Diesel engine maintainability virtual verification method and system based on complex model

Abstract

The invention provides a diesel engine maintainability virtual verification method and system based on a complex model. The method comprises the steps of maintainability verification demand analysis, verification scheme making, maintenance virtual prototype modeling, virtual verification execution and analysis and maintainability comprehensive evaluation. Through subsystem hierarchical division and disassembly sequence analysis, a check task is clear, a model and environment construction specification is formulated, a homologous multi-granularity lightweight model is adopted to construct a prototype containing virtual maintenance behaviors and disassembly sequence simulation, and dynamic analysis of spacing, collision, man-machine work efficiency and process is carried out in parallel. And after comprehensive evaluation, identifying design weak points and proposing improvement suggestions. According to the method, the design early-stage maintainability virtual verification is realized, the verification systematicness, accuracy and efficiency are improved, the cost is reduced, and the period is shortened.

Description

Technical Field

[0001] This invention relates to the field of diesel engine maintainability design and verification technology, and in particular to a method and system for virtual verification of diesel engine maintainability based on a complex model. Background Technology

[0002] As complex equipment, the maintainability design of diesel engines is crucial for ensuring reliable operation and reducing total lifecycle costs. Traditional maintainability design verification mainly relies on physical prototypes, which suffers from drawbacks such as long cycles, high costs, delayed problem detection, and difficulty in modification. While virtual verification technology offers a potential solution to these problems, existing solutions still have shortcomings in terms of the systematic nature of maintainability verification, the accuracy and efficiency of the verification process, and the comprehensive consideration of human-machine-environment factors. For example, there is a lack of unified model and environment construction standards, collision detection algorithms struggle to balance real-time performance and accuracy, the depth of human-machine ergonomics evaluation is insufficient, and the factors considered in the optimization of disassembly and assembly sequence planning are limited. Therefore, there is an urgent need for a systematic, efficient, and accurate virtual verification method for diesel engine maintainability to identify and resolve potential maintainability issues in the early stages of design. Summary of the Invention

[0003] The purpose of this invention is to provide a method and system for virtual verification of diesel engine maintainability based on a complex model. By constructing a systematic virtual verification process and integrating multiple analysis techniques and optimization algorithms, a comprehensive, efficient, and accurate virtual assessment of diesel engine maintainability can be achieved.

[0004] According to one objective of the present invention, the present invention provides a method for virtual verification of diesel engine maintainability based on a complex model, comprising the following steps: S1. Maintainability Verification Requirements Analysis: Perform subsystem hierarchical division, structural disassembly and assembly maintainability analysis, and disassembly and assembly sequence maintainability analysis for the diesel engine, and clarify maintainability indicators and verification tasks; S2. Maintainability Verification Plan Development: Based on the analysis results of S1, develop specifications for diesel engine model construction, maintenance environment construction, and virtual disassembly and assembly sequence development, and construct a virtual verification environment; S3. Maintenance Virtual Prototype Modeling: Based on the specifications established in S2, a maintenance virtual prototype is constructed, which includes virtual maintenance behavior simulation and virtual maintenance disassembly and assembly sequence simulation. S4. Virtual Verification Execution and Analysis: In the constructed virtual environment, drive the maintenance virtual prototype to execute the verification tasks determined in S1, and perform parallel spacing analysis, motion collision analysis, human-machine ergonomics analysis and maintenance process dynamic analysis to obtain maintainability assessment data. S5. Comprehensive Maintainability Evaluation: Based on the evaluation data obtained in S4, a comprehensive evaluation of the maintainability of the diesel engine is conducted to identify design weaknesses and propose improvement suggestions.

[0005] Furthermore, in step S1, the subsystem hierarchical division includes the division of functions, structures, working principles, performance requirements, and inter-interface relationships of the engine, fuel system, cooling system, lubrication system, intake system, and exhaust system; the disassembly and assembly sequence maintainability analysis includes steps such as disassembly and assembly information extraction, disassembly and assembly information model establishment, disassembly and assembly sequence generation, disassembly and assembly sequence optimization, and optimal sequence output.

[0006] Furthermore, in step S2, the virtual disassembly and assembly sequence development adopts the ant colony algorithm and uses the ant cycle model for global optimization; the virtual maintenance environment construction includes the construction of virtual maintenance scene, virtual maintenance personnel model, maintenance personnel posture model and maintenance tool model, and uses physically based rendering and Phong lighting model for material rendering and lighting processing.

[0007] Furthermore, in step S3, the virtual prototype modeling for maintenance adopts the same source multi-granularity lightweight model technology, which divides the model into four orders of magnitude: original model, high-level lightweight model, medium-level lightweight model and low-level lightweight model. The model simplification adopts the triangular edge collapse algorithm based on the quadratic error metric. The virtual maintenance disassembly and assembly sequence simulation adopts the hierarchical disassembly and assembly sequence planning method based on the unordered tree structure.

[0008] Furthermore, in step S3, the maintenance process model is constructed using a hierarchical Petri net, formally defined as U = {SP, P, T, F, H, M}, where SP is a finite set of all subnets, P is a finite set of all locations, T is a finite set of transitions, F is a set of directed arcs, H is the time corresponding to transition T, and M is the state function of the location.

[0009] Furthermore, in step S4, the motion collision analysis employs a hybrid collision detection algorithm that combines spatial decomposition with the OBB hierarchical bounding box method.

[0010] Furthermore, in step S4, the ergonomics analysis constructs an evaluation index system based on the analytic hierarchy process, and the evaluation indexes include joint motion factors and body balance of each kinetic chain.

[0011] Furthermore, in step S4, the spacing analysis includes calculating the minimum static spacing between the repair object, tools, and surrounding environmental components, and introducing a virtual human model to analyze operational accessibility; the dynamic analysis of the repair process includes simulating and verifying the rationality of the disassembly and assembly process, the applicability of the tools, the sufficiency of the operating space, and the comfort of the virtual human's movement by driving the virtual human to execute a repair operation sequence.

[0012] Furthermore, in step S5, the maintainability comprehensive evaluation comprehensively considers the spacing analysis results, collision detection results, human-machine ergonomics evaluation results, maintenance process time data, and logical correctness.

[0013] According to another objective of the present invention, the present invention provides a virtual verification system for diesel engine maintainability based on a complex model, comprising: The requirements analysis module is used to perform subsystem hierarchical division, structural disassembly and assembly maintainability analysis, and disassembly and assembly sequence maintainability analysis of the diesel engine, and to clarify maintainability indicators and verification tasks. The solution formulation module is used to formulate diesel engine model construction specifications, maintenance environment construction specifications, and virtual disassembly and assembly sequence development specifications based on the analysis results of the requirements analysis module, and to build a virtual verification environment; The prototype modeling module is used to construct a virtual maintenance prototype based on the specifications defined in the scheme development module, which includes virtual maintenance behavior simulation and virtual maintenance disassembly and assembly sequence simulation. The verification execution module is used to drive the maintenance virtual prototype to perform the verification tasks determined by the requirements analysis module in the constructed virtual environment, and to perform spacing analysis, motion collision analysis, human-machine ergonomics analysis and maintenance process dynamic analysis in parallel to obtain maintainability assessment data. The comprehensive evaluation module is used to comprehensively evaluate the maintainability of the diesel engine based on the evaluation data obtained from the verification execution module, identify design weaknesses, and propose improvement suggestions.

