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RSS2023 Vol. 42, No. 6
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2023, 42(6): 821-828.
doi: 10.13433/j.cnki.1003-8728.20220001
PDF 1804KB
Abstract:
To solve the problem of tool wear monitoring in metal milling, a tool wear monitoring model is proposed based on recursive feature elimination and extra trees algorithm. Firstly, the time and frequency domain features of force, vibration and acoustic emission signals are extracted. Logistic regression, classification and regression tree, linear regression and linear discriminant analysis are used as base model of recursive feature elimination for feature dimension reduction. Then the processed features are used to train the K nearest neighbor, support vector regression and extra trees models, and a variety of monitoring models are obtained. By comparing the tool wear fitting curve and analyzing the standard deviation of the evaluation results, it can be concluded that the base model is the recursive feature elimination of classification and regression tree. The fitting degree of the model combined with the extreme random tree algorithm reaches 99.74 %, and the standard deviation of the evaluation result is 4.04. The results show that this method can effectively monitor the wear of milling cutter, so as to improve the machining quality of parts.
To solve the problem of tool wear monitoring in metal milling, a tool wear monitoring model is proposed based on recursive feature elimination and extra trees algorithm. Firstly, the time and frequency domain features of force, vibration and acoustic emission signals are extracted. Logistic regression, classification and regression tree, linear regression and linear discriminant analysis are used as base model of recursive feature elimination for feature dimension reduction. Then the processed features are used to train the K nearest neighbor, support vector regression and extra trees models, and a variety of monitoring models are obtained. By comparing the tool wear fitting curve and analyzing the standard deviation of the evaluation results, it can be concluded that the base model is the recursive feature elimination of classification and regression tree. The fitting degree of the model combined with the extreme random tree algorithm reaches 99.74 %, and the standard deviation of the evaluation result is 4.04. The results show that this method can effectively monitor the wear of milling cutter, so as to improve the machining quality of parts.
2023, 42(6): 829-834.
doi: 10.13433/j.cnki.1003-8728.20220017
Abstract:
With the development of rail transit, trains have become an important means of transport for freight transportation, so finding an effective method to evaluate train derailment has become a research focus. We study the phenomenon of sudden state changes in trains on straight roads and apply the catastrophe theory to accident analysis of train derailment. Based on the folding catastrophe in the elementary catastrophe theory, considering the influence of the train's lateral vibration acceleration and the deflection angle of the center of gravity on the train derailment, the folding catastrophe model of the train derailment accident is established. When it is approaching derailment, according to the principle of invariable value of elastic potential energy and Taylor expansion, the folding catastrophe potential function equation of the train derailment accident is deduced. By analyzing the balance curve and bifurcation set of the catastrophe model, give out of the danger zone of derailment during train operation. The Simpack software was used to establish the vehicle track model, and different types of road excitation spectra were applied. The simulation results were analyzed and compared with the balance curve and bifurcation set in the catastrophe model. It was obtained that when the train was running, the lateral vibration acceleration jumped from the lower half of the balance curve. In the upper half of the branch, the derailment coefficient increases and the risk of train derailment increases. Finally, a new train derailment evaluation method based on folding catastrophe theory is obtained.
With the development of rail transit, trains have become an important means of transport for freight transportation, so finding an effective method to evaluate train derailment has become a research focus. We study the phenomenon of sudden state changes in trains on straight roads and apply the catastrophe theory to accident analysis of train derailment. Based on the folding catastrophe in the elementary catastrophe theory, considering the influence of the train's lateral vibration acceleration and the deflection angle of the center of gravity on the train derailment, the folding catastrophe model of the train derailment accident is established. When it is approaching derailment, according to the principle of invariable value of elastic potential energy and Taylor expansion, the folding catastrophe potential function equation of the train derailment accident is deduced. By analyzing the balance curve and bifurcation set of the catastrophe model, give out of the danger zone of derailment during train operation. The Simpack software was used to establish the vehicle track model, and different types of road excitation spectra were applied. The simulation results were analyzed and compared with the balance curve and bifurcation set in the catastrophe model. It was obtained that when the train was running, the lateral vibration acceleration jumped from the lower half of the balance curve. In the upper half of the branch, the derailment coefficient increases and the risk of train derailment increases. Finally, a new train derailment evaluation method based on folding catastrophe theory is obtained.
2023, 42(6): 835-841.
doi: 10.13433/j.cnki.1003-8728.20220025
Abstract:
Design a double-spherical hinged ball-hinged universal connector that can be used for connection and communication among a unit of the robot. In this paper, the innovation and characteristics of the connector are introduced. Adams simulation software was used to analyze the influence of the axial load on the rotational angular velocity. The turning experiments to compare theoretical and actual steering anglesare conducted.The line passing performance test to study the influence of cable diameter and number on cable bendingis carried out. A cable damage test experiment to observe the damage of the internal cable after multiple bendsis conducted. Research indicates that the difference between the theoretical and actual steering angle of the connector is only 5°. In the steering process, ball lever firstly rotates to the limit position and then contacts ball shell, and then the ball lever and ball shell rotate together to reach the limit position; the line passing performance test results meet the requirements of pipeline robot.
