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RSS2015 Vol. 34, No. 1
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2015, 34(1): 1-7.
doi: 10.13433/j.cnki.1003-8728.2015.0101
PDF 4476KB
Abstract:
Aiming at the kinematics algorithm study of the concentric tube continuous robot applied in minimally invasive surgery, this paper compares several different kinematics algorithms and selects the minimum energy method to establish the kinematics mathematical model on the premise of both accuracy and computational complexity. Then the particle swarm optimization algorithm is used to optimize relevant energy function for the optimal solution because of its powerful optimization ability. Finally, the mapping relation of all parameters from drive space to joint space is set up, and the posture expression from basis point to end point of the robot is obtained through coordinate transformation and parameters fitting. At last, this paper compares the simulation results with the algorithm model by the use of Adams kinematics simulation, which shows the feasibility and accuracy of the kinematics model.
Aiming at the kinematics algorithm study of the concentric tube continuous robot applied in minimally invasive surgery, this paper compares several different kinematics algorithms and selects the minimum energy method to establish the kinematics mathematical model on the premise of both accuracy and computational complexity. Then the particle swarm optimization algorithm is used to optimize relevant energy function for the optimal solution because of its powerful optimization ability. Finally, the mapping relation of all parameters from drive space to joint space is set up, and the posture expression from basis point to end point of the robot is obtained through coordinate transformation and parameters fitting. At last, this paper compares the simulation results with the algorithm model by the use of Adams kinematics simulation, which shows the feasibility and accuracy of the kinematics model.
2015, 34(1): 8-12.
doi: 10.13433/j.cnki.1003-8728.2015.0102
Abstract:
The mass of the underwater vehicle affects its overall performance directly. So after meeting the requirements of strength and stiffness, the mass of submersible should be reduced as much as possible. In this paper, based on orthogonal test method, we achieve the structural optimization of the submersible pressure hull. Because it is more complicated to deal with the constraints by orthogonal test, so the structural optimization problem for the underwater vehicle based on the constraints of strength, stiffness and minimum mass was converted into a multi-objective optimization problem without constraints. By analyzing the test results,we obtained the influence law of each parameter on the strength and weight of the shell. Finally, after the comprehensive consideration, we give the optimal design scheme of the submersible pressure hull.
The mass of the underwater vehicle affects its overall performance directly. So after meeting the requirements of strength and stiffness, the mass of submersible should be reduced as much as possible. In this paper, based on orthogonal test method, we achieve the structural optimization of the submersible pressure hull. Because it is more complicated to deal with the constraints by orthogonal test, so the structural optimization problem for the underwater vehicle based on the constraints of strength, stiffness and minimum mass was converted into a multi-objective optimization problem without constraints. By analyzing the test results,we obtained the influence law of each parameter on the strength and weight of the shell. Finally, after the comprehensive consideration, we give the optimal design scheme of the submersible pressure hull.
2015, 34(1): 13-17.
doi: 10.13433/j.cnki.1003-8728.2015.0103
Abstract:
The complex mode method and Galerkin method are applied to analyze the critical velocity of pinned-pinned pipe conveying fluid resting on Pasternak foundation. Comparing with the exact solution obtained by the complex mode method, the effect of Galerkin modal truncation on the critical velocity is elaborated here, and the effect of Pasternak foundation's shear stiffness and spring stiffness on the truncation error are also focused. It is concluded that the Pasternak foundation's shear stiffness have a greater effect on the system's critical velocity than the spring stiffness, and the increasing of shear stiffness will reduce the truncation error produced by the Galerkin method, but the increasing of spring stiffness will bring a greater truncation error. On the above-mentioned, a new method is proposed that the coefficient can be confirmed by selecting appropriate one in a number of areas. And it is also founded that the calculation efficiency of critical velocity can be improved by choosing the proper order number in the Galerkin method according to different foundation stiffness.
The complex mode method and Galerkin method are applied to analyze the critical velocity of pinned-pinned pipe conveying fluid resting on Pasternak foundation. Comparing with the exact solution obtained by the complex mode method, the effect of Galerkin modal truncation on the critical velocity is elaborated here, and the effect of Pasternak foundation's shear stiffness and spring stiffness on the truncation error are also focused. It is concluded that the Pasternak foundation's shear stiffness have a greater effect on the system's critical velocity than the spring stiffness, and the increasing of shear stiffness will reduce the truncation error produced by the Galerkin method, but the increasing of spring stiffness will bring a greater truncation error. On the above-mentioned, a new method is proposed that the coefficient can be confirmed by selecting appropriate one in a number of areas. And it is also founded that the calculation efficiency of critical velocity can be improved by choosing the proper order number in the Galerkin method according to different foundation stiffness.
2015, 34(1): 18-22.
doi: 10.13433/j.cnki.1003-8728.2015.0104
Abstract:
Having a swash plate piston pump as an example in the paper, the cylinder cavitations mechanism at the same speed and under different diameter ratios was studied and simulated based on computational fluid dynamics (CFD). A formula to calculate the limiting diameter ratio of the plunger and the suction hole was given to ensure the pump flow conditions. The cavitations of the different inlet structure under the same condition and the same diameter ratio were investigated and compared. By the results of the analysis know that the diameter ratio of the plunger and the suction hole has greatly impact on cylinder cavitations, and the different suction hole structures have greatly impact on cylinder cavitations. And the cause of cavitations of the piston pump was also analyzed. This study provides a theoretical basis and design guidance for the design of the piston pump cylinder and piston.
Having a swash plate piston pump as an example in the paper, the cylinder cavitations mechanism at the same speed and under different diameter ratios was studied and simulated based on computational fluid dynamics (CFD). A formula to calculate the limiting diameter ratio of the plunger and the suction hole was given to ensure the pump flow conditions. The cavitations of the different inlet structure under the same condition and the same diameter ratio were investigated and compared. By the results of the analysis know that the diameter ratio of the plunger and the suction hole has greatly impact on cylinder cavitations, and the different suction hole structures have greatly impact on cylinder cavitations. And the cause of cavitations of the piston pump was also analyzed. This study provides a theoretical basis and design guidance for the design of the piston pump cylinder and piston.
