2001 Vol.14(1)
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2001, 15(1).
Abstract:
A flat neural networ is designed for the on-line state prediction of engine. To reduce the computational cost of weight matrix, a fast recursive algorithm is derived according to the pseudoinverse formual of the partition matrix. Furthermore the forgettin factor approach is introduced to improve predictive accuracy and robustness of the model. The experiment results indicate that the improved neural netword is of good accuracy and strong robustness in prediction, and can apply for the on-line prediction of nonlinear multi input multi output systems like vehicle engines.
A flat neural networ is designed for the on-line state prediction of engine. To reduce the computational cost of weight matrix, a fast recursive algorithm is derived according to the pseudoinverse formual of the partition matrix. Furthermore the forgettin factor approach is introduced to improve predictive accuracy and robustness of the model. The experiment results indicate that the improved neural netword is of good accuracy and strong robustness in prediction, and can apply for the on-line prediction of nonlinear multi input multi output systems like vehicle engines.
2001, 15(1).
Abstract:
Hydraulic counter-pressure deep drawing of truncated conical part is numerically simulated with MARK and the nature of increasing the forming limit in this process is searched. The effects of blank holding force and chamber pressure on forming results are investigated by experiments and ,as a result, truncated conical parts with large drawing ratio are successfully fromed in single step with this drawing method.
Hydraulic counter-pressure deep drawing of truncated conical part is numerically simulated with MARK and the nature of increasing the forming limit in this process is searched. The effects of blank holding force and chamber pressure on forming results are investigated by experiments and ,as a result, truncated conical parts with large drawing ratio are successfully fromed in single step with this drawing method.
2001, 15(1).
Abstract:
Vertical rigidity of the space self-adaptive φ530 high rigidity mill is calculated by applying the boundary element method(BEM)of three-dimension elastic contact problem, which can update the existed deforming separation calculating theory and corresponding methods of material mechanics, elastic mechanics and finite element method. The method has less hypotheses and stronger synthesis in contact-type calculating model. The advantages of the method are high calculating rate,high calculating accuracy, etc..
Vertical rigidity of the space self-adaptive φ530 high rigidity mill is calculated by applying the boundary element method(BEM)of three-dimension elastic contact problem, which can update the existed deforming separation calculating theory and corresponding methods of material mechanics, elastic mechanics and finite element method. The method has less hypotheses and stronger synthesis in contact-type calculating model. The advantages of the method are high calculating rate,high calculating accuracy, etc..
2001, 15(1).
Abstract:
The kinetic precision of transmission chain is a key problem in the research of gear cutting machine transmission system. The traditional point of view is to consider the transmission chain as a geometrical meshing system,thus it is deemed that the kinetic precision of the transmission chain only depends on the manufacturing and assembly errors of its transmission parts. But further research reveals that the kinetic precision of transmission system is closely related with the system dynamic effects.Therefore, from the dynamic point of view, it is discerned that not only deems the transmission chain as a geometrical meshing system but also considers it as a dynamic system performing with torsional vibration. On the basis of analyses and processes of measuring data of samples from tests of cutting machine's kinetic precision of transmission chain, the results represent that the influences of dynamic characteristics of the transmission system on its kinetic precision is non-negligible. Experimental methods for discerming the transfer function of torsional vibration of gear transmission system and experimental results have been given.
The kinetic precision of transmission chain is a key problem in the research of gear cutting machine transmission system. The traditional point of view is to consider the transmission chain as a geometrical meshing system,thus it is deemed that the kinetic precision of the transmission chain only depends on the manufacturing and assembly errors of its transmission parts. But further research reveals that the kinetic precision of transmission system is closely related with the system dynamic effects.Therefore, from the dynamic point of view, it is discerned that not only deems the transmission chain as a geometrical meshing system but also considers it as a dynamic system performing with torsional vibration. On the basis of analyses and processes of measuring data of samples from tests of cutting machine's kinetic precision of transmission chain, the results represent that the influences of dynamic characteristics of the transmission system on its kinetic precision is non-negligible. Experimental methods for discerming the transfer function of torsional vibration of gear transmission system and experimental results have been given.
