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RSS2012 Vol. 31, No. 8
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2012, 31(8): 1205-1210.
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Abstract:
To get users' exciting requirements as the goal of conceptual design, integrating KANO model, an acquisition model for product functional requirements based on system evolutionary laws was proposed. Firstly, the maturity of the product was determined and then functional analysis was made. Secondly, evolutionary analysis of every functional module was made to find their corresponding evolutionary solutions based on system evolutionary laws. Then evolutionary solutions were considered with classification analysis based on market research. Finally, the excitatory demand was resulted as design targets in order to meet customers' exctatory demand. The present model could obtain the functional requirements systematically. The results could meet users' excitatory demand which were hardly generated from market research. The model was applied to find suited functional requirements of drinking fountains, and prove to be effective.
To get users' exciting requirements as the goal of conceptual design, integrating KANO model, an acquisition model for product functional requirements based on system evolutionary laws was proposed. Firstly, the maturity of the product was determined and then functional analysis was made. Secondly, evolutionary analysis of every functional module was made to find their corresponding evolutionary solutions based on system evolutionary laws. Then evolutionary solutions were considered with classification analysis based on market research. Finally, the excitatory demand was resulted as design targets in order to meet customers' exctatory demand. The present model could obtain the functional requirements systematically. The results could meet users' excitatory demand which were hardly generated from market research. The model was applied to find suited functional requirements of drinking fountains, and prove to be effective.
2012, 31(8): 1211-1217.
Abstract:
Data exchange is one of the key technologies of collaborative design, and Product Structure Data become the important exchanging data among collaborative enterprise. Based on analyzing the actual related work of data exchange problem, this article brings forward a method of Virtual PDM, which is a extensive PDM built on general PDM, to solve the Product Structure Date exchange problem in heterogeneous PDM systems of each enterprise. Firstly, the data model of STEP PDM scheme and XML-based product structure data is described. The framework of VPDM-Based Product Structure Date exchange is proposed and the parts being composed the whole framework are analyzed. And then, the technology framework based on J2EE is constructed. At last, the system configuration implementing the framework and the data exchange sequence are listed. Meanwhile, files are shown, which are generated for query and return by instance demand. Using this method, Product Structure Data among heterogeneous PDM systems has been successful exchanged.
Data exchange is one of the key technologies of collaborative design, and Product Structure Data become the important exchanging data among collaborative enterprise. Based on analyzing the actual related work of data exchange problem, this article brings forward a method of Virtual PDM, which is a extensive PDM built on general PDM, to solve the Product Structure Date exchange problem in heterogeneous PDM systems of each enterprise. Firstly, the data model of STEP PDM scheme and XML-based product structure data is described. The framework of VPDM-Based Product Structure Date exchange is proposed and the parts being composed the whole framework are analyzed. And then, the technology framework based on J2EE is constructed. At last, the system configuration implementing the framework and the data exchange sequence are listed. Meanwhile, files are shown, which are generated for query and return by instance demand. Using this method, Product Structure Data among heterogeneous PDM systems has been successful exchanged.
2012, 31(8): 1218-1221.
Abstract:
In the field of aircraft manufacturing, interference-fit connection is a common structural connection method which can enhance the fatigue strength of interference-fit fasteners. Stress wave installation is a new method for installing easily the interference-fit fasteners that have large interference volumes. We use experiments to analyze the factors that influence the quality for installing the interference-fit hi-lock bolts of a certain model of aircraft during its manufacturing. The results show that the use of hi-lock bolts with large fillets and high-quality surface lubrication and the use of twin guns for loading can enhance its installation quality and that the high interference-fit installation method is not suitable for fasteners and sandwich materials with large difference in strength.
In the field of aircraft manufacturing, interference-fit connection is a common structural connection method which can enhance the fatigue strength of interference-fit fasteners. Stress wave installation is a new method for installing easily the interference-fit fasteners that have large interference volumes. We use experiments to analyze the factors that influence the quality for installing the interference-fit hi-lock bolts of a certain model of aircraft during its manufacturing. The results show that the use of hi-lock bolts with large fillets and high-quality surface lubrication and the use of twin guns for loading can enhance its installation quality and that the high interference-fit installation method is not suitable for fasteners and sandwich materials with large difference in strength.
2012, 31(8): 1222-1226.
Abstract:
The horizontal vibration is a key factor that affects riding comfort of high-speed elevators. The guiding system is one of the main parts leading to the horizontal vibration of elevators. In order to reduce the horizontal vibrations, we establish the mathematical models of one fourth of the total elevator car with a guide shoe. On the basis of the model, the differential equations and the state space model of x and y directions are given respectively. Then the generalized predictive PID (proportion integration differentiation) control strategy is designed by means of combining GPC (generalized predictive control) with PID. The simulation results show that the generalized predictive PID controller suppresses effectively the horizontal vibration of high-speed elevators, and it is better than PID controller.
The horizontal vibration is a key factor that affects riding comfort of high-speed elevators. The guiding system is one of the main parts leading to the horizontal vibration of elevators. In order to reduce the horizontal vibrations, we establish the mathematical models of one fourth of the total elevator car with a guide shoe. On the basis of the model, the differential equations and the state space model of x and y directions are given respectively. Then the generalized predictive PID (proportion integration differentiation) control strategy is designed by means of combining GPC (generalized predictive control) with PID. The simulation results show that the generalized predictive PID controller suppresses effectively the horizontal vibration of high-speed elevators, and it is better than PID controller.
2012, 31(8): 1227-1231.
Abstract:
The torsion fatigue testing machine is used as the experimental platform to study the dynamic working characteristics of the torsional vibration damper. The positive/inverse Fourier transform method is adopted to analyze the data obtained from the dynamic test of the damper. The dynamic working characteristic curves of the torsional vibration damper with different frequencies and amplitudes are revealed from the analyses. Based on that, the linearization process is conducted on the damping of the damper. Experimental results show that dynamic performance of the damper is not only related to the vibration amplitude, but also to the exciting frequency. Furthermore, the damper has typical nonlinear hysteretic characteristics.
