2001 Vol.14(2)
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2001, 15(2).
Abstract:
A method for automatic detection of burning through of short circuit CO2 arc welding is presented. It is based on the extraction of arc signal features as well as classification of the obtained features using self-organize feature map (SOM) neural networks in order to get the weld quality information, for example, to determine if there is defect in the product. This is important for the on-line monitoring of weld quality especially in robotic welding and lay the foundation for the further real-time control of weld quality.
A method for automatic detection of burning through of short circuit CO2 arc welding is presented. It is based on the extraction of arc signal features as well as classification of the obtained features using self-organize feature map (SOM) neural networks in order to get the weld quality information, for example, to determine if there is defect in the product. This is important for the on-line monitoring of weld quality especially in robotic welding and lay the foundation for the further real-time control of weld quality.
2001, 15(2).
Abstract:
The dynamic responses of roller gear indexing cam mechanism are investigated. With applying Lagarange equation and Gear method, motion equations of this mechanism including clearance, motor characteristic, torsion flexibility are developed and solved. The resuls show that clearance affects primarily the response on turret, and has little effects on the responses on rotary table. At the same time, the velocity flucturaion of motor shaft is not serious for the existence of inertia of reducer, and the high frequency of velocity fluctuation of camshaft is related with the torsion stiffness of shaft and the clearance between pairs.
The dynamic responses of roller gear indexing cam mechanism are investigated. With applying Lagarange equation and Gear method, motion equations of this mechanism including clearance, motor characteristic, torsion flexibility are developed and solved. The resuls show that clearance affects primarily the response on turret, and has little effects on the responses on rotary table. At the same time, the velocity flucturaion of motor shaft is not serious for the existence of inertia of reducer, and the high frequency of velocity fluctuation of camshaft is related with the torsion stiffness of shaft and the clearance between pairs.
2001, 15(2).
Abstract:
The solid and finite element model of metal pushing type continuously variable transmission are established at speed ration of I=0.5 and I=2.0. In order to solve the problem of the complicated of structure, the node-node rod discrete finite element model is put forward and the whole system is simplified and established. The natural frequency and mode shape of system are solved by iterative Lanczos-reduce method for sensitivity analysis in finite element model. The new method and the result can be used to improve the smoothness of the variable transmission system and to propose the theory for reducing noise at operation.
The solid and finite element model of metal pushing type continuously variable transmission are established at speed ration of I=0.5 and I=2.0. In order to solve the problem of the complicated of structure, the node-node rod discrete finite element model is put forward and the whole system is simplified and established. The natural frequency and mode shape of system are solved by iterative Lanczos-reduce method for sensitivity analysis in finite element model. The new method and the result can be used to improve the smoothness of the variable transmission system and to propose the theory for reducing noise at operation.
2001, 15(2).
Abstract:
A simulation system for five-axis NC machining using general cutting tools is presented. This system differs from other simulation system in that it not only focuses on the geometric simulation but also focuses on the collision detection which is usually not included in NC machining simulation. Besides all of these, estimating cutting forces is also discussed. In order to obtain high efficiency, all algorithms use swept volume modeling technique, so the simulation system is compact and can be performed efficiently.
A simulation system for five-axis NC machining using general cutting tools is presented. This system differs from other simulation system in that it not only focuses on the geometric simulation but also focuses on the collision detection which is usually not included in NC machining simulation. Besides all of these, estimating cutting forces is also discussed. In order to obtain high efficiency, all algorithms use swept volume modeling technique, so the simulation system is compact and can be performed efficiently.
2001, 15(2).
Abstract:
Technology of movement and knowledge guidance in virtual assembly is presented. The designer can move the mechanical part precisely under the movement guidance. The movement guidance is implemented based on constraint recognition and assembly degree of freedom analysis. A multi-hierarchy knowledge base is built to represent the assembly knowledge and information. The virtual assembly system judges the requirement of the designer based on the context of design task and searches for the useful knowledge and information, which can be provided to the designer in a natural way.
Technology of movement and knowledge guidance in virtual assembly is presented. The designer can move the mechanical part precisely under the movement guidance. The movement guidance is implemented based on constraint recognition and assembly degree of freedom analysis. A multi-hierarchy knowledge base is built to represent the assembly knowledge and information. The virtual assembly system judges the requirement of the designer based on the context of design task and searches for the useful knowledge and information, which can be provided to the designer in a natural way.
2001, 15(2).
Abstract:
Kinematics of a-3RPS parallel pyramid manipulator are investigated by principal screw. Firstly, the principal screws are identified by quadric degeneration. The planar conics representing the relations between the pitches and the three linear inputs are described, and the three-dimensional distribution of the axes of all the twists in illustrated. Finally, a unmerical example is given successfullly.
