Layered modeling and drill bit optimization design method based on lunar soil structure characteristics

Abstract

The invention discloses a layered modeling and drill bit optimization design method based on lunar soil structure characteristics, and belongs to the field of lunar soil structure model and drill bit structure optimization design. The method comprises the following steps: establishing a lunar soil-lunar rock-lunar soil layered composite model based on a Mohr-Coulomb model; the characteristics of low cohesion and high friction angle of a lunar soil layer and high density and high elastic modulus of a lunar rock layer are given, a drill bit three-dimensional model is constructed through Siemens NX and assembled with the lunar soil-lunar rock-lunar soil layered composite model to form a drill bit-composite lunar soil model, and finite element analysis is adopted to determine the optimization range of drill bit structure parameters; and further taking the lowest cutting power consumption and the highest efficiency as double targets, carrying out coding and collaborative optimization on drill bit structure parameters by utilizing a genetic algorithm, calculating a superposition value of the cutting power consumption of lunar soil and lunar rock through step-by-step iteration, and carrying out decoding in combination with constraint conditions to obtain an optimal parameter combination. The drill bit structure optimized by the method can improve the lunar soil drilling efficiency and reliability, and is suitable for the design of a drilling mechanism for a lunar sampling task.

Description

Technical Field

[0001] The present invention relates to the field of lunar soil structure models and drill bit structure optimization design, and more specifically, to a hierarchical modeling and drill bit optimization design method based on lunar soil structure characteristics. Background Art

[0002] With the in-depth development of lunar exploration missions, drilling in lunar soil and lunar rock composite strata has become a key technical challenge for obtaining lunar surface samples. Traditional drill bit design methods are mostly based on homogeneous geological models, and do not fully consider the mechanical property differences between the layered structures of lunar soil and lunar rock: the lunar soil layer is loose and has low cohesion, while the lunar rock layer has high density and high strength. In the prior art, single material models and parameter optimization strategies are difficult to simulate the dynamic cutting behavior of drill bits in composite strata, resulting in low drilling efficiency, high power consumption, and easy wear or jamming of drill bits. In addition, existing optimization methods mostly focus on single objectives and lack effective support for multi-objective collaborative optimization, making it difficult to meet the drilling requirements in complex lunar surface environments.

[0003] Therefore, a drill bit design method that can accurately characterize the layered characteristics of lunar soil and integrate multi-objective optimization algorithms is needed to solve the problems of model distortion and single optimization objective in the prior art, thereby improving the adaptability and operation efficiency of lunar drilling equipment in complex lunar soil environments. Summary of the Invention

[0004] To solve the above problems, the purpose of the present invention is to provide a hierarchical modeling and drill bit optimization design method based on lunar soil structure characteristics.

[0005] In order to overcome the deficiencies of the prior art, the present invention adopts the following technical solutions:

[0006] A hierarchical modeling and drill bit optimization design method based on lunar soil structure characteristics, characterized by comprising:

[0007] Step S1: Obtain data on the actual on-site working conditions of the drill bit, establish a finite element analysis model of the drill bit - composite lunar soil, and perform finite element analysis calculations to obtain the optimization range of the drill bit structure parameters, including the following steps:

[0008] Step S11: Perform hierarchical modeling of lunar soil based on the Mohr-Coulomb model, superimpose lunar soil and lunar rock to form a lunar soil - lunar rock - lunar soil combined model, and assign characteristic parameters of different layers of lunar soil to obtain a composite lunar soil model; the characteristic parameters of lunar soil in step S11 include density, elastic parameters, and plastic parameters of the Mohr-Coulomb model;

[0009] Step S12: Establish a three-dimensional geometric model of the drill bit through Siemens NX. The model includes key design parameters such as cutting edges, spiral grooves, and rake angles. Import the three-dimensional geometric model of the drill bit and the lunar soil model into the CAE software and perform assembly to complete the construction of the three-dimensional model of the drill bit-lunar soil composite;

[0010] Step S13: Mesh the drilling and sampling mechanism model using a block processing strategy;

[0011] Step S14: Define the material properties, contact constraint conditions of the drill bit and the lunar soil composite, set the friction coefficient, and set the load and boundary conditions; The set load and boundary conditions in Step S14 include setting the fixed support boundary conditions around and at the bottom of the lunar soil model, as well as the linear feed speed of the drill bit and the rotational speed of the cutting edge;

