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RSS2012 Vol. 31, No. 5
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2012, 31(5): 689-693.
PDF 608KB
Abstract:
On basis of the elastic mechanics and considering the influence of the width,depth of the local defect and load zone,and keeping the inner race stationary,the dynamic model of rolling element bearing with an inner race defect was constructed according to the change of the contact force between the rolling element and races caused by the variation of the contact deflection which took place when the rolling element passed the defect.Through the numerical simulation,it was verified that the frequency components of the vibration signal of the rolling element bearing with an inner race defect in low frequency region were the rotary frequency of the inner race,the frequency of the rolling element passing the defect and its multiple frequencies and side bands beside them caused by the rotary frequency of the inner race,which often was used in fault diagnosis of the rolling element bearing.The reason of occurrence of the multiple frequencies was explained reasonably.Compared the experimental result and numerical simulated result,it was showed the model can explained the vibration characteristics of rolling element bearing with an inner race default effectively.
On basis of the elastic mechanics and considering the influence of the width,depth of the local defect and load zone,and keeping the inner race stationary,the dynamic model of rolling element bearing with an inner race defect was constructed according to the change of the contact force between the rolling element and races caused by the variation of the contact deflection which took place when the rolling element passed the defect.Through the numerical simulation,it was verified that the frequency components of the vibration signal of the rolling element bearing with an inner race defect in low frequency region were the rotary frequency of the inner race,the frequency of the rolling element passing the defect and its multiple frequencies and side bands beside them caused by the rotary frequency of the inner race,which often was used in fault diagnosis of the rolling element bearing.The reason of occurrence of the multiple frequencies was explained reasonably.Compared the experimental result and numerical simulated result,it was showed the model can explained the vibration characteristics of rolling element bearing with an inner race default effectively.
2012, 31(5): 694-697.
Abstract:
In order to overcome the shortages of prematurity and worse convergency for conventional genetic algorithm,a new strategy for improving efficiency of the conventional genetic algorithm has been put forward.In the present method,the selection probability and the mutation probability are self-adaptive.Taking the stability of laminate composite as the goal,the optimized laminate sequency is analyzed with the help of using the benchwork of ABAQUS,and the new GA program,the parametric modeling program and the eigenvalue searching program are coded with Python language.Comparing with the conventional genetic algorithm,the new GA method shows a good consistency,fast convergency and practical feasibility.
In order to overcome the shortages of prematurity and worse convergency for conventional genetic algorithm,a new strategy for improving efficiency of the conventional genetic algorithm has been put forward.In the present method,the selection probability and the mutation probability are self-adaptive.Taking the stability of laminate composite as the goal,the optimized laminate sequency is analyzed with the help of using the benchwork of ABAQUS,and the new GA program,the parametric modeling program and the eigenvalue searching program are coded with Python language.Comparing with the conventional genetic algorithm,the new GA method shows a good consistency,fast convergency and practical feasibility.
2012, 31(5): 698-702.
Abstract:
In order to offer a theoretical basis for the selection of adaptive threshold for the asperity surfaces of different roughness and different correlation length,a series of 2D rough surface are generated with random function and Fourier Transform.The relationship between characteristic parameters of surface topography,such as root mean square slope and curvature of asperity peaks varying with correlation length,is studied.The parameter δ-,which is the ratio of adaptive threshold to root mean square curvature of asperity peaks,is firstly presented,and then the correlation that the number of adaptive nodes are dependent on parameter δ-is also investigated.Substantive numerical simulation of elastic-plastic contact between various adaptive rough surfaces and a rigid plane are carried out,and then results demonstrate that the precision of calcualtions can be guaranteed if δ--6 mm2.
In order to offer a theoretical basis for the selection of adaptive threshold for the asperity surfaces of different roughness and different correlation length,a series of 2D rough surface are generated with random function and Fourier Transform.The relationship between characteristic parameters of surface topography,such as root mean square slope and curvature of asperity peaks varying with correlation length,is studied.The parameter δ-,which is the ratio of adaptive threshold to root mean square curvature of asperity peaks,is firstly presented,and then the correlation that the number of adaptive nodes are dependent on parameter δ-is also investigated.Substantive numerical simulation of elastic-plastic contact between various adaptive rough surfaces and a rigid plane are carried out,and then results demonstrate that the precision of calcualtions can be guaranteed if δ--6 mm2.
2012, 31(5): 703-707.
Abstract:
In order to solve the problem of automatic assembly between modules,which is caused by module division durning rapid design,a way of automatic assembly based on SolidWorks is researched.The assembly sequence planning is generated by using of Assembly Oriented Graph(AOG) and Datum Flow Chain(DFC) representation,together with the second development function of SolidWorks,model space transforming technique and assembly based on features method were applied to realize automatic assembly between modules of the components.After the designer modifies parameters of components,the system can automatically drive dimensions of components and assembly them.At last,the program language VB.Net is used as the development platform,and developing a rapid design system for sandhopper.Therefore,this method is verified for the practical project effectively.
In order to solve the problem of automatic assembly between modules,which is caused by module division durning rapid design,a way of automatic assembly based on SolidWorks is researched.The assembly sequence planning is generated by using of Assembly Oriented Graph(AOG) and Datum Flow Chain(DFC) representation,together with the second development function of SolidWorks,model space transforming technique and assembly based on features method were applied to realize automatic assembly between modules of the components.After the designer modifies parameters of components,the system can automatically drive dimensions of components and assembly them.At last,the program language VB.Net is used as the development platform,and developing a rapid design system for sandhopper.Therefore,this method is verified for the practical project effectively.
