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RSS2017 Vol. 36, No. 4
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2017, 36(4): 493-497.
doi: 10.13433/j.cnki.1003-8728.2017.0401
PDF 986KB
Abstract:
The effect of improvement of controlling system and optimal design of friction pairs on precision growth of advanced two-axis linkage system is limited in some extent. In this paper, a precise fine-adjustor is introduced to realize the functional compound with the existing two-axis linkage system. The precision in small-range motion can be increased by several times without interference in the reliability and performance of wide-range motion of the existing system. The piezoelectric fine-adjustor is proposed to realize the growth in angular precision of horizontal-axis linkage system. The electromagnetic fluid type fine-adjustor is proposed to realize the growth in displacement precision of vertical-axis linkage system. The operational principles and working effects of these two fine-adjustors are analyzed. Experiments and analysis indicate that the proposed precision growth method can satisfy the anticipated engineering requirements.
The effect of improvement of controlling system and optimal design of friction pairs on precision growth of advanced two-axis linkage system is limited in some extent. In this paper, a precise fine-adjustor is introduced to realize the functional compound with the existing two-axis linkage system. The precision in small-range motion can be increased by several times without interference in the reliability and performance of wide-range motion of the existing system. The piezoelectric fine-adjustor is proposed to realize the growth in angular precision of horizontal-axis linkage system. The electromagnetic fluid type fine-adjustor is proposed to realize the growth in displacement precision of vertical-axis linkage system. The operational principles and working effects of these two fine-adjustors are analyzed. Experiments and analysis indicate that the proposed precision growth method can satisfy the anticipated engineering requirements.
2017, 36(4): 498-503.
doi: 10.13433/j.cnki.1003-8728.2017.0402
Abstract:
By analyzing the bolt jiont subjected to axial alternating load, the equations between slip angle of screw thread of bolt and the variation in load is established. Based on this, considering the load distribution on the thread of stay bolt under eccentric load, the eccentric load factor is introduced and then the theoretical model on the relationship between slip angle of screw thread and axial eccentric alternate load is obtained. The bolt-joint of M16×2 is calculated with the established theoretical model under specific load and compared with that obtained from finite-element method of Izumi under the same conditions, good agreement is obtained. The slip test of bolt connections under axial alternating loads are performed using vibration shaker, the slippage is measured and compared with the calculated results to validate the correctness of the theoretical formulation. The study provideds a theoretical analysis method to study the self-loosening of stay bolt.
By analyzing the bolt jiont subjected to axial alternating load, the equations between slip angle of screw thread of bolt and the variation in load is established. Based on this, considering the load distribution on the thread of stay bolt under eccentric load, the eccentric load factor is introduced and then the theoretical model on the relationship between slip angle of screw thread and axial eccentric alternate load is obtained. The bolt-joint of M16×2 is calculated with the established theoretical model under specific load and compared with that obtained from finite-element method of Izumi under the same conditions, good agreement is obtained. The slip test of bolt connections under axial alternating loads are performed using vibration shaker, the slippage is measured and compared with the calculated results to validate the correctness of the theoretical formulation. The study provideds a theoretical analysis method to study the self-loosening of stay bolt.
2017, 36(4): 504-511.
doi: 10.13433/j.cnki.1003-8728.2017.0403
Abstract:
It is urgently necessary to measure and analyze the dynamic transmission error signals of a high-speed gear. The paper constructs a dynamic transmission error measurement system, from which the error curve is obtained and then the error curve is analyzed with the Hilbert-Huang Transform(HHT). The intrinsic mode functions of different frequency components of the dynamic transmission error signal is adaptively gained. Then we separate the axis frequency spectrum and tooth frequency spectrum and obtain the Hilbert spectrum of the error signal. To verify the feasibility and correctness of the error analysis method based on the HHT, we use the Fast Fourier Transform (FFT) to analyze the same transmission error signal. The analysis results show that the HHT is good at frequency spectrum division and filtering of the dynamic transmission error signal of high-speed gear. Compared with the FFT, it can accurately separate the frequency spectra of the transmission error signal, thus having more accurate analysis.
It is urgently necessary to measure and analyze the dynamic transmission error signals of a high-speed gear. The paper constructs a dynamic transmission error measurement system, from which the error curve is obtained and then the error curve is analyzed with the Hilbert-Huang Transform(HHT). The intrinsic mode functions of different frequency components of the dynamic transmission error signal is adaptively gained. Then we separate the axis frequency spectrum and tooth frequency spectrum and obtain the Hilbert spectrum of the error signal. To verify the feasibility and correctness of the error analysis method based on the HHT, we use the Fast Fourier Transform (FFT) to analyze the same transmission error signal. The analysis results show that the HHT is good at frequency spectrum division and filtering of the dynamic transmission error signal of high-speed gear. Compared with the FFT, it can accurately separate the frequency spectra of the transmission error signal, thus having more accurate analysis.
