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RSS2021 Vol. 40, No. 11
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2021, 40(11): 1641-1648.
doi: 10.13433/j.cnki.1003-8728.20200263
PDF 2118KB
Abstract:
The high-speed machining of Ti-6Al-4V alloy is a complicated thermal coupling process with high temperature and high strain rate. In order to study the true stress-strain relationship of Ti-6Al-4V alloy at high temperature and high strain rate, a modified Johnson-cook (J-C) constitutive model was constructed. The modified J-C constitutive model considers that the strain hardening rate will decrease with the increasing of temperature in the plastic phase and that the flow stress of Ti-6Al-4V alloy will decrease sharply when the critical temperature of high temperature dynamic crystallization effect is reached. The predicted flow stress-strain results via modified J-C constitutive model are in a good agreement with the test data, and the error rate is within 8%, which accurately reflects the true stress-strain relationship of Ti-6Al-4V alloy at different loading temperatures.
The high-speed machining of Ti-6Al-4V alloy is a complicated thermal coupling process with high temperature and high strain rate. In order to study the true stress-strain relationship of Ti-6Al-4V alloy at high temperature and high strain rate, a modified Johnson-cook (J-C) constitutive model was constructed. The modified J-C constitutive model considers that the strain hardening rate will decrease with the increasing of temperature in the plastic phase and that the flow stress of Ti-6Al-4V alloy will decrease sharply when the critical temperature of high temperature dynamic crystallization effect is reached. The predicted flow stress-strain results via modified J-C constitutive model are in a good agreement with the test data, and the error rate is within 8%, which accurately reflects the true stress-strain relationship of Ti-6Al-4V alloy at different loading temperatures.
2021, 40(11): 1649-1656.
doi: 10.13433/j.cnki.1003-8728.20200256
Abstract:
Obtaining the response information of the structure by optimizing the arrangement of the incentive points, a new method is proposed, which takes the difference curvature function of acceleration signal as the damage index and directly applies the output signal to quickly judge the damage position of the structure. Firstly, the modal shape of the structure is calculated, and the minimum value of the non diagonal element of modal assurance criterion (MAC) matrix is taken as the fitness function, modified particle swarm optimization (MPSO) is used to optimize the number and location of excitation points, and then the average acceleration amplitude and root mean square (RMS) evaluation criteria are used to select the better scheme of excitation point arrangement. Then test the corresponding position of the excitation, obtain the acceleration signal, calculate the integral value of the square of the acceleration difference before and after the damage at the measuring point, use the curvature index function to determine the damage position, and the acceleration signal is filtered by Butterworth as the input sample of improved multi-scale sample entropy (MMSE). Finally, according to the change of MMSE mean value, the relative damage degree of the structure under each working condition is determined. The results show that the difference curvature function of acceleration signal of structural response is suitable for damage detection. By simulating the damage of bolt connection in three-dimensional truss vibration table, the damage diagnosis can be carried out under different damage conditions.
Obtaining the response information of the structure by optimizing the arrangement of the incentive points, a new method is proposed, which takes the difference curvature function of acceleration signal as the damage index and directly applies the output signal to quickly judge the damage position of the structure. Firstly, the modal shape of the structure is calculated, and the minimum value of the non diagonal element of modal assurance criterion (MAC) matrix is taken as the fitness function, modified particle swarm optimization (MPSO) is used to optimize the number and location of excitation points, and then the average acceleration amplitude and root mean square (RMS) evaluation criteria are used to select the better scheme of excitation point arrangement. Then test the corresponding position of the excitation, obtain the acceleration signal, calculate the integral value of the square of the acceleration difference before and after the damage at the measuring point, use the curvature index function to determine the damage position, and the acceleration signal is filtered by Butterworth as the input sample of improved multi-scale sample entropy (MMSE). Finally, according to the change of MMSE mean value, the relative damage degree of the structure under each working condition is determined. The results show that the difference curvature function of acceleration signal of structural response is suitable for damage detection. By simulating the damage of bolt connection in three-dimensional truss vibration table, the damage diagnosis can be carried out under different damage conditions.
2021, 40(11): 1657-1663.
doi: 10.13433/j.cnki.1003-8728.20200274
Abstract:
In this paper, a multi-modal piezoelectric energy harvesting device which based on rail vibration absorber was established. This device not only can reduce the track vibration effectively, and also harvest the vibration energy of rail vibration absorber. The effect of piezoelectric energy harvesting module on vibration absorption efficiency of the vibration absorber has been studied base on an elastic vibration model of the wheel-rail-absorber system. And the power generation capacity of piezoelectric energy harvesting module has been analyzed with the harmonic response method. The simulation results show that the energy harvesting module has little influence on the absorption efficiency of vibration absorber when it has been installed. Moreover, the multi-modal structure can broaden the frequency band of vibration energy harvesting effectively in the frequency range of 0 ~ 600 Hz, and increase the harvesting efficiency of vibration energy.
In this paper, a multi-modal piezoelectric energy harvesting device which based on rail vibration absorber was established. This device not only can reduce the track vibration effectively, and also harvest the vibration energy of rail vibration absorber. The effect of piezoelectric energy harvesting module on vibration absorption efficiency of the vibration absorber has been studied base on an elastic vibration model of the wheel-rail-absorber system. And the power generation capacity of piezoelectric energy harvesting module has been analyzed with the harmonic response method. The simulation results show that the energy harvesting module has little influence on the absorption efficiency of vibration absorber when it has been installed. Moreover, the multi-modal structure can broaden the frequency band of vibration energy harvesting effectively in the frequency range of 0 ~ 600 Hz, and increase the harvesting efficiency of vibration energy.
