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RSS2015 Vol. 34, No. 4
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2015, 34(4): 493-497.
doi: 10.13433/j.cnki.1003-8728.2015.0401
PDF 2897KB
Abstract:
Considering swash-plate engine has complicated structure,huge finite element model and poor analysis efficiency, the component mode synthesis(CMS) technique was adopted to structural dynamics analysis and vibration reduction design. The CMS analysis model was constructed by Ansys software and calculate the modes. The engine vibration sources and vibration transfer routes were analyzed; vibration reduction measures were discussed, and advanced set isolator at key bearings to reduce vibration. Based on CMS model, isolator substructure set was took into CMS model to got reduction calculation model,and harmonic response results shows the reduction measure is successful at low-frequency stage.
Considering swash-plate engine has complicated structure,huge finite element model and poor analysis efficiency, the component mode synthesis(CMS) technique was adopted to structural dynamics analysis and vibration reduction design. The CMS analysis model was constructed by Ansys software and calculate the modes. The engine vibration sources and vibration transfer routes were analyzed; vibration reduction measures were discussed, and advanced set isolator at key bearings to reduce vibration. Based on CMS model, isolator substructure set was took into CMS model to got reduction calculation model,and harmonic response results shows the reduction measure is successful at low-frequency stage.
2015, 34(4): 498-501.
doi: 10.13433/j.cnki.1003-8728.2015.0402
Abstract:
In order to investigate the torsional vibration characteristics of inline 4-cylinders gasoline engine working with cylinder deactivation and explore the best cylinder deactivation schemes,a crankshaft model is established with the multi-body dynamics software AVL-EXCITE Designer and is validated by experiments. Different cylinder deactivation schemes under 20%~40 of engine load are simulated respectively. The result makes clear that the torsional vibration angle displacement amplitude of the crankshaft under cylinder deactivation increases significantly,which is mainly composed of low order rolling vibrations. For inline 4-cylinders gasoline engine, the crankshaft torsion vibration characteristics of two cylinders with deactivation on both ends is better than the middle two cylinders with deactivation.
In order to investigate the torsional vibration characteristics of inline 4-cylinders gasoline engine working with cylinder deactivation and explore the best cylinder deactivation schemes,a crankshaft model is established with the multi-body dynamics software AVL-EXCITE Designer and is validated by experiments. Different cylinder deactivation schemes under 20%~40 of engine load are simulated respectively. The result makes clear that the torsional vibration angle displacement amplitude of the crankshaft under cylinder deactivation increases significantly,which is mainly composed of low order rolling vibrations. For inline 4-cylinders gasoline engine, the crankshaft torsion vibration characteristics of two cylinders with deactivation on both ends is better than the middle two cylinders with deactivation.
2015, 34(4): 502-506.
doi: 10.13433/j.cnki.1003-8728.2015.0403
Abstract:
A method for determining the similarity coefficients based on the optimization theory is put forward. The method regards the similarity coefficients as optimization variables and defines the functional index of a model as optimization objective. Then a case of rotor model design is provided to demonstrate the feasibility of our method. The design results show that the model based on this method is similar to the prototype. Particularly, the model based on the similarity theory is a special case of the model based on our method. It contributes a solution for determining the similarity coefficients of the incomplete similarity model and provides a new theoretical basis for designing models of a complex system.
A method for determining the similarity coefficients based on the optimization theory is put forward. The method regards the similarity coefficients as optimization variables and defines the functional index of a model as optimization objective. Then a case of rotor model design is provided to demonstrate the feasibility of our method. The design results show that the model based on this method is similar to the prototype. Particularly, the model based on the similarity theory is a special case of the model based on our method. It contributes a solution for determining the similarity coefficients of the incomplete similarity model and provides a new theoretical basis for designing models of a complex system.
2015, 34(4): 507-511.
doi: 10.13433/j.cnki.1003-8728.2015.0404
Abstract:
The dynamics equation is established for a planar flexible beam and girder structure with known large overall motion. After analysis, the accurate nonlinear equations is put forward. The finite element method is used for the system discretization and the coupling dynamics equations of flexible beams and girders are obtained by the Lagrange multipliers. Compared with the one-order coupling model, each matrix of our model adds two kinds of coupling: the velocity and the angular velocity coupling terms of basic point and the deformation coupling term. Compared the zero-order coupling model and the one-order coupling model with the accurate nonlinear model through simulation in dynamic response. The roles of various coupling terms is determined and qualitative analysis is carried out.
The dynamics equation is established for a planar flexible beam and girder structure with known large overall motion. After analysis, the accurate nonlinear equations is put forward. The finite element method is used for the system discretization and the coupling dynamics equations of flexible beams and girders are obtained by the Lagrange multipliers. Compared with the one-order coupling model, each matrix of our model adds two kinds of coupling: the velocity and the angular velocity coupling terms of basic point and the deformation coupling term. Compared the zero-order coupling model and the one-order coupling model with the accurate nonlinear model through simulation in dynamic response. The roles of various coupling terms is determined and qualitative analysis is carried out.
2015, 34(4): 512-517.
doi: 10.13433/j.cnki.1003-8728.2015.0405
Abstract:
Nanopowder of hydrogen storage material will be widely used for fuel cell vehicle, and the other application fields of nanopowder are simply introduced. The fundamental principle of physically and chemically fabricating nanopowder in laboratory is analyzed respectively. The fundamental principle and system composition of mechanically ball mill for fabricating nanopowder in laboratory are expounded. The electric motor types, angular speed change in a revolution of stirring principal shaft, surface shape of principal rotation shaft and radial stirring teeth in the radial direction of stirring principal shaft, layer numbers of radial stirring teeth, stirring rod numbers in the every radial stirring layer, cross section shape of stirring principal shaft & radial stirring rod in the ball mill used for laboratory are primarily analyzed. The influence laws of AC servo motor driving way and different mechanical structure shape on steel ball dynamic response,ball flow fields properties and ball grinding effect for material powder are obtained. Electric drives and mechanical structure precept in ball mill are optimized.
