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RSS2019 Vol. 38, No. 12
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2019, 38(12): 1805-1811.
doi: 10.13433/j.cnki.1003-8728.20190052
PDF 1088KB
Abstract:
This paper studied the three-dimensional numerical simulation of the cutterhead's rock cutting process of a cutter suction dredger. With the discrete element method, the virtual repose test was used to calibrate the friction coefficient of particles and boundary; the virtual uniaxial compression test and the Brazilian test were used to calibrate the contact parameters of the particles, which were used to simulate the rock cutting process of the cutterhead of a cutter suction dredger. The simulation results show that the cutting morphology matches the actuality and that the average torque is basically consistent with the experimental results and the finite element simulation value, thus verifying the reliability of the parameter calibration process. The research results are useful for predicting the force of a cutterhead. At the same time, unlike the finite element simulation, the broken debris particles are constantly moving, thus allowing the further study of the transfer of debris particles.
This paper studied the three-dimensional numerical simulation of the cutterhead's rock cutting process of a cutter suction dredger. With the discrete element method, the virtual repose test was used to calibrate the friction coefficient of particles and boundary; the virtual uniaxial compression test and the Brazilian test were used to calibrate the contact parameters of the particles, which were used to simulate the rock cutting process of the cutterhead of a cutter suction dredger. The simulation results show that the cutting morphology matches the actuality and that the average torque is basically consistent with the experimental results and the finite element simulation value, thus verifying the reliability of the parameter calibration process. The research results are useful for predicting the force of a cutterhead. At the same time, unlike the finite element simulation, the broken debris particles are constantly moving, thus allowing the further study of the transfer of debris particles.
2019, 38(12): 1812-1818.
doi: 10.13433/j.cnki.1003-8728.20190094
Abstract:
The paper studies a new hybrid rotary table with spiral oil wedge. The influence of different rotational speed and thickness of oil film on the pressure field distribution is simulated with the commercial CFD software based on the Navier-Stokes equation. The simulation results show that the oil film thickness has a more significant influence on the hydrostatic pressure than the rotational speed when the pressure applied is the same, while the oil film thickness and rotational speed both obviously affect the hydrodynamic pressure. The hydrodynamic pressure peak is higher than the hydrostatic pressure recess when the oil film thickness is the same and the rotational speed is higher. Experiments are carried out to measure the oil film pressure, and the experimental results show a good agreement with the simulation results, verifying the effectiveness of the numerical simulation.
The paper studies a new hybrid rotary table with spiral oil wedge. The influence of different rotational speed and thickness of oil film on the pressure field distribution is simulated with the commercial CFD software based on the Navier-Stokes equation. The simulation results show that the oil film thickness has a more significant influence on the hydrostatic pressure than the rotational speed when the pressure applied is the same, while the oil film thickness and rotational speed both obviously affect the hydrodynamic pressure. The hydrodynamic pressure peak is higher than the hydrostatic pressure recess when the oil film thickness is the same and the rotational speed is higher. Experiments are carried out to measure the oil film pressure, and the experimental results show a good agreement with the simulation results, verifying the effectiveness of the numerical simulation.
2019, 38(12): 1819-1824.
doi: 10.13433/j.cnki.1003-8728.20190069
Abstract:
In order to analyze the dynamic characteristics of the lower limb including the musculoskeletal system in human gait movement, the lower limb motion model including the musculoskeletal system are established by using a biomechanics software, AnyBodyTM Modeling System. By using the reverse dynamics, the human body is driven by the three-dimensional coordinates of the motion control points set on the lower limb joints and the ground reaction force. Then the normal gait simulation of the human body is completed. The curves of the angles and moments of the ankle joint and knee joint in the normal gait are obtained, and the relationship between the joint torque and the angle is analyzed. The curves of the muscle strength and muscle activity of the soleus, sartorius, tibialis posterior and tibialis anterior muscle are given in the gait cycle. The relationship between the muscle strength and activity is discussed.
In order to analyze the dynamic characteristics of the lower limb including the musculoskeletal system in human gait movement, the lower limb motion model including the musculoskeletal system are established by using a biomechanics software, AnyBodyTM Modeling System. By using the reverse dynamics, the human body is driven by the three-dimensional coordinates of the motion control points set on the lower limb joints and the ground reaction force. Then the normal gait simulation of the human body is completed. The curves of the angles and moments of the ankle joint and knee joint in the normal gait are obtained, and the relationship between the joint torque and the angle is analyzed. The curves of the muscle strength and muscle activity of the soleus, sartorius, tibialis posterior and tibialis anterior muscle are given in the gait cycle. The relationship between the muscle strength and activity is discussed.