2021, 40(11): 1664-1669.
doi: 10.13433/j.cnki.1003-8728.20200541
Abstract:
Aiming at the problem that high no-load induced electromotive force harmonic content of tangential permanent magnet synchronous motor will increase stray loss, a method of optimizing stator slot parameters and rotor pole face eccentric design was proposed to improve the no-load induced electromotive force waveform. Expression of no-load harmonic induced electromotive force of tangential permanent magnet motor was deduced, and the key structural parameters affecting no-load induced electromotive force harmonics was analyzed, and the distortion rate of no-load induced electromotive force was determined as the optimized object to be reduced. The finite element method was used to analyze the three parameters of stator slot width, stator slot height and rotor pole face eccentricity to how affect the odd harmonics and waveform distortion rate of the no-load induced electromotive force of the motor, and then the optimal parameters was obtained. The simulation results show that the optimized motor can effectively weaken the no-load induced electromotive force harmonics, reduce the waveform distortion rate, increase the air gap magnetic density, reduce the cogging torque, and finally improve the overall performance of the motor.
Aiming at the problem that high no-load induced electromotive force harmonic content of tangential permanent magnet synchronous motor will increase stray loss, a method of optimizing stator slot parameters and rotor pole face eccentric design was proposed to improve the no-load induced electromotive force waveform. Expression of no-load harmonic induced electromotive force of tangential permanent magnet motor was deduced, and the key structural parameters affecting no-load induced electromotive force harmonics was analyzed, and the distortion rate of no-load induced electromotive force was determined as the optimized object to be reduced. The finite element method was used to analyze the three parameters of stator slot width, stator slot height and rotor pole face eccentricity to how affect the odd harmonics and waveform distortion rate of the no-load induced electromotive force of the motor, and then the optimal parameters was obtained. The simulation results show that the optimized motor can effectively weaken the no-load induced electromotive force harmonics, reduce the waveform distortion rate, increase the air gap magnetic density, reduce the cogging torque, and finally improve the overall performance of the motor.
2021, 40(11): 1670-1674.
doi: 10.13433/j.cnki.1003-8728.20200329
Abstract:
In order to determine the scope of influence of fluid excitation and shafting excitation on the centrifugal pump vibration, we calculated the unsteady flow field of a centrifugal pump and analyzed the vibration characteristics of this pump under fluid excitation and shafting excitation. We choose to use misalignment fault of rotor system as the shafting excitation in this paper. The numerical simulation results show that when the shafting is misaligned, the vibration response of the pump at 1APF (motor rotational frequency) is enhanced, a significant vibration response occurred at 2APF, and there is almost no change in the vibration level at 1BPF (blade passing frequency) and the middle-frequency. When the centrifugal pump is excited by fluid excitation and the misaligned excitation, the centrifugal pump has obvious vibration response at 1APF and 1BPF. The vibration level at 1BPF differs greatly from that at shafting excitation only.
In order to determine the scope of influence of fluid excitation and shafting excitation on the centrifugal pump vibration, we calculated the unsteady flow field of a centrifugal pump and analyzed the vibration characteristics of this pump under fluid excitation and shafting excitation. We choose to use misalignment fault of rotor system as the shafting excitation in this paper. The numerical simulation results show that when the shafting is misaligned, the vibration response of the pump at 1APF (motor rotational frequency) is enhanced, a significant vibration response occurred at 2APF, and there is almost no change in the vibration level at 1BPF (blade passing frequency) and the middle-frequency. When the centrifugal pump is excited by fluid excitation and the misaligned excitation, the centrifugal pump has obvious vibration response at 1APF and 1BPF. The vibration level at 1BPF differs greatly from that at shafting excitation only.
2021, 40(11): 1675-1680.
doi: 10.13433/j.cnki.1003-8728.20200279
Abstract:
Taking the visual robot loading and unloading system of the oil casing threading machine as the research object, the simulation model for the automatic loading and unloading system of the threading machine robot is established with UG and Robot Studio software. The Halcon image processing software is used to center the grasping workpiece, and developed the corresponding human-computer interaction interface. The robot's special loading and unloading fixture was designed, the system Smart dynamic components was created, and I/O signals to realize equipment communication was added. According to the actual production line unloading operation mode, the robot offline simulation program is written to complete the simulation and optimization of the robot flexible loading and unloading system. The simulation results show that the designed simulation system realizes the robot vision to accurately grasp the flexible loading and unloading of the workpiece.
Taking the visual robot loading and unloading system of the oil casing threading machine as the research object, the simulation model for the automatic loading and unloading system of the threading machine robot is established with UG and Robot Studio software. The Halcon image processing software is used to center the grasping workpiece, and developed the corresponding human-computer interaction interface. The robot's special loading and unloading fixture was designed, the system Smart dynamic components was created, and I/O signals to realize equipment communication was added. According to the actual production line unloading operation mode, the robot offline simulation program is written to complete the simulation and optimization of the robot flexible loading and unloading system. The simulation results show that the designed simulation system realizes the robot vision to accurately grasp the flexible loading and unloading of the workpiece.