[0014] This invention replaces traditional physical prototype verification with virtual simulation technology, supporting maintainability verification in the early design stages, enabling parallel maintainability design and product design, and significantly shortening the development cycle. It reduces reliance on physical prototypes, lowering verification costs and the financial and time investment required for later design modifications. A systematic process is adopted, covering requirements analysis, scheme formulation, and prototype modeling, ensuring comprehensiveness and accuracy of verification. Layered disassembly and assembly, ant colony optimization, and hybrid collision detection technologies are introduced to improve verification efficiency and accuracy in complex scenarios. By comprehensively considering factors such as spacing, collision, and ergonomics, the evaluation results are more scientific, providing reliable guidance for diesel engine maintainability design and offering a reference for virtual verification of general quality characteristics of other complex equipment. Attached Figure Description

[0015] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0016] Figure 1 This is a flowchart illustrating the virtual verification method for diesel engine maintainability according to an embodiment of the present invention. Figure 2 This is a technical roadmap for the maintainability inspection requirements analysis research of this invention. Figure 3 A research technology roadmap was developed for the maintainability verification scheme of this invention. Figure 4 This is a schematic diagram of an unordered tree structure according to an embodiment of the present invention; Figure 5 This is a technical roadmap for research on virtual prototype modeling for maintenance in embodiments of the present invention. Detailed Implementation

[0017] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0018] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," and "counterclockwise," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting this invention.

[0019] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the stated features. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified. Furthermore, the terms "installed," "connected," and "linked" should be interpreted broadly; for example, they may refer to a fixed connection, a detachable connection, or an integral connection; they may refer to a mechanical connection or an electrical connection; they may refer to a direct connection or an indirect connection through an intermediate medium; and they may refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0020] Example 1 A virtual verification method for diesel engine maintainability based on a complex model includes the following steps: S1. Maintainability Verification Requirements Analysis: Perform subsystem hierarchical division, structural disassembly and assembly maintainability analysis, and disassembly and assembly sequence maintainability analysis for the diesel engine, and clarify maintainability indicators and verification tasks; S2. Maintainability Verification Plan Development: Based on the analysis results of S1, develop specifications for diesel engine model construction, maintenance environment construction, and virtual disassembly and assembly sequence development, and construct a virtual verification environment; S3. Maintenance Virtual Prototype Modeling: Based on the specifications established in S2, a maintenance virtual prototype is constructed, which includes virtual maintenance behavior simulation and virtual maintenance disassembly and assembly sequence simulation. S4. Virtual Verification Execution and Analysis: In the constructed virtual environment, drive the maintenance virtual prototype to execute the verification tasks determined in S1, and perform parallel spacing analysis, motion collision analysis, human-machine ergonomics analysis and maintenance process dynamic analysis to obtain maintainability assessment data. S5. Comprehensive Maintainability Evaluation: Based on the evaluation data obtained in S4, a comprehensive evaluation of the maintainability of the diesel engine is conducted to identify design weaknesses and propose improvement suggestions.

[0021] Specifically, in step S1, the subsystem convention level study includes the study of the functions, structure, working principle, performance requirements, and inter-interface relationships of the engine, fuel system, cooling system, lubrication system, intake system, and exhaust system. The disassembly / assembly sequence maintainability analysis includes steps such as disassembly / assembly information extraction, disassembly / assembly information model establishment, disassembly / assembly sequence generation, disassembly / assembly sequence optimization, and optimal sequence output.

[0022] Specifically, in step S2, the virtual disassembly and assembly sequence development adopts the ant colony algorithm, and the optimal ant cycle model is used for global optimization. In step S2, the virtual maintenance environment construction includes the construction of virtual maintenance scene, virtual maintenance personnel model, maintenance personnel posture model and maintenance tool model, and uses physically based rendering (PBR) and Phong lighting model for material rendering and lighting processing.

[0023] Specifically, in step S3, the virtual prototype modeling for maintenance employs a homogeneous multi-granularity lightweight modeling technique, dividing the model into four orders of magnitude: original model, high-level lightweight model, mid-level lightweight model, and low-level lightweight model. Model simplification utilizes a triangular edge collapse algorithm based on a quadratic error metric. The virtual maintenance disassembly and assembly sequence simulation employs a hierarchical disassembly and assembly sequence planning method based on an unordered tree structure.

[0024] In step S3, the maintenance process model is constructed using a hierarchical Petri net, formally defined as U = {SP,P,T,F,H,M}.

[0025] Specifically, in step S4, the motion collision analysis employs a hybrid collision detection algorithm combining spatial decomposition and OBB hierarchical bounding box methods. Ergonomics analysis uses the analytic hierarchy process (AHP) to construct an evaluation index system, assessing indicators including joint motion factors and body balance in each kinematic chain. Spacing analysis in step S4 involves calculating the minimum static spacing between the repair object, tools, and surrounding components, and introducing a virtual human model to analyze operational accessibility. Dynamic analysis of the repair process in step S4 includes simulating and verifying the rationality of the disassembly and assembly process, tool applicability, sufficiency of operating space, and virtual human movement comfort by driving a virtual human to execute a repair operation sequence.

[0026] Specifically, in step S5, the maintainability comprehensive evaluation should at least comprehensively consider the spacing analysis results, collision detection results, human-machine ergonomics evaluation results, maintenance process time data, and logical correctness.

[0027] Example 2 A virtual verification method for diesel engine maintainability based on a complex model includes the following steps: S1. Maintainability Inspection Requirements Analysis: First, analyze the subsystem convention hierarchy of the diesel engine to clarify the location, function, and interface of the fuel system and its filter sub-components; Then, a structural disassembly and maintainability analysis is conducted to assess the space available for accessing the filter, the tools required, and the ease of disassembly and assembly steps. Finally, maintainability analysis of the disassembly and assembly sequence was conducted to generate and optimize the optimal sequence for filter removal and installation. The maintainability metrics (such as accessibility and operation time) and specific verification tasks ("replacing the fuel filter") for this validation were determined.

[0028] S2. Development of a maintainability inspection plan: Based on the analysis in S1, detailed specifications were developed for the lightweight design of diesel engine CAD models (accuracy and format requirements), virtual maintenance environment (simulating a maintenance workshop scenario), virtual character model (ergonomically designed mechanic dimensions and degrees of freedom), and maintenance tool model (matching filter wrenches). Based on the complexity of the disassembly and assembly sequence, parameters for the ant colony algorithm (ant cycle model) were selected and configured for subsequent sequence planning.