2015, 34(1): 23-26.
doi: 10.13433/j.cnki.1003-8728.2015.0105
Abstract:
Finite element method is applied to analyze the static strength and modal properties of a concrete pump base, the results show that the static strength and natural frequencies satisfied the preliminary conditions of lightweight design. Then the density topological optimization method is adopted to carried out the lightweight design of the concrete pump base by taking the material density of element as the design variable, taking the static strength and natural frequency as the design constraints, and taking the minimum volume as the design objective. At the same time, symmetric constraints and minimum member constraints are introduced to guarantee manufacturability after optimization. The results indicate that with the constraints of static strength and natural frequencies, the weight of the concrete pump base can be reduced by 18.3 kg.
Finite element method is applied to analyze the static strength and modal properties of a concrete pump base, the results show that the static strength and natural frequencies satisfied the preliminary conditions of lightweight design. Then the density topological optimization method is adopted to carried out the lightweight design of the concrete pump base by taking the material density of element as the design variable, taking the static strength and natural frequency as the design constraints, and taking the minimum volume as the design objective. At the same time, symmetric constraints and minimum member constraints are introduced to guarantee manufacturability after optimization. The results indicate that with the constraints of static strength and natural frequencies, the weight of the concrete pump base can be reduced by 18.3 kg.
2015, 34(1): 27-31.
doi: 10.13433/j.cnki.1003-8728.2015.0106
Abstract:
The traditional optimization methods cannot find the exact optimal solution of many structural optimization problems because the mathematic models of these types of problems do not exist or can hardly be solved accurately. So interactive method is proposed to cope with the challenge. To overcome the shortcomings of simple genetic algorithms, an improved genetic algorithm (IGA) is proposed. Through analyzing the upper cross beam structure of a 700T cast hydraulic press, the structural optimization model and IGA model of the upper cross beam are built to undertake the IGA-FEM(Finite Element Method) interactive mechanical structure optimization with the objective of light weight and the constraints of qualified stiffness and strength. The optimization results show that the deformation of the upper cross beam maintains the status quo and the maximum equivalent stress is declined by 5.87% while the weight is decreased by 12.09% in comparison to the original design.
The traditional optimization methods cannot find the exact optimal solution of many structural optimization problems because the mathematic models of these types of problems do not exist or can hardly be solved accurately. So interactive method is proposed to cope with the challenge. To overcome the shortcomings of simple genetic algorithms, an improved genetic algorithm (IGA) is proposed. Through analyzing the upper cross beam structure of a 700T cast hydraulic press, the structural optimization model and IGA model of the upper cross beam are built to undertake the IGA-FEM(Finite Element Method) interactive mechanical structure optimization with the objective of light weight and the constraints of qualified stiffness and strength. The optimization results show that the deformation of the upper cross beam maintains the status quo and the maximum equivalent stress is declined by 5.87% while the weight is decreased by 12.09% in comparison to the original design.
2015, 34(1): 32-36.
doi: 10.13433/j.cnki.1003-8728.2015.0107
Abstract:
The integrating finite model for cylinder head, cylinder block and main bearing cap was established, the nonlinear contact boundary conditions were employed by using Abaqus software. The vibration response of the assembly under the rated speed was calculated, and the computed results were compared with the testing results. It shows that the finite model is rational. The deformation of cylinder block, cylinder head fire surface and cylinder hole was analyzed at the maximum firing pressure. The results show that the stiffness of cylinder body skirt is small; the deformation of the central area of cylinder head fire surface is large, the stress in the connection region between cylinder head fire surface and cylinder head is large; the deformation of cylinder hole is small and in engineering allowance.
The integrating finite model for cylinder head, cylinder block and main bearing cap was established, the nonlinear contact boundary conditions were employed by using Abaqus software. The vibration response of the assembly under the rated speed was calculated, and the computed results were compared with the testing results. It shows that the finite model is rational. The deformation of cylinder block, cylinder head fire surface and cylinder hole was analyzed at the maximum firing pressure. The results show that the stiffness of cylinder body skirt is small; the deformation of the central area of cylinder head fire surface is large, the stress in the connection region between cylinder head fire surface and cylinder head is large; the deformation of cylinder hole is small and in engineering allowance.
2015, 34(1): 37-41.
doi: 10.13433/j.cnki.1003-8728.2015.0108
Abstract:
The tapered roller bearings with logarithmic profile in railway generate the skew phenomenon during working. A contact model between roller and inner/outer race under skewing condition was established based on the elastic contact theory. The contact stress distribution of tapered roller was calculated numerically through the cutting-slice method. The effect of skew on the stress distribution of roller has been analyzed and the optimum crowning value in skew condition has been calculated. MATLAB simulation Results show that when the skew angle is small, stress concentration can be appropriately modified by increasing crowning value; and the large skew angle should be avoided, because the increased crowning can't alleviate roller's stress concentration.
The tapered roller bearings with logarithmic profile in railway generate the skew phenomenon during working. A contact model between roller and inner/outer race under skewing condition was established based on the elastic contact theory. The contact stress distribution of tapered roller was calculated numerically through the cutting-slice method. The effect of skew on the stress distribution of roller has been analyzed and the optimum crowning value in skew condition has been calculated. MATLAB simulation Results show that when the skew angle is small, stress concentration can be appropriately modified by increasing crowning value; and the large skew angle should be avoided, because the increased crowning can't alleviate roller's stress concentration.
2015, 34(1): 42-46.
doi: 10.13433/j.cnki.1003-8728.2015.0109
Abstract:
According to the requirement on controlling the structure acoustic radiation of the flexible base, a passive vibration isolation method which use metal rubber isolators is proposed in this paper. To analyze the dynamic performance of the metal rubber vibration isolation system on the flexible base, the ADAMS software is used together with a finite element analysis software. The dynamic frequency characteristics of the system on different materials of the flexible base, different linear stiffness, cubic nonlinear stiffness and damping of the isolator are obtained by numerical simulation using these two softwares, and the differences of vibration level with different parameters are calculated. Then the influences of these parameters on the vibration isolation performance are analyzed by comparing these results, and the method to improve the effect of vibration isolation and optimize the parameters of the system is presented.