2021, 40(11): 1681-1687.
doi: 10.13433/j.cnki.1003-8728.20200354
Abstract:
In order to improve the drawing accuracy of laser SLAM technology, this paper proposed an IRBPF-SLAM algorithm for intelligent resampling. The algorithm uses the bat heuristic adaptive resampling to resample small particles, generate new solutions, randomly select the best solution, update the number of bats, normalize the particles, update the optimal state of the robot, and finally reset the particles. The iteration times of the algorithm can be adjusted adaptively according to the degree of filter divergence. In addition, the distribution of laser sensors improved in the paper is integrated into the algorithm to obtain better distribution and mapping results. Simulation results show that the IRBPF-SLAM algorithm has better accuracy, calculation efficiency and filter consistency. In a large indoor space, the IRBPF-SLAM algorithm is integrated into the framework of ROS, and tested on the Ackerman mobile platform. The test results show that the new algorithm has more advantages than other algorithms.
In order to improve the drawing accuracy of laser SLAM technology, this paper proposed an IRBPF-SLAM algorithm for intelligent resampling. The algorithm uses the bat heuristic adaptive resampling to resample small particles, generate new solutions, randomly select the best solution, update the number of bats, normalize the particles, update the optimal state of the robot, and finally reset the particles. The iteration times of the algorithm can be adjusted adaptively according to the degree of filter divergence. In addition, the distribution of laser sensors improved in the paper is integrated into the algorithm to obtain better distribution and mapping results. Simulation results show that the IRBPF-SLAM algorithm has better accuracy, calculation efficiency and filter consistency. In a large indoor space, the IRBPF-SLAM algorithm is integrated into the framework of ROS, and tested on the Ackerman mobile platform. The test results show that the new algorithm has more advantages than other algorithms.
2021, 40(11): 1688-1694.
doi: 10.13433/j.cnki.1003-8728.20200351
Abstract:
Aiming at the problem that the mounting system of three cylinder engine can not meet the requirements of robust design considering some uncertain parameters, a method of mounting system optimization and stability analysis based on evidence theory is proposed in this paper. Considering the uncertainty of the parameters of the suspension system, based on the evidence theory and genetic algorithm, the parameters of the engine suspension system are optimized. Then, the probability cumulative distribution curve of the optimized parameters under the uncertainty condition is analyzed, and the result shows that the suspension system meets the stability design requirements. Finally, the optimized parameters are verified when there is fluctuation in the uncertain parameter range.
Aiming at the problem that the mounting system of three cylinder engine can not meet the requirements of robust design considering some uncertain parameters, a method of mounting system optimization and stability analysis based on evidence theory is proposed in this paper. Considering the uncertainty of the parameters of the suspension system, based on the evidence theory and genetic algorithm, the parameters of the engine suspension system are optimized. Then, the probability cumulative distribution curve of the optimized parameters under the uncertainty condition is analyzed, and the result shows that the suspension system meets the stability design requirements. Finally, the optimized parameters are verified when there is fluctuation in the uncertain parameter range.
2021, 40(11): 1695-1702.
doi: 10.13433/j.cnki.1003-8728.20200277
Abstract:
Ignoring the posture of the end motion platform of a plane flexible four-cable parallel robot may cause positioning errors. On the premise that the platform posture is considered, this paper sets up the robot’s kinematics model and carries out the static analysis of the end platform so as to optimize the minimum variance of the tension of each flexible cable. The paper proposes the tension homogenization optimization algorithm and uses the penalty function and the gradient method to calculate the posture under the condition that the optimal cable force distribution is satisfied. It then analyzes the influence of factors such as the layout shape of the rope exit points of the static platform and the platform shape on the positioning accuracy. MATLAB simulation results show that the positioning error of the tension homogenization optimization algorithm is less than 10-6 mm, and that the tension meets the expected requirements. The model that considers the posture of the motion platform can correct the deflection angle of more than 6°. The deflection angle error caused by different rope exit points can reach at most 4.5°. The greater the difference between the length and width of the motion platform, the greater its influence on the posture. Prototype experimental results show that the algorithm has high accuracy and feasibility. The research can help realize the high-precision positioning of the flexible four-cable parallel robot motion platform.
Ignoring the posture of the end motion platform of a plane flexible four-cable parallel robot may cause positioning errors. On the premise that the platform posture is considered, this paper sets up the robot’s kinematics model and carries out the static analysis of the end platform so as to optimize the minimum variance of the tension of each flexible cable. The paper proposes the tension homogenization optimization algorithm and uses the penalty function and the gradient method to calculate the posture under the condition that the optimal cable force distribution is satisfied. It then analyzes the influence of factors such as the layout shape of the rope exit points of the static platform and the platform shape on the positioning accuracy. MATLAB simulation results show that the positioning error of the tension homogenization optimization algorithm is less than 10-6 mm, and that the tension meets the expected requirements. The model that considers the posture of the motion platform can correct the deflection angle of more than 6°. The deflection angle error caused by different rope exit points can reach at most 4.5°. The greater the difference between the length and width of the motion platform, the greater its influence on the posture. Prototype experimental results show that the algorithm has high accuracy and feasibility. The research can help realize the high-precision positioning of the flexible four-cable parallel robot motion platform.
