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RSS2020 Vol. 39, No. 2
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2020, 39(2): 165-173.
doi: 10.13433/j.cnki.1003-8728.20190111
PDF 1402KB
Abstract:
In this paper, a new fault diagnosis method for rolling bearings based on minimum entropy deconvolution (MED) and generalized minimax concave penalty (GMCP) sparse enhanced signal decomposition is proposed. First, root mean square error (RMSE) is introduced to quantitatively analyze the advantages of GMCP effectively retaining periodic impact. Then MED and GMCP are applied to the fault diagnosis of rolling bearings. This method can effectively separate the noise and interference frequencies of equipment vibration signals and retain the periodic impulse frequencies completely. It is very effective for the fault diagnosis of rolling bearings, and it also has advantages in the identification of fault characteristic spectrum. The competitiveness of this method in fault diagnosis of rolling bearings is verified by simulation and experiment.
In this paper, a new fault diagnosis method for rolling bearings based on minimum entropy deconvolution (MED) and generalized minimax concave penalty (GMCP) sparse enhanced signal decomposition is proposed. First, root mean square error (RMSE) is introduced to quantitatively analyze the advantages of GMCP effectively retaining periodic impact. Then MED and GMCP are applied to the fault diagnosis of rolling bearings. This method can effectively separate the noise and interference frequencies of equipment vibration signals and retain the periodic impulse frequencies completely. It is very effective for the fault diagnosis of rolling bearings, and it also has advantages in the identification of fault characteristic spectrum. The competitiveness of this method in fault diagnosis of rolling bearings is verified by simulation and experiment.
2020, 39(2): 174-179.
doi: 10.13433/j.cnki.1003-8728.20190097
Abstract:
In order to operate on prostate needle-insertion surgery under the magnetic resonance environment, a new robot structure for acupuncture surgery was designed based on the clinical requirements and various types of ultrasonic motors. Firstly, based on the principle of RCM(remote center of motion), related improvement is added to the needle-insertion module; the friction resistance of the needle-insertion process can be reduced because of piezoelectric anti-friction device. Then the forward and inverse kinematics equations are solved by D-H (Denavit-Hartenberg)parameter method, and the workspace of the robot is solved by Monte Carlo method. Finally, the kinematics equation is verified by MATLAB software, and the robot joint Kinematics performance is simulated. Analysis and verification are completed; it is proved that the robot meets the design requirements under the magnetic resonance environment.
In order to operate on prostate needle-insertion surgery under the magnetic resonance environment, a new robot structure for acupuncture surgery was designed based on the clinical requirements and various types of ultrasonic motors. Firstly, based on the principle of RCM(remote center of motion), related improvement is added to the needle-insertion module; the friction resistance of the needle-insertion process can be reduced because of piezoelectric anti-friction device. Then the forward and inverse kinematics equations are solved by D-H (Denavit-Hartenberg)parameter method, and the workspace of the robot is solved by Monte Carlo method. Finally, the kinematics equation is verified by MATLAB software, and the robot joint Kinematics performance is simulated. Analysis and verification are completed; it is proved that the robot meets the design requirements under the magnetic resonance environment.
2020, 39(2): 180-186.
doi: 10.13433/j.cnki.1003-8728.20190120
Abstract:
In order to reveal the coupling relationship among bifurcation, gear meshing impact, tooth mesh apart, tooth back-side contact and dynamic load coefficient (DLC) of the nonlinear gear system, the pseudo color maps of meshing impact and period, duty cycle of the mesh apart (DC1), duty cycle of the tooth back-side contact (DC2) and DLC for a single-stage spur gear system were obtained by CPNF (continue Poincaré-Newton-Floquet) in dimensionless backlash- frequency plane. The results indicate that the system exhibits complex comprehensive dynamic characteristics under the coupling of clearance and frequency. With the change of backlash and frequency, the periodic motion of the system turns to chaos by the way of period-doubling, Hopf, crisis, grazing and saddle node bifurcation. The abrupt change of bifurcation and meshing impact leads to step increase of DC1, DC2 and DLC. DC1, DC2 and DLC reach the extreme value due to the influence of chaos, quasi periodic motion and bilateral impact within the scope of the resonance frequency and small gap. These dynamic characteristics transition laws can provide the theoretical reference for the optimization of the gear structure parameter.
In order to reveal the coupling relationship among bifurcation, gear meshing impact, tooth mesh apart, tooth back-side contact and dynamic load coefficient (DLC) of the nonlinear gear system, the pseudo color maps of meshing impact and period, duty cycle of the mesh apart (DC1), duty cycle of the tooth back-side contact (DC2) and DLC for a single-stage spur gear system were obtained by CPNF (continue Poincaré-Newton-Floquet) in dimensionless backlash- frequency plane. The results indicate that the system exhibits complex comprehensive dynamic characteristics under the coupling of clearance and frequency. With the change of backlash and frequency, the periodic motion of the system turns to chaos by the way of period-doubling, Hopf, crisis, grazing and saddle node bifurcation. The abrupt change of bifurcation and meshing impact leads to step increase of DC1, DC2 and DLC. DC1, DC2 and DLC reach the extreme value due to the influence of chaos, quasi periodic motion and bilateral impact within the scope of the resonance frequency and small gap. These dynamic characteristics transition laws can provide the theoretical reference for the optimization of the gear structure parameter.