Kinematics of a-3RPS parallel pyramid manipulator are investigated by principal screw. Firstly, the principal screws are identified by quadric degeneration. The planar conics representing the relations between the pitches and the three linear inputs are described, and the three-dimensional distribution of the axes of all the twists in illustrated. Finally, a unmerical example is given successfullly.
2001, 15(2).
Abstract:
Based on analyzing various factors influencing milled surface topography, firstly, a generalized model for milled surface topography is proposed. Secondly, using the principles of transformation matrix and vector operation, the trajectory equation of cutting edge relative to workpiece is derived. Then, a three-dimensional topography simulation algorithm is constructed through dividing the workpiece into reqular grids. Finally, taking the peripheral milling process as an example, the generalized model is simplified, and the corresponding simulation examples are given. The results indicate that it is very efficient for the genrealized model to be used to analyze and simulated the peripherally milled surface topography.
Based on analyzing various factors influencing milled surface topography, firstly, a generalized model for milled surface topography is proposed. Secondly, using the principles of transformation matrix and vector operation, the trajectory equation of cutting edge relative to workpiece is derived. Then, a three-dimensional topography simulation algorithm is constructed through dividing the workpiece into reqular grids. Finally, taking the peripheral milling process as an example, the generalized model is simplified, and the corresponding simulation examples are given. The results indicate that it is very efficient for the genrealized model to be used to analyze and simulated the peripherally milled surface topography.
2001, 15(2).
Abstract:
A general model of flexible isolation systems which involves both the passive and active control factors is established by inserting actuators into an passive isolation system. And the power flow transmission function in such a system as with multi-disturbance, multi-mounts, passive isolators and actuators is deduced. By means of the numerical simulation method, the influence of actuators on power flow transmission characteristic is studied. And as a conclusion, the passive-active synthetic control strategy of power flow is summarized.
A general model of flexible isolation systems which involves both the passive and active control factors is established by inserting actuators into an passive isolation system. And the power flow transmission function in such a system as with multi-disturbance, multi-mounts, passive isolators and actuators is deduced. By means of the numerical simulation method, the influence of actuators on power flow transmission characteristic is studied. And as a conclusion, the passive-active synthetic control strategy of power flow is summarized.
2001, 15(2).
Abstract:
The possibility of pressure control with the structural change of a safety valve is investigated. Safety valve is commonly used as safety devices for numerous applications which include boilers, ships, industrial plants, and piping. Setting and stopping pressures of a safety valve, pset and psto, are traditionally adjusted with a flne tuning of seat ring and valve ring heights, hsr and hvr. However, it is mot easy to achieve the proper setting and stopping pressures of a safety valve in practice. The depth of inside and outside grooves in a valve, di and do are modified and their effects on setting and stpping pressures of a safety vlave are tested. The most appropriate values appear 1.0 mm in di and 0.5~1.0 mm in do, respectively. The valve ring height, hvr, shows that the best results can be achieved at 2.3mm for setting pressures of 0.1~0.4 Mpa and 1.0 mm for setting pressures of 0.5~1.0 Mpa.The stopping pressures increases with the increase of seat ring height, hsr, upto certain hsr value and then becomes independent to the seat ring height. This implies that there exists valve are adjusted with the seat ring and valve ring hejghts. This study, however, demonstrated that the modification of value grooves also changes setting and stopping pressures of a safety valve. Therefore, the proper selection in dimensions of the inside and outside grooves should be considered for the safety valve design.
The possibility of pressure control with the structural change of a safety valve is investigated. Safety valve is commonly used as safety devices for numerous applications which include boilers, ships, industrial plants, and piping. Setting and stopping pressures of a safety valve, pset and psto, are traditionally adjusted with a flne tuning of seat ring and valve ring heights, hsr and hvr. However, it is mot easy to achieve the proper setting and stopping pressures of a safety valve in practice. The depth of inside and outside grooves in a valve, di and do are modified and their effects on setting and stpping pressures of a safety vlave are tested. The most appropriate values appear 1.0 mm in di and 0.5~1.0 mm in do, respectively. The valve ring height, hvr, shows that the best results can be achieved at 2.3mm for setting pressures of 0.1~0.4 Mpa and 1.0 mm for setting pressures of 0.5~1.0 Mpa.The stopping pressures increases with the increase of seat ring height, hsr, upto certain hsr value and then becomes independent to the seat ring height. This implies that there exists valve are adjusted with the seat ring and valve ring hejghts. This study, however, demonstrated that the modification of value grooves also changes setting and stopping pressures of a safety valve. Therefore, the proper selection in dimensions of the inside and outside grooves should be considered for the safety valve design.
2001, 15(2).
