2004 Vol.17(1)
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2004, 18(1).
Abstract:
The calculation method for vane numbers is obtained on the intention that it should have no back flow area in the flow passage of centrifugal passage. Then a criterion that the design of splitting vanes of centrifugal compound impeller should ensure that the back flow area ratio be the minimum is proposed. On the basis of the criterion, the slippery theory is used as one of CFD methods to analyze the inner flow field of the impeller of various kinds of splitting vanes design, therefore, the optimized design of splitting vanes is obtained and which agrees with that of some testing results.
The calculation method for vane numbers is obtained on the intention that it should have no back flow area in the flow passage of centrifugal passage. Then a criterion that the design of splitting vanes of centrifugal compound impeller should ensure that the back flow area ratio be the minimum is proposed. On the basis of the criterion, the slippery theory is used as one of CFD methods to analyze the inner flow field of the impeller of various kinds of splitting vanes design, therefore, the optimized design of splitting vanes is obtained and which agrees with that of some testing results.
2004, 18(1).
Abstract:
Flight simulator is an important device and a typical high performance position servo system used in the hardware-in-the-loop simulation of flight control system. Without using the future desired output, zero phase error controller makes the overall system's frequency response exhibit zero phase shift for all frequencies and a very small gain error at low frequency range can be achieved. A new algorithm to design the feedforward controller is presented, in order to reduce the phase error, the design of proposed feedforward con-troller uses a modified plant model, which is a closed loop transfer function, through which the system tracking precision performance can be improved greatly. Real-time control results show the effectiveness of the proposed approach in flight simulator servo system.
Flight simulator is an important device and a typical high performance position servo system used in the hardware-in-the-loop simulation of flight control system. Without using the future desired output, zero phase error controller makes the overall system's frequency response exhibit zero phase shift for all frequencies and a very small gain error at low frequency range can be achieved. A new algorithm to design the feedforward controller is presented, in order to reduce the phase error, the design of proposed feedforward con-troller uses a modified plant model, which is a closed loop transfer function, through which the system tracking precision performance can be improved greatly. Real-time control results show the effectiveness of the proposed approach in flight simulator servo system.
2004, 18(1).
Abstract:
A new tool force model to be presented is based upon process geometry and the characteristics of the force system，in which the forces acting on the tool rake face，the cutting edge rounding and the clearance face have been considered，and the size effect is accountable for the new model. It is desired that the model can be well applicable to conventional diamond turning and the model may be employed as a tool in the design of diamond tools. This approach is quite different from traditional investigations primarily based on empirical studies. As the depth of cut becomes the same order as the rounded cutting edge radius，sliding along the clearance face due to elastic recovery of workpiece material and plowing due to the rounded cutting edge may become important in micro-machining，the forces acting on the cutting edge rounding and the clearance face can not be neglected. For this reason，it is very important to understand the influence of some parameters on tool forces and develop a model of the relationship between them.
A new tool force model to be presented is based upon process geometry and the characteristics of the force system，in which the forces acting on the tool rake face，the cutting edge rounding and the clearance face have been considered，and the size effect is accountable for the new model. It is desired that the model can be well applicable to conventional diamond turning and the model may be employed as a tool in the design of diamond tools. This approach is quite different from traditional investigations primarily based on empirical studies. As the depth of cut becomes the same order as the rounded cutting edge radius，sliding along the clearance face due to elastic recovery of workpiece material and plowing due to the rounded cutting edge may become important in micro-machining，the forces acting on the cutting edge rounding and the clearance face can not be neglected. For this reason，it is very important to understand the influence of some parameters on tool forces and develop a model of the relationship between them.
2004, 18(1).
Abstract:
The piezoelectric pump with nozzle/diffuser-elements, which oscillating form differing from regular volumetric reciprocating or rotating pumps because there are nozzle/diffuser-elements substituted for regular valves, is a new type pump whose actuator is a piezoelectric ceramal part with verse piezoelectric effect. In recent year, piezoelectric pump is paid increasing attention to because it is an ideal candidate in application in such area as medical health, mechanical tools and micro-mechanism. The fundamental research on it, however, is still not made through. Focuses on the phenomenon of different directions of flow among Germany pump, Chinese pump and Swiss pump, which are all fitted with nozzle/diffuser-elements, and analyzes the cone angle of nozzle/diffuser-elements based on the flow equation of valve-less piezoelectric pump with nozzle/diffuser-elements. As a result, the concepts of diffuser loss coefficient and loss coefficient are introduced to explain these phenomena, from which a discussion is given on the optimization of the cone angle of nozzle/diffuser-element aiming at the maximum of pump flow.
The piezoelectric pump with nozzle/diffuser-elements, which oscillating form differing from regular volumetric reciprocating or rotating pumps because there are nozzle/diffuser-elements substituted for regular valves, is a new type pump whose actuator is a piezoelectric ceramal part with verse piezoelectric effect. In recent year, piezoelectric pump is paid increasing attention to because it is an ideal candidate in application in such area as medical health, mechanical tools and micro-mechanism. The fundamental research on it, however, is still not made through. Focuses on the phenomenon of different directions of flow among Germany pump, Chinese pump and Swiss pump, which are all fitted with nozzle/diffuser-elements, and analyzes the cone angle of nozzle/diffuser-elements based on the flow equation of valve-less piezoelectric pump with nozzle/diffuser-elements. As a result, the concepts of diffuser loss coefficient and loss coefficient are introduced to explain these phenomena, from which a discussion is given on the optimization of the cone angle of nozzle/diffuser-element aiming at the maximum of pump flow.
2004, 18(1).
Abstract:
Sealing performance of the reciprocat-ing seals on a larger diameter (100 mm in diameter ) axial piston is theoretically investigated. Based on the characteris-tics of the clearance flow between the seal and the piston, reasonable boundary conditions for Navier-Stokes equations are determined and the equations are modified, so that the final equations can describe the real flow state of the clear-ance flow. Through combining the final equations with finite element method, the pressure distributions within the clearance field during the reciprocating motion of the piston and the leakage rate with the pressure are studied. The deflections of the seal which affect sealing performance are calculated as well. Sealing performance of piston seals using oil as the working liquid is compared with using water. It is concluded that the seal using water as the working liquid is under dry friction, which cannot be dealt with the theory of fluid mechanics. The seal structure is only acceptable using oil as the working liquid.