2019, 38(12): 1825-1831.
doi: 10.13433/j.cnki.1003-8728.20190063
Abstract:
The crankshaft vibration model of 12V150 diesel engine was established according to the crankshaft dynamics and harmonic analysis theory. Based on this model, the three-dimensional coupled vibration phenomenon and mechanism of crankshaft of high power density diesel engine was studied. Then the influence of installing torsion damper on the three-dimensional coupled vibration was probed. The results show that the torsional amplitude is larger in the case of 3d and 4.5d orders, and the bending vibration peaks occur in a wide frequency range. Torsional and bending vibration of multiple orders can cause the same frequency or double frequency axis vibration. A coupling relationship exists between the three-dimensional and the adjacent main journal. The installation of the torsion damper has obvious effect on the control of torsion vibration and can reduce bending and axial vibration amplitude of several major orders, while the vertical bending vibration and axial vibration increase at low rotating speed. The analysis of results indicates that the main working speed range and three-dimensional vibration coupling effect should be considered particularly.
The crankshaft vibration model of 12V150 diesel engine was established according to the crankshaft dynamics and harmonic analysis theory. Based on this model, the three-dimensional coupled vibration phenomenon and mechanism of crankshaft of high power density diesel engine was studied. Then the influence of installing torsion damper on the three-dimensional coupled vibration was probed. The results show that the torsional amplitude is larger in the case of 3d and 4.5d orders, and the bending vibration peaks occur in a wide frequency range. Torsional and bending vibration of multiple orders can cause the same frequency or double frequency axis vibration. A coupling relationship exists between the three-dimensional and the adjacent main journal. The installation of the torsion damper has obvious effect on the control of torsion vibration and can reduce bending and axial vibration amplitude of several major orders, while the vertical bending vibration and axial vibration increase at low rotating speed. The analysis of results indicates that the main working speed range and three-dimensional vibration coupling effect should be considered particularly.
2019, 38(12): 1832-1839.
doi: 10.13433/j.cnki.1003-8728.20190240
Abstract:
A control algorithm referred to as Space Tolerance Constrain Control (STCC) was proposed for active training on an upper limb rehabilitation robot. The STCC can automatically restrict the robot's TCP, which pose was determined by trainee, not to go outside the tolerance volume wrapping a given trajectory. The tolerance volume consists of two planes, which are parallel to the trajectory plane and located on both sides of the one, and two surfaces to be perpendicular to the trajectory plane, which go through two offset curves on both sides of the trajectory. The restriction strength is proportional to the deviation of TCP from the given trajectory. Once the TCP goes unexpectedly outside the tolerance volume, the STCC can quickly switch the active control mode into the passive to drive the TCP to a point on the trajectory. For the reason of real-time sensing in the process of training, the multi-thread technique was used in programming. Finally, the desired control results were arose from experimental operations.
A control algorithm referred to as Space Tolerance Constrain Control (STCC) was proposed for active training on an upper limb rehabilitation robot. The STCC can automatically restrict the robot's TCP, which pose was determined by trainee, not to go outside the tolerance volume wrapping a given trajectory. The tolerance volume consists of two planes, which are parallel to the trajectory plane and located on both sides of the one, and two surfaces to be perpendicular to the trajectory plane, which go through two offset curves on both sides of the trajectory. The restriction strength is proportional to the deviation of TCP from the given trajectory. Once the TCP goes unexpectedly outside the tolerance volume, the STCC can quickly switch the active control mode into the passive to drive the TCP to a point on the trajectory. For the reason of real-time sensing in the process of training, the multi-thread technique was used in programming. Finally, the desired control results were arose from experimental operations.
2019, 38(12): 1840-1846.
doi: 10.13433/j.cnki.1003-8728.20190060
Abstract:
The analysis of the flow field state in the working chamber during the operation of the scroll compressor is difficult to obtain through test and measurement. For this reason, this paper establishes a three-dimensional flow field numerical model with dynamic and static scrolls with dynamic boundary, radial and axial clearances, with the moving and static scrolls of the circular involute profile. The CFD dynamic mesh technology is used to set the flow field boundary and the internal mesh deformation to obtain the internal flow field parameters of the dynamic and static scroll meshing process, and the simulation results are verified by the test. The results show that the simulation results are basically consistent with the experimental results. The dynamic distribution of the pressure and velocity of the gas flow in the working chamber is obtained, the causes of uneven distribution of pressure, velocity and temperature in the compression process were explored.
The analysis of the flow field state in the working chamber during the operation of the scroll compressor is difficult to obtain through test and measurement. For this reason, this paper establishes a three-dimensional flow field numerical model with dynamic and static scrolls with dynamic boundary, radial and axial clearances, with the moving and static scrolls of the circular involute profile. The CFD dynamic mesh technology is used to set the flow field boundary and the internal mesh deformation to obtain the internal flow field parameters of the dynamic and static scroll meshing process, and the simulation results are verified by the test. The results show that the simulation results are basically consistent with the experimental results. The dynamic distribution of the pressure and velocity of the gas flow in the working chamber is obtained, the causes of uneven distribution of pressure, velocity and temperature in the compression process were explored.
