Automatic polishing process method for helicopter composite material blade

Abstract

The invention belongs to the technical field of automatic polishing of helicopter composite material blades, and relates to an automatic polishing process method of a helicopter composite material blade. According to the technical scheme, the automation control technology, precision mechanical design and advanced computer aided design and manufacturing (CAD / CAM) software are comprehensively applied, and automation and intelligentization of surface treatment of the composite material main blade are achieved; according to the evaluation system for the automatic polishing process method of the helicopter composite material main blade based on the analytic hierarchy process, which polishing method has the best advantage in the aspect of improving the automatic polishing efficiency and quality of the helicopter composite material main blade is determined according to the weight of the polishing scheme, and the polishing precision and efficiency are improved; and meanwhile, the self-adaptability is high, the automation degree is high, and the cost benefit and the safety are high.

Description

Technical Field

[0001] The invention belongs to the technical field of automatic grinding of helicopter composite material blades and relates to an automatic grinding process method for helicopter composite material blades. Background Art

[0002] With the rapid development of the aviation industry, helicopters, as an important means of air transportation, have increasingly higher performance and safety requirements. Composite materials are widely used in the manufacture of helicopter main blades due to their light weight and high strength. Due to their complex curved shapes and high performance requirements, the surface quality of helicopter composite main blades directly affects the aerodynamic performance and structural integrity of the blades. Therefore, the quality requirements for surface treatment are extremely high during the manufacturing process. Traditional manual polishing methods have problems such as low efficiency, unstable quality, and high labor intensity, which can hardly meet the needs of modern aviation manufacturing for high precision and high efficiency.

[0003] A document discloses a composite material component grinding device, including a controller, a mechanical arm, a grinding device and a laser feedback device. The grinding method includes laser scanning the component surface to obtain a data model, importing a target model, establishing a grinding route, grinding according to the route, and providing real-time feedback to compare the polished data model with the target model until the grinding is completed. A document discloses a bad point staggered grinding mechanism for composite blades, which is suitable for the maintenance of wind power blades to improve processing accuracy and blade quality.

[0004] None of the published literature has studied and described the grinding process parameters. This patent proposes an innovative automatic grinding process method and process parameters for automatic grinding of composite blades based on the specific appearance characteristics of helicopter composite main blades, including detailed provisions for the automatic grinding process method and parameters of putty, primer and topcoat on the surface of composite blades. Therefore, the development of an automated, intelligent, standardized and normalized composite main blade grinding process method and process parameters is of great significance for improving the quality of aviation products, reducing costs and improving production efficiency. Summary of the invention

[0005] Purpose of the Invention

[0006] The purpose of the present invention is to provide an automatic grinding process method for a helicopter composite main blade, which realizes precise grinding of the blade surface through automation technology to improve grinding efficiency and quality, and ensure that the blade surface reaches the smoothness and consistency required by the design. In addition, the present invention also aims to reduce manual operations, reduce labor intensity, improve the working environment, and improve the consistency and reliability of the product through automated grinding, so as to meet the manufacturing needs of the aviation industry for high-performance composite blades.

[0007] Technical Solution

[0008] The present invention relates to an automatic grinding process method for helicopter composite material blades. The method realizes precise grinding of the blade surface through automation technology, and adapts to the characteristics of the composite material and the complex curved surface shape of the blade by precisely controlling various parameters in the grinding process, such as contact force, grinding machine speed, sandpaper mesh number, etc., so as to achieve efficient, uniform and stable grinding effect.

[0009] The following steps are involved:

[0010] 1. Data collection: Due to the complex curing reaction during the blade forming process, the shape after forming is different from the theoretical digital model. Grinding, as a contact surface grinding and polishing process, is very important for obtaining the actual shape. Use a 3D laser scanner to perform high-precision scanning on the surface of the helicopter composite main blade to obtain accurate 3D data of the blade surface.

[0011] 2. Digital modeling: Import the collected data into CAD software to build a digital model of the blade.

[0012] 3. First, the blade grinding area is divided into zones, which are divided into D150 and D77 grinding head zones according to the surface curvature radius: the large curvature surface mainly uses the D150 grinding head, which is located in the middle position; the small curvature surface uses the D77 grinding head, which is located on the concave side of the blade and at both ends of the blade, and then the blocks are divided according to a certain length in the length direction.

