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RSS2018 Vol. 37, No. 11
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2018, 37(11): 1641-1649.
doi: 10.13433/j.cnki.1003-8728.20180127
PDF 1188KB
Abstract:
The finger seal as the component of a rotor system and the mechanical interaction between the finger seal and the rotor affect the dynamic characteristics of the system. Therefore we propose the seal force calculation method to build the rotor system's dynamics model and analyze its related dynamics. In this paper, the gas film stiffness and gas film damping of the finger seal are realized by means of solid-fluid coupling analysis, and the related fitting formulas are established. Then, the mechanical model of finger seal/rotor interaction is established by combining finger seal/rotor contact processes; a method of calculating the seal force which is applied to the dynamic analysis of the rotor system is proposed. The calculation process of seal force is also implemented by an example and the relationship between seal force and working conditions is discussed. The results show preliminarily that:The gas film stiffness of the finger seal increases with the increase of fluid pressure, and the rotor speed has little influence on the film stiffness; the gas film damping of finger seal decreases with the increase of fluid pressure and rotor speed. The seal force in contact region increases with the rotor's whirl amplitude but basically does not change with the rotor speed; the seal force in the non-contact region decreases with the increase of the rotor's whirl amplitude and increases with the rotor speed. The seal force varies periodically with time, and the frequency of sealing force increases with the increase of rotor frequency.
The finger seal as the component of a rotor system and the mechanical interaction between the finger seal and the rotor affect the dynamic characteristics of the system. Therefore we propose the seal force calculation method to build the rotor system's dynamics model and analyze its related dynamics. In this paper, the gas film stiffness and gas film damping of the finger seal are realized by means of solid-fluid coupling analysis, and the related fitting formulas are established. Then, the mechanical model of finger seal/rotor interaction is established by combining finger seal/rotor contact processes; a method of calculating the seal force which is applied to the dynamic analysis of the rotor system is proposed. The calculation process of seal force is also implemented by an example and the relationship between seal force and working conditions is discussed. The results show preliminarily that:The gas film stiffness of the finger seal increases with the increase of fluid pressure, and the rotor speed has little influence on the film stiffness; the gas film damping of finger seal decreases with the increase of fluid pressure and rotor speed. The seal force in contact region increases with the rotor's whirl amplitude but basically does not change with the rotor speed; the seal force in the non-contact region decreases with the increase of the rotor's whirl amplitude and increases with the rotor speed. The seal force varies periodically with time, and the frequency of sealing force increases with the increase of rotor frequency.
2018, 37(11): 1650-1655.
doi: 10.13433/j.cnki.1003-8728.20180134
Abstract:
Aiming at the limitation of the passive obstacle surmounting method of wheeled robots in unstructured ground environment, this paper proposes an articulated series eight-wheeled robot with active and passive obstacle surmounting method. The robot includes two symmetrical bodies connected by a hydraulic cylinder and a hinge mechanism. By controlling the hydraulic stroke displacement and hard and soft conditions, the robot can transform its attitude and surmount the vertical obstacle higher than its wheel's diameter. This paper establishes the robot centroid movement model and analyzes the obstacle surmount mechanism of this robot on vertical obstacle and moat. Then, an obstacle surmounting simulation is carried out on ADAMS, and a real prototype experiment is also carried out. The results confirm that the robot can surmount the vertical obstacle height which is 1.5 times higher than the wheel diameter and 1.5 times higher than wheelbase moat, having a good ability to surmount obstacles in the unstructured ground environment.
Aiming at the limitation of the passive obstacle surmounting method of wheeled robots in unstructured ground environment, this paper proposes an articulated series eight-wheeled robot with active and passive obstacle surmounting method. The robot includes two symmetrical bodies connected by a hydraulic cylinder and a hinge mechanism. By controlling the hydraulic stroke displacement and hard and soft conditions, the robot can transform its attitude and surmount the vertical obstacle higher than its wheel's diameter. This paper establishes the robot centroid movement model and analyzes the obstacle surmount mechanism of this robot on vertical obstacle and moat. Then, an obstacle surmounting simulation is carried out on ADAMS, and a real prototype experiment is also carried out. The results confirm that the robot can surmount the vertical obstacle height which is 1.5 times higher than the wheel diameter and 1.5 times higher than wheelbase moat, having a good ability to surmount obstacles in the unstructured ground environment.