According to the requirement on controlling the structure acoustic radiation of the flexible base, a passive vibration isolation method which use metal rubber isolators is proposed in this paper. To analyze the dynamic performance of the metal rubber vibration isolation system on the flexible base, the ADAMS software is used together with a finite element analysis software. The dynamic frequency characteristics of the system on different materials of the flexible base, different linear stiffness, cubic nonlinear stiffness and damping of the isolator are obtained by numerical simulation using these two softwares, and the differences of vibration level with different parameters are calculated. Then the influences of these parameters on the vibration isolation performance are analyzed by comparing these results, and the method to improve the effect of vibration isolation and optimize the parameters of the system is presented.
2015, 34(1): 47-50.
doi: 10.13433/j.cnki.1003-8728.2015.0110
Abstract:
To ensure the safety and reliability of 32t×42m double girder overhead crane, the local stress-strain method is adopted to estimate the fatigue life of the wire rope when bearing from the free state to the rated load. Finite element numerical algorithms are utilized to obtain the stress distribution of the wire rope, and the dangerous parts of the wire rope fatigue failure are located at the contact zone of the wire rope and the cord. The simulation value of the wire rope stress and the life are 1 060.3 MPa and 7 233.6 lifting times respectively. In order to prove above results, the calculation model of the wire rope life is established according to Manson-Coffin equation when the mean stress is considered. The fatigue life is 7 937.4 lifting times. The deviation between the numerical life value and the calculation model is 8.87%. Therefore, the calculation model is indicated suitable for predicting the wire rope fatigue life in the practical application.
To ensure the safety and reliability of 32t×42m double girder overhead crane, the local stress-strain method is adopted to estimate the fatigue life of the wire rope when bearing from the free state to the rated load. Finite element numerical algorithms are utilized to obtain the stress distribution of the wire rope, and the dangerous parts of the wire rope fatigue failure are located at the contact zone of the wire rope and the cord. The simulation value of the wire rope stress and the life are 1 060.3 MPa and 7 233.6 lifting times respectively. In order to prove above results, the calculation model of the wire rope life is established according to Manson-Coffin equation when the mean stress is considered. The fatigue life is 7 937.4 lifting times. The deviation between the numerical life value and the calculation model is 8.87%. Therefore, the calculation model is indicated suitable for predicting the wire rope fatigue life in the practical application.
2015, 34(1): 51-55.
doi: 10.13433/j.cnki.1003-8728.2015.0111
Abstract:
The coupling degree of S+3-SPS spherical mechanisms with general structure is reduced and the mechanism turns into another spherical mechanism of which the coupling degree is 0 and analytic solutions of forward position analysis are obtained by overlapping two spherical joints on the moving platform. For S+3-SPS spherical mechanism whose coupling degree is 1, by adding a branch chain virtually, the mechanism contains the above mechanism whose coupling degree is 0. A consistent equation of movement which contains only one variable is established on the base of a chain whose constrain degree is -1. Finally, using one-dimensional search method, all real forward position numerical solutions of the present mechanism are obtained. Based on the coupling degree analysis, the stylized generic numerical method is easy to accomplish computer programming and can also be applied to solve other parallel mechanisms rapidly which contain SPS type branch chain.
The coupling degree of S+3-SPS spherical mechanisms with general structure is reduced and the mechanism turns into another spherical mechanism of which the coupling degree is 0 and analytic solutions of forward position analysis are obtained by overlapping two spherical joints on the moving platform. For S+3-SPS spherical mechanism whose coupling degree is 1, by adding a branch chain virtually, the mechanism contains the above mechanism whose coupling degree is 0. A consistent equation of movement which contains only one variable is established on the base of a chain whose constrain degree is -1. Finally, using one-dimensional search method, all real forward position numerical solutions of the present mechanism are obtained. Based on the coupling degree analysis, the stylized generic numerical method is easy to accomplish computer programming and can also be applied to solve other parallel mechanisms rapidly which contain SPS type branch chain.
2015, 34(1): 56-59.
doi: 10.13433/j.cnki.1003-8728.2015.0112
Abstract:
Orientation trajectory planning plays an important role in manipulator controlling and the smoothness of interpolation orientation will directly affect the action softness of end in manipulator. In this paper, the equivalence of orientation planning was studied and rotation angular planning curve was given with controllable angular acceleration and angular velocity. In order to reduce computational complexity, the end orientation was described in quaternion instead of orientation matrix. Else, the relationship of equivalent angular and spherical linear quaternion interpolation (Slerp) was studied. In the end, for self-developed six-axis manipulator module, the orientation planning method was simulated and discussed with simulation platform LabVIEW. As showed by simulation results, the planned orientations have C2-continuous characteristic while changes smoothly.
Orientation trajectory planning plays an important role in manipulator controlling and the smoothness of interpolation orientation will directly affect the action softness of end in manipulator. In this paper, the equivalence of orientation planning was studied and rotation angular planning curve was given with controllable angular acceleration and angular velocity. In order to reduce computational complexity, the end orientation was described in quaternion instead of orientation matrix. Else, the relationship of equivalent angular and spherical linear quaternion interpolation (Slerp) was studied. In the end, for self-developed six-axis manipulator module, the orientation planning method was simulated and discussed with simulation platform LabVIEW. As showed by simulation results, the planned orientations have C2-continuous characteristic while changes smoothly.
2015, 34(1): 60-64.
doi: 10.13433/j.cnki.1003-8728.2015.0113
Abstract:
Based on the strain energy release and the principle of linear fracture mechanics, the equivalent stiffness equations of a pipe with a transverse crack whose tip direction was at any angle with respect to the axis direction of pipe were derived, then the relationship between the crack parameters and the natural frequencies was obtained. Furthermore, the change trend of the first three order natural frequencies with different crack locations, depths and angles was studied. The effectiveness of the calculation method for natural frequencies of pipe with crack is proved by the experiments.
Based on the strain energy release and the principle of linear fracture mechanics, the equivalent stiffness equations of a pipe with a transverse crack whose tip direction was at any angle with respect to the axis direction of pipe were derived, then the relationship between the crack parameters and the natural frequencies was obtained. Furthermore, the change trend of the first three order natural frequencies with different crack locations, depths and angles was studied. The effectiveness of the calculation method for natural frequencies of pipe with crack is proved by the experiments.
