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RSS2018 Vol. 37, No. 6
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2018, 37(6): 821-827.
doi: 10.13433/j.cnki.1003-8728.2018.0601
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Abstract:
In order to obtain the best pulverization effect, a parameterized simulation model for vertical vibration mill was built in this paper. Latin hypercube method was used to generate sample data, the response surface approximation model (RSM) was established and its accuracy satisfies the accepted level. A multi-objective optimization design on RSM was carried out by multi-optimization genetic algorithm NSGA-Ⅱ, and its objectives were to maximize vibration intensity and impact force and to minimize the volume of mill medium. The Pareto optimal solution set and Pareto frontier were obtained, which provides guidance for mechanical design and parameter selection of the vertical vibration mill. Finally, an optimization example of vertical vibration mill was given to show its effectiveness. Approximate model method can improve optimization efficiency and it also provides a method for design and optimization of the similar complicated models.
In order to obtain the best pulverization effect, a parameterized simulation model for vertical vibration mill was built in this paper. Latin hypercube method was used to generate sample data, the response surface approximation model (RSM) was established and its accuracy satisfies the accepted level. A multi-objective optimization design on RSM was carried out by multi-optimization genetic algorithm NSGA-Ⅱ, and its objectives were to maximize vibration intensity and impact force and to minimize the volume of mill medium. The Pareto optimal solution set and Pareto frontier were obtained, which provides guidance for mechanical design and parameter selection of the vertical vibration mill. Finally, an optimization example of vertical vibration mill was given to show its effectiveness. Approximate model method can improve optimization efficiency and it also provides a method for design and optimization of the similar complicated models.
2018, 37(6): 828-833.
doi: 10.13433/j.cnki.1003-8728.2018.0602
Abstract:
In view of the difficulty in diesel engine vibration acceleration signal feature extraction, a kind of vibration signal time-frequency characteristics extraction method, which joined the local texture feature information of nonnegative matrix decomposition method, is put forward. Firstly, decompose the diesel engine cylinder head vibration acceleration signal by the matching pursuit (MP) algorithm, and obtain the 2-d time-frequency distribution diagrams by superimposing the decomposed signal Wigner-Ville distribution. Then, use NMF to calculate the corresponding low dimensional time-frequency characteristic parameters of the time-frequency distribution image. Next, introduce local binary pattern (LBP) operator pair recoding, frequency of the image gray level matrix to improve the effect of feature extraction of NMF. By the analysis of four different states of diesel engine vibration acceleration signal, which is corresponding to the valve clearance is normal, the valve clearance is too small or too big, and valve leakage, the results showed that the combination of LBP and NMF can effectively express the time-frequency characteristics of diesel engine cylinder head vibration acceleration signal, which can be used for the diagnosis of diesel engine valve fault accurately.
In view of the difficulty in diesel engine vibration acceleration signal feature extraction, a kind of vibration signal time-frequency characteristics extraction method, which joined the local texture feature information of nonnegative matrix decomposition method, is put forward. Firstly, decompose the diesel engine cylinder head vibration acceleration signal by the matching pursuit (MP) algorithm, and obtain the 2-d time-frequency distribution diagrams by superimposing the decomposed signal Wigner-Ville distribution. Then, use NMF to calculate the corresponding low dimensional time-frequency characteristic parameters of the time-frequency distribution image. Next, introduce local binary pattern (LBP) operator pair recoding, frequency of the image gray level matrix to improve the effect of feature extraction of NMF. By the analysis of four different states of diesel engine vibration acceleration signal, which is corresponding to the valve clearance is normal, the valve clearance is too small or too big, and valve leakage, the results showed that the combination of LBP and NMF can effectively express the time-frequency characteristics of diesel engine cylinder head vibration acceleration signal, which can be used for the diagnosis of diesel engine valve fault accurately.
2018, 37(6): 834-838.
doi: 10.13433/j.cnki.1003-8728.2018.0603
Abstract:
Aiming at the problems of shock and noise existing in the transforming moment between high and low pressure areas, a novel triangular uniform-section damping groove is proposed. First, The mathematical modeling of flow characteristic about the damping grooves is established and orifice area is simulated in different stages based on structural characteristic of rotating-sleeve distributing-flow system. Then, flow pulsation, pump chamber pressure and velocity vector are analyzed in sight of numerical analysis and visualization research with full flow field, respectively. The results show that the triangular damping groove flow regime of flow flied is turbulent flow. In addition, triangular damping groove has serious flow pulsation, large flow velocity and disordered flow direction resulting in flow impact and backflow, but stable pressure caused by flow backward is beneficial to pressure pulsation and pressure flied.
Aiming at the problems of shock and noise existing in the transforming moment between high and low pressure areas, a novel triangular uniform-section damping groove is proposed. First, The mathematical modeling of flow characteristic about the damping grooves is established and orifice area is simulated in different stages based on structural characteristic of rotating-sleeve distributing-flow system. Then, flow pulsation, pump chamber pressure and velocity vector are analyzed in sight of numerical analysis and visualization research with full flow field, respectively. The results show that the triangular damping groove flow regime of flow flied is turbulent flow. In addition, triangular damping groove has serious flow pulsation, large flow velocity and disordered flow direction resulting in flow impact and backflow, but stable pressure caused by flow backward is beneficial to pressure pulsation and pressure flied.