Nanopowder of hydrogen storage material will be widely used for fuel cell vehicle, and the other application fields of nanopowder are simply introduced. The fundamental principle of physically and chemically fabricating nanopowder in laboratory is analyzed respectively. The fundamental principle and system composition of mechanically ball mill for fabricating nanopowder in laboratory are expounded. The electric motor types, angular speed change in a revolution of stirring principal shaft, surface shape of principal rotation shaft and radial stirring teeth in the radial direction of stirring principal shaft, layer numbers of radial stirring teeth, stirring rod numbers in the every radial stirring layer, cross section shape of stirring principal shaft & radial stirring rod in the ball mill used for laboratory are primarily analyzed. The influence laws of AC servo motor driving way and different mechanical structure shape on steel ball dynamic response,ball flow fields properties and ball grinding effect for material powder are obtained. Electric drives and mechanical structure precept in ball mill are optimized.
2015, 34(4): 518-521.
doi: 10.13433/j.cnki.1003-8728.2015.0406
Abstract:
A kinematics model for the symmetric 3-PRR planar parallel mechanism is established.The kinematic equations are derived by using the coordinate transformation method, and the forward and inverse position solutions are solved by the theoretical method and Matlab method. In solving the forward position solutions, half-angle formula method is adopted. The kinematics simulation of the mechanism via Pro/E's Mechanism module is carried out, and the simulation trajectory and path planning of the center of the moving platform are analyzed and compared, which verifies the correctness of the modeling methods and feasibility of institutions.
A kinematics model for the symmetric 3-PRR planar parallel mechanism is established.The kinematic equations are derived by using the coordinate transformation method, and the forward and inverse position solutions are solved by the theoretical method and Matlab method. In solving the forward position solutions, half-angle formula method is adopted. The kinematics simulation of the mechanism via Pro/E's Mechanism module is carried out, and the simulation trajectory and path planning of the center of the moving platform are analyzed and compared, which verifies the correctness of the modeling methods and feasibility of institutions.
2015, 34(4): 522-525.
doi: 10.13433/j.cnki.1003-8728.2015.0407
Abstract:
The surface texture of the friction surface plays a role in improving the contacting manner and lubrication state between the friction surfaces. Lattice Boltzmann method is introduced to the theoretical analysis and the numerical simulation of surface texture. A simulation calculation program has been written with D2Q9 two-dimensional velocity model and non-equilibrium extrapolation boundary processing format. The flow on the texture surface is simulated with this program mainly relating to the two-dimensional square groove, the triangle groove and the trapezoidal groove. Corresponding to the above-mentioned flow, the flow diagrams are calculated based on the different Reynolds numbers. At the same time, the changes of the flow for the different grooves are analyzed. The drag coefficients involving in different shapes and depths were calculated while the influencing factors are summarized. Through the comparison of the surface resistance, the results show that the trapezoidal groove is best surface texture. There exists an optimal value of the depth to diameter ratio seen from the simulation of the square groove. Thus, Boltzmann method is an effective method to simulate complex fluid motion.
The surface texture of the friction surface plays a role in improving the contacting manner and lubrication state between the friction surfaces. Lattice Boltzmann method is introduced to the theoretical analysis and the numerical simulation of surface texture. A simulation calculation program has been written with D2Q9 two-dimensional velocity model and non-equilibrium extrapolation boundary processing format. The flow on the texture surface is simulated with this program mainly relating to the two-dimensional square groove, the triangle groove and the trapezoidal groove. Corresponding to the above-mentioned flow, the flow diagrams are calculated based on the different Reynolds numbers. At the same time, the changes of the flow for the different grooves are analyzed. The drag coefficients involving in different shapes and depths were calculated while the influencing factors are summarized. Through the comparison of the surface resistance, the results show that the trapezoidal groove is best surface texture. There exists an optimal value of the depth to diameter ratio seen from the simulation of the square groove. Thus, Boltzmann method is an effective method to simulate complex fluid motion.
2015, 34(4): 526-532.
doi: 10.13433/j.cnki.1003-8728.2015.0408
Abstract:
In order to obtain the equilibrium state and dynamic characteristics of the steel strip, it is necessary to regard the steel strip and air cushions as a coupling system. Taking the steel strip as an axially moving Euler-Bernoulli beam under tension and using the Ground-Effect theory to describe the gas dynamics characteristics in air cushion area, the governing equations and coupling condition of the system are established. By introducing the Green's function for static deflection of the strip, the transverse deformation of the strip is represented explicitly in terms of the pressure by convolution. The equilibrium pressure in air cushion area and the strip deformation are determined by Newton-Raphson method. Then the governing equations of the system are linearized at the equilibrium state, and a set of differential equations with non-constant coefficients is obtained. Global discretization is conducted with Galerkin's method. The natural frequencies of the steel strip are determined by numerical method of generalized matrix eigenvalue problem. The results show that reducing speed and raising tension appropriately have favorable impact on the stability of steel strip; however, supply pressure impact on dynamic characteristics of steel strip is extremely limited.
In order to obtain the equilibrium state and dynamic characteristics of the steel strip, it is necessary to regard the steel strip and air cushions as a coupling system. Taking the steel strip as an axially moving Euler-Bernoulli beam under tension and using the Ground-Effect theory to describe the gas dynamics characteristics in air cushion area, the governing equations and coupling condition of the system are established. By introducing the Green's function for static deflection of the strip, the transverse deformation of the strip is represented explicitly in terms of the pressure by convolution. The equilibrium pressure in air cushion area and the strip deformation are determined by Newton-Raphson method. Then the governing equations of the system are linearized at the equilibrium state, and a set of differential equations with non-constant coefficients is obtained. Global discretization is conducted with Galerkin's method. The natural frequencies of the steel strip are determined by numerical method of generalized matrix eigenvalue problem. The results show that reducing speed and raising tension appropriately have favorable impact on the stability of steel strip; however, supply pressure impact on dynamic characteristics of steel strip is extremely limited.
