2005 Vol.18(3)
Display Mode： |
2005, 19(3).
Abstract:
A physical value mapping (PVM) algorithm based on finite element mesh from the stamped part in stamping process to the product is presented. In order to improve the efficiency of the PVM algorithm, a search way from the mesh of the product to the mesh of the stamped part will be adopted. At the same time, the search process is divided into two steps: entire search (ES) and local search (LS), which improve the searching efficiency. The searching area is enlarged to avoid missing projection elements in ES process. An arc-length method is introduced in LS process. The validity is confirmed by the results of the complex industry-forming product.
A physical value mapping (PVM) algorithm based on finite element mesh from the stamped part in stamping process to the product is presented. In order to improve the efficiency of the PVM algorithm, a search way from the mesh of the product to the mesh of the stamped part will be adopted. At the same time, the search process is divided into two steps: entire search (ES) and local search (LS), which improve the searching efficiency. The searching area is enlarged to avoid missing projection elements in ES process. An arc-length method is introduced in LS process. The validity is confirmed by the results of the complex industry-forming product.
2005, 19(3).
Abstract:
Combining with the development of automated manual transmission (AMT), the various throttle control demands are analyzed under different working conditions of AMT such as tracking acceleration pedal, start, shift and so on. Based on simulation, the responding throttle control strategies are proposed, and a simple but effective throttle control method is presented. The testing results have proved that the strategies are effective for improving the pedal tracking precision and the qualities of start and shift.
Combining with the development of automated manual transmission (AMT), the various throttle control demands are analyzed under different working conditions of AMT such as tracking acceleration pedal, start, shift and so on. Based on simulation, the responding throttle control strategies are proposed, and a simple but effective throttle control method is presented. The testing results have proved that the strategies are effective for improving the pedal tracking precision and the qualities of start and shift.
2005, 19(3).
Abstract:
A novel powder metallurgy (P/M) material with high wear resistance is developed in order to decrease the wear and lubricant-leakage of a diesel engine valve guide. The friction and wear tests of this material are conducted. It indicates that the wear resistance of the newly developed P/M material has been improved and much better than that of the formerly used alloy steel. Moreover, three different sealing structures are designed and theoretically analyzed with respect to the characteristic of hydrodynamic sealing. Through comparative experiments of component leakage and engine run-in for different valve guide structures, it proves that the structure with a machined sealing groove but not installed with a seal-ring cannot only reduce the specific lubricant consumption (SLC) of cylinder head, but also decrease the wear of valve stem and valve guide.
A novel powder metallurgy (P/M) material with high wear resistance is developed in order to decrease the wear and lubricant-leakage of a diesel engine valve guide. The friction and wear tests of this material are conducted. It indicates that the wear resistance of the newly developed P/M material has been improved and much better than that of the formerly used alloy steel. Moreover, three different sealing structures are designed and theoretically analyzed with respect to the characteristic of hydrodynamic sealing. Through comparative experiments of component leakage and engine run-in for different valve guide structures, it proves that the structure with a machined sealing groove but not installed with a seal-ring cannot only reduce the specific lubricant consumption (SLC) of cylinder head, but also decrease the wear of valve stem and valve guide.
2005, 19(3).
Abstract:
In order to balance the contradiction between the demand of high precision and that of short time interval of model computing for the power plant simulator, a set of simulated mathematical models are constructed. The model describes the cylinder wall temperature located at four key positions of the high pressure cylinder. The simulated model is confirmed to be not only simple but also precise via comparison between the simulated results and the automatic data of a power plant.
In order to balance the contradiction between the demand of high precision and that of short time interval of model computing for the power plant simulator, a set of simulated mathematical models are constructed. The model describes the cylinder wall temperature located at four key positions of the high pressure cylinder. The simulated model is confirmed to be not only simple but also precise via comparison between the simulated results and the automatic data of a power plant.
2005, 19(3).
Abstract:
The recently developed European flaw assessment procedure, structural integrity assessment procedure(SINTAP) is applied to assessment for welded joints of the API 5L X65 pipeline steel with an assumed embedded flaw and surface flaw at the weld toe. As one of the basic input data, fracture toughness crack tip opening displacement (CTOD) tests are conducted at 0 ℃ and performed according to the requirements of the standard of BS7448. For the heat affected zone (HAZ) speci-mens, the microstructure observation is performed to insure that the tip of the crack is located in the coarse grain zone. The result explains the dispersity of the test values. In structural integrity assess-ment procedure-fracture assessment diagram(SINTAP FAD) method, the failure curves of welded joints at level 1 and 3 are derived from the tensile test results. The results of the assessment show that all assessment points are located within the failure lines of analysis level 1 and 3. So the welded joint of the pipeline is safe. This study laid the foundation of application of SINTAP to pipeline structure assessment.
The recently developed European flaw assessment procedure, structural integrity assessment procedure(SINTAP) is applied to assessment for welded joints of the API 5L X65 pipeline steel with an assumed embedded flaw and surface flaw at the weld toe. As one of the basic input data, fracture toughness crack tip opening displacement (CTOD) tests are conducted at 0 ℃ and performed according to the requirements of the standard of BS7448. For the heat affected zone (HAZ) speci-mens, the microstructure observation is performed to insure that the tip of the crack is located in the coarse grain zone. The result explains the dispersity of the test values. In structural integrity assess-ment procedure-fracture assessment diagram(SINTAP FAD) method, the failure curves of welded joints at level 1 and 3 are derived from the tensile test results. The results of the assessment show that all assessment points are located within the failure lines of analysis level 1 and 3. So the welded joint of the pipeline is safe. This study laid the foundation of application of SINTAP to pipeline structure assessment.
2005, 19(3).