2017, 36(4): 512-518.
doi: 10.13433/j.cnki.1003-8728.2017.0404
Abstract:
Because of its lower absolute positioning, an industrial robot is unable to meet the needs of high-precision processing, so this paper puts forward an integrated error compensation method. The error model of a tool's central points based on distance accuracy is developed by the modified Denavit-Hartenberg model. Meanwhile, this paper studies the positioning error of the stressful joints 2 and 3, which is caused by the robot's gravity and external load; then it establishes the flexible error model. Finally, a laser tracker is used as the measurement equipment, and the error model is solved by the least squares method. The positioning error of the robot is compensated for by updating the parameters of its controller to improve the positioning accuracy. After the compensation, the mean positioning accuracy of the robot is significantly improved, which previously is 3.548 mm to 0.939 mm.
Because of its lower absolute positioning, an industrial robot is unable to meet the needs of high-precision processing, so this paper puts forward an integrated error compensation method. The error model of a tool's central points based on distance accuracy is developed by the modified Denavit-Hartenberg model. Meanwhile, this paper studies the positioning error of the stressful joints 2 and 3, which is caused by the robot's gravity and external load; then it establishes the flexible error model. Finally, a laser tracker is used as the measurement equipment, and the error model is solved by the least squares method. The positioning error of the robot is compensated for by updating the parameters of its controller to improve the positioning accuracy. After the compensation, the mean positioning accuracy of the robot is significantly improved, which previously is 3.548 mm to 0.939 mm.
2017, 36(4): 519-526.
doi: 10.13433/j.cnki.1003-8728.2017.0405
Abstract:
Because the conventional multi-response optimization methods rarely consider the optimization and the robustness simultaneously and tend to overlook the quality loss of multiple responses, we propose a new method of multi-response robust optimization based on the improved quality loss function to achieve the robustness and optimization of multiple responses by introducing the dual response surface method. With the dual response surface method and the multivariate loss function combined, the new method considers both the mean and variance of multiple responses. Firstly, the regression equation of the mean and standard deviation of multiple responses are fitted and are incorporated into the multivariate quality loss function. Secondly, the subjective and objective weight theory is used to set the weights of quality losses of mean and standard deviations of each response. Finally, the multi-response robust and optimal problem is transformed into the minimization of overall quality loss. The hyperbolic flexure hinge in the cell injection 3-DOF compliant parallel micro motion platform is used to prove the effectiveness of the new method. The analysis results show that the new method can more effectively solve multi-response robust optimization problems.
Because the conventional multi-response optimization methods rarely consider the optimization and the robustness simultaneously and tend to overlook the quality loss of multiple responses, we propose a new method of multi-response robust optimization based on the improved quality loss function to achieve the robustness and optimization of multiple responses by introducing the dual response surface method. With the dual response surface method and the multivariate loss function combined, the new method considers both the mean and variance of multiple responses. Firstly, the regression equation of the mean and standard deviation of multiple responses are fitted and are incorporated into the multivariate quality loss function. Secondly, the subjective and objective weight theory is used to set the weights of quality losses of mean and standard deviations of each response. Finally, the multi-response robust and optimal problem is transformed into the minimization of overall quality loss. The hyperbolic flexure hinge in the cell injection 3-DOF compliant parallel micro motion platform is used to prove the effectiveness of the new method. The analysis results show that the new method can more effectively solve multi-response robust optimization problems.
2017, 36(4): 527-534.
doi: 10.13433/j.cnki.1003-8728.2017.0406
Abstract:
We build the shifting simulation model of a hydro-mechanical continuously variable transmission (HMCVT). The speed drop amplitude, dynamic load coefficient, maximum degree of shock of output shaft and shifting time are regarded as the shifting quality evaluation indices to establish the engine speed, load torque, pressure of main circuit and flow of speed control valves as factors of influence. An L9(34) orthogonal table is used to determine the primary-secondary and optimal-worst levels of influence factors and to predict the optimum scheme. The simulation datas are calculated by using a statistical method in order to verify the reliability of the simulation results, which show that the shifting quality is improved by the lower engine speed, smaller load torque, lower pressure of main circuit, and the larger flow of speed control valves.
We build the shifting simulation model of a hydro-mechanical continuously variable transmission (HMCVT). The speed drop amplitude, dynamic load coefficient, maximum degree of shock of output shaft and shifting time are regarded as the shifting quality evaluation indices to establish the engine speed, load torque, pressure of main circuit and flow of speed control valves as factors of influence. An L9(34) orthogonal table is used to determine the primary-secondary and optimal-worst levels of influence factors and to predict the optimum scheme. The simulation datas are calculated by using a statistical method in order to verify the reliability of the simulation results, which show that the shifting quality is improved by the lower engine speed, smaller load torque, lower pressure of main circuit, and the larger flow of speed control valves.
2017, 36(4): 535-541.
doi: 10.13433/j.cnki.1003-8728.2017.0407
Abstract:
Research on mining combined time domain statistical parameter information from vibration signal is a very meaningful work for machinery detection, fault diagnosis and state prediction service. In this paper, drilling pump's vibration signal is segmented by BOU(Basic operation unit) processing, then time domain parameters of such vibration signal's segmentation has been calculated. These time domain parameters are investigated carefully with using a new framework-statistical distribution of combined time domain parameters. Studies have shown that the distribution of time domain parameter scatters has strong regularity and spatial feature under different working conditions. A good corresponding relationship between the vibration signal, combined parameter distribution characteristics, regional distribution, and equipment malfunction has been established. It can also provide a geat convenience for the fault detection of drilling pump.
