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RSS2021 Vol. 40, No. 1
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2021, 40(1): 1-8.
doi: 10.13433/j.cnki.1003-8728.20200017
PDF 3244KB
Abstract:
Based on Reynolds equation, a theoretical lubrication model of surface textured sliding bearings is established, and the effects of different texture parameters (distribution angle, depth, area ratio, deflection angle, length) on bearing capacity and friction coefficient of bit sliding bearings are investigated. Arrangement of texture near the convergence of oil film and the minimum oil film thickness is beneficial to increase the lubrication performance of the bearing surface, while arrangement of texture at the divergence of oil film will reduce the bearing capacity and increase the friction coefficient. The optimum texture depth is related to the working conditions of the bearing. Under different eccentricity conditions, the greater the load the bearing bears, the deeper the optimum texture depth of the grooved textured bearing. The friction coefficient increases first and then decreases with the increase of texture area ratio, and the friction coefficient is the smallest when the area ratio is 18%. The effect of texture depth on texture deflection angle is small, and the friction coefficient of bearing decreases with the increase of deflection angle. When the texture length is 1/2 of the width of bearing, the lubrication effect of bearing is the best.
Based on Reynolds equation, a theoretical lubrication model of surface textured sliding bearings is established, and the effects of different texture parameters (distribution angle, depth, area ratio, deflection angle, length) on bearing capacity and friction coefficient of bit sliding bearings are investigated. Arrangement of texture near the convergence of oil film and the minimum oil film thickness is beneficial to increase the lubrication performance of the bearing surface, while arrangement of texture at the divergence of oil film will reduce the bearing capacity and increase the friction coefficient. The optimum texture depth is related to the working conditions of the bearing. Under different eccentricity conditions, the greater the load the bearing bears, the deeper the optimum texture depth of the grooved textured bearing. The friction coefficient increases first and then decreases with the increase of texture area ratio, and the friction coefficient is the smallest when the area ratio is 18%. The effect of texture depth on texture deflection angle is small, and the friction coefficient of bearing decreases with the increase of deflection angle. When the texture length is 1/2 of the width of bearing, the lubrication effect of bearing is the best.
2021, 40(1): 9-15.
doi: 10.13433/j.cnki.1003-8728.20200097
Abstract:
The fretting fatigue test of ZL702A aluminum alloy shows that the crack nucleates at the contact trailing edge, and it is closed under tensile stress and open under compressive stress. The finite element method is used to analyze the special opening and closing mechanism. Firstly, the concept of cumulative dissipation energy is used to determine the location of crack initiation. In the simulation of crack propagation path with Smith-watson-topper (SWT) parameter method and Max Tangential Stress (MTS) criterion method, MTS criterion can accurately simulate the crack pattern path comparing with the experiment. Secondly, when MTS criterion is used to simulate crack growth, the normal stress and tangential stress on the crack surface are measured, and the special crack opening is obtained. The closing phenomenon is caused by the deformation of one side of the crack surface caused by fretting contact. Finally, the ratio of crack opening dependency (RCOD) and the effective stress intensity factor are introduced to modify Paris formula, and the fretting fatigue life equation with crack opening and closing phenomenon is obtained. By comparison, it is found that the prediction value of fatigue life without considering crack opening and closing is significantly higher than the test value, while the fatigue life with considering crack opening and closing is significantly higher than the test value. The life prediction value is in a good agreement with the test value.
The fretting fatigue test of ZL702A aluminum alloy shows that the crack nucleates at the contact trailing edge, and it is closed under tensile stress and open under compressive stress. The finite element method is used to analyze the special opening and closing mechanism. Firstly, the concept of cumulative dissipation energy is used to determine the location of crack initiation. In the simulation of crack propagation path with Smith-watson-topper (SWT) parameter method and Max Tangential Stress (MTS) criterion method, MTS criterion can accurately simulate the crack pattern path comparing with the experiment. Secondly, when MTS criterion is used to simulate crack growth, the normal stress and tangential stress on the crack surface are measured, and the special crack opening is obtained. The closing phenomenon is caused by the deformation of one side of the crack surface caused by fretting contact. Finally, the ratio of crack opening dependency (RCOD) and the effective stress intensity factor are introduced to modify Paris formula, and the fretting fatigue life equation with crack opening and closing phenomenon is obtained. By comparison, it is found that the prediction value of fatigue life without considering crack opening and closing is significantly higher than the test value, while the fatigue life with considering crack opening and closing is significantly higher than the test value. The life prediction value is in a good agreement with the test value.