Design a double-spherical hinged ball-hinged universal connector that can be used for connection and communication among a unit of the robot. In this paper, the innovation and characteristics of the connector are introduced. Adams simulation software was used to analyze the influence of the axial load on the rotational angular velocity. The turning experiments to compare theoretical and actual steering anglesare conducted.The line passing performance test to study the influence of cable diameter and number on cable bendingis carried out. A cable damage test experiment to observe the damage of the internal cable after multiple bendsis conducted. Research indicates that the difference between the theoretical and actual steering angle of the connector is only 5°. In the steering process, ball lever firstly rotates to the limit position and then contacts ball shell, and then the ball lever and ball shell rotate together to reach the limit position; the line passing performance test results meet the requirements of pipeline robot.
2023, 42(6): 842-849.
doi: 10.13433/j.cnki.1003-8728.20220040
Abstract:
Aiming at the chaos control problem for a single-degree-of-freedom vibro-impact system with clearance, a parameter feedback control method of chaotic motion based on RBFNN (radial basis function neural network) optimized by QPSO (quantum particle swarm optimization) algorithm is proposed in this paper. The correlation relationship and its characteristics between the chaotic motion and specific parameters of the system were analyzed by using bifurcation diagram, Lyapunov exponential spectrum diagram, Poincare cross section diagram and phase diagram. A parameter feedback chaos controller was designed based on RBFNN, and the maximum Lyapunov exponent was used as a weighted term to construct a fitness function, so as to guide the QPSO algorithm to optimize the parameters of the controller and quantitatively evaluate the chaos control effect. In the simulation experiment, the influence of QPSO control parameters (i.e., shrinkage and expansion coefficient) on chaos control effect is further analyzed and studied.
Aiming at the chaos control problem for a single-degree-of-freedom vibro-impact system with clearance, a parameter feedback control method of chaotic motion based on RBFNN (radial basis function neural network) optimized by QPSO (quantum particle swarm optimization) algorithm is proposed in this paper. The correlation relationship and its characteristics between the chaotic motion and specific parameters of the system were analyzed by using bifurcation diagram, Lyapunov exponential spectrum diagram, Poincare cross section diagram and phase diagram. A parameter feedback chaos controller was designed based on RBFNN, and the maximum Lyapunov exponent was used as a weighted term to construct a fitness function, so as to guide the QPSO algorithm to optimize the parameters of the controller and quantitatively evaluate the chaos control effect. In the simulation experiment, the influence of QPSO control parameters (i.e., shrinkage and expansion coefficient) on chaos control effect is further analyzed and studied.
2023, 42(6): 850-856.
doi: 10.13433/j.cnki.1003-8728.20220014
Abstract:
Aiming at the limitations of ground-based mobile robots in unstructured terrain, a design scheme of variable-diameter wheel-legged obstacle-climbing robots based on plane gear connecting rod group is proposed in this paper. Firstly, the transformation principle of the obstacle-climbing robot between wheel mode and wheel-leg mode through variable-diameter mechanism was introduced. When encountering obstacles, the variable-diameter mechanism can change the mode according to the height of the obstacles to perform obstacle crossing movement. On this basis, through deformation ratio calculationand kinematics simulation, the rationality of the design of the variable-diameter mechanism, its strong obstacle-climbing ability, and the reliability and stability of the mode change are verified. Secondly, by constructing a mechanical model to analyze the obstacle-climbing ability of the robot in the two modes, and the maximum obstacle-climbing height in different modes are obtained. Finally, based on ADAMS software, the robot's ability to obstacle-climbing on single steps, continuous steps and complex roads is simulated. The results show that the obstacle-climbing robot has better obstacle-climbing ability when facing different working conditions, which verifies the feasibility of the design scheme.
Aiming at the limitations of ground-based mobile robots in unstructured terrain, a design scheme of variable-diameter wheel-legged obstacle-climbing robots based on plane gear connecting rod group is proposed in this paper. Firstly, the transformation principle of the obstacle-climbing robot between wheel mode and wheel-leg mode through variable-diameter mechanism was introduced. When encountering obstacles, the variable-diameter mechanism can change the mode according to the height of the obstacles to perform obstacle crossing movement. On this basis, through deformation ratio calculationand kinematics simulation, the rationality of the design of the variable-diameter mechanism, its strong obstacle-climbing ability, and the reliability and stability of the mode change are verified. Secondly, by constructing a mechanical model to analyze the obstacle-climbing ability of the robot in the two modes, and the maximum obstacle-climbing height in different modes are obtained. Finally, based on ADAMS software, the robot's ability to obstacle-climbing on single steps, continuous steps and complex roads is simulated. The results show that the obstacle-climbing robot has better obstacle-climbing ability when facing different working conditions, which verifies the feasibility of the design scheme.