Research on mining combined time domain statistical parameter information from vibration signal is a very meaningful work for machinery detection, fault diagnosis and state prediction service. In this paper, drilling pump's vibration signal is segmented by BOU(Basic operation unit) processing, then time domain parameters of such vibration signal's segmentation has been calculated. These time domain parameters are investigated carefully with using a new framework-statistical distribution of combined time domain parameters. Studies have shown that the distribution of time domain parameter scatters has strong regularity and spatial feature under different working conditions. A good corresponding relationship between the vibration signal, combined parameter distribution characteristics, regional distribution, and equipment malfunction has been established. It can also provide a geat convenience for the fault detection of drilling pump.
2017, 36(4): 542-546.
doi: 10.13433/j.cnki.1003-8728.2017.0408
Abstract:
In order to reduce the energy leakage and to improve the time-frequency analysis ability of the dual tree complex wavelet transform(DT-CWT) for non-stationary signal of machinery fault, the transfer function of the filter is improved to guarantee the orthogonality and to enhance the symmetry. The filter algorithm is also improved to make the reconstruction accuracy better. Finally, the initial shock response vector of the filter of scaling function is optimized. The calculation method is presented to construct the dual tree complex wavelet and filter based on the Hibert transform and Q-shift. The basic requirements for the filter design and calculation is proposed. The comparative experiments were conducted for the proposed method and the ordinary complex wavelet transform and discrete wavelet transform. The experimental results show that the reduction effect of noise and energy leakage for the proposed wavelet is better than othersThe present method was used to extract the weak failure information in machinery vibration signals to diagnose the mechanical fault. The experiments indicate that this method can obtain high signal-to-noise ratio(SNR) than the common methods and extract the fault feature submerged in a heavy noise effectively.
In order to reduce the energy leakage and to improve the time-frequency analysis ability of the dual tree complex wavelet transform(DT-CWT) for non-stationary signal of machinery fault, the transfer function of the filter is improved to guarantee the orthogonality and to enhance the symmetry. The filter algorithm is also improved to make the reconstruction accuracy better. Finally, the initial shock response vector of the filter of scaling function is optimized. The calculation method is presented to construct the dual tree complex wavelet and filter based on the Hibert transform and Q-shift. The basic requirements for the filter design and calculation is proposed. The comparative experiments were conducted for the proposed method and the ordinary complex wavelet transform and discrete wavelet transform. The experimental results show that the reduction effect of noise and energy leakage for the proposed wavelet is better than othersThe present method was used to extract the weak failure information in machinery vibration signals to diagnose the mechanical fault. The experiments indicate that this method can obtain high signal-to-noise ratio(SNR) than the common methods and extract the fault feature submerged in a heavy noise effectively.
2017, 36(4): 547-552.
doi: 10.13433/j.cnki.1003-8728.2017.0409
Abstract:
According to the structural features of the friction hoist with high speed and heavy load, the five degree-of-freedom longitudinal vibration model with elastic main axle of friction hoist system is established with reasonable simplification, and the model of a friction hoist is analyzed by numerical simulation. The results are compared with those of the traditional 4 degree of freedom model, the elastic effect of main axle on the design results is obtained.
According to the structural features of the friction hoist with high speed and heavy load, the five degree-of-freedom longitudinal vibration model with elastic main axle of friction hoist system is established with reasonable simplification, and the model of a friction hoist is analyzed by numerical simulation. The results are compared with those of the traditional 4 degree of freedom model, the elastic effect of main axle on the design results is obtained.
A New Matrix Expression Method for Whole Information to Describe and Analyze a Metamorphic Mechanism
2017, 36(4): 553-559.
doi: 10.13433/j.cnki.1003-8728.2017.0410
Abstract:
The paper discusses a matrix expression method for the configuration transformation of metamorphic mechanism. A matrix with whole information can describe all structural information on metamorphic mechanism, and we put forward its configuration transformation formula. The retrieval of the matrix can help obtain a lot of information, including number of kinematic joints, number of multiple components, number of multiple joints, size of multiple components, link connectivity, etc. The retrieval of its extension matrix produces kinematic parameters of the driving link and housing of the metamorphic mechanism. A case study demonstrates that this method can describe the driving link that is attached to another in the process of link increase or decrease and that the properties of the kinematic pair change obviously and completely without the need to renumber the initial configuration links.
The paper discusses a matrix expression method for the configuration transformation of metamorphic mechanism. A matrix with whole information can describe all structural information on metamorphic mechanism, and we put forward its configuration transformation formula. The retrieval of the matrix can help obtain a lot of information, including number of kinematic joints, number of multiple components, number of multiple joints, size of multiple components, link connectivity, etc. The retrieval of its extension matrix produces kinematic parameters of the driving link and housing of the metamorphic mechanism. A case study demonstrates that this method can describe the driving link that is attached to another in the process of link increase or decrease and that the properties of the kinematic pair change obviously and completely without the need to renumber the initial configuration links.