[0012] Step S15: Set the analysis steps according to the structural parameters of the drill bit; The structural parameters of the drill bit in Step S15 include the widths b1 and b2 of the main and secondary cutting edges, the rake angles θ1 and θ2 of the main and secondary cutting edges, the cutting angle α of the cutting edge, the rake angle φ of the cutting edge, and the cutting depth h0;

[0013] Step S16: Perform finite element analysis and calculation on the finite element analysis model of the drill bit-lunar soil composite to obtain the optimization range of the structural parameters of the drill bit;

[0014] Step S2: Optimize the design of each structural parameter of the drill bit based on the genetic algorithm to obtain the optimal structural parameters that meet the lowest cutting power consumption and the highest cutting efficiency, including the following steps:

[0015] Step S21: Take the lowest cutting power consumption and the highest cutting efficiency as the optimization design objectives, keep the rotational speed and linear feed speed of the drill bit constant, and construct an objective function for multi-objective optimization;

[0016] Step S22: Select the main cutting edge b1, secondary cutting edge b2, cutting angle α of the cutting edge, rake angle θ1 of the main cutting edge, rake angle θ2 of the secondary cutting edge, cutting depth h0, and rake angle φ of the cutting edge in the structural parameters of the drill bit as the optimization design variables, that is Set the upper and lower limit ranges of the design variables;

[0017] Step S23: Write the optimization program for the structural parameters of the drill bit as follows: (1) Determine the population size, iteration upper limit, and ParetoFraction of the genetic algorithm; (2) Define the corresponding variable parameters; (3) Set the constraint conditions for the optimization design variables; (4) Calculate the objective function value;

[0018] Step S24: Convert the drill bit structure parameters into a coding form that can be processed by the genetic algorithm to obtain "population t", i.e., the initial population. Through double-objective collaborative optimization, calculate two different fitness values F1 and F2 for "population t", corresponding to the lunar soil cutting mechanics model and the drill bit cutting lunar rock profile mechanics model respectively. For each fitness value, perform arithmetic operations of "maximum number of iterations, crossover, and mutation" to obtain "population t+1". Then, determine whether "population t+1" meets the requirements. If it does not meet the requirements, assign "population t+1" to "population t" and continue the next round of fitness value calculation and iterative operation. If it meets the requirements, proceed to the next step and perform a "decoding" operation on the population that meets the requirements to finally obtain the "optimal structure parameters", i.e., the optimized result.

[0019] The upper and lower limit ranges of the design variables described in step S22 and the optimized range values of the drill bit structure parameters described in step S16 are both:

[0020] The value ranges of the widths b1 and b2 of the main and secondary cutting edges are both 0 - 4 mm.

[0021] The value ranges of the rake angles θ1 and θ2 of the main and secondary cutting edges are both 0 - 40°.

[0022] The value range of the cutting angle α of the cutting edge is 30° - 60°.

[0023] The sum of the cutting angle α of the cutting edge and the rake angle φ of the cutting edge should be less than or equal to 90°.

[0024] The value range of the cutting depth h0 is 0 - 3 mm.

[0025] Step S11 further includes: a lunar soil - lunar rock - lunar soil composite model based on hierarchical structure division. Among them, the lunar soil layer is set with a larger friction angle and low cohesion to simulate the characteristics of loose particles, and the lunar rock layer is given a higher density and elastic modulus to simulate the characteristics of high-strength hard rock.

[0026] In step S15, the analysis step is set as: only change one of the structure parameters each time, and keep the other parameter values unchanged, and separately investigate the influence of each drill bit structure parameter on the cutting efficiency and power consumption.

[0027] The objective function in step S21 needs to be calculated separately according to the soil types passed through by the drill bit during drilling and finally summed up. The soil is a composite lunar soil model with layers of two property materials, lunar soil and lunar rock stacked. That is, when calculating the power consumption and efficiency during the drill bit cutting of the composite lunar soil, first calculate the power consumption generated by the drill bit when drilling the lunar soil and lunar rock respectively, then sum up the power consumption generated by the lunar soil and lunar rock respectively to obtain the power consumption generated during the drill bit cutting of the composite lunar soil, and then calculate the mechanical efficiency during the drill bit drilling of the composite lunar soil according to the efficiency calculation formula.