Abstract:
The dynamical behaviors of logistic map(May's model) and duffing equation are studied through fractal dimension of time series at different parameters. It is shown that the parameters of dynamical behaviors can be identified effectively by the curve of fractal dimension with parameter increments. For further verification, the relation between the fractional dimension of time series and rotational speed can be used to identify critical speed effectively by using this method to a plate Jeffoctt rotor system. The numerical and experimental result indicates that the identification of critical parameters is effective.
The dynamical behaviors of logistic map(May's model) and duffing equation are studied through fractal dimension of time series at different parameters. It is shown that the parameters of dynamical behaviors can be identified effectively by the curve of fractal dimension with parameter increments. For further verification, the relation between the fractional dimension of time series and rotational speed can be used to identify critical speed effectively by using this method to a plate Jeffoctt rotor system. The numerical and experimental result indicates that the identification of critical parameters is effective.
2005, 19(3).
Abstract:
A digital model is presented for the purpose of design, manufacture and measurement of hypoid gear, based on the non-uniform rational B-spline surface (NURBS) method. The digital model and the function-oriented active design technique are combined to form a new design method for hypoid gears. The method is well adaptable to CNC bevel gear cutting machines and CNC-controlled gear inspection machines, and can be used to create the initial machine tool cutting location data or program measurement path. The presented example verifies the method is correct.
A digital model is presented for the purpose of design, manufacture and measurement of hypoid gear, based on the non-uniform rational B-spline surface (NURBS) method. The digital model and the function-oriented active design technique are combined to form a new design method for hypoid gears. The method is well adaptable to CNC bevel gear cutting machines and CNC-controlled gear inspection machines, and can be used to create the initial machine tool cutting location data or program measurement path. The presented example verifies the method is correct.
2005, 19(3).
Abstract:
The deformation characters and load status of the blank's potential fracture zone are analyzed at the moment when blank is approaching to punch corner in drawing process of cone shape part. Based on tension instability theory, the formula for calculating fracture limit load of cone shape part in drawing process is derived. Also, the formula is analyzed and verified by experiment.
The deformation characters and load status of the blank's potential fracture zone are analyzed at the moment when blank is approaching to punch corner in drawing process of cone shape part. Based on tension instability theory, the formula for calculating fracture limit load of cone shape part in drawing process is derived. Also, the formula is analyzed and verified by experiment.
2005, 19(3).
Abstract:
To simulate steady airflows inside of wall-flow diesel particulate filters (DPF) with different reverse blowing pipes collocation, a mathematical model of the flow in a DPF is established by an equivalent continuum approach. The experimental results agree well with the theoretical values calculated from the model. Simulation shows that the velocity and the pressure distribution of the filters in the regenerative process are key factors to the filter's regeneration. How to decrease the mal-distribution of the flow in the filter and how to achieve the better regenerative performance at the least cost of air consumption in the regenerative process are the ultimate goals of the study. Calculation and experiments show that the goals can be realized through adjusting the angle of two reverse blowing pipes and their relative location suitably.
To simulate steady airflows inside of wall-flow diesel particulate filters (DPF) with different reverse blowing pipes collocation, a mathematical model of the flow in a DPF is established by an equivalent continuum approach. The experimental results agree well with the theoretical values calculated from the model. Simulation shows that the velocity and the pressure distribution of the filters in the regenerative process are key factors to the filter's regeneration. How to decrease the mal-distribution of the flow in the filter and how to achieve the better regenerative performance at the least cost of air consumption in the regenerative process are the ultimate goals of the study. Calculation and experiments show that the goals can be realized through adjusting the angle of two reverse blowing pipes and their relative location suitably.
2005, 19(3).
Abstract:
In order to enhance the effect of corneal grafting, an assisting microsurgical robot has been developed. As one of principal issues for the robotic system design, type and size synthesis of the robotic mechanism is discussed. For this purpose, timeline subtask is analyzed with surgical component motion in manual corneal grafting microsurgery, as the reference of robotic mechanism synthesis. On the basis of study on the kinematic correlation between the arm structures and the wrist structures, configuration of joint is determined for the surgical task and motion in type synthesis of the mechanism. The objective for size synthesis of robotic mechanism is optimization of the mechanism dexterity as a manipulation capability. The condition number based on Jacob matrix is chosen as dexterity measure of the mechanism. The prototype is developed.
In order to enhance the effect of corneal grafting, an assisting microsurgical robot has been developed. As one of principal issues for the robotic system design, type and size synthesis of the robotic mechanism is discussed. For this purpose, timeline subtask is analyzed with surgical component motion in manual corneal grafting microsurgery, as the reference of robotic mechanism synthesis. On the basis of study on the kinematic correlation between the arm structures and the wrist structures, configuration of joint is determined for the surgical task and motion in type synthesis of the mechanism. The objective for size synthesis of robotic mechanism is optimization of the mechanism dexterity as a manipulation capability. The condition number based on Jacob matrix is chosen as dexterity measure of the mechanism. The prototype is developed.
2005, 19(3).
Abstract:
Optical-electronic autocollimation method is commonly used to measure straightness of precision guides in engineering application. However, the traditional fixed interval optical-electronic autocollimation method is not suitable for measuring straightness of an air-bearing guide with a long air-bearing bush or a precision straight guide with a long slide-carriage, because the air-bearing bush and the slide-carriage are actually taken as a big bridgeboard bigger than the length of the bridge-board with the reflector, which is about 1/4~1/2 of total length of the measured guide. If straightness is measured according to the traditional method, only a few points are sampled so that the guide straightness can not be evaluated fully or accurately. In order to solve the problem, an alterable measuring interval method is proposed for straightness measurement based on analyzing the mutual relations and effects among the tilting angle of the reflector, the length of the bridgeboard, the measuring interval and the straightness of the guide. A straightness calculation model is also developed using the method, and the errors stemming from the method proposed are introduced in brief. A precision air-bearing guide with a long air-bearing bush is measured and evaluated using the method proposed, and the actual measurement and evaluation results prove that the method is correct in theory and practical in operation. The method proposed gives an effective and flexible solution to the straightness measurement of the precision guide with long slide-carriage or air-bearing bush in application. It is an extension of the traditional optical-electronic autocollimation method for straightness measurement.