2015, 34(4): 533-537.
doi: 10.13433/j.cnki.1003-8728.2015.0409
Abstract:
An oil tank cleaning robot is a special device for implementing the automatic cleaning of the sludge on the bottom of an oil tank. After analyzing the working environments and processes of the oil tank, a dynamic energy stability pyramid was adopted to analyze the cleaning stability of the oil tank wall and the blind spots of sludge on the oil tank bottom. The simulation was carried out with the ADAMS. The cleaning robot can guarantee its tumble stability when its robot velocity is within. When the angle of inclination of the cleaning robot is 30 degrees and the velocity of the nozzle pulsed with water jet is not greater than 100 m/s, the cleaning robot is stable. The simulation results are in conformity with the basic design parameters of a cleaning robot and reveal that the cleaning robot can effectively clean oil tank bottom sludge.
An oil tank cleaning robot is a special device for implementing the automatic cleaning of the sludge on the bottom of an oil tank. After analyzing the working environments and processes of the oil tank, a dynamic energy stability pyramid was adopted to analyze the cleaning stability of the oil tank wall and the blind spots of sludge on the oil tank bottom. The simulation was carried out with the ADAMS. The cleaning robot can guarantee its tumble stability when its robot velocity is within. When the angle of inclination of the cleaning robot is 30 degrees and the velocity of the nozzle pulsed with water jet is not greater than 100 m/s, the cleaning robot is stable. The simulation results are in conformity with the basic design parameters of a cleaning robot and reveal that the cleaning robot can effectively clean oil tank bottom sludge.
2015, 34(4): 538-543.
doi: 10.13433/j.cnki.1003-8728.2015.0410
Abstract:
Taking into consideration the vibrational signals of nonlinear and non-stationary and weak faults of a planetary gear transmission system, the paper conducted a comprehensive analysis of its normal, single and multiple coupling failure characteristics based on the chaos theory. The acquisition of vibrational signal was pretreated using the wavelet packet algorithm. The best time delay and minimum embedding dimension were chosen to reconstruct phase space. On this basis, phase portraits were used to qualitatively describe the failure types of different failure states; correlation dimensions and the largest Lyapunov exponent were used to quantify the characteristics and levels of different failure states. The analysis results show that the phase portraits of five different failure states have certain differences, the more serious the fault, the more coupling faults there are, the larger correlation dimensions and the Lyapunov exponent are, and the greater chaos characteristics of failure states are. Thus the qualitative and quantitative methods of the chaos theory can be used to identify the single fault and two coupling faults of the planetary gear transmission system. Its coupling faults have non-overlapping and overlapping fault features.
Taking into consideration the vibrational signals of nonlinear and non-stationary and weak faults of a planetary gear transmission system, the paper conducted a comprehensive analysis of its normal, single and multiple coupling failure characteristics based on the chaos theory. The acquisition of vibrational signal was pretreated using the wavelet packet algorithm. The best time delay and minimum embedding dimension were chosen to reconstruct phase space. On this basis, phase portraits were used to qualitatively describe the failure types of different failure states; correlation dimensions and the largest Lyapunov exponent were used to quantify the characteristics and levels of different failure states. The analysis results show that the phase portraits of five different failure states have certain differences, the more serious the fault, the more coupling faults there are, the larger correlation dimensions and the Lyapunov exponent are, and the greater chaos characteristics of failure states are. Thus the qualitative and quantitative methods of the chaos theory can be used to identify the single fault and two coupling faults of the planetary gear transmission system. Its coupling faults have non-overlapping and overlapping fault features.
2015, 34(4): 544-548.
doi: 10.13433/j.cnki.1003-8728.2015.0411
Abstract:
An equation based on arc function of the tangent angle was put forward to represent any possible convex and concave lines to meet the requirements of finger beam forming. The universal expression and the characteristic parameters of the general profile were obtained based on the Taylor series. The finger seal was optimized aiming at low leakage rate and low wear rate. Then the fingertip beam shape optimization and other geometric structural parameters optimization would achieve simultaneously. The optimization results indicate that the general profile finger seal structure form with good comprehensive properties can be obtained by two-objective optimization. Compared with the finger seal with existing circular arc profile or the involute profile, the finger seal with general convex profile had a similar performance. The finger seal with general concave profile had obvious advantages in meeting the low leakage performance.
An equation based on arc function of the tangent angle was put forward to represent any possible convex and concave lines to meet the requirements of finger beam forming. The universal expression and the characteristic parameters of the general profile were obtained based on the Taylor series. The finger seal was optimized aiming at low leakage rate and low wear rate. Then the fingertip beam shape optimization and other geometric structural parameters optimization would achieve simultaneously. The optimization results indicate that the general profile finger seal structure form with good comprehensive properties can be obtained by two-objective optimization. Compared with the finger seal with existing circular arc profile or the involute profile, the finger seal with general convex profile had a similar performance. The finger seal with general concave profile had obvious advantages in meeting the low leakage performance.
2015, 34(4): 549-554.
doi: 10.13433/j.cnki.1003-8728.2015.0412
Abstract:
Aiming to the criteria of knowledge retrieval methods resulting in low precision of knowledge reuse via the traditional "similar parts structure with similar process", 3D machining process knowledge reuse methods is proposed based on the "similar environmental characteristics with similar process". Firstly, the AAG (Attribution Adjacency Graph) process model is established a mathematical expression with a modified subgraph isomorphism matching method for processing feature extraction. Secondly, the extracted features is reconstructed with the machining feature adjacency graph processing. Thirdly, the feature-based machining feature environments is gotten by defining rules. The matching parameters including the feature type, attachment surface types and topological relations between features and other information, the machining process knowledge can be reused by inputing the machining feature environment for similarity matching into the process models,. Examples show that the present method can effectively match a similar machining feature environment and search the environment so as to match the similar process.