2012, 31(5): 708-712.
Abstract:
Because of special rationalized performances of Zircaloy grinding,using conventional grinding technology will bring about the grinding hot and the workpiece to surface burning,but the abrasive belt has mush characteristics,for example,the grinding temperature is much low and the workpiece of surface is not easy to be burned,so it is called as"cold grinding".This article adopts three different abrasive belts doing experimental process about zirconium tube,observing the workpiece of the standard of material removal rate,the surface roughness and the surface of the worn belt after grinding,and finding out which is most suitable for the abrasive belt grinding of Zircaloy tube.The professional graphic processing software Image-Pro Plus is used to process and calculate the pictures that are collected by the camera for analyzing the situation of belt plug.Also,the influence of belt speed on the standard material removal rate is investigated,when the belt speed is 12 m/s with the experiment,the material removing efficiency achieves maximum value,and the belt wear is more reasonable.
Because of special rationalized performances of Zircaloy grinding,using conventional grinding technology will bring about the grinding hot and the workpiece to surface burning,but the abrasive belt has mush characteristics,for example,the grinding temperature is much low and the workpiece of surface is not easy to be burned,so it is called as"cold grinding".This article adopts three different abrasive belts doing experimental process about zirconium tube,observing the workpiece of the standard of material removal rate,the surface roughness and the surface of the worn belt after grinding,and finding out which is most suitable for the abrasive belt grinding of Zircaloy tube.The professional graphic processing software Image-Pro Plus is used to process and calculate the pictures that are collected by the camera for analyzing the situation of belt plug.Also,the influence of belt speed on the standard material removal rate is investigated,when the belt speed is 12 m/s with the experiment,the material removing efficiency achieves maximum value,and the belt wear is more reasonable.
2012, 31(5): 713-717.
Abstract:
In order to investigate the polishing depth with grinding head of polishing machine in perpendicular direction,the structure and principle of polishing machine was analyzed and the principle of polishing tile with grinding grain was analyzed.It is concluded that tiles were polished by grinding head in a spiral track.Grinding block is simplified as the scraper and the mathematical model of polishing depth with grinding head of polishing machine in perpendicular direction is established.The effectiveness of the model is verified by experiments.
In order to investigate the polishing depth with grinding head of polishing machine in perpendicular direction,the structure and principle of polishing machine was analyzed and the principle of polishing tile with grinding grain was analyzed.It is concluded that tiles were polished by grinding head in a spiral track.Grinding block is simplified as the scraper and the mathematical model of polishing depth with grinding head of polishing machine in perpendicular direction is established.The effectiveness of the model is verified by experiments.
2012, 31(5): 718-722.
Abstract:
Based on principle of involutes gearing and methods of determining the elastic deformation of gear teeth,the impact position and velocity are obtained.The impact force expression was established according to theory of mechanical dynamics.The impact force affected by the rotating speed,transmitting load and transmission ratio are analyzed.
Based on principle of involutes gearing and methods of determining the elastic deformation of gear teeth,the impact position and velocity are obtained.The impact force expression was established according to theory of mechanical dynamics.The impact force affected by the rotating speed,transmitting load and transmission ratio are analyzed.
2012, 31(5): 723-725.
Abstract:
In order to obtain the natural frequency of brake discs rapidly and accurately,an online detection system is designed and developed in this paper.The system is composed of sensors,data acquisition hardware,data acquisition and analysis software module,online detection software module and controlled circuit.The design principle and the implementation method of the system are introduced.The application results show that the detection system has good performances and can detect the natural frequency of brake discs rapidly and accurately,and display the judgment results intuitively.
In order to obtain the natural frequency of brake discs rapidly and accurately,an online detection system is designed and developed in this paper.The system is composed of sensors,data acquisition hardware,data acquisition and analysis software module,online detection software module and controlled circuit.The design principle and the implementation method of the system are introduced.The application results show that the detection system has good performances and can detect the natural frequency of brake discs rapidly and accurately,and display the judgment results intuitively.
Analysis of Rotating Machine Fault Diagnosis Based on Blind Source Separation and Wavelet De-noising
2012, 31(5): 726-730.
Abstract:
The vibration signals of rotating machinery are separated and diagnosed by combining the wavelet noise reduction and the blind source separation in this paper. Firstly, the combing method uses the better wavelet threshold value de-noising to reduce noise for non-stationary vibration signals, and then separates the useful vibration signals with blind source separation. It shows that the combining method is more effective than the direct blind source separation in signal processing. Applying the combining method to analyze real measured trouble signals of a gas turbine, the fault diagnosis results are found to be in agreement with practice. The result shows that the combing method is efficient in analyzing the fault diagnosis of rotating machinery.
The vibration signals of rotating machinery are separated and diagnosed by combining the wavelet noise reduction and the blind source separation in this paper. Firstly, the combing method uses the better wavelet threshold value de-noising to reduce noise for non-stationary vibration signals, and then separates the useful vibration signals with blind source separation. It shows that the combining method is more effective than the direct blind source separation in signal processing. Applying the combining method to analyze real measured trouble signals of a gas turbine, the fault diagnosis results are found to be in agreement with practice. The result shows that the combing method is efficient in analyzing the fault diagnosis of rotating machinery.
2012, 31(5): 731-734.