Optical-electronic autocollimation method is commonly used to measure straightness of precision guides in engineering application. However, the traditional fixed interval optical-electronic autocollimation method is not suitable for measuring straightness of an air-bearing guide with a long air-bearing bush or a precision straight guide with a long slide-carriage, because the air-bearing bush and the slide-carriage are actually taken as a big bridgeboard bigger than the length of the bridge-board with the reflector, which is about 1/4~1/2 of total length of the measured guide. If straightness is measured according to the traditional method, only a few points are sampled so that the guide straightness can not be evaluated fully or accurately. In order to solve the problem, an alterable measuring interval method is proposed for straightness measurement based on analyzing the mutual relations and effects among the tilting angle of the reflector, the length of the bridgeboard, the measuring interval and the straightness of the guide. A straightness calculation model is also developed using the method, and the errors stemming from the method proposed are introduced in brief. A precision air-bearing guide with a long air-bearing bush is measured and evaluated using the method proposed, and the actual measurement and evaluation results prove that the method is correct in theory and practical in operation. The method proposed gives an effective and flexible solution to the straightness measurement of the precision guide with long slide-carriage or air-bearing bush in application. It is an extension of the traditional optical-electronic autocollimation method for straightness measurement.
2005, 19(3).
Abstract:
A computer model for the performance simulation of vehicles equipped with traction drive continuously variable transmission (CVT) is presented. The model integrates the traction drive CVT subsystem into an existing overall vehicle system. The characteristics of engine output torque are formulated using neural networks, and torque converter is modeled using lookup tables. Component inputs and outputs are coupled in the dynamic equations and interfaces in the powertrain system. The model simulation can provide evaluation of vehicle performance in drivability, fuel economy and emission levels for various drive ranges prior to the prototyping of the vehicle. As a design tool, the model assists engineers in understanding the effect of powertrain components on vehicle performance and making decisions in the selection of key design parameters. The model is implemented in the MATLAB/Simulink environment. The performance simulation of a test vehicle is included as a nu-merical example to illustrate the effectiveness of the model.
A computer model for the performance simulation of vehicles equipped with traction drive continuously variable transmission (CVT) is presented. The model integrates the traction drive CVT subsystem into an existing overall vehicle system. The characteristics of engine output torque are formulated using neural networks, and torque converter is modeled using lookup tables. Component inputs and outputs are coupled in the dynamic equations and interfaces in the powertrain system. The model simulation can provide evaluation of vehicle performance in drivability, fuel economy and emission levels for various drive ranges prior to the prototyping of the vehicle. As a design tool, the model assists engineers in understanding the effect of powertrain components on vehicle performance and making decisions in the selection of key design parameters. The model is implemented in the MATLAB/Simulink environment. The performance simulation of a test vehicle is included as a nu-merical example to illustrate the effectiveness of the model.
2005, 19(3).
Abstract:
It is discussed with the design and implementation of an architecture for a mobile robot to navigate in dynamic and unknown indoor environments. The architecture is based on the framework of Open Robot Control Software at KTH (OROCOS@KTH), which is also discussed and evaluated to navigate indoor efficiently, a new algorithm named door-like-exit detection is proposed which employs 2D feature of a door and extracts key points of pathway from the raw data of a laser scanner. As a hybrid architecture, it is decomposed into several basic components which can be classified as either deliberative or reactive. Each component can concurrently execute and communicate with another. It is expansible and transferable and its components are reusable.
It is discussed with the design and implementation of an architecture for a mobile robot to navigate in dynamic and unknown indoor environments. The architecture is based on the framework of Open Robot Control Software at KTH (OROCOS@KTH), which is also discussed and evaluated to navigate indoor efficiently, a new algorithm named door-like-exit detection is proposed which employs 2D feature of a door and extracts key points of pathway from the raw data of a laser scanner. As a hybrid architecture, it is decomposed into several basic components which can be classified as either deliberative or reactive. Each component can concurrently execute and communicate with another. It is expansible and transferable and its components are reusable.
2005, 19(3).
Abstract:
The multi-impact characteristics and failure mechanism of two kinds of automotive engine chain made in China are studied through engine assembly and road-drive tests. The worn surface morphologies of rubbing area between pin, bush and roller are also analyzed based on scanning electron microscope. The results show that the main wear mechanism of automotive engine chain is fatigue wear, and its failure mechanism is the forming, extending and flaking of cracks on top layer of pin and bush. In addition, the material, hot-treatment method and shaping technique for roller have a great influence upon the resistance to multi-impact. Ensuring sufficient strength and plasticity of roller, as well as adopting suitable shaping technique are the effective method to increase its resistance to multi-impact.
The multi-impact characteristics and failure mechanism of two kinds of automotive engine chain made in China are studied through engine assembly and road-drive tests. The worn surface morphologies of rubbing area between pin, bush and roller are also analyzed based on scanning electron microscope. The results show that the main wear mechanism of automotive engine chain is fatigue wear, and its failure mechanism is the forming, extending and flaking of cracks on top layer of pin and bush. In addition, the material, hot-treatment method and shaping technique for roller have a great influence upon the resistance to multi-impact. Ensuring sufficient strength and plasticity of roller, as well as adopting suitable shaping technique are the effective method to increase its resistance to multi-impact.
2005, 19(3).