[0013] 4. Grinding path planning: Use CAM software to automatically plan the grinding path based on the digital model to ensure that the grinding process fully covers the blade surface.

[0014] a) determining the position and posture of each path point of the desired path;

[0015] b) Convert the pose information on the path points into the desired angles of the robot joints through inverse kinematics;

[0016] c) after obtaining the expected joint angles of each path point, interpolating the joint angles;

[0017] d) Add consideration constraints to ensure that the robot does not exceed its physical limits during movement, thereby achieving safe and stable movement:

[0018] e) Solve the function expression of joint angle value and time.

[0019] Use a cubic polynomial to interpolate the initial and final positions of the robot arm, and use the cubic polynomial function θ(t) to represent the joint angle and time. Make the function pass through each path point in turn. The expression is:

[0020] θ(t)=a0+a1t+a2t 2+a3t 3

[0021] In order to make the trajectory curve more continuous, the robot’s initial time t0 and key time t f The speed is 0, and the construction constraints are:

[0022]

[0023] The joint velocity and acceleration on the motion trajectory are:

[0024]

[0025] Combining the above formulas, the cubic polynomial interpolation function is expressed as:

[0026]

[0027] When acceleration constraints are required, cubic polynomial interpolation can no longer meet the requirements, so the quintic polynomial interpolation expression is used as follows:

[0028]

[0029] The constraints are:

[0030]

[0031] 5. Grinding path simulation: Grinding beyond the expected path may damage key parts or components such as blade edges, bushings, wraps, and grounding strips, affecting blade performance, so path verification is required before grinding. The grinding path is simulated by laser projection, and visual identification is performed for situations where the grinding path blocks or covers key areas and parts, and the trajectory is adjusted;

[0032] 6. Polishing parameter model establishment

[0033] According to Preston theory, a material removal rate model of the body structure surface during grinding is established. The material removal rate h(x,y) of the body structure surface is related to the processing parameters during grinding and can be expressed as:

[0034]

[0035] In the formula, h0(x,y) is the material removal rate at a grinding point on the surface of the machine body structure.

[0036] h(x,y)—the amount of workpiece material removed

[0037] k—Preston coefficient

[0038] v(x,y)—Relative speed between the grinding tool and the grinding point on the surface of the machine structure

[0039] P n (x,y)—Contact force between the grinding tool and the surface of the machine structure

[0040] From the above formula, we can see that to ensure uniform removal of material from the surface of the machine body structure, it is not only necessary to maintain the contact force p between the punching tool and the workpiece during the punching process. n (x, y) is a constant force, and its relative velocity v(x, y) must also be controlled.

[0041] Therefore, in the implementation process, according to the characteristics of helicopter coating materials, manual grinding is simulated and compared, and the removal amount is about 3μm. The grinding time is set to t, and the material removal volume Q can be expressed as:

[0042] Q = 3 × 10 -3 ×S

[0043] In the formula, Q is the volume of the material removed.

[0044] S—grinding area

[0045] The material removal rate of the grinding area is expressed as:

[0046]

[0047] Where k is the Preston coefficient

[0048] V—grinding speed

[0049] P—Grinding contact force

[0050] From this, the relationship model between the grinding parameters can be derived to determine the grinding parameter combination that meets the 3 micron removal rate:

[0051] (1) Pressure parameter P:

[0052]

[0053] By predetermining or experimentally measuring the K value (for a specific material and abrasive combination), setting a reasonable grinding time t and grinding speed V, the required pressure P can be calculated.

[0054] (2) Grinding speed V:

[0055]

[0056] Similarly, when K, t, and P are known, the relative speed V between the grinding tool and the workpiece can be determined.

[0057] (3) Grinding time parameter t:

[0058]

[0059] By predetermining or experimentally measuring the K value (for a specific material and abrasive combination), setting a reasonable grinding pressure P and grinding speed V, the required grinding time t can be calculated.

[0060] Furthermore, it also includes 7. automatic grinding execution: through the automatic grinding robot, the grinding operation is performed according to the planned path and preset parameters.

[0061] Furthermore, it also includes automatic grinding method evaluation and optimization:

[0062] A grinding process evaluation system is designed to provide a theoretical model for the optimization of automatic grinding process methods.

[0063] Furthermore, the evaluation system includes a target layer, a criterion layer, a solution layer, steps of the hierarchical analysis method, result analysis, comprehensive weight calculation, and solution ranking.