Abstract:
Using auto parts and standard material specimens, the strengthening characteristics of low amplitude loading was investigated. The results showed that the strengthening characteristics of low amplitude loading were greatly affected by the test specimens. For auto parts, there were obvious regions of strengthening cycles and strengthening loads, their strengthening conditions were easy to satisfy. Whereas the strengthening conditions of standard material specimens were strict, the strengthening loading should be matched with strengthening cycle which was higher than that of standard material specimen. The reasons of different strengthening conditions for these two types of specimens were primarily analyzed.
Using auto parts and standard material specimens, the strengthening characteristics of low amplitude loading was investigated. The results showed that the strengthening characteristics of low amplitude loading were greatly affected by the test specimens. For auto parts, there were obvious regions of strengthening cycles and strengthening loads, their strengthening conditions were easy to satisfy. Whereas the strengthening conditions of standard material specimens were strict, the strengthening loading should be matched with strengthening cycle which was higher than that of standard material specimen. The reasons of different strengthening conditions for these two types of specimens were primarily analyzed.
2012, 31(5): 735-739.
Abstract:
Aim at the strong non-linear,non-Gauss and non-stationary vibration signal of rotating machinery,a short rapid time-frequency process analysis method is proposed based on the wavelet transform and the traditional time-frequency analysis.In the method,the wavelet transform is used to achieve the signal decomposition of the variable scale time-frequency atom(wavelet functions),and FFT is used to perform time-frequency analysis.With this method,the bearing shaft vibration response incorporated with shock signal is analyzed,and the vibration characteristics in the time domain and frequency domain are obtained.The results show that the method can extract the non-stationary signal characteristics(frequency and magnitude) quickly and accurately,and its accuracy is higher than that of FFT and STFT.
Aim at the strong non-linear,non-Gauss and non-stationary vibration signal of rotating machinery,a short rapid time-frequency process analysis method is proposed based on the wavelet transform and the traditional time-frequency analysis.In the method,the wavelet transform is used to achieve the signal decomposition of the variable scale time-frequency atom(wavelet functions),and FFT is used to perform time-frequency analysis.With this method,the bearing shaft vibration response incorporated with shock signal is analyzed,and the vibration characteristics in the time domain and frequency domain are obtained.The results show that the method can extract the non-stationary signal characteristics(frequency and magnitude) quickly and accurately,and its accuracy is higher than that of FFT and STFT.
2012, 31(5): 740-743.
Abstract:
The color characterization of a device refers to the transformation between its related color space and its standard color space.It is one of the key technologies of color management.Taking the transformation between RGB color space and CIE L＊a＊b＊ color space as an example,we adopt the cerebellar model articulation controller(CMAC) identification theory to characterize the color space of a device,and then compare our color space characterization method with the BP neural network method and the fuzzy neural network identification method.We simulate the color space characterization with Matlab.The simulation results show that our new method can meet the output precision requirement by less than 100 times of iteration when the number of training samples is 729,and that the average color error of a testing sample is 1.35,indicating that the transformation speed and accuracy of our new method is superior.
The color characterization of a device refers to the transformation between its related color space and its standard color space.It is one of the key technologies of color management.Taking the transformation between RGB color space and CIE L＊a＊b＊ color space as an example,we adopt the cerebellar model articulation controller(CMAC) identification theory to characterize the color space of a device,and then compare our color space characterization method with the BP neural network method and the fuzzy neural network identification method.We simulate the color space characterization with Matlab.The simulation results show that our new method can meet the output precision requirement by less than 100 times of iteration when the number of training samples is 729,and that the average color error of a testing sample is 1.35,indicating that the transformation speed and accuracy of our new method is superior.
2012, 31(5): 744-748.
Abstract:
A radar is a typical electronic equipment that plays an important role in the measurement and control of spaceflight missions.Based on the discussion about the number of its spare parts,the paper analyzes the basic principles of dividing its subsystems,whose failure probability was modeled.Assuming that the time for replacing the spare parts is neglected,the paper puts forward the integral expressions of the failure probability by using the poisson process.Accordingly,the paper proposes the method for calculating the mean availability and the mean working time,thus analyzing the spare parts of the radar's subsystems.This method is useful for analyzing and calculating the availability and mission reliability of the radar at the launching site and the purchase of its spare parts.
A radar is a typical electronic equipment that plays an important role in the measurement and control of spaceflight missions.Based on the discussion about the number of its spare parts,the paper analyzes the basic principles of dividing its subsystems,whose failure probability was modeled.Assuming that the time for replacing the spare parts is neglected,the paper puts forward the integral expressions of the failure probability by using the poisson process.Accordingly,the paper proposes the method for calculating the mean availability and the mean working time,thus analyzing the spare parts of the radar's subsystems.This method is useful for analyzing and calculating the availability and mission reliability of the radar at the launching site and the purchase of its spare parts.
2012, 31(5): 749-752.
Abstract:
Widely used in aerospace and other high-tech areas,hydraulic servo systems require that their output should quickly track the input instructions without overshoot and that their control accuracy be good.To address the strong nonlinearity and repetitive motion of a hydraulic servo system,this paper takes advantage of repetitive control compensation and CMAC(Cerebellar Model Articulation Controller) to construct a compound PID controller by combining repetitive control compensation and CMAC with PID,which is used to carry out the position control of the hydraulic servo system.The simulation results show that compared with both the CMAC and the CMAC and PID parallel controller,our compound PID controller can enhance the response speed of the hydraulic servo system and the accuracy for tracking its periodical signals,thus enhancing its interference suppression capability.
