorting; 1-5) Calculate the combined weight vector, perform consistency check, and perform hierarchical total sorting; 1-6) Establishing a judgment model matrix based on the combined weight vector and the fuzzy relationship matrix; 1-7) The data in the evaluation model matrix is ​​normalized to obtain the degree of membership of each performance evaluation index and form the performance evaluation result of the prefabricated stretcher.

3. The method for screening and optimizing the modification scheme of the vehicle-mounted stretcher according to claim 2, characterized in that: In step 1-4), the single-layer weight vector is calculated and consistency check is performed. The specific method of performing hierarchical single sorting includes: 1-4-1) Calculate the maximum eigenvalue, eigenvector and consistency index of each consistency matrix; 1-4-2) Based on several consistency indicators, calculate the random consistency indicator and consistency ratio, and use the consistency indicator, random consistency indicator and consistency ratio to perform consistency test: ① If the consistency ratio is <0.1, the consistency matrix passes the consistency test, normalizes each feature vector to obtain a weight vector, and sorts each evaluation index according to the weight vector; ② If the consistency ratio is ≥ 0.1, the consistency matrix fails the consistency test and the pairwise comparison matrix is ​​reconstructed.

4. The method for screening and optimizing the modification scheme of the vehicle-mounted stretcher according to claim 2, characterized in that: In step 1-5), the combined weight vector is calculated and consistency check is performed. The specific method of performing the hierarchical total sorting includes: 1-5-1) According to the constructed pairwise comparison matrix, the maximum eigenvalue, eigenvector and consistency index of each pairwise comparison matrix are calculated; 1-5-2) Based on several consistency indicators, calculate the random consistency indicator and consistency ratio, and use the consistency ratio to perform combined consistency test: ① If the consistency ratio is <0.1, the total hierarchical ranking passes the consistency test, the combined weight vector of the solution layer for the total goal is calculated, and the performance evaluation indicators of the solution layer are ranked according to the combined weight vector; ② If the consistency ratio is ≥ 0.1, the hierarchical total ranking fails the consistency test. Reconsider the model or readjust the element values ​​of the pairwise comparison matrix with a high consistency ratio.

5. The method for screening and optimizing vehicle-mounted stretcher modification schemes according to claim 2, characterized in that: The data in the evaluation model matrix is ​​obtained according to the following formula: I=S×R Where I is the stretcher performance index in the evaluation model matrix, S is the weight vector of the performance evaluation index, and R is the fuzzy relationship matrix.

6. The method for screening and optimizing vehicle-mounted stretcher modification schemes according to claim 1, characterized in that: In step 4), the practicability of each modification and prefabrication scheme is evaluated by static characteristic analysis, dynamic characteristic analysis, fatigue life assessment, strength and stiffness verification, and the performance index data of each prefabricated stretcher finite element simulation model during the evaluation process are recorded. The specific method of scoring each prefabricated stretcher finite element simulation model in combination with the prefabricated stretcher performance evaluation model includes: 4-1) Establish several scenarios, each of which contains a different typical working condition, and place each prefabricated stretcher finite element simulation model under each typical working condition; 4-2) Using the whole vehicle finite element statics analysis method, the static characteristics of each prefabricated stretcher finite element simulation model are analyzed, and the allowable stress of each prefabricated stretcher finite element simulation model under each typical working condition is calculated and recorded respectively; 4-3) Using the finite element modal dynamics analysis method, the dynamic characteristics of each prefabricated stretcher finite element simulation model are analyzed, and the natural frequency and vibration mode of each prefabricated stretcher finite element simulation model under each typical working condition are calculated and recorded respectively; 4-4) Combined with fatigue analysis software, fatigue life assessment is performed on each prefabricated stretcher finite element simulation model, and the damage and life of each prefabricated stretcher finite element simulation model under various typical working conditions are calculated and recorded respectively; 4-5) Under static conditions, calculate and verify the stiffness and strength of each prefabricated stretcher finite element simulation model; 4-6) The allowable stress obtained in step 4-2), the natural frequency and vibration mode obtained in step 4-3), the damage and life obtained in step 4-4), and the stiffness and strength obtained in step 4-5) are used as performance index data of the corresponding prefabricated stretcher finite element simulation model, and each prefabricated stretcher finite element simulation model is scored using the prefabricated stretcher performance evaluation model.