2015, 34(1): 65-68.
doi: 10.13433/j.cnki.1003-8728.2015.0114
Abstract:
The numerical method based on the standard solid model is developed to solve the problem of a rigid cylinder rolling with any given constant speed over a viscoelastic body. In the present method, the solution is expanded into a set of Fourier series, a so-called standard solid model is used to characterize the viscoelastic properties for the viscoelastic foundation, the three-dimensional differential constitutive equations of the viscoelastic material is used to relate Fourier coefficients, and a special boundary element is developed to handle the rolling contact boundary condition. Finally, a verification example of moving pressure on the viscoelastic half space is given to validate the methodology.
The numerical method based on the standard solid model is developed to solve the problem of a rigid cylinder rolling with any given constant speed over a viscoelastic body. In the present method, the solution is expanded into a set of Fourier series, a so-called standard solid model is used to characterize the viscoelastic properties for the viscoelastic foundation, the three-dimensional differential constitutive equations of the viscoelastic material is used to relate Fourier coefficients, and a special boundary element is developed to handle the rolling contact boundary condition. Finally, a verification example of moving pressure on the viscoelastic half space is given to validate the methodology.
2015, 34(1): 69-74.
doi: 10.13433/j.cnki.1003-8728.2015.0115
Abstract:
Based on the logistic transportation characteristics of the U-shaped line, a position encoding method which identifies the relationship between the work station and location of U-shaped line is put forward and resolved. According to the position coding method, decision variables are represented, and the learning effect and sequence-dependent tasks are described. The U-shaped assembly line balancing model based on nonlinear mixed integer programming is constructed with the objective of minimizing the number of workstations. The learning effect is quantified according to positions and the nonlinear model is linearized so as to reduce the computational complexity of the model and solve the problem quickly and efficiently. The experimental examples show that the proposed model can effectively solve the type-I and mixed-model U-shaped assembly line balancing problem which is integrated with the learning effect and sequence-dependent tasks.
Based on the logistic transportation characteristics of the U-shaped line, a position encoding method which identifies the relationship between the work station and location of U-shaped line is put forward and resolved. According to the position coding method, decision variables are represented, and the learning effect and sequence-dependent tasks are described. The U-shaped assembly line balancing model based on nonlinear mixed integer programming is constructed with the objective of minimizing the number of workstations. The learning effect is quantified according to positions and the nonlinear model is linearized so as to reduce the computational complexity of the model and solve the problem quickly and efficiently. The experimental examples show that the proposed model can effectively solve the type-I and mixed-model U-shaped assembly line balancing problem which is integrated with the learning effect and sequence-dependent tasks.
2015, 34(1): 75-80.
doi: 10.13433/j.cnki.1003-8728.2015.0116
Abstract:
To aim at the problem of CAD assembly model transforming to dynamic model in product design process, the automation assembly technology for dynamics simulation (AATFDS) was put forward, which is composed of the methodology for representing assembly relation to satisfy the requirement of automation assembly and the CAD-based automatic assembly technology. The technology was applied to the assembly model for a type decelerator. At last, by using the ability of assembly model converting to dynamics model, the assembly model was converted to a dynamics model in Autodesk Inventor block. Based on the above-mentioned, a complete dynamics model was built. The result showed the feasibility of AATFDS by comparing with the theoretical solution.
To aim at the problem of CAD assembly model transforming to dynamic model in product design process, the automation assembly technology for dynamics simulation (AATFDS) was put forward, which is composed of the methodology for representing assembly relation to satisfy the requirement of automation assembly and the CAD-based automatic assembly technology. The technology was applied to the assembly model for a type decelerator. At last, by using the ability of assembly model converting to dynamics model, the assembly model was converted to a dynamics model in Autodesk Inventor block. Based on the above-mentioned, a complete dynamics model was built. The result showed the feasibility of AATFDS by comparing with the theoretical solution.
2015, 34(1): 81-85.
doi: 10.13433/j.cnki.1003-8728.2015.0117
Abstract:
Tool wear state directly affects the product quality, productivity and cost. The tool condition monitoring system is conducive to tool preventive maintenance. The prior samples for monitoring model are limited, and the conventional neural networks recognition model has some drawbacks such running into local minimum value easily, slow convergence rate and so on. In view of these situations, a tool wear monitoring method based on Least Squares Support Vector Machine (LS-SVM) was proposed. Aiming at the systematic error existing in tool wear monitoring result to affect the precision of LS-SVM model, Kalman filters algorithm was proposed to modify the monitoring result. The cutting force signals were measured as monitoring signals. Features extracted by wavelet package transforms as model inputs. Tool wear can be got by the corrected and trained LS-SVM model. The experimental result shows that the LS-SVM model can efficiently carry out tool wear monitoring. Althrough the BP neural networks has better precision, faster learning ability and less training samples. The tool wear monitoring results modified by Kalman filter are more close to the real wear.
Tool wear state directly affects the product quality, productivity and cost. The tool condition monitoring system is conducive to tool preventive maintenance. The prior samples for monitoring model are limited, and the conventional neural networks recognition model has some drawbacks such running into local minimum value easily, slow convergence rate and so on. In view of these situations, a tool wear monitoring method based on Least Squares Support Vector Machine (LS-SVM) was proposed. Aiming at the systematic error existing in tool wear monitoring result to affect the precision of LS-SVM model, Kalman filters algorithm was proposed to modify the monitoring result. The cutting force signals were measured as monitoring signals. Features extracted by wavelet package transforms as model inputs. Tool wear can be got by the corrected and trained LS-SVM model. The experimental result shows that the LS-SVM model can efficiently carry out tool wear monitoring. Althrough the BP neural networks has better precision, faster learning ability and less training samples. The tool wear monitoring results modified by Kalman filter are more close to the real wear.