The torsion fatigue testing machine is used as the experimental platform to study the dynamic working characteristics of the torsional vibration damper. The positive/inverse Fourier transform method is adopted to analyze the data obtained from the dynamic test of the damper. The dynamic working characteristic curves of the torsional vibration damper with different frequencies and amplitudes are revealed from the analyses. Based on that, the linearization process is conducted on the damping of the damper. Experimental results show that dynamic performance of the damper is not only related to the vibration amplitude, but also to the exciting frequency. Furthermore, the damper has typical nonlinear hysteretic characteristics.
2012, 31(8): 1232-1235.
Abstract:
Service-oriented manufacturing is new manufacturing mode fused of manufacturing and service. Enter-prise provided services constitute a virtual manufacturing alliance, and these service relations in the alliance form a complex service manufacturing network. In order to describe and analysis of the league of distribution and service relationship role, the present study defines the service-oriented manufacturing network. The role of node in the network and their relationships are revealed by evaluating the statistic parameters such as node strength, clustering coefficient based on the theory of complex weighted network in the paper. These parameters reveal enterprises in the service oriented manufacturing environment position and the mutual relationship. This result can be used to construct and manage the network and find or group collaborative partners. Finally, an example was verified.
Service-oriented manufacturing is new manufacturing mode fused of manufacturing and service. Enter-prise provided services constitute a virtual manufacturing alliance, and these service relations in the alliance form a complex service manufacturing network. In order to describe and analysis of the league of distribution and service relationship role, the present study defines the service-oriented manufacturing network. The role of node in the network and their relationships are revealed by evaluating the statistic parameters such as node strength, clustering coefficient based on the theory of complex weighted network in the paper. These parameters reveal enterprises in the service oriented manufacturing environment position and the mutual relationship. This result can be used to construct and manage the network and find or group collaborative partners. Finally, an example was verified.
2012, 31(8): 1236-1240.
Abstract:
As the fatigue life of tower crane is influenced by many uncertain factors, in this paper, the Grey System Theory is used to forecast the fatigue life of the tower crane. The model of GM ( 1,1 ) and the power model of GM ( 1,1 ) are respectively used to the prediction of fatigue life of lifting arm of QTZ630 under the load spectrum of actual conditions. It is shown that the life prediction error of the traditional Miner method is 43.7% ; and the error is decreased to 25.2% by using linear gray model of GM( 1,1 ) ; while the error based on the non-linear gray power model of GM( 1,1 ) is dropped to 23.2%. The life prediction result based on gray prediction method is inclined to safety, which indicates that the grey prediction offers a way to predict the fatigue life for tower crane. And it also have appropriate prospect in the life prediction field of tower crane for the high prediction accuracy and reliability.
As the fatigue life of tower crane is influenced by many uncertain factors, in this paper, the Grey System Theory is used to forecast the fatigue life of the tower crane. The model of GM ( 1,1 ) and the power model of GM ( 1,1 ) are respectively used to the prediction of fatigue life of lifting arm of QTZ630 under the load spectrum of actual conditions. It is shown that the life prediction error of the traditional Miner method is 43.7% ; and the error is decreased to 25.2% by using linear gray model of GM( 1,1 ) ; while the error based on the non-linear gray power model of GM( 1,1 ) is dropped to 23.2%. The life prediction result based on gray prediction method is inclined to safety, which indicates that the grey prediction offers a way to predict the fatigue life for tower crane. And it also have appropriate prospect in the life prediction field of tower crane for the high prediction accuracy and reliability.
2012, 31(8): 1241-1246.
Abstract:
The airflow field in a typical aeroengine beating chamber has been calculated with the commercial computational fluid dynamics software CFX 11. 0, taking into consideration the sealing structure of the ventilation hole and the airflow state equations. Then the effects of erating conditions such as rotational speed, air inflow volume, gap of the bearing chamber, the the structural parameters and ophydraulic diameter of the bearing chamber on the air-flow states are analyzed. The calculation results show preliminarily but clearly that the air inflow, ventilation hole and compressible air property have significant influence on the airflow states of the bearing chamber. The nondi-mensional tangential velocity decreases along the radial direction of the bearing chamber, but the radial and axial velocities change in a complicated manner. The rotational speed of the rotor, airflow volume and the hydraulic diameter of the bearing chamber have great influence on the nondimensional velocity distribution.
The airflow field in a typical aeroengine beating chamber has been calculated with the commercial computational fluid dynamics software CFX 11. 0, taking into consideration the sealing structure of the ventilation hole and the airflow state equations. Then the effects of erating conditions such as rotational speed, air inflow volume, gap of the bearing chamber, the the structural parameters and ophydraulic diameter of the bearing chamber on the air-flow states are analyzed. The calculation results show preliminarily but clearly that the air inflow, ventilation hole and compressible air property have significant influence on the airflow states of the bearing chamber. The nondi-mensional tangential velocity decreases along the radial direction of the bearing chamber, but the radial and axial velocities change in a complicated manner. The rotational speed of the rotor, airflow volume and the hydraulic diameter of the bearing chamber have great influence on the nondimensional velocity distribution.
2012, 31(8): 1247-1252.
Abstract:
An experimental study is carried out to prove that the grinding heat instead of high-frequency induction heat should be utilized to harden the surface of 48MnV microalloyed steel parts, through which the grinding process and surface hardening technique should be integrated. The mathematical model of grinding temperature is also established, and the changes in grinding temperature and cooling rate are measured. Furthermore, the grinding effect, hardening effect and the forming mechanism of grinding-hardening layers are investigated. The experimental results show that： 1 ) the estimated temperature is quite close to the measured temperature; hence the mathematical model can be utilized to optimize the processing parameters of the 48MnV microalloyed steel parts; 2) satisfactory grinding-hardening temperature and cooling rate can be achieved with the optimized processing parameters; 3) the grinding-hardening layer, the fine needlelike martensite in an entirely hardened zone, the martensite and ferrite in a transitional region have similar microstructures with those acquired with the high-frequency induction technique; 4) different from the forming mechanism of the high-frequency induction hardened layer, a higher grinding-hardening temperature is needed to compensate for shortertime austenitization; 5) because of the from surface to inside thermo-mechanical loading caused by grinding, the morphology of martensite changes from fine to thicker, then to finer, other than from thick to fine.