7. The method for screening and optimizing the modification scheme of the vehicle-mounted stretcher according to claim 6, characterized in that: The specific method of using the prefabricated stretcher performance evaluation model to score each prefabricated stretcher finite element simulation model includes: 4-6-1) normalizing the performance index data of each prefabricated stretcher finite element simulation model, and calculating the percentage of each performance index data in the total performance index data of the corresponding prefabricated stretcher finite element simulation model; 4-6-2) converting each percentage calculated in step 4-6-1) into an integer real number and using it as the weight score of each performance index of the corresponding prefabricated stretcher finite element simulation model; 4-6-3) Combine the weighted score calculated in step 4-6-2) with the prefabricated stretcher performance evaluation model, calculate the scores of each performance index of the prefabricated stretcher finite element simulation model, sum up the scores of each performance index, calculate the total score of each prefabricated stretcher finite element simulation model, and determine the quality level.

8. The method for screening and optimizing vehicle-mounted stretcher modification schemes according to claim 6, characterized in that: In step 4-5), in a static state, the specific method of calculating and verifying the stiffness and strength of each prefabricated stretcher finite element simulation model includes: 4-5-1) In the finite element simulation model of each prefabricated stretcher, the arm of the stretcher is simplified to a cantilever beam of material mechanics, the support frame of the stretcher is meshed, and each prefabricated stretcher finite element simulation model is loaded; 4-5-2) Calculate the bending moment normal stress and deflection value of the stretcher arm in the finite element simulation model of each prefabricated stretcher; 4-5-3) According to the bending moment normal stress and deflection values ​​calculated in step 4-5-2), determine whether the strength and stiffness of the stretcher arms of each prefabricated stretcher finite element simulation model meet the requirements in the following manner: If the bending moment normal stress is less than the yield stress of the stretcher arm material, the stiffness of the arm meets the requirements; If the bending moment normal stress is ≥ the yield stress of the stretcher arm material, the stiffness of the arm does not meet the requirements; If the deflection value is less than the deflection threshold, the strength of the arm meets the requirements; If the deflection value is ≥ the deflection threshold, the strength of the arm does not meet the requirements; 4-5-4) setting constraints and loads for the stretcher support frames in the finite element simulation models of each prefabricated stretcher, and using static analysis to calculate the deformation and maximum equivalent stress of the stretcher support frames in the finite element simulation models of each prefabricated stretcher; 4-5-5) According to the deformation and maximum equivalent stress calculated in step 4-5-4), determine whether the strength and stiffness of the stretcher support frame of each prefabricated stretcher finite element simulation model meet the requirements in the following manner: If the maximum deformation is ≤ the deformation threshold, the stiffness of the support frame meets the requirements; If the maximum deformation > the deformation threshold, the stiffness of the support frame does not meet the requirements; If the maximum equivalent stress is ≤ the yield strength of the material, the strength of the support frame meets the requirements; If the maximum equivalent stress is greater than the yield strength of the material, the strength of the support frame does not meet the requirements; 4-5-6) Load the bearing pin of the traverse guide rail and calculate the shear stress of a single bearing pin in the finite element simulation model of each prefabricated stretcher; 4-5-7) Based on the calculated shear stress of a single bearing pin, the shear strength verification of the transverse guide bearing pins of each prefabricated stretcher finite element simulation model is determined in the following manner: If the shear stress is less than the allowable shear stress of the material, the shear strength of the traverse guide bearing pin meets the requirements; If the shear stress is ≥ the allowable shear stress of the material, the shear strength of the transverse guide bearing pin does not meet the requirements.

9. The method for screening and optimizing the modification scheme of the vehicle-mounted stretcher according to claim 8, characterized in that: The deflection threshold ranges from 10 to 11 mm.

10. According to the method for screening and optimizing modification schemes of a vehicle-mounted stretcher according to claim 8, the deformation threshold value is in the range of 8 to 9 mm.

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