2015, 34(1): 86-89.
doi: 10.13433/j.cnki.1003-8728.2015.0118
Abstract:
Due to the incipient fault attributes of gear are not obvious, a hybrid diagnosis model for gear diagnosing based on Ensemble Empirical Mode Decomposition (EEMD) and Genetic-Support Vector Machine (GSVM) was proposed. With the EEMD method,the gear vibration signals are adaptively decomposed into a finite number of Intrinsic Mode Functions(IMF),which can alleviate mode mixing that may appear in conventional EMD method. The energy character vectors of every IMF component is calculated and the energy features extracted from a number of IMFs that contained the most dominant fault information are served as the input genetic-vectors of the support vector machine, then the fault state of the gear can be determined. The results show the high correct classification rate of the proposed method.
Due to the incipient fault attributes of gear are not obvious, a hybrid diagnosis model for gear diagnosing based on Ensemble Empirical Mode Decomposition (EEMD) and Genetic-Support Vector Machine (GSVM) was proposed. With the EEMD method,the gear vibration signals are adaptively decomposed into a finite number of Intrinsic Mode Functions(IMF),which can alleviate mode mixing that may appear in conventional EMD method. The energy character vectors of every IMF component is calculated and the energy features extracted from a number of IMFs that contained the most dominant fault information are served as the input genetic-vectors of the support vector machine, then the fault state of the gear can be determined. The results show the high correct classification rate of the proposed method.
2015, 34(1): 90-93.
doi: 10.13433/j.cnki.1003-8728.2015.0119
Abstract:
Herein, the straightness errors of large CNC machine tool guideways are investigated in the machining of workpieces. Based on the straightness errors of a CNC machine tool and a workpiece measured by an Agilent laser interferometer, a hybrid modeling method is proposed, and a real-time straightness error compensator is developed to aim at the offsetting external coordinate origin function of the FANUC CNC system. An experiment of real-time compensation and machining was conducted on a large gantry CNC machine. The results showed more than 60% of straightness errors were eliminated after compensation. However, the compensation efficiency of this method is guaranteed by the consistence of the subsequent compensation-machining travel and the error modeling travel.
Herein, the straightness errors of large CNC machine tool guideways are investigated in the machining of workpieces. Based on the straightness errors of a CNC machine tool and a workpiece measured by an Agilent laser interferometer, a hybrid modeling method is proposed, and a real-time straightness error compensator is developed to aim at the offsetting external coordinate origin function of the FANUC CNC system. An experiment of real-time compensation and machining was conducted on a large gantry CNC machine. The results showed more than 60% of straightness errors were eliminated after compensation. However, the compensation efficiency of this method is guaranteed by the consistence of the subsequent compensation-machining travel and the error modeling travel.
2015, 34(1): 94-98.
doi: 10.13433/j.cnki.1003-8728.2015.0120
Abstract:
An integrated solution for the conflicts which existed widely in customer requirements was presented. Product model base and requirement expression template were established for preventing the conflicts in the early time. The order of the conflict resolution was determined by considering the coupling factor of conflict and the important degree of customer requirement. Finally, based on the idea of parallel processing and dynamic feedback, the conflicts of customer requirements were effectively solved by using the case-based reasoning (CBR), theory of the solution of inventive problems (TRIZ) and negotiation principles in turn. A case study of the customized tunnel excavator was used to show the application of the present method.
An integrated solution for the conflicts which existed widely in customer requirements was presented. Product model base and requirement expression template were established for preventing the conflicts in the early time. The order of the conflict resolution was determined by considering the coupling factor of conflict and the important degree of customer requirement. Finally, based on the idea of parallel processing and dynamic feedback, the conflicts of customer requirements were effectively solved by using the case-based reasoning (CBR), theory of the solution of inventive problems (TRIZ) and negotiation principles in turn. A case study of the customized tunnel excavator was used to show the application of the present method.
2015, 34(1): 99-102.
doi: 10.13433/j.cnki.1003-8728.2015.0121
Abstract:
In order to improve the speed and precision for surface measurement and reconstruction, a new method is proposed based on the coordinate measurement machine CMM adaptive measurement method to reconstruct surfaces. In the measurement process, points got from the sample are fitted to calculate the next point and the measurement vector, and guide the CMM to automatically measure. After fitting the free surface model of the measured cloud, the error between points on fitting model and sample is detected and calculated. If the error is big, the actual detected points are added to reconstruct the model again. The accurate data and the elaborate surface model are obtained by detecting and updating the fitted model until the accuracy meets the requirement. Furthermore, a computer graphics display method is used to make the calculation examples process visual to verify the proposed method. The empirical results show that the accuracy of measurement and reconstruction reaches the micrometer level, and the reverse cycle for free form surface is multiply shortening down, and the algorithm robustness is high.
In order to improve the speed and precision for surface measurement and reconstruction, a new method is proposed based on the coordinate measurement machine CMM adaptive measurement method to reconstruct surfaces. In the measurement process, points got from the sample are fitted to calculate the next point and the measurement vector, and guide the CMM to automatically measure. After fitting the free surface model of the measured cloud, the error between points on fitting model and sample is detected and calculated. If the error is big, the actual detected points are added to reconstruct the model again. The accurate data and the elaborate surface model are obtained by detecting and updating the fitted model until the accuracy meets the requirement. Furthermore, a computer graphics display method is used to make the calculation examples process visual to verify the proposed method. The empirical results show that the accuracy of measurement and reconstruction reaches the micrometer level, and the reverse cycle for free form surface is multiply shortening down, and the algorithm robustness is high.
2015, 34(1): 103-106.
doi: 10.13433/j.cnki.1003-8728.2015.0122
Abstract:
Based on the mechanical winding machine, a new 4-Axis glass fiber winding machine is designed by adding the telescopic and slewing mechanism of guide-wire head and tension control mechanism,. Combing with the winding method of different mandrels and the computer controlling of the 4-Axis, the winding machine can wind common mandrels such as pressure vessel mandrel and rectangular mandrel. The ladder-type tension control method is applied to reduce the effect of tension of fibrous layers in the winding process. To improve the efficiency of mandrel design, mandrel parametric design is conducted based on Solidworks software and the frequently-used mandrel model library is also built.