[0064] Further, 1). Target layer

[0065] The only element processes for the target layer are:

[0066] A1: Improve the efficiency and quality of automatic grinding of helicopter composite main blades

[0067] Further, 2). Criteria layer

[0068] The criteria layer includes the following important factors:

[0069] B1: Grinding accuracy

[0070] B2: Grinding efficiency

[0071] B3: Adaptability

[0072] B4: Degree of Automation

[0073] B5: Cost-effectiveness

[0074] B6: Safety

[0075] Further, 3). Solution layer

[0076] Each solution at the solution level represents a specific polishing method or technology:

[0077] C1: Automatic grinding process method proposed by the present invention

[0078] C2: Traditional manual polishing method

[0079] C3: Semi-automatic grinding method

[0080] Further, 4). The steps of AHP are as follows

[0081] (1) Constructing a judgment matrix

[0082] For each criterion level factor, a judgment matrix is ​​constructed to compare the relative importance of each solution under the criterion.

[0083] (2) Calculate weight

[0084] Perform eigenvalue decomposition on each judgment matrix and calculate the weight of each solution under different criteria.

[0085] (3)Consistency test

[0086] The consistency index and consistency ratio of each judgment matrix are calculated to ensure the consistency of the judgment matrix.

[0087] (4) Comprehensive weight calculation

[0088] The weight of the criterion layer is multiplied by the weight of the scheme,layer under each criterion to obtain the comprehensive weight of each scheme.

[0089] (5) Scheme ranking

[0090] Sort each plan according to the comprehensive weight, and the plan with the largest weight is the optimal polishing method.

[0091] Further, 5. Results Analysis

[0092] Through the above-mentioned analytic hierarchy process, it is possible to determine which grinding method has the greatest advantage in improving the efficiency and quality of automatic grinding of helicopter composite main blades according to the weight of each scheme. Assuming that the final calculation results show that the weight of "the automatic grinding process method proposed by the present invention" is the highest, it can be concluded that this method is the best choice, which can significantly improve the grinding accuracy and efficiency, and at the same time has strong adaptability, high degree of automation, high cost-effectiveness and safety.

[0093] Further, 6. Comprehensive weight calculation

[0094] Multiply the weight of the criterion layer by the weight of the option layer under each criterion to obtain the comprehensive weight of each option.

[0095] Further, 7. Scheme ranking

[0096] Sort each option according to the comprehensive weight, and the option with the largest weight is the best choice. Through the above steps, a judgment matrix can be constructed and AHP can be used for multi-criteria decision analysis. The beneficial effects of this application are:

[0097] 1) Improve efficiency: Automated grinding significantly improves production efficiency and shortens production cycle.

[0098] 2) Quality assurance: Precisely control grinding parameters to ensure the consistency and reliability of grinding quality.

[0099] 3) Reduce costs: reduce labor dependence, reduce labor costs, and improve material utilization.

[0100] 4) Improve the environment: reduce workers’ exposure to harmful dust and noise and improve the working environment.

[0101] 5) Strong adaptability: Quickly adjust parameters. According to the different Pres coefficients when grinding different substrates, the automatic grinding parameters can be quickly adjusted by combining empirical values ​​and standard operating procedures. This solves the problem that fixed parameters are not suitable for the manufacturing characteristics of multiple varieties and small batches in the aviation field, improves the applicability and flexibility of the automatic grinding system, and can be expanded to the design and application of automatic grinding method models for composite parts with complex structures. DETAILED DESCRIPTION

[0102] In order to make the purpose, technical scheme and advantages of the implementation of the present invention clearer, the technical scheme in the embodiment of the present invention will be described in more detail in combination with the embodiment of the present invention. In the example, the same or similar reference numerals throughout represent the same or similar originals or elements with the same or similar functions. The described embodiments are part of the embodiments of the present invention, not all of them. The embodiments described below by reference are exemplary and intended to be used to explain the present invention, and should not be construed as limitations on the present invention. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in the field without creative work are within the scope of protection of the present invention. The following is a detailed description in combination with the embodiments of the present invention.