2020, 39(2): 187-193.
doi: 10.13433/j.cnki.1003-8728.20190123
Abstract:
To study the elasto-plastic contact behavior in the meshing process of rough tooth surface, an elasto-plastic contact algorithm for rough curved surface is proposed based on the ZMC model. For reducing the effect of the sampling interval in the contact modeling, the rough tooth surface topography is pretreated by using the micro topography fitting method. In a way, the asperity distribution parameters can be obtained steadily. The present elasto-plastic contact algorithm is implemented by using the measured tooth surface topography in gear meshing process. The variations of the contact results between those from elastic contact analysis and those from elasto-plastic contact analysis under different conditions are compared, the clues for contact behavior prediction in the gear meshing process is provided
To study the elasto-plastic contact behavior in the meshing process of rough tooth surface, an elasto-plastic contact algorithm for rough curved surface is proposed based on the ZMC model. For reducing the effect of the sampling interval in the contact modeling, the rough tooth surface topography is pretreated by using the micro topography fitting method. In a way, the asperity distribution parameters can be obtained steadily. The present elasto-plastic contact algorithm is implemented by using the measured tooth surface topography in gear meshing process. The variations of the contact results between those from elastic contact analysis and those from elasto-plastic contact analysis under different conditions are compared, the clues for contact behavior prediction in the gear meshing process is provided
2020, 39(2): 194-200.
doi: 10.13433/j.cnki.1003-8728.20190119
Abstract:
In order to enhance the stiffness performance of an incompletely restrained cable-driven parallel mechanism, this paper studies a stiffness-based optimization method. Firstly, the parallel mechanism's static equations are used to analyze its force and a line vector and a differential transform are introduced to deduce its static stiffness model. Then, two design variables are defined, the optimal design with respect to workspace, global average value of stiffness and global volatility of stiffness are carried out and analyzed. Finally, the multi-objective optimization of the parallel mechanism is implemented by using the ideal point method and the objective functions are normalized to obtain the best structural parameters.
In order to enhance the stiffness performance of an incompletely restrained cable-driven parallel mechanism, this paper studies a stiffness-based optimization method. Firstly, the parallel mechanism's static equations are used to analyze its force and a line vector and a differential transform are introduced to deduce its static stiffness model. Then, two design variables are defined, the optimal design with respect to workspace, global average value of stiffness and global volatility of stiffness are carried out and analyzed. Finally, the multi-objective optimization of the parallel mechanism is implemented by using the ideal point method and the objective functions are normalized to obtain the best structural parameters.
2020, 39(2): 201-206.
doi: 10.13433/j.cnki.1003-8728.20190112
Abstract:
For an accurate evaluation of wind turbine gearbox condition, a kind of based on the kernel principal component analysis (KPCA) and least squares support vector machines (LS-SVM) combined with gearbox data fusion fault prediction model is put forward, in terms of the uncertainty of SCADA system data in the information quality and redundancy, firstly the model for monitoring data preprocessing (quartile method, a method to eliminate abnormal data), the correlation analysis was carried out on the gear box characteristic factors, by using the forecast method of gearbox typical state characteristics (vibration, temperature characteristics, etc.). By using the theory of statistical process control (SPC) analysis of the residual, the abnormal condition of gear box is predicted. Finally, the model for the accuracy and effectiveness are verified by taking the oil temperature prediction of gearbox as an example.
For an accurate evaluation of wind turbine gearbox condition, a kind of based on the kernel principal component analysis (KPCA) and least squares support vector machines (LS-SVM) combined with gearbox data fusion fault prediction model is put forward, in terms of the uncertainty of SCADA system data in the information quality and redundancy, firstly the model for monitoring data preprocessing (quartile method, a method to eliminate abnormal data), the correlation analysis was carried out on the gear box characteristic factors, by using the forecast method of gearbox typical state characteristics (vibration, temperature characteristics, etc.). By using the theory of statistical process control (SPC) analysis of the residual, the abnormal condition of gear box is predicted. Finally, the model for the accuracy and effectiveness are verified by taking the oil temperature prediction of gearbox as an example.
2020, 39(2): 207-213.
doi: 10.13433/j.cnki.1003-8728.20190101
Abstract:
In order to optimize the vehicle handling and stability, a cooperative controller was designed for active rear wheel steering (ARS) and dual-motor distributed drive system direct-yaw-moment-control (DYC), and which was applied to FSAE racing car. Firstly, a two-degree-of-freedom linear vehicle dynamic model is constructed. Secondly, based on the sliding mode variable structure control (SM-VSC), a cooperative controller was designed by consisting of ARS controller and DYC controller. The ARS controller controls rear steering angle to minimize the side slip angle, while the DYC controller optimizes yaw rate via controlling the distribution of driving moment between the two rear driving wheels. Finally, the simulation of double lane change was performed to investigate the effectiveness of the present strategy on the improving cornering performance.