2023, 42(6): 857-865.
doi: 10.13433/j.cnki.1003-8728.20230192
Abstract:
In view of the large amount of energy loss caused by fluid high-speed rotation in the overflow pipe during the separation process of hydrocyclone, based on the pressure drop mechanism, the loss of kinetic energy in the hydrocyclone can be reduced by increasing the flow rate of the overflow pipe. The overflow pipe of a hydrocyclone with a diameter of 100mm is designed as a cone shape and the lower part of the overflow pipe is cut into horizontal incision、upward bevel incision、downward bevel incision respectively. The multiphase flow volume of fluid (VOF) model and Reynolds stress model (RSM) were used to calculate the separation performance of different hydrocyclones, the internal velocity field and pressure field of the hydrocyclone were analyzed in detail, and the material separation experiments were carried out on the conventional and improved hydrocyclones under the same experimental conditions, and the energy-saving effect of improved hydrocyclones was studied. The results show that the pressure drop reduction is related to the axial velocity tangential velocity attenuation and pressure reduction gradient, the inlet flow is in the range of 880 -1 000 mL/s, and the separation efficiency of improved hydrocyclones and the conventional hydrocyclone is basically the same, and the separation efficiency of the horizontal slit type, upward bevel incision type and downward bevel incision hydrocyclones reaches the highest when the inlet flow is 980 mL/s, compared with conventional hydrocyclone, the pressure drop rates are 23.79%, 11.65% and 26.46%, respectively, which have significant energy-saving effects.
In view of the large amount of energy loss caused by fluid high-speed rotation in the overflow pipe during the separation process of hydrocyclone, based on the pressure drop mechanism, the loss of kinetic energy in the hydrocyclone can be reduced by increasing the flow rate of the overflow pipe. The overflow pipe of a hydrocyclone with a diameter of 100mm is designed as a cone shape and the lower part of the overflow pipe is cut into horizontal incision、upward bevel incision、downward bevel incision respectively. The multiphase flow volume of fluid (VOF) model and Reynolds stress model (RSM) were used to calculate the separation performance of different hydrocyclones, the internal velocity field and pressure field of the hydrocyclone were analyzed in detail, and the material separation experiments were carried out on the conventional and improved hydrocyclones under the same experimental conditions, and the energy-saving effect of improved hydrocyclones was studied. The results show that the pressure drop reduction is related to the axial velocity tangential velocity attenuation and pressure reduction gradient, the inlet flow is in the range of 880 -1 000 mL/s, and the separation efficiency of improved hydrocyclones and the conventional hydrocyclone is basically the same, and the separation efficiency of the horizontal slit type, upward bevel incision type and downward bevel incision hydrocyclones reaches the highest when the inlet flow is 980 mL/s, compared with conventional hydrocyclone, the pressure drop rates are 23.79%, 11.65% and 26.46%, respectively, which have significant energy-saving effects.
2023, 42(6): 866-869.
doi: 10.13433/j.cnki.1003-8728.20220041
Abstract:
In order to solve the problem of thermally induced preload of spindle bearing of high-speed machine tool under different spindle speeds, cutting loads and initial preloads, a new method of temperature self-compensation with separated spacer was proposed to realize the self-compensation of thermally induced preload of spindle bearing. Firstly, the thermal structure coupling analysis model of the spindle unit was established to analyze the relative axial displacement of the separated spacers under different temperatures and thermally induced preloads. Secondly, the vibration of the main engine and the temperature rise of the bearing before and after compensation were studied with different spindle speeds and the initial preloads with the spindle bearing test platform of high-speed machine tool. The results show that the relative displacement of the spacer varies linearly with temperature, and the initial preload has almost no effect on it. Compared with the traditional integrated spacer, the vibration of the main engine is slightly increased and the temperature rise of the bearing is significantly reduced with the separated spacer, which indicates that the designed separated spacer can effectively reduce the heat-induced preload.
In order to solve the problem of thermally induced preload of spindle bearing of high-speed machine tool under different spindle speeds, cutting loads and initial preloads, a new method of temperature self-compensation with separated spacer was proposed to realize the self-compensation of thermally induced preload of spindle bearing. Firstly, the thermal structure coupling analysis model of the spindle unit was established to analyze the relative axial displacement of the separated spacers under different temperatures and thermally induced preloads. Secondly, the vibration of the main engine and the temperature rise of the bearing before and after compensation were studied with different spindle speeds and the initial preloads with the spindle bearing test platform of high-speed machine tool. The results show that the relative displacement of the spacer varies linearly with temperature, and the initial preload has almost no effect on it. Compared with the traditional integrated spacer, the vibration of the main engine is slightly increased and the temperature rise of the bearing is significantly reduced with the separated spacer, which indicates that the designed separated spacer can effectively reduce the heat-induced preload.
2023, 42(6): 870-877.
doi: 10.13433/j.cnki.1003-8728.20220016
Abstract:
In order to improve the existing problems in the compressed sensing equivalent source method for plates nearfield acoustic holography such as insufficient sparsity, small scope of application, a method of optimizing the range of equivalent source surface to filter the high wavenumber evanescent wave is proposed and the reconstruction error reduces. In this method, the plate vibration mode and the acoustic radiation mode are used to study the evanescent wave distribution area of the plate. The high wavenumber evanescent wave distribution is obtained by using the plate vibration mode, and the distribution of the equivalent source vector in the wavenumber domain is obtained by the acoustic radiation mode. The numerical simulation experimental results show that the present method increases the sparsity of the equivalent source vector, improves the reconstruction accuracy greatly and expands the application scope of compressed equivalent source method.