[0103] The present invention provides a helicopter composite blade automatic polishing method model. Based on the blade shape structure and multiple types of matrix materials, a robot automatic control and sensor feedback system are used to design an automatic fine polishing method model suitable for helicopters and other aircraft, and the model is used to achieve precise polishing of the putty layer, primer layer and topcoat layer on the blade surface. In the putty polishing stage, the automatic polishing robot removes surface unevenness, laying a good foundation for subsequent painting; in the primer polishing stage, the robot adjusts parameters to adapt to the primer characteristics to ensure uniform coating; in the topcoat polishing stage, fine polishing equipment and parameters are used to achieve the final smoothness and glossiness.

[0104] At the same time, the present invention also proposes an innovative automatic grinding process method for helicopter composite main blades, aiming to solve the problems of low efficiency, unstable quality and high labor intensity in traditional manual grinding. The technical solution comprehensively uses automatic control technology, precision mechanical design and advanced computer-aided design and manufacturing (CAD / CAM) software to realize the automation and intelligence of the surface treatment of composite main blades. An evaluation system for automatic grinding process methods for helicopter composite main blades based on hierarchical analysis method is invented and designed. According to the weight of the grinding scheme, it is determined which grinding method has the most advantages in improving the efficiency and quality of automatic grinding of helicopter composite main blades, which improves the grinding accuracy and efficiency, and has strong adaptability, high degree of automation, high cost-effectiveness and safety.

[0105] 1. Automatic grinding process of composite blades

[0106] The present invention relates to an automatic grinding process for composite material blades, comprising the following steps:

[0107] 1. Data collection: Due to the complex curing reaction during the blade forming process, the shape after forming is different from the theoretical digital model. Grinding, as a contact surface grinding and polishing process, is very important for obtaining the actual shape. Use a 3D laser scanner to perform high-precision scanning on the surface of the helicopter composite main blade to obtain accurate 3D data of the blade surface.

[0108] 2. Digital modeling: Import the collected data into CAD software to build a digital model of the blade.

[0109] 3. First, the blade grinding area is divided into zones, which are divided into D150 and D77 grinding head zones according to the surface curvature radius: the large curvature surface mainly uses the D150 grinding head, which is located in the middle position; the small curvature surface uses the D77 grinding head, which is located on the concave side of the blade and at both ends of the blade, and then the blocks are divided according to a certain length in the length direction.

[0110] 4. Grinding path planning: Use CAM software to automatically plan the grinding path based on the digital model to ensure that the grinding process fully covers the blade surface.

[0111] f) determining the position and posture of each path point of the desired path;

[0112] g) Convert the position information on the path points into the desired angles of the robot joints through inverse kinematics;

[0113] h) after obtaining the expected joint angles of each path point, interpolating the joint angles;

[0114] i) Add consideration constraints to ensure that the robot does not exceed its physical limits during movement, thereby achieving safe and stable movement:

[0115] j) Solve the function expression of joint angle value and time.

[0116] Use a cubic polynomial to interpolate the initial and final positions of the robot arm, and use the cubic polynomial function θ(t) to represent the joint angle and time. Make the function pass through each path point in turn. The expression is:

[0117] θ(t)=a0+a1t+a2t 2 +a3t 3

[0118] In order to make the trajectory curve more continuous, the robot’s initial time t0 and key time t f The speed is 0, and the construction constraints are:

[0119]

[0120] The joint velocity and acceleration on the motion trajectory are:

[0121]

[0122] Combining the above formulas, the cubic polynomial interpolation function is expressed as:

[0123]

[0124] When acceleration constraints are required, cubic polynomial interpolation can no longer meet the requirements, so the quintic polynomial interpolation expression is used as follows:

[0125]

[0126] The constraints are:

[0127]

[0128] 5. Grinding path simulation: Grinding beyond the expected path may damage key parts or components such as blade edges, bushings, wraps, and grounding strips, affecting blade performance, so path verification is required before grinding. The grinding path is simulated by laser projection, and visual identification is performed for situations where the grinding path blocks or covers key areas and parts, and the trajectory is adjusted;

[0129] 6. Polishing parameter model establishment

[0130] According to Preston theory, a material removal rate model of the body structure surface during grinding is established. The material removal rate h(x,y) of the body structure surface is related to the processing parameters during grinding and can be expressed as:

[0131]

[0132] In the formula, h0(x,y) is the material removal rate at a grinding point on the surface of the machine body structure.