An experimental study is carried out to prove that the grinding heat instead of high-frequency induction heat should be utilized to harden the surface of 48MnV microalloyed steel parts, through which the grinding process and surface hardening technique should be integrated. The mathematical model of grinding temperature is also established, and the changes in grinding temperature and cooling rate are measured. Furthermore, the grinding effect, hardening effect and the forming mechanism of grinding-hardening layers are investigated. The experimental results show that： 1 ) the estimated temperature is quite close to the measured temperature; hence the mathematical model can be utilized to optimize the processing parameters of the 48MnV microalloyed steel parts; 2) satisfactory grinding-hardening temperature and cooling rate can be achieved with the optimized processing parameters; 3) the grinding-hardening layer, the fine needlelike martensite in an entirely hardened zone, the martensite and ferrite in a transitional region have similar microstructures with those acquired with the high-frequency induction technique; 4) different from the forming mechanism of the high-frequency induction hardened layer, a higher grinding-hardening temperature is needed to compensate for shortertime austenitization; 5) because of the from surface to inside thermo-mechanical loading caused by grinding, the morphology of martensite changes from fine to thicker, then to finer, other than from thick to fine.
2012, 31(8): 1253-1256.
Abstract:
A novel spatial parallel mechanism with two translations and two rotations (2T2R) is analysized, which is composed of two adjacent RPU limps and two adjacent SPS limps. Firstly based on Lie group theory, the degrees-of-freedom (DOFs) of the mechanism is calculated and the input paires is ehoosen. And then the analytical solution of position, velocity and acceleration for the mechanism are deduced exhaustivlly. Finally, a numeric example is given： a kinematic curve analysis is carried out by using Matlab, the virtual prototype model of the meahcnism is eonstrueted and kinematic simulation is eonducted by using Adams, kinematics simulation results is quite coincident with theoretical analysis. This work lay the foundation for the analysis of dynamics and control of the two translations and two rotations parallel mechanism, The present result provided theoretical basis for the analysis of dynamics and control, the design and practicality of the mechanism.
A novel spatial parallel mechanism with two translations and two rotations (2T2R) is analysized, which is composed of two adjacent RPU limps and two adjacent SPS limps. Firstly based on Lie group theory, the degrees-of-freedom (DOFs) of the mechanism is calculated and the input paires is ehoosen. And then the analytical solution of position, velocity and acceleration for the mechanism are deduced exhaustivlly. Finally, a numeric example is given： a kinematic curve analysis is carried out by using Matlab, the virtual prototype model of the meahcnism is eonstrueted and kinematic simulation is eonducted by using Adams, kinematics simulation results is quite coincident with theoretical analysis. This work lay the foundation for the analysis of dynamics and control of the two translations and two rotations parallel mechanism, The present result provided theoretical basis for the analysis of dynamics and control, the design and practicality of the mechanism.
2012, 31(8): 1257-1260.
Abstract:
A pipe cleaning robot is designed based on the analysis of pipe features in the central air conditioning being used in supermarkets and large office building. The robot system can be used for detecting and cleaning the rectangular pipe above-mentioned. The moving mechanism and cleaning brush lifting mechanism are selected, and the turning of moving mechanism and climbing over obstacle of moving mechanism is discussed in detail, finally the optimal design of transmission device of cleaning brush is done. The design is proved to be feasible and in a good agreement with that in practice.
A pipe cleaning robot is designed based on the analysis of pipe features in the central air conditioning being used in supermarkets and large office building. The robot system can be used for detecting and cleaning the rectangular pipe above-mentioned. The moving mechanism and cleaning brush lifting mechanism are selected, and the turning of moving mechanism and climbing over obstacle of moving mechanism is discussed in detail, finally the optimal design of transmission device of cleaning brush is done. The design is proved to be feasible and in a good agreement with that in practice.
2012, 31(8): 1261-1264.
Abstract:
During the fault diagnosis in gearbox, in order to achieve de-noising and demodulation simultaneously in the fault gear vibration signal, two different morphological operators are designed based on the mathematical morphological theory. For different signal processing purpose, the vibration signal can be de-noised and modulated with morphological operators. The procession results of simulated signal and real gear crack fault signal show that the combined operation can filter the impulse and stochastic noises, and improve signal-to-noise ratio, while the difference operation can extract the demodulated impulses in the signal, and reveal impulsion feature in fault signal. The proposed method is simple and fast in computation as only addition and subtraction operators are need. This method can be applied to the singal processing in online diagnosis for gearbox.
During the fault diagnosis in gearbox, in order to achieve de-noising and demodulation simultaneously in the fault gear vibration signal, two different morphological operators are designed based on the mathematical morphological theory. For different signal processing purpose, the vibration signal can be de-noised and modulated with morphological operators. The procession results of simulated signal and real gear crack fault signal show that the combined operation can filter the impulse and stochastic noises, and improve signal-to-noise ratio, while the difference operation can extract the demodulated impulses in the signal, and reveal impulsion feature in fault signal. The proposed method is simple and fast in computation as only addition and subtraction operators are need. This method can be applied to the singal processing in online diagnosis for gearbox.
2012, 31(8): 1265-1269.
Abstract:
The selection of strain gages is important in determining flight loads by strain gage measurement, which has large effects on the prediction of load equations. An improved genetic algorithm of selecting strain gages in the measurements of flight loads was proposed in this paper by considering the elimination of the irrelevant gages. Also, the performances of improved genetic algorithm were analyzed compared with those of exhaustive search and genetic algorithms. Further, the improved genetic algorithm was applied to select the strain gages in the load measurements of certain landing gear. The test example shows that the improved genetic algorithm in this paper could obtain the high-quality load equations with acceptable accuracy and small irrelevance.