In order to optimize the vehicle handling and stability, a cooperative controller was designed for active rear wheel steering (ARS) and dual-motor distributed drive system direct-yaw-moment-control (DYC), and which was applied to FSAE racing car. Firstly, a two-degree-of-freedom linear vehicle dynamic model is constructed. Secondly, based on the sliding mode variable structure control (SM-VSC), a cooperative controller was designed by consisting of ARS controller and DYC controller. The ARS controller controls rear steering angle to minimize the side slip angle, while the DYC controller optimizes yaw rate via controlling the distribution of driving moment between the two rear driving wheels. Finally, the simulation of double lane change was performed to investigate the effectiveness of the present strategy on the improving cornering performance.
2020, 39(2): 214-220.
doi: 10.13433/j.cnki.1003-8728.20190118
Abstract:
For the function of recovering braking energy and preventing the wheel from driving wheels slipping of electric vehicles during in the emergency braking, the electromechanical coordinated anti-lock control strategy with the priority of the regenerative braking torque was proposed, that is, in any braking condition, as long as the regenerative braking torque is effective, regenerative braking torque is preferred to prevent the driving wheel from being locked. Firstly, the working mode and braking force distribution principle of this control strategy were analyzed, and its corresponding control logic is given. Then, taking the 1/4 electric vehicle model as an example, the dynamic mathematical model of regenerative ABS being given priority to be activated was established, and the PID control law based on wheel slip ratio was designed. On this basis, the corresponding MATLAB/SIMULINK model of the control strategy was established. Simulation results show that the proposed control strategy is feasible, and with the increase of the road surface adhesion coefficient, the braking mode will be changed from purely regenerative ABS to electromechanical composite regenerative ABS with the priority of the regenerative braking torque to be used, and the mechanical braking torque will be also increased accordingly. Secondly, the comparative simulation with the traditional hydraulic ABS shows that the control strategy can increase the reaction speed of the brake system by at least 21.8% and the brake distance of the vehicle by 4.9%.
For the function of recovering braking energy and preventing the wheel from driving wheels slipping of electric vehicles during in the emergency braking, the electromechanical coordinated anti-lock control strategy with the priority of the regenerative braking torque was proposed, that is, in any braking condition, as long as the regenerative braking torque is effective, regenerative braking torque is preferred to prevent the driving wheel from being locked. Firstly, the working mode and braking force distribution principle of this control strategy were analyzed, and its corresponding control logic is given. Then, taking the 1/4 electric vehicle model as an example, the dynamic mathematical model of regenerative ABS being given priority to be activated was established, and the PID control law based on wheel slip ratio was designed. On this basis, the corresponding MATLAB/SIMULINK model of the control strategy was established. Simulation results show that the proposed control strategy is feasible, and with the increase of the road surface adhesion coefficient, the braking mode will be changed from purely regenerative ABS to electromechanical composite regenerative ABS with the priority of the regenerative braking torque to be used, and the mechanical braking torque will be also increased accordingly. Secondly, the comparative simulation with the traditional hydraulic ABS shows that the control strategy can increase the reaction speed of the brake system by at least 21.8% and the brake distance of the vehicle by 4.9%.
2020, 39(2): 221-227.
doi: 10.13433/j.cnki.1003-8728.20190125
Abstract:
Aiming at the fatigue cracking of yaw brake cylinder of wind turbine, the relationship between the yaw operation and the yaw braking times of 24 wind turbines are analyzed based on the operational monitoring data of a Hunan wind farm SCADA (supervisory control and data acquisition). The yaw operation cycle is obtained by using the non-parametric estimation method. The finite element model for yaw brake system is established via ABAQUS. The load spectrum of yaw brake cylinder is formulated. According to the GL specification, the brake cylinder is checked. Based on the nCode Design-Life, the fatigue life analysis is carried out, and the influence of the two adjacent cylinder walls thickness on the fatigue life is studied. The results show that the thickness of two adjacent cylinder walls has a significant influence on the fatigue life. The fatigue life of yaw brake cylinder can be prolonged by optimizing the cylinder walls thickness.
Aiming at the fatigue cracking of yaw brake cylinder of wind turbine, the relationship between the yaw operation and the yaw braking times of 24 wind turbines are analyzed based on the operational monitoring data of a Hunan wind farm SCADA (supervisory control and data acquisition). The yaw operation cycle is obtained by using the non-parametric estimation method. The finite element model for yaw brake system is established via ABAQUS. The load spectrum of yaw brake cylinder is formulated. According to the GL specification, the brake cylinder is checked. Based on the nCode Design-Life, the fatigue life analysis is carried out, and the influence of the two adjacent cylinder walls thickness on the fatigue life is studied. The results show that the thickness of two adjacent cylinder walls has a significant influence on the fatigue life. The fatigue life of yaw brake cylinder can be prolonged by optimizing the cylinder walls thickness.