2018, 37(6): 839-847.
doi: 10.13433/j.cnki.1003-8728.2018.0604
Abstract:
In the installation process of five-axis gantry machining center, the machine bed's deformation, resulting from pre-loading force in anchor bolts installation, will affect the geometric accuracy of gantry machining center, and the stress distribution characteristics will affect the gantry machining center's accuracy maintenance. Based on the analysis of the bolt pre-loading model, the step pre-loading method of the anchor bolts is proposed, and the method is based on the minimum deformation installation error and the uniform pressure distribution of the bolts. And how these factors, including pre-loading order, pre-loading steps' number and pre-loading steps' ratio, influence the geometrical accuracy of rail mounting surface, uniformity of the pressure distribution and precision retention of the gantry machining center are analyzed quantitatively. The simulation results show that the present method can realize fast and effective installation of the anchor bolts in five-axis gantry machining center, and it can also solve the problem that the traditional experience method's installation efficiency is low and its accuracy is difficult to guarantee.
In the installation process of five-axis gantry machining center, the machine bed's deformation, resulting from pre-loading force in anchor bolts installation, will affect the geometric accuracy of gantry machining center, and the stress distribution characteristics will affect the gantry machining center's accuracy maintenance. Based on the analysis of the bolt pre-loading model, the step pre-loading method of the anchor bolts is proposed, and the method is based on the minimum deformation installation error and the uniform pressure distribution of the bolts. And how these factors, including pre-loading order, pre-loading steps' number and pre-loading steps' ratio, influence the geometrical accuracy of rail mounting surface, uniformity of the pressure distribution and precision retention of the gantry machining center are analyzed quantitatively. The simulation results show that the present method can realize fast and effective installation of the anchor bolts in five-axis gantry machining center, and it can also solve the problem that the traditional experience method's installation efficiency is low and its accuracy is difficult to guarantee.
2018, 37(6): 848-853.
doi: 10.13433/j.cnki.1003-8728.2018.0605
Abstract:
This paper studies the Fourier series expansion of the connecting rod angle of standard position base hing four bar mechanism and general position extension hing four bar linkage mechanism. It is found that the harmonic characteristic parameters normalized of connecting rod curve have nothing to do with the length l0 and the angle α of extension of the connecting rod, but relate to the length of foundation rod, l1、l2、l3 and l4. Therefore, optimization target is the minimum amplitude difference between the desired trajectory and the E point trajectory of the connecting rod. It is only necessary to optimal design the four parameters of l1、l2、l3 and l4, and the other 6 parameters are calculated further. All calculations are performed automatically by the Matlab program. This method can rapidly and accurately realize the four bar scale design of any desired trajectory, and it is not limited by the number of discrete points and initial values, which reduces the dimension of optimization and improves the efficiency of calculation compared with the traditional optimization design of the direct method and the electron atlas indirect method. And the coincidence degree of track is extremely high. It provides an ideal design method for the trajectory synthesis of planar linkage mechanism.
This paper studies the Fourier series expansion of the connecting rod angle of standard position base hing four bar mechanism and general position extension hing four bar linkage mechanism. It is found that the harmonic characteristic parameters normalized of connecting rod curve have nothing to do with the length l0 and the angle α of extension of the connecting rod, but relate to the length of foundation rod, l1、l2、l3 and l4. Therefore, optimization target is the minimum amplitude difference between the desired trajectory and the E point trajectory of the connecting rod. It is only necessary to optimal design the four parameters of l1、l2、l3 and l4, and the other 6 parameters are calculated further. All calculations are performed automatically by the Matlab program. This method can rapidly and accurately realize the four bar scale design of any desired trajectory, and it is not limited by the number of discrete points and initial values, which reduces the dimension of optimization and improves the efficiency of calculation compared with the traditional optimization design of the direct method and the electron atlas indirect method. And the coincidence degree of track is extremely high. It provides an ideal design method for the trajectory synthesis of planar linkage mechanism.
2018, 37(6): 854-858.
doi: 10.13433/j.cnki.1003-8728.2018.0606
Abstract:
Planar parallel mechanism is widely used in the field of engineering because of its excellent performance. In order to enhance mechanism movement precision, the real time control method of 3-RRR planar parallel mechanism is presented based on the fuzzy-PID control algorithm. The fuzzy-PID control system model for 3-RRR planar parallel mechanism is established by analyzing the fuzzy-PID control theory. The experimental setup of mechanism for control is built. And the real time control of mechanism's movement precision is studied through experiment. The results show that the maximum of mechanism angle displacement error is 2.1° when 3-RRR planar parallel mechanism is bring to bear fuzzy-PID control. And the decrease extent of error reaches to 53% upwards. The present fuzzy-PID control system can be used tothe real time control of mechanism's movement precision. And it can decrease the error of mechanism angle displacement efficiency. The present method is of simple arithmetic and real time characteristics.
Planar parallel mechanism is widely used in the field of engineering because of its excellent performance. In order to enhance mechanism movement precision, the real time control method of 3-RRR planar parallel mechanism is presented based on the fuzzy-PID control algorithm. The fuzzy-PID control system model for 3-RRR planar parallel mechanism is established by analyzing the fuzzy-PID control theory. The experimental setup of mechanism for control is built. And the real time control of mechanism's movement precision is studied through experiment. The results show that the maximum of mechanism angle displacement error is 2.1° when 3-RRR planar parallel mechanism is bring to bear fuzzy-PID control. And the decrease extent of error reaches to 53% upwards. The present fuzzy-PID control system can be used tothe real time control of mechanism's movement precision. And it can decrease the error of mechanism angle displacement efficiency. The present method is of simple arithmetic and real time characteristics.