In order to improve the existing problems in the compressed sensing equivalent source method for plates nearfield acoustic holography such as insufficient sparsity, small scope of application, a method of optimizing the range of equivalent source surface to filter the high wavenumber evanescent wave is proposed and the reconstruction error reduces. In this method, the plate vibration mode and the acoustic radiation mode are used to study the evanescent wave distribution area of the plate. The high wavenumber evanescent wave distribution is obtained by using the plate vibration mode, and the distribution of the equivalent source vector in the wavenumber domain is obtained by the acoustic radiation mode. The numerical simulation experimental results show that the present method increases the sparsity of the equivalent source vector, improves the reconstruction accuracy greatly and expands the application scope of compressed equivalent source method.
2023, 42(6): 878-882.
doi: 10.13433/j.cnki.1003-8728.20220026
Abstract:
In order to realize the high frequency vibration of electro-hydraulic excitation system, a rotary directional valve is proposed and designed in this paper. The dynamic equation of the rotary directional valve is derived, and the dynamic response characteristics of the rotary directional valve are simulated by MATLAB. The effects of hydrodynamic moment, equivalent damping coefficient and moment of inertia on the dynamic response characteristics of the rotary directional valve are analyzed. The simulation results show that the damping coefficient, moment of inertia and hydrodynamic stiffness coefficient have great influence on the response speed, stability and operating bandwidth of the rotary directional valve, among which the hydrodynamic stiffness coefficient has the strongest influence on the rotary directional valve and the weakest degree of damping. The research results can provide basic data support for improving the response speed, stability and working bandwidth of the rotary directional valve and optimization orientation.
In order to realize the high frequency vibration of electro-hydraulic excitation system, a rotary directional valve is proposed and designed in this paper. The dynamic equation of the rotary directional valve is derived, and the dynamic response characteristics of the rotary directional valve are simulated by MATLAB. The effects of hydrodynamic moment, equivalent damping coefficient and moment of inertia on the dynamic response characteristics of the rotary directional valve are analyzed. The simulation results show that the damping coefficient, moment of inertia and hydrodynamic stiffness coefficient have great influence on the response speed, stability and operating bandwidth of the rotary directional valve, among which the hydrodynamic stiffness coefficient has the strongest influence on the rotary directional valve and the weakest degree of damping. The research results can provide basic data support for improving the response speed, stability and working bandwidth of the rotary directional valve and optimization orientation.
2023, 42(6): 883-889.
doi: 10.13433/j.cnki.1003-8728.20230034
Abstract:
Hot-rolled strip surface defect detection is an important task of intelligent detection in production process. Aiming at the low efficiency and poor real-time performance of the current hot-rolled strip surface defect detection algorithm, a lightweight object detector based on convolutional neural network is proposed. Based on the YOLOv4-tiny model, the present method combines the optimization strategy of multi-scale detection and spatial attention mechanism for the particularity of the surface defect detection of strip steel, which maintains the detection efficiency while improving the precision of lightweight object detectors. Experiments show that the improved YOLOv4-tiny model can accurately detect the surface defects of strip steel, the mAP (mean Average precision)value is of 73.29%, and the FPS (Frames per second) value reaches 163, which meets the real-time requirements of engineering application.
Hot-rolled strip surface defect detection is an important task of intelligent detection in production process. Aiming at the low efficiency and poor real-time performance of the current hot-rolled strip surface defect detection algorithm, a lightweight object detector based on convolutional neural network is proposed. Based on the YOLOv4-tiny model, the present method combines the optimization strategy of multi-scale detection and spatial attention mechanism for the particularity of the surface defect detection of strip steel, which maintains the detection efficiency while improving the precision of lightweight object detectors. Experiments show that the improved YOLOv4-tiny model can accurately detect the surface defects of strip steel, the mAP (mean Average precision)value is of 73.29%, and the FPS (Frames per second) value reaches 163, which meets the real-time requirements of engineering application.
2023, 42(6): 890-897.
doi: 10.13433/j.cnki.1003-8728.20220011
Abstract:
In order to study the relationship between the micro morphology characteristic parameters and the contact stress of rough surface, based on the definition standard ISO25178 of micro topography roughness parameters, the three-dimensional height parameters which are related to contact deformation were selected as the objects to build the relationship model with maximum Mises stress based on 220 sets of measured ultrasonic grinding surface by back propagation (BP) neural network. Then, the influence of the different height parameters on the maximum Mises stress was analyzed and the main parameters affecting maximum Mises stress were selected by Sobol and mean impact value (MIV) sensitivity analysis methods. Finally, the nonlinear regression model for height parameters selected above and the maximum Mises stress was established through statistical correlation principle and polynomial regression analysis method. The results show that: 1) The importance of all 7 height parameters to maximum Mises stress from large to small is as follows: arithmetic average height Sa , root mean square height Sq , skewness Ssk , maximum height Sz , maximum peak height Sp , maximum pit height Sv and kurtosis Sku ; 2) Based on 90% of total influence degree, the selected height parameters that play a major role in maximum Mises stress are: Sa, Sq and Ssk ; 3) Comparing with the ellipsoid contact algorithm, the relative error of regression model is less than 10%, and the calculation efficiency is greatly improved. These show that the model has a practical value.