Based on the mechanical winding machine, a new 4-Axis glass fiber winding machine is designed by adding the telescopic and slewing mechanism of guide-wire head and tension control mechanism,. Combing with the winding method of different mandrels and the computer controlling of the 4-Axis, the winding machine can wind common mandrels such as pressure vessel mandrel and rectangular mandrel. The ladder-type tension control method is applied to reduce the effect of tension of fibrous layers in the winding process. To improve the efficiency of mandrel design, mandrel parametric design is conducted based on Solidworks software and the frequently-used mandrel model library is also built.
2015, 34(1): 107-112.
doi: 10.13433/j.cnki.1003-8728.2015.0123
Abstract:
Based on the variant design theory, a new method by using super elliptic equations and cubic uniform B-spline construction technology to extract the sub-form's cross-sectional shape features was presented. Combining with the variant design of curved surfaces, the effects of extraction and shape optimization design were proved by an electric hand tool design case. The results were showed in the contrast research that the super elliptic extraction algorithm has less parameters, which is simple and can better extract the symmetric figure and chamfering graphics features. The cubic uniform B-spline algorithm has more parameters. Although it is a little complicated, it can be better used in extracting a variety of graphics and has wide adaptation.
Based on the variant design theory, a new method by using super elliptic equations and cubic uniform B-spline construction technology to extract the sub-form's cross-sectional shape features was presented. Combining with the variant design of curved surfaces, the effects of extraction and shape optimization design were proved by an electric hand tool design case. The results were showed in the contrast research that the super elliptic extraction algorithm has less parameters, which is simple and can better extract the symmetric figure and chamfering graphics features. The cubic uniform B-spline algorithm has more parameters. Although it is a little complicated, it can be better used in extracting a variety of graphics and has wide adaptation.
2015, 34(1): 113-117.
doi: 10.13433/j.cnki.1003-8728.2015.0124
Abstract:
This paper investigates the structural dynamics of a muffler through transfer function and modal analysis methods. The sound radiation of the muffler is computed by the finite element and boundary element coupled analysis, and compared with the sound level of exhaust noise, which illustrates that the radiation noise has an evident impact on the acoustic performance of the muffler. The shape of muffler is optimized by reducing its thickness, and consequently result shows that the optimized muffler has lower radiation sound level.
This paper investigates the structural dynamics of a muffler through transfer function and modal analysis methods. The sound radiation of the muffler is computed by the finite element and boundary element coupled analysis, and compared with the sound level of exhaust noise, which illustrates that the radiation noise has an evident impact on the acoustic performance of the muffler. The shape of muffler is optimized by reducing its thickness, and consequently result shows that the optimized muffler has lower radiation sound level.
2015, 34(1): 118-123.
doi: 10.13433/j.cnki.1003-8728.2015.0125
Abstract:
There are some difficulties to accurately identify the defects on the internal and external surfaces of the oil tube by the magnetic flux leakage(MFL) signal. Hence, this paper presents an identification method to achieve it based on support vector machines (SVM). First, the time-frequency analysis approach is employed to acquire the feature vectors of the time domain and frequency domain from MFL signal. Then, the feature vectors are used as the sample data of the proposed model of defect identification based on SVM. The parameters of this model are optimized by the Modified Adaptive Particle Swarm Optimization(MCAPSO)algorithm based on cloud theory. Finally, with the optimized model parameters and training sample data, the identification model of defect on internal and external surfaces based on SVM was established. The experimental results show that the proposed approach is effective on the identification of the oil tube defects between the internal and external surfaces, and its accuracy is higher than 90%.
There are some difficulties to accurately identify the defects on the internal and external surfaces of the oil tube by the magnetic flux leakage(MFL) signal. Hence, this paper presents an identification method to achieve it based on support vector machines (SVM). First, the time-frequency analysis approach is employed to acquire the feature vectors of the time domain and frequency domain from MFL signal. Then, the feature vectors are used as the sample data of the proposed model of defect identification based on SVM. The parameters of this model are optimized by the Modified Adaptive Particle Swarm Optimization(MCAPSO)algorithm based on cloud theory. Finally, with the optimized model parameters and training sample data, the identification model of defect on internal and external surfaces based on SVM was established. The experimental results show that the proposed approach is effective on the identification of the oil tube defects between the internal and external surfaces, and its accuracy is higher than 90%.
2015, 34(1): 124-130.
doi: 10.13433/j.cnki.1003-8728.2015.0126
Abstract:
Color display is one of the main equipment of conveying information. However, color visual effect often has differences in different devices with the same RGB value. Thus a color characteristic method is needed to transform the device-dependent RGB color space to the device-independent CIELAB color space. To solve this problem, the polynomial regression is used to describe the nonlinear relationship between RGB and CIELAB. Then, the modeling color targets and performance testing color targets are set up. During the modeling process, chaotic sequence is introduced to improve the particle swarm optimization method. Mean square error (MSE) is taken as the fitness function, and the polynomial coefficients are estimated based on the chaotic particle swarm optimization method. The proposed method is compared with the least squares method and Markov-Chain -Monte-Carlo (MCMC) based Bayesian estimation method. The results show that the accuracies of these three methods are nearly the same and the chaotic particle swarm optimization (CPSO) method is less time-consuming. The experimental results also show that the average color difference of the established model is little, and the proposed method is an effective method for display device colorimetric characterization.
Color display is one of the main equipment of conveying information. However, color visual effect often has differences in different devices with the same RGB value. Thus a color characteristic method is needed to transform the device-dependent RGB color space to the device-independent CIELAB color space. To solve this problem, the polynomial regression is used to describe the nonlinear relationship between RGB and CIELAB. Then, the modeling color targets and performance testing color targets are set up. During the modeling process, chaotic sequence is introduced to improve the particle swarm optimization method. Mean square error (MSE) is taken as the fitness function, and the polynomial coefficients are estimated based on the chaotic particle swarm optimization method. The proposed method is compared with the least squares method and Markov-Chain -Monte-Carlo (MCMC) based Bayesian estimation method. The results show that the accuracies of these three methods are nearly the same and the chaotic particle swarm optimization (CPSO) method is less time-consuming. The experimental results also show that the average color difference of the established model is little, and the proposed method is an effective method for display device colorimetric characterization.