2018, 37(6): 859-866.
doi: 10.13433/j.cnki.1003-8728.2018.0607
Abstract:
By means of fractal contacting theory, in the case of consideration of elastic contacting characteristics between two plates of the rod fastening composite special rotor, bending coupling model and twist coupling model were established. Furthermore, the dynamic model of the rod fastening composite special rotor-bearing system was established by Lumped Parameter Method. By impact test, the natural frequencies of the rod fastening composite special rotor in free state were measured, which are used to verify the model. By means of numerical simulation, the natural frequencies of bending and twisting vibration of the system were researched. It was found that fractal contacting theory was appropriate to solve the elastic contacting problem. The natural frequencies were varied with normal load between contacting surfaces. The natural frequencies of the rod fastening composite special rotor are less than the solid rotor with same size and structure. Higher order natural frequencies are seriously influenced by normal loads. Lower natural frequencies of the rod fastening composite special rotor supported by the hydraulic bearing are hardly influenced by normal loads relatively.
By means of fractal contacting theory, in the case of consideration of elastic contacting characteristics between two plates of the rod fastening composite special rotor, bending coupling model and twist coupling model were established. Furthermore, the dynamic model of the rod fastening composite special rotor-bearing system was established by Lumped Parameter Method. By impact test, the natural frequencies of the rod fastening composite special rotor in free state were measured, which are used to verify the model. By means of numerical simulation, the natural frequencies of bending and twisting vibration of the system were researched. It was found that fractal contacting theory was appropriate to solve the elastic contacting problem. The natural frequencies were varied with normal load between contacting surfaces. The natural frequencies of the rod fastening composite special rotor are less than the solid rotor with same size and structure. Higher order natural frequencies are seriously influenced by normal loads. Lower natural frequencies of the rod fastening composite special rotor supported by the hydraulic bearing are hardly influenced by normal loads relatively.
2018, 37(6): 867-872.
doi: 10.13433/j.cnki.1003-8728.2018.0608
Abstract:
The toroidal electromechanical drive is a kind of space mechanical and electrical drive with the combination of electromagnetic drive and retarding mechanism. It has a good application prospect in the field of robotics and aerospace. Based on the analysis of the structure characteristics and driving mechanism, the output torque of the single planet tooth is analytically calculated. Based on the analysis of the electromagnetic meshing relation between the internal stator and external stator and the planetary gear, the influence of the structural parameters such as the number of planet tooth and the worm wrap angle on the output torque is discussed. The analytical relationship among the output torque of multi tooth engagement is deduced. The fluctuation of the output torque is analyzed and calculated.
The toroidal electromechanical drive is a kind of space mechanical and electrical drive with the combination of electromagnetic drive and retarding mechanism. It has a good application prospect in the field of robotics and aerospace. Based on the analysis of the structure characteristics and driving mechanism, the output torque of the single planet tooth is analytically calculated. Based on the analysis of the electromagnetic meshing relation between the internal stator and external stator and the planetary gear, the influence of the structural parameters such as the number of planet tooth and the worm wrap angle on the output torque is discussed. The analytical relationship among the output torque of multi tooth engagement is deduced. The fluctuation of the output torque is analyzed and calculated.
2018, 37(6): 873-878.
doi: 10.13433/j.cnki.1003-8728.2018.0609
Abstract:
A fault diagnosis method based on 3D axis orbit and manifold learning is proposed. The horizontal, vertical and axial displacement signals of rotor system are extracted and the ensemble empirical mode decomposition (EEMD) is used to denoise the original signal. The denoised signals are combined into 3D axis orbit. Locally tangent space arrangement (LTSA) manifold learning algorithm is used to reduce the dimension of the 3D axis orbit, thus to obtain its 2D manifold diagram. Compared with the 3D axis orbit, the 2D manifold diagram is more convenient for analysis and recognition, and the spatial topological relation of the data points of the 3D axis orbit is retained. The method is applied to the test, 3D axis orbit and 2D manifold diagram of the normal, misalignment, oil whirl and oil whip in the rotor system are obtained. Compared with the 3D axis orbit, the 2D manifold diagram has simple and intuitive feature differentiation.
A fault diagnosis method based on 3D axis orbit and manifold learning is proposed. The horizontal, vertical and axial displacement signals of rotor system are extracted and the ensemble empirical mode decomposition (EEMD) is used to denoise the original signal. The denoised signals are combined into 3D axis orbit. Locally tangent space arrangement (LTSA) manifold learning algorithm is used to reduce the dimension of the 3D axis orbit, thus to obtain its 2D manifold diagram. Compared with the 3D axis orbit, the 2D manifold diagram is more convenient for analysis and recognition, and the spatial topological relation of the data points of the 3D axis orbit is retained. The method is applied to the test, 3D axis orbit and 2D manifold diagram of the normal, misalignment, oil whirl and oil whip in the rotor system are obtained. Compared with the 3D axis orbit, the 2D manifold diagram has simple and intuitive feature differentiation.