2021, 40(1): 16-21.
doi: 10.13433/j.cnki.1003-8728.20200261
Abstract:
Under shock loading with variable amplitude and frequency, the viscoelastic damping structure is always in the multifactorial dynamic state, and its shock response is obviously different from that at the low strain rate. Based on the periodic mechanical response for SR at high strain rates and the fractional order α of the fractional Maxwell model reflecting the elasticity-viscosity distribution, a distributed-order Maxwell constitutive model is constructed to accurately simulate the shock response of vibration isolation SR. To verify the proposed model, the shock experiments for different high strain rates are performed by SHPB system. The results indicate that experimental stress-strain curves could be divided into four stages: the linear stage, strain-softening stage, strain-hardening stage and failure stage. With increase of the strain rate, the yield strain, the yield stress, the secant modulus and the curvature in strain-softening stage all increase, and the hardening effect in the strain-hardening stage tends to stronger, which should embody the rate-dependent properties of SR. Besides, the representational ability of the proposed model on experimental data is further analyzed. The RMSE values at different strain rates are all small. For all these reasons, the distributed-order Maxwell constitutive model could accurately describe the shock response of vibration isolation SR in a wider range of strain rates with the advantages of higher fitting precision, and clear physical meaning.
Under shock loading with variable amplitude and frequency, the viscoelastic damping structure is always in the multifactorial dynamic state, and its shock response is obviously different from that at the low strain rate. Based on the periodic mechanical response for SR at high strain rates and the fractional order α of the fractional Maxwell model reflecting the elasticity-viscosity distribution, a distributed-order Maxwell constitutive model is constructed to accurately simulate the shock response of vibration isolation SR. To verify the proposed model, the shock experiments for different high strain rates are performed by SHPB system. The results indicate that experimental stress-strain curves could be divided into four stages: the linear stage, strain-softening stage, strain-hardening stage and failure stage. With increase of the strain rate, the yield strain, the yield stress, the secant modulus and the curvature in strain-softening stage all increase, and the hardening effect in the strain-hardening stage tends to stronger, which should embody the rate-dependent properties of SR. Besides, the representational ability of the proposed model on experimental data is further analyzed. The RMSE values at different strain rates are all small. For all these reasons, the distributed-order Maxwell constitutive model could accurately describe the shock response of vibration isolation SR in a wider range of strain rates with the advantages of higher fitting precision, and clear physical meaning.
2021, 40(1): 22-32.
doi: 10.13433/j.cnki.1003-8728.20190335
Abstract:
In order to effectively extract the fault characteristics of the vibration signal of rolling bearing, a fault diagnosis method based on piecewise cubic Hermite interpolation-local characteristic-scale decomposition (PCHIP-LCD) is proposed. PCHIP method is adopted to replace cubic spline interpolation (CSI) in LCD, proposing improved LCD method to complete x(t) decomposition of vibration signal, and to obtain several intrinsic scale components (ISCs). an effective ISCs component screening rule based on the combination weight index of kurtosis and correlation co efficient (K-C) was established to achieve the selection and reconstruction of ISCs components, then obtain the reconstruction signal xnew(t). Teager energy operator (TEO) demodulation analysis was carried out on reconstructed signal xnew(t), TEO energy spectrum is obtained to extract the fault characteristics of rolling bearings. The results show that this method can enhance the enveloping fitting ability of signals.
In order to effectively extract the fault characteristics of the vibration signal of rolling bearing, a fault diagnosis method based on piecewise cubic Hermite interpolation-local characteristic-scale decomposition (PCHIP-LCD) is proposed. PCHIP method is adopted to replace cubic spline interpolation (CSI) in LCD, proposing improved LCD method to complete x(t) decomposition of vibration signal, and to obtain several intrinsic scale components (ISCs). an effective ISCs component screening rule based on the combination weight index of kurtosis and correlation co efficient (K-C) was established to achieve the selection and reconstruction of ISCs components, then obtain the reconstruction signal xnew(t). Teager energy operator (TEO) demodulation analysis was carried out on reconstructed signal xnew(t), TEO energy spectrum is obtained to extract the fault characteristics of rolling bearings. The results show that this method can enhance the enveloping fitting ability of signals.
2021, 40(1): 33-39.
doi: 10.13433/j.cnki.1003-8728.20190344
Abstract:
The drive structure of the existing soft robots is mostly fiber-reinforced and multi-cavity types. For the soft actuators, a novel soft actuator is developed. Firstly, the design idea of the novel soft actuator structure is introduced. In order to further study the rationality of the structure, the analysis of the bending characteristics of the soft actuator via Yeoh model is carried out, and the relationship model between the radius of curvature and the inflation pressure is obtained, and the soft actuator is used. The construction of the production and experimental platform validates the model and proves the correctness of the structural model.