2015, 34(1): 131-135.
doi: 10.13433/j.cnki.1003-8728.2015.0127
Abstract:
Under the different back-pressure, seven kinds of choking-cavitator with different choke pipe diameters is simulated by using the computational fluid dynamics software FLUENT, the effects of the choke pipe diameters and the back-pressure on the cavitation strength of the chocking-cavitator are studied. The results showed that the choking flow phenomena will appear in choking-cavitator having sifferent choke pipe diameters when the back-pressure was less than or equal to the value of the critical pressure. It is found that the characteristic parameters,such as pressure, volume fraction of air and Mach number, on the axis of choke pipe in the choked section upstream are not affected by the back pressure. When the homogenous gas-liquid two-phase flow was formed in the choke pipe, it is also found that the Mach number of the gas-liquid two-phase flow increase gradually from the middle section to the choked section of the choke pipe and reach the maximum value of 0.98, very closed to 1, at the maximum pressure gradient. There exist the best ranges of back-pressure to produce the strong choking cavitation for the choking-cavitator having different diameters of choke pipe. As the choke pipe diameter is increased, the best range of back pressure gradually is reduced. Increasing the choke pipe diameter or back-pressure under the choked flow conditions, the maximum pressure gradient will be also increased and the choked section will move to the choke pipe upstream.
Under the different back-pressure, seven kinds of choking-cavitator with different choke pipe diameters is simulated by using the computational fluid dynamics software FLUENT, the effects of the choke pipe diameters and the back-pressure on the cavitation strength of the chocking-cavitator are studied. The results showed that the choking flow phenomena will appear in choking-cavitator having sifferent choke pipe diameters when the back-pressure was less than or equal to the value of the critical pressure. It is found that the characteristic parameters,such as pressure, volume fraction of air and Mach number, on the axis of choke pipe in the choked section upstream are not affected by the back pressure. When the homogenous gas-liquid two-phase flow was formed in the choke pipe, it is also found that the Mach number of the gas-liquid two-phase flow increase gradually from the middle section to the choked section of the choke pipe and reach the maximum value of 0.98, very closed to 1, at the maximum pressure gradient. There exist the best ranges of back-pressure to produce the strong choking cavitation for the choking-cavitator having different diameters of choke pipe. As the choke pipe diameter is increased, the best range of back pressure gradually is reduced. Increasing the choke pipe diameter or back-pressure under the choked flow conditions, the maximum pressure gradient will be also increased and the choked section will move to the choke pipe upstream.
2015, 34(1): 136-139.
doi: 10.13433/j.cnki.1003-8728.2015.0128
Abstract:
The soft measurement method of vehicle fuel consumption, based on the radial basis neural networks, was put forward in view of the existing fuel consumption measurement's high cost, complicated structure, and difficulty to realize the on-board and real-time measurements of fuel consumption. This method based on the combustion mechanisms of engine, avoided the fuel consumption information difficult to be directly measured, and selected some parameters which affected fuel consumption and was easy to be directly measured as the input part of the measurement model. The measured data from fuel consumption test was treated as training samples and test samples of measurement model. Principal component analysis was used to improve the training speed and the measurement model can learn by itself. The computer simulation results in Matlab, compared with the measured data from fuel consumption test, showed that the measurement errors were less than 5.0%, this soft measurement method verified valid and reduced the cost and complexity of the on-board and real-time fuel consumption measurement.
The soft measurement method of vehicle fuel consumption, based on the radial basis neural networks, was put forward in view of the existing fuel consumption measurement's high cost, complicated structure, and difficulty to realize the on-board and real-time measurements of fuel consumption. This method based on the combustion mechanisms of engine, avoided the fuel consumption information difficult to be directly measured, and selected some parameters which affected fuel consumption and was easy to be directly measured as the input part of the measurement model. The measured data from fuel consumption test was treated as training samples and test samples of measurement model. Principal component analysis was used to improve the training speed and the measurement model can learn by itself. The computer simulation results in Matlab, compared with the measured data from fuel consumption test, showed that the measurement errors were less than 5.0%, this soft measurement method verified valid and reduced the cost and complexity of the on-board and real-time fuel consumption measurement.
2015, 34(1): 140-145.
doi: 10.13433/j.cnki.1003-8728.2015.0129
Abstract:
Because of the time delay in oxygen sensor feedback signal, the conventional air-fuel ratio feedback control has a time lag, which leads the deterioration of engine combustion performance includeing the acceleration transient combustion performance, power performance and exhaust emissions performance. In order to make the air-fuel ratio stay stably and rapidly in the theoretical air-fuel ratio in the acceleration transient conditions, based on the control strategy of the gasoline engine acceleration transient air-fuel ratio, the composite neural network air-fuel ratio control system was designed on the basis of the BP neural network controller (NNI identification) and based on the RBF neural network controller (NNC controller) with chaotic optimization algorithm and then computer simulation was conducted. The results show that the optimization control system can enhance the real-time feature and accuracy of the acceleration transient air-fuel ratio of the gasoline engine, and stablize the air-fuel ratio in the theoretical value in acceleration transient conditions, and thus solve the problem of hysteresis in signal transmission effectively.
Because of the time delay in oxygen sensor feedback signal, the conventional air-fuel ratio feedback control has a time lag, which leads the deterioration of engine combustion performance includeing the acceleration transient combustion performance, power performance and exhaust emissions performance. In order to make the air-fuel ratio stay stably and rapidly in the theoretical air-fuel ratio in the acceleration transient conditions, based on the control strategy of the gasoline engine acceleration transient air-fuel ratio, the composite neural network air-fuel ratio control system was designed on the basis of the BP neural network controller (NNI identification) and based on the RBF neural network controller (NNC controller) with chaotic optimization algorithm and then computer simulation was conducted. The results show that the optimization control system can enhance the real-time feature and accuracy of the acceleration transient air-fuel ratio of the gasoline engine, and stablize the air-fuel ratio in the theoretical value in acceleration transient conditions, and thus solve the problem of hysteresis in signal transmission effectively.