2021, 40(11): 1703-1709.
doi: 10.13433/j.cnki.1003-8728.20200264
Abstract:
In view of the difficulty and low calculation efficiency in analyzing the random response of the nonlinear system of the wire-cable vibration isolator, a statistical linearization analysis method for the random response characteristics of the nonlinear system of wire-cable isolator was proposed, and the numerical simulation was carried out to verify the effectiveness of the method. Simultaneously the displacement transfer rate was calculated to evaluate the vibration isolation effect of the wire-cable isolator. Research indicated that the results of the proposed method are consistent with the numerical simulation, and it can be used to analyze the random response accurately and effectively. Moreover, the proposed method is more efficient than the numerical simulation, significantly improving the design efficiency of the nonlinear vibration isolation system.
In view of the difficulty and low calculation efficiency in analyzing the random response of the nonlinear system of the wire-cable vibration isolator, a statistical linearization analysis method for the random response characteristics of the nonlinear system of wire-cable isolator was proposed, and the numerical simulation was carried out to verify the effectiveness of the method. Simultaneously the displacement transfer rate was calculated to evaluate the vibration isolation effect of the wire-cable isolator. Research indicated that the results of the proposed method are consistent with the numerical simulation, and it can be used to analyze the random response accurately and effectively. Moreover, the proposed method is more efficient than the numerical simulation, significantly improving the design efficiency of the nonlinear vibration isolation system.
2021, 40(11): 1710-1716.
doi: 10.13433/j.cnki.1003-8728.20200266
Abstract:
The whole model of catenary-pantograph-shroud-train is established. Based on the method of separated vortex simulation, the unsteady aerodynamic characteristics of the pantograph with different height shroud under the action of cross wind are studied, and the variation laws of vorticity, streamline and aerodynamic load are analyzed. The simulation results show that when the height of the shroud is 100 mm, the separation vortices deflect significantly to the leeward side of the crosswind; and when the height of the shroud is 400 mm, the effects on the lower bars of the pantograph and the joints of the car body are enhanced; when the height of the shroud is 200 mm, the effect of the crosswind on the deflection of the flow field is obviously improved, and the distribution of the flow field is symmetrical in the longitudinal direction, and the increase of the resistance coefficient is much smaller than that of the pantograph. The reduction of the transverse force on the pantograph greatly reduces the overturning moment and the side deflection moment, so it is advisable to use a 200 mm height deflector in the harsh wind environment. These results are significant to the study of the influence of the shroud height on the aerodynamic characteristics of the pantograph under cross wind action.
The whole model of catenary-pantograph-shroud-train is established. Based on the method of separated vortex simulation, the unsteady aerodynamic characteristics of the pantograph with different height shroud under the action of cross wind are studied, and the variation laws of vorticity, streamline and aerodynamic load are analyzed. The simulation results show that when the height of the shroud is 100 mm, the separation vortices deflect significantly to the leeward side of the crosswind; and when the height of the shroud is 400 mm, the effects on the lower bars of the pantograph and the joints of the car body are enhanced; when the height of the shroud is 200 mm, the effect of the crosswind on the deflection of the flow field is obviously improved, and the distribution of the flow field is symmetrical in the longitudinal direction, and the increase of the resistance coefficient is much smaller than that of the pantograph. The reduction of the transverse force on the pantograph greatly reduces the overturning moment and the side deflection moment, so it is advisable to use a 200 mm height deflector in the harsh wind environment. These results are significant to the study of the influence of the shroud height on the aerodynamic characteristics of the pantograph under cross wind action.
2021, 40(11): 1717-1722.
doi: 10.13433/j.cnki.1003-8728.20200371
Abstract:
To explore the influence of the connection between the leaf spring of balanced suspension and axle on vehicle ride comfort, a heavy commercial vehicle made is taken as the research object. The sliding and rubber connection modes were developed and applied to the coupled dynamics model. Further, the simulations are carried to obtain the ride comfort data that shows the vehicle ride comfort with the rubber mode is better than sliding mode but still have improved space. A mathematical model, with the three-directional ride comfort of multi-point under the axle vibration transfer path as the objective function, the rubber translational and rotational stiffness coefficient as optimization variables, and suspension working space as the constraint conditions, was established. Next, the dynamic model, multi-island genetic algorithm, optimization variables, objective function, and constraint conditions are integrated into a multidisciplinary optimization platform to optimize the stiffness of rubber with a multi-software coupling calculation method. Finally, comparing the ride comfort response under the rubber stiffness parameters before and after optimization, illustrating the ride comfort has improved by about 8% with the optimized stiffness parameters. Besides, the improvement is mainly due to the reduction of medium-high frequency vibration.
To explore the influence of the connection between the leaf spring of balanced suspension and axle on vehicle ride comfort, a heavy commercial vehicle made is taken as the research object. The sliding and rubber connection modes were developed and applied to the coupled dynamics model. Further, the simulations are carried to obtain the ride comfort data that shows the vehicle ride comfort with the rubber mode is better than sliding mode but still have improved space. A mathematical model, with the three-directional ride comfort of multi-point under the axle vibration transfer path as the objective function, the rubber translational and rotational stiffness coefficient as optimization variables, and suspension working space as the constraint conditions, was established. Next, the dynamic model, multi-island genetic algorithm, optimization variables, objective function, and constraint conditions are integrated into a multidisciplinary optimization platform to optimize the stiffness of rubber with a multi-software coupling calculation method. Finally, comparing the ride comfort response under the rubber stiffness parameters before and after optimization, illustrating the ride comfort has improved by about 8% with the optimized stiffness parameters. Besides, the improvement is mainly due to the reduction of medium-high frequency vibration.