2017, 36(4): 560-566.
doi: 10.13433/j.cnki.1003-8728.2017.0411
Abstract:
A new-type gear cold roll-beating technology based on the generative principle is proposed, and the transmission ratio between the roller and the gear blank is given by using the kinematics analysis. To avoid the interference between the roller and the gear blank in the cold roll-beating process, the calculation method of the setting angle is given. Based on the constant-volume principle for plastic deformation, the blank diameter in cold roll-beating of involute gear is determined. With reference to the hob design method, the roller structure is designed and the effective teeth number of the roller is given. The roll-beating experiments of gear cold are carried out and the feasibility of the present method is demonstrated.
A new-type gear cold roll-beating technology based on the generative principle is proposed, and the transmission ratio between the roller and the gear blank is given by using the kinematics analysis. To avoid the interference between the roller and the gear blank in the cold roll-beating process, the calculation method of the setting angle is given. Based on the constant-volume principle for plastic deformation, the blank diameter in cold roll-beating of involute gear is determined. With reference to the hob design method, the roller structure is designed and the effective teeth number of the roller is given. The roll-beating experiments of gear cold are carried out and the feasibility of the present method is demonstrated.
2017, 36(4): 567-573.
doi: 10.13433/j.cnki.1003-8728.2017.0412
Abstract:
The loss of cutting tool in the electro discharge machining will directly influence the machining precision. Based on the feasibility of the electro discharge machining of the monocrystalline silicon, the effect of the peak current, pulse width and pulse interval on the loss of cutting tool is analyzed. The prediction model for the loss of cutting tool is established via RSM, considering the peak current, pulse width and pulse interval and other process parameters. The second order response surface of the loss of cutting tool and the process parameters is analyzed via Design-Expert 8.0. The analyzed results of variance show that the prediction model has a good fitting degree and adaptability. It uses satisfaction function (DFA) to obtain the best process parameters combination of the loss of cutting tool in the process of the electro discharge machining of the monocrystalline silicon. The average relative error between the prediction results and the experimentalunder the optimum processing parameters is 5.1%. The verification test show that the prediction model for the cutting tool loss is accurate, and the prediction of the loss of cutting tool in electro discharge machining for related semiconductor materials can be realized.
The loss of cutting tool in the electro discharge machining will directly influence the machining precision. Based on the feasibility of the electro discharge machining of the monocrystalline silicon, the effect of the peak current, pulse width and pulse interval on the loss of cutting tool is analyzed. The prediction model for the loss of cutting tool is established via RSM, considering the peak current, pulse width and pulse interval and other process parameters. The second order response surface of the loss of cutting tool and the process parameters is analyzed via Design-Expert 8.0. The analyzed results of variance show that the prediction model has a good fitting degree and adaptability. It uses satisfaction function (DFA) to obtain the best process parameters combination of the loss of cutting tool in the process of the electro discharge machining of the monocrystalline silicon. The average relative error between the prediction results and the experimentalunder the optimum processing parameters is 5.1%. The verification test show that the prediction model for the cutting tool loss is accurate, and the prediction of the loss of cutting tool in electro discharge machining for related semiconductor materials can be realized.
2017, 36(4): 574-578.
doi: 10.13433/j.cnki.1003-8728.2017.0413
Abstract:
In aircraft structural strength testing, the servo valve is chosen by the nominal rate of flow, and the hydraulic actuators is chosen by its load capacity and stroke, which will affect the matching characteristic of valve controlled hydraulic cylinder. Based on AMESim software, the valve controlled actuators model is built and the matching of valve controlled actuators is simulated and analyzed to obtain the boundary values of proportion gain. A physical test is conducted to verify the proposed method. The results show that the present method is effective. The study provides a method to choose and design servo valve and hydraulic actuators, and gives a theoretical basis for programming database for matching of valve controlled hydraulic cylinder.
In aircraft structural strength testing, the servo valve is chosen by the nominal rate of flow, and the hydraulic actuators is chosen by its load capacity and stroke, which will affect the matching characteristic of valve controlled hydraulic cylinder. Based on AMESim software, the valve controlled actuators model is built and the matching of valve controlled actuators is simulated and analyzed to obtain the boundary values of proportion gain. A physical test is conducted to verify the proposed method. The results show that the present method is effective. The study provides a method to choose and design servo valve and hydraulic actuators, and gives a theoretical basis for programming database for matching of valve controlled hydraulic cylinder.
2017, 36(4): 579-585.
doi: 10.13433/j.cnki.1003-8728.2017.0414
Abstract:
While data mining technology is applied to solve the knowledge acquisition of intelligent CAPP (Computer aided process planning) system, a serious problem is faced that it is hard for common users to use data mining. In order to overcome the problem, a method of data mining modeling by integrating ontology and CBR to control the data mining process intelligently is proposed. Firstly, a case base for data mining of process planning is built based on the ontological semantics; secondly, a reasoning mechanism in type of semantic understanding is established, as well as comprehensive evaluation and modification technique for data mining case is discussed. At lastly, the process planning of a typical mechanical part is taken for an example to test the present method. The experiments show that present method breaks the limit of traditional data mining, which has to be executed through the collaboration of domain experts and knowledge engineers, and is able to execute intelligent data mining. As a result, the threshold of its application is dramatically reduced.