2018, 37(6): 879-883.
doi: 10.13433/j.cnki.1003-8728.2018.0067
Abstract:
In order to realize the on-machine measurement (OMM) of lead errors of large-scale gear with high efficiency and high precision, an integrated OMM method based on scanning probe is proposed. The movement function model of machine tool is established in accordance with the multi-body system theory. According to the contact relationship between the probe and the measured feature of the tooth surface, the measuring model of the involute spiral surface is built by the homogeneous coordinate transformation method. Under the constraint condition of motion generation for tooth surface the functional equations between the measured feature of the tooth surface and the servo motion of the machine tool is deduced, which are solved to obtain the motion quantity of each servo axis to implement measurement path. To describe the finely detailed features of tooth curve precisely, the noise signal of the detected data such as vibration disturbance of machine tool servo system, surface roughness of measured gear, etc. are eliminated using wavelet transfer method. The OMM experiment of the tooth deviation of helical gear is carried out on an YK73 series CNC gear forming grinding machine. The experimental results show that the measurement results are in good agreement with the measurement results of the gear metering center, and the feasibility, effectiveness and high accuracy of the presented method is proved.
In order to realize the on-machine measurement (OMM) of lead errors of large-scale gear with high efficiency and high precision, an integrated OMM method based on scanning probe is proposed. The movement function model of machine tool is established in accordance with the multi-body system theory. According to the contact relationship between the probe and the measured feature of the tooth surface, the measuring model of the involute spiral surface is built by the homogeneous coordinate transformation method. Under the constraint condition of motion generation for tooth surface the functional equations between the measured feature of the tooth surface and the servo motion of the machine tool is deduced, which are solved to obtain the motion quantity of each servo axis to implement measurement path. To describe the finely detailed features of tooth curve precisely, the noise signal of the detected data such as vibration disturbance of machine tool servo system, surface roughness of measured gear, etc. are eliminated using wavelet transfer method. The OMM experiment of the tooth deviation of helical gear is carried out on an YK73 series CNC gear forming grinding machine. The experimental results show that the measurement results are in good agreement with the measurement results of the gear metering center, and the feasibility, effectiveness and high accuracy of the presented method is proved.
2018, 37(6): 884-890.
doi: 10.13433/j.cnki.1003-8728.2018.0610
Abstract:
To solve rotation error separation of high-precision lathe spindle, the multi-step error separation method was put forward. According to the errors' characteristics, each step is set to eliminate the single kind of error. Finally the precision rotation error is obtained in the final step of error separation. With the standard sphere fixed to precise lathe spindle as the direct measurement object, a measuring platform based on three spatially vertical electrical vortex sensors is designed to measure the radial jerk value and axial displacement of high-precision standard sphere synchronously. Based on the two radial vertical sensors, the pretreatment is carried out to separate the average eccentricity of 13.1 microns. By comparing the axial displacement and the radial jerk value, the influence of the axial displacement on the radial jerk value is theoretically explored. After preprocessing the collected data, the mathematical statistics method is used to finally separate errors. Through least squares approximations to assess the spindle rotation precision, it is concluded that the roundness error of the standard sphere is 2.3 microns, and in the actual speed range of 0~700 r/min, the average rotation precision of the spindle is 1.8 microns.
To solve rotation error separation of high-precision lathe spindle, the multi-step error separation method was put forward. According to the errors' characteristics, each step is set to eliminate the single kind of error. Finally the precision rotation error is obtained in the final step of error separation. With the standard sphere fixed to precise lathe spindle as the direct measurement object, a measuring platform based on three spatially vertical electrical vortex sensors is designed to measure the radial jerk value and axial displacement of high-precision standard sphere synchronously. Based on the two radial vertical sensors, the pretreatment is carried out to separate the average eccentricity of 13.1 microns. By comparing the axial displacement and the radial jerk value, the influence of the axial displacement on the radial jerk value is theoretically explored. After preprocessing the collected data, the mathematical statistics method is used to finally separate errors. Through least squares approximations to assess the spindle rotation precision, it is concluded that the roundness error of the standard sphere is 2.3 microns, and in the actual speed range of 0~700 r/min, the average rotation precision of the spindle is 1.8 microns.
2018, 37(6): 891-895.
doi: 10.13433/j.cnki.1003-8728.2018.0611
Abstract:
Due to the conflict between the accuracy of the curve fitting and the smoothness, which most of time sacrifices the quality of one aspect of the curve fitting to meet the requirement for another when the curve fitting is conducted, the curve fitting method based on the cubic B-spline wavelet transform is put forward. The data on original control points are processed with the wavelet transform, information on high frequency detail is removed to obtain principal information on low frequency. The new control points are used to represent the data characteristics of the original control points, thus ensuring the precision and improving the smoothness of the curve fitting and the machining accuracy. The case studies show that the curve fitting method is effective and provides a compromise method for the curve fitting between fitting precision, smoothness and machining accuracy.
Due to the conflict between the accuracy of the curve fitting and the smoothness, which most of time sacrifices the quality of one aspect of the curve fitting to meet the requirement for another when the curve fitting is conducted, the curve fitting method based on the cubic B-spline wavelet transform is put forward. The data on original control points are processed with the wavelet transform, information on high frequency detail is removed to obtain principal information on low frequency. The new control points are used to represent the data characteristics of the original control points, thus ensuring the precision and improving the smoothness of the curve fitting and the machining accuracy. The case studies show that the curve fitting method is effective and provides a compromise method for the curve fitting between fitting precision, smoothness and machining accuracy.
2018, 37(6): 896-902.
doi: 10.13433/j.cnki.1003-8728.2018.0612
Abstract:
In order to solve the manufacturing of surface texture on mechanical parts and make full use of the advantages of electrochemical machining, based on the COMSOL multiphisics software, the electrochemical machining of mask micro-dimples array simulation analysis and the electrochemical machining of surface texture on mechanical parts experience study were carried out. The diameter and depth in nano size on the surface micro-dimples array were available and the technological rule of micro-dimples machining with common DC (Direct current) processing voltage and processing time, processing impulse current frequency and duty cycle,different diameter of mask holes were carried out. The results showed that the optimal micro-dimples with surface quality is the processing time of 12 s, pulse voltage of 12 V,duty cycle of 30%,pulse frequency of 3 000 Hz, pore size of mask of 200 μm.