The selection of strain gages is important in determining flight loads by strain gage measurement, which has large effects on the prediction of load equations. An improved genetic algorithm of selecting strain gages in the measurements of flight loads was proposed in this paper by considering the elimination of the irrelevant gages. Also, the performances of improved genetic algorithm were analyzed compared with those of exhaustive search and genetic algorithms. Further, the improved genetic algorithm was applied to select the strain gages in the load measurements of certain landing gear. The test example shows that the improved genetic algorithm in this paper could obtain the high-quality load equations with acceptable accuracy and small irrelevance.
2012, 31(8): 1270-1273.
Abstract:
This paper analyzes the mechanism model synthesis methods, uses numerical value count method to induce the relationship and formulas between the number of pairs in Assur Group, the number of links and pairs in the link, and the numbers of outer linked pairs, then analyzes and lists the eigenvalue of Assur groups which contain 2,4,6,8 links. Based on the eigenvalue of Assur Group, brings forward a new drawing method and corresponding rules for mechanism topology figure, uses this method to do mechanism transform can easily get large numbers of different configuration of same Assur Group and same eigenvalue, thus provides a new theory for planar mechanism model synthesis based on Assur Group. Finally uses Assur Group eigenvalue to do mechanism level distinguish and creative design, and proves this theory's validity by an example.
This paper analyzes the mechanism model synthesis methods, uses numerical value count method to induce the relationship and formulas between the number of pairs in Assur Group, the number of links and pairs in the link, and the numbers of outer linked pairs, then analyzes and lists the eigenvalue of Assur groups which contain 2,4,6,8 links. Based on the eigenvalue of Assur Group, brings forward a new drawing method and corresponding rules for mechanism topology figure, uses this method to do mechanism transform can easily get large numbers of different configuration of same Assur Group and same eigenvalue, thus provides a new theory for planar mechanism model synthesis based on Assur Group. Finally uses Assur Group eigenvalue to do mechanism level distinguish and creative design, and proves this theory's validity by an example.
2012, 31(8): 1274-1279.
Abstract:
It is difficult to understand the actual flow inside a centrifugal pump, whose design is still semi-empirical and semi-theoretical and whose prediction accuracy is not satisfactory. Thus, we establish a new model for predicting its performance. We combine the genetic algorithm with the BP neural network to conduct the optimal design of its performance parameters. We use the genetic algorithm to optimize the weighted values and threshold values of the BP neural network, and then use the BP algorithm to train the neural network, thus avoiding the local minimum values when the training is done with the BP neural network alone. We use some representative performance data of the centrifugal pump as training samples of the new model. The study results show that the BP neural network optimized with the genetic algorithm speeds up the convergence of the model and improves the training accuracy. Our method can serve as an effective theoretical basis for the optimal design of performance parameters of a centrifugal pump.
It is difficult to understand the actual flow inside a centrifugal pump, whose design is still semi-empirical and semi-theoretical and whose prediction accuracy is not satisfactory. Thus, we establish a new model for predicting its performance. We combine the genetic algorithm with the BP neural network to conduct the optimal design of its performance parameters. We use the genetic algorithm to optimize the weighted values and threshold values of the BP neural network, and then use the BP algorithm to train the neural network, thus avoiding the local minimum values when the training is done with the BP neural network alone. We use some representative performance data of the centrifugal pump as training samples of the new model. The study results show that the BP neural network optimized with the genetic algorithm speeds up the convergence of the model and improves the training accuracy. Our method can serve as an effective theoretical basis for the optimal design of performance parameters of a centrifugal pump.
2012, 31(8): 1280-1284.
Abstract:
In this paper, a novel parabola-rectangle flexural hinges is presented. According to the Castigliano's second theorem and calculus, the design equations for calculating the bending rigidity and stretching or compressing rigidity about the flexural hinges are derived. Based on the beam element with variational cross-section, the finite element model of the flexure hinges is established, and the calculation of the rigidity about the flexural hinges is ac-complished. In order to validate the correctness of design equations for calculating the bending rigidity and stretching or compressing rigidity, the comparison between the analytic and the FEM results is done. The effect of the geometric parameters on the performance of the parabola-rectangle flexural hinges is analyzed, and the comparison with the corner-filleted flexural hinges shows that the compliance and sensitivity to the load of parabola-rectangle flexural hinges are inferior to that of corner-filleted flexural hinges.
In this paper, a novel parabola-rectangle flexural hinges is presented. According to the Castigliano's second theorem and calculus, the design equations for calculating the bending rigidity and stretching or compressing rigidity about the flexural hinges are derived. Based on the beam element with variational cross-section, the finite element model of the flexure hinges is established, and the calculation of the rigidity about the flexural hinges is ac-complished. In order to validate the correctness of design equations for calculating the bending rigidity and stretching or compressing rigidity, the comparison between the analytic and the FEM results is done. The effect of the geometric parameters on the performance of the parabola-rectangle flexural hinges is analyzed, and the comparison with the corner-filleted flexural hinges shows that the compliance and sensitivity to the load of parabola-rectangle flexural hinges are inferior to that of corner-filleted flexural hinges.
2012, 31(8): 1285-1289.
Abstract:
In this paper, two kinds of 2-DOF parallel mechanisms are proposed to use as the actuator for plane sprayer. The dynamic equation of two mechanisms based on the Lagrange equation is derived, the two mechanisms on the terminal operating point (spray gun position) which do the circular and elliptical trajectory are simulated by using Matlab, the variation of driving force of mechanism active member were obtained. The present results provide the reference value for the selection and synthesis and control strategy of mechanism.
In this paper, two kinds of 2-DOF parallel mechanisms are proposed to use as the actuator for plane sprayer. The dynamic equation of two mechanisms based on the Lagrange equation is derived, the two mechanisms on the terminal operating point (spray gun position) which do the circular and elliptical trajectory are simulated by using Matlab, the variation of driving force of mechanism active member were obtained. The present results provide the reference value for the selection and synthesis and control strategy of mechanism.
2012, 31(8): 1290-1294.