The drive structure of the existing soft robots is mostly fiber-reinforced and multi-cavity types. For the soft actuators, a novel soft actuator is developed. Firstly, the design idea of the novel soft actuator structure is introduced. In order to further study the rationality of the structure, the analysis of the bending characteristics of the soft actuator via Yeoh model is carried out, and the relationship model between the radius of curvature and the inflation pressure is obtained, and the soft actuator is used. The construction of the production and experimental platform validates the model and proves the correctness of the structural model.
2021, 40(1): 40-46.
doi: 10.13433/j.cnki.1003-8728.20200022
Abstract:
Based on the analysis and division of the position and orientation errors among the pairing connector of reconfigurable robots, a special pair of the connector is designed for online measurement and identification of the assembly errors among the assembled modules. The relation model between the errors of position and orientation in the pairing connector and deviations of the geometric structure in adjoining modules is established. Furthermore, the mapping relation model among the measuring values of the internal range sensors and the errors of the position and orientation in the pairing connector is also established. An online identification and compensation method for the assembly errors among the consecutive modules is presented, based on the displacement of the internal range sensors. In order to verify the correctness of the present method, a single joint-link test platform is developed. After the assembly errors are identified and compensated online, the test results show that the average position errors of the end-link are reduced by above 7 times.
Based on the analysis and division of the position and orientation errors among the pairing connector of reconfigurable robots, a special pair of the connector is designed for online measurement and identification of the assembly errors among the assembled modules. The relation model between the errors of position and orientation in the pairing connector and deviations of the geometric structure in adjoining modules is established. Furthermore, the mapping relation model among the measuring values of the internal range sensors and the errors of the position and orientation in the pairing connector is also established. An online identification and compensation method for the assembly errors among the consecutive modules is presented, based on the displacement of the internal range sensors. In order to verify the correctness of the present method, a single joint-link test platform is developed. After the assembly errors are identified and compensated online, the test results show that the average position errors of the end-link are reduced by above 7 times.
2021, 40(1): 47-54.
doi: 10.13433/j.cnki.1003-8728.20200020
Abstract:
Aiming to reveal the influence rules of the parts′ masses of five-axis machining center on the whole machine performance, the dynamic model for the five axis machine center was established by combining the centralized parameter method and the substructure, According to the characteristics of topological structure of five-axis machining center, and the idea of substructure synthesis, it is divided into two sub-chains. Furthermore, the influence law is carried out. After analyzing the relations of each part′ mass of the sub-chain assembly, the evaluation index of machine tool inertia matching-mass ratio is proposed. Based on the optimization result of the inertia matching of tool-chain and part-chain, the mass optimization scheme of the whole machine is obtained. The optimization result is verified by the finite element simulation software. The results show that the mass of the whole machine is reduced by 10.3% and the first-order natural frequency is increased by 3.9%.
Aiming to reveal the influence rules of the parts′ masses of five-axis machining center on the whole machine performance, the dynamic model for the five axis machine center was established by combining the centralized parameter method and the substructure, According to the characteristics of topological structure of five-axis machining center, and the idea of substructure synthesis, it is divided into two sub-chains. Furthermore, the influence law is carried out. After analyzing the relations of each part′ mass of the sub-chain assembly, the evaluation index of machine tool inertia matching-mass ratio is proposed. Based on the optimization result of the inertia matching of tool-chain and part-chain, the mass optimization scheme of the whole machine is obtained. The optimization result is verified by the finite element simulation software. The results show that the mass of the whole machine is reduced by 10.3% and the first-order natural frequency is increased by 3.9%.
2021, 40(1): 55-62.
doi: 10.13433/j.cnki.1003-8728.20200016
Abstract:
In order to reveal the bounce dynamics and influencing factors of the contactor system, the segmental vibration differential equations of the contact and core bounce are proposed from the vibration view, and its numerical solution is obtained. Based on ADAMS and ANSYS software, the 3D dynamic simulation model of AC contactor is established. The simulation model and numerical solution are verified by experiments. The experimental results show that the numerical solution can accurately reflect the whole process of contact and core bounce. Secondly, the influence of the arc-shaped contact and the contact spring parameters with different curvature radius on the bounce of the contact is analyzed. At the same time, the dynamic and static contacts are respectively arc-arc, arc-plane, and plane-plane. The three matching cases of the planar shape are analyzed and compared. The results show that when the contact curvature is 0.625, the contact bounce time is the shortest. The combination of the circular arc shape and the planar contact can greatly reduce the contact bounce time.