In order to study the relationship between the micro morphology characteristic parameters and the contact stress of rough surface, based on the definition standard ISO25178 of micro topography roughness parameters, the three-dimensional height parameters which are related to contact deformation were selected as the objects to build the relationship model with maximum Mises stress based on 220 sets of measured ultrasonic grinding surface by back propagation (BP) neural network. Then, the influence of the different height parameters on the maximum Mises stress was analyzed and the main parameters affecting maximum Mises stress were selected by Sobol and mean impact value (MIV) sensitivity analysis methods. Finally, the nonlinear regression model for height parameters selected above and the maximum Mises stress was established through statistical correlation principle and polynomial regression analysis method. The results show that: 1) The importance of all 7 height parameters to maximum Mises stress from large to small is as follows: arithmetic average height Sa , root mean square height Sq , skewness Ssk , maximum height Sz , maximum peak height Sp , maximum pit height Sv and kurtosis Sku ; 2) Based on 90% of total influence degree, the selected height parameters that play a major role in maximum Mises stress are: Sa, Sq and Ssk ; 3) Comparing with the ellipsoid contact algorithm, the relative error of regression model is less than 10%, and the calculation efficiency is greatly improved. These show that the model has a practical value.
2023, 42(6): 898-905.
doi: 10.13433/j.cnki.1003-8728.20220044
Abstract:
In order to reduce the sensitivity of contact marks of an aviation spiral bevel gear to installation distance deviation (also called installation error), it is necessary to carry out its low sensitivity tooth surface optimization design. By introducing the installation error into the loaded tooth contact analysis (LTCA) technology, the error loaded tooth contact analysis (ELTCA) method that considers the installation error is proposed. Based on the ELTCA method, the internal relationship between tooth contact mark and installation error is established. With the help of the quantitative description of the contact mark, the sensitivity matrix of the tooth contact mark with respect to the installation error is obtained. Based on the local synthesis method, the objective function of sensitivity with respect to tooth contact parameters is established, and the low sensitivity tooth surface optimization design model of the spiral bevel gear is established. Using the neural network and the genetic algorithm to solve this optimization problem, the cutting parameters of low sensitivity tooth surface are obtained. The results show that the sensitivity of the optimized tooth contact mark to installation error is reduced by 78.87%.
In order to reduce the sensitivity of contact marks of an aviation spiral bevel gear to installation distance deviation (also called installation error), it is necessary to carry out its low sensitivity tooth surface optimization design. By introducing the installation error into the loaded tooth contact analysis (LTCA) technology, the error loaded tooth contact analysis (ELTCA) method that considers the installation error is proposed. Based on the ELTCA method, the internal relationship between tooth contact mark and installation error is established. With the help of the quantitative description of the contact mark, the sensitivity matrix of the tooth contact mark with respect to the installation error is obtained. Based on the local synthesis method, the objective function of sensitivity with respect to tooth contact parameters is established, and the low sensitivity tooth surface optimization design model of the spiral bevel gear is established. Using the neural network and the genetic algorithm to solve this optimization problem, the cutting parameters of low sensitivity tooth surface are obtained. The results show that the sensitivity of the optimized tooth contact mark to installation error is reduced by 78.87%.
2023, 42(6): 906-913.
doi: 10.13433/j.cnki.1003-8728.20230191
Abstract:
For the poor polishing quality, low polishing efficiency and serious environmental pollution in polishing of stainless steel via current methods, the micro-arc plasma discharge polishing method in the polishing of 304 stainless steel was proposed by combining the electrochemical processing with electrical discharge machining. The mechanism in the micro-arc plasma discharge polishing was studied based on the electrochemical and streamer theories. By planning the orthogonal tests and analyzing the testing results with Taguchi analysis and ANOVA, the optimal parameters by considering the material removal rate and surface roughness was obtained and verified through the experimental results. The results show that the voltage, polishing time and electrolyte temperature have the significant effects on the material removal rate, and the polishing time and voltage have the significant effects on the surface roughness. The maximum material removal rate in the micro-arc plasma discharge polishing of 304 stainless steel can reach 11.73 μm/min, and the minimum surface roughness can reach 29.1 nm.
For the poor polishing quality, low polishing efficiency and serious environmental pollution in polishing of stainless steel via current methods, the micro-arc plasma discharge polishing method in the polishing of 304 stainless steel was proposed by combining the electrochemical processing with electrical discharge machining. The mechanism in the micro-arc plasma discharge polishing was studied based on the electrochemical and streamer theories. By planning the orthogonal tests and analyzing the testing results with Taguchi analysis and ANOVA, the optimal parameters by considering the material removal rate and surface roughness was obtained and verified through the experimental results. The results show that the voltage, polishing time and electrolyte temperature have the significant effects on the material removal rate, and the polishing time and voltage have the significant effects on the surface roughness. The maximum material removal rate in the micro-arc plasma discharge polishing of 304 stainless steel can reach 11.73 μm/min, and the minimum surface roughness can reach 29.1 nm.