While data mining technology is applied to solve the knowledge acquisition of intelligent CAPP (Computer aided process planning) system, a serious problem is faced that it is hard for common users to use data mining. In order to overcome the problem, a method of data mining modeling by integrating ontology and CBR to control the data mining process intelligently is proposed. Firstly, a case base for data mining of process planning is built based on the ontological semantics; secondly, a reasoning mechanism in type of semantic understanding is established, as well as comprehensive evaluation and modification technique for data mining case is discussed. At lastly, the process planning of a typical mechanical part is taken for an example to test the present method. The experiments show that present method breaks the limit of traditional data mining, which has to be executed through the collaboration of domain experts and knowledge engineers, and is able to execute intelligent data mining. As a result, the threshold of its application is dramatically reduced.
2017, 36(4): 586-591.
doi: 10.13433/j.cnki.1003-8728.2017.0415
Abstract:
The double cone drill was used to drill carbon fiber reinforced plastics (CFRP). A model for describing the drilling axial force and the spindle speed and feed rate was established by uasing the artificial neural networks with Back-propagation algorithm. Under the processing parameters, the comparative analysis of the change law of drilling axial force among three double cone drill which have variant ratio of the second cutting edge to the principal cutting edge. The results show that comparing with the multivariable linear regression model, the relative error prediction value via BP neural network model is lower than theexperimental, which the prediction errors via BP neural network model were below 3%. The maximum error via multiple linear regression model was 12.46%. BP neural network could be used to establish more accurately axial force prediction model. From the point of view reduce drilling axial force, the double cone drill with the ratio of the second cutting edge to the principal cutting edge has to be equal to 1 should be adopted.
The double cone drill was used to drill carbon fiber reinforced plastics (CFRP). A model for describing the drilling axial force and the spindle speed and feed rate was established by uasing the artificial neural networks with Back-propagation algorithm. Under the processing parameters, the comparative analysis of the change law of drilling axial force among three double cone drill which have variant ratio of the second cutting edge to the principal cutting edge. The results show that comparing with the multivariable linear regression model, the relative error prediction value via BP neural network model is lower than theexperimental, which the prediction errors via BP neural network model were below 3%. The maximum error via multiple linear regression model was 12.46%. BP neural network could be used to establish more accurately axial force prediction model. From the point of view reduce drilling axial force, the double cone drill with the ratio of the second cutting edge to the principal cutting edge has to be equal to 1 should be adopted.
2017, 36(4): 592-597.
doi: 10.13433/j.cnki.1003-8728.2017.0416
Abstract:
Sintered tungsten carbide was machined using CBN (Cubic boron nitride) tools under the assistance of laser heating and ultrasonic vibration. The variation characteristics of cutting force in the four cutting modes, including common cutting(CC), conventional ultrasonic vibration cutting(CUVC), ultrasonic elliptical vibration cutting (UEVC), laser and ultrasonic vibration combination cutting, were analyzed by means of the finite element analysis(FEA) method. The experiments were carried out on an ultra-precision lathe assisted by YAG laser equipment and self-developed ultrasonic vibration device. The precision cutting characteristics experiment of tungsten carbide with laser and ultrasonic vibration assistance were studied. The influence of the cutting parameters on the cutting force were studied via a series of contrast experiments. The results show that because of the softening of the workpiece material and the interrupted cutting, the laser and ultrasonic vibration combination cutting can greatly reduce the cutting force while machinability of tungsten carbide can be remarkably improved. The experimental results suggest that the precision machining of tungsten carbide can be realized under certain optimized technological parameters, which will effectively cost for precision machining of some other hard and brittle materials.
Sintered tungsten carbide was machined using CBN (Cubic boron nitride) tools under the assistance of laser heating and ultrasonic vibration. The variation characteristics of cutting force in the four cutting modes, including common cutting(CC), conventional ultrasonic vibration cutting(CUVC), ultrasonic elliptical vibration cutting (UEVC), laser and ultrasonic vibration combination cutting, were analyzed by means of the finite element analysis(FEA) method. The experiments were carried out on an ultra-precision lathe assisted by YAG laser equipment and self-developed ultrasonic vibration device. The precision cutting characteristics experiment of tungsten carbide with laser and ultrasonic vibration assistance were studied. The influence of the cutting parameters on the cutting force were studied via a series of contrast experiments. The results show that because of the softening of the workpiece material and the interrupted cutting, the laser and ultrasonic vibration combination cutting can greatly reduce the cutting force while machinability of tungsten carbide can be remarkably improved. The experimental results suggest that the precision machining of tungsten carbide can be realized under certain optimized technological parameters, which will effectively cost for precision machining of some other hard and brittle materials.