2001, 15(1).
Abstract:
The nonlinear properties of rotating machinery vibration signals are presented. The relationship between faults and quadratic phase coupling is discussed. The mechanism that gives rise to quadratic phase coupling is analyzed, and the coupling models are summarized. As a result, higher order spectra analysis is introduced into fault diagnosis of rotors. A brief review of the properties of higher order spectra is presented. Furthermore, the bicoherence spectrum is employed to extract the features that signify the machinery condition. Experiments show that bicoherence spectrum patterns of different faults are quite different, so it is proposed to identify the faults in rotors.
The nonlinear properties of rotating machinery vibration signals are presented. The relationship between faults and quadratic phase coupling is discussed. The mechanism that gives rise to quadratic phase coupling is analyzed, and the coupling models are summarized. As a result, higher order spectra analysis is introduced into fault diagnosis of rotors. A brief review of the properties of higher order spectra is presented. Furthermore, the bicoherence spectrum is employed to extract the features that signify the machinery condition. Experiments show that bicoherence spectrum patterns of different faults are quite different, so it is proposed to identify the faults in rotors.
2001, 15(1).
Abstract:
The accessibility of coordinate measuring machines (CMMs) in dimensional is studied. The problem of computing the glodbal accessibility cone is solved using a method of angle representation. Otherwise, the length and volume of probe are considered sufficiently so that all the feasible probe orientations could be determined for the inspection of a workpiece when a touch trigger probe is used and the shortcoming of abstracting a probe as an infinite half-line could be overcome completely. In the end, an example is given to explain the method.
The accessibility of coordinate measuring machines (CMMs) in dimensional is studied. The problem of computing the glodbal accessibility cone is solved using a method of angle representation. Otherwise, the length and volume of probe are considered sufficiently so that all the feasible probe orientations could be determined for the inspection of a workpiece when a touch trigger probe is used and the shortcoming of abstracting a probe as an infinite half-line could be overcome completely. In the end, an example is given to explain the method.
2001, 15(1).
Abstract:
In order to realize the feedback control for variable polarity plasma arc welding (VPPAW) formation in the welding process, the geometrical sizes of the keyhole image must be extracted. With the properties of multiscale edge through the wavelet theory, the edge points were detected by getting the maximum modules of the gradient vector in the dircetion towards which the gradient vector points in the image plane. At coarse scales,the local maxima of modules have different positions and only detected the sharp edge. At fine scale, there are many maxima created by the image noise, The best scale where the edges are well discriminated from noises is discussed by the multiscale transform. At last, a new method of peak analysis for threshold selection is provided. It is based on the wavelet transform which provides a multiscale analysis of the information of the histogram. Many experiments show these ways are effective for the keyhole image to get the geometry parameters of the keyhole in the real-time VPPAW image processing.
In order to realize the feedback control for variable polarity plasma arc welding (VPPAW) formation in the welding process, the geometrical sizes of the keyhole image must be extracted. With the properties of multiscale edge through the wavelet theory, the edge points were detected by getting the maximum modules of the gradient vector in the dircetion towards which the gradient vector points in the image plane. At coarse scales,the local maxima of modules have different positions and only detected the sharp edge. At fine scale, there are many maxima created by the image noise, The best scale where the edges are well discriminated from noises is discussed by the multiscale transform. At last, a new method of peak analysis for threshold selection is provided. It is based on the wavelet transform which provides a multiscale analysis of the information of the histogram. Many experiments show these ways are effective for the keyhole image to get the geometry parameters of the keyhole in the real-time VPPAW image processing.
2001, 15(1).
Abstract:
The contact condition, stress-strain field and shape optimization of thread profile for drillpipe connector are investigated by semi-analytical finite element method for contact problem in order to enhance the load capacity and reduce the fatigue accident of drillpipe thread compounds.
The contact condition, stress-strain field and shape optimization of thread profile for drillpipe connector are investigated by semi-analytical finite element method for contact problem in order to enhance the load capacity and reduce the fatigue accident of drillpipe thread compounds.
2001, 15(1).