2019, 38(12): 1847-1853.
doi: 10.13433/j.cnki.1003-8728.20190058
Abstract:
In order to make the VX380T CNC machining center worktable have superior static performance, dynamic performance and lightweight features, the optimal load transfer path of the worktable section was studied by the method of topological analysis. Based on the analysis results of the topology, the stiffener layout of the worktable was designed. A multi-objective parameter optimization of the redesigned worktable was carried out. The mass and harmonic response amplitude of the new worktable are taken as optimization objectives, the structural parameters ware taken as design variables, and the static performance and the natural frequencies of the original worktable was constraint condition. Comparing the optimized design result with the original one, the result showed that the worktable mass reduces by 12.19%, and the static and dynamic performance can be improved simultaneously. The feasibility and validity of optimal design are proved.
In order to make the VX380T CNC machining center worktable have superior static performance, dynamic performance and lightweight features, the optimal load transfer path of the worktable section was studied by the method of topological analysis. Based on the analysis results of the topology, the stiffener layout of the worktable was designed. A multi-objective parameter optimization of the redesigned worktable was carried out. The mass and harmonic response amplitude of the new worktable are taken as optimization objectives, the structural parameters ware taken as design variables, and the static performance and the natural frequencies of the original worktable was constraint condition. Comparing the optimized design result with the original one, the result showed that the worktable mass reduces by 12.19%, and the static and dynamic performance can be improved simultaneously. The feasibility and validity of optimal design are proved.
2019, 38(12): 1854-1860.
doi: 10.13433/j.cnki.1003-8728.20190064
Abstract:
The effects of dimensionless velocity, aspect ratio, skew angle and dimensionless thermoelastic coupling factor on the vibration characteristics of a thermoelastic coupled moving skew plate is analyzed. Taking the moving thermoelastic coupled skew plate as the research object, based on the theory of small deflection bending, the differential equation of motion for elastic thin plate is established, the differential quadrature method is used to establish the characteristic equation of thermoelastic coupled skew plate. The relationship between the dimensionless complex frequencies of the first three modes of a thermoelastic coupled moving skew plate and its velocity is obtained. The results show that the critical velocity of the first mode divergence and instability decreases with the increase of the skew plate angle, and the critical velocity of the first mode divergence and instability increases with the increase of the dimensionless thermoelastic coupling factor under the same conditions.
The effects of dimensionless velocity, aspect ratio, skew angle and dimensionless thermoelastic coupling factor on the vibration characteristics of a thermoelastic coupled moving skew plate is analyzed. Taking the moving thermoelastic coupled skew plate as the research object, based on the theory of small deflection bending, the differential equation of motion for elastic thin plate is established, the differential quadrature method is used to establish the characteristic equation of thermoelastic coupled skew plate. The relationship between the dimensionless complex frequencies of the first three modes of a thermoelastic coupled moving skew plate and its velocity is obtained. The results show that the critical velocity of the first mode divergence and instability decreases with the increase of the skew plate angle, and the critical velocity of the first mode divergence and instability increases with the increase of the dimensionless thermoelastic coupling factor under the same conditions.
2019, 38(12): 1861-1867.
doi: 10.13433/j.cnki.1003-8728.20180082
Abstract:
To study the load characteristics of plow bits under operational conditions, an experimental platform for studying mechanical testing of a coal plow and a system for measuring the triaxial forces acting on the plow bits were developed based on the theory of coal cutting by coal plows. Experimental measurements were performed during the coal cutting process of a BH38/2×400 coal plow. The triaxial forces acting on the cutting bits at different cutting depths and speeds were obtained, and the experimental results were compared with theoretical calculations. The results show that the measured triaxial forces were consistently lower than the corresponding theoretical values for various cutting depths. In addition, the ratios of the experimental values to the theoretical values of the triaxial forces were found to fluctuate at certain values. For different cutting speeds, the experimental values of the triaxial forces deviated from the theoretical values and they were related by certain multiplicative factors.
To study the load characteristics of plow bits under operational conditions, an experimental platform for studying mechanical testing of a coal plow and a system for measuring the triaxial forces acting on the plow bits were developed based on the theory of coal cutting by coal plows. Experimental measurements were performed during the coal cutting process of a BH38/2×400 coal plow. The triaxial forces acting on the cutting bits at different cutting depths and speeds were obtained, and the experimental results were compared with theoretical calculations. The results show that the measured triaxial forces were consistently lower than the corresponding theoretical values for various cutting depths. In addition, the ratios of the experimental values to the theoretical values of the triaxial forces were found to fluctuate at certain values. For different cutting speeds, the experimental values of the triaxial forces deviated from the theoretical values and they were related by certain multiplicative factors.