In order to solve the manufacturing of surface texture on mechanical parts and make full use of the advantages of electrochemical machining, based on the COMSOL multiphisics software, the electrochemical machining of mask micro-dimples array simulation analysis and the electrochemical machining of surface texture on mechanical parts experience study were carried out. The diameter and depth in nano size on the surface micro-dimples array were available and the technological rule of micro-dimples machining with common DC (Direct current) processing voltage and processing time, processing impulse current frequency and duty cycle,different diameter of mask holes were carried out. The results showed that the optimal micro-dimples with surface quality is the processing time of 12 s, pulse voltage of 12 V,duty cycle of 30%,pulse frequency of 3 000 Hz, pore size of mask of 200 μm.
2018, 37(6): 903-909.
doi: 10.13433/j.cnki.1003-8728.2018.0054
Abstract:
Some problems of coverage uniformity last for a long time in the traditional plane lapping, simulation and experiments are carried out to investigate the X-Y linkage plane lapping track, whose motion model is established. Effects of four parameters on the lapping trajectory are simulated, including initial diameter, the phase angle of initial point, speed ratio and X-Y linkage plane lapping track. Then, experiments on the plane lapping are conducted for a self-developed plane lapping machine tool. The flatness and roughness of its lapping surface are measured. The experimental results ensure the effectiveness of the lapping trajectory simulation method and show that the reasonable combination of lapping parameters is an essential factor for improving the surface quality.
Some problems of coverage uniformity last for a long time in the traditional plane lapping, simulation and experiments are carried out to investigate the X-Y linkage plane lapping track, whose motion model is established. Effects of four parameters on the lapping trajectory are simulated, including initial diameter, the phase angle of initial point, speed ratio and X-Y linkage plane lapping track. Then, experiments on the plane lapping are conducted for a self-developed plane lapping machine tool. The flatness and roughness of its lapping surface are measured. The experimental results ensure the effectiveness of the lapping trajectory simulation method and show that the reasonable combination of lapping parameters is an essential factor for improving the surface quality.
2018, 37(6): 910-914.
doi: 10.13433/j.cnki.1003-8728.2018.0613
Abstract:
Because of the synchronous control problem of a multi-axis industrial robot, a new nonlinear PD (proportion-differential) ring coupling synchronous control structure for the industrial robot is proposed, and new definition methods for position error and synchronization error are given. A multi-axis PD coupling control algorithm for the industrial robot based on the Lyapunov stability theory is presented, and the asymptotic stability of the algorithm is proved. The experimental results show that the synchronous control algorithm for the multi-axis PD ring coupling compensation of the industrial robot based on the new nonlinear PD ring coupling synchronous control structure can realize the fast convergence of position error and synchronization error for the synchronous control system and improve the synchronization performance and position tracking accuracy of the industrial robot control system.
Because of the synchronous control problem of a multi-axis industrial robot, a new nonlinear PD (proportion-differential) ring coupling synchronous control structure for the industrial robot is proposed, and new definition methods for position error and synchronization error are given. A multi-axis PD coupling control algorithm for the industrial robot based on the Lyapunov stability theory is presented, and the asymptotic stability of the algorithm is proved. The experimental results show that the synchronous control algorithm for the multi-axis PD ring coupling compensation of the industrial robot based on the new nonlinear PD ring coupling synchronous control structure can realize the fast convergence of position error and synchronization error for the synchronous control system and improve the synchronization performance and position tracking accuracy of the industrial robot control system.
Fuzzy Sliding Mode Control of Uncertainty Mechanical System with Second Order Approximation Accuracy
2018, 37(6): 915-920.
doi: 10.13433/j.cnki.1003-8728.2018.0614
Abstract:
The universal approximation of a fuzzy logic system is used to establish the unknown nonlinear function model of an uncertainty mechanical system. The fuzzy logic system based on the first-order approximation accuracy needs many fuzzy rules to ensure the certain approximation accuracy. However, the increase of the number of rules will inevitably lead to the increase of computational complexity. In this paper, a fuzzy logic system with second-order approximation accuracy is designed to approximate the unknown nonlinear part of the uncertainty mechanical system, whose trajectory tracking control is carried out with the sliding mode control. Simulation results prove that the fuzzy logic system with second-order approximation accuracy can greatly reduce the number of fuzzy rules and can approximate any nonlinear functions with high precision. Therefore, the adaptive fuzzy logic system designed with the special membership function solves the contradiction between approximation accuracy and number of fuzzy rules and provides guarantees for the high-accuracy and real-time control of the uncertainty mechanical system.
The universal approximation of a fuzzy logic system is used to establish the unknown nonlinear function model of an uncertainty mechanical system. The fuzzy logic system based on the first-order approximation accuracy needs many fuzzy rules to ensure the certain approximation accuracy. However, the increase of the number of rules will inevitably lead to the increase of computational complexity. In this paper, a fuzzy logic system with second-order approximation accuracy is designed to approximate the unknown nonlinear part of the uncertainty mechanical system, whose trajectory tracking control is carried out with the sliding mode control. Simulation results prove that the fuzzy logic system with second-order approximation accuracy can greatly reduce the number of fuzzy rules and can approximate any nonlinear functions with high precision. Therefore, the adaptive fuzzy logic system designed with the special membership function solves the contradiction between approximation accuracy and number of fuzzy rules and provides guarantees for the high-accuracy and real-time control of the uncertainty mechanical system.
