1992 Vol.5(1)
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1992, 6(1).
Abstract:
In this paper, a new idea of linearizing the dynamic model of flexible robots is put forward. Based on linearization of the kinematic mode, the decoupled time-variant linear differential equations, with micro-variables as generalized coordinates, are deduced from the general dynamic equations. The numerical computation of a 3-link arm for the normal dynamic problem is also carried out.
In this paper, a new idea of linearizing the dynamic model of flexible robots is put forward. Based on linearization of the kinematic mode, the decoupled time-variant linear differential equations, with micro-variables as generalized coordinates, are deduced from the general dynamic equations. The numerical computation of a 3-link arm for the normal dynamic problem is also carried out.
1992, 6(1).
Abstract:
This paper describes the study on the metering shock and vibration characteristic and its transmission from cylinder to swash plate within a 25SCY14-1B axial piston pump. The exciting force and torque acting on swash plate were derived and finite element method was used to analyze the vibration model of the swash plate in the pump. The cylinder pressure transients and swash plate vibration were measured by miniature pressure sensor and acceleration meters. The analyzed result was verified by experiments. And on these bases, some principles for reducing piston pump's metering vibration and noise were given.
This paper describes the study on the metering shock and vibration characteristic and its transmission from cylinder to swash plate within a 25SCY14-1B axial piston pump. The exciting force and torque acting on swash plate were derived and finite element method was used to analyze the vibration model of the swash plate in the pump. The cylinder pressure transients and swash plate vibration were measured by miniature pressure sensor and acceleration meters. The analyzed result was verified by experiments. And on these bases, some principles for reducing piston pump's metering vibration and noise were given.
1992, 6(1).
Abstract:
Elastic-plastic large displacement bending of sheets involves both material and geometric nonlinear analysis. In thesis, the finite element analysis models are obtained by means of transformation of coordinate systems and small defection theory of sheets. Analysis of straignt seam welded tube forming process and double layer welded tube (DLWT) forming process is carried out with this model, and the comparison between theoretical and experimental results has been made. The results demonstrate that this method is effective and convenient to analyze elastic-plastic large displacement bending of sheets.
Elastic-plastic large displacement bending of sheets involves both material and geometric nonlinear analysis. In thesis, the finite element analysis models are obtained by means of transformation of coordinate systems and small defection theory of sheets. Analysis of straignt seam welded tube forming process and double layer welded tube (DLWT) forming process is carried out with this model, and the comparison between theoretical and experimental results has been made. The results demonstrate that this method is effective and convenient to analyze elastic-plastic large displacement bending of sheets.
1992, 6(1).
Abstract:
Considering that the practical sliding friction is a repeated friction process of the same asperity on the same track, this paper, based on the contact model of "ball-on-disc", established some mathematic expressions for calculating the depth of wear track and frictional coefficient of a hard asperity on soft plating layer contact after an arbitrary times of friction. The results of calculation were in good agreement with experimental values. In discussions the important influence of plastic flow stress (Pm) of soft plating layers on the computation results had been emphasized.
Considering that the practical sliding friction is a repeated friction process of the same asperity on the same track, this paper, based on the contact model of "ball-on-disc", established some mathematic expressions for calculating the depth of wear track and frictional coefficient of a hard asperity on soft plating layer contact after an arbitrary times of friction. The results of calculation were in good agreement with experimental values. In discussions the important influence of plastic flow stress (Pm) of soft plating layers on the computation results had been emphasized.
1992, 6(1).
Abstract:
The omen identification of machining chatter and corresponding control strategy are discussed emphatically in this paper. It is confirmed that there are essential connections between the cutting stability and identification parameter θ of chattering omen. When the cutting process is transiting from stable state to an unstable state, we may predict the chattering according to the variation of identification parameter θ. When the value of θ exceeds its giving control threshold θlim, a control signal will be sent to the vari-speed control system immediately from the chatter prediction system. A special strategy of learning vari-speed is proposed to control the machining chatter, it has good effect on suppressing chatter.
The omen identification of machining chatter and corresponding control strategy are discussed emphatically in this paper. It is confirmed that there are essential connections between the cutting stability and identification parameter θ of chattering omen. When the cutting process is transiting from stable state to an unstable state, we may predict the chattering according to the variation of identification parameter θ. When the value of θ exceeds its giving control threshold θlim, a control signal will be sent to the vari-speed control system immediately from the chatter prediction system. A special strategy of learning vari-speed is proposed to control the machining chatter, it has good effect on suppressing chatter.
1992, 6(1).
Abstract:
In this paper, based on the fundamental theory of plastic mechanics of continuum, the analytic formulae to express the stress field, strain field and strain rate field for the bulging procedures under the common action of two opposite pressures mentioned above are derived, the effect of the pressures on stress state and bulging velocity are discussed in comparison with the case of one single pressure acted bulging.