[0029] S3, Virtual Prototype Modeling for Maintenance: a. Use specialized software to process the diesel engine CAD model (especially the fuel system section) into a lightweight model with homogeneous multi-granularity. For filters and surrounding components requiring detailed collision detection, use a high- or medium-level lightweight model; for distant background components, use a low-level lightweight model. Model simplification employs a triangular edge collapse algorithm.

[0030] b. Construct a virtual maintenance scenario (workshop), a virtual repairman model, and a filter wrench tool model.

[0031] c. Decompose the "replace fuel filter" task based on the hierarchical idea (unordered tree structure) and plan the sub-task sequence.

[0032] d. Establish the process model U = {SP, P, T, F, H, M} for the maintenance task using hierarchical Petri nets, and define maintenance resources (tools, spare parts), personnel behavior, tool behavior, state transition logic, and time constraints.

[0033] e. Configure PBR materials and lighting for the scene to create a realistic visual environment.

[0034] S4. Virtual Verification Execution and Analysis: In a virtual environment, a virtual mechanic is driven to perform the complete operation of "replacing the fuel filter".

[0035] Spacing analysis: Static calculation of the minimum spacing between the virtual repairman, wrench, filter, and surrounding components to determine whether the operating space is sufficient.

[0036] Motion collision analysis: During the movement and operation of the virtual mechanic, a hybrid algorithm of spatial decomposition and OBB hierarchical bounding box is used to detect in real time whether interference collisions occur between the mechanic, tools, filters, and other diesel engine components.

[0037] Ergonomics analysis: Record the joint angles and body postures of the virtual repairman during operation, and evaluate the operation comfort and fatigue based on the comfort evaluation model constructed by the analytic hierarchy process, and identify unreasonable postures.

[0038] Dynamic analysis of the maintenance process: Observe the continuity of the entire maintenance process, check whether the tools can be used smoothly, whether the sequence logic is correct, and verify the consistency of the process logic through a Petri net model. Record the time of each step.

[0039] S5. Overall Maintainability Evaluation: Collect all analysis data from S4: whether the spacing meets requirements, whether collisions occur, ergonomics score, time for each step, and correctness of process logic. Use this data to evaluate the maintainability of the "fuel filter replacement" task. For example, if insufficient tool operating space is found (poor spacing analysis results), collisions occur during disassembly, or the mechanic's posture is awkward (low ergonomics score), then the maintainability design of that part is deemed flawed, and improvement suggestions are proposed (such as changing the filter installation position or optimizing the surrounding layout).

[0040] The above embodiments demonstrate that the method of the present invention can systematically, effectively, and accurately complete the virtual verification of specific maintenance tasks for diesel engines, providing an intuitive and quantitative basis for design improvement.

[0041] Example 3 This embodiment, in conjunction with the accompanying drawings, provides a detailed description of the specific implementation of the present invention. The diesel engine maintainability virtual verification addresses the issues of smooth and efficient diesel engine maintenance processes, improved equipment reliability and service life, and reduced maintenance costs. By combining virtual simulation technology, maintainability verification work is carried out in a virtual environment, providing a convenient, efficient, and feasible technical path for future maintainability verification.

[0042] like Figure 1 As shown, the technical solution of this embodiment mainly focuses on three aspects: maintainability verification requirements analysis, maintainability verification plan formulation, and virtual maintenance prototype modeling. A method for virtual verification of diesel engine maintainability based on a complex model includes the following steps: Step 1: Maintainability Inspection Needs Analysis and Research (1) Research Content 1.1) Research on the Conventional Hierarchy of Diesel Engine Subsystems The study of subsystem conventions in diesel engines examines the relationships and conventions between different subsystems within the overall diesel engine system. The research objects include the mechanical linkages, installation, and assembly relationships between the engine, fuel system, cooling system, lubrication system, intake system, and exhaust system. This convention-level study provides a detailed analysis and description of the function, structure, working principle, and performance requirements of each subsystem. Simultaneously, it also studies the interfaces and conventions between different subsystems, clarifying their collaborative working mechanisms. Through the study of diesel engine subsystem conventions, a better understanding of the overall structure and working principle of diesel engines can be achieved, providing important references for diesel engine repair and maintenance. Specific research content is as follows: Subsystem Function Description: A functional description of the diesel engine's subsystems, including their main functions, roles, and objectives. For example, the engine subsystem is responsible for generating power, and the fuel system is responsible for supplying fuel. Subsystem structure analysis: This involves analyzing the structure of a subsystem, including the function and interrelationships of its components. For example, the engine subsystem includes components such as the cylinder block, pistons, and crankshaft.

[0043] Subsystem Working Principles: In-depth study of the working principles and processes of subsystems, including principles of energy conversion, combustion, and fluid transfer. For example, the working principle of a fuel system includes processes such as fuel supply, injection, and mixing.

[0044] Subsystem performance requirements: Define the performance indicators and requirements of the subsystem, including requirements for power output, fuel efficiency, and emission standards. Studying these performance requirements can guide the system's maintenance and repair schedule. Subsystem interfaces and conventions: This section studies the interfaces and conventions between different subsystems to ensure the mechanical principles underlying their coordinated operation. For example, the fuel supply interface connection between the engine subsystem and the fuel system.

[0045] 1.2) Structural disassembly and maintainability analysis and research Structural disassembly and maintainability analysis involves in-depth research and evaluation of the diesel engine's structure to determine the ease, efficiency, and reliability during disassembly, assembly, and maintenance. Specific research content is as follows: Structural analysis: Analyze the overall structure of the diesel engine, including the location, connection method, and fixing method of its components. Clarify the correlation and dependency relationships between the various components and determine the complexity of the structure. Disassembly and Assembly Analysis: Assess the ease of disassembly and assembly of the diesel engine, including the steps and tool requirements. Analyze potential difficulties in disassembly and assembly, and identify areas for improvement. Identify key steps in the disassembly and assembly process and propose suggestions to improve operational efficiency.

[0046] Maintainability analysis: Assess the vulnerable parts, repair difficulty, and repair time of the diesel engine during maintenance. Identify components prone to failure or requiring routine maintenance. Analyze potential problems during maintenance, such as the selection of repair tools and the required repair techniques.

[0047] 1.3) Maintainability Analysis of Disassembly and Assembly Sequence Disassembly and assembly are divided into disassembly and assembly. Disassembly and assembly are relative to assembly. Assembly is the process of establishing constraints between parts, while disassembly and assembly is the process of eliminating those constraints. A disassembly and assembly sequence refers to the process of generating a sequence of parts that meets certain constraints based on information such as the diesel engine's structure and assembly relationships. Each disassembly and assembly method corresponds to a disassembly and assembly sequence. During the disassembly and assembly process, it is permissible to damage certain non-critical parts during disassembly and assembly, a situation not allowed in assembly. The purpose of the disassembly and assembly sequence is to use available information and certain analytical methods, with the optimization objective as the criterion, to find an optimal sequence suitable for the virtual disassembly and assembly of a diesel engine. Therefore, the disassembly and assembly sequence of a diesel engine can generally be divided into the following steps: Extraction of disassembly and assembly information: Based on the assembly relationship between diesel engine components, including the topological structure and spatial position of the components, extract the information required for product disassembly and assembly sequence planning.