Sealing performance of the reciprocat-ing seals on a larger diameter (100 mm in diameter ) axial piston is theoretically investigated. Based on the characteris-tics of the clearance flow between the seal and the piston, reasonable boundary conditions for Navier-Stokes equations are determined and the equations are modified, so that the final equations can describe the real flow state of the clear-ance flow. Through combining the final equations with finite element method, the pressure distributions within the clearance field during the reciprocating motion of the piston and the leakage rate with the pressure are studied. The deflections of the seal which affect sealing performance are calculated as well. Sealing performance of piston seals using oil as the working liquid is compared with using water. It is concluded that the seal using water as the working liquid is under dry friction, which cannot be dealt with the theory of fluid mechanics. The seal structure is only acceptable using oil as the working liquid.
2004, 18(1).
Abstract:
The 3-D turbulent flow in the impeller of sewage pump is simulated. The time-averaged N-S equations and the k-ε turbulent model is modified. The calculation is carried out in body-fitted coordinated grid by applying SIMPLE-C algorithm. The calculated velocity, pressure distributions of the turbulent flow in the sewage pump are obtained for the first time, which will be helpful for the optimal design and performance prediction of sewage pumps on the basis of flow field simulation.
The 3-D turbulent flow in the impeller of sewage pump is simulated. The time-averaged N-S equations and the k-ε turbulent model is modified. The calculation is carried out in body-fitted coordinated grid by applying SIMPLE-C algorithm. The calculated velocity, pressure distributions of the turbulent flow in the sewage pump are obtained for the first time, which will be helpful for the optimal design and performance prediction of sewage pumps on the basis of flow field simulation.
2004, 18(1).
Abstract:
An effective computational method is developed for dynamic analysis of fluid-structure interaction problems involving large-amplitude sloshing of the fluid and large-displacement motion of the structure. The structure is modeled as a rigid container sup-ported by a system consisting of springs and dashpots. The motion of the fluid is decomposed into two parts: the large-displacement motion with the container and the large-amplitude sloshing relative to the container. The former is conveniently dealt with by defining a container-fixed noninertial local frame, while the latter is easily handled by adopting an ALE kinematical description. This leads to an easy and accurate treatment of both the fluid-structure interface and the fluid free surface without producing excessive distortion of the computational mesh. The coupling between the fluid and the structure is accomplished through the coupling matrices that can be easily established. Two numerical examples, including a TLD-structure system and a simplified liquid-loaded vehicle system, are presented to demonstrate the effectiveness and reliability of the proposed method. The present work can also be applied to simulate fluid-structure problems incorporating multibody systems and several fluid domains.
An effective computational method is developed for dynamic analysis of fluid-structure interaction problems involving large-amplitude sloshing of the fluid and large-displacement motion of the structure. The structure is modeled as a rigid container sup-ported by a system consisting of springs and dashpots. The motion of the fluid is decomposed into two parts: the large-displacement motion with the container and the large-amplitude sloshing relative to the container. The former is conveniently dealt with by defining a container-fixed noninertial local frame, while the latter is easily handled by adopting an ALE kinematical description. This leads to an easy and accurate treatment of both the fluid-structure interface and the fluid free surface without producing excessive distortion of the computational mesh. The coupling between the fluid and the structure is accomplished through the coupling matrices that can be easily established. Two numerical examples, including a TLD-structure system and a simplified liquid-loaded vehicle system, are presented to demonstrate the effectiveness and reliability of the proposed method. The present work can also be applied to simulate fluid-structure problems incorporating multibody systems and several fluid domains.
2004, 18(1).
Abstract:
The structure, function and working principle of JLUIV-3, which is a new type of automated guided vehicle (AGV) with computer vision, is described. The white stripe line with certain width is used as inductive mark for JLUIV-3 automated navigation. JULIV-3 can automatically recognize the Arabic numeral codes which mark the multi-branch paths and multi-operation buffers, and autonomously select the correct path for destination. Compared with the traditional AGV, it has much more navigation flexibility and less cost, and provides higher-level intelligence. The identification method of navigation path by using neural network and the optimal control method of the AGV are introduced in detail.
The structure, function and working principle of JLUIV-3, which is a new type of automated guided vehicle (AGV) with computer vision, is described. The white stripe line with certain width is used as inductive mark for JLUIV-3 automated navigation. JULIV-3 can automatically recognize the Arabic numeral codes which mark the multi-branch paths and multi-operation buffers, and autonomously select the correct path for destination. Compared with the traditional AGV, it has much more navigation flexibility and less cost, and provides higher-level intelligence. The identification method of navigation path by using neural network and the optimal control method of the AGV are introduced in detail.
2004, 18(1).
Abstract:
Parallel manipulators have many advantages over serial manipulators in terms of high load/weight ratio, velocity, stiffness and precision. A dimensional design theory and methodology of six degrees of freedom scissor parallel manipulator (SPM) is investigated. The SPM kinematics inverse equation is given. Based on the formulation of the local dexterity and the definition about the indexes of workspace incircle radius, the effects of the design parameters on the dexterity and workspace are discussed. Moreover the incircle radius change ratio about workspace are defined and used as the evaluated indicator to analyze the effects of the design parameters on the performances. A dimensional design theory that could satisfy the requirement of dexterity and workspace is proposed. The dimensional design theory and methodology can be of help in the design, trajectory planning and control of parallel manipulator.
Parallel manipulators have many advantages over serial manipulators in terms of high load/weight ratio, velocity, stiffness and precision. A dimensional design theory and methodology of six degrees of freedom scissor parallel manipulator (SPM) is investigated. The SPM kinematics inverse equation is given. Based on the formulation of the local dexterity and the definition about the indexes of workspace incircle radius, the effects of the design parameters on the dexterity and workspace are discussed. Moreover the incircle radius change ratio about workspace are defined and used as the evaluated indicator to analyze the effects of the design parameters on the performances. A dimensional design theory that could satisfy the requirement of dexterity and workspace is proposed. The dimensional design theory and methodology can be of help in the design, trajectory planning and control of parallel manipulator.