2020, 39(2): 228-234.
doi: 10.13433/j.cnki.1003-8728.20190115
Abstract:
To investigate the vibration and noise problem of high-speed train disc brake system, a finite element model of train disc brake system with real size is created. Both the complex eigenvalue analysis and transient dynamic analysis are performed by using Abaqus, and the results obtained via both analysis methods are compared. It is found that results obtained from complex eigenvalue analysis will occur "over-prediction", which indicates that the transient dynamic analysis should be more accruable and suitable in solving the vibration problem of high-speed train. Additionally, transient dynamic analysis is conducted to study the relationship between the system parameters and brake vibration behaviors. The results show that the reduction of the elastic modulus of the brake clamps is beneficial for reducing the vibration amplitude of the brake system and accordingly suppress the main vibration frequency of the system. The elastic modulus of brake disc support will not affect the normal vibration characteristics of the brake system. However, the tangential vibration amplitude will be reduced with the decrease of the elastic modulus of brake disc support. The vibration intensity of the braking system can be effectively reduced after the surface of brake disc is processed with grooves, and the energy of the vibration signal at the main frequency can be weakened. However, this manufacture method for the pad may bring the problems of excessive local stress and the local wear.
To investigate the vibration and noise problem of high-speed train disc brake system, a finite element model of train disc brake system with real size is created. Both the complex eigenvalue analysis and transient dynamic analysis are performed by using Abaqus, and the results obtained via both analysis methods are compared. It is found that results obtained from complex eigenvalue analysis will occur "over-prediction", which indicates that the transient dynamic analysis should be more accruable and suitable in solving the vibration problem of high-speed train. Additionally, transient dynamic analysis is conducted to study the relationship between the system parameters and brake vibration behaviors. The results show that the reduction of the elastic modulus of the brake clamps is beneficial for reducing the vibration amplitude of the brake system and accordingly suppress the main vibration frequency of the system. The elastic modulus of brake disc support will not affect the normal vibration characteristics of the brake system. However, the tangential vibration amplitude will be reduced with the decrease of the elastic modulus of brake disc support. The vibration intensity of the braking system can be effectively reduced after the surface of brake disc is processed with grooves, and the energy of the vibration signal at the main frequency can be weakened. However, this manufacture method for the pad may bring the problems of excessive local stress and the local wear.
2020, 39(2): 235-240.
doi: 10.13433/j.cnki.1003-8728.20190116
Abstract:
Aiming at the existing national standard method for uncertainty analysis of workpiece measurement error not to simplify calculation and avoid distribution hypothesis, a new method for evaluating uncertainty considering roundness error is studied. Firstly, the least squares fitting method is used to evaluate the error. Then, the optimal estimation of roundness error probability density function (PDF) is solved by using maximum entropy principle and particle swarm optimization (PSO). Finally, the roundness error uncertainty is evaluated by numerical integration and compared with the evaluation by GUM and Monte Carlo method (MCM). The results show that PDF estimation method can evaluate the roundness error uncertainty with small sample data and no distribution assumption, and the algorithm has good convergence and stable estimation.
Aiming at the existing national standard method for uncertainty analysis of workpiece measurement error not to simplify calculation and avoid distribution hypothesis, a new method for evaluating uncertainty considering roundness error is studied. Firstly, the least squares fitting method is used to evaluate the error. Then, the optimal estimation of roundness error probability density function (PDF) is solved by using maximum entropy principle and particle swarm optimization (PSO). Finally, the roundness error uncertainty is evaluated by numerical integration and compared with the evaluation by GUM and Monte Carlo method (MCM). The results show that PDF estimation method can evaluate the roundness error uncertainty with small sample data and no distribution assumption, and the algorithm has good convergence and stable estimation.
2020, 39(2): 241-246.
doi: 10.13433/j.cnki.1003-8728.20190114
Abstract:
A new meta-heuristic algorithm, whale swarm algorithm (WSA) is proposed for solving the flexible job shop scheduling problem(FJSP) with the objective to minimize the makespan. In the WSA, whale individual position vector can be updated by using the guidance of its better and most recent whale, the range of whale individual movements can be controlled by the ultrasonic intensity, because of this iteration method, it shows superiority in global searching ability and maintaining population diversity when solving various standard functions. Firstly, a two-segment string is used to describe the FJSP as two sub-problems, machine assignment and operation sequence. Secondly, the conversion method between the whale individual position vector and the scheduling solution is applied, and then the population can be updated and searched for optimization via WSA. Finally, the experimental data show that the present WSA is effective for solving the FJSP.
A new meta-heuristic algorithm, whale swarm algorithm (WSA) is proposed for solving the flexible job shop scheduling problem(FJSP) with the objective to minimize the makespan. In the WSA, whale individual position vector can be updated by using the guidance of its better and most recent whale, the range of whale individual movements can be controlled by the ultrasonic intensity, because of this iteration method, it shows superiority in global searching ability and maintaining population diversity when solving various standard functions. Firstly, a two-segment string is used to describe the FJSP as two sub-problems, machine assignment and operation sequence. Secondly, the conversion method between the whale individual position vector and the scheduling solution is applied, and then the population can be updated and searched for optimization via WSA. Finally, the experimental data show that the present WSA is effective for solving the FJSP.