In order to reveal the bounce dynamics and influencing factors of the contactor system, the segmental vibration differential equations of the contact and core bounce are proposed from the vibration view, and its numerical solution is obtained. Based on ADAMS and ANSYS software, the 3D dynamic simulation model of AC contactor is established. The simulation model and numerical solution are verified by experiments. The experimental results show that the numerical solution can accurately reflect the whole process of contact and core bounce. Secondly, the influence of the arc-shaped contact and the contact spring parameters with different curvature radius on the bounce of the contact is analyzed. At the same time, the dynamic and static contacts are respectively arc-arc, arc-plane, and plane-plane. The three matching cases of the planar shape are analyzed and compared. The results show that when the contact curvature is 0.625, the contact bounce time is the shortest. The combination of the circular arc shape and the planar contact can greatly reduce the contact bounce time.
2021, 40(1): 63-68.
doi: 10.13433/j.cnki.1003-8728.20200015
Abstract:
In order to explore a new way to improve the comprehensive performance of machine tools, a new configuration of foam aluminum sandwich structural column is proposed. Firstly, the XK714 CNC machine tool column is selected as the prototype, and the foam aluminum sandwich structure machine tool column is preliminarily designed with the equal rigidity design theory and the light weight design theory. Then, the multi-objective optimization design method is used to optimize the design of foam aluminum sandwich structure machine tool columns. Finally, the static, dynamic, thermal and light properties of the prototype column and the foam aluminum sandwich structure column before and after optimization are compared and analyzed. The results show that the foam aluminum sandwich structure machine tool column is effective for improving the static, dynamic, thermal and lightweight performance of the machine tool column and even the whole machine.
In order to explore a new way to improve the comprehensive performance of machine tools, a new configuration of foam aluminum sandwich structural column is proposed. Firstly, the XK714 CNC machine tool column is selected as the prototype, and the foam aluminum sandwich structure machine tool column is preliminarily designed with the equal rigidity design theory and the light weight design theory. Then, the multi-objective optimization design method is used to optimize the design of foam aluminum sandwich structure machine tool columns. Finally, the static, dynamic, thermal and light properties of the prototype column and the foam aluminum sandwich structure column before and after optimization are compared and analyzed. The results show that the foam aluminum sandwich structure machine tool column is effective for improving the static, dynamic, thermal and lightweight performance of the machine tool column and even the whole machine.
2021, 40(1): 69-75.
doi: 10.13433/j.cnki.1003-8728.20200019
Abstract:
In order to solve the problem of gap between magnetic poles or other insulating materials caused by machining precision or assembly error in practical engineering, a new type of linear-rotary magnetic gear (LRMG) with polar gap was designed in this paper. The concept of pole pitch ratio (PPR) was proposed, and the effects of diameter or pole pitch on optimal PPR were investigated. Simulation results show that the peak thrust and peak torque decrease with PPR increasing. And it is found that when PPR is 0.3, the output thrust density and torque density have the largest value, specific thrust and specific torque are also maximum, which means it has the maximum pole utilization ratio. The optimal PPR is not affected by the variation of diameter and pole pitch.
In order to solve the problem of gap between magnetic poles or other insulating materials caused by machining precision or assembly error in practical engineering, a new type of linear-rotary magnetic gear (LRMG) with polar gap was designed in this paper. The concept of pole pitch ratio (PPR) was proposed, and the effects of diameter or pole pitch on optimal PPR were investigated. Simulation results show that the peak thrust and peak torque decrease with PPR increasing. And it is found that when PPR is 0.3, the output thrust density and torque density have the largest value, specific thrust and specific torque are also maximum, which means it has the maximum pole utilization ratio. The optimal PPR is not affected by the variation of diameter and pole pitch.
2021, 40(1): 76-83.
doi: 10.13433/j.cnki.1003-8728.20190330
Abstract:
Action is the basic motion unit of electromechanical products, to ensure the reliability of the whole machine system, the reliability of the basic action unit must be guaranteed. Based on fuzzy matter-element method, a new method for reliability analysis of electromechanical product minimum action unit was proposed. Firstly, according to the structural decomposition mentality of "function-motion-action", the basic meta-action unit can be obtained by structuring decomposition the whole machine function. Then, the fuzzy matter-element analysis method was used to obtain the similar meta-action unit; the failure data of meta-action was constructed based on the similar meta-action, and a three-parameter Weibull distribution model was used to model the failure data. Finally, the failure data distribution of the meta-action unit was tested by Kolmogorov-Smirnov test method to judge whether the selected model was reasonable or not. The rotary cylinder piston moving meta-action of numerical control rotary table of some machining center was taken as an example to test reasonableness and effectiveness of the method. The results show that the failure data of meta-action obey the three-parameter Weibull distribution model, and the research of this paper is also the basis of the mapping between the reliability of the meta-action unit and the reliability of the whole machine.