Abstract:
As mechanical dither is widely applied to reduce frequency "Lock-in" of RLG (ring laser gyroscope) that is based on the principle proposed by Sagnac in 1913, it is necessary to know the recent development in the field. The proper design of dither mechanism that decides the effect of bias to some extent is discussed. The proper dither signal and its control have a direct influence on dither efficiency. Real, stable and accurate error compensation can improve the performance of RLG further. Some proposals, which are helpful to future research on the field, are concluded.
As mechanical dither is widely applied to reduce frequency "Lock-in" of RLG (ring laser gyroscope) that is based on the principle proposed by Sagnac in 1913, it is necessary to know the recent development in the field. The proper design of dither mechanism that decides the effect of bias to some extent is discussed. The proper dither signal and its control have a direct influence on dither efficiency. Real, stable and accurate error compensation can improve the performance of RLG further. Some proposals, which are helpful to future research on the field, are concluded.
2001, 15(2).
Abstract:
Compared with the traditional rigid-plastic/rigid-viscoplastic(RP/RVP) FEM(based on iteration solution), RP/RVP FEM based on linear programming(LP) has some remarkable advantages, such as it 's free of convergence problem and its convenience in contact, rigid zone, and friction force treatment. The numerical model of RP/RVP FEM based on LP for axisymmetrical metal forming simulation is studied, and some related key factors and its treatment methods in formulation of constraint condition are proposed. Some solution examples are provided to validate its accuracy and efficiency.
Compared with the traditional rigid-plastic/rigid-viscoplastic(RP/RVP) FEM(based on iteration solution), RP/RVP FEM based on linear programming(LP) has some remarkable advantages, such as it 's free of convergence problem and its convenience in contact, rigid zone, and friction force treatment. The numerical model of RP/RVP FEM based on LP for axisymmetrical metal forming simulation is studied, and some related key factors and its treatment methods in formulation of constraint condition are proposed. Some solution examples are provided to validate its accuracy and efficiency.
2001, 15(2).
Abstract:
A complex number node analysis approach is proposed for vibration reducing of structural flexible redundant manipulators by utilizing self-motion. In the proposed approach, the self-motion is evaluated to nullify the modal excitingforce of flexural motion, and the approach can be freely used when the degree of freedom of flexural motion is much greater than the available degree of reundancy. The availability and effectiveness of the proposed appproach are demonstrated through numerical simulation with a four-link spatial robotic manipullator possessing an end flexible link.
A complex number node analysis approach is proposed for vibration reducing of structural flexible redundant manipulators by utilizing self-motion. In the proposed approach, the self-motion is evaluated to nullify the modal excitingforce of flexural motion, and the approach can be freely used when the degree of freedom of flexural motion is much greater than the available degree of reundancy. The availability and effectiveness of the proposed appproach are demonstrated through numerical simulation with a four-link spatial robotic manipullator possessing an end flexible link.
2001, 15(2).
Abstract:
The effects of the location, numer and stiffness of guide pads on the lowest critical rotational frequencies of the rotating circular saw damped at the inside and free at the perimeter are discussed by the mon-linear theory and the perturbation theory of structural vibration analysis. The influence of the centrifugal force and the cutting temperature are considered in the course of the analysis. The results of the analysis and the calculation show that the introduction of one guide does not stably raise critical rotational frequencies of the circular saw. The two guides can raise lowest critical rotational frequency of the circular saw then the angle between the two guides fixed on the direction of the circumference satisfies the certain conditions.
The effects of the location, numer and stiffness of guide pads on the lowest critical rotational frequencies of the rotating circular saw damped at the inside and free at the perimeter are discussed by the mon-linear theory and the perturbation theory of structural vibration analysis. The influence of the centrifugal force and the cutting temperature are considered in the course of the analysis. The results of the analysis and the calculation show that the introduction of one guide does not stably raise critical rotational frequencies of the circular saw. The two guides can raise lowest critical rotational frequency of the circular saw then the angle between the two guides fixed on the direction of the circumference satisfies the certain conditions.
2001, 15(2).
Abstract:
Rhombus thinking, a new creative thinking method, is the combination of divergent thinking process and convergent thinking process, in which qualitative analysis is carried out before quantitative analysis. This method tries to solve the bottle neck problem in intelligent CAD based on the extension theory. The rhombus thinking method to the scheme design of new products is applied. In this products is applied. In this process, firstly, the matter-element expression for the know information are set up, and then a set of matter-elements are opened up by matter-elements extension method; Finally, the useful information are got by appraisal method of dependent degree. It has been successfully applied to the scheme design for the cutter-store of machining center. Theoretical and experimental results demonstrated that the method is much more accurate, objective and efficient than the traditional one.