2004, 18(1).
Abstract:
Traditional PID controllers are no longer suitable for magnetic-bearing-supported high-speed flywheels with significant gyroscopic effects. Because gyroscopic effects greatly influence the stability of the flywheel rotor，especially at high rotational speeds. Velocity cross feedback and displacement cross feedback are used to overcome harmful effects of nutation and precession modes, and stabilize the rotor at high rotational speeds. Theoretical analysis is given to show their effects. A control platform based on RTLinux and a PC is built to control the active magnetic bearing (AMB) system, and relevant results are reported. Using velocity cross feedback and displacement cross feedback in a closed loop control system, the flywheel successfully runs at over 20 000 r/min.
Traditional PID controllers are no longer suitable for magnetic-bearing-supported high-speed flywheels with significant gyroscopic effects. Because gyroscopic effects greatly influence the stability of the flywheel rotor，especially at high rotational speeds. Velocity cross feedback and displacement cross feedback are used to overcome harmful effects of nutation and precession modes, and stabilize the rotor at high rotational speeds. Theoretical analysis is given to show their effects. A control platform based on RTLinux and a PC is built to control the active magnetic bearing (AMB) system, and relevant results are reported. Using velocity cross feedback and displacement cross feedback in a closed loop control system, the flywheel successfully runs at over 20 000 r/min.
2004, 18(1).
Abstract:
The influences of thrust magnetic bearing and journal tilt on dynamic characteristics of rotor system are studied mainly. The outcome shows that the influences of coupling effects of thrust magnetic bearing and tilt of journal on critical rotational speeds of system are very large, and the stability of system reduces greatly. That shows it is important that the influence of coupling effects of thrust and radial magnetic bearings due to the rotor tilting must be considered in the study of rotor-magnetic bearings system dynamic characteristics, and also shows it is important that the rotor is mounted and debugged in ideal alignment of magnetic bearings.
The influences of thrust magnetic bearing and journal tilt on dynamic characteristics of rotor system are studied mainly. The outcome shows that the influences of coupling effects of thrust magnetic bearing and tilt of journal on critical rotational speeds of system are very large, and the stability of system reduces greatly. That shows it is important that the influence of coupling effects of thrust and radial magnetic bearings due to the rotor tilting must be considered in the study of rotor-magnetic bearings system dynamic characteristics, and also shows it is important that the rotor is mounted and debugged in ideal alignment of magnetic bearings.
2004, 18(1).
Abstract:
According to the deficiency of the present model of pneumatic artificial muscles (PAM), a serial model is built up based on the PAM's essential working principle with the elastic theory, it is validated by the quasi-static and dynamic experiment results, which are gained from two experiment systems. The experiment results and the simulation results illustrate that the serial model has made a great success compared with Chou's model, which can describe the force characteristics of PAM more precisely. A compensation item considering the braid's elasticity and the coulomb damp is attached to the serial model based on the analysis of the experiment results. The dynamic experiment proves that the viscous damp of the PAM could be ignored in order to simplify the model of PAM. Finally, an improved serial model of PAM is obtained.
According to the deficiency of the present model of pneumatic artificial muscles (PAM), a serial model is built up based on the PAM's essential working principle with the elastic theory, it is validated by the quasi-static and dynamic experiment results, which are gained from two experiment systems. The experiment results and the simulation results illustrate that the serial model has made a great success compared with Chou's model, which can describe the force characteristics of PAM more precisely. A compensation item considering the braid's elasticity and the coulomb damp is attached to the serial model based on the analysis of the experiment results. The dynamic experiment proves that the viscous damp of the PAM could be ignored in order to simplify the model of PAM. Finally, an improved serial model of PAM is obtained.
2004, 18(1).
Abstract:
Measure index system of technical innovation in medium and small manufacturing enterprises is established according to principles of exploration, adaptability, standardization, generalization, feasibility, comparability and combination of economic benefit and continual development. It includes index of technical innovation capacity, informational administration on technical innovation, and investment of technical innovation, economic benefit, green technical level, social contribution and other influential indexes. Approach to measure of technical innovation in medium and small manufacturing enterprises is presented based on combination of grey relation and fuzzy hierarchy analysis, and conclusions are drawn based on practical analysis of 20 medium and small enterprises, which provides the basis for the medium and small enterprises to select technical innovation policies and the government to constitute relative policies.
Measure index system of technical innovation in medium and small manufacturing enterprises is established according to principles of exploration, adaptability, standardization, generalization, feasibility, comparability and combination of economic benefit and continual development. It includes index of technical innovation capacity, informational administration on technical innovation, and investment of technical innovation, economic benefit, green technical level, social contribution and other influential indexes. Approach to measure of technical innovation in medium and small manufacturing enterprises is presented based on combination of grey relation and fuzzy hierarchy analysis, and conclusions are drawn based on practical analysis of 20 medium and small enterprises, which provides the basis for the medium and small enterprises to select technical innovation policies and the government to constitute relative policies.
2004, 18(1).
Abstract:
Based on extenics, an extensive functional information model (function-behavioral action-structure–environmental constraint) of the mechanical product intelligent conceptual design is developed, and the mechanism of theoretic structure solutions is produced, the mapping relations between function–behavior and behavior–structure are analyzed. The model is applied to the filling material system's conceptual design to verify validity.
Based on extenics, an extensive functional information model (function-behavioral action-structure–environmental constraint) of the mechanical product intelligent conceptual design is developed, and the mechanism of theoretic structure solutions is produced, the mapping relations between function–behavior and behavior–structure are analyzed. The model is applied to the filling material system's conceptual design to verify validity.
2004, 18(1).
Abstract:
A genetic algorithm(GA)-based new method is designed to evaluate the circularity error of mechanical parts. The method uses the capability of nonlinear optimization of GA to search for the optimal solution of circularity error. The finely-designed GA (FDGA) characterized dynamical bisexual recombination and Gaussian mutation. The mathematical model of the nonlinear problem is given. The implementation details in FDGA are described such as the crossover or recombination mechanism which utilized a bisexual reproduction scheme and the elitist reservation method; and the adaptive mutation which used the Gaussian probability distribution to determine the values of the offspring produced by mutation mechanism. The examples are provided to verify the designed FDGA. The computation results indicate that the FDGA works very well in the field of form error evaluation such as circularity evaluation.