Abstract:
The non-uniformity of vibration amplitude the lateral roughness of pavement. In order to study in the length direction of paver screed has great influence on non-uniformity of lateral vibration of asphalt paver screed, the screed was thought as a flexible body, and a coupled concrete paver was established. The flexible body's rigid and flexible model for compacting mechanism of asphalt dynamic control equations were built using FEA formula and the dynamic equations of coupled rigid and flexible system were deduced. These equations were solved by the Wilson-O method, and numerical simulation was carried out to investigate the distribution of acceleration and amplitude along the length direction of screed, the influence of frequency of tamping and vibrating mechanism on non-uniformity. A paver prototype was tested to verify the theoretic analysis results above. The results showed that： the flexible model of screed accorded with the actual vibration properties of screed; the non-uniformity can be reduced by optimizing the allocation of tamper mass, eccentric shaft mass and eccentricity on every section of screed.
The non-uniformity of vibration amplitude the lateral roughness of pavement. In order to study in the length direction of paver screed has great influence on non-uniformity of lateral vibration of asphalt paver screed, the screed was thought as a flexible body, and a coupled concrete paver was established. The flexible body's rigid and flexible model for compacting mechanism of asphalt dynamic control equations were built using FEA formula and the dynamic equations of coupled rigid and flexible system were deduced. These equations were solved by the Wilson-O method, and numerical simulation was carried out to investigate the distribution of acceleration and amplitude along the length direction of screed, the influence of frequency of tamping and vibrating mechanism on non-uniformity. A paver prototype was tested to verify the theoretic analysis results above. The results showed that： the flexible model of screed accorded with the actual vibration properties of screed; the non-uniformity can be reduced by optimizing the allocation of tamper mass, eccentric shaft mass and eccentricity on every section of screed.
2012, 31(8): 1295-1300.
Abstract:
In view of inner structure and complying with quality equivalent principle, a 2.5 inch mobile hard disk was modeled based on ANSYS/LS-DYNA. The non-linear mapping relation between structural parameters of the key components and drop impact response was built using FEM (finite element method) and experimental design. Drop impact processes of different head actuator arm thickness, cantilever thickness and pivot bearing stiffness were simulated in order to obtain training specimen for the ANN (artificial neutral network). The BP ANN prediction model was established. Multiple objective optimization algorithms for crashworthiness of mobile hard disk were analyzed based on ANN and GA (genetic algorithm). The results indicate that the method is effective and may provide theory gist of preferences in key part parameter design.
In view of inner structure and complying with quality equivalent principle, a 2.5 inch mobile hard disk was modeled based on ANSYS/LS-DYNA. The non-linear mapping relation between structural parameters of the key components and drop impact response was built using FEM (finite element method) and experimental design. Drop impact processes of different head actuator arm thickness, cantilever thickness and pivot bearing stiffness were simulated in order to obtain training specimen for the ANN (artificial neutral network). The BP ANN prediction model was established. Multiple objective optimization algorithms for crashworthiness of mobile hard disk were analyzed based on ANN and GA (genetic algorithm). The results indicate that the method is effective and may provide theory gist of preferences in key part parameter design.
2012, 31(8): 1301-1305,1310.
Abstract:
The boundary layer separation frequently happens to compressor blades under the non-design condition. Therefore, through making a slot at the tip region of two blades of a rotor for aspiration, we perform the numerical simulation of the boundary layer suction (BLS) of a double-stage counter-rotational compressor by using the entity slot and adding source terms. Then we make comparative study of the performance characteristics and internal flow field of the compressor before and after aspiration respectively. The study results show that the sucking of low-energy fluid near the rotor tip region can enhance the pressure ratio and efficiency of the compressor under various flow volumes,with its total pressure ratio increasing by about 1.25% and the efficiency increasing by nearly 2%. The flow analysis show that the outlet flow angle at the tip region of the two blades of the rotor is reduced, thus reducing the OGV attack angle and improving the flow of the blade tip region significantly. The pressure ratio prediction results with the source term addition method are close to those with the entity slot method but have a greater prediction efficiency. The reason is that the entity slot method considers the additional loss caused by slot structure.
The boundary layer separation frequently happens to compressor blades under the non-design condition. Therefore, through making a slot at the tip region of two blades of a rotor for aspiration, we perform the numerical simulation of the boundary layer suction (BLS) of a double-stage counter-rotational compressor by using the entity slot and adding source terms. Then we make comparative study of the performance characteristics and internal flow field of the compressor before and after aspiration respectively. The study results show that the sucking of low-energy fluid near the rotor tip region can enhance the pressure ratio and efficiency of the compressor under various flow volumes,with its total pressure ratio increasing by about 1.25% and the efficiency increasing by nearly 2%. The flow analysis show that the outlet flow angle at the tip region of the two blades of the rotor is reduced, thus reducing the OGV attack angle and improving the flow of the blade tip region significantly. The pressure ratio prediction results with the source term addition method are close to those with the entity slot method but have a greater prediction efficiency. The reason is that the entity slot method considers the additional loss caused by slot structure.
2012, 31(8): 1306-1310.
Abstract:
The worm drive is last stage reduction gear of one antenna deployment mechanism, and the load beared by the worm gear is the maximum. The reliability of worm gear is critical for the successful deployment of the antenna. In order to improve the reliability of mechanism by controlling the worm assemble errors, this paper studies the contact stress sensitivity to different assemble errors. First, the 3D tooth contact FE model of worm gear is established. Then based on three kinds of errors for worm assembling and according to the center distance deviation, middle plane deviation and axis angle deviation, five work conditions are formed. Finally, the contact stress for each work condition were analyze, results demonstrate that the axis angle deviation will affect contact tress most seriously.
The worm drive is last stage reduction gear of one antenna deployment mechanism, and the load beared by the worm gear is the maximum. The reliability of worm gear is critical for the successful deployment of the antenna. In order to improve the reliability of mechanism by controlling the worm assemble errors, this paper studies the contact stress sensitivity to different assemble errors. First, the 3D tooth contact FE model of worm gear is established. Then based on three kinds of errors for worm assembling and according to the center distance deviation, middle plane deviation and axis angle deviation, five work conditions are formed. Finally, the contact stress for each work condition were analyze, results demonstrate that the axis angle deviation will affect contact tress most seriously.
2012, 31(8): 1311-1314.