Rhombus thinking, a new creative thinking method, is the combination of divergent thinking process and convergent thinking process, in which qualitative analysis is carried out before quantitative analysis. This method tries to solve the bottle neck problem in intelligent CAD based on the extension theory. The rhombus thinking method to the scheme design of new products is applied. In this products is applied. In this process, firstly, the matter-element expression for the know information are set up, and then a set of matter-elements are opened up by matter-elements extension method; Finally, the useful information are got by appraisal method of dependent degree. It has been successfully applied to the scheme design for the cutter-store of machining center. Theoretical and experimental results demonstrated that the method is much more accurate, objective and efficient than the traditional one.
2001, 15(2).
Abstract:
Logic components are used to support the conceptual design. Taking the stamping die structure as the research object, several logic components are defined for the conceptual die construction design. A new method-logic assembly modeling is presented to satisfy the characteristic of the top-down die design process. Representing shapes and spatial relations in logic can provide a natural, intuitive method of developing complete computer systems for reasoning about die construction design at the conceptual stage. This method can reflect the designer's thought clearly and provide the designer with a test bed for generating alternatives and performing reasoning work at the conceptual die design stage.
Logic components are used to support the conceptual design. Taking the stamping die structure as the research object, several logic components are defined for the conceptual die construction design. A new method-logic assembly modeling is presented to satisfy the characteristic of the top-down die design process. Representing shapes and spatial relations in logic can provide a natural, intuitive method of developing complete computer systems for reasoning about die construction design at the conceptual stage. This method can reflect the designer's thought clearly and provide the designer with a test bed for generating alternatives and performing reasoning work at the conceptual die design stage.
2001, 15(2).
Abstract:
The Newton-Raphson iteration and QR algorithm are combined to search the Hopf bifurcation point of the vehicle running on straight track and on large radius curved tracks. Limit cycles that are bifurcated from the equilibrium points and the saddle-node bifurcation point are computed through employing a variable-step Runge-Kutta method and the Poincare map. Finally, numerical simulations are carried out for the stability of a high speed passenger car operating on straight and large radius curved tracks. The influences of the radius of curvature and the superelevation of the track on the stability of the vehicle system are investigated.
The Newton-Raphson iteration and QR algorithm are combined to search the Hopf bifurcation point of the vehicle running on straight track and on large radius curved tracks. Limit cycles that are bifurcated from the equilibrium points and the saddle-node bifurcation point are computed through employing a variable-step Runge-Kutta method and the Poincare map. Finally, numerical simulations are carried out for the stability of a high speed passenger car operating on straight and large radius curved tracks. The influences of the radius of curvature and the superelevation of the track on the stability of the vehicle system are investigated.
2001, 15(2).
Abstract:
Acclimatizing itself to the development of network, Math Works Inc constructed a MATLAB Web Server environment by dint of which one can browse the calculation and plots of MATLAB through Internet directly. The installation and use of the environment is introduced. A code established on the platform of MATLAB, which deals with the modal analysis of magnetic bearing system(MBS) supporting rotors of five degrees of freedom and considering the coupling of thrust bearing with radical bearings is modified to work in the environment. The purpose is to realize a remote call of the code by users through Internet for the performance analysis of the system. Such an application is very important to the concurrent design of MBS and for the utilization of distributive knowledge acquistion resources in collaborative design. The work on modification and realization is described and the results are discussed.
Acclimatizing itself to the development of network, Math Works Inc constructed a MATLAB Web Server environment by dint of which one can browse the calculation and plots of MATLAB through Internet directly. The installation and use of the environment is introduced. A code established on the platform of MATLAB, which deals with the modal analysis of magnetic bearing system(MBS) supporting rotors of five degrees of freedom and considering the coupling of thrust bearing with radical bearings is modified to work in the environment. The purpose is to realize a remote call of the code by users through Internet for the performance analysis of the system. Such an application is very important to the concurrent design of MBS and for the utilization of distributive knowledge acquistion resources in collaborative design. The work on modification and realization is described and the results are discussed.
2001, 15(2).
Abstract:
A new typed hydraulic system of electro-hydraulic hammer is researched and developed. By means of power bond graphs the modeling and simulation to the dynamic characteristics of the new hydraulic system are performed. The experimental research which is emphasized on the blowing stroke is also performed. It is proved from the result of simulation and experiment that this new hydraulic system possesses such advantages as simplification of structure, flexibeness of operation and reliability of working. Especially it possesses better dynamic characteristics.
A new typed hydraulic system of electro-hydraulic hammer is researched and developed. By means of power bond graphs the modeling and simulation to the dynamic characteristics of the new hydraulic system are performed. The experimental research which is emphasized on the blowing stroke is also performed. It is proved from the result of simulation and experiment that this new hydraulic system possesses such advantages as simplification of structure, flexibeness of operation and reliability of working. Especially it possesses better dynamic characteristics.
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