[0048] Establishment of the disassembly and assembly information model: The disassembly and assembly information model is the carrier of diesel engine disassembly and assembly information, laying the foundation for the generation of subsequent disassembly and assembly sequences.

[0049] Generation of disassembly and assembly sequence: Based on certain theoretical methods, the disassembly and assembly information model is analyzed and calculated to solve the disassembly and assembly sequence of the diesel engine.

[0050] Optimization of the disassembly and assembly sequence: The obtained sequence is optimized according to the disassembly and assembly objectives.

[0051] Output the optimal disassembly and assembly sequence.

[0052] (2) Technical approach to maintainability verification requirements analysis like Figure 2 As shown, the maintainability verification requirements analysis specifically includes: 1) Maintainability Index Analysis Maintainability analysis refers to the process of building a digital maintenance simulation environment based on digital information during the design phase, and modeling and simulating the maintenance process in the maintenance simulation environment to obtain data on the interaction between "human-machine-environment" during the maintenance process. Based on maintainability design criteria and human factors and ergonomics standards, maintainability analysis and human factors and ergonomics analysis are carried out to identify existing problems in advance.

[0053] Maintainability index analysis mainly includes the following aspects: a) Good maintenance accessibility Maintenance accessibility refers to the relative ease with which different components of a product can be accessed during maintenance, or the ease with which the parts need to be repaired. There are two main measures to achieve product accessibility: first, to rationally position each part and provide adequate space for maintenance operations, including space for applicable tools; and second, to provide pathways that facilitate observation, inspection, maintenance, and repair.

[0054] b) Improve standardization and interchangeability Standardization, interchangeability, and generalization not only benefit product design and production, but also simplify product maintenance, significantly reduce the variety and quantity of maintenance parts, and greatly shorten maintenance time.

[0055] c) It has comprehensive error prevention measures and identification markings. If there are no error prevention measures and identification marks in the product design, errors such as incorrect installation, reverse installation or omission of parts with similar appearance and size often occur during maintenance. Procurement, storage and safekeeping are also prone to errors.

[0056] d) Ensure maintenance safety Safety in the context of maintainability refers to a design feature that prevents personal injury or equipment damage during maintenance activities. It is more complex and involves more issues than safety during use, requiring not only safety during use but also safety during storage, transportation, maintenance, and repair.

[0057] e) Good testability Testability is a design feature of a product that facilitates the determination of its condition and the detection and diagnosis of faults. Once the faulty part is identified, replacing the part usually resolves the problem. Therefore, the selection of testing equipment and methods, as well as the configuration of testing points, are important considerations for maintainability.

[0058] f) Repairability requirements for valuable components Valuable components should possess properties that facilitate repair of the original component after it has worn, deformed, or otherwise failed. Practice has shown that repairing valuable components not only saves maintenance resources and costs but also plays a crucial role in improving equipment availability.

[0059] g) Reduce maintenance content and lower maintenance skill requirements Reduce maintenance items and lower failure rates by designing products with structures that require little or no preventative maintenance to reduce maintenance workload.

[0060] h) Meets the human-machine-environment engineering requirements for maintenance. Human-machine-environment engineering in maintenance studies the relationship between various human abilities (physical strength, sensory abilities, endurance, etc.), body dimensions, and equipment during equipment maintenance, as well as how to improve maintenance efficiency and quality and reduce personnel fatigue. Good working posture, low noise, good lighting, suitable tools, and appropriate workload can improve the quality and efficiency of maintenance work, making it an indispensable aspect of maintainability design.

[0061] 2) Verification Task Analysis Diesel engine inspection tasks primarily refer to diesel engine maintenance tasks, including routine maintenance, inspection, testing, parts replacement, and troubleshooting. Simultaneously, it's necessary to analyze the installation and disassembly of complex tooling during maintenance work, such as the replacement of core diesel engine components, based on actual conditions. The accuracy of the simulation of the inspection task, based on the above, impacts the ergonomics performance evaluation results.

[0062] Step 2: Development and Research of Maintainability Verification Plan (1) Research Content 2.1) Research on the Standardization of Diesel Engine Model Construction The research on diesel engine model construction specifications studies the specifications and standards that must be followed during the establishment of diesel engine data models. A diesel engine data model is a model used to describe and represent its shape, structure, and properties. The following are the contents of the data model construction specification research: The model construction has a clear purpose: to define the application objectives of the diesel engine data model, including engineering design, simulation analysis, and teaching demonstrations. Different application scenarios require the creation of different types of 3D engine models.

[0063] Determining the scope of model building: Determine the modeling scope of the data model, including the accuracy requirements, spatial range, attribute information, etc.

[0064] Model building methods: The research employs 3D data modeling methods, including CAD software-based modeling, parametric modeling, and solid modeling. Choosing an appropriate modeling method can better represent the shape and structure of 3D objects.

[0065] Model Accuracy and Precision: This section investigates how to ensure the accuracy and precision of the data model, including accurately acquiring engine geometric parameters and material properties, and error control during data processing and modeling. Model Standards and Formats: This section studies the standards and formats for 3D data models, such as STL, OBJ, and STEP, to ensure that the model can be exchanged and shared across different platforms and software.

[0066] 2.2) Research on the Construction Standards for Diesel Engine Maintenance Environment Virtual maintenance operations need to be conducted in a virtual environment. Constructing a virtual environment makes the simulation process more realistic and effective; the more realistic the environment, the more reliable the simulation results. Generally, the construction of a virtual maintenance environment includes modeling the virtual maintenance scenario, personnel, postures, and tools.

[0067] Virtual maintenance scenario model construction: A virtual maintenance scenario refers to the environment in which a diesel engine is disassembled and assembled. It differs from the diesel engine model and tool models, representing only the environmental information surrounding the diesel engine during disassembly and assembly, including the factory building and equipment. In the virtual disassembly and assembly process, the maintenance scenario is typically a hangar or workshop, and tool models and personnel models will also operate within this environment.

[0068] Virtual Maintenance Human Model: The construction of the human body model is an important part of the virtual simulation process. During disassembly and assembly simulations, the human body is required to perform these actions. Human ergonomic analyses, such as accessibility, visibility, and comfort, also require the human body model. By adjusting the degrees of freedom of the human body model, various human postures can be accommodated, achieving realistic joint movements and constraints.

[0069] Maintenance personnel posture model: Maintenance personnel posture refers to the state and posture of the human body model when performing virtual maintenance operations. Designing the personnel posture that may occur during the disassembly and assembly simulation before maintenance operations can facilitate maintenance simulation verification.

[0070] Maintenance tool models: Maintenance tool models are also an indispensable part of virtual maintenance simulation operations. The disassembly and assembly of diesel engine parts requires maintenance personnel to use tools. The maintenance tool models must be constructed according to the disassembly and assembly sequence requirements.