2023, 42(6): 914-922.
doi: 10.13433/j.cnki.1003-8728.20220037
Abstract:
In order to solve the problem that the recognition rate of new working conditions is low due to the limited working conditions category contained in the training samples in the practical application of drainage pipe blockage detection, a new voice print recognition model based on Refined Composite Multi-scale Dispersion Entropy and Gaussian Mixture Hidden Markov Model is proposed. Firstly, this method uses single-parameter dual-threshold endpoint detection algorithm based on sub-band spectral entropy to perform endpoint detection and signal segmentation for the sound pressure signal after noise reduction in single and complicated working conditions, and obtain sound pressure signals corresponding to blockage, lateral connection and pipe end in the pipeline. Then the refined composite multi-scale dispersion entropy features are extracted. Finally, the feature vectors of different types of individual sound pressure signals in a single working condition are used for model training, and the trained parameter model used for complex working conditions recognition of blockages, lateral connection and pipe end. The experimental results have shown that the proposed method can effectively identify blockages, pipe fittings such as lateral connection and pipe end under the condition of limited training sample categories, the comprehensive recognition rate is 93.75%, which verified that the voiceprint of the blockage has commonality under different working conditions, and it is different from lateral connection and pipe end and has certain engineering application value.
In order to solve the problem that the recognition rate of new working conditions is low due to the limited working conditions category contained in the training samples in the practical application of drainage pipe blockage detection, a new voice print recognition model based on Refined Composite Multi-scale Dispersion Entropy and Gaussian Mixture Hidden Markov Model is proposed. Firstly, this method uses single-parameter dual-threshold endpoint detection algorithm based on sub-band spectral entropy to perform endpoint detection and signal segmentation for the sound pressure signal after noise reduction in single and complicated working conditions, and obtain sound pressure signals corresponding to blockage, lateral connection and pipe end in the pipeline. Then the refined composite multi-scale dispersion entropy features are extracted. Finally, the feature vectors of different types of individual sound pressure signals in a single working condition are used for model training, and the trained parameter model used for complex working conditions recognition of blockages, lateral connection and pipe end. The experimental results have shown that the proposed method can effectively identify blockages, pipe fittings such as lateral connection and pipe end under the condition of limited training sample categories, the comprehensive recognition rate is 93.75%, which verified that the voiceprint of the blockage has commonality under different working conditions, and it is different from lateral connection and pipe end and has certain engineering application value.
2023, 42(6): 923-933.
doi: 10.13433/j.cnki.1003-8728.20220049
Abstract:
In order to solve the problem that the wear of crusher liner is difficult to predict, a new method for predicting the wear state of crusher liner based on LMS and BAS-LSSVM with improved half-pan tongue function is proposed. Firstly, based on the least mean square error (LMS) algorithm, an improved dustpan tongue function LMS was introduced to calculate the acoustic time (TOF) of the ultrasonic echo signal of the lining board. Secondly, the thickness of liner was calculated by TOF, and the wear amount was obtained according to the thickness change of liner before and after wear. Finally, a BAS-LSSVM liner wear prediction model was established by optimizing the penalty factor of least squares support vector machine (LSSVM) and the standardized parameters in its kernel function by using the Beetle Antennae Search algorithm (BAS). The wear amount was taken as the input of the prediction model, and the lining wear stage was taken as the output. The experimental results show that the identification accuracy of moving cone liner and fixed cone liner can reach 94.44% and 95.56% respectively, which can effectively predict the wear state of the crusher liner.
In order to solve the problem that the wear of crusher liner is difficult to predict, a new method for predicting the wear state of crusher liner based on LMS and BAS-LSSVM with improved half-pan tongue function is proposed. Firstly, based on the least mean square error (LMS) algorithm, an improved dustpan tongue function LMS was introduced to calculate the acoustic time (TOF) of the ultrasonic echo signal of the lining board. Secondly, the thickness of liner was calculated by TOF, and the wear amount was obtained according to the thickness change of liner before and after wear. Finally, a BAS-LSSVM liner wear prediction model was established by optimizing the penalty factor of least squares support vector machine (LSSVM) and the standardized parameters in its kernel function by using the Beetle Antennae Search algorithm (BAS). The wear amount was taken as the input of the prediction model, and the lining wear stage was taken as the output. The experimental results show that the identification accuracy of moving cone liner and fixed cone liner can reach 94.44% and 95.56% respectively, which can effectively predict the wear state of the crusher liner.
2023, 42(6): 934-938.
doi: 10.13433/j.cnki.1003-8728.20220033
Abstract:
This paper presents a fan condition monitoring method based on multi-sensor signal indexes. Firstly, a variety of commonly used sensors are used to pick up the signals of the fan, collect the signals of various sensors in different states, and calculate the indicators of the signals. Secondly, the principal component analysis is used to reduce the dimension of multi-sensor signal indexes, simplify the state detection model and extract the main component indexes which can represent the running state of the fan. Finally, the RNN, which has the advantage of learning the nonlinear characteristic indexes, is used to predict and analyze the fan state, so as to realize the effective monitoring of the fan state. Experimental results show the effectiveness of the present method.