Action is the basic motion unit of electromechanical products, to ensure the reliability of the whole machine system, the reliability of the basic action unit must be guaranteed. Based on fuzzy matter-element method, a new method for reliability analysis of electromechanical product minimum action unit was proposed. Firstly, according to the structural decomposition mentality of "function-motion-action", the basic meta-action unit can be obtained by structuring decomposition the whole machine function. Then, the fuzzy matter-element analysis method was used to obtain the similar meta-action unit; the failure data of meta-action was constructed based on the similar meta-action, and a three-parameter Weibull distribution model was used to model the failure data. Finally, the failure data distribution of the meta-action unit was tested by Kolmogorov-Smirnov test method to judge whether the selected model was reasonable or not. The rotary cylinder piston moving meta-action of numerical control rotary table of some machining center was taken as an example to test reasonableness and effectiveness of the method. The results show that the failure data of meta-action obey the three-parameter Weibull distribution model, and the research of this paper is also the basis of the mapping between the reliability of the meta-action unit and the reliability of the whole machine.
2021, 40(1): 84-91.
doi: 10.13433/j.cnki.1003-8728.20190332
Abstract:
The influence of frequency, amplitude, fixed height and fixed orientation of specimens on the surface machining quality of specimens was studied through one-dimensional vibration-type wall-sticking machining experiment, which further provided theoretical methods for inner surface machining of box shell parts. Based on the electrodynamic vibration test system, the 6061 aluminum alloy blocks were embedded in rubber gaskets at different heights and pasted on the inner wall of the self-made vibration container perpendicular and parallel to the vibration direction for processing experiments. When the specimen is fixed perpendicular to the vibration direction, with the same fixed height, the higher the frequency (amplitude), the faster the surface roughness value of the specimen will decline, and the better the processing effect will be. When the specimen is fixed parallel to the vibration direction, the same fixed height, the lower the frequency, the better the processing effect. Under a certain frequency and amplitude, two fixed position of the specimen surface roughness with the fixed height change law, but under different frequency amplitude, there are differences between the change rule. The results show that the vertical vibration direction is better than the parallel vibration direction under the same conditions. The fixed specimen perpendicular to the vibration direction is mainly affected by collision and extrusion of the grinding block, while the specimen parallel to the vibration direction is mainly affected by sliding and rubbing of the grinding block. In a certain range, the larger the frequency (amplitude), the more conducive to the processing of specimens.
The influence of frequency, amplitude, fixed height and fixed orientation of specimens on the surface machining quality of specimens was studied through one-dimensional vibration-type wall-sticking machining experiment, which further provided theoretical methods for inner surface machining of box shell parts. Based on the electrodynamic vibration test system, the 6061 aluminum alloy blocks were embedded in rubber gaskets at different heights and pasted on the inner wall of the self-made vibration container perpendicular and parallel to the vibration direction for processing experiments. When the specimen is fixed perpendicular to the vibration direction, with the same fixed height, the higher the frequency (amplitude), the faster the surface roughness value of the specimen will decline, and the better the processing effect will be. When the specimen is fixed parallel to the vibration direction, the same fixed height, the lower the frequency, the better the processing effect. Under a certain frequency and amplitude, two fixed position of the specimen surface roughness with the fixed height change law, but under different frequency amplitude, there are differences between the change rule. The results show that the vertical vibration direction is better than the parallel vibration direction under the same conditions. The fixed specimen perpendicular to the vibration direction is mainly affected by collision and extrusion of the grinding block, while the specimen parallel to the vibration direction is mainly affected by sliding and rubbing of the grinding block. In a certain range, the larger the frequency (amplitude), the more conducive to the processing of specimens.
2021, 40(1): 92-100.
doi: 10.13433/j.cnki.1003-8728.20200293
Abstract:
In order to make tourism cultural creative products better carry cultural imagery, it has to use computer-aided technology to optimize and evaluate the design plan, match the relationship between color and multicultural imagery, improve design efficiency. By combining grey relational analysis and approaching ideal solutions, using trapezoidal fuzzy numbers to describe users′ cultural image preferences for cultural elements in the color scheme of tourism cultural creative products, this paper proposes a tourism cultural creativity based on grey relational analysis-approximate ideal solution sorting method Evaluation method of product color design scheme.
In order to make tourism cultural creative products better carry cultural imagery, it has to use computer-aided technology to optimize and evaluate the design plan, match the relationship between color and multicultural imagery, improve design efficiency. By combining grey relational analysis and approaching ideal solutions, using trapezoidal fuzzy numbers to describe users′ cultural image preferences for cultural elements in the color scheme of tourism cultural creative products, this paper proposes a tourism cultural creativity based on grey relational analysis-approximate ideal solution sorting method Evaluation method of product color design scheme.