[0028] Advantages of the present invention: By using the hierarchical modeling technology to construct a lunar soil-lunar rock-lunar soil composite model and assigning different mechanical parameters to each layer based on the Mohr-Coulomb model, the present invention improves the characterization ability of the drilling mechanical model for the dynamic mechanical behavior of the composite formation, and solves the problem of simulation distortion caused by the traditional homogeneous model ignoring the layered characteristics; through the collaborative design of dynamic finite element simulation and genetic algorithm multi-objective optimization, when optimizing the drill bit structure parameters, the balance between cutting power consumption and efficiency is taken into account, effectively reducing the cutting resistance and energy loss of the drill bit in the alternating layer of lunar soil and lunar rock, and enhancing the adaptability and long-term operation reliability of the drilling equipment in the complex lunar soil environment. Description of the Drawings

[0029] Figure 1 is the lunar soil-lunar rock-lunar soil composite model;

[0030] Figure 2 is the flowchart of the genetic algorithm. Detailed Embodiments

[0031] The technical solution of the present invention will be further described below with reference to the drawings and through specific embodiments.

[0032] A method for hierarchical modeling and drill bit optimization design based on the structural characteristics of lunar soil, characterized by comprising:

[0033] Step S1: Obtain the data of the actual on-site working conditions of the drill bit, establish a finite element analysis model of the drill bit-composite lunar soil, perform finite element analysis calculations, and obtain the optimization range of the drill bit structure parameters, including the following steps:

[0034] Step S11: Based on the Mohr-Coulomb model, perform hierarchical modeling on lunar soil, stack lunar soil and lunar rock into a lunar soil-lunar rock-lunar soil composite model as Figure 1 shown, and assign lunar soil characteristic parameters to different layers to obtain a composite lunar soil model; the lunar soil characteristic parameters in step S11 include density, elastic parameters, and plastic parameters of the Mohr-Coulomb model;

[0035] Step S12: Establish a three-dimensional geometric model of the drill bit through Siemens NX. The model includes key design parameters such as cutting edges, spiral grooves, and edge inclination angles. Import the three-dimensional geometric model of the drill bit and the lunar soil model into the CAE software and perform assembly to complete the construction of the three-dimensional model of the drill bit-composite lunar soil;

[0036] Step S13: Adopt a block processing strategy to mesh the drilling and sampling mechanism model;

[0037] Step S14: Define the material properties, contact constraint conditions, set the friction coefficient, and set the load and boundary conditions of the drill bit and the composite lunar soil; the set load and boundary conditions in Step S14 include setting the fixed support boundary conditions around and at the bottom of the lunar soil model, as well as the linear feed speed of the drill bit and the rotational speed of the cutting edge;

[0038] Step S15: Set the analysis step according to the structural parameters of the drill bit; the structural parameters of the drill bit in Step S15 include the widths b1, b2 of the main and secondary cutting edges, the rake angles θ1, θ2 of the main and secondary cutting edges, the cutting angle α of the cutting edge, the rake angle φ of the cutting edge, and the cutting depth h0;

[0039] Step S16: Perform finite element analysis and calculation on the finite element analysis model of the drill bit - composite lunar soil to obtain the optimization range of the structural parameters of the drill bit;

[0040] Step S2: Optimize the design of each structural parameter of the drill bit based on the genetic algorithm to obtain the optimal structural parameters that meet the lowest cutting power consumption and the highest cutting efficiency, including the following steps:

[0041] Step S21: Take the lowest cutting power consumption and the highest cutting efficiency as the optimization design objectives, keep the rotational speed and linear feed speed of the drill bit constant, and construct the objective function of multi-objective optimization;

[0042] Step S22: Select the main cutting edge b1, secondary cutting edge b2, cutting angle α of the cutting edge, rake angle θ1 of the main cutting edge, rake angle θ2 of the secondary cutting edge, cutting depth h0, and rake angle φ of the cutting edge in the structural parameters of the drill bit as the optimization design variables, that is Set the upper and lower limit ranges of the design variables;

[0043] Step S23: Write the optimization program for the structural parameters of the drill bit, and the method is as follows: (1) Determine the population size, iteration upper limit, and ParetoFraction of the genetic algorithm; (2) Define the corresponding variable parameters; (3) Set the constraint conditions of the optimization design variables; (4) Calculate the objective function value;