A genetic algorithm(GA)-based new method is designed to evaluate the circularity error of mechanical parts. The method uses the capability of nonlinear optimization of GA to search for the optimal solution of circularity error. The finely-designed GA (FDGA) characterized dynamical bisexual recombination and Gaussian mutation. The mathematical model of the nonlinear problem is given. The implementation details in FDGA are described such as the crossover or recombination mechanism which utilized a bisexual reproduction scheme and the elitist reservation method; and the adaptive mutation which used the Gaussian probability distribution to determine the values of the offspring produced by mutation mechanism. The examples are provided to verify the designed FDGA. The computation results indicate that the FDGA works very well in the field of form error evaluation such as circularity evaluation.
2004, 18(1).
Abstract:
The FB-ZVZCS-PWM converter is realized by the way of subjoining block-capacitor into the FB-ZVS-PWM converter. At the freewheeling interval, the primary current is attenuated fast to zero and maintained. And then, power device of the static leg becomes a zero-current-switch (ZCS), power device of the shifted leg becomes a zero-voltage-switch(ZVS). Thus, on one hand IGBT (Insulated gate bipolar transistor) with tail current can be easily used in full-bridge soft-switching converter; on the other hand additional circuiting energy is greatly reduced. At the same time, less duty cycle loss, lower secondary parasitic resonance, wider soft-switching load range can be achieved. Based on the existing component models in the Pspice software package, a combined model of IGBT is established, in which a non-linear capacitor is introduced to replace the parasitic capacitor. Using this model, computerized simulation is conducted for the FB-ZVZCS-PWM soft-switching converter, the switching and energy-transferring characteristics of the power device are analyzed. Finally, based on the achievement above, a 10 kW arc welding inverter with FB-ZVZCS-PWM converter is developed. The simulation results are testified by experiments. It is proved that by adopting appropriate models, computerized simulation is an effective and useful tool for the development of the arc welding inverter.
The FB-ZVZCS-PWM converter is realized by the way of subjoining block-capacitor into the FB-ZVS-PWM converter. At the freewheeling interval, the primary current is attenuated fast to zero and maintained. And then, power device of the static leg becomes a zero-current-switch (ZCS), power device of the shifted leg becomes a zero-voltage-switch(ZVS). Thus, on one hand IGBT (Insulated gate bipolar transistor) with tail current can be easily used in full-bridge soft-switching converter; on the other hand additional circuiting energy is greatly reduced. At the same time, less duty cycle loss, lower secondary parasitic resonance, wider soft-switching load range can be achieved. Based on the existing component models in the Pspice software package, a combined model of IGBT is established, in which a non-linear capacitor is introduced to replace the parasitic capacitor. Using this model, computerized simulation is conducted for the FB-ZVZCS-PWM soft-switching converter, the switching and energy-transferring characteristics of the power device are analyzed. Finally, based on the achievement above, a 10 kW arc welding inverter with FB-ZVZCS-PWM converter is developed. The simulation results are testified by experiments. It is proved that by adopting appropriate models, computerized simulation is an effective and useful tool for the development of the arc welding inverter.
2004, 18(1).
Abstract:
To control the position of differential cylinder closed loop without using any throttle elements, a new idea that two speed variable pumps are used to compensate the non-symmetric flow of differential cylinder is carried out. According to the leaking property of the system, a speed offset principle is also proposed to eliminate the cavitation and tension caused by the leakage and condensation of oil, which makes the system be in the same state as a valve controlled circuit. This principle is explained theoretically and experimentally. Further the relationship that the pressures in cylinder chambers change with load and leakage, and the relationship between biasing speed and pre-load pressures in cylinder chambers are established. The research has proved that the new system has similar technique features as those of controlled with servo valves, but due to the elimination of all the throttle lose the efficiency of system can be improved greatly.
To control the position of differential cylinder closed loop without using any throttle elements, a new idea that two speed variable pumps are used to compensate the non-symmetric flow of differential cylinder is carried out. According to the leaking property of the system, a speed offset principle is also proposed to eliminate the cavitation and tension caused by the leakage and condensation of oil, which makes the system be in the same state as a valve controlled circuit. This principle is explained theoretically and experimentally. Further the relationship that the pressures in cylinder chambers change with load and leakage, and the relationship between biasing speed and pre-load pressures in cylinder chambers are established. The research has proved that the new system has similar technique features as those of controlled with servo valves, but due to the elimination of all the throttle lose the efficiency of system can be improved greatly.
2004, 18(1).
Abstract:
To simulate the process of cold roll-forming process, a new method is adopted. The theoretical foundation of this method is an elastic-plastic large deformation spline finite strip method based on object-oriented programming. Combined with the computer graphics technology, the visual simulation of cold roll-forming is completed and the system is established. By analyzing common channel steel, the process is shown and explained including theory method, model and result display. So the simulation system is already a kind of mature and effective tool to analyze the process of cold roll forming.
To simulate the process of cold roll-forming process, a new method is adopted. The theoretical foundation of this method is an elastic-plastic large deformation spline finite strip method based on object-oriented programming. Combined with the computer graphics technology, the visual simulation of cold roll-forming is completed and the system is established. By analyzing common channel steel, the process is shown and explained including theory method, model and result display. So the simulation system is already a kind of mature and effective tool to analyze the process of cold roll forming.
2004, 18(1).
Abstract:
According to the theoretical analysis and calculation on the base of con-tinuous mass system, the simulation experimental investigation on active control of torsional vibration in a turbogenerator shaft system is conducted. A test installation with the excitation of generator motor and multi-stepped shaft system is established to simulate the torsional vibration of a turbogenerator rotor shaft system, and to examine the active control strategy presented. Some useful results are reached in the experimental study.
According to the theoretical analysis and calculation on the base of con-tinuous mass system, the simulation experimental investigation on active control of torsional vibration in a turbogenerator shaft system is conducted. A test installation with the excitation of generator motor and multi-stepped shaft system is established to simulate the torsional vibration of a turbogenerator rotor shaft system, and to examine the active control strategy presented. Some useful results are reached in the experimental study.