2021, 40(1): 101-108.
doi: 10.13433/j.cnki.1003-8728.20200021
Abstract:
In order to reveal the shrinkage mechanism of the cylindrical parts in the fused deposition modeling (FDM), the finite element model for the building process of the cylindrical part was established. Based on the "birth-death element technology", the command flow of temperature field and stress field was programmed, and the coupling thermo-mechanical numerical simulation in the building process of the cylindrical parts was carried out. The simulation results show that the radial temperature gradient distribution of the cylindrical parts is very uneven and the equivalent stress is high; while the axial temperature gradient distribution is relatively uniform, and the equivalent stress is lower than the radial one. The difference between the radial and the axial temperature gradients results in large radial shrinkage and small axial deformation in the cylindrical parts.
In order to reveal the shrinkage mechanism of the cylindrical parts in the fused deposition modeling (FDM), the finite element model for the building process of the cylindrical part was established. Based on the "birth-death element technology", the command flow of temperature field and stress field was programmed, and the coupling thermo-mechanical numerical simulation in the building process of the cylindrical parts was carried out. The simulation results show that the radial temperature gradient distribution of the cylindrical parts is very uneven and the equivalent stress is high; while the axial temperature gradient distribution is relatively uniform, and the equivalent stress is lower than the radial one. The difference between the radial and the axial temperature gradients results in large radial shrinkage and small axial deformation in the cylindrical parts.
2021, 40(1): 109-115.
doi: 10.13433/j.cnki.1003-8728.20200029
Abstract:
The flexible characteristics of flexible flexibility in the flexible workshop make the workshop scheduling problem under dynamic random disturbance more flexible and optimized. In this paper, the dynamic random events of the flexible workshop production system are used to quantitatively analyze and judge the degree of influence on the workshop. Based on the adjustment of the workshop scheduling, a rule-based strategy based on immunity is proposed to ensure the healthy execution of the actual production plan. Firstly, according to the degree of interference of the dynamic random interference environment to the workshop system, the concept of immunity is proposed, and the immunity value is used as the basis for the self-repair scheduling and scheduling adjustment of the system. In the scheduling adjustment, according to the current production state, the rule-oriented dynamic adjustment is carried out, and the scheduling mode is reasonably selected to improve the fit of the shop scheduling adjustment and the actual target demand of the workshop.
The flexible characteristics of flexible flexibility in the flexible workshop make the workshop scheduling problem under dynamic random disturbance more flexible and optimized. In this paper, the dynamic random events of the flexible workshop production system are used to quantitatively analyze and judge the degree of influence on the workshop. Based on the adjustment of the workshop scheduling, a rule-based strategy based on immunity is proposed to ensure the healthy execution of the actual production plan. Firstly, according to the degree of interference of the dynamic random interference environment to the workshop system, the concept of immunity is proposed, and the immunity value is used as the basis for the self-repair scheduling and scheduling adjustment of the system. In the scheduling adjustment, according to the current production state, the rule-oriented dynamic adjustment is carried out, and the scheduling mode is reasonably selected to improve the fit of the shop scheduling adjustment and the actual target demand of the workshop.
2021, 40(1): 116-124.
doi: 10.13433/j.cnki.1003-8728.20190331
Abstract:
The surface quality of transparent parts is an important indicator to measure whether they are qualified or not. Computer vision technology is widely used in the detection of surface defects of transparent parts because of its advantages such as high speed, high precision, low cost and good stability. This paper mainly introduces the detection of the surface defects of transparent parts with image acquisition, image processing and defect recognition. This paper uses the image feature method and the deep learning method to classify the surface defects of transparent parts and discusses the recent developments and existing problems of computer vision technology for detecting surface defects of transparent parts.
The surface quality of transparent parts is an important indicator to measure whether they are qualified or not. Computer vision technology is widely used in the detection of surface defects of transparent parts because of its advantages such as high speed, high precision, low cost and good stability. This paper mainly introduces the detection of the surface defects of transparent parts with image acquisition, image processing and defect recognition. This paper uses the image feature method and the deep learning method to classify the surface defects of transparent parts and discusses the recent developments and existing problems of computer vision technology for detecting surface defects of transparent parts.