[0133] h(x,y)—the amount of workpiece material removed

[0134] k—Preston coefficient

[0135] v(x,y)—Relative speed between the grinding tool and the grinding point on the surface of the machine structure

[0136] P n (x,y)—Contact force between the grinding tool and the surface of the machine structure

[0137] From the above formula, we can see that to ensure uniform removal of material from the surface of the machine body structure, it is not only necessary to maintain the contact force p between the punching tool and the workpiece during the punching process. n (x, y) is a constant force, and its relative velocity v(x, y) must also be controlled.

[0138] Therefore, in the implementation process, according to the characteristics of helicopter coating materials, manual grinding is simulated and compared, and the removal amount is about 3μm. The grinding time is set to t, and the material removal volume Q can be expressed as:

[0139] Q = 3 × 10 -3 ×S

[0140] In the formula, Q is the volume of the material removed.

[0141] S—grinding area

[0142] The material removal rate of the grinding area is expressed as:

[0143]

[0144] Where k is the Preston coefficient

[0145] V—grinding speed

[0146] P—Grinding contact force

[0147] From this, the relationship model between the grinding parameters can be derived to determine the grinding parameter combination that meets the 3 micron removal rate:

[0148] (4) Pressure parameter P:

[0149]

[0150] By predetermining or experimentally measuring the K value (for a specific material and abrasive combination), setting a reasonable grinding time t and grinding speed V, the required pressure P can be calculated.

[0151] (5) Grinding speed V:

[0152]

[0153] Similarly, when K, t, and P are known, the relative speed V between the grinding tool and the workpiece can be determined.

[0154] (6) Grinding time parameter t:

[0155]

[0156] By predetermining or experimentally measuring the K value (for a specific material and abrasive combination), setting a reasonable grinding pressure P and grinding speed V, the required grinding time t can be calculated.

[0157] 7. Automatic grinding execution: The automatic grinding robot performs the grinding operation according to the planned path and preset parameters.

[0158] 2. Evaluation and optimization of automatic grinding methods

[0159] An evaluation system for the automatic grinding process of helicopter composite main rotor blades based on the analytic hierarchy process is designed to provide a theoretical model for the optimization of the automatic grinding process.

[0160] 1. Target layer (A)

[0161] The only element processes for the target layer are:

[0162] A1: Improve the efficiency and quality of automatic grinding of helicopter composite main blades

[0163] 2. Standard layer (B)

[0164] The criteria layer includes the following important factors:

[0165] B1: Polishing Precision

[0166] B2: Grinding efficiency

[0167] B3: Adaptability

[0168] B4: Automation Level

[0169] B5: Cost-effectiveness

[0170] B6: Safety

[0171] 3. Solution layer (C)

[0172] Each solution at the solution level represents a specific polishing method or technology:

[0173] C1: Automatic grinding process method proposed by the present invention

[0174] C2: Traditional manual polishing method

[0175] C3: Semi-automatic grinding method (partial use of robots)

[0176] 4. Steps of AHP (1) Constructing Judgment Matrix

[0177] For each criterion level factor (B1, B2, B3, B4, B5, B6), a judgment matrix is ​​constructed to compare the relative importance of each solution (C1, C2, C3) under the criterion.

[0178] B1(grinding accuracy)

[0179] C1C2C3 153

[0181] 1 / 511 / 3

[0182] 1 / 331

[0183] B2(grinding efficiency)

[0184] C1C2C3 174

[0186] 1 / 711 / 2

[0187] 1 / 421

[0188] B3 (Adaptive)

[0189] C1C2C3 185

[0191] 1 / 811 / 3

[0192] 1 / 531

[0193] B4(Automation level)

[0194] C1C2C3 196

[0196] 1 / 911 / 3

[0197] 1 / 631

[0198] B5(Cost-effectiveness)

[0199] C1C2C3 132

[0201] 1 / 311 / 2

[0202] 1 / 221

[0203] B6(Safety)

[0204] C1C2C3 164

[0206] 1 / 611 / 2

[0207] 1 / 421

[0208] (2) Calculate weight

[0209] Perform eigenvalue decomposition on each judgment matrix and calculate the weight of each solution under different criteria.

[0210] (3)Consistency test

[0211] The consistency index (CI) and consistency ratio (CR) of each judgment matrix were calculated to ensure the consistency of the judgment matrix.

[0212] (4) Comprehensive weight calculation

[0213] The weight of the criterion layer is multiplied by the weight of the scheme,layer under each criterion to obtain the comprehensive weight of each scheme.