Widely used in aerospace and other high-tech areas,hydraulic servo systems require that their output should quickly track the input instructions without overshoot and that their control accuracy be good.To address the strong nonlinearity and repetitive motion of a hydraulic servo system,this paper takes advantage of repetitive control compensation and CMAC(Cerebellar Model Articulation Controller) to construct a compound PID controller by combining repetitive control compensation and CMAC with PID,which is used to carry out the position control of the hydraulic servo system.The simulation results show that compared with both the CMAC and the CMAC and PID parallel controller,our compound PID controller can enhance the response speed of the hydraulic servo system and the accuracy for tracking its periodical signals,thus enhancing its interference suppression capability.
2012, 31(5): 753-759.
Abstract:
To solve the problems of overwhelming assumptions used in equipment state estimation,this paper proposes a novel kind of characteristic variable identification and selection method based on Mahalanobis-Taguchi system(MTS).First,the Mahalanobis distance(MD) is applied to describe the space distance,and the standard space is established based on the normal samples.Then,the MD of exceptional samples are calculated and compared with the normal samples to verify the correctness of the standard space.The orthogonal array and the signal to noise ratio are introduced for characteristic variable selection.An experimental platform is constructed based on the Rolling-element bearing of a spindle headstock of the micro computer numerical control(CNC) milling machine.The experimental results demonstrate that the prominent characteristic variables for Rolling-element bearing state can be effectively identified based on MTS.
To solve the problems of overwhelming assumptions used in equipment state estimation,this paper proposes a novel kind of characteristic variable identification and selection method based on Mahalanobis-Taguchi system(MTS).First,the Mahalanobis distance(MD) is applied to describe the space distance,and the standard space is established based on the normal samples.Then,the MD of exceptional samples are calculated and compared with the normal samples to verify the correctness of the standard space.The orthogonal array and the signal to noise ratio are introduced for characteristic variable selection.An experimental platform is constructed based on the Rolling-element bearing of a spindle headstock of the micro computer numerical control(CNC) milling machine.The experimental results demonstrate that the prominent characteristic variables for Rolling-element bearing state can be effectively identified based on MTS.
2012, 31(5): 760-765.
Abstract:
To eluicdatie the mechanism effect of friction on the nonlinear vibration and stability of gear system,a nonlinear vibration of torsional model with time-varying stiffness and friction was established,numerical method and analytical expression were given to solve the problem,study the non-linear response and parametric stability of gear system with double periodic parametrically.Effects of the system parameters,such as friction coefficient,mesh stiffneee factor and load sharing coefficient,on the nonlinear vibration response and parametric stability of gear system were investigated.Simulation results demonstrated that rational dynamics parameters can efficiently control the response peak of friction and reduce instability domain.
To eluicdatie the mechanism effect of friction on the nonlinear vibration and stability of gear system,a nonlinear vibration of torsional model with time-varying stiffness and friction was established,numerical method and analytical expression were given to solve the problem,study the non-linear response and parametric stability of gear system with double periodic parametrically.Effects of the system parameters,such as friction coefficient,mesh stiffneee factor and load sharing coefficient,on the nonlinear vibration response and parametric stability of gear system were investigated.Simulation results demonstrated that rational dynamics parameters can efficiently control the response peak of friction and reduce instability domain.
2012, 31(5): 766-770.
Abstract:
The structural optimal design based on traditional optimization theory and experience estimation exists many weak points,such as the local optimum、strict differentiability demand of objective function and the optimization results sensitive to the initialization values,which are hard to be conquered.An idiographic problem about the length optimization design of five freedoms robotic arm is solved in this paper.The object function about gross power,angular accelerations of each articulation、structural compactness,is found;the length of each articulation is optimized using combining multiple objective genetic algorithms with fuzzy judgment as an intelligent optimization method.Comparing the results between the traditional method and intelligent one,it shows that the intelligent optimization method can meet the requests of economy,stability and structural space.
The structural optimal design based on traditional optimization theory and experience estimation exists many weak points,such as the local optimum、strict differentiability demand of objective function and the optimization results sensitive to the initialization values,which are hard to be conquered.An idiographic problem about the length optimization design of five freedoms robotic arm is solved in this paper.The object function about gross power,angular accelerations of each articulation、structural compactness,is found;the length of each articulation is optimized using combining multiple objective genetic algorithms with fuzzy judgment as an intelligent optimization method.Comparing the results between the traditional method and intelligent one,it shows that the intelligent optimization method can meet the requests of economy,stability and structural space.
2012, 31(5): 771-777.
Abstract:
The wire-cut electrical discharge machining(WEDM) is an important part of precision and special machining.There are many factors of influence on the WEDM precision,which exhibit themselves in the form of the dynamic characteristics of wire electrode.The traditional wire electrode stability control method reduces not only the wire-moving speed but also the machining precision.So the problem lies in understanding the dynamic characteristics of electrode wire.This paper presents a review on the dynamic characteristics of WEDM electrode wire from three perspectives： vibration model,thermal model and stability control.It also points out the existing issues and research trends.
The wire-cut electrical discharge machining(WEDM) is an important part of precision and special machining.There are many factors of influence on the WEDM precision,which exhibit themselves in the form of the dynamic characteristics of wire electrode.The traditional wire electrode stability control method reduces not only the wire-moving speed but also the machining precision.So the problem lies in understanding the dynamic characteristics of electrode wire.This paper presents a review on the dynamic characteristics of WEDM electrode wire from three perspectives： vibration model,thermal model and stability control.It also points out the existing issues and research trends.