Abstract:
The modeling of the rotor-support system of a typical centrifuge is discussed. The impedance matching method, cooperating with Riccati transfer matrix method and modal analysis method are adopted to calculate its dynamic characteristics. The influences of the main parts to the critical speeds are analyzed. Based on the analysis, a critical speed in the operating speed range is tuned successfully, and thus the dynamic characteristics of the centrifuge are much improved.
The modeling of the rotor-support system of a typical centrifuge is discussed. The impedance matching method, cooperating with Riccati transfer matrix method and modal analysis method are adopted to calculate its dynamic characteristics. The influences of the main parts to the critical speeds are analyzed. Based on the analysis, a critical speed in the operating speed range is tuned successfully, and thus the dynamic characteristics of the centrifuge are much improved.
2001, 15(1).
Abstract:
A multi-agent computer aided assembly process planning system (MCAAPP) for ship hull is presented. The system includes system framework, global facilitator, the macro agent structure, agent communication language, agent-oriented programming language, knowledge representation and reasoning strategy. The system can produce the technological file and technological quota, which can satisfy the production needs of factory.
A multi-agent computer aided assembly process planning system (MCAAPP) for ship hull is presented. The system includes system framework, global facilitator, the macro agent structure, agent communication language, agent-oriented programming language, knowledge representation and reasoning strategy. The system can produce the technological file and technological quota, which can satisfy the production needs of factory.
2001, 15(1).
Abstract:
With the viewpoint of integration all phases of product life cycle, product disassembly problem is discussed.An kind of logical net methodology for product disassembly model, such as logical net methodology for product disassembly medeling is presented. An channel of converting product assembly model into disassembly model, such as logical net, is proposed, and the minimization cost problem and is linear programming model are given.
With the viewpoint of integration all phases of product life cycle, product disassembly problem is discussed.An kind of logical net methodology for product disassembly model, such as logical net methodology for product disassembly medeling is presented. An channel of converting product assembly model into disassembly model, such as logical net, is proposed, and the minimization cost problem and is linear programming model are given.
2001, 15(1).
Abstract:
The use of evaluation criteria, such as the global conditioning index, global payload index, and global stiffness index, to select the link lengths of spherical 3-DOF parallel manipulator with prismatic actuators and analyze their operational performance is concerned. The technique has wide application to the design of the serial and panrallel robots.
The use of evaluation criteria, such as the global conditioning index, global payload index, and global stiffness index, to select the link lengths of spherical 3-DOF parallel manipulator with prismatic actuators and analyze their operational performance is concerned. The technique has wide application to the design of the serial and panrallel robots.
2001, 15(1).
Abstract:
Solidification microstructure and mechanical property are explored. Furthermore, tensile fracture and microstructure are analyzed by using SEM and JXA-840A electron-probe. The results indicate that SiC particles in SiCp/ZA27 composite are mainly distributed on interfaces or between dendrites and surrounded by primary αphase. The dendrite of αphase is fined by SiCp.The tensile strength at room temperature decreases with the increasing of SiCp addition. The tensile strength at elevated temperature increases with the addition of SiCp. The fracture of SiCp/ZA27 composites is the mixture of tough and brittle fracture. The carck is prone to extend along the interface and the region of dispersed shrinkage.
Solidification microstructure and mechanical property are explored. Furthermore, tensile fracture and microstructure are analyzed by using SEM and JXA-840A electron-probe. The results indicate that SiC particles in SiCp/ZA27 composite are mainly distributed on interfaces or between dendrites and surrounded by primary αphase. The dendrite of αphase is fined by SiCp.The tensile strength at room temperature decreases with the increasing of SiCp addition. The tensile strength at elevated temperature increases with the addition of SiCp. The fracture of SiCp/ZA27 composites is the mixture of tough and brittle fracture. The carck is prone to extend along the interface and the region of dispersed shrinkage.
2001, 15(1).