2021, 40(11): 1723-1729.
doi: 10.13433/j.cnki.1003-8728.20200359
Abstract:
Under the cloud service platform, in order to improve the quality of product design service recommendation and enhance the interaction between users and service providers during the process of product collaborative design, the framework of personalized product design service recommendation was built, and a design service recommendation method for considering user demand preference was developed. Firstly, Fuzzy C-means (FCM) clustering algorithm was adopted to fulfill initial clustering of users. Then, optimizing the function of user similarity and score prediction by improved collaborative filtering method based on user (User-based CF) to increase the accuracy of the target users for predicting scores design service recommendation items. Finally, the update and iteration of product design services could be realized through the interactive feedback of users on design service recommendation results. The design requirement of wall-mounted intelligent air conditioning which submitted by the users in Design Cloud Service Platform was taken as an example to verify the effectiveness of the proposed method.
Under the cloud service platform, in order to improve the quality of product design service recommendation and enhance the interaction between users and service providers during the process of product collaborative design, the framework of personalized product design service recommendation was built, and a design service recommendation method for considering user demand preference was developed. Firstly, Fuzzy C-means (FCM) clustering algorithm was adopted to fulfill initial clustering of users. Then, optimizing the function of user similarity and score prediction by improved collaborative filtering method based on user (User-based CF) to increase the accuracy of the target users for predicting scores design service recommendation items. Finally, the update and iteration of product design services could be realized through the interactive feedback of users on design service recommendation results. The design requirement of wall-mounted intelligent air conditioning which submitted by the users in Design Cloud Service Platform was taken as an example to verify the effectiveness of the proposed method.
2021, 40(11): 1730-1734.
doi: 10.13433/j.cnki.1003-8728.20200278
Abstract:
An adaptive tree support generation algorithm is proposed in order to reduce the cost of supporting materials and save printing time. The algorithm identifies the triangles to be supported and divides them into separate areas, then the adaptive sampling algorithm based on the area contour is used to obtain the point to be supported. After that, according to the critical inclination constraint condition, the principle of nearest point combination is adopted to calculate the intermediate nodes of the tree support structure from top to bottom. Finally, the sweeping method is used to materialize the support path, and the support structure connected to the model is sharpened to make it peel easily. The experimental results show that the algorithm can reduce the number of points to be supported and the consumption of supporting materials and printing time while ensuring the stability.
An adaptive tree support generation algorithm is proposed in order to reduce the cost of supporting materials and save printing time. The algorithm identifies the triangles to be supported and divides them into separate areas, then the adaptive sampling algorithm based on the area contour is used to obtain the point to be supported. After that, according to the critical inclination constraint condition, the principle of nearest point combination is adopted to calculate the intermediate nodes of the tree support structure from top to bottom. Finally, the sweeping method is used to materialize the support path, and the support structure connected to the model is sharpened to make it peel easily. The experimental results show that the algorithm can reduce the number of points to be supported and the consumption of supporting materials and printing time while ensuring the stability.
2021, 40(11): 1735-1740.
doi: 10.13433/j.cnki.1003-8728.20200260
Abstract:
The surface integrity of aeroengine blades seriously affects the fatigue strength and service life of the blades. In order to master the key parameters of the surface integrity of the flexible polishing blade of abrasive cloth wheel, the polishing test and the surface integrity test of TC4 blade were carried out based on the polishing technology equipment of "NC machine + flexible grinding head + elastic grinding tool (abrasive cloth wheel) ". The changes of surface integrity parameters before and after polishing were compared, and the changes mechanism was analyzed, the results show that the flexible polishing of abrasive cloth wheel can obviously improve the surface roughness, surface micro-morphology, surface residual stress and surface micro-hardness, however, the residual stress in depth direction, microhardness in depth direction and microstructure were not affected. The results provide a basis for surface integrity control of abrasive cloth wheel.
The surface integrity of aeroengine blades seriously affects the fatigue strength and service life of the blades. In order to master the key parameters of the surface integrity of the flexible polishing blade of abrasive cloth wheel, the polishing test and the surface integrity test of TC4 blade were carried out based on the polishing technology equipment of "NC machine + flexible grinding head + elastic grinding tool (abrasive cloth wheel) ". The changes of surface integrity parameters before and after polishing were compared, and the changes mechanism was analyzed, the results show that the flexible polishing of abrasive cloth wheel can obviously improve the surface roughness, surface micro-morphology, surface residual stress and surface micro-hardness, however, the residual stress in depth direction, microhardness in depth direction and microstructure were not affected. The results provide a basis for surface integrity control of abrasive cloth wheel.
2021, 40(11): 1741-1746.
doi: 10.13433/j.cnki.1003-8728.20200268
Abstract:
An approach to detect the blade surface strain of wind turbine with Fiber Bragg Grating (FBG) is proposed. The distribution of blade surface strain is obtained via the numerical simulation. The detection method with FBG is designed and the experiment of blade surface strain detection is carried out. The feasibility and effectiveness of this method are verified by comparing the experimental results with the simulated. The results show that structure of FBG sensor is light and simple with high signal-to-noise ratio. And the present approach can detect the blade surface strain of wind turbine quickly and accurately.
An approach to detect the blade surface strain of wind turbine with Fiber Bragg Grating (FBG) is proposed. The distribution of blade surface strain is obtained via the numerical simulation. The detection method with FBG is designed and the experiment of blade surface strain detection is carried out. The feasibility and effectiveness of this method are verified by comparing the experimental results with the simulated. The results show that structure of FBG sensor is light and simple with high signal-to-noise ratio. And the present approach can detect the blade surface strain of wind turbine quickly and accurately.