Aiming to the criteria of knowledge retrieval methods resulting in low precision of knowledge reuse via the traditional "similar parts structure with similar process", 3D machining process knowledge reuse methods is proposed based on the "similar environmental characteristics with similar process". Firstly, the AAG (Attribution Adjacency Graph) process model is established a mathematical expression with a modified subgraph isomorphism matching method for processing feature extraction. Secondly, the extracted features is reconstructed with the machining feature adjacency graph processing. Thirdly, the feature-based machining feature environments is gotten by defining rules. The matching parameters including the feature type, attachment surface types and topological relations between features and other information, the machining process knowledge can be reused by inputing the machining feature environment for similarity matching into the process models,. Examples show that the present method can effectively match a similar machining feature environment and search the environment so as to match the similar process.
2015, 34(4): 555-559.
doi: 10.13433/j.cnki.1003-8728.2015.0413
Abstract:
The pendulum length is a key parameter which achieves automatic tracking about 5-axis machining center. The processing precision of machining center is directly influenced by the pendulum length. A method for measuring the pendulum length about tool axis pendulum type machining center is presented, in which the principle is that actual variations of machine coordinate values should be consistent with the calculated variations according to the geometric relations between pendulum length and swing angle of tool axis. Compared with the traditional method, example demonstrates that the present precision is higher than the traditional. In addition, the method is proved to be reliable and practical.
The pendulum length is a key parameter which achieves automatic tracking about 5-axis machining center. The processing precision of machining center is directly influenced by the pendulum length. A method for measuring the pendulum length about tool axis pendulum type machining center is presented, in which the principle is that actual variations of machine coordinate values should be consistent with the calculated variations according to the geometric relations between pendulum length and swing angle of tool axis. Compared with the traditional method, example demonstrates that the present precision is higher than the traditional. In addition, the method is proved to be reliable and practical.
2015, 34(4): 560-564.
doi: 10.13433/j.cnki.1003-8728.2015.0414
Abstract:
A new electric hot milling method is proposed firstly, and then this paper has proposed the theory and the experimental device of the new method. It has been proved by experiment and analyzing the vibration signal processed by wavelet transform on the new method that it really can significantly reduce the vibration and increase the tool life in milling process. And it also can reduce the surface roughness of the material. Besides, the device is not only cheap but also simple and practical. A new high-temperature hardness measurement method based on electric hot technology is proposed. The change of hardness at high temperature of the hardened steel has been analyzed. The hardness of T10A carbon tool steel which has been hardened is nearly 57HRC in normal atmospheric temperature, but the hardness drastically reduce to hardness 30HRC when the material is heated to 300 ℃. So the efficiency of the new electric hot milling method has also been proved.
A new electric hot milling method is proposed firstly, and then this paper has proposed the theory and the experimental device of the new method. It has been proved by experiment and analyzing the vibration signal processed by wavelet transform on the new method that it really can significantly reduce the vibration and increase the tool life in milling process. And it also can reduce the surface roughness of the material. Besides, the device is not only cheap but also simple and practical. A new high-temperature hardness measurement method based on electric hot technology is proposed. The change of hardness at high temperature of the hardened steel has been analyzed. The hardness of T10A carbon tool steel which has been hardened is nearly 57HRC in normal atmospheric temperature, but the hardness drastically reduce to hardness 30HRC when the material is heated to 300 ℃. So the efficiency of the new electric hot milling method has also been proved.
2015, 34(4): 565-569.
doi: 10.13433/j.cnki.1003-8728.2015.0415
Abstract:
Aiming at of the buckling of precision products with complex surface for automotive, the parameters of the main factors influencing deformation values including injection time, mold temperature, melt temperature, packing pressure curve and the coolant temperature in the early stages of the design of experiments are determined according to the design principles of mold flow. The maximum value in Z direction as a optimization target, a model for issue of response affected by multiple variables is established by using the CCD second order response surface design method and selecting the melting temperature, the curve of packing pressure and coolant temperature for testing variables, and the analysis of mold flow is carried out so as to obtain the testing results. The optimal combination of process parameters is obtained under the conditions of multiple criteria by identifying the significance of regression equation via F test and drawing the available response surface equation, and the reliability of the optimization scheme is verified by using the CAE analysis. By tracking and measuring the car door handle, the results show that the optimal solution will enable to decrease the amount of buckling above 16%, and to meet the appearance and functional requirements of precision products, comparing with that of injection mold without experimental optimization.
Aiming at of the buckling of precision products with complex surface for automotive, the parameters of the main factors influencing deformation values including injection time, mold temperature, melt temperature, packing pressure curve and the coolant temperature in the early stages of the design of experiments are determined according to the design principles of mold flow. The maximum value in Z direction as a optimization target, a model for issue of response affected by multiple variables is established by using the CCD second order response surface design method and selecting the melting temperature, the curve of packing pressure and coolant temperature for testing variables, and the analysis of mold flow is carried out so as to obtain the testing results. The optimal combination of process parameters is obtained under the conditions of multiple criteria by identifying the significance of regression equation via F test and drawing the available response surface equation, and the reliability of the optimization scheme is verified by using the CAE analysis. By tracking and measuring the car door handle, the results show that the optimal solution will enable to decrease the amount of buckling above 16%, and to meet the appearance and functional requirements of precision products, comparing with that of injection mold without experimental optimization.