[0044] Step S24: Convert the drill bit structure parameters into a coding form that can be processed by the genetic algorithm to obtain "population t", i.e., the initial population. Through dual-objective collaborative optimization, calculate two different fitness values F1 and F2 for "population t", corresponding to the lunar soil cutting mechanics model and the drill bit cutting lunar rock profile mechanics model respectively. For each fitness value, perform arithmetic operations of "maximum number of iterations, crossover, and mutation" to obtain "population t + 1". Then, determine whether "population t + 1" meets the requirements. If it does not meet the requirements, assign "population t + 1" to "population t" and continue with the next round of fitness value calculation and iterative operation. If it meets the requirements, proceed to the next step and perform a "decoding" operation on the population that meets the requirements to finally obtain the "optimal structure parameters", i.e., the optimized result. The genetic algorithm flowchart is as Figure 2 shown;

[0045] The upper and lower limit ranges of the design variables described in step S22 and the optimized range values of the drill bit structure parameters described in step S16 are both:

[0046] The value ranges of the widths b1 and b2 of the main and secondary cutting edges are both 0 - 4 mm;

[0047] The value ranges of the rake angles θ1 and θ2 of the main and secondary cutting edges are both 0 - 40°;

[0048] The value range of the cutting angle α of the cutting edge is 30° - 60°;

[0049] The sum of the cutting angle α of the cutting edge and the rake angle φ of the cutting edge should be less than or equal to 90°;

[0050] The value range of the cutting depth h0 is 0 - 3 mm.

[0051] Step S11 further includes: a lunar soil - lunar rock - lunar soil composite model based on hierarchical structure division. Among them, a larger friction angle and low cohesion are set for the lunar soil layer to simulate the characteristics of loose particles, and a higher density and elastic modulus are given to the lunar rock layer to simulate the characteristics of high-strength hard rock.

[0052] In step S15, the analysis step is set as: each time, only change one of the structure parameters, and keep the other parameter values unchanged, and investigate the influence of each drill bit structure parameter on the cutting efficiency and power consumption respectively.

[0053] The objective function in the step S21 needs to be calculated separately according to the soil types passed through by the drill bit during drilling and finally summed up. The soil is a composite lunar soil model with layers of two material properties of lunar soil and lunar rock stacked. That is, when calculating the power consumption and efficiency during the process of the drill bit drilling the composite lunar soil, first calculate the power consumption generated by the drill bit drilling the lunar soil and lunar rock respectively, then sum up the power consumption generated by the lunar soil and lunar rock respectively to obtain the power consumption generated during the process of the drill bit drilling the composite lunar soil, and then calculate the mechanical efficiency of the drill bit drilling the composite lunar soil according to the efficiency calculation formula.