[0071] 2.3) Research on Virtual Disassembly and Assembly Sequence Development Specifications Ant colony optimization (ACO) is an algorithm that mimics the foraging process of ants in nature. There are three main models in ACO: ant count, ant density, and ant week. The main difference between these three models lies in the amount of pheromone left behind by ants when they traverse a certain path at a given time. Compared to the local update method of pheromone in the first two models, the ant week system uses a global update method. Experiments show that the ant week model yields better results than the other two models, so it is more widely used in ACO. The basic ACO algorithm generally involves six steps to solve the problem: Initialize variable parameters: Set parameter values ​​according to requirements.

[0072] Determining the initial position: Set the initial position for each ant.

[0073] Determining the probability function: The probability function is the basis for ants to choose their path.

[0074] Record the iteration path: Record the ant positions for subsequent optimization.

[0075] Updating information elements.

[0076] Clear the taboo list, iterate again, and output the result after reaching the maximum number of iterations.

[0077] (2) Technical approach like Figure 3 As shown, the development of a maintainability verification plan includes: 1) Spacing Analysis Spacing analysis, as part of static analysis, calculates the minimum distance between the LRU and its fixing bolts and surrounding components, based on the spacing of the digital prototype itself, to determine whether the surrounding space meets the disassembly and assembly requirements. Additionally, a virtual human with a fixed operating posture can be added to analyze the accessibility of the operating space.

[0078] 2) Motion Collision Analysis In maintainability analysis, motion collision detection mainly refers to interference checks between equipment subsystems and components, collision checks between subsystem components and external components to ensure that there are no conflicts in the disassembly and assembly of each subsystem component, and collision detection between personnel, maintenance tools, and the maintenance environment during the maintenance process.

[0079] Because maintainability analysis introduces maintenance tools and personnel, it needs to consider factors such as maintenance accessibility, operating space, and maintenance paths. Furthermore, due to the complexity of the systems involved in maintainability analysis and the numerous components they contain, it places high demands on collision detection algorithms: they need to detect collisions in real time, requiring high real-time performance; simultaneously, to accurately detect collisions and calculate their locations, high accuracy is also required. However, as the research in previous chapters has shown, a single collision detection algorithm cannot adequately balance the relationship between real-time performance and accuracy.

[0080] Considering that most components are stationary during maintainability analysis, spatial decomposition can pre-divide the space into cells, determining the cells occupied by each component. When maintenance tools or components move, only the cells occupied by these moving components need to be recalculated, significantly reducing the amount of data to be inspected and improving efficiency. Furthermore, experience shows that OBB hierarchical bounding box detection has high accuracy. Therefore, this solution employs a hybrid collision detection algorithm combining spatial decomposition and OBB hierarchical bounding box methods, leveraging the advantages of both to achieve the required real-time performance and accuracy.

[0081] 3) Ergonomics Analysis In the study of repair design and maintenance process analysis, the purpose of ergonomic evaluation is to optimize human working postures to meet the requirements of maintenance work and personnel safety in confined spaces. Improving the comfort of human behavior is essentially about optimizing limb posture, which is related to the human joint movement system. The human movement system, through muscle contraction and relative joint rotation, causes limbs to deviate from anatomically neutral postures. Muscle contraction in the movement system causes fatigue, resulting in uncomfortable human behavior. The fatigue caused by muscle contraction is closely related to joint movement; the fatigue level of muscle contraction can be determined by the joint rotation angle. From an ergonomic perspective, the movement of human joints has certain angular limits; extreme states can cause discomfort and even musculoskeletal damage. When the human body is in various comfortable postures, the joints are within a certain comfortable angle range. As the joint rotation angle gradually increases, the muscle contraction force driving joint movement increases, leading to increased biomechanical fatigue and a decrease in limb comfort caused by joint movement.

[0082] In the study of human behavioral comfort assessment, this invention focuses on analyzing joint motion factors and joint balance conditions related to human biomechanics. The invention proposes to establish vector expressions for the behavioral states of each kinetic chain, thereby decomposing the assessment factors of human behavioral comfort into several levels, and using the analytic hierarchy process (AHP) to construct the hierarchical relationship of the indicators. In the human comfort assessment indicator system, human behavioral comfort serves as the target layer of the evaluation system, representing the comprehensive evaluation objective of human behavioral comfort. Below the target layer is the criterion layer for comfort evaluation, where the evaluation indicators are the joint motion factors of each kinetic chain, providing a specific description of the human behavioral state. Below the criterion layer is the indicator layer of the entire evaluation system, which refines the joint degrees of freedom indicators. Since the lower limbs are the parts that support and coordinate body balance, the indicator factors of the lower limb kinetic chain also include the body's balance status, and the assessment of joint degrees of freedom is divided into two cases: balance and imbalance.

[0083] 4) Dynamic analysis of the maintenance process The process of repairing parts is simulated by creating a virtual human to simulate the disassembly and assembly of parts. During the simulation, the rationality of the disassembly and assembly process, the suitability of the tools, the availability of sufficient operating space, and the comfort evaluation and analysis of the virtual human's movement are also examined.

[0084] Based on current technological conditions, maintenance virtual inspections should primarily rely on static analysis in practice, supplemented by dynamic analysis.

[0085] Step 3: Research on Virtual Prototype Modeling for Maintenance (1) Research Content 3.1) Research on Virtual Maintenance Behavior Simulation Virtual maintenance behavior simulation research models human maintenance actions by decomposing maintenance tasks and classifying maintenance activities, thereby enabling convenient control of virtual humans to perform specified maintenance tasks. The decomposition of maintenance tasks and the classification of maintenance actions are the foundation for realizing maintenance activity simulation. Maintenance actions for maintenance process simulation can be divided from top to bottom into task-independent action elements, action units related to general semantics, and task-oriented work units, thus forming a maintenance task decomposition model.

[0086] Action elements are usually classified according to the human joint chain and degrees of freedom of movement. They are generally a continuous motion trajectory involving several joints, with some maintenance semantics, but are basically not related to task semantics.

[0087] An action unit is generally composed of several action elements according to certain semantic rules. These semantics belong to the general description of human body maintenance activities and are not related to specific tasks.

[0088] A work unit, or simply a work, is constructed based on motion elements and motion units for a specific domain task. A work unit describes the collective maintenance activities performed by a human model over a period of time to achieve a relatively small maintenance goal. These maintenance goals can be obtained by decomposing specific maintenance tasks.

[0089] 3.2) Simulation Study of Virtual Maintenance Disassembly and Assembly Sequence Virtual maintenance disassembly and assembly sequence simulation research focuses on disassembly and assembly methods for complex structural products. Disassembly and assembly are crucial steps in virtual maintenance support for complex products, directly impacting their disassembly and assembly capabilities, quality, and cost. This research on disassembly and assembly sequence planning technology for complex products in virtual maintenance primarily employs a hierarchical approach to simplify the complex product. Disassembly and assembly sequences are planned for each decomposed level, and then nested and merged into a complete disassembly and assembly sequence for the complex product. This effectively improves the disassembly and assembly process of complex products and enhances the quality of maintenance support.