2020, 39(2): 247-252.
doi: 10.13433/j.cnki.1003-8728.20190122
Abstract:
In order to extract gear fault features effectively form early fault vibration signals, a new method of gear fault feature extraction based on multipoint optimal minimum entropy deconvolution adjusted (MOMEDA) and mathematical morphological filtering is proposed, aiming at the non-linear, non-stationary and low signal-to-noise ratio characteristics of gear early fault vibration signals. Firstly, the periodic fault features in the signal are recovered by MOMEDA and the noise of the signal is reduced. Then the morphological difference filter is used to filter the deconvolution signal to enhance the impact characteristics in the signal. Finally, the spectrum of the filtering results is obtained to extract the gear fault features. The simulation and experimental results show that the method has the ability to suppress noise and extract periodic impact features and can realize the extraction of gear fault features.
In order to extract gear fault features effectively form early fault vibration signals, a new method of gear fault feature extraction based on multipoint optimal minimum entropy deconvolution adjusted (MOMEDA) and mathematical morphological filtering is proposed, aiming at the non-linear, non-stationary and low signal-to-noise ratio characteristics of gear early fault vibration signals. Firstly, the periodic fault features in the signal are recovered by MOMEDA and the noise of the signal is reduced. Then the morphological difference filter is used to filter the deconvolution signal to enhance the impact characteristics in the signal. Finally, the spectrum of the filtering results is obtained to extract the gear fault features. The simulation and experimental results show that the method has the ability to suppress noise and extract periodic impact features and can realize the extraction of gear fault features.
2020, 39(2): 253-257.
doi: 10.13433/j.cnki.1003-8728.20190336
Abstract:
Methylimidazole was grafted onto the molecular chain of chlorinated paraffin (CP) to synthesize chlorinated paraffin-based supported ionic liquids (CP-mimCl) through molecular structural design, which was used in extreme pressure and antiwear field by compounding with base oil. The experiment results showed that the maximum decomposition temperature of CP-mimCl increased by 24 ℃, the maximum decomposition rate decreased by 3.2%/min, and also showed the characteristics of uniform weightlessness. Compared with CP composite solution, the average wear spot diameter of CP-mimCl composite solution decreased by 6.8%, 7.7%, 7.3% under different loads, friction coefficient decreased by 36.2%, and the average pB increased by 15.7%. The results of SEM showed that the wear spot morphology by CP-mimCl composite solution was more dense and delicate than that by CP composite solution.
Methylimidazole was grafted onto the molecular chain of chlorinated paraffin (CP) to synthesize chlorinated paraffin-based supported ionic liquids (CP-mimCl) through molecular structural design, which was used in extreme pressure and antiwear field by compounding with base oil. The experiment results showed that the maximum decomposition temperature of CP-mimCl increased by 24 ℃, the maximum decomposition rate decreased by 3.2%/min, and also showed the characteristics of uniform weightlessness. Compared with CP composite solution, the average wear spot diameter of CP-mimCl composite solution decreased by 6.8%, 7.7%, 7.3% under different loads, friction coefficient decreased by 36.2%, and the average pB increased by 15.7%. The results of SEM showed that the wear spot morphology by CP-mimCl composite solution was more dense and delicate than that by CP composite solution.
2020, 39(2): 258-266.
doi: 10.13433/j.cnki.1003-8728.20190113
Abstract:
Being based on the theory of deep learning, one-dimensional Convolutional Neural Networks is applied to fault diagnosis of bearing vibration signals. Compared with traditional methods, extraction feature is simple and efficient. In order to further optimize the one-dimensional convolution structure, smooth over its search mode at all positions of the signal, and connect the fault characteristics in the period, a new DSCNN-GRU network model is proposed. The model combines the lightweight and fast of Depthwise Separable Convolution, and reduces the structural parameters of one-dimensional convolution. By adding gating mechanism, the signal characteristics of fault points can be memorized and analyzed, and the signal relationship in the period can be linked to better capture the signal fault characteristics and enhance the sensitivity of temporal series. An Adam algorithm for tracking gradient optimization is proposed to solve the problem of model with time windows oscillation. The data collected from the reducer rolling bearing shows that the average fault recognition rate of the algorithm can reach more than 94%, the classification effect is obvious, and the generalization ability is stronger.
Being based on the theory of deep learning, one-dimensional Convolutional Neural Networks is applied to fault diagnosis of bearing vibration signals. Compared with traditional methods, extraction feature is simple and efficient. In order to further optimize the one-dimensional convolution structure, smooth over its search mode at all positions of the signal, and connect the fault characteristics in the period, a new DSCNN-GRU network model is proposed. The model combines the lightweight and fast of Depthwise Separable Convolution, and reduces the structural parameters of one-dimensional convolution. By adding gating mechanism, the signal characteristics of fault points can be memorized and analyzed, and the signal relationship in the period can be linked to better capture the signal fault characteristics and enhance the sensitivity of temporal series. An Adam algorithm for tracking gradient optimization is proposed to solve the problem of model with time windows oscillation. The data collected from the reducer rolling bearing shows that the average fault recognition rate of the algorithm can reach more than 94%, the classification effect is obvious, and the generalization ability is stronger.