2004, 18(1).
Abstract:
In order to achieve active grinding control, a novel numerical control micropositioning workpiece table with a resolution of 6 nm has been developed. The table is driven by three piezoelectric actuators mounted on the base. An elastic structure with three half-notch flexure hinges is designed to apply preload to the piezoelectric actuators. The position of flexure hinges is also elaborately designed with consideration to reduce the bending deformation of the moving part. Three capacitive sensors are used to form close loop control system. Considering the table as a damped 3-DOF mass-spring system, the models of static and dynamic stiffness and error owing to the action of external forces have been established. In order to make the table have high resolution and positioning accuracy, an error compensation algorithm is implemented by using the established models. The experimental testing has been carried out to verify the performance of the workpiece table and the established models of the micropositioning workpiece table.
In order to achieve active grinding control, a novel numerical control micropositioning workpiece table with a resolution of 6 nm has been developed. The table is driven by three piezoelectric actuators mounted on the base. An elastic structure with three half-notch flexure hinges is designed to apply preload to the piezoelectric actuators. The position of flexure hinges is also elaborately designed with consideration to reduce the bending deformation of the moving part. Three capacitive sensors are used to form close loop control system. Considering the table as a damped 3-DOF mass-spring system, the models of static and dynamic stiffness and error owing to the action of external forces have been established. In order to make the table have high resolution and positioning accuracy, an error compensation algorithm is implemented by using the established models. The experimental testing has been carried out to verify the performance of the workpiece table and the established models of the micropositioning workpiece table.
2004, 18(1).
Abstract:
Multi-frictional disks are employed to transmit the torque in speeding wet clutch, and the oil thickness within frictional disks could be adjusted for practical output speeding. As oil combined with α-hydrocarbon or polyester is getting widely used as lubricant and the speeding wet clutch works within hydrodynamic lubrication, mixture lubrication, boundary lubrication and contact situation, established the thermal analysis model for investigating the behavior of frictional disks in speeding wet clutch, which covers the power-law fluid model, Patir-Cheng average flow model, GT asperity contact model, oil film inertia and heat effects, mean energy equation, and heat conduction equation. The formulas in the model are deduced. The numeral calculation and analysis for hydrodynamic lubrication and mixture lubrication are executed. Relationships and variations among transmitting torque, mean push pressure, output speed, and load are presented. Thermal effect should be considered during the hydrodynamic lubrication and larger transmitting torque makes earlier entrance to mixture lubrication.
Multi-frictional disks are employed to transmit the torque in speeding wet clutch, and the oil thickness within frictional disks could be adjusted for practical output speeding. As oil combined with α-hydrocarbon or polyester is getting widely used as lubricant and the speeding wet clutch works within hydrodynamic lubrication, mixture lubrication, boundary lubrication and contact situation, established the thermal analysis model for investigating the behavior of frictional disks in speeding wet clutch, which covers the power-law fluid model, Patir-Cheng average flow model, GT asperity contact model, oil film inertia and heat effects, mean energy equation, and heat conduction equation. The formulas in the model are deduced. The numeral calculation and analysis for hydrodynamic lubrication and mixture lubrication are executed. Relationships and variations among transmitting torque, mean push pressure, output speed, and load are presented. Thermal effect should be considered during the hydrodynamic lubrication and larger transmitting torque makes earlier entrance to mixture lubrication.
2004, 18(1).
Abstract:
The traditional lumped parameter model of fluid pipe is introduced and its drawbacks are pointed out. Furthermore, two suggestions are put forward to remove these drawbacks. Firstly, the structure of equivalent circuit is modified, and then the evaluation of equivalent fluid resistance is change to take the frequency-dependent friction into account. Both simulation and experiment prove that this model is precise to characterize the dynamic behaviors of fluid in pipe.
The traditional lumped parameter model of fluid pipe is introduced and its drawbacks are pointed out. Furthermore, two suggestions are put forward to remove these drawbacks. Firstly, the structure of equivalent circuit is modified, and then the evaluation of equivalent fluid resistance is change to take the frequency-dependent friction into account. Both simulation and experiment prove that this model is precise to characterize the dynamic behaviors of fluid in pipe.
2004, 18(1).
Abstract:
A method is proposed for the analysis of vibration signals from components of rotating machines, based on the wavelet packet transformation (WPT) and the underlying physical concepts of modulation mechanism. The method provides a finer analysis and better time-frequency localization capabilities than any other analysis methods. Both details and approximations are split into finer components and result in better-localized frequency ranges corresponding to each node of a wavelet packet tree. For the purpose of feature extraction, a hard threshold is given and the energy of the coefficients above the threshold is used, as a criterion for the selection of the best vector. The feature extraction of a vibration signal is accomplished by computing the reconstruction signal and its spectrum. When applied to a rolling bear vibration signal feature extraction, the proposed method can lead to be very effective.
A method is proposed for the analysis of vibration signals from components of rotating machines, based on the wavelet packet transformation (WPT) and the underlying physical concepts of modulation mechanism. The method provides a finer analysis and better time-frequency localization capabilities than any other analysis methods. Both details and approximations are split into finer components and result in better-localized frequency ranges corresponding to each node of a wavelet packet tree. For the purpose of feature extraction, a hard threshold is given and the energy of the coefficients above the threshold is used, as a criterion for the selection of the best vector. The feature extraction of a vibration signal is accomplished by computing the reconstruction signal and its spectrum. When applied to a rolling bear vibration signal feature extraction, the proposed method can lead to be very effective.
2004, 18(1).
Abstract:
Kinematics and its related issues of a 3-DOF in-parallel compliant mechanism are focused on. The micro manipulation application that requires high accuracy is developed. Design of the developed micromanipulator is based on the modified Delta mechanism. The main advantages of this manipulator are the use of only revolute flexure hinges and the capability to produce pure translation theoretically. The aim is to develop an efficient kinematic model used for positioning control. For this purpose, the Jacobian matrix relating the end effector position with the actuator displacements is obtained by both theoretical derivation and experiment. Aiming at the abnormality in the motion capabilities of the micromanipulator found in calibration experiment, the mobility of the compliant mechanism on a theoretical level is analyzed by using the matrix method and screw theory. Both the experimental and theoretical results have verified that the compliant mechanism does have rotational motion.