Abstract:
Based on the motion relation between the grinding wheel and gear in the process of helical-gear form grinding, the coordinate system was established. The mathematical model of the whole helical-gear form grinding surface which contains tooth fillet, involute helicoids and tip cone transition curve was established. Based on the theory of engagement, the exactitude theoretical profile of the grinding wheel had been obtained by deducing the contact condition equations between the grinding wheel and the tooth face to be ground. The wheel profile exactitude grinding program was developed and the numerical example of the algorithm was also presented.
Based on the motion relation between the grinding wheel and gear in the process of helical-gear form grinding, the coordinate system was established. The mathematical model of the whole helical-gear form grinding surface which contains tooth fillet, involute helicoids and tip cone transition curve was established. Based on the theory of engagement, the exactitude theoretical profile of the grinding wheel had been obtained by deducing the contact condition equations between the grinding wheel and the tooth face to be ground. The wheel profile exactitude grinding program was developed and the numerical example of the algorithm was also presented.
2012, 31(8): 1315-1319.
Abstract:
The vibration signal of the aeroengine is non-stationary and involves multi-frequency components as well as an abundant of noise. The Hilbert-Huang transform was used to decompose the vibration signal into a number of intrinsic mode functions (IMF) which represented the physically meaning of the data. Then, the generalized roughness vectors of the IMF were obtained. Because the energy of the IMF represents the validity of this component in the whole signal, the percentage of energy is used as the weight of the generalized roughness feature. Finally, the energy weighted generalized roughness feature was obtained. The experiments on the aeroengine test data of the rubimpact and the normal conditions demonstrated that these statistic characteristics were distinguished for different conditions.
The vibration signal of the aeroengine is non-stationary and involves multi-frequency components as well as an abundant of noise. The Hilbert-Huang transform was used to decompose the vibration signal into a number of intrinsic mode functions (IMF) which represented the physically meaning of the data. Then, the generalized roughness vectors of the IMF were obtained. Because the energy of the IMF represents the validity of this component in the whole signal, the percentage of energy is used as the weight of the generalized roughness feature. Finally, the energy weighted generalized roughness feature was obtained. The experiments on the aeroengine test data of the rubimpact and the normal conditions demonstrated that these statistic characteristics were distinguished for different conditions.
2012, 31(8): 1320-1324.
Abstract:
Considering the effect of contact line on grinding unbalanced force, grinding efficiency and lead modification, the contact line between grinding wheel and tooth face was drawn based on the principle of form grinding. By analyzing the nature of contact line, the impact of wheel inclination angle changing for contact line was obtained. At the same time, the inclination angle has been optimized by weighted sum-squared method, and the designed simulation program can be used to optimize adjustment of contact line. Compared with the traditional empiri-cal method to determine the inclination angle, the optimized inclination angle were more accurate and reliable.
Considering the effect of contact line on grinding unbalanced force, grinding efficiency and lead modification, the contact line between grinding wheel and tooth face was drawn based on the principle of form grinding. By analyzing the nature of contact line, the impact of wheel inclination angle changing for contact line was obtained. At the same time, the inclination angle has been optimized by weighted sum-squared method, and the designed simulation program can be used to optimize adjustment of contact line. Compared with the traditional empiri-cal method to determine the inclination angle, the optimized inclination angle were more accurate and reliable.
2012, 31(8): 1325-1328.
Abstract:
Based on the structural characteristics of tractors, a system for measuring the moment of inertia of tractors was constructed. We also established a simplified mathematic model and designed a specialized half-framework for measuring the moment of inertia of tractor. Using the Pro/E software, the moment of inertia of the half-framework for measurement was obtained accurately. When the half-framework was fixed to the tractor, the moment of inertia of both pitch and roll can all be measured, and the measurement precision was improved. This method was validated in the measurement of moment of inertia for CF650 tractor made in Jiangsu Changfa Group, and the relative error of the moment of inertia was less than 3.10%. The results showed that this method had high precision and the system for measuring the moment of inertia of tractor established in this paper can meet the requirement of accuracy in engineering.
Based on the structural characteristics of tractors, a system for measuring the moment of inertia of tractors was constructed. We also established a simplified mathematic model and designed a specialized half-framework for measuring the moment of inertia of tractor. Using the Pro/E software, the moment of inertia of the half-framework for measurement was obtained accurately. When the half-framework was fixed to the tractor, the moment of inertia of both pitch and roll can all be measured, and the measurement precision was improved. This method was validated in the measurement of moment of inertia for CF650 tractor made in Jiangsu Changfa Group, and the relative error of the moment of inertia was less than 3.10%. The results showed that this method had high precision and the system for measuring the moment of inertia of tractor established in this paper can meet the requirement of accuracy in engineering.
2012, 31(8): 1329-1333.
Abstract:
We use the D-H role to solve each axis motion variable and then discuss how to solve the C-axis motion variable. After this we calculate, analyze and evaluate the machining errors of each axis of the CNC grinding system, which are caused by follow-axis motions. The major work we have done is that we determine a follow-axis and joint-axis cooperated motion scheme. Then we process the machining errors of the six-axis and four-link CNC abra-sive belt grinding system. Finally we use the indirect method to compare the degrees of changes in the efficiency before and after the error-processing. The study results show that the use of the six-axis an processing d four-link CNC abrasive belt grinding system rather than the six-axis CNC abrasive belt grinding system for grinding a curved surface is feasible within the range in which its processing efficiency is allowed.
We use the D-H role to solve each axis motion variable and then discuss how to solve the C-axis motion variable. After this we calculate, analyze and evaluate the machining errors of each axis of the CNC grinding system, which are caused by follow-axis motions. The major work we have done is that we determine a follow-axis and joint-axis cooperated motion scheme. Then we process the machining errors of the six-axis and four-link CNC abra-sive belt grinding system. Finally we use the indirect method to compare the degrees of changes in the efficiency before and after the error-processing. The study results show that the use of the six-axis an processing d four-link CNC abrasive belt grinding system rather than the six-axis CNC abrasive belt grinding system for grinding a curved surface is feasible within the range in which its processing efficiency is allowed.