2012, 31(5): 778-782.
Abstract:
We study a washout algorithm for addressing the simulation fidelity of the six-DOF motion platform of a civil airliner for training.We use the Pro/E and Mathematica to establish the model and the classical filtering algorithm to simulate a set of actual flight data.The washout algorithm takes the discrete form and optimizes its parameters;this not only suits the simulation reality but also makes the washout algorithm more flexible.The simulation results show that the washout algorithm can improve the simulation fidelity of the six-DOF motion platform.
We study a washout algorithm for addressing the simulation fidelity of the six-DOF motion platform of a civil airliner for training.We use the Pro/E and Mathematica to establish the model and the classical filtering algorithm to simulate a set of actual flight data.The washout algorithm takes the discrete form and optimizes its parameters;this not only suits the simulation reality but also makes the washout algorithm more flexible.The simulation results show that the washout algorithm can improve the simulation fidelity of the six-DOF motion platform.
2012, 31(5): 783-786.
Abstract:
With back cutting depth,spindle speed,feeding and cutting width as design variables,and cutting force as response,a second-order mathematical model of cutting force is built using the response surface method of statistics.The hardware test system of cutting experiment for 45 steel is built.The response surface method is incorporated in LabVIEW 8.6 programming to design the software system.By inputting the number of impact factor and the factor value scope,the software system can automatically generate a center combination experimental design scheme and it can collect,calculate and analyze the experimental data,and,finally build the response surface model.
With back cutting depth,spindle speed,feeding and cutting width as design variables,and cutting force as response,a second-order mathematical model of cutting force is built using the response surface method of statistics.The hardware test system of cutting experiment for 45 steel is built.The response surface method is incorporated in LabVIEW 8.6 programming to design the software system.By inputting the number of impact factor and the factor value scope,the software system can automatically generate a center combination experimental design scheme and it can collect,calculate and analyze the experimental data,and,finally build the response surface model.
2012, 31(5): 787-790.
Abstract:
To analyze the two conditions that the front or rear brake has or does not have its load sensing proportional valves,the match between its braking force distribution curve and the I curve and the impact of the load sensing proportional valve on an automobile's braking performance,we introduce the concept of braking force utilization rate,which we believe can reflect its braking performance,and work out different braking force utilization rate algorithms for different matches.Then we analyze the relationship between braking utilization rate and road adhesion coefficient.We compare the changes in the braking utilization rate under the two conditions;the comparison results show that the load sensing proportional valve can greatly increase the braking utilization rate of an automobile when it travels on the road that has a high adhesion coefficient.
To analyze the two conditions that the front or rear brake has or does not have its load sensing proportional valves,the match between its braking force distribution curve and the I curve and the impact of the load sensing proportional valve on an automobile's braking performance,we introduce the concept of braking force utilization rate,which we believe can reflect its braking performance,and work out different braking force utilization rate algorithms for different matches.Then we analyze the relationship between braking utilization rate and road adhesion coefficient.We compare the changes in the braking utilization rate under the two conditions;the comparison results show that the load sensing proportional valve can greatly increase the braking utilization rate of an automobile when it travels on the road that has a high adhesion coefficient.
2012, 31(5): 791-795.
Abstract:
To overcome the shortcomings of line interpolation and circular interpolation,we utilize the NURBS interpolation function of the FANUC system to carry out the machining of NURBS curve.In order to ensure the high-speed and high-accuracy machining of the NURBS curve,we combine the control function of the HRV2 servo system with the real-time look-ahead control function of CNC and improve the machining performance of the CNC by adjusting the look-ahead feedforward coefficient and the velocity gain parameters.The actual tool movement trajectories show that our new scheme can improve the response and rigidity of the servo system,reduce the machining errors of the CNC and increase its location velocity.
To overcome the shortcomings of line interpolation and circular interpolation,we utilize the NURBS interpolation function of the FANUC system to carry out the machining of NURBS curve.In order to ensure the high-speed and high-accuracy machining of the NURBS curve,we combine the control function of the HRV2 servo system with the real-time look-ahead control function of CNC and improve the machining performance of the CNC by adjusting the look-ahead feedforward coefficient and the velocity gain parameters.The actual tool movement trajectories show that our new scheme can improve the response and rigidity of the servo system,reduce the machining errors of the CNC and increase its location velocity.
2012, 31(5): 796-800.
Abstract:
In order to make the float-wall structure has better cooling effect,this paper carried out optimization studies about the float-wall's wall temperature.On the base of heat-flow coupling analysis on the float-wall's temperature,a nonlinear mapping function from float-wall's parameters to float-wall's temperature was constructed with BP neural networks(NN).The genetic algorithm(GA) was used to obtain the objective function values in optimal design of structures.Optimal design of float-wall was put forward by using genetic algorithms to obtain the more effective cooling structure;the temperature index was decreased by 4.19%.The results show that the optimization technology applied in optimal design of float-wall's wall temperature is effective and reasonable.
In order to make the float-wall structure has better cooling effect,this paper carried out optimization studies about the float-wall's wall temperature.On the base of heat-flow coupling analysis on the float-wall's temperature,a nonlinear mapping function from float-wall's parameters to float-wall's temperature was constructed with BP neural networks(NN).The genetic algorithm(GA) was used to obtain the objective function values in optimal design of structures.Optimal design of float-wall was put forward by using genetic algorithms to obtain the more effective cooling structure;the temperature index was decreased by 4.19%.The results show that the optimization technology applied in optimal design of float-wall's wall temperature is effective and reasonable.