Kinematics and its related issues of a 3-DOF in-parallel compliant mechanism are focused on. The micro manipulation application that requires high accuracy is developed. Design of the developed micromanipulator is based on the modified Delta mechanism. The main advantages of this manipulator are the use of only revolute flexure hinges and the capability to produce pure translation theoretically. The aim is to develop an efficient kinematic model used for positioning control. For this purpose, the Jacobian matrix relating the end effector position with the actuator displacements is obtained by both theoretical derivation and experiment. Aiming at the abnormality in the motion capabilities of the micromanipulator found in calibration experiment, the mobility of the compliant mechanism on a theoretical level is analyzed by using the matrix method and screw theory. Both the experimental and theoretical results have verified that the compliant mechanism does have rotational motion.
2004, 18(1).
Abstract:
Nowadays there are several manual or half-automatic methods developed to drive the DNA micro-fluid of transgenic micro-injection and they often fail to control precisely the injection volume at picolitres level. Micro-size of the injector tip and viscosity of the DNA liquid also lead to dead area of volume control. An adequate way is presented utilizing temperature gradients to direct liquid flow in the pipette from the warmer to the cooler. Compared with the previous ones, this way is helpful in decreasing the dead area of controlling through decreasing the viscous rate of DNA liquid, which changes as the temperature varies. The DNA liquid is pushed by a sheer stress at the liquid-pipette interface, which emerges when viscous rate of the liquid changes. Preliminary experimenting results show the efficiency and convenience of this way in improving the system's characteristics.
Nowadays there are several manual or half-automatic methods developed to drive the DNA micro-fluid of transgenic micro-injection and they often fail to control precisely the injection volume at picolitres level. Micro-size of the injector tip and viscosity of the DNA liquid also lead to dead area of volume control. An adequate way is presented utilizing temperature gradients to direct liquid flow in the pipette from the warmer to the cooler. Compared with the previous ones, this way is helpful in decreasing the dead area of controlling through decreasing the viscous rate of DNA liquid, which changes as the temperature varies. The DNA liquid is pushed by a sheer stress at the liquid-pipette interface, which emerges when viscous rate of the liquid changes. Preliminary experimenting results show the efficiency and convenience of this way in improving the system's characteristics.
2004, 18(1).
Abstract:
The problem of dynamic relocation and phase-out of combined manufacturing plant and warehousing facilities in the supply chain are concerned. A multiple time/multiple objective model is proposed to maximize total profit during the time horizon, minimize total access time from the plant/warehouse facilities to its suppliers and customers and maximize aggregated local incentives during the time horizon. The relocation problem keeps the feature of NP-hard and with the traditional method the optimal result cannot be got easily. So a compact genetic algorithm (CGA) is introduced to solve the problem. In order to accelerate the convergence speed of the CGA, the least square approach is introduced and a fast compact genetic algorithm (fCGA) is proposed. Finally, simulation results with the fCGA are compared with the CGA and classical integer programming (IP). The results show that the fCGA proposed is of high efficiency for Pareto optimality problem.
The problem of dynamic relocation and phase-out of combined manufacturing plant and warehousing facilities in the supply chain are concerned. A multiple time/multiple objective model is proposed to maximize total profit during the time horizon, minimize total access time from the plant/warehouse facilities to its suppliers and customers and maximize aggregated local incentives during the time horizon. The relocation problem keeps the feature of NP-hard and with the traditional method the optimal result cannot be got easily. So a compact genetic algorithm (CGA) is introduced to solve the problem. In order to accelerate the convergence speed of the CGA, the least square approach is introduced and a fast compact genetic algorithm (fCGA) is proposed. Finally, simulation results with the fCGA are compared with the CGA and classical integer programming (IP). The results show that the fCGA proposed is of high efficiency for Pareto optimality problem.
2004, 18(1).
Abstract:
Based on the improved mode superposition method proposed by Z. D. Ma and I. Hagiwara, a precisely compensated efficient mode synthesis method is developed. The calculation procedure is discussed in detail and the truncation error is also analyzed. By comparison, it is shown that this method has a higher accuracy and a less calculation time than the general used ones.
Based on the improved mode superposition method proposed by Z. D. Ma and I. Hagiwara, a precisely compensated efficient mode synthesis method is developed. The calculation procedure is discussed in detail and the truncation error is also analyzed. By comparison, it is shown that this method has a higher accuracy and a less calculation time than the general used ones.
2004, 18(1).
Abstract:
Based on the beginning, propagating and ending mechanism of rotating-stall cell, the relation between the pressure history signal and the pressure distribution along rotor circumference is proposed. The angular velocities of rotating-stall cell propagating are computed from time series picked by the pressure probes on a cross section. Self-relation calculating filtered the random noise of the pressure history data. The exciting load on rotor is computed by integral of filtered pressure signal along rotor circumference. By Prohl-Myklestad method, dynamical equations of rotor system are obtained. The dynamical response of rotor system is resolved by using Matlab system. Further more, the situation of more than one of stall cells is discussed. Two cases respectively from the natural gas compressor of some fertilizer plant and the CO2 compressor of some nitrogenous fertilizer plant demonstrate that both methods of calculating the load exerted on rotor by pressure fluctuation and resolving the dynamic response of rotor are available and the characteristics of frequency spectrum of rotating stall are correct.
Based on the beginning, propagating and ending mechanism of rotating-stall cell, the relation between the pressure history signal and the pressure distribution along rotor circumference is proposed. The angular velocities of rotating-stall cell propagating are computed from time series picked by the pressure probes on a cross section. Self-relation calculating filtered the random noise of the pressure history data. The exciting load on rotor is computed by integral of filtered pressure signal along rotor circumference. By Prohl-Myklestad method, dynamical equations of rotor system are obtained. The dynamical response of rotor system is resolved by using Matlab system. Further more, the situation of more than one of stall cells is discussed. Two cases respectively from the natural gas compressor of some fertilizer plant and the CO2 compressor of some nitrogenous fertilizer plant demonstrate that both methods of calculating the load exerted on rotor by pressure fluctuation and resolving the dynamic response of rotor are available and the characteristics of frequency spectrum of rotating stall are correct.