2021, 40(11): 1747-1753.
doi: 10.13433/j.cnki.1003-8728.20200280
Abstract:
According to compressed sensing theory, the reconstruction algorithm with convex optimization method has some problems such as larger reconstruction error, more reconstruction iterations and lower reconstruction error signal-to-noise ratio in the application of rolling bearing fault signals. In order to improve these shortcomings, this paper proposes a new algorithm that uses the arc sine function instead of the hyperbolic function to approximate the l0 norm, which makes the approximation degree of the function curve and the l0 norm higher and smoother. At the same time, the attenuation factor is added to accelerate the iteration speed. The experimental results show that the proposed algorithm reduces the number of iterations to some extent, but loses some reconstruction accuracy. However, compared with the existing algorithms, the overall reconstruction effect has the advantages of higher reconstruction accuracy, fewer iterations and higher reconstruction SNR.
According to compressed sensing theory, the reconstruction algorithm with convex optimization method has some problems such as larger reconstruction error, more reconstruction iterations and lower reconstruction error signal-to-noise ratio in the application of rolling bearing fault signals. In order to improve these shortcomings, this paper proposes a new algorithm that uses the arc sine function instead of the hyperbolic function to approximate the l0 norm, which makes the approximation degree of the function curve and the l0 norm higher and smoother. At the same time, the attenuation factor is added to accelerate the iteration speed. The experimental results show that the proposed algorithm reduces the number of iterations to some extent, but loses some reconstruction accuracy. However, compared with the existing algorithms, the overall reconstruction effect has the advantages of higher reconstruction accuracy, fewer iterations and higher reconstruction SNR.
2021, 40(11): 1754-1759.
doi: 10.13433/j.cnki.1003-8728.20200557
Abstract:
According to the structural characteristics and working principle of linear compressor, the control strategy of linear compressor was divided into mechanical and electromagnetic parts. The physical models for the two parts are constructed respectively. On the basis of the physical model, the linear compressor state equation was constructed with the driving voltage as the input and the piston displacement as the output. The variable speed reaching law sliding mode control algorithm proposed in this paper was used to design the linear compressor controller, and the linear compressor control system was built in Simulink. The present method was compared with the traditional exponential reaching law controller by using the numerical simulation. The results show that the sliding mode controller with variable speed reaching law is superior to the controller with the uniform exponential reaching law in the steady-state time and chattering degree, and the control accuracy is improved by 20%. At the same time, when α =1.346、k = 13.499, the sliding mode controller with the variable speed reaching law achieves the optimal control effect. The control error is between 4% and 7.8%, which verifies the control accuracy and effectiveness of the controller.
According to the structural characteristics and working principle of linear compressor, the control strategy of linear compressor was divided into mechanical and electromagnetic parts. The physical models for the two parts are constructed respectively. On the basis of the physical model, the linear compressor state equation was constructed with the driving voltage as the input and the piston displacement as the output. The variable speed reaching law sliding mode control algorithm proposed in this paper was used to design the linear compressor controller, and the linear compressor control system was built in Simulink. The present method was compared with the traditional exponential reaching law controller by using the numerical simulation. The results show that the sliding mode controller with variable speed reaching law is superior to the controller with the uniform exponential reaching law in the steady-state time and chattering degree, and the control accuracy is improved by 20%. At the same time, when α =1.346、k = 13.499, the sliding mode controller with the variable speed reaching law achieves the optimal control effect. The control error is between 4% and 7.8%, which verifies the control accuracy and effectiveness of the controller.
2021, 40(11): 1760-1766.
doi: 10.13433/j.cnki.1003-8728.20200267
Abstract:
Non-road vehicles often travel on non-paved road, therefore, they may be shocked and vibrated in multiple directions due to uneven road surface, acceleration and deceleration, as well as turning and direction change, etc. However, present seat suspension of such vehicles cannot effectively attenuate such shock vibrations. Most of current researches on the vibration reduction of seat suspensions focus on passive vibration reduction and vibration reduction in the vertical direction, and research on multi-dimensional coordinated active vibration reduction is relatively rare. To this end, the 3-RCC parallel mechanism which is able to attenuate multi-dimensional vibration is used as the seat suspension system. The virtual prototype of the 3-RCC suspension model, combined with the active control module, is built in ADAMS, and the controller is built in MATLAB/Simulink for the joint simulation of ADAMS and MATLAB. The simulation results show that the 3-RCC seat suspension can coordinate the vibration reduction in multi-dimension, and driver' s ride comfort is further improved by combining the active control module.
Non-road vehicles often travel on non-paved road, therefore, they may be shocked and vibrated in multiple directions due to uneven road surface, acceleration and deceleration, as well as turning and direction change, etc. However, present seat suspension of such vehicles cannot effectively attenuate such shock vibrations. Most of current researches on the vibration reduction of seat suspensions focus on passive vibration reduction and vibration reduction in the vertical direction, and research on multi-dimensional coordinated active vibration reduction is relatively rare. To this end, the 3-RCC parallel mechanism which is able to attenuate multi-dimensional vibration is used as the seat suspension system. The virtual prototype of the 3-RCC suspension model, combined with the active control module, is built in ADAMS, and the controller is built in MATLAB/Simulink for the joint simulation of ADAMS and MATLAB. The simulation results show that the 3-RCC seat suspension can coordinate the vibration reduction in multi-dimension, and driver' s ride comfort is further improved by combining the active control module.