Abstract:
Tolerance analysis of a planetary reducer is conducted. By focusing the serially-arranged parts in the central line and setting an appropriate dimension as a “gap”, worst-case tolerance analysis method and statistical (RSS) tolerance analysis are used, and then a tolerance-analyzing tool CE/TOL is introduced. The acceptable value range of the “gap” is from 1.5 mm to 3.5 mm. While worst-case analysis rejects the design, RSS accepts it by a more realistic result with the law of probability accounted. With the help of CE/TOL and CAD software Pro/E, all components' dimensions and tolerances are assigned and modified, and more detailed and more comprehensible results are gives out.
Tolerance analysis of a planetary reducer is conducted. By focusing the serially-arranged parts in the central line and setting an appropriate dimension as a “gap”, worst-case tolerance analysis method and statistical (RSS) tolerance analysis are used, and then a tolerance-analyzing tool CE/TOL is introduced. The acceptable value range of the “gap” is from 1.5 mm to 3.5 mm. While worst-case analysis rejects the design, RSS accepts it by a more realistic result with the law of probability accounted. With the help of CE/TOL and CAD software Pro/E, all components' dimensions and tolerances are assigned and modified, and more detailed and more comprehensible results are gives out.
2005, 19(3).
Abstract:
Based on the analyses of the structural feature and the function requirements of new style bottle cap, the two fundamental components, the 1ining washer and the outer body, are abstracted as a plate and a cylinder with thin wal1 respectively. For simulating the deformation of the 1ining washer under equiaxia1 pressure, the modified Lagrangian finite element analysis is applied on the 228 triangular elements. Under assembly pressure, the plastoelastic deformation of both the 1ining washer and the outer body are studied in terms of Tresca's yield criterion and the limitation of the plastic deformation is presented when the two components are assembled into one unit. For the production of this kind of bottle cover, experiments are carried out by carefully measuring the changes of the diameter of 1ining washer as well as that of the outer body. It is shown that results from the experiments have a good agreement with the theoretical calculation and the maximum value of the allowable pressure has successfully been used in the design of newly developed bottle cap production system.
Based on the analyses of the structural feature and the function requirements of new style bottle cap, the two fundamental components, the 1ining washer and the outer body, are abstracted as a plate and a cylinder with thin wal1 respectively. For simulating the deformation of the 1ining washer under equiaxia1 pressure, the modified Lagrangian finite element analysis is applied on the 228 triangular elements. Under assembly pressure, the plastoelastic deformation of both the 1ining washer and the outer body are studied in terms of Tresca's yield criterion and the limitation of the plastic deformation is presented when the two components are assembled into one unit. For the production of this kind of bottle cover, experiments are carried out by carefully measuring the changes of the diameter of 1ining washer as well as that of the outer body. It is shown that results from the experiments have a good agreement with the theoretical calculation and the maximum value of the allowable pressure has successfully been used in the design of newly developed bottle cap production system.
2005, 19(3).
Abstract:
A high temperature displacement sensor based on the principle of eddy-current is investigated. A new temperature compensation technique by using eddy-current effect is presented to satisfy the special requirement at high temperature up to 550 °C. The experiment shows that the temperature compensation technique leads to good temperature stability for the sensors. The variation of the sensi-tivity as well as the temperature drift of the sensor with temperature compensation technique is only about 7.4% and 90~350 mV at 550 °C compared with that at room temperature, and that of the sensor without temperature compensation technique is about 31.2% and 2~3 V at 550 °C compared with that at room temperature. A new dynamic calibration method for the eddy-current displacement sensor is presented, which is very easy to be realized especially in high frequency and at high temperatures. The high temperature displacement sensors developed are successfully used at temperature up to 550 °C in a magnetic bearing system for more than 100 h.
A high temperature displacement sensor based on the principle of eddy-current is investigated. A new temperature compensation technique by using eddy-current effect is presented to satisfy the special requirement at high temperature up to 550 °C. The experiment shows that the temperature compensation technique leads to good temperature stability for the sensors. The variation of the sensi-tivity as well as the temperature drift of the sensor with temperature compensation technique is only about 7.4% and 90~350 mV at 550 °C compared with that at room temperature, and that of the sensor without temperature compensation technique is about 31.2% and 2~3 V at 550 °C compared with that at room temperature. A new dynamic calibration method for the eddy-current displacement sensor is presented, which is very easy to be realized especially in high frequency and at high temperatures. The high temperature displacement sensors developed are successfully used at temperature up to 550 °C in a magnetic bearing system for more than 100 h.
2005, 19(3).
Abstract:
A ground-based hardware-in-the-loop (HIL) simulation system with hydraulically driven Stewart platform for spacecraft docking simulation is presented. The system is used for simulating docking process of the on-orbit spacecraft. Principle and structure of the six-degree-of-freedom simulation system are introduced. The docking process dynamic of the vehicles is modeled. Experiment results and mathematical simulation data are compared to validating the simulation system. The comparisons of the results prove that the simulation system proposed can effectively simulate the on-orbit docking process of the spacecraft.
A ground-based hardware-in-the-loop (HIL) simulation system with hydraulically driven Stewart platform for spacecraft docking simulation is presented. The system is used for simulating docking process of the on-orbit spacecraft. Principle and structure of the six-degree-of-freedom simulation system are introduced. The docking process dynamic of the vehicles is modeled. Experiment results and mathematical simulation data are compared to validating the simulation system. The comparisons of the results prove that the simulation system proposed can effectively simulate the on-orbit docking process of the spacecraft.
2005, 19(3).
Abstract:
The instantaneous kinematics of a special 3-UPU parallel platform manipulator is discussed. First, the instantaneous motions of the 3-UPU manipulator in four kinds of positions and a special manipulator are studied by reciprocal screw theory. Then, the principal screws in one of four positions are obtained. It is shown that the moving platform has five degrees of freedom (DOF) in the initial position or after a translation along the z-axis; In the generic position, the mechanism only has three DOF, moreover the three DOF characteristics are different in different position. The instantaneous kinematic characteristics of alike 3-UPU mechanisms are very different in different position and special structure. The results presented are important to the use of alike 3-UPU parallel manipulator and contribute to the mechanism theory.