Modeling and Optimization of Twist Beam Rear Suspension with Watt's Link and Full-vehicle Simulation
2015, 34(1): 146-150.
doi: 10.13433/j.cnki.1003-8728.2015.0130
Abstract:
In view of the lateral force oversteer problem of twist beam suspensions, the model of this kind suspension with Watt's link is built based on the scheme of twist beam equipped with Watt's link and ADAMS software. Through the computer simulations of the two types of rear suspension in condition of lateral force, the twist beam rear suspension with Watt's link becomes lateral force understeer which proves that the suspension with Watt's link could improve the C characters of the twist beam rear suspension. In order to obtain better toe & camber features, structural parameters of twist beam rear suspension with Watt's link are optimized in use of ADAMS/Insight.
In view of the lateral force oversteer problem of twist beam suspensions, the model of this kind suspension with Watt's link is built based on the scheme of twist beam equipped with Watt's link and ADAMS software. Through the computer simulations of the two types of rear suspension in condition of lateral force, the twist beam rear suspension with Watt's link becomes lateral force understeer which proves that the suspension with Watt's link could improve the C characters of the twist beam rear suspension. In order to obtain better toe & camber features, structural parameters of twist beam rear suspension with Watt's link are optimized in use of ADAMS/Insight.
2015, 34(1): 151-154.
doi: 10.13433/j.cnki.1003-8728.2015.0131
Abstract:
The tailpipe noise of some automotive exhaust system was simulated in some speed of engine with gt-power software. Several improved schemes of exhaust system muffler were put forward, and then choose the best one from them. Based on the best scheme, the impact of a few factors changes on noise elimination was analyzed, and ideal parameter scheme was selected. Finally, main indexes such as power loss and insertion loss all reach a preferable level; the tailpipe noise is decreased greatly. It is concluded that the lengths of perforated pipe and insert pipe, and the volume of expansion chamber have a great impact on noise elimination.
The tailpipe noise of some automotive exhaust system was simulated in some speed of engine with gt-power software. Several improved schemes of exhaust system muffler were put forward, and then choose the best one from them. Based on the best scheme, the impact of a few factors changes on noise elimination was analyzed, and ideal parameter scheme was selected. Finally, main indexes such as power loss and insertion loss all reach a preferable level; the tailpipe noise is decreased greatly. It is concluded that the lengths of perforated pipe and insert pipe, and the volume of expansion chamber have a great impact on noise elimination.
2015, 34(1): 155-159.
doi: 10.13433/j.cnki.1003-8728.2015.0132
Abstract:
In order to study the influence of torsion mode, bending mode and umbrella mode of the wheelset on the stability of high-speed bogie, the vehicle-track system dynamic model was established in this paper. The wheelset structures were considered as rigid body and flexible body respectively in the dynamic model. The lateral stability of the bogies was assessed by the RMS values of the bogie frame lateral acceleration and the sum of the wheel-rail guiding force according to UIC518. The results show as follows: The 1st symmetric and antisymmetric bending modes of wheelset are the main factors affecting the lateral stability of high-speed bogie. The RMS values of the bogie frame lateral acceleration of the flexible and rigid wheelset models are 4.69 m/s2 and 4.14 m/s2, and the RMS values of the sum of the wheel-rail guiding force are 16.35 kN and 14.79 kN respectively when the vehicle running speed is 500 km/h. The modal frequencies of wheelset decrease with the decreasing of the axle stiffness. The RMS values of the lateral acceleration of the bogie frame and the sum of the wheel-rail guiding force increase with the decreasing of modal frequencies of wheelset. So, the critical speed decreases with the decreasing of the axle stiffness. As a result, the stiffness of the axle must be taken into consideration during the lightweight design of wheelsets.
In order to study the influence of torsion mode, bending mode and umbrella mode of the wheelset on the stability of high-speed bogie, the vehicle-track system dynamic model was established in this paper. The wheelset structures were considered as rigid body and flexible body respectively in the dynamic model. The lateral stability of the bogies was assessed by the RMS values of the bogie frame lateral acceleration and the sum of the wheel-rail guiding force according to UIC518. The results show as follows: The 1st symmetric and antisymmetric bending modes of wheelset are the main factors affecting the lateral stability of high-speed bogie. The RMS values of the bogie frame lateral acceleration of the flexible and rigid wheelset models are 4.69 m/s2 and 4.14 m/s2, and the RMS values of the sum of the wheel-rail guiding force are 16.35 kN and 14.79 kN respectively when the vehicle running speed is 500 km/h. The modal frequencies of wheelset decrease with the decreasing of the axle stiffness. The RMS values of the lateral acceleration of the bogie frame and the sum of the wheel-rail guiding force increase with the decreasing of modal frequencies of wheelset. So, the critical speed decreases with the decreasing of the axle stiffness. As a result, the stiffness of the axle must be taken into consideration during the lightweight design of wheelsets.
2015, 34(1): 160-164.
doi: 10.13433/j.cnki.1003-8728.2015.0133
Abstract:
Based on the LS-SVM algorithm, a sound quality evaluation (SQE) model of vehicle interior noise during acceleration is presented in this paper. The objective psychoacoustic parameters and subjective annoyance results are used as the input and output of the model, respectively. Based on the correlation analysis and the significance test, some parameters, such as loudness, sharpness, roughness, AI index and A-weighted sound pressure level, are selected as variables for LS-SVM SQE modeling. The prediction results of unknown samples are high correlated with the subjective annoyance results, which are better than those from the multiple linear regression method. The proposed LS-SVM SQE model, which has performed good generalization ability, can be applied in the sound quality prediction of vehicle interior noise under accelerating condition.
Based on the LS-SVM algorithm, a sound quality evaluation (SQE) model of vehicle interior noise during acceleration is presented in this paper. The objective psychoacoustic parameters and subjective annoyance results are used as the input and output of the model, respectively. Based on the correlation analysis and the significance test, some parameters, such as loudness, sharpness, roughness, AI index and A-weighted sound pressure level, are selected as variables for LS-SVM SQE modeling. The prediction results of unknown samples are high correlated with the subjective annoyance results, which are better than those from the multiple linear regression method. The proposed LS-SVM SQE model, which has performed good generalization ability, can be applied in the sound quality prediction of vehicle interior noise under accelerating condition.