Abstract:
In order to improve the anti-jamming performance of a vortex precession meter, the disciplinarian of the vortex precession and the mechanism of hydrodynamic oscillation inside the vortex precession meter are numerically investigated by using the large eddy simulation. The results show that the periodical eccentric motion of the vortexes initiates a hydrodynamic oscillation inside the vortex precession meter. The visualized time dependent flow fields indicate that the pressures at axisymmetric points oscillate with a same intensity and frequency but 180°phase shift. By using differential sensing technique, a new prototype of double-double-sensor vortex precession meter, aimed to improve measurement accuracy, is developed.
In order to improve the anti-jamming performance of a vortex precession meter, the disciplinarian of the vortex precession and the mechanism of hydrodynamic oscillation inside the vortex precession meter are numerically investigated by using the large eddy simulation. The results show that the periodical eccentric motion of the vortexes initiates a hydrodynamic oscillation inside the vortex precession meter. The visualized time dependent flow fields indicate that the pressures at axisymmetric points oscillate with a same intensity and frequency but 180°phase shift. By using differential sensing technique, a new prototype of double-double-sensor vortex precession meter, aimed to improve measurement accuracy, is developed.
2001, 15(1).
Abstract:
Numerical simulation of extrusion process of aluminium tube is dealt with using the finite element polycrystal model. The non-uniformity in plastic anisortopies of aluminium extruded tubes through the wall thickness is investigated.
Numerical simulation of extrusion process of aluminium tube is dealt with using the finite element polycrystal model. The non-uniformity in plastic anisortopies of aluminium extruded tubes through the wall thickness is investigated.
2001, 15(1).
Abstract:
An effective controller and compensator is designed by using the system identification and constant structure theory to realize the effective control. The experimental results indicate the extraneous torque can be decreased by 90% and the characteristics can be improved greatly by meaans of this kind of method.
An effective controller and compensator is designed by using the system identification and constant structure theory to realize the effective control. The experimental results indicate the extraneous torque can be decreased by 90% and the characteristics can be improved greatly by meaans of this kind of method.
2001, 15(1).
Abstract:
The motion planning of multiple mobile robots undertaking individual tasks in the same environment is studied. A motion planning method based on neural networks is proposed. By storing fuzzy rules in neural networks the method can fully make use of the association ability and high processing speed of neural networks to make robots avoid collisions with other objects in real time. Compared with rules method, the method can not only avoid building a large and complex rules base but also make robots avoid collisions and conflicts at higher speed and with higher intelligence.
The motion planning of multiple mobile robots undertaking individual tasks in the same environment is studied. A motion planning method based on neural networks is proposed. By storing fuzzy rules in neural networks the method can fully make use of the association ability and high processing speed of neural networks to make robots avoid collisions with other objects in real time. Compared with rules method, the method can not only avoid building a large and complex rules base but also make robots avoid collisions and conflicts at higher speed and with higher intelligence.
2001, 15(1).
Abstract:
The effects of structure elastic deformations of wheelset and track on creep forces of wheel and rail are investigated. Finite element method is used to calculate the influence coefficients expressing the relations between structure elastic deformations of wheelset and track and the corresponding loads in the rolling direction and the lateral direction of wheelset, respectively. The influence coefficients of wheelset and track are used to revise some of the influence coefficients obtained with the formula of Bossinesq and Cerruti in Kalker's theory of three-dimensional elastic bodies in rolling contact with non-Hertzian form. The theory of Kalker and the modified theory of Kalker are respectively employed to analyze creep forces of wheelset and track. The numerical results obtained show a great influence of structure elastic deformations of wheelset and track on the creep forces. Therfore it is not reasonable that wheel and rail are treated as elastic half space in the analysis of wheel and rail in rolling contact, and the present theories of rolling contact based on the assumption of elastic half space need to be further improved.
The effects of structure elastic deformations of wheelset and track on creep forces of wheel and rail are investigated. Finite element method is used to calculate the influence coefficients expressing the relations between structure elastic deformations of wheelset and track and the corresponding loads in the rolling direction and the lateral direction of wheelset, respectively. The influence coefficients of wheelset and track are used to revise some of the influence coefficients obtained with the formula of Bossinesq and Cerruti in Kalker's theory of three-dimensional elastic bodies in rolling contact with non-Hertzian form. The theory of Kalker and the modified theory of Kalker are respectively employed to analyze creep forces of wheelset and track. The numerical results obtained show a great influence of structure elastic deformations of wheelset and track on the creep forces. Therfore it is not reasonable that wheel and rail are treated as elastic half space in the analysis of wheel and rail in rolling contact, and the present theories of rolling contact based on the assumption of elastic half space need to be further improved.