2012, 31(5): 801-805,809.
Abstract:
We propose a new method for evaluating and predicting the grinding surface roughness of engineering ceramics efficiently,using the grayscale information on their surface images.First,through experiments,we select luminance 140,contrast 42,saturation 24 and acutance 9 as the image-acquisition parameters and then select the mean value and mean square deviation of the grayscale as its parameters for describing the surface roughness.Second,after the acquired images receive the digital image processing of noise reduction,image enhancement and grey enhancement,we extract the grayscale information on every other 6 surface images to establish the model of the relationship between the surface roughness evaluation parameters Ra、Rz、Ry and the mean value of grayscale information.Finally,the analysis of the model shows that the mean value and mean square deviation of the grayscale are proportional to the grinding surface roughness;this conclusion can be used to quickly evaluate the surface roughness of various kinds of ceramics after grinding.
We propose a new method for evaluating and predicting the grinding surface roughness of engineering ceramics efficiently,using the grayscale information on their surface images.First,through experiments,we select luminance 140,contrast 42,saturation 24 and acutance 9 as the image-acquisition parameters and then select the mean value and mean square deviation of the grayscale as its parameters for describing the surface roughness.Second,after the acquired images receive the digital image processing of noise reduction,image enhancement and grey enhancement,we extract the grayscale information on every other 6 surface images to establish the model of the relationship between the surface roughness evaluation parameters Ra、Rz、Ry and the mean value of grayscale information.Finally,the analysis of the model shows that the mean value and mean square deviation of the grayscale are proportional to the grinding surface roughness;this conclusion can be used to quickly evaluate the surface roughness of various kinds of ceramics after grinding.
2012, 31(5): 806-809.
Abstract:
Based on the aerodynamics of wind turbine,structural dynamics of blades and output power performance,the relationship between them was discussed.The multidisciplinary design optimization model of the blades was presented whereas the objective was cost of energy which is calculated from the Annual Energy Production(AEP) and the cost of the whole rotor.Using this model,a 5 MW rotor was optimized and the design variables were the chord,twist angle and relative thickness of blades.The cost of the optimized rotor was reduced by 2.6% comparing with the original rotor.To valide the optimization results,the comparison of the load between the optimized and original blade were calculated and plotted.
Based on the aerodynamics of wind turbine,structural dynamics of blades and output power performance,the relationship between them was discussed.The multidisciplinary design optimization model of the blades was presented whereas the objective was cost of energy which is calculated from the Annual Energy Production(AEP) and the cost of the whole rotor.Using this model,a 5 MW rotor was optimized and the design variables were the chord,twist angle and relative thickness of blades.The cost of the optimized rotor was reduced by 2.6% comparing with the original rotor.To valide the optimization results,the comparison of the load between the optimized and original blade were calculated and plotted.
2012, 31(5): 810-813,817.
Abstract:
Homing is the process that an autonomous underwater vehicle(AUV) returns to its underwater supporting station after mission,and it is the key operation in the AUV's autonomous retrieval.The AUV homing control algorithm based on path following is proposed in this paper.The homing path is planned with the Dubins curve to connect the AUV starting point and the docking point using one straight line and two arcs with radius equal to the AUV minimum turning radius determined by the AUV's maneuvering capability.The tangent vectors of the homing path at the start-point and end-point are along the AUV's initial heading and the docking entrance direction respectively.The nonlinear dynamic model of the path following errors is derived in the Serret-Frenet coordinate originating at the reference point moving on the path,overcoming the singularity problem in the classic methods.The command yaw angle is designed as the control input of the path following errors,which are proved to be globally asymptotically stable while properly choosing the rate of the path curve parameter.The simulation studies demonstrate the effectiveness of the proposed homing path planning and following controller.
Homing is the process that an autonomous underwater vehicle(AUV) returns to its underwater supporting station after mission,and it is the key operation in the AUV's autonomous retrieval.The AUV homing control algorithm based on path following is proposed in this paper.The homing path is planned with the Dubins curve to connect the AUV starting point and the docking point using one straight line and two arcs with radius equal to the AUV minimum turning radius determined by the AUV's maneuvering capability.The tangent vectors of the homing path at the start-point and end-point are along the AUV's initial heading and the docking entrance direction respectively.The nonlinear dynamic model of the path following errors is derived in the Serret-Frenet coordinate originating at the reference point moving on the path,overcoming the singularity problem in the classic methods.The command yaw angle is designed as the control input of the path following errors,which are proved to be globally asymptotically stable while properly choosing the rate of the path curve parameter.The simulation studies demonstrate the effectiveness of the proposed homing path planning and following controller.
2012, 31(5): 814-817.
Abstract:
In this paper,a new method for solving output angles of arbitrarily space four-links mechanism is developed.The simplified model is established considering dimension errors of link length,including angles of links,initial clearances of hinges and different wear loss from reliability standpoint.Then reliability of kinetic accuracy of arbitrarily space four-links mechanism is analyzed.Futhermore,an example of lock mechanism on door system of a certain airplane is given,of which the reliability of kinetic precision is calculated by such method.Finally,a contrast model is built in order to provide reference for analyzing the effects imposed on reliability by different wear loss in engineering calculation.