[0090] Layering of complex products For complex products with numerous parts and complex structures, the first step is to divide them into several independent assembly / disassembly components to improve the parallelism and mechanization of assembly and disassembly. For a specific complex product, an unordered tree structure is used to visually represent the hierarchical model data structure. As shown in the diagram below, each pair of dashed lines represents a layering step. First, the assembly is divided into components or parts, then the corresponding components are further divided into components or parts in the next layer, and so on until no further division is possible.

[0091] like Figure 4 As shown, the unordered tree structure used to represent the data structure of a part hierarchical model has two advantages: The clear structural relationships of the structure tree make it easy to compile the process structure tree when performing virtual maintenance simulation, which can improve efficiency.

[0092] In terms of planning the disassembly and assembly sequence for complex products, one can start from the bottom of the tree structure and plan the disassembly and assembly sequence for each part or component in each independent dashed box. Then, one can plan the disassembly and assembly sequence for each part or component in each independent dashed box upwards. Finally, by sorting the parts and components from top to bottom through hierarchical nesting, the disassembly and assembly sequence of the entire product can be obtained, thus simplifying the originally complex problem.

[0093] Analysis of factors influencing the disassembly and assembly scheme When selecting factors influencing the disassembly and assembly sequence, we analyze these factors from the perspectives of shortening disassembly and assembly time and reducing costs, determining the degree of influence of each factor, and then determining a suitable solution. To comprehensively reflect the advantages and disadvantages of the disassembly and assembly sequence, we mainly study the following key influencing factors that need to be considered when evaluating the disassembly and assembly sequence scheme.

[0094] Number of changes in assembly / disassembly direction: Reducing the number of changes in assembly / disassembly direction during the assembly / disassembly process can reduce reversal operations and shorten assembly / disassembly time. Since the product assembly structure and assembly / disassembly process are generally expressed in the Cartesian coordinate system XYZ, it is assumed that the assembly / disassembly operations of parts are carried out along six directions: +X, -X, +Y, -Y, +Z, and -Z. Based on the interference matrix of the assembly, the assembly / disassembly direction of each part in the assembly / disassembly sequence is inferred to determine whether the sequence is geometrically feasible; if at least one part in the sequence is infeasible in all six assembly directions, the assembly / disassembly sequence is determined to be infeasible; otherwise, it is a feasible sequence.

[0095] Assembly stability refers to the ability of two sub-assemblies involved in an assembly operation to maintain their internal assembly relationships under the influence of gravity and the forces required to establish the assembly. It directly affects the reliability of disassembly and assembly operations, as well as the complexity of fixtures and tools. To quantify the stability of feasible disassembly and assembly sequences, this paper uses a stable adjacency matrix A to describe the connection relationships between components in the product. Stable connections here refer to connections that impose mandatory constraints on the mutual movement of parts, such as threaded connections, interference fits between shafts and holes, O-ring connections, and snap ring connections.

[0096] The stable proximity matrix A is specifically represented as follows:

[0097] In the formula:

[0098] For a given disassembly and assembly sequence, starting from the first part of the sequence, if there is a stable contact relationship between the next two parts, add 2; if there is a contact connection relationship, add 1; if there is no connection relationship, add 0. That is, simply add the value of the corresponding stable adjacency matrix. The final accumulated value is represented by V2 (0≤V2≤2N-2).

[0099] Tool Change Count: The number of tool changes during product assembly and disassembly should be minimized to improve efficiency. At the outset of assembly and disassembly planning, the tools for each part are predefined, thus determining the corresponding tool sequence for a given product assembly and disassembly sequence. This paper proposes using a tool transformation matrix B (N*N dimensional) to represent this, as follows:

[0100] In the formula:

[0101] Therefore, for a given disassembly and assembly sequence, the calculation method for the number of disassembly and assembly tool changes is similar to the conversion method of V2, and the final calculated number of disassembly and assembly tool changes is represented by V3.

[0102] (2) Technical approach like Figure 5 As shown, the research roadmap for virtual prototype modeling in maintenance. 1) Homogeneous multi-granularity lightweight model During the virtual assembly simulation of aircraft, the functions of each component are different, and the requirements for its model information are also different. The models involved in the assembly can be divided into four levels: original model, advanced lightweight model, intermediate lightweight model, and low-level lightweight model.

[0103] a) The original model refers to a model that contains complete information about the components. For example, when performing product pre-assembly analysis, if only static interference checks are performed, the original model can be used.

[0104] b) Advanced lightweight models are lightweight models that include model entity information and auxiliary entity features, such as digital models of moving parts. They need to have certain assembly paths created and need to include some auxiliary entity features necessary for path planning. Therefore, lightweight models that include auxiliary entity features are required.

[0105] c) The intermediate lightweight model is a lightweight model that only contains model entity information. For example, if it is only used as a component model in the assembly environment and is only used to check whether there is interference with moving components, a lightweight model that only contains entity information can be used.

[0106] d) Low-level lightweight models simplify the internal structure by retaining only the external contour entity information of the component digital model. For example, in the assembly of parts and the overall assembly, the internal structure of the component has little impact on the assembly simulation process. The assembly simulation process only needs the external contour entity information of the component. Therefore, its internal structure can be simplified accordingly, removing the entity information of the internal parts and retaining only the assembly information of the parts.

[0107] For model meshing, this scheme employs a triangular edge collapse algorithm, also known as Quadric Error Metric Simplification, which simplifies triangular mesh models. Its principle is to continuously perform edge collapse operations on the original model until the desired simplification level is achieved. Specifically, the algorithm first calculates the quadratic error matrix for each vertex and adds it to the error matrices of adjacent triangles to obtain the error matrix for each edge. Then, for each edge, the vertex with the smallest error between its two endpoints is selected for collapse, while simultaneously updating the vertex information and error matrices of adjacent triangles. By continuously performing edge collapse operations, the model can be gradually simplified, reducing the number of vertices and triangles while preserving the model's shape and topological features. This algorithm demonstrates good performance in both computational speed and simplification effect and is widely used in the optimization and compression of 3D models.

[0108] 2) Layered assembly and disassembly in complex scenarios The essence of hierarchical assembly scenarios is to break down a complex assembly scenario into several simpler ones, and then perform assembly simulations accordingly, thus distributing the high demands of the complex assembly scenario on computer hardware performance. The principles for breaking down complex assembly scenarios include: a) Product assembly hierarchy breakdown. Product assembly hierarchy can be divided into: component assembly; segment / part assembly; and overall product assembly. Correspondingly, assembly scenarios can be divided into: component assembly scenario; segment / part assembly scenario; and overall product assembly scenario. The component assembly scenario completes the assembly simulation from part to component; the segment / part assembly scenario completes the assembly simulation from assembly assembly of assemblies and parts to segment components; and the overall product assembly scenario completes the assembly simulation from segment components, assemblies, and parts to the overall product.