2015, 34(4): 570-576.
doi: 10.13433/j.cnki.1003-8728.2015.0416
Abstract:
With the analysis of injection mould-repair knowledge, a knowledge cluster method to get typical mould-repair project based on the ontology was presented, the domain ontology of the injection mould-repair knowledge was established, a model for the mould-repair project by using the data matrix was built. The semantic similarity between the mould-repair concepts was obtained by calculating the similarity of the mould-repair knowledge domain ontology concepts. The normalized formula was to calculate the similarities between the mould-repair projects and between the clusters. The similarity matrix was used to indicate similarity between mould-repair projects. The mould-repair project clusters were eventually merged by the agglomerative hierarchical cluster method. The cluster result was determined by the cluster granularity of mould-repair projects. The present method has been applied successfully to cluster the typical mould-repair projects by some mould-repair projects from the mould corporation.
With the analysis of injection mould-repair knowledge, a knowledge cluster method to get typical mould-repair project based on the ontology was presented, the domain ontology of the injection mould-repair knowledge was established, a model for the mould-repair project by using the data matrix was built. The semantic similarity between the mould-repair concepts was obtained by calculating the similarity of the mould-repair knowledge domain ontology concepts. The normalized formula was to calculate the similarities between the mould-repair projects and between the clusters. The similarity matrix was used to indicate similarity between mould-repair projects. The mould-repair project clusters were eventually merged by the agglomerative hierarchical cluster method. The cluster result was determined by the cluster granularity of mould-repair projects. The present method has been applied successfully to cluster the typical mould-repair projects by some mould-repair projects from the mould corporation.
2015, 34(4): 577-581.
doi: 10.13433/j.cnki.1003-8728.2015.0417
Abstract:
Aiming at the problem of frictional resistance existed in feeding platforms of NC machine tools, the structure and operating principle of a novel magnetic levitation feeding platform based on the hybrid excited linear synchronous motor(HELSM) are proposed in this paper. There is magnetic force coupling between the electromagnetic thrust and the normal force, because the driving system and levitation system share a common air-gap magnetic field. The numerical analysis and finite element validation to the electromagnetic thrust and normal force of the HELSM are run. The correlative state equation and output equation of the system are established and the decoupling control is run. The result shows that the electromagnetic thrust and normal force can be completely decoupled after applying state feedback and input transformation. This study will be useful to improve the stability and positioning accuracy to the feeding platform.
Aiming at the problem of frictional resistance existed in feeding platforms of NC machine tools, the structure and operating principle of a novel magnetic levitation feeding platform based on the hybrid excited linear synchronous motor(HELSM) are proposed in this paper. There is magnetic force coupling between the electromagnetic thrust and the normal force, because the driving system and levitation system share a common air-gap magnetic field. The numerical analysis and finite element validation to the electromagnetic thrust and normal force of the HELSM are run. The correlative state equation and output equation of the system are established and the decoupling control is run. The result shows that the electromagnetic thrust and normal force can be completely decoupled after applying state feedback and input transformation. This study will be useful to improve the stability and positioning accuracy to the feeding platform.
2015, 34(4): 582-585.
doi: 10.13433/j.cnki.1003-8728.2015.0418
Abstract:
Because of the uncertainty of the position of a functional axis of the thread while connecting threads, such as the low interconvertibility, low reliability, the increase of manufacturing cost, etc., a new method for measuring the functional axis of the thread is presented on the basis of the synthetic thread measurement principle. The flexible sliced tooth-type gauge head with high stiffness is adopted to encircle and engage with the thread tightly. The TESA inductance type transducer is used to measure the position change of the gauge head, which reflects changes in the functional diameter of the thread. Through processing data, the generalities of the functional diameter of the thread are obtained. With the existing theory of functional axis of thread, its functional axis are worked out. The experimental results verify the feasibility of the measurement method, with which the measurement accuracy is higher than 10 μm. The measurement method presented in this paper contributes to solving the deficiency of the current study of the functional axis of thread.
Because of the uncertainty of the position of a functional axis of the thread while connecting threads, such as the low interconvertibility, low reliability, the increase of manufacturing cost, etc., a new method for measuring the functional axis of the thread is presented on the basis of the synthetic thread measurement principle. The flexible sliced tooth-type gauge head with high stiffness is adopted to encircle and engage with the thread tightly. The TESA inductance type transducer is used to measure the position change of the gauge head, which reflects changes in the functional diameter of the thread. Through processing data, the generalities of the functional diameter of the thread are obtained. With the existing theory of functional axis of thread, its functional axis are worked out. The experimental results verify the feasibility of the measurement method, with which the measurement accuracy is higher than 10 μm. The measurement method presented in this paper contributes to solving the deficiency of the current study of the functional axis of thread.
2015, 34(4): 586-589.
doi: 10.13433/j.cnki.1003-8728.2015.0419
Abstract:
This paper presents the 3D gaze estimation method based on binocular model. The method can overcome the two inherent problems of the 2D gaze estimation method, namely restriction on head movement and complex procedures for calibrating individual parameters. Firstly, we use two cameras on which groups of infrared lights are installed around the center of the lens to establish a stereo vision system. Then using this stereo vision system, the cameras capture eye images. Secondly, based on the non-spherical model of a cornea, we set up the 3D eye model which is adaptive to estimate 3D gaze. Thirdly the binocular optical axis calculation method is deduced. Finally, the midpoint between two intersection points of the left and right eye optical axis and the computer screen is calculated. With these, the fixation point is determined. The 3D gaze estimation method can estimate the eye gaze under natural head movement. Moreover, except only once, calibration by a user is not required (no calibration). The 3D gaze estimation method has high accuracy.
This paper presents the 3D gaze estimation method based on binocular model. The method can overcome the two inherent problems of the 2D gaze estimation method, namely restriction on head movement and complex procedures for calibrating individual parameters. Firstly, we use two cameras on which groups of infrared lights are installed around the center of the lens to establish a stereo vision system. Then using this stereo vision system, the cameras capture eye images. Secondly, based on the non-spherical model of a cornea, we set up the 3D eye model which is adaptive to estimate 3D gaze. Thirdly the binocular optical axis calculation method is deduced. Finally, the midpoint between two intersection points of the left and right eye optical axis and the computer screen is calculated. With these, the fixation point is determined. The 3D gaze estimation method can estimate the eye gaze under natural head movement. Moreover, except only once, calibration by a user is not required (no calibration). The 3D gaze estimation method has high accuracy.