2012, 31(8): 1334-1340.
Abstract:
The instability and non-equilibrium in the production system of aviation manufacturing enterprise increased the complexity of production schedule, multi-level mixed programming and agent were used to build production scheduling system for aviation manufacturing enterprise. The virtual dynamic management cell and the shop architecture constructed with it were given, some factors like time were transformed to cost factors, the production scheduling model using multi-level mixed programming was built, the processes of task assigned in production scheduling were introduced and some scheduling rules used in the processes were given. Entities of production scheduling were mapped to agents, scheduling system were built with JADE Java Agent Development Framework. The system was used in the shop of an aviation manufacturing enterprise and the scopes of some important parameters were given, the effectiveness of the system was validated.
The instability and non-equilibrium in the production system of aviation manufacturing enterprise increased the complexity of production schedule, multi-level mixed programming and agent were used to build production scheduling system for aviation manufacturing enterprise. The virtual dynamic management cell and the shop architecture constructed with it were given, some factors like time were transformed to cost factors, the production scheduling model using multi-level mixed programming was built, the processes of task assigned in production scheduling were introduced and some scheduling rules used in the processes were given. Entities of production scheduling were mapped to agents, scheduling system were built with JADE Java Agent Development Framework. The system was used in the shop of an aviation manufacturing enterprise and the scopes of some important parameters were given, the effectiveness of the system was validated.
2012, 31(8): 1341-1343.
Abstract:
A parameter called the change rate of the mode axial displacement difference is proposed based on the feature of vibration mode, and is used to judg crack of roller. Displacement mode of roller is calculated by establishing the three-dimensional finite element models of roller with no crack, external crack and inner crack, respectively. The influence of the position and depth of crack on the change rate of the axial displacement difference in the first mode of roller with external and inner crack is also analyzed by extracting the axial displacement in the first mode of a generatrix on the surface of the roller. The results demonstrate that the change rate of the axial displacement difference in the first mode exist a peak at the crack position. And the peak goes higher when the crack is deeper. Therefore, it is feasible to identify the roller's crack damage by the change rate of the axial displacement difference in the first mode.
A parameter called the change rate of the mode axial displacement difference is proposed based on the feature of vibration mode, and is used to judg crack of roller. Displacement mode of roller is calculated by establishing the three-dimensional finite element models of roller with no crack, external crack and inner crack, respectively. The influence of the position and depth of crack on the change rate of the axial displacement difference in the first mode of roller with external and inner crack is also analyzed by extracting the axial displacement in the first mode of a generatrix on the surface of the roller. The results demonstrate that the change rate of the axial displacement difference in the first mode exist a peak at the crack position. And the peak goes higher when the crack is deeper. Therefore, it is feasible to identify the roller's crack damage by the change rate of the axial displacement difference in the first mode.
2012, 31(8): 1344-1348.
Abstract:
Its dynamics analysis plays an intermediate part in its design and control, so it is important to understand its unique dynamics and control characteristics. The topology, kinematics and dynamics of a dual-arm space robot are systematically studied, and its dynamic model is established by using the Kane-Huston method and the screw theory was presented in this paper. The numerical example shows that, given the values of motion parameters, the transient motion of all parts of the space robot can be solved by using the dynamics model we established. Simulations results show that the dynamics model established with the Kane-Huston method and the screw theory is true to reality.
Its dynamics analysis plays an intermediate part in its design and control, so it is important to understand its unique dynamics and control characteristics. The topology, kinematics and dynamics of a dual-arm space robot are systematically studied, and its dynamic model is established by using the Kane-Huston method and the screw theory was presented in this paper. The numerical example shows that, given the values of motion parameters, the transient motion of all parts of the space robot can be solved by using the dynamics model we established. Simulations results show that the dynamics model established with the Kane-Huston method and the screw theory is true to reality.
2012, 31(8): 1349-1353,1358.
Abstract:
In order to study the effects of shot peening on the surface integrity and fatigue properties of titanium alloy, we study the surface morphology, surface roughness, surface metallography, surface micro-hardness and surface residual stress of shot peened TC4 titanium alloy by using a scanning electron microscopy ( SEM), surface profile gauge, metallography microscopy, micro-hardness instrument and X-ray diffraction residual stress analyzer, etc. The fatigue resistance of titanium alloy is investigated by using microcomputer-controlled and high-frequency fatigue testing machine. The relationship between surface integrity and fatigue resistance is discussed. The investi-gation results show that the tension-tension fatigue resistance of TC4 titanium alloy can he greatly improved by reasonable shot peening. The fatigue limit improves by about 14.5% with the shot peening, including 0.10 mmA 0.15 mmA intensity and 100% coverage. However, the fatigue resistance of TC4 titanium alloy can not be significantly improved with the higher shot peening intensity of 0.15 mmA-0.20 mmA. The effect of shot peening on the fatigue property of TC4 titanium alloy is due to the effect of shot peening on its surface integrity. The fatigue resistance of TC4 titanium alloy improves significantly when the surface residual compressive stress and structural strengthening factors induced by shot peening are dominant.
In order to study the effects of shot peening on the surface integrity and fatigue properties of titanium alloy, we study the surface morphology, surface roughness, surface metallography, surface micro-hardness and surface residual stress of shot peened TC4 titanium alloy by using a scanning electron microscopy ( SEM), surface profile gauge, metallography microscopy, micro-hardness instrument and X-ray diffraction residual stress analyzer, etc. The fatigue resistance of titanium alloy is investigated by using microcomputer-controlled and high-frequency fatigue testing machine. The relationship between surface integrity and fatigue resistance is discussed. The investi-gation results show that the tension-tension fatigue resistance of TC4 titanium alloy can he greatly improved by reasonable shot peening. The fatigue limit improves by about 14.5% with the shot peening, including 0.10 mmA 0.15 mmA intensity and 100% coverage. However, the fatigue resistance of TC4 titanium alloy can not be significantly improved with the higher shot peening intensity of 0.15 mmA-0.20 mmA. The effect of shot peening on the fatigue property of TC4 titanium alloy is due to the effect of shot peening on its surface integrity. The fatigue resistance of TC4 titanium alloy improves significantly when the surface residual compressive stress and structural strengthening factors induced by shot peening are dominant.