2017, 36(4): 598-604.
doi: 10.13433/j.cnki.1003-8728.2017.0417
Abstract:
Planetary roller screw mechanism (PRSM) has a lot of advantages such as high load, fine environmental adaptability, long life, et al. Load bearing characteristics of PRSM mainly include the analysis of mechanics of elements, axial deformation, load distribution over threads, load share among rollers, friction moment and wear. Research on load bearing characteristics aims to reveal the mechanisation of load transfer, deformation of components and wear of threads, and is the way to further improve its transmission performance and service life. In this paper, the load bearing principle of PRSM is introduced, and on the basis of it, the main achievements on load bearing characteristics are summarized. Finally, some suggestions are presented for future research on load bearing characteristics of PRSM.
Planetary roller screw mechanism (PRSM) has a lot of advantages such as high load, fine environmental adaptability, long life, et al. Load bearing characteristics of PRSM mainly include the analysis of mechanics of elements, axial deformation, load distribution over threads, load share among rollers, friction moment and wear. Research on load bearing characteristics aims to reveal the mechanisation of load transfer, deformation of components and wear of threads, and is the way to further improve its transmission performance and service life. In this paper, the load bearing principle of PRSM is introduced, and on the basis of it, the main achievements on load bearing characteristics are summarized. Finally, some suggestions are presented for future research on load bearing characteristics of PRSM.
2017, 36(4): 605-609.
doi: 10.13433/j.cnki.1003-8728.2017.0418
Abstract:
In the low-speed wire electrical discharge machining (LS-WEDM), because the wire electrode is influenced by external disturbance and the control system itself, the wire tension fluctuates mildly in some ranges, and the maximum amplitude can reach 30%. This fact can lead to violent wire deflection and vibration between two guide wheels and seriously influence the geometrical accuracy and surface quality. In this paper, firstly, a detailed force analysis has been implemented, and an improved wire winding system has been introduced. Secondly, a constant wire tension control closed-loop system has been designed, and a mixed algorithm based on the improved Particle Swarm Optimization (Improved-PSO) and Proportion Integration Differentiation (PID) has been used to carry out the online control of the wire tension. Finally, a large number of experiments have been carried out by using this control system. The experimental results show that this closed-loop control system has high precision and real-time, that the wave amplitude of the wire tension can be controlled within 5%, and that the lateral vibration of wire can be reduced by approximately 50%. Therefore, this control system is practical and feasible and can be applied to the WEDM field.
In the low-speed wire electrical discharge machining (LS-WEDM), because the wire electrode is influenced by external disturbance and the control system itself, the wire tension fluctuates mildly in some ranges, and the maximum amplitude can reach 30%. This fact can lead to violent wire deflection and vibration between two guide wheels and seriously influence the geometrical accuracy and surface quality. In this paper, firstly, a detailed force analysis has been implemented, and an improved wire winding system has been introduced. Secondly, a constant wire tension control closed-loop system has been designed, and a mixed algorithm based on the improved Particle Swarm Optimization (Improved-PSO) and Proportion Integration Differentiation (PID) has been used to carry out the online control of the wire tension. Finally, a large number of experiments have been carried out by using this control system. The experimental results show that this closed-loop control system has high precision and real-time, that the wave amplitude of the wire tension can be controlled within 5%, and that the lateral vibration of wire can be reduced by approximately 50%. Therefore, this control system is practical and feasible and can be applied to the WEDM field.
2017, 36(4): 610-615.
doi: 10.13433/j.cnki.1003-8728.2017.0419
Abstract:
In order to simplify development process and cut down the period of cab mounting system, the co-simulation method is used to solve the multi-objective optimization problem of a loader cab mounting system's vibration isolation performance whose virtual prototype is built in ADAMS, excitation signals come from experimental test and optimization algorithms are coded in MATLAB. The objective includes minimization of vibration total value and maximization decoupling ratio. The multi-objective particle swarm optimization (MOPSO) algorithm shows a better optimization performance than non-dominated sorting genetic (NSGA-Ⅱ) algorithm by covering a better Pareto frontier in this problem. Simulation results also confirm the feasibility and effectiveness of the approach in this study.
In order to simplify development process and cut down the period of cab mounting system, the co-simulation method is used to solve the multi-objective optimization problem of a loader cab mounting system's vibration isolation performance whose virtual prototype is built in ADAMS, excitation signals come from experimental test and optimization algorithms are coded in MATLAB. The objective includes minimization of vibration total value and maximization decoupling ratio. The multi-objective particle swarm optimization (MOPSO) algorithm shows a better optimization performance than non-dominated sorting genetic (NSGA-Ⅱ) algorithm by covering a better Pareto frontier in this problem. Simulation results also confirm the feasibility and effectiveness of the approach in this study.
2017, 36(4): 616-620.
doi: 10.13433/j.cnki.1003-8728.2017.0420
Abstract:
An equivalent modeling method of ring isolator was proposed, and a vibration analysis model of dynamic cabin, which included power unit, ring isolator and cabin shell, was established using ANSYS. The simulation results were compared with the experimental ones to show the validity of the finite element model. Effects of some major parameters on vibration transmission characteristics were discussed. The parameter study result shows that large error will occur with high simplification degree of power unit; decreasing the radial stiffness of ring isolator or increasing the structural damping of the cabin shell can reduce structural vibration response of dynamical systems in high frequency band, but they have no significant effect on anti-vibration in low frequency band.