2018, 37(11): 1656-1661.
doi: 10.13433/j.cnki.1003-8728.20180125
Abstract:
Analysis of airflow field in aero-engine bearing chamber is essential to design of secondary flow system as well as lubrication system. The investigations of the velocity, temperature and pressure fields for the air in an aero-engine bearing chamber were conducted with the finite element method. The influence of the rotor speeds on the velocity, temperature and pressure between the connection field in bearing chamber was discussed. The results show that the velocity and temperature of air increase with the increasing of rotor speeds while the pressure difference among the adjacent chambers decreases with the increasing of rotor speed. The accuracy and low computaion time of the present method is demonstrated by comparing the results via the airflow fields and the air/droplet coupling fields.
Analysis of airflow field in aero-engine bearing chamber is essential to design of secondary flow system as well as lubrication system. The investigations of the velocity, temperature and pressure fields for the air in an aero-engine bearing chamber were conducted with the finite element method. The influence of the rotor speeds on the velocity, temperature and pressure between the connection field in bearing chamber was discussed. The results show that the velocity and temperature of air increase with the increasing of rotor speeds while the pressure difference among the adjacent chambers decreases with the increasing of rotor speed. The accuracy and low computaion time of the present method is demonstrated by comparing the results via the airflow fields and the air/droplet coupling fields.
2018, 37(11): 1662-1669.
doi: 10.13433/j.cnki.1003-8728.20180116
Abstract:
To ensure the stability and consistency of the engine after assembly, the relationship between process data and cold test quality data in engine assembly production was studied by the vibration peak of cylinder head in engine cold test. The influence of bolt tightening quality on the high vibration peak of cylinder head was firstly determined by grey relational analysis, and then the factors affecting the vibration of cylinder head. By establishing neural networks and support vector machines models, real-time analysis of production data was made to achieve the prediction of engine quality data, which was used in the practical production of the cold test auxiliary, to guide the production process standard improvement. In this fact, improving the overall performance of the engine can be achieved by modifying the process parameters.
To ensure the stability and consistency of the engine after assembly, the relationship between process data and cold test quality data in engine assembly production was studied by the vibration peak of cylinder head in engine cold test. The influence of bolt tightening quality on the high vibration peak of cylinder head was firstly determined by grey relational analysis, and then the factors affecting the vibration of cylinder head. By establishing neural networks and support vector machines models, real-time analysis of production data was made to achieve the prediction of engine quality data, which was used in the practical production of the cold test auxiliary, to guide the production process standard improvement. In this fact, improving the overall performance of the engine can be achieved by modifying the process parameters.
2018, 37(11): 1670-1677.
doi: 10.13433/j.cnki.1003-8728.20180077
Abstract:
According to Hamilton principle, a mathematical model of lateral vibration of horizontal drill string is established by considering the coupling between drilling mud and drillstring. The effects of internal and external drilling mud velocity, drilling mud density, viscosity coefficient of drilling mud, gravity, friction and WOB (Weight on bit)on the lateral vibration of drillstring were analyzed. The lateral vibration characteristics of drill string under different WOB and drilling mud velocity were simulated based on the self-developed dynamic test device for horizontal drillstring. The research results show that the increase of WOB, the exciting of drilling mud and the flow velocity all results in the decrease of the lateral vibration frequency and the increase of vibration amplitude for the drillstring.
According to Hamilton principle, a mathematical model of lateral vibration of horizontal drill string is established by considering the coupling between drilling mud and drillstring. The effects of internal and external drilling mud velocity, drilling mud density, viscosity coefficient of drilling mud, gravity, friction and WOB (Weight on bit)on the lateral vibration of drillstring were analyzed. The lateral vibration characteristics of drill string under different WOB and drilling mud velocity were simulated based on the self-developed dynamic test device for horizontal drillstring. The research results show that the increase of WOB, the exciting of drilling mud and the flow velocity all results in the decrease of the lateral vibration frequency and the increase of vibration amplitude for the drillstring.