2020, 39(2): 267-272.
doi: 10.13433/j.cnki.1003-8728.20190117
Abstract:
The simulation of magnetic field with ANSYS software is carried out to obtain the curve diagram of the magnetic induction intensity of the magnetorheological damper under the conditions of different magnetofluid channel gaps, magnetic pole length, magnetic pole shape and magnetic loop thickness. The simulation results show that the response time of the magnetorheological damper increases with the increase of magnetic field and that the response time decreases with the increase of magnetic pole length. The response time is the shortest when the shape of the magnetic pole surface is flat and there is an arc chamfer. When the magnetic field of the piston is unsaturated, the response time increases with the increase of the thickness of the magnetic circuit, but when its magnetic field is saturated, the thickness of the magnetic loop has no effect on the response time of the magnetorheological damper.
The simulation of magnetic field with ANSYS software is carried out to obtain the curve diagram of the magnetic induction intensity of the magnetorheological damper under the conditions of different magnetofluid channel gaps, magnetic pole length, magnetic pole shape and magnetic loop thickness. The simulation results show that the response time of the magnetorheological damper increases with the increase of magnetic field and that the response time decreases with the increase of magnetic pole length. The response time is the shortest when the shape of the magnetic pole surface is flat and there is an arc chamfer. When the magnetic field of the piston is unsaturated, the response time increases with the increase of the thickness of the magnetic circuit, but when its magnetic field is saturated, the thickness of the magnetic loop has no effect on the response time of the magnetorheological damper.
2020, 39(2): 273-281.
doi: 10.13433/j.cnki.1003-8728.20190129
Abstract:
The relationship between subjective and objective evaluation of automobile seat comfort has the characteristics of complexity and high nonlinearity. The traditional BP neural networks (back propagation neural networks) are sensitive to weighted initial values and easily converge to local minimal value. Therefore, it is difficult to establish an accurate seat comfort prediction model. To solve the problem, this paper proposes a method for predicting automobile seat comfort by using the BP neural networks optimized by artificial bee colony algorithm. 176 groups of pressure distribution sample data were obtained through automobile body pressure test, 89% of which were used to train the model; 11% were used as model validation. Compared with the results predicted with real values, the results predicted with our method reach 0.0019 in mean square error and 0.946 in determination coefficient; the mean square error is 84.68% lower than that obtained with the BP neural network algorithm and the R2 (determination coefficient) is 42.5% higher than that obtained with the BP neural network algorithm. The results show that the prediction model of automobile seat comfort based on the BP neural networks optimized by the artificial bee colony algorithm is more stable and accurate.
The relationship between subjective and objective evaluation of automobile seat comfort has the characteristics of complexity and high nonlinearity. The traditional BP neural networks (back propagation neural networks) are sensitive to weighted initial values and easily converge to local minimal value. Therefore, it is difficult to establish an accurate seat comfort prediction model. To solve the problem, this paper proposes a method for predicting automobile seat comfort by using the BP neural networks optimized by artificial bee colony algorithm. 176 groups of pressure distribution sample data were obtained through automobile body pressure test, 89% of which were used to train the model; 11% were used as model validation. Compared with the results predicted with real values, the results predicted with our method reach 0.0019 in mean square error and 0.946 in determination coefficient; the mean square error is 84.68% lower than that obtained with the BP neural network algorithm and the R2 (determination coefficient) is 42.5% higher than that obtained with the BP neural network algorithm. The results show that the prediction model of automobile seat comfort based on the BP neural networks optimized by the artificial bee colony algorithm is more stable and accurate.
2020, 39(2): 282-287.
doi: 10.13433/j.cnki.1003-8728.20190121
Abstract:
To strengthen the relationship between the hoisting wirerope fault and the hoisting wirerope tension of multi-rope friction lifting system, a fault detection model based on support vector machine(SVM) and least squares support vector machine(LSSVM) was proposed. The particle swarm optimization algorithm (PSO) was used to optimize the model parameters to obtain the support vector machine diagnostic model with optimal parameters in MATLAB. Three kinds of faults and normal state tests were carried out in the lifting system of a mine. The PSO-SVM and PSO-LSSVM were trained and predicted by the wirerope fault data. The results showed the error and the mean square error of the PSO-SVM is smaller, and the PSO-LSSVM is faster, and both algorithms have good detection capabilities.
To strengthen the relationship between the hoisting wirerope fault and the hoisting wirerope tension of multi-rope friction lifting system, a fault detection model based on support vector machine(SVM) and least squares support vector machine(LSSVM) was proposed. The particle swarm optimization algorithm (PSO) was used to optimize the model parameters to obtain the support vector machine diagnostic model with optimal parameters in MATLAB. Three kinds of faults and normal state tests were carried out in the lifting system of a mine. The PSO-SVM and PSO-LSSVM were trained and predicted by the wirerope fault data. The results showed the error and the mean square error of the PSO-SVM is smaller, and the PSO-LSSVM is faster, and both algorithms have good detection capabilities.
2020, 39(2): 288-294.
doi: 10.13433/j.cnki.1003-8728.20190103
Abstract:
In order to remove or suppress the noise in the output displacement signal of the giant magnetostrictive actuator, the output displacement signal was processed and denoised based on the morphological component analysis theory. Because of the potential shortcomings of threshold processing in morphological component analysis algorithm, this paper proposes the fuzzy morphological component analysis algorithm by constructing fuzzy threshold function. Simulation and experimental results show that, from the comparison of the signals after de-noising, the noise of the output displacement signal is basically removed by the fuzzy morphological component analysis. From the comparison of simulation assessment indexes, the fuzzy morphological component analysis algorithm has the highest signal-to-noise ratio, the smallest mean square error and the largest similarity coefficient. Therefore, the fuzzy morphological component analysis algorithm shows a unique advantage in the de-noising of the output displacement signal for the giant magnetostrictive actuator.