[0109] b) Decompose assembly by product assembly station. Based on the layout of the manufacturing unit, develop assembly process plans. Complex assembly scenarios are broken down into different assembly scenarios according to the assembly process plan and assembly stations, and then assembly simulation is performed. Because the generated assembly simulation results are closely integrated with actual production, they can be embedded into the 3D virtual scene with minimal editing, guiding on-site production and improving on-site assembly efficiency.

[0110] 3) Maintenance process model Maintenance process model simulation realizes the movement and operation of virtual humans in a virtual maintenance scenario, as well as the interaction between virtual humans and virtual maintenance prototypes. It provides necessary interactive control methods to enable trainees to participate in virtual maintenance training in real time and interactively. Therefore, virtual maintenance process simulation should include virtual human maintenance action simulation, human-computer interaction control, and virtual human traversal control. The entire maintenance process is completed through a series of maintenance actions controlled by human-computer interaction. Traversal control ensures the realism of the virtual environment and the user's immersion. The basic elements included in the diesel engine maintenance process are as follows: a) Maintenance Event: A maintenance event refers to one or more maintenance operations performed based on a fault, false alarm, or a pre-planned maintenance schedule. A maintenance event is the sum of all operations performed for a specific maintenance task. It generally includes processes such as fault detection, fault isolation, disassembly, replacement, assembly, calibration, and inspection. Each maintenance process can be further broken down to the lowest level.

[0111] b) Repair Object: The repair object refers to the product or component awaiting repair. It is the main object in the repair process, possessing a certain size and structure and complete component constraints, and must be repaired according to a specific disassembly and assembly sequence.

[0112] c) Maintenance Personnel: Maintenance personnel are a type of maintenance resource, but as the main implementers of the maintenance process, they are listed separately. Based on the required maintenance tasks, maintenance personnel follow a prescribed work sequence, using maintenance tools and other necessary resources to repair products or components. The maintenance process involves human operating methods and actions, all of which will affect the maintenance process.

[0113] d) Maintenance Resources: Maintenance resources mainly include maintenance tools, equipment, spare parts, and related maintenance documentation. Tools and equipment are divided into general-purpose and special-purpose; they are reused by operators during maintenance and generally do not involve tool and equipment consumption. Spare parts, on the other hand, are consumables and are continuously depleted during use. Maintenance documentation mainly refers to maintenance knowledge manuals, such as product maintenance outlines and maintenance process checklists.

[0114] e) Maintenance Status: This describes the status of the maintenance object, resources, and personnel during the maintenance process. Examples include the assembly status of the maintenance object; the number of maintenance personnel, the current maintenance operation, and whether maintenance tools are needed; the types and quantities of maintenance tools and equipment; and the usage status of various spare parts. The maintenance status comprehensively describes the current attribute information of every object in the system.

[0115] f) Maintenance Time: Maintenance time is the total time spent on all maintenance activities involved in the maintenance process. It accurately reflects the time consumed by each maintenance operation. Expressing maintenance time during the maintenance process facilitates the calculation of maintainability time parameters later.

[0116] g) Maintenance Constraints: Maintenance constraints refer to the interactions between maintenance objects, personnel, tools, equipment, and spare parts during the maintenance process. A maintenance event is a series of operational activities performed by people, which must be carried out under certain constraints; otherwise, system chaos will occur. For example, maintenance personnel need to replace parts according to the product's disassembly and assembly rules, where the tools used are specific, and the disassembly and assembly sequence between parts is also fixed. In addition, there are also sequential constraints between various maintenance activities within a maintenance event.

[0117] Based on the information and logical relationships between various maintenance tasks during the maintenance process, a hierarchical Petri net is used to establish a maintenance process network model. The maintenance process is defined as follows:

[0118] in: For any element, the finite set of all subnets It is a non-hierarchical Petri net.

[0119] Let be a finite set of all storage locations, representing various types of maintenance resources. A collection of repair tools. For the collection of maintenance equipment, For the collection of spare parts, It is a collection of conflict libraries.

[0120] For a finite set of transitions, This represents maintenance actions, where DR represents the actions of the maintenance personnel and DG represents the actions of the maintenance tools. Since maintenance tools are used by maintenance personnel, theoretically DR = DG. However, in some cases, maintenance personnel may not need tools for their operations. .

[0121] Let be a set of directed arcs, representing the state transition process of maintenance operations.

[0122] The time T for the change in stress is derived from the time of the virtual maintenance.

[0123] Let be the state function of the depot, representing the state of each depot during the maintenance process.

[0124] 4) Material rendering and lighting processing Material rendering and lighting processing are mainly used to build a "real installation", "field", and "real-time" virtual environment for maintainability verification, effectively providing an advanced experimental environment and simulation means for equipment maintenance operation training, fault detection training, technical support training, etc.

[0125] For material rendering and lighting processing, essentially, it is to adjust the color, shadow, lighting brightness, etc. of the 3D scene according to the changes of factors such as surface normal, viewing direction, and lighting. This solution adopts physically based rendering (PBR) and Phong lighting model, and can create various light sources such as directional light, point light source, and cone light source according to needs, and uses deferred shading rendering method to generate a realistic rendering scene.

[0126] Step 4 Virtual Verification Execution and Analysis 4.1 Virtual Maintenance Digital Human Technology The main requirements are the efficiency, realism, and smoothness of maintenance action simulation, and it can simulate maintenance operations in a conventional environment. The rationality of the structure, posture, and actions of the virtual digital human will directly affect the results of maintainability analysis and evaluation.

[0127] 4.2 Virtual Maintenance Digital Prototype Technology The virtual maintenance prototype combines two professional fields of virtual prototype and maintenance design (including maintainability and maintenance process design). In the platform design, the main content of virtual maintenance is limited to the simulation of disassembly, part replacement, and installation activities in the maintenance process of mechanical products.

[0128] Step 5 Maintainability Comprehensive Evaluation Technology Maintainability analysis runs through the entire process of maintainability design and mainly has an impact at the beginning of the design. Maintainability analysis reasonably analyzes the possible maintenance processes and maintainability indicators, combines the key points affecting the realization of the maintenance process, determines the weak points in the design scheme, and provides guidance for the improvement of maintainability design work.

[0129] Compared with the current existing technologies, this invention realizes reachability and visibility verification in the virtual verification of diesel engine maintainability. Maintenance reachability refers to the degree of easy access when repairing, replacing, or maintaining components. Reachability and visibility are the most basic requirements that diesel engine maintainability must meet, and their design must meet the following basic criteria. The maintenance operation space should be designed according to human body dimensions, and the operation space should be larger than the minimum operation space of the human body. Maintenance personnel should be able to see their own operation actions during the maintenance process. The research work on diesel engine maintainability verification has great military significance and economic significance.