2001, 15(1).
Abstract:
The spanning tree method of identifying isomorphism and topological symmetry to planar kinematic chain with multiple joint is presented. Directly using the kinematic-chain's structural graph in the mechanism motion sketch or its inversion, the connected relations of components and joints can be presented through the spanning tree constructed by Depth-First traversal the graph and the distribution of back-edge. Then, whether two graph isomorphism and components'topological symmertry can be identified through comparing the structural characteristic of spanning tree and the distribution characteristic of back-edge. The study shows that the method is effective,directly perceptible, simple and easily dealt with by computer.
The spanning tree method of identifying isomorphism and topological symmetry to planar kinematic chain with multiple joint is presented. Directly using the kinematic-chain's structural graph in the mechanism motion sketch or its inversion, the connected relations of components and joints can be presented through the spanning tree constructed by Depth-First traversal the graph and the distribution of back-edge. Then, whether two graph isomorphism and components'topological symmertry can be identified through comparing the structural characteristic of spanning tree and the distribution characteristic of back-edge. The study shows that the method is effective,directly perceptible, simple and easily dealt with by computer.
2001, 15(1).
Abstract:
Castex(continous cast and extrusion)is a latest metallurgical technology. Making of AS wire(aluminum-clad steel wire) by Castex is an advanced bonding technology of bimetal.In order to study the deformation character of AS wire the numerical simulation is performed with FE method. From the simulation result the following conclusions are obtained:① The simulation is carried out sequentially in three zones:initial extrusion, extrusion,cavity-filling and bonding.②In the first zone the shearing deformation governs the whold zone, while in that of cavity-filling,the deformation mainly concentrates on transition arc of the concave mould. In addition, in the last zone, the dominant deformation lies at the boundary of concave mould, surface of steel wire and entry of sizing band. Due to the movement of steel wire, the direction of shear stress on its surface is opposite to that on the boundary of concave die.
Castex(continous cast and extrusion)is a latest metallurgical technology. Making of AS wire(aluminum-clad steel wire) by Castex is an advanced bonding technology of bimetal.In order to study the deformation character of AS wire the numerical simulation is performed with FE method. From the simulation result the following conclusions are obtained:① The simulation is carried out sequentially in three zones:initial extrusion, extrusion,cavity-filling and bonding.②In the first zone the shearing deformation governs the whold zone, while in that of cavity-filling,the deformation mainly concentrates on transition arc of the concave mould. In addition, in the last zone, the dominant deformation lies at the boundary of concave mould, surface of steel wire and entry of sizing band. Due to the movement of steel wire, the direction of shear stress on its surface is opposite to that on the boundary of concave die.
2001, 15(1).
Abstract:
In the extrusion of shapes with flat-faced die ,the proper design of die land is of critical importance in avoiding the generations of geometry defects. A methodology for the design of die land, which consists of a simulation-adjustment iteration, is proposed. The metal flow in extrusion is simulated by the three dimensional finite element method and the die land is adjusted according to the simulation result. Both the formulae for adjustment of the die land and the criterion for the judgment of proper die land are suggested. The extrusion of an L-secion shape is chosen as the computational example and the result is compared with the industrial design.
In the extrusion of shapes with flat-faced die ,the proper design of die land is of critical importance in avoiding the generations of geometry defects. A methodology for the design of die land, which consists of a simulation-adjustment iteration, is proposed. The metal flow in extrusion is simulated by the three dimensional finite element method and the die land is adjusted according to the simulation result. Both the formulae for adjustment of the die land and the criterion for the judgment of proper die land are suggested. The extrusion of an L-secion shape is chosen as the computational example and the result is compared with the industrial design.
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