2021, 40(11): 1767-1772.
doi: 10.13433/j.cnki.1003-8728.20200282
Abstract:
In order to reduce the traffic accidents caused by driver fatigue driving, it is necessary to carry out driver fatigue detection research. In order to meet the requirements of online real-time detection, a fatigue detection method for motor vehicle drivers based on facial features is proposed in this paper. Firstly, the MTCNN (multi-task cascaded convolutional networks) face detection network is optimized and accelerated by reducing the detection area through background difference, reducing the number of pyramid layers of image, etc., and the speed after acceleration is 258% times faster than before. Secondly, the multi-level cascaded residual regression tree is used to detect the feature points of driver' s face, and 68 feature points of the face are obtained. Finally, the driver fatigue detection model is established and trained by combining the features of face mouth and eye opening. The experimental results show that the accuracy of the proposed fatigue detection method can reach 95.4%, the average detection speed of each frame is 64ms, and the detection speed is fast enough for meeting the requirements of real-time
In order to reduce the traffic accidents caused by driver fatigue driving, it is necessary to carry out driver fatigue detection research. In order to meet the requirements of online real-time detection, a fatigue detection method for motor vehicle drivers based on facial features is proposed in this paper. Firstly, the MTCNN (multi-task cascaded convolutional networks) face detection network is optimized and accelerated by reducing the detection area through background difference, reducing the number of pyramid layers of image, etc., and the speed after acceleration is 258% times faster than before. Secondly, the multi-level cascaded residual regression tree is used to detect the feature points of driver' s face, and 68 feature points of the face are obtained. Finally, the driver fatigue detection model is established and trained by combining the features of face mouth and eye opening. The experimental results show that the accuracy of the proposed fatigue detection method can reach 95.4%, the average detection speed of each frame is 64ms, and the detection speed is fast enough for meeting the requirements of real-time
2021, 40(11): 1773-1778.
doi: 10.13433/j.cnki.1003-8728.20200269
Abstract:
A progressive damage model by considering the hygrothermal effect was established to study the damage behavior of honeycomb sandwich panel with plain weave panel under lateral compression. The UMAT subroutine is written to take the influence of the hygrothermal effect on the constitutive relation, the influence of the change in temperature on the material properties, the selected failure criteria and the stiffness degradation model into the progressive damage analysis. The predicted load-displacement curve and failure mode via the model at 25 ℃ and 0 moisture absorption were compared with the experimental in order to verify the correctness of the model. Furthermore, the influence of the hygrothermal effect on the bearing strength of the honeycomb sandwich panel subjected to the lateral compression load is studied at 5 temperatures and 5 humidities. The results show that the model can effectively predict the damage propagation process and the influence of the hygrothermal environment on the performance of the honeycomb sandwich panel. The results show that the bearing strength of the honeycomb sandwich panel decreases gradually with the increasing of temperature and humidity.
A progressive damage model by considering the hygrothermal effect was established to study the damage behavior of honeycomb sandwich panel with plain weave panel under lateral compression. The UMAT subroutine is written to take the influence of the hygrothermal effect on the constitutive relation, the influence of the change in temperature on the material properties, the selected failure criteria and the stiffness degradation model into the progressive damage analysis. The predicted load-displacement curve and failure mode via the model at 25 ℃ and 0 moisture absorption were compared with the experimental in order to verify the correctness of the model. Furthermore, the influence of the hygrothermal effect on the bearing strength of the honeycomb sandwich panel subjected to the lateral compression load is studied at 5 temperatures and 5 humidities. The results show that the model can effectively predict the damage propagation process and the influence of the hygrothermal environment on the performance of the honeycomb sandwich panel. The results show that the bearing strength of the honeycomb sandwich panel decreases gradually with the increasing of temperature and humidity.
2021, 40(11): 1779-1786.
doi: 10.13433/j.cnki.1003-8728.20200265
Abstract:
In consideration of high speed and heavy load operation characteristics of non-orthogonal aerospace spiral bevel gears and high tooth flank grinding accuracy, it is very difficult to achieve the matching of the actual tooth surface and the theoretical tooth surface. For satisfying the high accuracy and efficiency, an adaptive machine settings driven tooth flank accuracy control is proposed. Firstly, with simulation of advanced free-form grinding, machine settings driven tooth flank mathematical modeling is performed. Then, for tooth flank grinding accuracy control, adaptive grinding accuracy control model is established by correlating with the tooth flank form error measurement, tooth flank design and tooth flank form error modification. Finally, with applications of tooth flank form error sensitivity analysis strategy and the improved Levenberg-Marquardt algorithm, the adaptive approximation of the preset target tooth surface is achieved, and the final precise machine tool machining parameters are solved. Given numerical instance in this work can verify the validation of the proposed method.
In consideration of high speed and heavy load operation characteristics of non-orthogonal aerospace spiral bevel gears and high tooth flank grinding accuracy, it is very difficult to achieve the matching of the actual tooth surface and the theoretical tooth surface. For satisfying the high accuracy and efficiency, an adaptive machine settings driven tooth flank accuracy control is proposed. Firstly, with simulation of advanced free-form grinding, machine settings driven tooth flank mathematical modeling is performed. Then, for tooth flank grinding accuracy control, adaptive grinding accuracy control model is established by correlating with the tooth flank form error measurement, tooth flank design and tooth flank form error modification. Finally, with applications of tooth flank form error sensitivity analysis strategy and the improved Levenberg-Marquardt algorithm, the adaptive approximation of the preset target tooth surface is achieved, and the final precise machine tool machining parameters are solved. Given numerical instance in this work can verify the validation of the proposed method.