2015, 34(4): 590-594.
doi: 10.13433/j.cnki.1003-8728.2015.0420
Abstract:
To solve the problem that its visual control system cannot identify and locate the targets all the time when they perform rotation and scaling or when the lighting condition changes, we proposed the SIFT image matching algorithm and mapped its feature descriptors to a high-dimensional feature space through using the Gaussian kernel function, and then enhanced the targets in the feature space, for example, data dimension reduction. The enhanced SIFT image files were invoked into Labview through the Matlab script and read from spreadsheet file VI nodes, thus realizing the seamless connection of Labview with Matlab. The experimental results show that the Labview and Matlab hybrid programming of the excavator robot's visual control system can solve the problems existing in the old system and is more perfect and powerful.
To solve the problem that its visual control system cannot identify and locate the targets all the time when they perform rotation and scaling or when the lighting condition changes, we proposed the SIFT image matching algorithm and mapped its feature descriptors to a high-dimensional feature space through using the Gaussian kernel function, and then enhanced the targets in the feature space, for example, data dimension reduction. The enhanced SIFT image files were invoked into Labview through the Matlab script and read from spreadsheet file VI nodes, thus realizing the seamless connection of Labview with Matlab. The experimental results show that the Labview and Matlab hybrid programming of the excavator robot's visual control system can solve the problems existing in the old system and is more perfect and powerful.
2015, 34(4): 595-598.
doi: 10.13433/j.cnki.1003-8728.2015.0421
Abstract:
Regarding a racing car as research object, the rear diffuser's effects on aerodynamic performance of the car body is discussed. The reliability of the simulation is verified by comparing wind tunnel test data with CFD numerical simulation on the basis of the initial model. The design of the initial model's diffuser is improved, the working area of the diffuser is increased, and its effect on the aerodynamic force is studied. With numerical simulation method, the improved diffuser and the bionic pit-type non-smooth spoiler with triangle wing are combined,flow field parameters such as pressure and speed are obtained,the improved results of different diffuser for aerodynamic performance are compared, and the reasons for aerodynamic improvement are analyzed. The results show that through the diffuser and non-smooth spoiler's optimal combination, the aerodynamic negative lift can be effectively improved, and the aerodynamic drag is reduced, so that the purpose of coordinating coupling relationship between aerodynamic lift and aerodynamic drag is realized.
Regarding a racing car as research object, the rear diffuser's effects on aerodynamic performance of the car body is discussed. The reliability of the simulation is verified by comparing wind tunnel test data with CFD numerical simulation on the basis of the initial model. The design of the initial model's diffuser is improved, the working area of the diffuser is increased, and its effect on the aerodynamic force is studied. With numerical simulation method, the improved diffuser and the bionic pit-type non-smooth spoiler with triangle wing are combined,flow field parameters such as pressure and speed are obtained,the improved results of different diffuser for aerodynamic performance are compared, and the reasons for aerodynamic improvement are analyzed. The results show that through the diffuser and non-smooth spoiler's optimal combination, the aerodynamic negative lift can be effectively improved, and the aerodynamic drag is reduced, so that the purpose of coordinating coupling relationship between aerodynamic lift and aerodynamic drag is realized.
2015, 34(4): 599-602.
doi: 10.13433/j.cnki.1003-8728.2015.0422
Abstract:
Aiming at the optimization for dent resistance of cover body, a whole process method is developed with FEM and the engineering experience to solve the dent resistance problem. The script for fast simulation model is developed considering the material nonlinearity and contact nonlinearity via Tcl/Tk language, the dent resistance is calculated with the Abaqus software. The structure for the variable conditions is optimized with the simplified script parameters. The results show that the present optimization method of whole process for solving the dent resistance for variable conditions is quick, efficient and accurate.
Aiming at the optimization for dent resistance of cover body, a whole process method is developed with FEM and the engineering experience to solve the dent resistance problem. The script for fast simulation model is developed considering the material nonlinearity and contact nonlinearity via Tcl/Tk language, the dent resistance is calculated with the Abaqus software. The structure for the variable conditions is optimized with the simplified script parameters. The results show that the present optimization method of whole process for solving the dent resistance for variable conditions is quick, efficient and accurate.
2015, 34(4): 603-606.
doi: 10.13433/j.cnki.1003-8728.2015.0423
Abstract:
In order to solve the problems about heavy, difficult to adjust, discontinuous inertia rank of mechanical inertia flywheels in the traditional clutch performance test system, the technology of electric emulation for mechanical inertia is introduced to clutch test system. Through analyzing loads on moving automobile, the dynamic model of clutch was developed and combined with the characteristics of clutch test system, the torque feedback and speed closed-loop control method of electric emulation for mechanical inertia was proposed. In contrast to clutch drive away test based on the traditional mechanical inertia flywheels, the result indicates that the control method can accurately simulate the change characteristics of torque and speed of clutch in automobile start.
In order to solve the problems about heavy, difficult to adjust, discontinuous inertia rank of mechanical inertia flywheels in the traditional clutch performance test system, the technology of electric emulation for mechanical inertia is introduced to clutch test system. Through analyzing loads on moving automobile, the dynamic model of clutch was developed and combined with the characteristics of clutch test system, the torque feedback and speed closed-loop control method of electric emulation for mechanical inertia was proposed. In contrast to clutch drive away test based on the traditional mechanical inertia flywheels, the result indicates that the control method can accurately simulate the change characteristics of torque and speed of clutch in automobile start.