An equivalent modeling method of ring isolator was proposed, and a vibration analysis model of dynamic cabin, which included power unit, ring isolator and cabin shell, was established using ANSYS. The simulation results were compared with the experimental ones to show the validity of the finite element model. Effects of some major parameters on vibration transmission characteristics were discussed. The parameter study result shows that large error will occur with high simplification degree of power unit; decreasing the radial stiffness of ring isolator or increasing the structural damping of the cabin shell can reduce structural vibration response of dynamical systems in high frequency band, but they have no significant effect on anti-vibration in low frequency band.
2017, 36(4): 621-625.
doi: 10.13433/j.cnki.1003-8728.2017.0421
Abstract:
A 21-DOF model of the tracked vehicle with 6 pairs of wheels including power-transmission system was built based on the multi-body dynamics method. Combined with a simplified slope model, rules of suspension breakdown during different slope conditions were studied by simulations. Results showed that the critical speed of vehicle occurring suspension breakdown is a "W" curve with different slope-vehicle angles, and one of the first pair of suspension always break down at first. When the slope angle being bigger, the minimum of critical speed of suspension breakdown decreases quickly and its corresponding slope-vehicle angle increases. Moreover, impacts on the front of vehicle body influencing by suspension breakdown increase greatly.
A 21-DOF model of the tracked vehicle with 6 pairs of wheels including power-transmission system was built based on the multi-body dynamics method. Combined with a simplified slope model, rules of suspension breakdown during different slope conditions were studied by simulations. Results showed that the critical speed of vehicle occurring suspension breakdown is a "W" curve with different slope-vehicle angles, and one of the first pair of suspension always break down at first. When the slope angle being bigger, the minimum of critical speed of suspension breakdown decreases quickly and its corresponding slope-vehicle angle increases. Moreover, impacts on the front of vehicle body influencing by suspension breakdown increase greatly.
2017, 36(4): 626-631.
doi: 10.13433/j.cnki.1003-8728.2017.0422
Abstract:
The transient exterior flow fields were calculated with a turbulence model: detached eddy simulation (DES) method to get the fluctuating pressure on car body. Pseudo-excitation method (PEM) was used to calculate the interior acoustic fields and the sound pressure level spectrum was got by acoustic-vibration coupling method. Noise characteristics at different field points were compared under different vehicle velocity conditions. Road experiments were implemented to verify the effects of simulations. Results show that the aeroacoustic noise is a kind of noise with wide frequency bands, which decreases in the form of exponential function when reaching the peak value. Both the frequencies of zero value and peak value become higher when the vehicle velocity increases. The amplitudes of sound pressure level are relative to the intensity of fluctuating pressure and the radiation surface areas, and the application of PEM on aerodynamic noise simulations is feasible.
The transient exterior flow fields were calculated with a turbulence model: detached eddy simulation (DES) method to get the fluctuating pressure on car body. Pseudo-excitation method (PEM) was used to calculate the interior acoustic fields and the sound pressure level spectrum was got by acoustic-vibration coupling method. Noise characteristics at different field points were compared under different vehicle velocity conditions. Road experiments were implemented to verify the effects of simulations. Results show that the aeroacoustic noise is a kind of noise with wide frequency bands, which decreases in the form of exponential function when reaching the peak value. Both the frequencies of zero value and peak value become higher when the vehicle velocity increases. The amplitudes of sound pressure level are relative to the intensity of fluctuating pressure and the radiation surface areas, and the application of PEM on aerodynamic noise simulations is feasible.
2017, 36(4): 632-636.
doi: 10.13433/j.cnki.1003-8728.2017.0423
Abstract:
This paper describes the influence of ground effect on the form of diffuser. The FSAE car diffuser is designed on the premise of meeting the requirements of FSAE car design rules. The computational fluid dynamics(CFD) technique is adopted to simulate the diffuser flow field, and the diffuser is further optimized to enhances its working efficiency, which provides more downforce for the car and improves the handling stability and safety of the car. The analysis show that the lift coefficient of the FSAE car is decreased from 0.391 originally to -0.371 with the designed diffuser, and the drag coefficient changes from 0.589 into 0.583.
This paper describes the influence of ground effect on the form of diffuser. The FSAE car diffuser is designed on the premise of meeting the requirements of FSAE car design rules. The computational fluid dynamics(CFD) technique is adopted to simulate the diffuser flow field, and the diffuser is further optimized to enhances its working efficiency, which provides more downforce for the car and improves the handling stability and safety of the car. The analysis show that the lift coefficient of the FSAE car is decreased from 0.391 originally to -0.371 with the designed diffuser, and the drag coefficient changes from 0.589 into 0.583.