[0214] (5) Scheme ranking

[0215] Sort each plan according to the comprehensive weight, and the plan with the largest weight is the optimal polishing method.

[0216] 5. Results Analysis

[0217] Through the above-mentioned analytic hierarchy process, it is possible to determine which grinding method has the greatest advantage in improving the efficiency and quality of automatic grinding of helicopter composite main blades according to the weight of each scheme. Assuming that the final calculation results show that the weight of "the automatic grinding process method (C1) proposed by the present invention" is the highest, it can be concluded that this method is the best choice, which can significantly improve the grinding accuracy and efficiency, and at the same time has strong adaptability, high degree of automation, high cost-effectiveness and safety.

[0218] This method can not only quantify the advantages and disadvantages of different polishing methods, but also provide a scientific basis for practical application, ensuring that the manufacturing of helicopter composite main rotor blades achieves the smoothness and consistency required by the design and meets the high performance needs of the aviation industry.

[0219] 6. Comprehensive weight calculation

[0220] Multiply the weight of the criterion layer by the weight of the option layer under each criterion to obtain the comprehensive weight of each option.

[0221] 7. Scheme ranking

[0222] The options are ranked according to the comprehensive weight, and the option with the largest weight is the best choice. Through the above steps, a judgment matrix can be constructed and AHP can be used for multi-criteria decision analysis.

[0223] 3. Implementation Case of Automatic Grinding of Composite Blades

[0224] The automatic grinding process of composite blades. The grinding of helicopter composite blades includes three substrates, namely, the composite surface release agent, putty layer, and coating layer. The coating layer includes a primer layer and a topcoat layer. There is no need to grind the topcoat in the normal operation process. Only when there are defects in the topcoat and rework and repair are required, the topcoat needs to be polished. The Preston coefficients of different substrates are different. It is necessary to select the appropriate Preston coefficient according to the abrasive used and the state of the substrate.

[0225] 1. The automatic polishing process of the release agent on the surface of the composite blade, the specific steps are as follows:

[0226] (1) Cleaning of release agent layer: Use a cleaning agent that will not damage the composite material matrix to clean the putty layer, and then wipe it dry immediately with a clean cloth;

[0227] (2) Data acquisition: Use a 3D laser scanner to perform high-precision scanning on the surface of the helicopter composite main blade to obtain accurate 3D data of the blade surface.

[0228] (3) Digital modeling: The collected data is imported into CAD software to construct a digital model of the blade.

[0229] (4) The blade grinding area is divided into zones and the grinding tools are set.

[0230] (5) Grinding path planning: Use CAM software to automatically plan the grinding path based on the digital model to ensure that the grinding process fully covers the blade surface.

[0231] (6) Grinding path simulation: The grinding path is simulated by laser projection, and visual identification is performed on the situations where the grinding track blocks or covers key areas and parts, and the track is adjusted;

[0232] (7) Establishment of grinding parameter model: The material removal rate model of the surface of the body structure during grinding is established based on Preston theory.

[0233] (8) Automatic grinding execution: The automatic grinding robot performs the grinding operation according to the planned path and preset parameters.

[0234] (9) Blade surface cleaning: Use a cleaning agent that will not damage the composite material matrix to clean the polished surface until the polished dust is cleaned up, and then wipe it dry immediately with a clean cloth.

[0235] 2. Combined with the experience parameters of manual grinding operation, grinding parameter model application case

[0236] The application of the grinding parameter model of the present invention is described below with reference to specific examples:

[0237] According to manual grinding experience, when using abrasives to grind the release agent, the grinding contact force is 5N, the grinding speed is 0.01m / s, the removal thickness is 2 microns, and the grinding is 0.01m 2 The time required for the area is 40s, then:

[0238] a) Calculate the amount of material removed:

[0239] Material removal = area × thickness = 0.01 × 2 × 10 -6 =2×10 -8 m 3 .

[0240] b) Calculate the material removal rate:

[0241] Grinding takes 40 seconds, material removal rate = material removal amount / time = 2 × 10 -8 ÷40=0.5×10 -9 m 3 / s.

[0242] c) Calculate the Preston coefficient according to the Preston equation:

[0243] Material removal rate = Preston coefficient × pressure × speed.

[0244] It can be obtained that: Preston coefficient K = 0.5 × 10 -9 ÷(500×0.01)=1×10 -10 .