The instantaneous kinematics of a special 3-UPU parallel platform manipulator is discussed. First, the instantaneous motions of the 3-UPU manipulator in four kinds of positions and a special manipulator are studied by reciprocal screw theory. Then, the principal screws in one of four positions are obtained. It is shown that the moving platform has five degrees of freedom (DOF) in the initial position or after a translation along the z-axis; In the generic position, the mechanism only has three DOF, moreover the three DOF characteristics are different in different position. The instantaneous kinematic characteristics of alike 3-UPU mechanisms are very different in different position and special structure. The results presented are important to the use of alike 3-UPU parallel manipulator and contribute to the mechanism theory.
2005, 19(3).
Abstract:
The manipulation and constraint equations are established by considering the pure rolling motion in a dexterous hand as two passive joints. According to mapping relation among the motion of the system, the differential kinematics and mobility are studied. The minimal structure for realizing the task motion of the object is obtained, and the conditions for dexterous manipulation are presented. Finally, some rolling manipulations are used as examples to demonstrate the applicability of approach proposed.
The manipulation and constraint equations are established by considering the pure rolling motion in a dexterous hand as two passive joints. According to mapping relation among the motion of the system, the differential kinematics and mobility are studied. The minimal structure for realizing the task motion of the object is obtained, and the conditions for dexterous manipulation are presented. Finally, some rolling manipulations are used as examples to demonstrate the applicability of approach proposed.
2005, 19(3).
Abstract:
The modeling and motion control of a universal part feeder is addressed. The feeder consists of a flat plate (or called bed) and a part placed on the plate. The bed can vibrate side-by-side (in x axis), back and forth (in y axis), clockwise and counter clockwise (about z axis), actuated by three linear motors (voice coils). When the bed does these vibrations, the part placed on the plat will have position and/or orientation change due to the interaction between the two contact surfaces. By controlling the ways in which the plate vibrates, the position and orientation of the part can be controlled. The two vibration profiles of the bed are investigated in the research: the high-low vibration mode and the bang-bang vibration mode. The motion equations of the bed and the part as well as the control schemes for the high-low vibration mode are presented. Both simulation and real-time testing verify the system's dynamic model and indicate the feasibilities of the developed control laws.
The modeling and motion control of a universal part feeder is addressed. The feeder consists of a flat plate (or called bed) and a part placed on the plate. The bed can vibrate side-by-side (in x axis), back and forth (in y axis), clockwise and counter clockwise (about z axis), actuated by three linear motors (voice coils). When the bed does these vibrations, the part placed on the plat will have position and/or orientation change due to the interaction between the two contact surfaces. By controlling the ways in which the plate vibrates, the position and orientation of the part can be controlled. The two vibration profiles of the bed are investigated in the research: the high-low vibration mode and the bang-bang vibration mode. The motion equations of the bed and the part as well as the control schemes for the high-low vibration mode are presented. Both simulation and real-time testing verify the system's dynamic model and indicate the feasibilities of the developed control laws.
2005, 19(3).
Abstract:
A new hybrid MMA-MGCMMA (HMM) algorithm for solving topology optimization problems is presented. This algorithm combines the method of moving asymptotes (MMA) algorithm and the modified globally convergent version of the method of moving asymptotes (MGCMMA) algorithm in the optimization process. This algorithm preserves the advantages of both MMA and MGCMMA. The optimizer is switched from MMA to MGCMMA automatically, depending on the numerical oscillation value existing in the calculation. This algorithm can improve calculation efficiency and accelerate convergence compared with simplex MMA or MGCMMA algorithms, which is proven with an example.
A new hybrid MMA-MGCMMA (HMM) algorithm for solving topology optimization problems is presented. This algorithm combines the method of moving asymptotes (MMA) algorithm and the modified globally convergent version of the method of moving asymptotes (MGCMMA) algorithm in the optimization process. This algorithm preserves the advantages of both MMA and MGCMMA. The optimizer is switched from MMA to MGCMMA automatically, depending on the numerical oscillation value existing in the calculation. This algorithm can improve calculation efficiency and accelerate convergence compared with simplex MMA or MGCMMA algorithms, which is proven with an example.
2005, 19(3).
Abstract:
A new B-spline surface reconstruction method from layer data based on deformable model is presented. An initial deformable surface, which is represented as a closed cylinder, is firstly given. The surface is subject to internal forces describing its implicit smoothness property and external forces attracting it toward the layer data points. And then finite element method is adopted to solve its energy minimization problem, which results a bicubic closed B-spline surface with C2 continuity. The proposed method can provide a smoothness and accurate surface model directly from the layer data, without the need to fit cross-sectional curves and make them compatible. The feasibility of the pro-posed method is verified by the experimental results.
A new B-spline surface reconstruction method from layer data based on deformable model is presented. An initial deformable surface, which is represented as a closed cylinder, is firstly given. The surface is subject to internal forces describing its implicit smoothness property and external forces attracting it toward the layer data points. And then finite element method is adopted to solve its energy minimization problem, which results a bicubic closed B-spline surface with C2 continuity. The proposed method can provide a smoothness and accurate surface model directly from the layer data, without the need to fit cross-sectional curves and make them compatible. The feasibility of the pro-posed method is verified by the experimental results.
2005, 19(3).
Abstract:
For the narrowband of liner charge-coupled device (CCD) receiver and the imaging rule that cylindrical lens system can compress round facula into narrow and long one, the system is simplified and light force can concentrate on a strip facula. Considered the effective CCD length and selection of lens parameters, the system can be optimized. Correspondingly to the CCD pixels, the ray is composed of much angle information. By widening the parallel ray or increasing the lens aperture, luminous flux can be ensured when oblique incidence. Meanwhile, the effective working range can also be improved. Based on the experimental data, cylindrical system could be applied in accurate angle measurement. It has been proved feasible that the cylindrical system can be used in anchor behavior study for liquid crystal (LC) case. The low-power He-Ne laser cylindrical system can carry out the previous effect in high power laser spherical system.