2018, 37(6): 921-925.
doi: 10.13433/j.cnki.1003-8728.2018.0615
Abstract:
On-machine scanning measurement for large gear profile error on gear grinding has large amount of data and is motion-sensitive. In this regard, a data processing method is proposed, which includes identification effective data based on finding the break points through enlarging the change trend, using wavelet analysis method to extract the macroscopic shape outline and machining error analysis. Experiments for gear profile error on-machine measurement in the grinding machine showed that this method can not only more comprehensively and accurately evaluate the tooth profile error, but also can accurately represent the morphologies of tooth surface and error location, and that it has high repeatability and good stability.
On-machine scanning measurement for large gear profile error on gear grinding has large amount of data and is motion-sensitive. In this regard, a data processing method is proposed, which includes identification effective data based on finding the break points through enlarging the change trend, using wavelet analysis method to extract the macroscopic shape outline and machining error analysis. Experiments for gear profile error on-machine measurement in the grinding machine showed that this method can not only more comprehensively and accurately evaluate the tooth profile error, but also can accurately represent the morphologies of tooth surface and error location, and that it has high repeatability and good stability.
2018, 37(6): 926-929.
doi: 10.13433/j.cnki.1003-8728.2018.0616
Abstract:
In order to expand the effective frequency band of a conventional dynamic vibration absorber (DVA), a novel variable stiffness DVA with piezoelectric stack is designed. Using Euler beam theory, a piezoelectric stack element is applied to generate preload on the beam which acts as a spring element in the DVA to tune its bending stiffness. The principle of this novel DVA is presented and the equation of the bending stiffness for an Euler beam was deduced. A prototype of this variable stiffness DVA is fabricated. The dynamic behavior of the DVA under different driven voltages is validated experimentally. There results show that the natural frequency of the DVA can be shifted from 75 Hz to 71.5 Hz when the driven voltage was tuned from 0 V to 120 V.
In order to expand the effective frequency band of a conventional dynamic vibration absorber (DVA), a novel variable stiffness DVA with piezoelectric stack is designed. Using Euler beam theory, a piezoelectric stack element is applied to generate preload on the beam which acts as a spring element in the DVA to tune its bending stiffness. The principle of this novel DVA is presented and the equation of the bending stiffness for an Euler beam was deduced. A prototype of this variable stiffness DVA is fabricated. The dynamic behavior of the DVA under different driven voltages is validated experimentally. There results show that the natural frequency of the DVA can be shifted from 75 Hz to 71.5 Hz when the driven voltage was tuned from 0 V to 120 V.
2018, 37(6): 930-936.
doi: 10.13433/j.cnki.1003-8728.2018.0617
Abstract:
The relationships among of damping force F and six main parameters of magnetorheological damper (MRD) were obtained based on the Bingham constitutive model. The effects of the six parameters on the damping force F and dynamic range λ were also discussed. At the same time, a quarter vehicle suspension model with MRD was established. Based on the Bingham constitutive model, the influence of the passive damping coefficient cs of MRD on the damping effect of vehicle suspension was analyzed. Moreover, the RMS value of the percentage-based slope was put forward to evaluate the influence degree of the six parameters of MRD on the vibration attenuation effect, and the influence of damper wear on the damping effect was also obtained. The results show that the piston diameter d2 and cylinder inner diameter D have a great influence on the damping effect, and other parameters have little influence on the damping effect. It also identified that when the dynamic range λ and damping force F are all large enough, the vehicle suspension can get better damping effect.
The relationships among of damping force F and six main parameters of magnetorheological damper (MRD) were obtained based on the Bingham constitutive model. The effects of the six parameters on the damping force F and dynamic range λ were also discussed. At the same time, a quarter vehicle suspension model with MRD was established. Based on the Bingham constitutive model, the influence of the passive damping coefficient cs of MRD on the damping effect of vehicle suspension was analyzed. Moreover, the RMS value of the percentage-based slope was put forward to evaluate the influence degree of the six parameters of MRD on the vibration attenuation effect, and the influence of damper wear on the damping effect was also obtained. The results show that the piston diameter d2 and cylinder inner diameter D have a great influence on the damping effect, and other parameters have little influence on the damping effect. It also identified that when the dynamic range λ and damping force F are all large enough, the vehicle suspension can get better damping effect.
2018, 37(6): 937-940.
doi: 10.13433/j.cnki.1003-8728.2018.0618
Abstract:
Heat dissipation performance for ventilated brake disc plays an important role in improving brake performance, and ribs structure is a key factor that influence on heat dissipation performance for ventilated brake disc. In this paper, the emergency braking condition was considered, and the computational fluid dynamics (CFD) method was applied to analyzethe brake disc which had four different ribs structure, including radial rib structure (Z-type), arc rib structure (A-type) rectangular rib structure (R-type) and trapezoidal rib structure (T-type). The temperature distribution, average convective heat transfer coefficient and total heat flux were studied on the brake disc. The results showed that the A-type brake disc had the better heat dissipation performance among the four kinds of different ribs structure; comparing with the Z-type brake disc, the A-type brake disc had the more uniform temperature distribution, in which the temperature fell 7.3%, higher average convective heat transfer coefficient and total heat flux improved 32.3%. Hence, the A-type rib structure could effectively improve the heat dissipation performance for ventilated brake disc.