2019, 38(12): 1868-1876.
doi: 10.13433/j.cnki.1003-8728.20190059
Abstract:
Considering the effects of the axial load, elasto-plastic constitutive, coordinated contact, bearing clearance and other factors, the failure of the ball bearing with deep groove used in an automotive transmission in the service process is solved by the non-Hertz finite element model. Based on the above-mentioned, the failure mechanism of the bearing in the servicing process is obtained. The effects of the constitutive model for bearing material and the alternating load on the contact state are further studied. The results show that the elastic constitutive model has a smaller bearing capacity than the elasto-plastic constitutive model, and the stress level is higher. The load can reduce the internal stress extreme value of the bearing at a certain angle. The stress extreme value and the initial yield depth increases with the increasing of load. But when the load is too large, the initial yield depth decreases sharply.
Considering the effects of the axial load, elasto-plastic constitutive, coordinated contact, bearing clearance and other factors, the failure of the ball bearing with deep groove used in an automotive transmission in the service process is solved by the non-Hertz finite element model. Based on the above-mentioned, the failure mechanism of the bearing in the servicing process is obtained. The effects of the constitutive model for bearing material and the alternating load on the contact state are further studied. The results show that the elastic constitutive model has a smaller bearing capacity than the elasto-plastic constitutive model, and the stress level is higher. The load can reduce the internal stress extreme value of the bearing at a certain angle. The stress extreme value and the initial yield depth increases with the increasing of load. But when the load is too large, the initial yield depth decreases sharply.
2019, 38(12): 1877-1884.
doi: 10.13433/j.cnki.1003-8728.20190074
Abstract:
For the problems of complex and variable vibration signals of planetary gears, feature extraction distortion and small sample size, a new fault diagnosis method combining function data analysis with improved support vector domain description (SVDD) is proposed. According to different fault types of gears, different fault fitting basis functions are established, the training set data is fitted with the Fourier basis function, and the SVDD model is established according to the function coefficient features obtained by fitting, and in a ROC (receiver operating characteristic) of the evaluation function optimization objective simulated annealing algorithm kernel parameter model SVDD penalty factors σ/c and optimized; different test samples are taken into the SVDD model, and the fault type is determined by calculating the relative distance between the test sample and the center of the ball, thereby completing the planetary gear fault diagnosis. The comparison of experimental results shows that the proposed method can accurately identify the types of planetary gear faults.
For the problems of complex and variable vibration signals of planetary gears, feature extraction distortion and small sample size, a new fault diagnosis method combining function data analysis with improved support vector domain description (SVDD) is proposed. According to different fault types of gears, different fault fitting basis functions are established, the training set data is fitted with the Fourier basis function, and the SVDD model is established according to the function coefficient features obtained by fitting, and in a ROC (receiver operating characteristic) of the evaluation function optimization objective simulated annealing algorithm kernel parameter model SVDD penalty factors σ/c and optimized; different test samples are taken into the SVDD model, and the fault type is determined by calculating the relative distance between the test sample and the center of the ball, thereby completing the planetary gear fault diagnosis. The comparison of experimental results shows that the proposed method can accurately identify the types of planetary gear faults.
2019, 38(12): 1885-1893.
doi: 10.13433/j.cnki.1003-8728.20190054
Abstract:
Aiming at the problems including unclear description of the matching relationship between parts and the low accuracy of parts matching in assembly design, a method of structured description and matching reasoning for assemblable features is proposed. Firstly, the definition and structural description of assembly key knots including engineering semantics, assembly constraints, assembly ports and assembly space relations were given, which based on the analysis of the process correlation, matching surface characteristics and assembly design intention that affect parts acquisition, matching, adjustment and assembly. Then, the DFA (design for assembly) of complex product parts based on assembly key knots was analyzed, and the weight of each factor in assembly key knot was determined. In addition, the solution of assembly attribute adjacent graph of complex parts was completed by FTOPSIS (fuzzy technique for order preference by similarity to an ideal solution) in fuzzy set theory, and thus the precise matching between components could be realized from qualitative input to quantitative solution and then to qualitative output. Finally, the validity of the method was verified, and the research result provided a novel approach for efficient and accurate assembly of complex product parts.
Aiming at the problems including unclear description of the matching relationship between parts and the low accuracy of parts matching in assembly design, a method of structured description and matching reasoning for assemblable features is proposed. Firstly, the definition and structural description of assembly key knots including engineering semantics, assembly constraints, assembly ports and assembly space relations were given, which based on the analysis of the process correlation, matching surface characteristics and assembly design intention that affect parts acquisition, matching, adjustment and assembly. Then, the DFA (design for assembly) of complex product parts based on assembly key knots was analyzed, and the weight of each factor in assembly key knot was determined. In addition, the solution of assembly attribute adjacent graph of complex parts was completed by FTOPSIS (fuzzy technique for order preference by similarity to an ideal solution) in fuzzy set theory, and thus the precise matching between components could be realized from qualitative input to quantitative solution and then to qualitative output. Finally, the validity of the method was verified, and the research result provided a novel approach for efficient and accurate assembly of complex product parts.