In order to remove or suppress the noise in the output displacement signal of the giant magnetostrictive actuator, the output displacement signal was processed and denoised based on the morphological component analysis theory. Because of the potential shortcomings of threshold processing in morphological component analysis algorithm, this paper proposes the fuzzy morphological component analysis algorithm by constructing fuzzy threshold function. Simulation and experimental results show that, from the comparison of the signals after de-noising, the noise of the output displacement signal is basically removed by the fuzzy morphological component analysis. From the comparison of simulation assessment indexes, the fuzzy morphological component analysis algorithm has the highest signal-to-noise ratio, the smallest mean square error and the largest similarity coefficient. Therefore, the fuzzy morphological component analysis algorithm shows a unique advantage in the de-noising of the output displacement signal for the giant magnetostrictive actuator.
2020, 39(2): 295-302.
doi: 10.13433/j.cnki.1003-8728.20190106
Abstract:
Aiming at the effect of the shape accuracy of the formed workpiece and the residual stresses induced by milling on the elastoplastic stress distribution in the press bending process of the workpiece, a simulation method for press bending considering residual stresses in milling was proposed. Firstly, the analytical formulas of the bending stress were derived. Then, the finite element model for the bending considering the induced residual stress in milling was established. The influences of the residual stresses caused by milling operation on the press bending were investigated, and the analytical formula of the bending stress considering the residual stress in milling was established via numerical method. Results indicate that the present finite element model can be used to study the change in the stress-strain distribution in bending. The residual stress generated by low speed milling has the greatest influence on the stress distribution before unloading and the tangential strain on the upper and lower surfaces after unloading. The residual stresses induced by the high-speed milling minimize the bending angle and maximize the deformation of the specimen after unloading.
Aiming at the effect of the shape accuracy of the formed workpiece and the residual stresses induced by milling on the elastoplastic stress distribution in the press bending process of the workpiece, a simulation method for press bending considering residual stresses in milling was proposed. Firstly, the analytical formulas of the bending stress were derived. Then, the finite element model for the bending considering the induced residual stress in milling was established. The influences of the residual stresses caused by milling operation on the press bending were investigated, and the analytical formula of the bending stress considering the residual stress in milling was established via numerical method. Results indicate that the present finite element model can be used to study the change in the stress-strain distribution in bending. The residual stress generated by low speed milling has the greatest influence on the stress distribution before unloading and the tangential strain on the upper and lower surfaces after unloading. The residual stresses induced by the high-speed milling minimize the bending angle and maximize the deformation of the specimen after unloading.
2020, 39(2): 303-308.
doi: 10.13433/j.cnki.1003-8728.20190096
Abstract:
The aerodynamic performance of coaxial twin-rotors in either hover or level flight is simulated. The numerical method using multiple reference frame method is firstly applied in a benchmark rotor and wind tunnel model in hover and level flight, respectively. The simulated thrust coefficients agree with the results from experiment. Then the CFD (computational fluid dynamics) model is established for coaxial twin-rotors, and the aerodynamic performance of upper and lower rotors are analyzed. Numerical results show that the single rotor generates higher thrust coefficient than either the upper or the lower rotor of the coaxial twin-rotor in hover. The thrust ratio between the coaxial twin-rotor and the single rotor reaches 1.844 in present simulation. The thrust ratio decreases with the increase of the rotating speed. In level flight, to avoid the windmill effect, the coaxial twin-rotor is better than the single rotor, and a small space between upper and lower rotors is preferred.
The aerodynamic performance of coaxial twin-rotors in either hover or level flight is simulated. The numerical method using multiple reference frame method is firstly applied in a benchmark rotor and wind tunnel model in hover and level flight, respectively. The simulated thrust coefficients agree with the results from experiment. Then the CFD (computational fluid dynamics) model is established for coaxial twin-rotors, and the aerodynamic performance of upper and lower rotors are analyzed. Numerical results show that the single rotor generates higher thrust coefficient than either the upper or the lower rotor of the coaxial twin-rotor in hover. The thrust ratio between the coaxial twin-rotor and the single rotor reaches 1.844 in present simulation. The thrust ratio decreases with the increase of the rotating speed. In level flight, to avoid the windmill effect, the coaxial twin-rotor is better than the single rotor, and a small space between upper and lower rotors is preferred.
2020, 39(2): 309-314.
doi: 10.13433/j.cnki.1003-8728.20190128
Abstract:
An important challenge in structural reliability is to reduce the number of calls to the performance function. The failure has the characteristics of small probability and multiple responses in the engineering practice; the complex finite element modeling is indispensable. Therefore, it is particularly important to reduce the number of calls to the performance function. To construct the accurate surrogate model for the performance functions of the multi-response system, active learning is used to improve the accuracy, and the Latin Hypercube Sampling (LHS) is used to enhance the sampling efficiency. The Generalized Subset Simulation (GSS) is employed to enhance the computational efficiency of the GSS in the multiple-response system. An active learning reliability method based on the Kriging model and GSS is proposed to solve the small failure probability problem and reduce the number of calls to the performance function. The numerical simulation results show that the new method can effectively analyze the structural reliability of the multi-response system.