2004, 18(1).
Abstract:
Soft sensor is widely used in industrial process control. It plays an important role to improve the quality of product and assure safety in production. The core of soft sensor is to construct soft sensing model. A new soft sensing modeling method based on support vector machine (SVM) is proposed. SVM is a new machine learning method based on statistical learning theory and is powerful for the problem characterized by small sample, nonlinearity, high dimension and local minima. The proposed methods are applied to the estimation of frozen point of light diesel oil in distillation column. The estimated outputs of soft sensing model based on SVM match the real values of frozen point and follow varying trend of frozen point very well. Experiment results show that SVM provides a new effective method for soft sensing modeling and has promising application in industrial process applications.
Soft sensor is widely used in industrial process control. It plays an important role to improve the quality of product and assure safety in production. The core of soft sensor is to construct soft sensing model. A new soft sensing modeling method based on support vector machine (SVM) is proposed. SVM is a new machine learning method based on statistical learning theory and is powerful for the problem characterized by small sample, nonlinearity, high dimension and local minima. The proposed methods are applied to the estimation of frozen point of light diesel oil in distillation column. The estimated outputs of soft sensing model based on SVM match the real values of frozen point and follow varying trend of frozen point very well. Experiment results show that SVM provides a new effective method for soft sensing modeling and has promising application in industrial process applications.
2004, 18(1).
Abstract:
Based on the control scheme of force and position, the controlling and testing system of metal V-belt type CVT is developed. Having taken account of the complex nonlinear characteristics of the CVT shift dynamics and the saturation and nonlinear characteristics of the speed ratio control valve, the speed ratio fuzzy controller based on the speed ratio feedback is designed. The experiment results show that the developed speed ratio control system is practical and feasible.
Based on the control scheme of force and position, the controlling and testing system of metal V-belt type CVT is developed. Having taken account of the complex nonlinear characteristics of the CVT shift dynamics and the saturation and nonlinear characteristics of the speed ratio control valve, the speed ratio fuzzy controller based on the speed ratio feedback is designed. The experiment results show that the developed speed ratio control system is practical and feasible.
2004, 18(1).
Abstract:
The manufacturing status has great effect on the product's quality. Now measuring data can be automatically sent to database in computer by interfaces. Based on the client/server design, management information system (MIS) of a company is set up by Pow-erBuilder and SQL Server. Statistic parameters can be automatically com-puted and control curves can be plotted on time, which can bring great conven-ience to the ISO quality certification. Searching and analyzing on the database system can give useful information to the administrator to improve the quality of products.
The manufacturing status has great effect on the product's quality. Now measuring data can be automatically sent to database in computer by interfaces. Based on the client/server design, management information system (MIS) of a company is set up by Pow-erBuilder and SQL Server. Statistic parameters can be automatically com-puted and control curves can be plotted on time, which can bring great conven-ience to the ISO quality certification. Searching and analyzing on the database system can give useful information to the administrator to improve the quality of products.
2004, 18(1).
Abstract:
The element of pesedospectral-multiwavelet-Galerkin method, and how to combine it with penalty method for treating boundary conditions are given. Multiwavelet bases don't overlap on the given scale, and possess the same compact set in a group of several functions, so they can be directly used to the numerical discretion on the finite interval. Numerical tests show that general boundary conditions can be enforced with the penalty method, and that pesedospectral-multiwavelet-Galerkin method can well track the solutions' development. This also proves that pesedospectral-multiwavelet-Galerkin method is effective.
The element of pesedospectral-multiwavelet-Galerkin method, and how to combine it with penalty method for treating boundary conditions are given. Multiwavelet bases don't overlap on the given scale, and possess the same compact set in a group of several functions, so they can be directly used to the numerical discretion on the finite interval. Numerical tests show that general boundary conditions can be enforced with the penalty method, and that pesedospectral-multiwavelet-Galerkin method can well track the solutions' development. This also proves that pesedospectral-multiwavelet-Galerkin method is effective.
2004, 18(1).
Abstract:
The current method of case-based design (CBD) can be well practiced for configuration design in which design experience knowledge is involved. However, since the design case is confined to a certain application domain, it is difficult for CBD to be applied to conceptual design process that develops concepts to meet design specifications. Firstly, a function factor description space is erected to provide an exhibition room for all functions of design cases. Next, the approach for identifying the space state of function factor in description space is proposed, including the determination of the similarities between function factors of design case. And then a general object-oriented representation for design case is presented by bringing the class of function and in-out flow into the current case representation. Finally, a living example for electro-pet design that illustrates the implementation of the method for case-based conceptual design based on distributed design case repositories is described.
The current method of case-based design (CBD) can be well practiced for configuration design in which design experience knowledge is involved. However, since the design case is confined to a certain application domain, it is difficult for CBD to be applied to conceptual design process that develops concepts to meet design specifications. Firstly, a function factor description space is erected to provide an exhibition room for all functions of design cases. Next, the approach for identifying the space state of function factor in description space is proposed, including the determination of the similarities between function factors of design case. And then a general object-oriented representation for design case is presented by bringing the class of function and in-out flow into the current case representation. Finally, a living example for electro-pet design that illustrates the implementation of the method for case-based conceptual design based on distributed design case repositories is described.
2004, 18(1).
Abstract:
New shift schedule for automatic transmission is proposed from the point of view of saving energy. The bench-test of automatic shift adopting this shift schedule is done on automatic transmission's test-bed. The experimental results show the shift schedule is correct. This shift schedule has enriched the theory of vehicle automatic maneuvering and will improve the efficiency of hydrodynamic drive system of the vehicle.
New shift schedule for automatic transmission is proposed from the point of view of saving energy. The bench-test of automatic shift adopting this shift schedule is done on automatic transmission's test-bed. The experimental results show the shift schedule is correct. This shift schedule has enriched the theory of vehicle automatic maneuvering and will improve the efficiency of hydrodynamic drive system of the vehicle.
2004, 18(1).