2019, 38(12): 1894-1903.
doi: 10.13433/j.cnki.1003-8728.20190055
Abstract:
For the traditional acceleration and deceleration algorithms such as S-curve jerk discontinuity, sinusoidal curve snap discontinuity leads to flexible impact in the feed process, an acceleration & deceleration snap continuous control algorithm with asymmetric seven-segment versine curve is proposed in this paper. Considering the optimal mechanical performance of the system, by analyzing the maximum acceleration, maximum deceleration and maximum speed accessibility, 17 types of speed curves are planned; Aiming at the problem that the length of a given trajectory segment is smaller than the shortest trajectory segment length required for the system to move from the starting velocity to the ending velocity, a method for verifying the reachability of the starting velocity and the ending velocity based on the length constraint of the given trajectory segment is proposed. Meanwhile, the Shengjin formula is used to correct the starting speed and the ending speed. The self-developed multi-axis motion controller verifies the proposed all-type asymmetric seven-segment versine curve acceleration & deceleration snap continuous control algorithm. The experimental results show that the algorithm can plan 17 types of speed curves under the condition that the snap is continuous to improve system flexibility and the maximum acceleration, the maximum deceleration and the maximum speed are not exceeded. The problem of reachability check and correction of starting speed and ending speed under constraint of a given trajectory length can be solved.
For the traditional acceleration and deceleration algorithms such as S-curve jerk discontinuity, sinusoidal curve snap discontinuity leads to flexible impact in the feed process, an acceleration & deceleration snap continuous control algorithm with asymmetric seven-segment versine curve is proposed in this paper. Considering the optimal mechanical performance of the system, by analyzing the maximum acceleration, maximum deceleration and maximum speed accessibility, 17 types of speed curves are planned; Aiming at the problem that the length of a given trajectory segment is smaller than the shortest trajectory segment length required for the system to move from the starting velocity to the ending velocity, a method for verifying the reachability of the starting velocity and the ending velocity based on the length constraint of the given trajectory segment is proposed. Meanwhile, the Shengjin formula is used to correct the starting speed and the ending speed. The self-developed multi-axis motion controller verifies the proposed all-type asymmetric seven-segment versine curve acceleration & deceleration snap continuous control algorithm. The experimental results show that the algorithm can plan 17 types of speed curves under the condition that the snap is continuous to improve system flexibility and the maximum acceleration, the maximum deceleration and the maximum speed are not exceeded. The problem of reachability check and correction of starting speed and ending speed under constraint of a given trajectory length can be solved.
2019, 38(12): 1904-1909.
doi: 10.13433/j.cnki.1003-8728.20190224
Abstract:
In order to study influence of vibration mode and the amplitude of active magnetic suspension spindle in different speed ranges on the impact process and the mechanism of workpiece machining precision, based on the rotor dynamics, electromagnetism and metal cutting theories, the finite element method is employed to analyze theoretically and interpret quantitatively a series of physical phenomena in the process of cutting for magnetic levitation bearing spindle system. The results show that the vibration mode of the system is an important factor affecting the quality of system operation and processing. The optimal cutting speed of the spindle is determined by the vibration mode of the spindle, the shape and position accuracy of the workpiece and the dynamic response of the system under load excitation. The actual form and position accuracy of the workpiece is determined by the maximum amplitude of unidirectional vibration response of the system under load excitation.
In order to study influence of vibration mode and the amplitude of active magnetic suspension spindle in different speed ranges on the impact process and the mechanism of workpiece machining precision, based on the rotor dynamics, electromagnetism and metal cutting theories, the finite element method is employed to analyze theoretically and interpret quantitatively a series of physical phenomena in the process of cutting for magnetic levitation bearing spindle system. The results show that the vibration mode of the system is an important factor affecting the quality of system operation and processing. The optimal cutting speed of the spindle is determined by the vibration mode of the spindle, the shape and position accuracy of the workpiece and the dynamic response of the system under load excitation. The actual form and position accuracy of the workpiece is determined by the maximum amplitude of unidirectional vibration response of the system under load excitation.
2019, 38(12): 1910-1920.
doi: 10.13433/j.cnki.1003-8728.20190045
Abstract:
The compound planetary gear train is widely used in large-scale weapon equipment and power equipment. It is the core component of transmission gear shifting in armored vehicles, helicopters and wind turbines. It has many parts, multiple degrees of freedom and contains multistage planetary rows. The high-speed and heavy-duty operating environment often causes wear, fatigue cracks, broken teeth and other critical parts of the planetary gear train's sun gear and planetary gears, which reduce the safety and reliability of the equipment. The research on fault diagnosis of planetary gear trains is of great significance to reduce the maintenance cost, maximize the efficiency of use and improve the operational reliability. The vibration signal is usually used for diagnosis of typical fault on the planetary gear train. Because the vibration signal of the planetary gearbox has the characteristics of strong noise, frequent frequency components and complex amplitude-frequency modulation, it is extremely difficult to diagnose faults. The paper summarizes the structural characteristics of compound planetary gear trains and the difficulties in fault diagnosis. The research status of compound planetary gear systems fault diagnosis are expounded from the aspects of dynamic analysis, signal de-noising, multi-component signal demodulation and multi-information fusion, and the important and difficult problems existing in this research field are put forward.