In this paper, based on the fundamental theory of plastic mechanics of continuum, the analytic formulae to express the stress field, strain field and strain rate field for the bulging procedures under the common action of two opposite pressures mentioned above are derived, the effect of the pressures on stress state and bulging velocity are discussed in comparison with the case of one single pressure acted bulging.
1992, 6(1).
Abstract:
In this paper, the composed principle about kinematic chain with multiple joints (in short, M.J.) is firstly discussed, and a factor of M.J.about kinematic chain (in short, K.C.) is defined, so that the structural analysis and synthesis of the K.C.with M.j.are simplified, and then the 6-bar and 8-bar Assur groups with M.J.are investigated. All the independent types of the Assur groups with M.J.are obtained.
In this paper, the composed principle about kinematic chain with multiple joints (in short, M.J.) is firstly discussed, and a factor of M.J.about kinematic chain (in short, K.C.) is defined, so that the structural analysis and synthesis of the K.C.with M.j.are simplified, and then the 6-bar and 8-bar Assur groups with M.J.are investigated. All the independent types of the Assur groups with M.J.are obtained.
1992, 6(1).
Abstract:
A new procedure of finite segment modelling is presented in this paper. The flexibility is introduced into the dynamic equations of Huston's method with the simplest expressions of stiffness equations. All of the inertial and elastic couplings are taken into account, and the effects of shear displacements and warping are also considered. Hence, the procedure can be used for dynamic analyses of multibody systems with general cross-sectioned beam-like members undergoing complex three-dimensional motions such as flexible robots. The realtions between finite segment method and finite element method are discovered, with which and examples the rationality of the modelling procedure is confirmed.
A new procedure of finite segment modelling is presented in this paper. The flexibility is introduced into the dynamic equations of Huston's method with the simplest expressions of stiffness equations. All of the inertial and elastic couplings are taken into account, and the effects of shear displacements and warping are also considered. Hence, the procedure can be used for dynamic analyses of multibody systems with general cross-sectioned beam-like members undergoing complex three-dimensional motions such as flexible robots. The realtions between finite segment method and finite element method are discovered, with which and examples the rationality of the modelling procedure is confirmed.
1992, 6(1).
Abstract:
The mechanism of forced regenerative chatter in machine tools is studied in this paper. It is pointed out that this kind of chatter is a resonance of the chatter regenerative instable mode caused by a forced excitation. A method for judging the chatter is developed, which is based on the 3-dimensional spectrum of chatter control are developed: one is called the strategy of shifting the main mode of chatter aimed to increase the stiffness or damping of a machine tool to make the higher-order mode of the system into the main mode of chatter so that the forced regenerative chatter is restrained, and the other is called the strategy of removing forced excitation aimed to remove forced excitation directly or to change the speed of spindle to avoid the frequency of forced excitation so that the chatter is eliminated. The research results in this paper have been applied to a type Mx-4 crank lathe.
The mechanism of forced regenerative chatter in machine tools is studied in this paper. It is pointed out that this kind of chatter is a resonance of the chatter regenerative instable mode caused by a forced excitation. A method for judging the chatter is developed, which is based on the 3-dimensional spectrum of chatter control are developed: one is called the strategy of shifting the main mode of chatter aimed to increase the stiffness or damping of a machine tool to make the higher-order mode of the system into the main mode of chatter so that the forced regenerative chatter is restrained, and the other is called the strategy of removing forced excitation aimed to remove forced excitation directly or to change the speed of spindle to avoid the frequency of forced excitation so that the chatter is eliminated. The research results in this paper have been applied to a type Mx-4 crank lathe.
1992, 6(1).
Abstract:
The mathematical model of the hydraulic-pneumatic bammer was constructed with power bond graph and state space analysis methods for the first time in this paper. The dynamic characteristics of blowing and heightening can be studied by the mathematical model. After computer simulation programmed, the regularity that dynamic hydraulic pressure and displacements, velocities and accelerations of the ram are changing with time were obtained. With simulating results being in accordance with testing ones. It is proved that this method is appliable, and this model can be used to analyze and design the hydraulic pneumatic hammer.
The mathematical model of the hydraulic-pneumatic bammer was constructed with power bond graph and state space analysis methods for the first time in this paper. The dynamic characteristics of blowing and heightening can be studied by the mathematical model. After computer simulation programmed, the regularity that dynamic hydraulic pressure and displacements, velocities and accelerations of the ram are changing with time were obtained. With simulating results being in accordance with testing ones. It is proved that this method is appliable, and this model can be used to analyze and design the hydraulic pneumatic hammer.
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