[0130] This invention replaces physical prototypes with virtual simulation technology, supporting maintainability verification in the early stages of design, enabling parallel development of maintainability design and product design, and shortening the development cycle; it reduces verification costs dependent on physical prototypes and minimizes the financial and time investment required for later design modifications; it adopts a full-process verification scheme covering requirements analysis, scheme formulation, and prototype modeling, improving the systematic nature and accuracy of verification; and it introduces technologies such as layered disassembly and assembly, ant colony algorithm optimization, and hybrid collision detection, improving the efficiency and accuracy of maintainability verification in complex scenarios and providing reliable guidance for diesel engine maintainability design.

[0131] This invention enables virtual verification of diesel engine maintainability in the early design phase, overcoming reliance on physical prototypes, significantly shortening the design cycle, and reducing development costs. A systematic process and standardized procedures ensure the comprehensiveness and reliability of the virtual verification. Several advanced technologies are employed, including hybrid collision detection algorithms, multi-granularity lightweight models, layered disassembly and assembly planning, and Petri net-based maintenance process modeling, effectively improving the accuracy and efficiency of the verification process. This invention comprehensively considers factors such as spacing, collision, ergonomics, and dynamic processes, making the maintainability assessment results more scientific and accurate. It provides a referable technical approach and methodological reference for the virtual verification of maintainability and even general quality characteristics of other complex equipment.

[0132] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A virtual verification method for diesel engine maintainability based on a complex model, characterized in that, Includes the following steps: S1. Maintainability Verification Requirements Analysis: Perform subsystem hierarchical division, structural disassembly and assembly maintainability analysis, and disassembly and assembly sequence maintainability analysis for the diesel engine, and clarify maintainability indicators and verification tasks; S2. Maintainability Verification Plan Development: Based on the analysis results of S1, develop specifications for diesel engine model construction, maintenance environment construction, and virtual disassembly and assembly sequence development, and construct a virtual verification environment; S3. Maintenance Virtual Prototype Modeling: Based on the specifications established in S2, a maintenance virtual prototype is constructed, which includes virtual maintenance behavior simulation and virtual maintenance disassembly and assembly sequence simulation. S4. Virtual Verification Execution and Analysis: In the constructed virtual environment, drive the maintenance virtual prototype to execute the verification tasks determined in S1, and perform parallel spacing analysis, motion collision analysis, human-machine ergonomics analysis and maintenance process dynamic analysis to obtain maintainability assessment data. S5. Comprehensive Maintainability Evaluation: Based on the evaluation data obtained in S4, a comprehensive evaluation of the maintainability of the diesel engine is conducted to identify design weaknesses and propose improvement suggestions.

2. The method for virtual verification of diesel engine maintainability based on a complex model according to claim 1, characterized in that, In step S1, the subsystem hierarchical division includes the division of functions, structures, working principles, performance requirements, and inter-interface relationships of the engine, fuel system, cooling system, lubrication system, intake system, and exhaust system; the disassembly and assembly sequence maintainability analysis includes the steps of disassembly and assembly information extraction, disassembly and assembly information model establishment, disassembly and assembly sequence generation, disassembly and assembly sequence optimization, and optimal sequence output.

3. The method for virtual verification of diesel engine maintainability based on a complex model according to claim 1, characterized in that, In step S2, the virtual disassembly and assembly sequence development adopts the ant colony algorithm and uses the ant cycle model for global optimization; the virtual maintenance environment construction includes the construction of virtual maintenance scene, virtual maintenance personnel model, maintenance personnel posture model and maintenance tool model, and uses physically based rendering and Phong lighting model for material rendering and lighting processing.

4. The method for virtual verification of diesel engine maintainability based on a complex model according to claim 1, characterized in that, In step S3, the virtual prototype modeling for maintenance adopts the same source multi-granularity lightweight model technology, which divides the model into four orders of magnitude: original model, high-level lightweight model, medium-level lightweight model and low-level lightweight model. The model simplification adopts the triangular edge collapse algorithm based on the quadratic error metric. The virtual maintenance disassembly and assembly sequence simulation adopts the hierarchical disassembly and assembly sequence planning method based on the unordered tree structure.

5. The method for virtual verification of diesel engine maintainability based on a complex model according to claim 1, characterized in that, In step S3, the maintenance process model is constructed using hierarchical Petri nets, formally defined as U = {SP, P, T, F, H, M}, where SP is a finite set of all subnets, P is a finite set of all locations, T is a finite set of transitions, F is a set of directed arcs, H is the time corresponding to transition T, and M is the state function of the location.

6. The method for virtual verification of diesel engine maintainability based on a complex model according to claim 1, characterized in that, In step S4, the motion collision analysis adopts a hybrid collision detection algorithm that combines the spatial decomposition method with the OBB hierarchical bounding box method.

7. The method for virtual verification of diesel engine maintainability based on a complex model according to claim 1, characterized in that, In step S4, the ergonomics analysis constructs an evaluation index system based on the analytic hierarchy process. The evaluation indexes include joint motion factors and body balance of each kinetic chain.

8. The method for virtual verification of diesel engine maintainability based on a complex model according to claim 1, characterized in that, In step S4, the spacing analysis includes calculating the minimum static spacing between the repair object, tools, and surrounding environmental components, and introducing a virtual human model to analyze operational accessibility; the dynamic analysis of the repair process includes driving the virtual human to execute a repair operation sequence, simulating and verifying the rationality of the disassembly and assembly process, the applicability of the tools, the sufficiency of the operating space, and the comfort of the virtual human's movement.

9. The method for virtual verification of diesel engine maintainability based on a complex model according to claim 1, characterized in that, In step S5, the maintainability comprehensive evaluation comprehensively considers the spacing analysis results, collision detection results, human-machine ergonomics evaluation results, maintenance process time data, and logical correctness.

10. A virtual verification system for diesel engine maintainability based on a complex model, characterized in that, include: The requirements analysis module is used to perform subsystem hierarchical division, structural disassembly and assembly maintainability analysis, and disassembly and assembly sequence maintainability analysis of the diesel engine, and to clarify maintainability indicators and verification tasks. The solution formulation module is used to formulate diesel engine model construction specifications, maintenance environment construction specifications, and virtual disassembly and assembly sequence development specifications based on the analysis results of the requirements analysis module, and to build a virtual verification environment; The prototype modeling module is used to construct a virtual maintenance prototype based on the specifications defined in the scheme development module, which includes virtual maintenance behavior simulation and virtual maintenance disassembly and assembly sequence simulation. The verification execution module is used to drive the maintenance virtual prototype to perform the verification tasks determined by the requirements analysis module in the constructed virtual environment, and to perform spacing analysis, motion collision analysis, human-machine ergonomics analysis and maintenance process dynamic analysis in parallel to obtain maintainability assessment data. The comprehensive evaluation module is used to comprehensively evaluate the maintainability of the diesel engine based on the evaluation data obtained from the verification execution module, identify design weaknesses, and propose improvement suggestions.

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