The compound planetary gear train is widely used in large-scale weapon equipment and power equipment. It is the core component of transmission gear shifting in armored vehicles, helicopters and wind turbines. It has many parts, multiple degrees of freedom and contains multistage planetary rows. The high-speed and heavy-duty operating environment often causes wear, fatigue cracks, broken teeth and other critical parts of the planetary gear train's sun gear and planetary gears, which reduce the safety and reliability of the equipment. The research on fault diagnosis of planetary gear trains is of great significance to reduce the maintenance cost, maximize the efficiency of use and improve the operational reliability. The vibration signal is usually used for diagnosis of typical fault on the planetary gear train. Because the vibration signal of the planetary gearbox has the characteristics of strong noise, frequent frequency components and complex amplitude-frequency modulation, it is extremely difficult to diagnose faults. The paper summarizes the structural characteristics of compound planetary gear trains and the difficulties in fault diagnosis. The research status of compound planetary gear systems fault diagnosis are expounded from the aspects of dynamic analysis, signal de-noising, multi-component signal demodulation and multi-information fusion, and the important and difficult problems existing in this research field are put forward.
2019, 38(12): 1921-1927.
doi: 10.13433/j.cnki.1003-8728.20190072
Abstract:
As it is difficult to obtain the reasonable control parameters of linear motor feed servo system by using the traditional methods, the improved adaptive genetic algorithm was proposed to optimize these five control parameters of the linear motor servo system simultaneously. The control principle of the linear motor feed system was analyzed, and the real number coding was adopted to encode the control parameters and generate the population. According to the control requirements, the fitness function composed of the error integral term, the overshoot punish term and the stability time term was determined, and the algorithm was improved by using the nonlinear adaptive crossover rate and mutation rate to accelerate the convergence speed of genetic algorithm and avoid plunging into local convergence. The simulation results show that the stability time of the improved adaptive genetic algorithm is 4.1 ms better than 39ms of the "three-loop parameter setting method" and 5.9ms of the traditional genetic algorithm under the condition of ensuring the system without overshoot. The time required to reach the steady state of the system is reduced by 89.4% comparing with the "three-loop parameter setting method". The average relative following error of the sine signal after the improved adaptive genetic algorithm is 24.70%, which is better than 51.02% of the "three-loop parameter setting method" and 24.77% of the traditional genetic algorithm. Therefore, the improved adaptive genetic algorithm is superior to the "three-loop parameter setting method" and traditional genetic algorithm in the synchronous optimization of multi-control parameters of linear motor servo system.
As it is difficult to obtain the reasonable control parameters of linear motor feed servo system by using the traditional methods, the improved adaptive genetic algorithm was proposed to optimize these five control parameters of the linear motor servo system simultaneously. The control principle of the linear motor feed system was analyzed, and the real number coding was adopted to encode the control parameters and generate the population. According to the control requirements, the fitness function composed of the error integral term, the overshoot punish term and the stability time term was determined, and the algorithm was improved by using the nonlinear adaptive crossover rate and mutation rate to accelerate the convergence speed of genetic algorithm and avoid plunging into local convergence. The simulation results show that the stability time of the improved adaptive genetic algorithm is 4.1 ms better than 39ms of the "three-loop parameter setting method" and 5.9ms of the traditional genetic algorithm under the condition of ensuring the system without overshoot. The time required to reach the steady state of the system is reduced by 89.4% comparing with the "three-loop parameter setting method". The average relative following error of the sine signal after the improved adaptive genetic algorithm is 24.70%, which is better than 51.02% of the "three-loop parameter setting method" and 24.77% of the traditional genetic algorithm. Therefore, the improved adaptive genetic algorithm is superior to the "three-loop parameter setting method" and traditional genetic algorithm in the synchronous optimization of multi-control parameters of linear motor servo system.
2019, 38(12): 1928-1936.
doi: 10.13433/j.cnki.1003-8728.20190057
Abstract:
To provide parameters for developing ultra-precision equipment, we establish the gas film model of a static thrust gas bearing in double-row hole. Then we simulate the model with the Fluent software to verify its correctness. We find out the influence law of structural parameters on the bearing capacity and stiffness of the thrust gas bearing. Finally we optimize the parameters. The simulation results show that when 0.01 mm < h < 0.01 mm, the bearing capacity and stiffness of an equal-pressure cavity are greater than those of a pressure cavity. The bigger the d, the greater the bearing capacity, the smaller the maximum stiffness. When 0.1 mm < h2 < 1.3 mm, there is no influence on the bearing capacity and stiffness of the thrust gas bearing; when h < 0.018 mm and d1 is larger, the greater the bearing capacity and stiffness of the thrust gas bearing. Its bearing capacity is the largest when h and h1 are all in phase and when the values of d1 and d are the largest.