Claims

1. A layered modeling and drill bit optimization design method based on lunar soil structural characteristics, characterized in that: Including: Step S1: Obtain the data of the actual on-site working conditions of the drill bit, establish a finite element analysis model of the drill bit - composite lunar soil, conduct finite element analysis calculations, and obtain the optimization range of the drill bit structure parameters, including the following steps: Step S11: Based on the Mohr-Coulomb model, model the lunar soil in layers, superimpose the lunar soil and lunar rock to form a lunar soil - lunar rock - lunar soil composite model, and assign characteristic parameters to different layers of lunar soil to obtain a composite lunar soil model; the lunar soil characteristic parameters in Step S11 include density, elastic parameters, and plastic parameters of the Mohr-Coulomb model; Step S12: Establish a three-dimensional geometric model of the drill bit through Siemens NX. The model includes key design parameters such as cutting edges, spiral grooves, and edge inclination angles. Import the three-dimensional geometric model of the drill bit and the lunar soil model into CAE software and perform assembly to complete the construction of the three-dimensional model of the drill bit - composite lunar soil; Step S13: Use a block processing strategy to mesh the drilling and sampling mechanism model; Step S14: Define the material properties, contact constraint conditions of the drill bit and composite lunar soil, set the friction coefficient, and set the load and boundary conditions; the set load and boundary conditions in Step S14 include setting fixed support boundary conditions around and at the bottom of the lunar soil model, as well as the linear feed speed of the drill bit and the rotational speed of the cutting edge; Step S15: Set the analysis steps according to the structural parameters of the drill bit; the structural parameters of the drill bit in Step S15 include the widths b1, b2 of the main and secondary cutting edges, the edge inclination angles θ1, θ2 of the main and secondary cutting edges, the cutting angle α of the cutting edge, the rake angle φ of the cutting edge, and the cutting depth h0; Step S16: Conduct finite element analysis calculations on the finite element analysis model of the drill bit - composite lunar soil to obtain the optimization range of the drill bit structure parameters; Step S2: Based on the genetic algorithm, optimize the design of each structural parameter of the drill bit to obtain the optimal structural parameters that meet the lowest cutting power consumption and the highest cutting efficiency, including the following steps: Step S21: Take the lowest cutting power consumption and the highest cutting efficiency as the optimization design objectives, keep the drill bit rotation speed and linear feed speed constant, and construct an objective function for multi-objective optimization; Step S22: Select the main cutting edge b1, secondary cutting edge b2, cutting edge cutting angle α, main cutting edge inclination angle θ1, secondary cutting edge inclination angle θ2, cutting depth h0, and cutting edge rake angle φ from the drill bit structural parameters as optimization design variables, that is, Set the upper and lower limits of the design variables; Step S23: Write the optimization program for the drill bit structure parameters as follows: (1) Determine the population size, iteration upper limit, and ParetoFraction of the genetic algorithm; (2) Define the corresponding variable parameters; (3) Set the constraint conditions for the optimization design variables; (4) Calculate the objective function value; Step S24: Convert the drill bit structural parameters into a coding form that can be processed by the genetic algorithm to obtain "population t", that is, the initial population. Through dual-objective collaborative optimization, two different fitness values F1 and F2 are calculated for "population t", corresponding to the lunar soil cutting mechanics model and the drill bit cutting lunar rock profile mechanics model, respectively. For each fitness value, the "maximum number of iterations, crossover, and mutation" operations are performed to obtain "population t+1". Then, it is judged whether "population t+1" meets the requirements. If it does not meet the requirements, "population t+1" is assigned to "population t" and the next round of fitness value calculation and iterative operations are continued. If it meets the requirements, enter the next step and perform a "decoding" operation on the population that meets the requirements to finally obtain the "optimal structural parameters", that is, the optimized result.

2. The hierarchical modeling and drill bit optimization design method based on the lunar soil structure characteristics according to claim 1, wherein, The upper and lower limits of the design variables in step S22 and the optimized range values of the drill bit structural parameters in step S16 are both: The widths b1 and b2 of the primary and secondary cutting edges are both in the range of 0 to 4 mm; The inclination angles θ1 and θ2 of the primary and secondary cutting edges are both in the range of 0 to 40°; The cutting angle α of the cutting edge ranges from 30° to 60°; The sum of the cutting edge cutting angle α and the cutting edge rake angle φ is less than or equal to 90°; The cutting depth h0 ranges from 0 to 3 mm.

3. The method for layered modeling and drill bit optimization design based on lunar soil structural characteristics according to claim 1 is characterized in that: The step S11 further includes: a lunar soil-lunar rock-lunar soil combination model based on layered structure division, wherein the lunar soil layer is set with a larger friction angle and low cohesion to simulate the characteristics of loose particles, and the lunar rock layer is given a higher density and elastic modulus to simulate the characteristics of high-strength hard rock.

4. A hierarchical modeling and drill bit optimization design method based on the structural characteristics of lunar soil according to claim 1, characterized in that The analysis step in step S15 is set as follows: only one of the structural parameters is changed each time, while the other parameters remain unchanged, and the effects of the various structural parameters of the drill bit on the cutting efficiency and power consumption are examined respectively.

5. A hierarchical modeling and drill bit optimization design method based on the structural characteristics of lunar soil according to claim 1, characterized in that The objective function in step S21 needs to be calculated separately according to the soil drilled by the drill bit during the drilling process and finally summed. The soil is a composite lunar soil model in which two materials with lunar properties, lunar soil and lunar rock, are stacked layer by layer. That is, when calculating the power consumption and efficiency generated by the drill bit in the process of drilling the composite lunar soil, the power consumption generated by the drill bit in drilling the lunar soil and lunar rock is first calculated separately, and then the power consumption generated by the lunar soil and lunar rock are summed to obtain the power consumption generated by the drill bit in the process of drilling the composite lunar soil. Finally, the mechanical efficiency of the drill bit in the process of drilling the composite lunar soil is calculated according to the efficiency calculation formula.

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