For the narrowband of liner charge-coupled device (CCD) receiver and the imaging rule that cylindrical lens system can compress round facula into narrow and long one, the system is simplified and light force can concentrate on a strip facula. Considered the effective CCD length and selection of lens parameters, the system can be optimized. Correspondingly to the CCD pixels, the ray is composed of much angle information. By widening the parallel ray or increasing the lens aperture, luminous flux can be ensured when oblique incidence. Meanwhile, the effective working range can also be improved. Based on the experimental data, cylindrical system could be applied in accurate angle measurement. It has been proved feasible that the cylindrical system can be used in anchor behavior study for liquid crystal (LC) case. The low-power He-Ne laser cylindrical system can carry out the previous effect in high power laser spherical system.
2005, 19(3).
Abstract:
The presented system consists of field devices, a control system and a host computer system. The field devices, which are composed of an in-pipe micro-robot, a displacement sensor, a curvature sensor, and an inner surface measurement unit, can go into the pipe to get the data of displacement and axis curvature, and the shape data of the inner surface. With the conic-shape laser beam shot by the inner surface measurement unit, the intersectional curve between the laser beam and the inner-surface of the tested pipe can be calculated in the local coordination system (LCS) of the inner surface measurement unit. The relation between the LCS and the global coordination system (GCS) can be deduced, too. After the robot reaches the end of the pipe, all measured intersectional curves can be translated into the same coordination system to become a point cloud of the inner surface of the pipe according to the relations between LCS and GCS. Depending on this points cloud, the CAD model of the inner surface of the pipe can be reconstructed easily with reverse engineering tools, and the feature of flaw of the pipe can be obtained with flaw analysis tools.
The presented system consists of field devices, a control system and a host computer system. The field devices, which are composed of an in-pipe micro-robot, a displacement sensor, a curvature sensor, and an inner surface measurement unit, can go into the pipe to get the data of displacement and axis curvature, and the shape data of the inner surface. With the conic-shape laser beam shot by the inner surface measurement unit, the intersectional curve between the laser beam and the inner-surface of the tested pipe can be calculated in the local coordination system (LCS) of the inner surface measurement unit. The relation between the LCS and the global coordination system (GCS) can be deduced, too. After the robot reaches the end of the pipe, all measured intersectional curves can be translated into the same coordination system to become a point cloud of the inner surface of the pipe according to the relations between LCS and GCS. Depending on this points cloud, the CAD model of the inner surface of the pipe can be reconstructed easily with reverse engineering tools, and the feature of flaw of the pipe can be obtained with flaw analysis tools.
2005, 19(3).
Abstract:
Research has been done on an energy-saving type of hydraulic workover rig. This rig can recover and reuse the potential energy which is released by the pipestring when lowered, and the equipped power of this rig is only one third of an ordinary rig. The structure and theory of this rig are introduced. The mathematical model of lowering the pipestring is established and a simulation analysis is conducted. Through simulation some conclusions are obtained: The lighter the pipestring is, the less velocity of lowering the pipestring is; The smaller the throttle valve path area is, the less velocity of lowering the pipestring is; Different air vessel volumes have no evident effect on the pipestring lowering velocity. The actual measure results prove that the simulation results are right. Finally, the energy-saving effect of this rig is proved by the field test results.
Research has been done on an energy-saving type of hydraulic workover rig. This rig can recover and reuse the potential energy which is released by the pipestring when lowered, and the equipped power of this rig is only one third of an ordinary rig. The structure and theory of this rig are introduced. The mathematical model of lowering the pipestring is established and a simulation analysis is conducted. Through simulation some conclusions are obtained: The lighter the pipestring is, the less velocity of lowering the pipestring is; The smaller the throttle valve path area is, the less velocity of lowering the pipestring is; Different air vessel volumes have no evident effect on the pipestring lowering velocity. The actual measure results prove that the simulation results are right. Finally, the energy-saving effect of this rig is proved by the field test results.
2005, 19(3).
Abstract:
With the idea of the phononic crystals, a thin rectangular plate with two-dimensional periodic structure is designed. Flexural wave band structures of such a plate with infinite structure are calculated with the plane-wave expansion (PWE) method, and directional band gaps are found in the ΓX direction. The acceleration frequency response in the ΓX direction of such a plate with finite structure is simulated with the finite element method and verified with a vibration experiment. The frequency ranges of sharp drops in the calculated and measured acceleration frequency response curves are in basic agreement with those in the band structures. Thin plate is a widely used component in the engineering structures. The existence of band gaps in such periodic structures gives a new idea in vibration control of thin plates.
With the idea of the phononic crystals, a thin rectangular plate with two-dimensional periodic structure is designed. Flexural wave band structures of such a plate with infinite structure are calculated with the plane-wave expansion (PWE) method, and directional band gaps are found in the ΓX direction. The acceleration frequency response in the ΓX direction of such a plate with finite structure is simulated with the finite element method and verified with a vibration experiment. The frequency ranges of sharp drops in the calculated and measured acceleration frequency response curves are in basic agreement with those in the band structures. Thin plate is a widely used component in the engineering structures. The existence of band gaps in such periodic structures gives a new idea in vibration control of thin plates.
2005, 19(3).
Abstract:
Metaball-based constraint deformation technique is used to change the definition of r, the straight-line distance from a space point to a constraint center in the original calculation of the potential function. By replacing the parameter of the parametrized surface w with the straight-line distance r, a method of building transition surfaces according to connected boundary curves and skeleton curves is proposed. The method has no restrictions on boundary curves that control the space shapes of transition surfaces or on types of skeleton curves, thus transition surfaces, which reach C1 continuity and are more abundant in shapes and natural, can be obtained.