To provide parameters for developing ultra-precision equipment, we establish the gas film model of a static thrust gas bearing in double-row hole. Then we simulate the model with the Fluent software to verify its correctness. We find out the influence law of structural parameters on the bearing capacity and stiffness of the thrust gas bearing. Finally we optimize the parameters. The simulation results show that when 0.01 mm < h < 0.01 mm, the bearing capacity and stiffness of an equal-pressure cavity are greater than those of a pressure cavity. The bigger the d, the greater the bearing capacity, the smaller the maximum stiffness. When 0.1 mm < h2 < 1.3 mm, there is no influence on the bearing capacity and stiffness of the thrust gas bearing; when h < 0.018 mm and d1 is larger, the greater the bearing capacity and stiffness of the thrust gas bearing. Its bearing capacity is the largest when h and h1 are all in phase and when the values of d1 and d are the largest.
2019, 38(12): 1937-1943.
doi: 10.13433/j.cnki.1003-8728.20190075
Abstract:
In order to achieve large stroke and high resolution positioning, the new configuration of the linear motor of the piezoelectric looper is designed by using the driven structure. Firstly, the clamping mechanism is designed with inclined wedge mechanism and disc shaped elastic yellow. The driving mechanism is designed based on flexible structure. Secondly, the static and dynamic characteristics of clamping mechanism and driving mechanism are simulated by using the finite element analysis software ANSYS. Finally, an experimental system was built to test the displacement, speed and resolution of the motor. The results show that:under the driving voltage of 50 Hz, the motor's motion speed is 59.1 m/s, the resolution of motor output displacement is 24 nm.
In order to achieve large stroke and high resolution positioning, the new configuration of the linear motor of the piezoelectric looper is designed by using the driven structure. Firstly, the clamping mechanism is designed with inclined wedge mechanism and disc shaped elastic yellow. The driving mechanism is designed based on flexible structure. Secondly, the static and dynamic characteristics of clamping mechanism and driving mechanism are simulated by using the finite element analysis software ANSYS. Finally, an experimental system was built to test the displacement, speed and resolution of the motor. The results show that:under the driving voltage of 50 Hz, the motor's motion speed is 59.1 m/s, the resolution of motor output displacement is 24 nm.
2019, 38(12): 1944-1953.
doi: 10.13433/j.cnki.1003-8728.20190079
Abstract:
After a tire burst, the vehicle may roll, rollover or drift to cause dangerous conditions, which seriously threaten the driving safety. In order to guarantee the vehicle stability and improve its robustness and adaptability after the tire blowout, a fuzzy sliding mode control algorithm is proposed on the basis of the current tire-burst control algorithm. The tire burst model is built by using UniTire model, and the vehicle model is built by using Carsim software. A fuzzy sliding mode controller is designed for nonlinear control of yaw moment. Different braking pressures are applied to each wheel to ensure the stable operation of the vehicle after the tire blowout according to the traditional electronic stability control theory. In order to verify the algorithm, the tire burst simulation was done under the straight and curved working conditions by using Carsim software and Simulink model. The results show that, after a tire blowout, the designed controller can control the vehicle stability effectively, and the yaw rate, sideslip angle, lateral acceleration and lateral displacement are reduced obviously.
After a tire burst, the vehicle may roll, rollover or drift to cause dangerous conditions, which seriously threaten the driving safety. In order to guarantee the vehicle stability and improve its robustness and adaptability after the tire blowout, a fuzzy sliding mode control algorithm is proposed on the basis of the current tire-burst control algorithm. The tire burst model is built by using UniTire model, and the vehicle model is built by using Carsim software. A fuzzy sliding mode controller is designed for nonlinear control of yaw moment. Different braking pressures are applied to each wheel to ensure the stable operation of the vehicle after the tire blowout according to the traditional electronic stability control theory. In order to verify the algorithm, the tire burst simulation was done under the straight and curved working conditions by using Carsim software and Simulink model. The results show that, after a tire blowout, the designed controller can control the vehicle stability effectively, and the yaw rate, sideslip angle, lateral acceleration and lateral displacement are reduced obviously.
2019, 38(12): 1954-1959.
doi: 10.13433/j.cnki.1003-8728.20190280
Abstract:
In order to clarify the variation rules of acoustic emission signals in the tensile damage process, steel Q235 samples were selected to conduct axial tension and acoustic emission signals were collected stably and continuously. Through the wavelet packet decomposition and reconstruction, the wavelet packet energy spectrum of the acoustic emission signal and the singularity index characteristics of signal amplitude were extracted. The results show that the signal energy is concentrated in the low frequency band, and the energy ratio of each frequency band in the low frequency band decreases with the increasing of frequency band, while the opposite situation will occur in the high frequency band. As the damage degree increases, the ratio of high-frequency energy to total energy decreases, the ratio of low-frequency energy to total energy increases, and the singularity index decreases. When the stretching rate increases, the ratio of high-frequency energy to total energy decreases, while the ratio of low-frequency energy to total energy and the singularity index increase. Finally, combining with the tensile fracture, macro and microscopic features were analyzed.