This paper presents a fan condition monitoring method based on multi-sensor signal indexes. Firstly, a variety of commonly used sensors are used to pick up the signals of the fan, collect the signals of various sensors in different states, and calculate the indicators of the signals. Secondly, the principal component analysis is used to reduce the dimension of multi-sensor signal indexes, simplify the state detection model and extract the main component indexes which can represent the running state of the fan. Finally, the RNN, which has the advantage of learning the nonlinear characteristic indexes, is used to predict and analyze the fan state, so as to realize the effective monitoring of the fan state. Experimental results show the effectiveness of the present method.
2023, 42(6): 939-948.
doi: 10.13433/j.cnki.1003-8728.20230190
Abstract:
The living cabin environment of a ship has a significant impact on the psychological state and work efficiency of the crew, and optimizing the layout of the cabin is one of the important ways to improve the overall combat level of the fleet. This study mainly focuses on the layout optimization of the living cabin space inside ship, proposes the division method of modular thinking, and uses fuzzy cluster analysis to divide the cabin module, and uses the PGA algorithm to perform multi-objective optimization calculation, so as to guide the evolution results of the genetic algorithm to be more in line with its engineering practicability, so as to effectively improve the comfort of crew living and further improve the quality of long-distance navigation work at sea. Finally, the fuzzy comprehensive evaluation of center of gravity ordering verifies the optimization output scheme of living cabin.
The living cabin environment of a ship has a significant impact on the psychological state and work efficiency of the crew, and optimizing the layout of the cabin is one of the important ways to improve the overall combat level of the fleet. This study mainly focuses on the layout optimization of the living cabin space inside ship, proposes the division method of modular thinking, and uses fuzzy cluster analysis to divide the cabin module, and uses the PGA algorithm to perform multi-objective optimization calculation, so as to guide the evolution results of the genetic algorithm to be more in line with its engineering practicability, so as to effectively improve the comfort of crew living and further improve the quality of long-distance navigation work at sea. Finally, the fuzzy comprehensive evaluation of center of gravity ordering verifies the optimization output scheme of living cabin.
2023, 42(6): 949-955.
doi: 10.13433/j.cnki.1003-8728.20220038
Abstract:
Batteries are used as the energy source of a wheeled mobile robot, which is, however, limited. Based on the composition of energy consumption of the wheeled mobile robot in operation, its energy consumption model is established by integrating the motor efficiency, ground friction, terrain, speed change, turning and other factors. The optimal node A* algorithm for the path planning of the wheeled mobile robot under optimal energy consumption is proposed with the optimal node search method. The simulation results, compared with the path planning results of the A* algorithm under the shortest distance constraint and optimal energy consumption constraint, show that the optimal node A* algorithm can not only reduce the energy consumption per unit distance but also shorten the path-finding time, thus verifying its effectiveness.
Batteries are used as the energy source of a wheeled mobile robot, which is, however, limited. Based on the composition of energy consumption of the wheeled mobile robot in operation, its energy consumption model is established by integrating the motor efficiency, ground friction, terrain, speed change, turning and other factors. The optimal node A* algorithm for the path planning of the wheeled mobile robot under optimal energy consumption is proposed with the optimal node search method. The simulation results, compared with the path planning results of the A* algorithm under the shortest distance constraint and optimal energy consumption constraint, show that the optimal node A* algorithm can not only reduce the energy consumption per unit distance but also shorten the path-finding time, thus verifying its effectiveness.
2023, 42(6): 956-961.
doi: 10.13433/j.cnki.1003-8728.20220216
Abstract:
Ground test is one kind of the most important verification means for aircraft structures currently, in order to ensure the safety of complex lever loading system under large deformation of aircraft, the virtual assembly method was investigated and the virtual assembly template was set up based XML schema. A extensible model library was developed for the test equipments. the virtual assembly of the loading and supporting systems was realized on CATIA software. A iterative method was put forward to solve the equilibrium equation of lever loading system motion. The spatial position of loading equipment in each loading step was calculated according to the simulation deformation of aircraft structure. The motion simulation of loading equipment was realized by coordinate transformation, and the collision check of the lever loading system and supporting system was also carried out. The example shows that the collision problem can be found, which provides the technical support for test design and reduces the test risk.
Ground test is one kind of the most important verification means for aircraft structures currently, in order to ensure the safety of complex lever loading system under large deformation of aircraft, the virtual assembly method was investigated and the virtual assembly template was set up based XML schema. A extensible model library was developed for the test equipments. the virtual assembly of the loading and supporting systems was realized on CATIA software. A iterative method was put forward to solve the equilibrium equation of lever loading system motion. The spatial position of loading equipment in each loading step was calculated according to the simulation deformation of aircraft structure. The motion simulation of loading equipment was realized by coordinate transformation, and the collision check of the lever loading system and supporting system was also carried out. The example shows that the collision problem can be found, which provides the technical support for test design and reduces the test risk.