[0245] Therefore, under the premise of unchanged abrasive, when automatic grinding is used to simulate manual grinding of the release agent on the surface of composite blades, the Preston coefficient in the grinding parameter model is 1×10 -10 .

[0246] It can be seen from the above specific implementation methods that the grinding parameter model of the present invention can accurately calculate various grinding parameters according to given conditions, thereby achieving effective control of the 2 micron removal amount.

[0247] When using abrasives to polish putty, paint layer, and topcoat layer, it is necessary to accurately measure or reasonably set the Preston coefficient K and other related parameters according to different materials, abrasives, equipment, etc. to ensure the accurate application of the model and the achievement of the polishing effect.

[0248] It is understood by those skilled in the art that, unless otherwise defined, all terms (including technical terms and scientific terms) used herein have the same meaning as the general understanding of ordinary technicians in the field to which the present invention belongs. It should also be understood that terms such as those defined in general dictionaries should be understood to have the same meaning as in the context of the prior art, and unless defined as here, will not be interpreted with idealized or overly formal meanings. The specific implementation methods described above further describe the purpose, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation method of the present invention and is not intended to limit the present invention. Within the spirit and principle of the present invention, any technician familiar with the profession may use the above disclosed technical content to change or modify it into an equivalent embodiment of equivalent changes for application in other fields, but any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present invention without departing from the technical solution content of the present invention, any modification, equivalent replacement, improvement, etc., made according to the technical essence of the present invention, should be included in the protection scope of the present invention.

Claims

1. A method for automatically grinding helicopter composite blades, characterized in that: This method uses automation technology to achieve precise grinding of the blade surface. By precisely controlling various parameters in the grinding process, such as contact force, grinder speed, and sandpaper mesh size, it adapts to the characteristics of composite materials and the complex curved surface shape of the blade, thereby achieving efficient, uniform, and stable grinding effects.

2. The method according to claim 1, characterized in that The following steps are involved: 1) Data collection: Due to the complex curing reaction during the blade forming process, the shape after forming is different from the theoretical digital model. Grinding, as a contact surface grinding and polishing process, is very important for obtaining the actual shape. Use a 3D laser scanner to scan the surface of the helicopter composite main blade with high precision to obtain accurate 3D data of the blade surface; 2). Digital modeling: Import the collected data into CAD software to build a digital model of the blade; 3) First, the blade grinding area is divided into zones, which are divided into D150 and D77 grinding zones according to the surface curvature radius: the large curvature surface mainly uses the D150 grinding head, which is located in the middle; the small curvature surface uses the D77 grinding head, which is located on the concave side of the blade and at both ends of the blade, and then the blocks are divided according to a certain length in the length direction; 4). Grinding path planning: Use CAM software to automatically plan the grinding path based on the digital model to ensure that the grinding process fully covers the blade surface; a) determining the position and posture of each path point of the desired path; b) Convert the pose information on the path points into the desired angles of the robot joints through inverse kinematics; c) after obtaining the expected joint angles of each path point, interpolating the joint angles; d) Add consideration constraints to ensure that the robot does not exceed its physical limits during movement, thereby achieving safe and stable movement: e) Solve the function expression of joint angle value and time; Use a cubic polynomial to interpolate the initial and final positions of the robot arm, and use the cubic polynomial function θ(t) to represent the joint angle and time. Make the function pass through each path point in turn. The expression is: θ(t)=a0+a1t+a2t 2 +a3t 3 In order to make the trajectory curve more continuous, the robot’s initial time t0 and key time t f The speed is 0, and the construction constraints are: The joint velocity and acceleration on the motion trajectory are: Combining the above formulas, the cubic polynomial interpolation function is expressed as: When acceleration constraints are required, cubic polynomial interpolation can no longer meet the requirements, so the quintic polynomial interpolation expression is used as follows: The constraints are: 5) Grinding path simulation: Grinding beyond the expected path may damage the blade edge, bushing, wrap, and key parts of the grounding belt, affecting the blade performance. Therefore, path verification is required before grinding. The grinding path is simulated by laser projection, and the key areas and parts covered by the grinding path are visually identified, and the trajectory is adjusted. 6). Establishment of polishing parameter model According to Preston's theory, a material removal rate model of the body structure surface during grinding is established; the material removal rate h(x, y) of the body structure surface is related to the processing parameters during grinding and can be expressed as: In the formula, h0(x,y) is the material removal rate at a grinding point on the surface of the machine body structure. h(x,y)—the amount of workpiece material removed k—Preston coefficient v(x,y)—Relative speed between the grinding tool and the grinding point on the surface of the machine structure P n (x,y)—Contact force between the grinding tool and the surface of the machine structure From the above formula, we can see that to ensure uniform removal of material from the surface of the machine body structure, it is not only necessary to maintain the contact force p between the punching tool and the workpiece during the punching process. n (x, y) is a constant force, and its relative velocity v(x, y) needs to be controlled; Therefore, in the implementation process, according to the characteristics of helicopter coating materials, manual grinding is simulated and compared, and the removal amount is about 3μm. The grinding time is set to t, and the material removal volume Q can be expressed as: Q=3×10 -3 ×S In the formula, Q is the volume of the material removed; S—grinding area; The material removal rate of the grinding area is expressed as: Where, k—Preston coefficient; V—grinding speed; P—grinding contact force; From this, the relationship model between the grinding parameters can be derived to determine the grinding parameter combination that meets the 3 micron removal rate: (1) Pressure parameter P: By predetermining or experimentally measuring the K value, setting a reasonable grinding time t and grinding speed V, the required pressure P can be calculated; (2) Grinding speed V: Similarly, when K, t, and P are known, the relative speed V between the abrasive tool and the workpiece can be determined; (3) Grinding time parameter t: By predetermining or experimentally measuring the K value, setting a reasonable grinding pressure P and grinding speed V, the required grinding time t can be calculated.