2021, 40(1): 125-131.
doi: 10.13433/j.cnki.1003-8728.20200014
Abstract:
The key parameters of the motors ESP system play a vital role in the control effect of ESP, and these parameters are difficult to be obtained directly, so it is a feasible method to estimate them. In the CarSim step condition, the recursive least squares algorithm is used to identify the equivalent lateral deflection stiffness of front and rear axles at different angles and vehicle speeds, and the identified MAP was fitted. A 3-degree of freedom simplified vehicle model is established, in which the equivalent lateral stiffness of the front and rear axles changes with the angle of rotation and the speed of the vehicle. The improved Sage-Husa noise estimator was combined with unscented Kalman filter to estimate sideslip angle, yaw rate, longitudinal speed and transverse speed of the vehicle running state parameters. The estimated results were in good agreement with the simulation results of CarSim software. Taking the estimated vehicle driving state parameters as input, the adaptive traceless Kalman filter is used to estimate the adhesion coefficients of high-adhesion road surface, low-adhesion road surface and split road surface. The estimated results are in good agreement with the CarSim road adhesion coefficient setting values.
The key parameters of the motors ESP system play a vital role in the control effect of ESP, and these parameters are difficult to be obtained directly, so it is a feasible method to estimate them. In the CarSim step condition, the recursive least squares algorithm is used to identify the equivalent lateral deflection stiffness of front and rear axles at different angles and vehicle speeds, and the identified MAP was fitted. A 3-degree of freedom simplified vehicle model is established, in which the equivalent lateral stiffness of the front and rear axles changes with the angle of rotation and the speed of the vehicle. The improved Sage-Husa noise estimator was combined with unscented Kalman filter to estimate sideslip angle, yaw rate, longitudinal speed and transverse speed of the vehicle running state parameters. The estimated results were in good agreement with the simulation results of CarSim software. Taking the estimated vehicle driving state parameters as input, the adaptive traceless Kalman filter is used to estimate the adhesion coefficients of high-adhesion road surface, low-adhesion road surface and split road surface. The estimated results are in good agreement with the CarSim road adhesion coefficient setting values.
2021, 40(1): 132-138.
doi: 10.13433/j.cnki.1003-8728.20200013
Abstract:
The conventional hydraulic braking system generally adopts the PWM (Pulse width modulation) control technology to regulate the wheel cylinder pressure. It controls the increase and decrease of the pressure according to the correspondence between duty ratio and wheel cylinder pressure variation. However, by studying the PWM dynamics characteristics of a solenoid valve, it was found that the effective duty ratio range was small when the pressure of the braking system is reduced and that it is difficult to achieve precise pressure and high efficiency regulation. Therefore, a segmentation control method was proposed in this paper, based on the look-up table method and the stepped decompression control. The wheel cylinder pressure estimation algorithm was applied to the pressure control; the wheel cylinder′s estimated pressure was used as feedback of the pressure closed-loop control system. With the Simulink/AMEsim co-simulation platform, the computer simulation was carried out to verify the pressure estimation algorithm and the pressure control algorithm. The accuracy of the estimation algorithm and the feasibility and superiority of the pressure control algorithm were proved.
The conventional hydraulic braking system generally adopts the PWM (Pulse width modulation) control technology to regulate the wheel cylinder pressure. It controls the increase and decrease of the pressure according to the correspondence between duty ratio and wheel cylinder pressure variation. However, by studying the PWM dynamics characteristics of a solenoid valve, it was found that the effective duty ratio range was small when the pressure of the braking system is reduced and that it is difficult to achieve precise pressure and high efficiency regulation. Therefore, a segmentation control method was proposed in this paper, based on the look-up table method and the stepped decompression control. The wheel cylinder pressure estimation algorithm was applied to the pressure control; the wheel cylinder′s estimated pressure was used as feedback of the pressure closed-loop control system. With the Simulink/AMEsim co-simulation platform, the computer simulation was carried out to verify the pressure estimation algorithm and the pressure control algorithm. The accuracy of the estimation algorithm and the feasibility and superiority of the pressure control algorithm were proved.
2021, 40(1): 139-145.
doi: 10.13433/j.cnki.1003-8728.20200012
Abstract:
The motion equations of the MacPherson steering suspension mechanism were established with the rigid body screw motion theory, which can describe more accurately the actual motion state of the MacPherson suspension mechanism. The formulae of camber and toe-in angles of the wheel, whose initial values were taken into consideration, and those of two pressure angles in the steering trapezoid were deduced. The difference between toe-in and steering angles of the wheel was discussed. The optimization model of the suspension mechanism was established by minimizing steering errors and restricting the four alignment parameters and two transmission pressure angles within their maximum and minimum boundaries when the wheel is jouncing, rebounding or during vehicle steering. An actual MacPherson-type steering suspension mechanism was optimized under its given conditions; the results show that the varying range of the toe-in angle is narrower than the original range when the wheel is jouncing, meaning that the suspension mechanism has a more stable kinematics performance, thus improving significantly the steering performance of the suspension mechanism under the conditions that the two pressure angles and the required minimum turning radius of the vehicle are satisfied during steering.