Heat dissipation performance for ventilated brake disc plays an important role in improving brake performance, and ribs structure is a key factor that influence on heat dissipation performance for ventilated brake disc. In this paper, the emergency braking condition was considered, and the computational fluid dynamics (CFD) method was applied to analyzethe brake disc which had four different ribs structure, including radial rib structure (Z-type), arc rib structure (A-type) rectangular rib structure (R-type) and trapezoidal rib structure (T-type). The temperature distribution, average convective heat transfer coefficient and total heat flux were studied on the brake disc. The results showed that the A-type brake disc had the better heat dissipation performance among the four kinds of different ribs structure; comparing with the Z-type brake disc, the A-type brake disc had the more uniform temperature distribution, in which the temperature fell 7.3%, higher average convective heat transfer coefficient and total heat flux improved 32.3%. Hence, the A-type rib structure could effectively improve the heat dissipation performance for ventilated brake disc.
2018, 37(6): 941-948.
Abstract:
Aiming at a simplified model of a van type truck, the model of the original truck, the model of the truck equipped with the tail drag reduction device and the top drag reduction device were numerically simulated based on computational fluid dynamics theory and method respectively. The aerodynamic characteristics such as aerodynamic drag coefficient, velocity vector distribution, pressure distribution and turbulent kinetic energy distribution of the original model and the improved model are obtained. The calculation results show that the tail drag reduction device and the top drag reduction device can improve the aerodynamic characteristics of the truck and reduce the aerodynamic drag. The top drag reduction device improves the airflow distribution between the cab and the cargo compartment, and the tail drag reduction device improves the vortex flow at the rear of the truck, so the truck drag is thus reduced.
Aiming at a simplified model of a van type truck, the model of the original truck, the model of the truck equipped with the tail drag reduction device and the top drag reduction device were numerically simulated based on computational fluid dynamics theory and method respectively. The aerodynamic characteristics such as aerodynamic drag coefficient, velocity vector distribution, pressure distribution and turbulent kinetic energy distribution of the original model and the improved model are obtained. The calculation results show that the tail drag reduction device and the top drag reduction device can improve the aerodynamic characteristics of the truck and reduce the aerodynamic drag. The top drag reduction device improves the airflow distribution between the cab and the cargo compartment, and the tail drag reduction device improves the vortex flow at the rear of the truck, so the truck drag is thus reduced.
2018, 37(6): 949-956.
doi: 10.13433/j.cnki.1003-8728.2018.0126
Abstract:
For carbon fiber bundle of plain weave C/SiC composites, the three dimensional and three phase finite element model of representative volume element (RVE) with interface is established by using the scanning electron microscope (SEM) pictures, and considering fiber arrangement and selection of appropriate interface model. The axial TRS of carbon fiber bundle is simulated by using cooling method with indirect coupling, considering the influence of temperature on the elastic constants of the components and applying appropriate periodic boundary conditions. The analysis shows that the TRS of SiC matrix increases with the decrease of the thickness of interface, and increases with the increase of the interface modulus. Introducing the one-dimensional stress distribution axis and using oscillation amplitude of stress as one condition of choosing the best parameters, it is considered that it's better to reduce the gradient of the change of TRS among the components by choosing interface with small thermal expansion coefficient.
For carbon fiber bundle of plain weave C/SiC composites, the three dimensional and three phase finite element model of representative volume element (RVE) with interface is established by using the scanning electron microscope (SEM) pictures, and considering fiber arrangement and selection of appropriate interface model. The axial TRS of carbon fiber bundle is simulated by using cooling method with indirect coupling, considering the influence of temperature on the elastic constants of the components and applying appropriate periodic boundary conditions. The analysis shows that the TRS of SiC matrix increases with the decrease of the thickness of interface, and increases with the increase of the interface modulus. Introducing the one-dimensional stress distribution axis and using oscillation amplitude of stress as one condition of choosing the best parameters, it is considered that it's better to reduce the gradient of the change of TRS among the components by choosing interface with small thermal expansion coefficient.
2018, 37(6): 957-962.
doi: 10.13433/j.cnki.1003-8728.2018.0619
Abstract:
An automation test rig using the proven three point contact configuration was applied to studying the effect of slide to roll ratio (SRR) on the tribological behavior of lubricated steel/steel contacts in a boundary lubrication regime. The tested specimen surface was examined under an optical microscope and a scanning electron microscope (SEM) to study the fatigue behavior of the specimen surface. Then the X-ray photo-electronic spectroscope (XPS) is applied to studying the related tribochemistry behavior. The study results show that the increase of SRR can reduce the number of micropits on the worn surface, while wear increased and friction did not change much. XPS study results indicate that the increase of SRR resulted in the increase of oxide concentration on the worn surface as well as the film thickness. Therefore, the effect of SRR on the tribological behavior of lubricated steel/steel contacts in the boundary lubrication regime is not only related to friction and wear but also highly depends on related tribochemistry.
An automation test rig using the proven three point contact configuration was applied to studying the effect of slide to roll ratio (SRR) on the tribological behavior of lubricated steel/steel contacts in a boundary lubrication regime. The tested specimen surface was examined under an optical microscope and a scanning electron microscope (SEM) to study the fatigue behavior of the specimen surface. Then the X-ray photo-electronic spectroscope (XPS) is applied to studying the related tribochemistry behavior. The study results show that the increase of SRR can reduce the number of micropits on the worn surface, while wear increased and friction did not change much. XPS study results indicate that the increase of SRR resulted in the increase of oxide concentration on the worn surface as well as the film thickness. Therefore, the effect of SRR on the tribological behavior of lubricated steel/steel contacts in the boundary lubrication regime is not only related to friction and wear but also highly depends on related tribochemistry.