In this paper,a new method for solving output angles of arbitrarily space four-links mechanism is developed.The simplified model is established considering dimension errors of link length,including angles of links,initial clearances of hinges and different wear loss from reliability standpoint.Then reliability of kinetic accuracy of arbitrarily space four-links mechanism is analyzed.Futhermore,an example of lock mechanism on door system of a certain airplane is given,of which the reliability of kinetic precision is calculated by such method.Finally,a contrast model is built in order to provide reference for analyzing the effects imposed on reliability by different wear loss in engineering calculation.
2012, 31(5): 818-821,826.
Abstract:
A numerical simulation model of single-grain grinding for superalloy GH4169 is presented,and the mapping relationship between single-grain grinding and macroscopic grinding is established based on the statistical analysis of simulation results.At last,a novel method to predict the surface grinding force of superalloy GH4169 is proposed.And the law that the grinding technical parameters,which containes peripheral wheel speed,workpiece speed and the wheel depth of cut,affect the single-grain and macroscopic grinding force is investigated.The theoretically model and computation results are supported by the surface grinding test of superalloy GH4169.
A numerical simulation model of single-grain grinding for superalloy GH4169 is presented,and the mapping relationship between single-grain grinding and macroscopic grinding is established based on the statistical analysis of simulation results.At last,a novel method to predict the surface grinding force of superalloy GH4169 is proposed.And the law that the grinding technical parameters,which containes peripheral wheel speed,workpiece speed and the wheel depth of cut,affect the single-grain and macroscopic grinding force is investigated.The theoretically model and computation results are supported by the surface grinding test of superalloy GH4169.
2012, 31(5): 822-826.
Abstract:
On the construction site,the tower crane working space overlaps mutually,extremely easy to have collision between the tower cranes.In view of this,a monitoring system is developed to measure tower crane positional information real-time using GPS RTK technology.This technology will enhance the measurement accuracy of GPS from the meter level to centimeter level.Measurement results are transformed to the same user-defined coordinate system through the Bursa-Wolf model,and transmitted to controller by wireless LAN technology.Based on the mathematical model of tower crane and the principle of collision detection,the anti-collision detection algorithm is designed.According to the position information of tower crane,the designed controller can achieve real-time monitor the tower crane and provide early-warning by using anti-collision detection algorithm.
On the construction site,the tower crane working space overlaps mutually,extremely easy to have collision between the tower cranes.In view of this,a monitoring system is developed to measure tower crane positional information real-time using GPS RTK technology.This technology will enhance the measurement accuracy of GPS from the meter level to centimeter level.Measurement results are transformed to the same user-defined coordinate system through the Bursa-Wolf model,and transmitted to controller by wireless LAN technology.Based on the mathematical model of tower crane and the principle of collision detection,the anti-collision detection algorithm is designed.According to the position information of tower crane,the designed controller can achieve real-time monitor the tower crane and provide early-warning by using anti-collision detection algorithm.
2012, 31(5): 827-835,841.
Abstract:
In this paper,traditional BEM theory is improved by considering dynamic inflow effect and then the improved BEM theory is applied to estimate wind turbine load at yawing and dynamic pitching.Pitt-Peters method and Generalized Dynamic Wake(GDW) method are also improved and applied in the calculation of wind turbine load.The comparison between calculated load and test results for real NREL wind turbine show that the improved BEM theory,improved Pitt-Peters method and improved GDW method can predict the wind turbine load very well at yawing and dynamic pitching.Furthermore,load calculation for real ZDS-2500 wind turbine also show that,at yawing and dynamic pitching the wind turbine will suffer from very high dynamic load.In order to avoid underestimation of load,load calculation for unsteady flow should be adopted.
In this paper,traditional BEM theory is improved by considering dynamic inflow effect and then the improved BEM theory is applied to estimate wind turbine load at yawing and dynamic pitching.Pitt-Peters method and Generalized Dynamic Wake(GDW) method are also improved and applied in the calculation of wind turbine load.The comparison between calculated load and test results for real NREL wind turbine show that the improved BEM theory,improved Pitt-Peters method and improved GDW method can predict the wind turbine load very well at yawing and dynamic pitching.Furthermore,load calculation for real ZDS-2500 wind turbine also show that,at yawing and dynamic pitching the wind turbine will suffer from very high dynamic load.In order to avoid underestimation of load,load calculation for unsteady flow should be adopted.
2012, 31(5): 836-841.
Abstract:
The profile design of the rollers of rolling bearings is an important method that can reduce the stress concentration at the edge of the roller and improve the fatigue life of bearings.The contact model of profiled tapered roller was established,then based on the equations of the problem for contact between roller and inner ring,the distributions of contact stress and Mises stress field and their variations with normal load were examined.The comparison of the distributions of above stress fields show that,for the logarithmic tapered roller,the stress concentration of contact stress and the Mises stress inside subsurface at the roller ends is improved;and that the roller profile and blend value should be designed in terms of load to avoid edge effect and prolong the fatigue life of tapered rollers.
The profile design of the rollers of rolling bearings is an important method that can reduce the stress concentration at the edge of the roller and improve the fatigue life of bearings.The contact model of profiled tapered roller was established,then based on the equations of the problem for contact between roller and inner ring,the distributions of contact stress and Mises stress field and their variations with normal load were examined.The comparison of the distributions of above stress fields show that,for the logarithmic tapered roller,the stress concentration of contact stress and the Mises stress inside subsurface at the roller ends is improved;and that the roller profile and blend value should be designed in terms of load to avoid edge effect and prolong the fatigue life of tapered rollers.
2012, 31(5): 842-846,850.