2021, 40(11): 1787-1792.
doi: 10.13433/j.cnki.1003-8728.20200275
Abstract:
Roller expansion is one of the most important surface strengthening methods. After experiencing the roller expansion, the fatigue life of the structure can be improved due to the generation of residual stress around the hole. However, how the roller expansion parameters effect the residual stress and fatigue life of TA15 alloy needs to be further investigated. The simulation model for the roller expansion of TA15 alloy is built in terms of the Johnson-Cook law. The generation, extension and working mechanism of residual stress are revealed by considering different interference and friction coefficients. The movement of the materials around the hole is also discussed. The fatigue experiment is conducted to study the improvement of the fatigue life after roller expansion. It is found that the machining parameters has the significant effects on the residual stress and fatigue life.
Roller expansion is one of the most important surface strengthening methods. After experiencing the roller expansion, the fatigue life of the structure can be improved due to the generation of residual stress around the hole. However, how the roller expansion parameters effect the residual stress and fatigue life of TA15 alloy needs to be further investigated. The simulation model for the roller expansion of TA15 alloy is built in terms of the Johnson-Cook law. The generation, extension and working mechanism of residual stress are revealed by considering different interference and friction coefficients. The movement of the materials around the hole is also discussed. The fatigue experiment is conducted to study the improvement of the fatigue life after roller expansion. It is found that the machining parameters has the significant effects on the residual stress and fatigue life.
2021, 40(11): 1793-1797.
doi: 10.13433/j.cnki.1003-8728.20200281
Abstract:
In the development of thrust vectoring system of a scaled jet UAV, the axisymmetric rotating function has been achieved by designing a kind link mechanism, which is driven by two electric steering servos. By analyzing the force and motion states in the process of thrust vectoring nozzle rotating, the relationship between the maximum servo torque needed and the maximum hinge torque is obtained. Then, methods of engineering estimation and CFD numerical simulation have been implemented on calculating the hinge moment generated by the thrust vectoring nozzle when rotating. The calculation results of hinge moment were used to select suitable electric steering servo, which has enough torque to against the hinge moment. Finally, the results of ground test and flight test demonstrated good performance of the axisymmetric thrust vectoring system, which meeting requirements of engineering application.
In the development of thrust vectoring system of a scaled jet UAV, the axisymmetric rotating function has been achieved by designing a kind link mechanism, which is driven by two electric steering servos. By analyzing the force and motion states in the process of thrust vectoring nozzle rotating, the relationship between the maximum servo torque needed and the maximum hinge torque is obtained. Then, methods of engineering estimation and CFD numerical simulation have been implemented on calculating the hinge moment generated by the thrust vectoring nozzle when rotating. The calculation results of hinge moment were used to select suitable electric steering servo, which has enough torque to against the hinge moment. Finally, the results of ground test and flight test demonstrated good performance of the axisymmetric thrust vectoring system, which meeting requirements of engineering application.
2021, 40(11): 1798-1804.
doi: 10.13433/j.cnki.1003-8728.20200565
Abstract:
The skid landing gear used in UAV often uses bow beam structure, and the upper beam is a kind of slender elastic body, which is similar to bamboo structure (with large slenderness ratio). In order to improve the structural performance of skid landing gear, First of all, refer to the microstructure of bamboo, three kinds of bionic circular tubes with similar vascular bundles are designed, the axial and radial collision energy absorption of bionic tube are simulated and calculated by finite element method; secondly through the finite element static and dynamic analysis, the mechanical properties of the original structure and the bamboo-like structure are compared under the same load. The simulation results show that in the static analysis, the maximum stress of the imitation bamboo structure is reduced by about 44% compared with the original structure, and the stress concentration at the joint between the bow beam and the sliding cylinder is improved. The possible smooth landing and non-smooth landing of the landing gear is simulated through multi-operating conditions in the dynamic analysis, and the maximum stress under multiple operating conditions of the bamboo-like structure is reduced by about 22% on average, it shows that the bamboo-like structure can effectively improve the landing performance.
The skid landing gear used in UAV often uses bow beam structure, and the upper beam is a kind of slender elastic body, which is similar to bamboo structure (with large slenderness ratio). In order to improve the structural performance of skid landing gear, First of all, refer to the microstructure of bamboo, three kinds of bionic circular tubes with similar vascular bundles are designed, the axial and radial collision energy absorption of bionic tube are simulated and calculated by finite element method; secondly through the finite element static and dynamic analysis, the mechanical properties of the original structure and the bamboo-like structure are compared under the same load. The simulation results show that in the static analysis, the maximum stress of the imitation bamboo structure is reduced by about 44% compared with the original structure, and the stress concentration at the joint between the bow beam and the sliding cylinder is improved. The possible smooth landing and non-smooth landing of the landing gear is simulated through multi-operating conditions in the dynamic analysis, and the maximum stress under multiple operating conditions of the bamboo-like structure is reduced by about 22% on average, it shows that the bamboo-like structure can effectively improve the landing performance.