2012, 31(8): 1354-1358.
Abstract:
The object recognition based on the invariants is the most active research area in the computer vision. The conventional studies about invariants are that these invariants are derived for planar objects using points and lines from images. Nowadays, more and more interest comes from 3 D reconstruction based on the invariants of conics. The projective invariants of a pair of coplanar conics are studied from the perspective of computational proces-ses and the geometrically interpreted is proposed in this paper. The projective invariants of a pair of eoplanar conics are first defined from invariants of a pair of quadratic forms. Then the invariants are geometrically interpreted by using the common self-polar triangle of the two conics, and the algorithm is proposed in this paper. The result of example shows that this formula in this paper is correct on the basis of present studies.
The object recognition based on the invariants is the most active research area in the computer vision. The conventional studies about invariants are that these invariants are derived for planar objects using points and lines from images. Nowadays, more and more interest comes from 3 D reconstruction based on the invariants of conics. The projective invariants of a pair of coplanar conics are studied from the perspective of computational proces-ses and the geometrically interpreted is proposed in this paper. The projective invariants of a pair of eoplanar conics are first defined from invariants of a pair of quadratic forms. Then the invariants are geometrically interpreted by using the common self-polar triangle of the two conics, and the algorithm is proposed in this paper. The result of example shows that this formula in this paper is correct on the basis of present studies.
2012, 31(8): 1359-1362,1368.
Abstract:
Based on the traditional method of Weibull reliability analysis, a new Weibull reliability analysis method based on the support vector machine (SVM) is proposed in this paper. The Weibull probability paper is programmed, by which the parameters of Weibull distribution and reliability life analysis are estimated. And the effectiveness of new Weibull reliability analysis based on SVM and the traditional one are compared. The simulation experiment results show that the new method based on SVM can improve the analysis precision and effectiveness. So the reliability analysis based on SVM can be regarded as another choice of Weibull reliability analysis, which is especially suitable for the small samples.
Based on the traditional method of Weibull reliability analysis, a new Weibull reliability analysis method based on the support vector machine (SVM) is proposed in this paper. The Weibull probability paper is programmed, by which the parameters of Weibull distribution and reliability life analysis are estimated. And the effectiveness of new Weibull reliability analysis based on SVM and the traditional one are compared. The simulation experiment results show that the new method based on SVM can improve the analysis precision and effectiveness. So the reliability analysis based on SVM can be regarded as another choice of Weibull reliability analysis, which is especially suitable for the small samples.
2012, 31(8): 1363-1368.
Abstract:
The dynamic model of cam mechanisms is established according to finite-element method. Kinematic analyses of this dynamic model are obtained. Furthermore, the dynamic equations of cam mechanisms with flexible members are established in modal-coordinates based on Kane's equations. With the dynamic equations and the transformation between modal coordinates and physical coordinates, the dynamic simulation for L-shaped swing rod in a cam loom is finished. Calculated displacement, velocity and acceleration response curves of the end of the swing rod show that the finite-element method is an effective procedure for the dynamic analysis of high-speed cam mechanisms, especially for the high-speed cam mechanisms with non-straight bar and complex shape followers.
The dynamic model of cam mechanisms is established according to finite-element method. Kinematic analyses of this dynamic model are obtained. Furthermore, the dynamic equations of cam mechanisms with flexible members are established in modal-coordinates based on Kane's equations. With the dynamic equations and the transformation between modal coordinates and physical coordinates, the dynamic simulation for L-shaped swing rod in a cam loom is finished. Calculated displacement, velocity and acceleration response curves of the end of the swing rod show that the finite-element method is an effective procedure for the dynamic analysis of high-speed cam mechanisms, especially for the high-speed cam mechanisms with non-straight bar and complex shape followers.
2012, 31(8): 1369-1372,1376.
Abstract:
The vibration control strategy is presented in this paper for a one-link flexible robot arm using trajectory planning. Considering the linearized first-order vibration motion equation, zero initial states and zero residual vibration, the piecewise designed flexural motion of the flexible link endpoint is calculated at first. Then, the acceleration-constant speed-deceleration rigid joint angle trajectory of the link is obtained with constraint conditions. Finally, the input torque of the flexible manipulator for tracking presented designed joint trajectory is achieved applying the PD controller. The numerical simulations are carried out to demonstrate the control performances and effectiveness of the proposed method.
The vibration control strategy is presented in this paper for a one-link flexible robot arm using trajectory planning. Considering the linearized first-order vibration motion equation, zero initial states and zero residual vibration, the piecewise designed flexural motion of the flexible link endpoint is calculated at first. Then, the acceleration-constant speed-deceleration rigid joint angle trajectory of the link is obtained with constraint conditions. Finally, the input torque of the flexible manipulator for tracking presented designed joint trajectory is achieved applying the PD controller. The numerical simulations are carried out to demonstrate the control performances and effectiveness of the proposed method.
2012, 31(8): 1373-1376.
Abstract:
To improve the manufacturing economy and design rationality of the blowout prevention valve of a largescale single ram, we optimize its structural topology. First, we propose the requirements for the topological optimization through analyzing its working principles and characteristics. Second, we establish the flow chart and objective function of the topological optimization and perform the objective function sensitivity analysis. Finally we optimize the structural topology of an actual blowout prevention valve, and the real example shows that our method is effective. The topological optimization results show that the optimized blowout prevention valve can save 16.8% of the material needed for manufacturing and enhance its mechanics characteristics.
To improve the manufacturing economy and design rationality of the blowout prevention valve of a largescale single ram, we optimize its structural topology. First, we propose the requirements for the topological optimization through analyzing its working principles and characteristics. Second, we establish the flow chart and objective function of the topological optimization and perform the objective function sensitivity analysis. Finally we optimize the structural topology of an actual blowout prevention valve, and the real example shows that our method is effective. The topological optimization results show that the optimized blowout prevention valve can save 16.8% of the material needed for manufacturing and enhance its mechanics characteristics.