2017, 36(4): 637-642.
doi: 10.13433/j.cnki.1003-8728.2017.0424
Abstract:
The accurate acquisition of longitudinal velocity and tire-road force is the premise and foundation of vehicle active safety control. Because the sensors of longitudinal velocity and tire force are expensive, we conduct the longitudinal velocity estimation based on the random Kalman filter (RKF) tire force estimator. First, the lateral tire force estimator based on the RKF is designed by using the vehicle states which are measured from on-board sensor combined with the vehicle's seven-DOF model. Then, the Kalman filtering algorithm is adopted to realize the estimation of the longitudinal velocity by relying on the estimated tire force. The co-simulations carried out by CarSim and MATLAB/Simulink demonstrate the effectiveness of the proposed estimator.
The accurate acquisition of longitudinal velocity and tire-road force is the premise and foundation of vehicle active safety control. Because the sensors of longitudinal velocity and tire force are expensive, we conduct the longitudinal velocity estimation based on the random Kalman filter (RKF) tire force estimator. First, the lateral tire force estimator based on the RKF is designed by using the vehicle states which are measured from on-board sensor combined with the vehicle's seven-DOF model. Then, the Kalman filtering algorithm is adopted to realize the estimation of the longitudinal velocity by relying on the estimated tire force. The co-simulations carried out by CarSim and MATLAB/Simulink demonstrate the effectiveness of the proposed estimator.
Study on Absorption Characterestics of Micro-perforated Panel Array based on Electro-acoustic Theory
2017, 36(4): 643-647.
doi: 10.13433/j.cnki.1003-8728.2017.0425
Abstract:
Acoustic finite element method for calculating the absorption coefficient of micro-perforated panel array is complex and hard to achieve. The normal incidence absorption coefficient, oblique incidence absorption coefficient and random incidence absorption coefficient are calculated using electro-acoustic equivalent circuit model. Measurement of the normal incidence coefficients are carried out to validate the Electro-acoustic equivalent circuit model. Experimental results show that the absorption coefficients can be up to 0.6 in the range of three octaves by adjusting the depth of diffident units in micro-perforated array and theoretical and experimental results are in good agreement.
Acoustic finite element method for calculating the absorption coefficient of micro-perforated panel array is complex and hard to achieve. The normal incidence absorption coefficient, oblique incidence absorption coefficient and random incidence absorption coefficient are calculated using electro-acoustic equivalent circuit model. Measurement of the normal incidence coefficients are carried out to validate the Electro-acoustic equivalent circuit model. Experimental results show that the absorption coefficients can be up to 0.6 in the range of three octaves by adjusting the depth of diffident units in micro-perforated array and theoretical and experimental results are in good agreement.
2017, 36(4): 648-652.
doi: 10.13433/j.cnki.1003-8728.2017.0426
Abstract:
Structural composition of a new-type composite-structure aero measuring rake which is equipped on aircraft engine is investigated and the computer simulation for it by using software ANSYS is carried out. Conception for vibration stress survey of the new-type aero measuring rake is designed, and the evaluation analysis for the conception is conducted based on finite element analysis results. Simulation results show that errors of maximum tensile stresses of vibration stress measuring points, which are chosen by project design, compared to corresponding sections are not exceeding 2.5%, which is lower than engineering acceptable error demands. The rationality and validity of conceptual design for vibration stress survey of a new-type aero measuring rake is verified and important reference is provided for design and modification of this rake.
Structural composition of a new-type composite-structure aero measuring rake which is equipped on aircraft engine is investigated and the computer simulation for it by using software ANSYS is carried out. Conception for vibration stress survey of the new-type aero measuring rake is designed, and the evaluation analysis for the conception is conducted based on finite element analysis results. Simulation results show that errors of maximum tensile stresses of vibration stress measuring points, which are chosen by project design, compared to corresponding sections are not exceeding 2.5%, which is lower than engineering acceptable error demands. The rationality and validity of conceptual design for vibration stress survey of a new-type aero measuring rake is verified and important reference is provided for design and modification of this rake.
2017, 36(4): 653-656.
doi: 10.13433/j.cnki.1003-8728.2017.0427
Abstract:
The axial-symmetric vectoring exhaust nozzle driving by three ringsis one of the convergent/divergent type nozzles. In this paper, the inverse kinematics modeling for throat area of axial-symmetric vectoring exhaust nozzle is given by using the relative rotation angle method. The three dimensional model for nozzle was built via CATIA software and its kinematics simulation was carried out via ADAMS, the computer simulation results showed that the mechanic design was reasonable and the kinematics modeling was effective, which provided an important reference for optimizing and controllingthe axial-symmetric vectoring exhaust nozzles driving by three rings.
The axial-symmetric vectoring exhaust nozzle driving by three ringsis one of the convergent/divergent type nozzles. In this paper, the inverse kinematics modeling for throat area of axial-symmetric vectoring exhaust nozzle is given by using the relative rotation angle method. The three dimensional model for nozzle was built via CATIA software and its kinematics simulation was carried out via ADAMS, the computer simulation results showed that the mechanic design was reasonable and the kinematics modeling was effective, which provided an important reference for optimizing and controllingthe axial-symmetric vectoring exhaust nozzles driving by three rings.