2015, 34(4): 607-612.
doi: 10.13433/j.cnki.1003-8728.2015.0424
Abstract:
Based on the transfer matrix method and Newton's second law, this paper derives the hydraulic-mechanical coupled multi-body dynamic equation of model of a school bus fitted with roll resistant specific hydraulic interconnected suspension system. After finishing eigenvalue identification and modal analysis, a comparsion on dynamic characteristics between vehicles which is installed or uninstalled the hydraulic interconnected suspension is produced. To research the coordination of dominant contribution modes of vehicle, the principle of the damping valves is discussed. Based on the modal matching strategy and the requirement for damping characteristic, a design method of damping valves is proposed and proved availably. The study results indicate that the roll resistant specific hydraulic interconnected suspension system can promote the capacity of anti-rollover specific observably and with reasonable comfort performance, the damping characteristics of the coupled system could be optimized.
Based on the transfer matrix method and Newton's second law, this paper derives the hydraulic-mechanical coupled multi-body dynamic equation of model of a school bus fitted with roll resistant specific hydraulic interconnected suspension system. After finishing eigenvalue identification and modal analysis, a comparsion on dynamic characteristics between vehicles which is installed or uninstalled the hydraulic interconnected suspension is produced. To research the coordination of dominant contribution modes of vehicle, the principle of the damping valves is discussed. Based on the modal matching strategy and the requirement for damping characteristic, a design method of damping valves is proposed and proved availably. The study results indicate that the roll resistant specific hydraulic interconnected suspension system can promote the capacity of anti-rollover specific observably and with reasonable comfort performance, the damping characteristics of the coupled system could be optimized.
2015, 34(4): 613-617.
doi: 10.13433/j.cnki.1003-8728.2015.0425
Abstract:
A bolted composite joint with interference-fit is conducted to analyze the stress state and the clamping force with a three-dimensional, solid finite element model. A full definition of the material properties and the contact pairs is implemented. It is shown that the transfer of the clamping load, which is created by the process of bolt tightening, will be affected by the friction significantly. Along the direction of plate thickness, the clamping force reduces from the bottom of the plate to the bolt head. The descending magnitude of clamping force is decided by the number of the bolt load and stress state in the vicinity of the fastener hole.
A bolted composite joint with interference-fit is conducted to analyze the stress state and the clamping force with a three-dimensional, solid finite element model. A full definition of the material properties and the contact pairs is implemented. It is shown that the transfer of the clamping load, which is created by the process of bolt tightening, will be affected by the friction significantly. Along the direction of plate thickness, the clamping force reduces from the bottom of the plate to the bolt head. The descending magnitude of clamping force is decided by the number of the bolt load and stress state in the vicinity of the fastener hole.
2015, 34(4): 618-622.
doi: 10.13433/j.cnki.1003-8728.2015.0426
Abstract:
The mechanical properties of T700/3234 and crushing energy absorption results were obtained respectively by the material performance tests and composite corrugated plate tests under quasi-static crushing. Simulation results based on LS-DYNA were in good agreement with test results, and the correctness of finite element model and material model was verified. The material model parameters were analyzed by the orthogonal design, the nonlinear mapping relationship between the energy absorption and material parameters was showed by a response surface, and the material parameter selection scheme was optimized. The results showed that the optimization method can effectively assist the finite element modeling, and greatly decrease the trial calculation times.
The mechanical properties of T700/3234 and crushing energy absorption results were obtained respectively by the material performance tests and composite corrugated plate tests under quasi-static crushing. Simulation results based on LS-DYNA were in good agreement with test results, and the correctness of finite element model and material model was verified. The material model parameters were analyzed by the orthogonal design, the nonlinear mapping relationship between the energy absorption and material parameters was showed by a response surface, and the material parameter selection scheme was optimized. The results showed that the optimization method can effectively assist the finite element modeling, and greatly decrease the trial calculation times.
2015, 34(4): 623-628.
doi: 10.13433/j.cnki.1003-8728.2015.0427
Abstract:
With a model experiment rig of aircraft engine dual-rotor system under base movements, the dual-rotor system vibration is tested when the aircraft is respectively in hovering, pitching, rolling and hovering-pitching motions. The influence of maneuvering condition over dynamic characteristics of the counter-rotating dual-rotor system is studied. The experimental results show that aircraft transient additional centrifugal force and gyroscopic moment generated in the internal rotor and the external rotor in rolling and pitching motions have a great influence on system transient vibration amplitude and axis center track.
With a model experiment rig of aircraft engine dual-rotor system under base movements, the dual-rotor system vibration is tested when the aircraft is respectively in hovering, pitching, rolling and hovering-pitching motions. The influence of maneuvering condition over dynamic characteristics of the counter-rotating dual-rotor system is studied. The experimental results show that aircraft transient additional centrifugal force and gyroscopic moment generated in the internal rotor and the external rotor in rolling and pitching motions have a great influence on system transient vibration amplitude and axis center track.
2015, 34(4): 629-635.
doi: 10.13433/j.cnki.1003-8728.2015.0428
Abstract:
A Stewart platform actuated by VCM (voice coil motors) is selected as the control device to realize active isolation/suppression for micro-vibration onboard a satellite. A SISO (single input single output) control strategy is established for the Stewart platform by decoupling its dynamic model to the single strut model. The effectiveness of the vibration isolation as well as the limitation on vibration suppression of the Skyhook control method is analyzed, then a PFF (positive force feedback) loop is implemented to achieve isolation. To enhance the robust stability properties of the control system, an acceleration feedback loop is added to the system. Finally, micro-vibration active isolation/suppression experiments and simulations are conducted on the Stewart platform's single strut, as well as Stewart platform rigid-flexible coupling dynamic model. Base sweep excitations and payload single-tone disturbances are induced on both objects, and isolation/suppression is conducted with this paper's control method. The experimental and simulation results show that the control performance is quite good and stable with respect to both vibration isolation and suppression.