Metaball-based constraint deformation technique is used to change the definition of r, the straight-line distance from a space point to a constraint center in the original calculation of the potential function. By replacing the parameter of the parametrized surface w with the straight-line distance r, a method of building transition surfaces according to connected boundary curves and skeleton curves is proposed. The method has no restrictions on boundary curves that control the space shapes of transition surfaces or on types of skeleton curves, thus transition surfaces, which reach C1 continuity and are more abundant in shapes and natural, can be obtained.
2005, 19(3).
Abstract:
Based on the analysis of the-state-of-the-art of pressure compensation of underwater hydraulic systems (UHSs), a new method of pressure compensation of UHSs, whose hydraulic power unit is in the atmospheric circumstance, is proposed. And a pilot-operated relief valve with pressure compensation is realized. The pressure compensation precision is guaranteed by direct detection. Its dynamic performance and stability are improved by a dynamic feedback. Theoretical study, simulation and experiment show that the pilot-operated relief valve with pressure compensation has a fine property of tracking underwater ambient pressure and meet the requirement of underwater ambient pressure compensation.
Based on the analysis of the-state-of-the-art of pressure compensation of underwater hydraulic systems (UHSs), a new method of pressure compensation of UHSs, whose hydraulic power unit is in the atmospheric circumstance, is proposed. And a pilot-operated relief valve with pressure compensation is realized. The pressure compensation precision is guaranteed by direct detection. Its dynamic performance and stability are improved by a dynamic feedback. Theoretical study, simulation and experiment show that the pilot-operated relief valve with pressure compensation has a fine property of tracking underwater ambient pressure and meet the requirement of underwater ambient pressure compensation.
2005, 19(3).
Abstract:
The dynamics differential equations are constructed, and the initial conditions are also given. Simulation shows the following conclusions: The water pressure in cylinder has great instantaneous pulsation and phase step when outlet valve or inlet valve opens, but is more gently in other time; The volume efficiency is influenced by the output pressure slightly, and decreases as the working rotational speed increases; When the inherent frequency of the valves is integer multiple of the working frequency, the volume efficiency of system will decrease evidently.
The dynamics differential equations are constructed, and the initial conditions are also given. Simulation shows the following conclusions: The water pressure in cylinder has great instantaneous pulsation and phase step when outlet valve or inlet valve opens, but is more gently in other time; The volume efficiency is influenced by the output pressure slightly, and decreases as the working rotational speed increases; When the inherent frequency of the valves is integer multiple of the working frequency, the volume efficiency of system will decrease evidently.
2005, 19(3).
Abstract:
According to the characteristics of a complex cover panel, its geometry shape is described by the NURBS surface with great description capability. With the reference to the surface classification determined by Gauss curvature, the proportion of the mid-surface area between before and after being developed is derived from the displacement variation of the mid-surface in the normal vector direction of the sheet metal during the sheet metal forming process. Hereby, based on the curve development theory in differential geometry, a novel diagonal point by point surface development method is put forward to estimate a complex cover panel's blank contour efficiently. By comparing the sample's development result of diagonal point by point surface development method with that of available one-step method, the validity of the proposed surface development method is verified.
According to the characteristics of a complex cover panel, its geometry shape is described by the NURBS surface with great description capability. With the reference to the surface classification determined by Gauss curvature, the proportion of the mid-surface area between before and after being developed is derived from the displacement variation of the mid-surface in the normal vector direction of the sheet metal during the sheet metal forming process. Hereby, based on the curve development theory in differential geometry, a novel diagonal point by point surface development method is put forward to estimate a complex cover panel's blank contour efficiently. By comparing the sample's development result of diagonal point by point surface development method with that of available one-step method, the validity of the proposed surface development method is verified.
2005, 19(3).
Abstract:
A fast 3D reconstruction method based on structured light to measure various parameters of the raceway groove is presented. Digital parallel grating stripes distributed with sine density are projected onto the raceway groove by a DLP projector, and distorting of stripes is happened on the raceway. Simultaneously, aided by three-step phase-shifting approach, three images covered by different stripes are obtained by a high-resolution CCD camera at the same location, thus a more accuracy local topography can be obtained. And then the bearing is rotated on a high precision computer controlled rotational stage. Three images are also obtained as the former step at next planned location triggered by the motor. After one cycle, all images information is combined through the mosaics. As a result, the 3D information of raceway groove can be gained. Not only geometric properties but also surface flaws can be extracted by software. A preliminary hardware system has been built, with which some geometric parameters have been extracted from recon-structed local topography.
A fast 3D reconstruction method based on structured light to measure various parameters of the raceway groove is presented. Digital parallel grating stripes distributed with sine density are projected onto the raceway groove by a DLP projector, and distorting of stripes is happened on the raceway. Simultaneously, aided by three-step phase-shifting approach, three images covered by different stripes are obtained by a high-resolution CCD camera at the same location, thus a more accuracy local topography can be obtained. And then the bearing is rotated on a high precision computer controlled rotational stage. Three images are also obtained as the former step at next planned location triggered by the motor. After one cycle, all images information is combined through the mosaics. As a result, the 3D information of raceway groove can be gained. Not only geometric properties but also surface flaws can be extracted by software. A preliminary hardware system has been built, with which some geometric parameters have been extracted from recon-structed local topography.
2005, 19(3).