In order to clarify the variation rules of acoustic emission signals in the tensile damage process, steel Q235 samples were selected to conduct axial tension and acoustic emission signals were collected stably and continuously. Through the wavelet packet decomposition and reconstruction, the wavelet packet energy spectrum of the acoustic emission signal and the singularity index characteristics of signal amplitude were extracted. The results show that the signal energy is concentrated in the low frequency band, and the energy ratio of each frequency band in the low frequency band decreases with the increasing of frequency band, while the opposite situation will occur in the high frequency band. As the damage degree increases, the ratio of high-frequency energy to total energy decreases, the ratio of low-frequency energy to total energy increases, and the singularity index decreases. When the stretching rate increases, the ratio of high-frequency energy to total energy decreases, while the ratio of low-frequency energy to total energy and the singularity index increase. Finally, combining with the tensile fracture, macro and microscopic features were analyzed.
2019, 38(12): 1960-1965.
doi: 10.13433/j.cnki.1003-8728.20190222
Abstract:
The main causes of surface material damage of marine equipment are abrasion, cavitation and corrosion and their interaction. To quantify the wear degree of the surface is of the great significance for designing the materials and structures of marine equipment. The test rig of the interactive wear for abrasion, cavitation and corrosion is an effective tool. Based on the interaction of the abrasion and cavitation, the comprehensive test rig of abrasion, cavitation and electrochemical corrosion is optimized by the numerical comparison of flow field. The test of interactive wear are completed for different materials when high-speed fluid impacted on the working surface of ships in the artificial seawater. The results show that the weight loss of the interaction of abrasion, cavitation and electrochemical corrosion for the same metal material is greater than that of the interaction of abrasion, cavitation and natural corrosion. The corrosion wear of high-strength ductile metal material is more serious, and the wear degree of the interaction of abrasion, cavitation and natural corrosion is greater than that of low-strength ductile metals.
The main causes of surface material damage of marine equipment are abrasion, cavitation and corrosion and their interaction. To quantify the wear degree of the surface is of the great significance for designing the materials and structures of marine equipment. The test rig of the interactive wear for abrasion, cavitation and corrosion is an effective tool. Based on the interaction of the abrasion and cavitation, the comprehensive test rig of abrasion, cavitation and electrochemical corrosion is optimized by the numerical comparison of flow field. The test of interactive wear are completed for different materials when high-speed fluid impacted on the working surface of ships in the artificial seawater. The results show that the weight loss of the interaction of abrasion, cavitation and electrochemical corrosion for the same metal material is greater than that of the interaction of abrasion, cavitation and natural corrosion. The corrosion wear of high-strength ductile metal material is more serious, and the wear degree of the interaction of abrasion, cavitation and natural corrosion is greater than that of low-strength ductile metals.
2019, 38(12): 1966-1974.
doi: 10.13433/j.cnki.1003-8728.20190070
Abstract:
A rotor wheelbase has an important influence on the downwash flow aggregation. According to the downwash flow formation, the effects of downwash flow and vortex compression and downwash aggregation were analyzed. The realizable k-ε turbulence model and sliding mesh were used, and the simulation model was verified. The rotor wheelbase's downwash flow aggregation characteristics and wind resistance ability below different aggregation degrees were analyzed. The simulation results show that the near-ground vortex compression between rotor gaps is crucial to the downwash flow aggregation phenomenon, which makes the downwash flow velocity distribution more uniform and increases the flow stability. When the rotor wheelbase is hovering and the wheelbase-to-diameter ratio is 1.1 to 1.4, the higher the wheelbase-to-diameter ratio, the lower the flow aggregation degree. The downwash flow aggregation phenomenon is useful for resisting the interference of pre-flight flow, however, when the forward flight speed exceeds a certain critical value, the downward flow pattern is destroyed, and the resistance of the downward flow aggregation phenomenon to wind is weakened.
A rotor wheelbase has an important influence on the downwash flow aggregation. According to the downwash flow formation, the effects of downwash flow and vortex compression and downwash aggregation were analyzed. The realizable k-ε turbulence model and sliding mesh were used, and the simulation model was verified. The rotor wheelbase's downwash flow aggregation characteristics and wind resistance ability below different aggregation degrees were analyzed. The simulation results show that the near-ground vortex compression between rotor gaps is crucial to the downwash flow aggregation phenomenon, which makes the downwash flow velocity distribution more uniform and increases the flow stability. When the rotor wheelbase is hovering and the wheelbase-to-diameter ratio is 1.1 to 1.4, the higher the wheelbase-to-diameter ratio, the lower the flow aggregation degree. The downwash flow aggregation phenomenon is useful for resisting the interference of pre-flight flow, however, when the forward flight speed exceeds a certain critical value, the downward flow pattern is destroyed, and the resistance of the downward flow aggregation phenomenon to wind is weakened.