Abstract:
The driving system of a serial manipulator usually combines an AC servomotor with a precision decelerator,with the latter being used for increasing the driving torque of the driving system and reducing its rotational speed.The reduction ratio of the driving system plays a very important role in accelerating or decelerating the serial manipulator and manipulating its operation speed.Therefore,we use an improved S-shaped speed curve to plan the trajectory of the end-effecter of the serial manipulator,to ensure its continuous acceleration and to reduce its impact while it is moving in a high speed.We propose a method for optimizing the reduction ratio of the driving system,which takes the operation principles of the AC servomotor as constraint conditions and aims at the minimal operation time for completing the planned trajectory.A SCARA robot with 4 degrees of freedom is taken as example.On the basis of the inverse dynamics modeling and trajectory planning,we optimize the reduction ratio of the driving system with the genetic algorithm.The simulation results show that our optimization method is effective,can make full use of the performance of the AC servomotor and consequently helps to reduce the cost of the driving system of the serial manipulator,thus enhancing its overall performance.
The driving system of a serial manipulator usually combines an AC servomotor with a precision decelerator,with the latter being used for increasing the driving torque of the driving system and reducing its rotational speed.The reduction ratio of the driving system plays a very important role in accelerating or decelerating the serial manipulator and manipulating its operation speed.Therefore,we use an improved S-shaped speed curve to plan the trajectory of the end-effecter of the serial manipulator,to ensure its continuous acceleration and to reduce its impact while it is moving in a high speed.We propose a method for optimizing the reduction ratio of the driving system,which takes the operation principles of the AC servomotor as constraint conditions and aims at the minimal operation time for completing the planned trajectory.A SCARA robot with 4 degrees of freedom is taken as example.On the basis of the inverse dynamics modeling and trajectory planning,we optimize the reduction ratio of the driving system with the genetic algorithm.The simulation results show that our optimization method is effective,can make full use of the performance of the AC servomotor and consequently helps to reduce the cost of the driving system of the serial manipulator,thus enhancing its overall performance.
2012, 31(5): 847-850.
Abstract:
We explain the merits and demerits existing in the kinetic performance of a serial or parallel robot and thus develop a space robot with the hybrid mechanism consisting of slider pair,void pair and planar 4-bar.Then we analyze its workspace and agility with the robotics and simulate them with Matlab7.0,thus obtaining the characteristics of workspace and the laws of agility change.The space robot can accomplish the tasks of welding,machining and assembling in a semi-ellipsoidal workspace.
We explain the merits and demerits existing in the kinetic performance of a serial or parallel robot and thus develop a space robot with the hybrid mechanism consisting of slider pair,void pair and planar 4-bar.Then we analyze its workspace and agility with the robotics and simulate them with Matlab7.0,thus obtaining the characteristics of workspace and the laws of agility change.The space robot can accomplish the tasks of welding,machining and assembling in a semi-ellipsoidal workspace.
2012, 31(5): 851-854,860.
Abstract:
Aiming to coexisting certainty and uncertainty of product attributes in case retrieval for the product family configuration design,a case retrieval method based on Projection Pursuit(PP)is proposed.Firstly,the uncertainty of product attributes is characterized by interval numbers,then real values interpolated randomly within interval numbers are used to replace interval numbers.Therefore,the number of resource cases and target cases is enlarged.On the work mentioned above,Projection Pursuit is used to get the best projection values.By using the projection values,the case retrieval considering uncertainty of product attributes in configuration design for product family can be completed.Case study of chain saw verifies the proposed method is of usefulness and effectiveness.
Aiming to coexisting certainty and uncertainty of product attributes in case retrieval for the product family configuration design,a case retrieval method based on Projection Pursuit(PP)is proposed.Firstly,the uncertainty of product attributes is characterized by interval numbers,then real values interpolated randomly within interval numbers are used to replace interval numbers.Therefore,the number of resource cases and target cases is enlarged.On the work mentioned above,Projection Pursuit is used to get the best projection values.By using the projection values,the case retrieval considering uncertainty of product attributes in configuration design for product family can be completed.Case study of chain saw verifies the proposed method is of usefulness and effectiveness.
2012, 31(5): 855-860.
Abstract:
In the present work,a few problems existing in the stress severity factor(SSF) approach used for the fatigue life analysis of joints were studied and an improvement of the approach was accomplished.Based on the observation of the fatigue damage failures,the point at the edge of the hole which is vertical to the overall loading direction was defined to be the fatigue damage dangerous point.2D and 3D contact finite element analyses of the joints were carried out.Taking into consideration of converting relation between the three-dimension stress concentration and the two-dimension stress concentration,the extrusion stress concentration factor and extrusion distribution factor were gotten,and thus the modified SSF approach was obtained.Two examples of the fatigue life analysis of joints were accomplished using the modified SSF approach and the results demonstrated that this modified SSF approach gives a more accurate prediction for the fatigue life.
In the present work,a few problems existing in the stress severity factor(SSF) approach used for the fatigue life analysis of joints were studied and an improvement of the approach was accomplished.Based on the observation of the fatigue damage failures,the point at the edge of the hole which is vertical to the overall loading direction was defined to be the fatigue damage dangerous point.2D and 3D contact finite element analyses of the joints were carried out.Taking into consideration of converting relation between the three-dimension stress concentration and the two-dimension stress concentration,the extrusion stress concentration factor and extrusion distribution factor were gotten,and thus the modified SSF approach was obtained.Two examples of the fatigue life analysis of joints were accomplished using the modified SSF approach and the results demonstrated that this modified SSF approach gives a more accurate prediction for the fatigue life.