2023, 42(6): 962-968.
doi: 10.13433/j.cnki.1003-8728.20200563
Abstract:
Modern wind turbine has pitch control systemwhich alleviates aerodynamic loads.Trailing edge flap is a feasible aerodynamic load control device for airplane wings. However, therelevant techniques have not been fully developed. Therefore, the trailing edge flap has not been successfully applied to the wind turbine rotors. The dynamic lift caused by the combined motions of airfoil flap and pitch is simulated through numerical method. The trailing edge part is simulated with an immersed boundary method, and the other part of the airfoil is modeled by a traditional curvilinear mesh, which helps to simulate the trailing edge flap and meanwhile ensure high calculation efficiency. The results were thoroughly compared with the existing wind tunnel experiments. Relatively good agreements were achieved which provide the references for developing the smart blades with trailing edge flaps.
Modern wind turbine has pitch control systemwhich alleviates aerodynamic loads.Trailing edge flap is a feasible aerodynamic load control device for airplane wings. However, therelevant techniques have not been fully developed. Therefore, the trailing edge flap has not been successfully applied to the wind turbine rotors. The dynamic lift caused by the combined motions of airfoil flap and pitch is simulated through numerical method. The trailing edge part is simulated with an immersed boundary method, and the other part of the airfoil is modeled by a traditional curvilinear mesh, which helps to simulate the trailing edge flap and meanwhile ensure high calculation efficiency. The results were thoroughly compared with the existing wind tunnel experiments. Relatively good agreements were achieved which provide the references for developing the smart blades with trailing edge flaps.
2023, 42(6): 969-977.
doi: 10.13433/j.cnki.1003-8728.20220009
Abstract:
In a bolted rotor with curvic couplings, the structure integrity of curvic coupling tooth may be damaged and local stress concentration may occur due to bolt holes. An optimization model for the power turbine bolted rotor with curvic couplings was established by considering the bolt axial preloading. Then the structure optimization design of power turbine rotor curvic coupling was completed based on ANSYS optimization platform. The results showed that the strength weakening effect of the bolt holes on the tooth root of curvic couplings is greater than that of concave (convex) tooth itself, and the bolt holes radial distribution near the pitch diameter of curvic couplings was beneficial to reduce the stress and improve the stress distribution of curvic couplings. Comparing with the original design, the maximum equivalent stress of the optimum curvic couplings was reduced by 9.1% and the max contact stress on the working face was reduced by 44.6%, which improves the tooth root stress distribution more homogenous and has no effect on the global deformation of the whole power turbine rotor.
In a bolted rotor with curvic couplings, the structure integrity of curvic coupling tooth may be damaged and local stress concentration may occur due to bolt holes. An optimization model for the power turbine bolted rotor with curvic couplings was established by considering the bolt axial preloading. Then the structure optimization design of power turbine rotor curvic coupling was completed based on ANSYS optimization platform. The results showed that the strength weakening effect of the bolt holes on the tooth root of curvic couplings is greater than that of concave (convex) tooth itself, and the bolt holes radial distribution near the pitch diameter of curvic couplings was beneficial to reduce the stress and improve the stress distribution of curvic couplings. Comparing with the original design, the maximum equivalent stress of the optimum curvic couplings was reduced by 9.1% and the max contact stress on the working face was reduced by 44.6%, which improves the tooth root stress distribution more homogenous and has no effect on the global deformation of the whole power turbine rotor.
2023, 42(6): 978-984.
doi: 10.13433/j.cnki.1003-8728.20220085
Abstract:
In order to solve the vibration reduction design problem of low-pressure rotor of a small turbofan engine, a comparative experimental investigation on the vibration attenuating characteristics of concentric and non-concentric squeeze film dampers (SFD)was carried out. A low-pressure simulated rotor which is consistent with the main structure and dynamic characteristics of low-pressure rotor was designed. On a high-speed rotating tester, the dynamic characteristics of low-pressure simulated rotor with concentric SFD and non-concentric SFD were tested in the full speed range, and the effects of oil film supply pressure and unbalance on the vibration attenuating characteristics of SFD were studied. Theexperimental results show that non-concentric SFD will reduce the critical speed of rotor system. Compared with concentric SFD, the damping characteristics of non-concentric SFD are more sensitive to the oil film supply pressure. Concentric SFD can withstand greater unbalance than non-concentric SFD, but non-concentric SFD has better vibration reduction effect in a small range of unbalance.
In order to solve the vibration reduction design problem of low-pressure rotor of a small turbofan engine, a comparative experimental investigation on the vibration attenuating characteristics of concentric and non-concentric squeeze film dampers (SFD)was carried out. A low-pressure simulated rotor which is consistent with the main structure and dynamic characteristics of low-pressure rotor was designed. On a high-speed rotating tester, the dynamic characteristics of low-pressure simulated rotor with concentric SFD and non-concentric SFD were tested in the full speed range, and the effects of oil film supply pressure and unbalance on the vibration attenuating characteristics of SFD were studied. Theexperimental results show that non-concentric SFD will reduce the critical speed of rotor system. Compared with concentric SFD, the damping characteristics of non-concentric SFD are more sensitive to the oil film supply pressure. Concentric SFD can withstand greater unbalance than non-concentric SFD, but non-concentric SFD has better vibration reduction effect in a small range of unbalance.