A Stewart platform actuated by VCM (voice coil motors) is selected as the control device to realize active isolation/suppression for micro-vibration onboard a satellite. A SISO (single input single output) control strategy is established for the Stewart platform by decoupling its dynamic model to the single strut model. The effectiveness of the vibration isolation as well as the limitation on vibration suppression of the Skyhook control method is analyzed, then a PFF (positive force feedback) loop is implemented to achieve isolation. To enhance the robust stability properties of the control system, an acceleration feedback loop is added to the system. Finally, micro-vibration active isolation/suppression experiments and simulations are conducted on the Stewart platform's single strut, as well as Stewart platform rigid-flexible coupling dynamic model. Base sweep excitations and payload single-tone disturbances are induced on both objects, and isolation/suppression is conducted with this paper's control method. The experimental and simulation results show that the control performance is quite good and stable with respect to both vibration isolation and suppression.
2015, 34(4): 636-640.
doi: 10.13433/j.cnki.1003-8728.2015.0429
Abstract:
The kinetic equation of the high-aspect-ratio wing with an external store is derived based on Hamilton's principle. This paper considers the in-plane bending of the high-aspect-ratio, and extends the bending-torsion motion of the traditional wing to bending-bending-torsion motion of the high-aspect-ratio wing. Dirac function is used to precisely consider the location and properties of the external store. The constraint of the beam is considered with the Lagrange multiplier method. The dimensionless dynamic equation is conducted by the introduction of dimensionless parameters. The Galerkin method is subsequently applied to convert to partial differential equations into a set of ordinary differential equations. The flutter is calculated with the K method. The linear system simulation results are presented to show the linear flutter velocity and then the effects of the store properties, such as location and mass on the wing store linear flutter velocity are also given.
The kinetic equation of the high-aspect-ratio wing with an external store is derived based on Hamilton's principle. This paper considers the in-plane bending of the high-aspect-ratio, and extends the bending-torsion motion of the traditional wing to bending-bending-torsion motion of the high-aspect-ratio wing. Dirac function is used to precisely consider the location and properties of the external store. The constraint of the beam is considered with the Lagrange multiplier method. The dimensionless dynamic equation is conducted by the introduction of dimensionless parameters. The Galerkin method is subsequently applied to convert to partial differential equations into a set of ordinary differential equations. The flutter is calculated with the K method. The linear system simulation results are presented to show the linear flutter velocity and then the effects of the store properties, such as location and mass on the wing store linear flutter velocity are also given.
2015, 34(4): 641-646.
doi: 10.13433/j.cnki.1003-8728.2015.0430
Abstract:
The streamline curvature method is assessed to solve the inverse problem for the S2 stream surface. In order to consider the entropy rise caused by fluid viscosity, the duct-flow loss model by Galvas is modified and coupled with the solving of a control equation in the through-flow calculation. Finally, the through-flow design program of a centrifugal impeller based on the circulation control method is established. Furthermore, to investigate the influence of circulation distribution on the flow field of the centrifugal impeller and its performance, an impeller is designed by using two kinds of circulation distribution with a slight difference at the trailing edge. Then, 3-dimensional numerical analysis is made, and the analysis results show that the circulation distribution has a significant effect on the velocity and blade load distribution of the centrifugal impeller.
The streamline curvature method is assessed to solve the inverse problem for the S2 stream surface. In order to consider the entropy rise caused by fluid viscosity, the duct-flow loss model by Galvas is modified and coupled with the solving of a control equation in the through-flow calculation. Finally, the through-flow design program of a centrifugal impeller based on the circulation control method is established. Furthermore, to investigate the influence of circulation distribution on the flow field of the centrifugal impeller and its performance, an impeller is designed by using two kinds of circulation distribution with a slight difference at the trailing edge. Then, 3-dimensional numerical analysis is made, and the analysis results show that the circulation distribution has a significant effect on the velocity and blade load distribution of the centrifugal impeller.
2015, 34(4): 647-652.
doi: 10.13433/j.cnki.1003-8728.2015.0431
Abstract:
To improve the ergonomic level of the aircraft cockpit and shorten the design process, the genetic algorithms are applied to predict the postures of pilot in terms of the comfort design. In the prediction process, the space coordinates of human body joints are applied to be the variables and the number of them is reduced by the deterministic constraint. The Jack software is used to test the results of the prediction, and it shows that the process is effective. The RULA (Rapid upper Limb Assessment) method is applied to evaluate the posture and supply the comfort parameters. Finally, the different levels of RGB (Red Green Blue) value are used to make the comfort parameters mapping visible.
To improve the ergonomic level of the aircraft cockpit and shorten the design process, the genetic algorithms are applied to predict the postures of pilot in terms of the comfort design. In the prediction process, the space coordinates of human body joints are applied to be the variables and the number of them is reduced by the deterministic constraint. The Jack software is used to test the results of the prediction, and it shows that the process is effective. The RULA (Rapid upper Limb Assessment) method is applied to evaluate the posture and supply the comfort parameters. Finally, the different levels of RGB (Red Green Blue) value are used to make the comfort parameters mapping visible.
2015, 34(4): 653-656.
doi: 10.13433/j.cnki.1003-8728.2015.0432
Abstract:
This paper studies the issue of wide-spread fatigue damage (WFD) crack initiation which focuses on the relationship between crack initiation life and time of widespread fatigue damage occurrence, as well as the impact of multiple site damages (MSD) on crack initiation life. Finally, this paper proposes a correcting calculation method for crack initiation life and damage accumulation base on MSD cracking condition.
This paper studies the issue of wide-spread fatigue damage (WFD) crack initiation which focuses on the relationship between crack initiation life and time of widespread fatigue damage occurrence, as well as the impact of multiple site damages (MSD) on crack initiation life. Finally, this paper proposes a correcting calculation method for crack initiation life and damage accumulation base on MSD cracking condition.