Abstract:
An optical imaging system and a configuration characteristic algorithm are presented to reduce the difficulties in extracting intact characters image with weak contrast, in recognizing characters on fast moving beer bottles. The system consists of a hardware subsystem, including a rotating device, CCD, 16 mm focus lens, a frame grabber card, a penetrating lighting and a computer, and a software subsystem. The software subsystem performs pretreatment, character segmentation and character recognition. In the pre-treatment, the original image is filtered with preset threshold to remove isolated spots. Then the horizontal projection and the vertical projection are used respectively to retrieve the character segmentation. Subse-quently, the configuration characteristic algorithm is applied to recognize the characters. The experimental results demonstrate that this system can recognize the characters on beer bottles accurately and effectively; the algorithm is proven fast, stable and robust, making it suitable in the industrial environment.
An optical imaging system and a configuration characteristic algorithm are presented to reduce the difficulties in extracting intact characters image with weak contrast, in recognizing characters on fast moving beer bottles. The system consists of a hardware subsystem, including a rotating device, CCD, 16 mm focus lens, a frame grabber card, a penetrating lighting and a computer, and a software subsystem. The software subsystem performs pretreatment, character segmentation and character recognition. In the pre-treatment, the original image is filtered with preset threshold to remove isolated spots. Then the horizontal projection and the vertical projection are used respectively to retrieve the character segmentation. Subse-quently, the configuration characteristic algorithm is applied to recognize the characters. The experimental results demonstrate that this system can recognize the characters on beer bottles accurately and effectively; the algorithm is proven fast, stable and robust, making it suitable in the industrial environment.
2005, 19(3).
Abstract:
A method is put forward to realize the recognition and guiding of initial welding position. The weld seams are marked with black lines, which simplify the computational complexity of image processing greatly. A two-time template matching method has been advanced to search for the target point, which is simple and has higher calculation speed. According to the depth computing principle with the special point matching using binocular stereovision, the initial welding position can be confirmed by calculating the middle point of the perpendicular line of two radials in the space. Taking the welding of propellant fuel container for example, good results are obtained with the algorithms. Finally, similar method for terminating welding position is also advanced.
A method is put forward to realize the recognition and guiding of initial welding position. The weld seams are marked with black lines, which simplify the computational complexity of image processing greatly. A two-time template matching method has been advanced to search for the target point, which is simple and has higher calculation speed. According to the depth computing principle with the special point matching using binocular stereovision, the initial welding position can be confirmed by calculating the middle point of the perpendicular line of two radials in the space. Taking the welding of propellant fuel container for example, good results are obtained with the algorithms. Finally, similar method for terminating welding position is also advanced.
2005, 19(3).
Abstract:
A coding-based method to solve the image matching problems in stereovision measurement is presented. The solution is to add and append an identity ID to the retro-reflect point, so it can be identified efficiently under the complicated circumstances and has the characteristics of rotation, zooming, and deformation independence. Its design architecture and implementation process in details based on the theory of stereovision measurement are described. The method is effective on reducing processing data time, improving accuracy of image matching and automation of measuring system through experiments.
A coding-based method to solve the image matching problems in stereovision measurement is presented. The solution is to add and append an identity ID to the retro-reflect point, so it can be identified efficiently under the complicated circumstances and has the characteristics of rotation, zooming, and deformation independence. Its design architecture and implementation process in details based on the theory of stereovision measurement are described. The method is effective on reducing processing data time, improving accuracy of image matching and automation of measuring system through experiments.
2005, 19(3).
Abstract:
A hybrid control approach is proposed to achieve the desired performance. Firstly a robust input shaper is designed to reduce the transient vibration and residual vibration of the container efficiently. Then a simple fuzzy logic controller is designed to eliminate the residual vibration completely in order to guarantee the positioning precision. Such a hybrid approach is simple in structure and readily realizable. Simulation results verify the fine performance of this hybrid control approach. It can achieve perfect elimination of residual vibration and concise positioning of the container load, and it is robust to parameter variations (mainly for cable length) and external disturbances.
A hybrid control approach is proposed to achieve the desired performance. Firstly a robust input shaper is designed to reduce the transient vibration and residual vibration of the container efficiently. Then a simple fuzzy logic controller is designed to eliminate the residual vibration completely in order to guarantee the positioning precision. Such a hybrid approach is simple in structure and readily realizable. Simulation results verify the fine performance of this hybrid control approach. It can achieve perfect elimination of residual vibration and concise positioning of the container load, and it is robust to parameter variations (mainly for cable length) and external disturbances.
2005, 19(3).
Abstract:
The effect of vibratory stress relief (VSR) is usually evaluated with the indirect method of observing the change of amplitude frequency response characteristics of structures. A new kind of evaluating method of VSR based on the ultrasonic time-of-arrival method (UTM), which can obtain the residual stress directly through measuring the propagation time of ultrasonic wave in the material, is presented. At first, the principle of the measuring method of residual stress based on UTM is analyzed. Then the measuring system of the method is described, which is in virtue of ultrasonic flaw detector and high-sampling-rate digital oscillograph. And a set of calibration system that contains a piece of standard specimen is also introduced. Experimental results prove the relation between the residual stress and the propagation time of ultrasonic in workpieces. Finally, the measuring and calibration systems are applied in evaluating the effect of VSR. The final test results show that the method is effective.
The effect of vibratory stress relief (VSR) is usually evaluated with the indirect method of observing the change of amplitude frequency response characteristics of structures. A new kind of evaluating method of VSR based on the ultrasonic time-of-arrival method (UTM), which can obtain the residual stress directly through measuring the propagation time of ultrasonic wave in the material, is presented. At first, the principle of the measuring method of residual stress based on UTM is analyzed. Then the measuring system of the method is described, which is in virtue of ultrasonic flaw detector and high-sampling-rate digital oscillograph. And a set of calibration system that contains a piece of standard specimen is also introduced. Experimental results prove the relation between the residual stress and the propagation time of ultrasonic in workpieces. Finally, the measuring and calibration systems are applied in evaluating the effect of VSR. The final test results show that the method is effective.
E-mail Alerts