The motion equations of the MacPherson steering suspension mechanism were established with the rigid body screw motion theory, which can describe more accurately the actual motion state of the MacPherson suspension mechanism. The formulae of camber and toe-in angles of the wheel, whose initial values were taken into consideration, and those of two pressure angles in the steering trapezoid were deduced. The difference between toe-in and steering angles of the wheel was discussed. The optimization model of the suspension mechanism was established by minimizing steering errors and restricting the four alignment parameters and two transmission pressure angles within their maximum and minimum boundaries when the wheel is jouncing, rebounding or during vehicle steering. An actual MacPherson-type steering suspension mechanism was optimized under its given conditions; the results show that the varying range of the toe-in angle is narrower than the original range when the wheel is jouncing, meaning that the suspension mechanism has a more stable kinematics performance, thus improving significantly the steering performance of the suspension mechanism under the conditions that the two pressure angles and the required minimum turning radius of the vehicle are satisfied during steering.
2021, 40(1): 146-154.
doi: 10.13433/j.cnki.1003-8728.20190343
Abstract:
Honeycomb core layer was assumed as a uniform entity in terms of the sandwich equivalent theory, the wet stress in hygrothermal environment is equivalent to the thermal stress, and the constitutive equation of honeycomb sandwich material under hygrothermal environment was established, the improved Hashin criteria and Besant criterion were used as the failure criterion of honeycomb sandwich material, which was realized with VUMAT subroutine. The Cohesive element simulation panel and connection between the core layer to establish finite element model for honeycomb sandwich plates under hygrothermal environment, hygrothermal environment will affect the bending performance of the honeycomb sandwich materials. By removing debonding phenomena between the Cohesive zone model panel and the core layer, the effect of the debonding damage on the properties of materials is calculated, the effect of the debonding location the bending performance of the honeycomb sandwich materials between the edge debonding and the internal debonding is compared. The results show that the hygrothermal environment reduces the ultimate bearing capacity of the material, the debonding phenomenon accelerates the separation of the panel and the core layer, the debonding position affects the damage spreading property and reduce the bending strength of the material.
Honeycomb core layer was assumed as a uniform entity in terms of the sandwich equivalent theory, the wet stress in hygrothermal environment is equivalent to the thermal stress, and the constitutive equation of honeycomb sandwich material under hygrothermal environment was established, the improved Hashin criteria and Besant criterion were used as the failure criterion of honeycomb sandwich material, which was realized with VUMAT subroutine. The Cohesive element simulation panel and connection between the core layer to establish finite element model for honeycomb sandwich plates under hygrothermal environment, hygrothermal environment will affect the bending performance of the honeycomb sandwich materials. By removing debonding phenomena between the Cohesive zone model panel and the core layer, the effect of the debonding damage on the properties of materials is calculated, the effect of the debonding location the bending performance of the honeycomb sandwich materials between the edge debonding and the internal debonding is compared. The results show that the hygrothermal environment reduces the ultimate bearing capacity of the material, the debonding phenomenon accelerates the separation of the panel and the core layer, the debonding position affects the damage spreading property and reduce the bending strength of the material.
2021, 40(1): 155-164.
doi: 10.13433/j.cnki.1003-8728.20200255
Abstract:
In order to improve the global optimization ability of particle swarm optimization (PSO), enhance the performance of PSO in dealing with those complex, high-dimensional, multimodal optimization problems, and furthermore, promote the optimization effect in reliability optimization applications, a direct position updating-based trying-mutation PSO (DTPSO) is proposed in this paper. In this algorithm, the direct position updating strategy and trying mutation strategy are designed, which can effectively maintain the diversity of population, balance the exploitation and exploration, and increase the probability of obtaining the global optimal solution. After being verified and compared by 9 complex test functions, the rationality of DTPSO algorithm design and the excellent global optimization performances are proved. In the reliability optimization, the reliability redundancy allocation and reliability allocation are optimized by different advanced improved algorithms, and the comparison results prove the stability and optimization performance of DTPSO.
In order to improve the global optimization ability of particle swarm optimization (PSO), enhance the performance of PSO in dealing with those complex, high-dimensional, multimodal optimization problems, and furthermore, promote the optimization effect in reliability optimization applications, a direct position updating-based trying-mutation PSO (DTPSO) is proposed in this paper. In this algorithm, the direct position updating strategy and trying mutation strategy are designed, which can effectively maintain the diversity of population, balance the exploitation and exploration, and increase the probability of obtaining the global optimal solution. After being verified and compared by 9 complex test functions, the rationality of DTPSO algorithm design and the excellent global optimization performances are proved. In the reliability optimization, the reliability redundancy allocation and reliability allocation are optimized by different advanced improved algorithms, and the comparison results prove the stability and optimization performance of DTPSO.