2018, 37(6): 963-970.
doi: 10.13433/j.cnki.1003-8728.2018.0620
Abstract:
A general performance calculation model was established for the pulse detonation shaft power device (PDSPD) with pulse detonation combustor (PDC). The detonation chamber model used PDC characteristic diagram. The influence of operating parameters on the performance of PDSPD was studied. The study results show that:under constant operating frequency, the power per liter and the shaft power rise with the increase of the pressure ratio, while the specific fuel consumption decreases; there is an optimum pressure ratio when the specific power reaches its maximum value; under constant pressure ratio, the power per liter of PDSPD rises with the increase of operating frequency. The performance of PDSPD and other three shaft power devices were compared under different operating conditions. The comparison results show that the specific fuel consumption level of PDSPD is close to that of the diesel engine at the same displacement and shaft power. Compared with the gasoline engine, PDSPD's specific fuel consumption level decreases with the same shaft power in a certain range of pressure ratios. Compared with the turbo-shaft engine, the specific power of PDSPD increases by more than 38.08%, and the specific fuel consumption decreases by 41.42%. Therefore, the propulsion, economy and thrust weight ratio of the engine are greatly improved.
A general performance calculation model was established for the pulse detonation shaft power device (PDSPD) with pulse detonation combustor (PDC). The detonation chamber model used PDC characteristic diagram. The influence of operating parameters on the performance of PDSPD was studied. The study results show that:under constant operating frequency, the power per liter and the shaft power rise with the increase of the pressure ratio, while the specific fuel consumption decreases; there is an optimum pressure ratio when the specific power reaches its maximum value; under constant pressure ratio, the power per liter of PDSPD rises with the increase of operating frequency. The performance of PDSPD and other three shaft power devices were compared under different operating conditions. The comparison results show that the specific fuel consumption level of PDSPD is close to that of the diesel engine at the same displacement and shaft power. Compared with the gasoline engine, PDSPD's specific fuel consumption level decreases with the same shaft power in a certain range of pressure ratios. Compared with the turbo-shaft engine, the specific power of PDSPD increases by more than 38.08%, and the specific fuel consumption decreases by 41.42%. Therefore, the propulsion, economy and thrust weight ratio of the engine are greatly improved.
2018, 37(6): 971-979.
doi: 10.13433/j.cnki.1003-8728.2018.0621
Abstract:
This paper focuses on the dragonflies and dragonflies-like FWMAV, mainly on the wings morphology, material attributes, mechanical properties and aerodynamics of wings. The development prospects and research trends of flapping structure are proposed, which are using more advanced observation instruments to explore the details of the wings to obtain the wing optimization inspiration, and in the simulation of wings strength, using different material properties to satisfy the diversity of the current bionic wings, and the computational model should tend to the real situation of the wings. In addition, a lot of experimental verifications need to be made to catch the developing of computational simulations.
This paper focuses on the dragonflies and dragonflies-like FWMAV, mainly on the wings morphology, material attributes, mechanical properties and aerodynamics of wings. The development prospects and research trends of flapping structure are proposed, which are using more advanced observation instruments to explore the details of the wings to obtain the wing optimization inspiration, and in the simulation of wings strength, using different material properties to satisfy the diversity of the current bionic wings, and the computational model should tend to the real situation of the wings. In addition, a lot of experimental verifications need to be made to catch the developing of computational simulations.
2018, 37(6): 980-984.
doi: 10.13433/j.cnki.1003-8728.2018.0622
Abstract:
In this paper, the transient thermal stress distribution of variable property for two-dimensional functionally graded material (FGM) plates under non-uniform temperature field is investigated. The model for Al1100-Ti6Al4V-ZrO2 two-dimensional FGM plate is established and the finite element solution for 2D-FGM plate is constructed, which are obtained by calculating 1) the distribution of two-dimensional FGM plate transient thermal stress in different time transient; 2) the distribution of variable property (component coefficient along the plate length and width direction) two-dimensional FGM plate transient thermal stress; 3) under non-uniform temperature field (including constant temperature and linear temperature distribution, nonlinear temperature distribution and temperature distribution of periodic) the distribution of transient thermal stress in two-dimensional FGM plate. The present method can be used as a reference for calculating and analyzing the transient thermal stress for two-dimensional functionally graded materials plate.
In this paper, the transient thermal stress distribution of variable property for two-dimensional functionally graded material (FGM) plates under non-uniform temperature field is investigated. The model for Al1100-Ti6Al4V-ZrO2 two-dimensional FGM plate is established and the finite element solution for 2D-FGM plate is constructed, which are obtained by calculating 1) the distribution of two-dimensional FGM plate transient thermal stress in different time transient; 2) the distribution of variable property (component coefficient along the plate length and width direction) two-dimensional FGM plate transient thermal stress; 3) under non-uniform temperature field (including constant temperature and linear temperature distribution, nonlinear temperature distribution and temperature distribution of periodic) the distribution of transient thermal stress in two-dimensional FGM plate. The present method can be used as a reference for calculating and analyzing the transient thermal stress for two-dimensional functionally graded materials plate.