3. The method according to claim 2, characterized in that Also includes 7). Automatic grinding execution: Through the automatic grinding robot, the grinding operation is performed according to the planned path and preset parameters.

4. The method according to claim 3, characterized in that It also includes the evaluation and optimization of automatic polishing methods: designing a polishing process method evaluation system to provide a theoretical model for the optimization of automatic polishing process methods.

5. The method according to claim 4, characterized in that The evaluation system includes a target layer, a criterion layer, a scheme layer, steps of the hierarchical analysis method, result analysis, comprehensive weight calculation, and scheme ranking.

6. The method according to claim 5, characterized in that 1). Target layer The only element processes for the target layer are: A1: Improve the efficiency and quality of automatic grinding of helicopter composite main blades.

7. The method according to claim 6, characterized in that 2) Standards layer The criteria layer includes the following important factors: B1: Grinding accuracy B2: Grinding efficiency B3: Adaptability B4: Degree of Automation B5: Cost-effectiveness B6: Safety 3) Solution layer Each solution at the solution level represents a specific polishing method or technology: C1: Based on the automatic polishing process proposed by the present invention; C2: Traditional manual polishing method; C3: Semi-automatic grinding method.

8. The method according to claim 7, characterized in that 4). The steps of AHP are as follows: (1) Constructing a judgment matrix For each criterion-level factor, a judgment matrix is ​​constructed to compare the relative importance of each solution under the criterion; (2) Calculate weight Perform eigenvalue decomposition on each judgment matrix and calculate the weight of each solution under different criteria; (3)Consistency test Calculate the consistency index and consistency ratio of each judgment matrix to ensure the consistency of the judgment matrix; (4) Comprehensive weight calculation Multiply the weight of the criterion layer by the weight of the scheme,layer under each criterion to obtain the comprehensive weight of each scheme; (5) Scheme ranking Sort each plan according to the comprehensive weight, and the plan with the largest weight is the optimal polishing method.

9. The method according to claim 8, characterized in that 5. Results Analysis Through the above analytic hierarchy process, it is possible to determine which grinding method has the greatest advantage in improving the efficiency and quality of automatic grinding of helicopter composite main blades according to the weight of each scheme; assuming that the final calculation result shows that the weight of "the automatic grinding process method proposed by the present invention" is the highest, it can be concluded that this method is the best choice, which can significantly improve the grinding accuracy and efficiency, and at the same time has strong adaptability, high degree of automation, high cost-effectiveness and safety; 6. Comprehensive weight calculation Multiply the weight of the criterion layer by the weight of the option layer under each criterion to obtain the comprehensive weight of each option.

10. The method according to claim 9, characterized in that 7. Scheme ranking Sort the options according to the comprehensive weight, and the option with the largest weight is the best choice; through the above steps 1-9, a judgment matrix can be constructed and AHP can be used for multi-criteria decision analysis.

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