An important challenge in structural reliability is to reduce the number of calls to the performance function. The failure has the characteristics of small probability and multiple responses in the engineering practice; the complex finite element modeling is indispensable. Therefore, it is particularly important to reduce the number of calls to the performance function. To construct the accurate surrogate model for the performance functions of the multi-response system, active learning is used to improve the accuracy, and the Latin Hypercube Sampling (LHS) is used to enhance the sampling efficiency. The Generalized Subset Simulation (GSS) is employed to enhance the computational efficiency of the GSS in the multiple-response system. An active learning reliability method based on the Kriging model and GSS is proposed to solve the small failure probability problem and reduce the number of calls to the performance function. The numerical simulation results show that the new method can effectively analyze the structural reliability of the multi-response system.
2020, 39(2): 315-320.
doi: 10.13433/j.cnki.1003-8728.20190100
Abstract:
The similarity study of three-dimensional models using skeleton diagrams has important applications in engineering, which can effectively solve problems such as retrieval and reuse. In this study, a simple skeleton diagram is used to describe the main normal direction monotonous free-form surface (any line along the main normal direction of the surface has at most one intersection with the surface). First, the total normal vector of the free surface is obtained. The free surface is projected onto the two-dimensional plane in the opposite direction of the total normal vector to obtain the projected surface. Then, the skeleton point and skeleton line of the projected surface is obtained. Finally, the skeleton line of the projected surface is stretched cylindrically in the direction of the total normal vector of the free surface and intersected with the free surface. The intersection line is a simple skeleton diagram of the free surface. The algorithm is compared with MATLAB's skeletal algorithm. Experiments show that the simple skeleton diagram obtained in this paper can better describe the geometric and topological features of the mononormal free-form surface in the main normal direction, which provides a theoretical and technical basis for the similarity of free-form surfaces.
The similarity study of three-dimensional models using skeleton diagrams has important applications in engineering, which can effectively solve problems such as retrieval and reuse. In this study, a simple skeleton diagram is used to describe the main normal direction monotonous free-form surface (any line along the main normal direction of the surface has at most one intersection with the surface). First, the total normal vector of the free surface is obtained. The free surface is projected onto the two-dimensional plane in the opposite direction of the total normal vector to obtain the projected surface. Then, the skeleton point and skeleton line of the projected surface is obtained. Finally, the skeleton line of the projected surface is stretched cylindrically in the direction of the total normal vector of the free surface and intersected with the free surface. The intersection line is a simple skeleton diagram of the free surface. The algorithm is compared with MATLAB's skeletal algorithm. Experiments show that the simple skeleton diagram obtained in this paper can better describe the geometric and topological features of the mononormal free-form surface in the main normal direction, which provides a theoretical and technical basis for the similarity of free-form surfaces.
2020, 39(2): 321-328.
doi: 10.13433/j.cnki.1003-8728.20190286
Abstract:
In order to meet the development needs of the throttle control system, a new type of Fly-by-Wire (FBW) Throttle Console Quadrant (TCQ) is proposed to conforming to ergonomics. Firstly, the translational design scheme, based on link & gear transmission, is adopted for the reason that it is easily to change between different movement forms. Secondly, the optimization design for TCQ's transmission mechanism is achieved based on the theory of minimum deviation; the basic dimensions of TCQ's are obtained via MATLAB's fmincon function. Thirdly, the system's accuracy is analyzed by using total differentiation and the effective length theory. The analysis results are obtained as follows: the maximum transmission errors are appeared when the lever is at the STOP position; the link 3 has more influence to transmission accuracy than link 2, and their influence trends are opposite; the influence for the transmission accuracy which is brought by kinematic pair clearance can be reduced by connecting bearing inner ring and link 3 at the movable point. Finally, according to prototype test and its verification results, it indicates that the test results are consistent with design; the design scheme is correct and workable.
In order to meet the development needs of the throttle control system, a new type of Fly-by-Wire (FBW) Throttle Console Quadrant (TCQ) is proposed to conforming to ergonomics. Firstly, the translational design scheme, based on link & gear transmission, is adopted for the reason that it is easily to change between different movement forms. Secondly, the optimization design for TCQ's transmission mechanism is achieved based on the theory of minimum deviation; the basic dimensions of TCQ's are obtained via MATLAB's fmincon function. Thirdly, the system's accuracy is analyzed by using total differentiation and the effective length theory. The analysis results are obtained as follows: the maximum transmission errors are appeared when the lever is at the STOP position; the link 3 has more influence to transmission accuracy than link 2, and their influence trends are opposite; the influence for the transmission accuracy which is brought by kinematic pair clearance can be reduced by connecting bearing inner ring and link 3 at the movable point. Finally, according to prototype test and its verification results, it indicates that the test results are consistent with design; the design scheme is correct and workable.