Abstract:
The simulation model of a valve control hydraulic system with long pipe is established in Simulink4.0, and then the step responses of the systems with difference pipe parameters are investigated by simulation. Simulation results show that the long pipes will slow down the step response of system and make it fluctuate periodically. The results of simulation conform to the results of experiment on the whole, which proves the mathematic model is correct.
The simulation model of a valve control hydraulic system with long pipe is established in Simulink4.0, and then the step responses of the systems with difference pipe parameters are investigated by simulation. Simulation results show that the long pipes will slow down the step response of system and make it fluctuate periodically. The results of simulation conform to the results of experiment on the whole, which proves the mathematic model is correct.
2004, 18(1).
Abstract:
There are many welding fixture layout design problems of flexible parts in body-in-white assembly process, which directly cause body assemble variation. The fixture layout design quality is mainly influenced by the position and quantity of fixture locators and clamps. A general analysis model of flexible assembles deformation caused by fixture is set up based on “N-2-1” locating principle, in which the locator and clamper are treated as the same fixture layout elements. An analysis model for the flexible part deformation in fixturing is set up in order to obtain the optimization object function and constraints accordingly. The final fixture element layout could be obtained through global optimal research by using improved genetic algorithm, which effectively decreases fixture elements layout influence on flexible assembles deformation.
There are many welding fixture layout design problems of flexible parts in body-in-white assembly process, which directly cause body assemble variation. The fixture layout design quality is mainly influenced by the position and quantity of fixture locators and clamps. A general analysis model of flexible assembles deformation caused by fixture is set up based on “N-2-1” locating principle, in which the locator and clamper are treated as the same fixture layout elements. An analysis model for the flexible part deformation in fixturing is set up in order to obtain the optimization object function and constraints accordingly. The final fixture element layout could be obtained through global optimal research by using improved genetic algorithm, which effectively decreases fixture elements layout influence on flexible assembles deformation.
2004, 18(1).
Abstract:
Using premium casing connections instead of API ones is one of the most effective technique to prevent casing failure. The factors contribute to the strength of premium casing connections are studied with FEA and full-scale test. The criterions are presented that ensure the connection's strength higher than the pipe. At the same time, the method is given to decrease the peak stress of the connection so as to improve its anticorruption property. At last, full-scale tests are done to test the strength of the connections designed with the method described, the results show that the connection's strength is higher than the pipe. This indicated that the method described is effective in designing premium casing connection.
Using premium casing connections instead of API ones is one of the most effective technique to prevent casing failure. The factors contribute to the strength of premium casing connections are studied with FEA and full-scale test. The criterions are presented that ensure the connection's strength higher than the pipe. At the same time, the method is given to decrease the peak stress of the connection so as to improve its anticorruption property. At last, full-scale tests are done to test the strength of the connections designed with the method described, the results show that the connection's strength is higher than the pipe. This indicated that the method described is effective in designing premium casing connection.
2004, 18(1).
Abstract:
In order to resolve the problems of machining non-axisymmetric aspheric lens, which is short of flexibility in mould grinding and needs high accuracy CNC machine center in globe diamond wheel grinding, a new parallel grinding method that utilizes common arc diamond wheel is put forward. Base on the approach calculation of machining locus, the advantages of parallel grinding that machines non-axisymmetric aspheric lens by 2.5-axis CNC machine center have been obtained. The results of grinding ex-periment show the new method can meet the need of grinding high accuracy non-axisymmetric aspheric lens.
In order to resolve the problems of machining non-axisymmetric aspheric lens, which is short of flexibility in mould grinding and needs high accuracy CNC machine center in globe diamond wheel grinding, a new parallel grinding method that utilizes common arc diamond wheel is put forward. Base on the approach calculation of machining locus, the advantages of parallel grinding that machines non-axisymmetric aspheric lens by 2.5-axis CNC machine center have been obtained. The results of grinding ex-periment show the new method can meet the need of grinding high accuracy non-axisymmetric aspheric lens.
2004, 18(1).
Abstract:
An automatic seam tracking system used in submerged arc welding is presented. In the system, the linear CCD vision sensor is installed in front of the welding torch. Laser structure light emitted by the semiconductor laser irradiates on a slant to work-piece surface and forms a structure light strip on work-piece surface. Scatter light of the strip is received by linear CCD on top of the seam and the image information of seam can be obtained. By way of image processing and applying Fuzzy-P controller in tracking process, automatic seam tracking has been realized accurately. Anti-disturbing ability of the system to work-piece surface status has been enhanced largely by classified microadjustment of torch height.
An automatic seam tracking system used in submerged arc welding is presented. In the system, the linear CCD vision sensor is installed in front of the welding torch. Laser structure light emitted by the semiconductor laser irradiates on a slant to work-piece surface and forms a structure light strip on work-piece surface. Scatter light of the strip is received by linear CCD on top of the seam and the image information of seam can be obtained. By way of image processing and applying Fuzzy-P controller in tracking process, automatic seam tracking has been realized accurately. Anti-disturbing ability of the system to work-piece surface status has been enhanced largely by classified microadjustment of torch height.
2004, 18(1).
Abstract:
FMS is a sort of highly automatic machining system，how to ensure part quality is master key to system highly active running. At first, series of machining dimension and process capability of flexible manufacturing system(FMS), is analyzed. Result of its, strong self-correlation of data series shows that time series analysis is applicable to data series analyzed. Based on-line modeling and forecasting for data series, principle and method of feedback compensation control is pro-posed. On a foundation of the virtual instrument platform, Labview of national instrument (NI), FMS dimen-sion and process capability monitoring system(monitoring system) is developed. In practice, it is proved that part quality and process capability of FMS are greatly improved.
FMS is a sort of highly automatic machining system，how to ensure part quality is master key to system highly active running. At first, series of machining dimension and process capability of flexible manufacturing system(FMS), is analyzed. Result of its, strong self-correlation of data series shows that time series analysis is applicable to data series analyzed. Based on-line modeling and forecasting for data series, principle and method of feedback compensation control is pro-posed. On a foundation of the virtual instrument platform, Labview of national instrument (NI), FMS dimen-sion and process capability monitoring system(monitoring system) is developed. In practice, it is proved that part quality and process capability of FMS are greatly improved.
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