2018, 37(11): 1678-1684.
doi: 10.13433/j.cnki.1003-8728.20180115
Abstract:
A new wing support platform composed of multiple 2R1T parallel mechanisms is designed. The active branch chains of all parallel mechanisms are coordinated by hydraulic interconnection to achieve coordinated adaptive adjustment of all moving platforms, so that they have better airfoil matching degree. The dimensional analysis of the parallel mechanism is carried out based on the comprehensive constraints of multiple evaluation indexes. The evaluation index under different constraint conditions is established using the monotonicity analysis method. According to the principle of optimal performances, a unified ratio coefficient is introduced to determine the feasible domain of the dimensional parameters. Finally, an optimal dimensional parameter feasible region of the parallel mechanism is determined with comprehensive constraints of multiple evaluation indexes and taking the motion deviation rate of the parallel platform center as the initial target in the example.
A new wing support platform composed of multiple 2R1T parallel mechanisms is designed. The active branch chains of all parallel mechanisms are coordinated by hydraulic interconnection to achieve coordinated adaptive adjustment of all moving platforms, so that they have better airfoil matching degree. The dimensional analysis of the parallel mechanism is carried out based on the comprehensive constraints of multiple evaluation indexes. The evaluation index under different constraint conditions is established using the monotonicity analysis method. According to the principle of optimal performances, a unified ratio coefficient is introduced to determine the feasible domain of the dimensional parameters. Finally, an optimal dimensional parameter feasible region of the parallel mechanism is determined with comprehensive constraints of multiple evaluation indexes and taking the motion deviation rate of the parallel platform center as the initial target in the example.
2018, 37(11): 1685-1692.
doi: 10.13433/j.cnki.1003-8728.20180052
Abstract:
Workspace analysis and dimension parameter optimal design of a new type of 3T1R parallel mechanism, namely 4-RUPaR parallel mechanism, are carried out. Firstly, the link-length of the mechanism is taken as the constraint condition to obtain the inverse kinematic equation with the coordinate transformation theory in analytic geometry. Secondly, the constraint condition of workspace is established based on the inverse kinematics equation and the visualization of the workspace of the mechanism is programmed in MATLAB. The dimension of the workspace is approximately expressed with point sets. Finally, the relationship between the dimensional parameters of the parallel mechanism and the fixed attitude workspace is obtained with the single variable analysis method. To maximize the workspace as the optimization objective, the differential evolution algorithm is used to solve the optimization problem. Good dimensional parameters are obtained; the effective workspace of the parallel mechanism is larger and more robust and is in agreement with practical engineering requirements.
Workspace analysis and dimension parameter optimal design of a new type of 3T1R parallel mechanism, namely 4-RUPaR parallel mechanism, are carried out. Firstly, the link-length of the mechanism is taken as the constraint condition to obtain the inverse kinematic equation with the coordinate transformation theory in analytic geometry. Secondly, the constraint condition of workspace is established based on the inverse kinematics equation and the visualization of the workspace of the mechanism is programmed in MATLAB. The dimension of the workspace is approximately expressed with point sets. Finally, the relationship between the dimensional parameters of the parallel mechanism and the fixed attitude workspace is obtained with the single variable analysis method. To maximize the workspace as the optimization objective, the differential evolution algorithm is used to solve the optimization problem. Good dimensional parameters are obtained; the effective workspace of the parallel mechanism is larger and more robust and is in agreement with practical engineering requirements.
2018, 37(11): 1693-1697.
doi: 10.13433/j.cnki.1003-8728.20180140
Abstract:
Owing to the nonlinearity of the electro-hydraulic servo system, the conventional control methods produce poor control performances. Aiming at the nonlinear control of the electro-hydraulic servo system, a nonlinear predictive control algorithm based on multi-objective particle swarm optimization (MPSO-NPC) is presented. The regulating factor proposed in this paper combines the notion of multi-objective optimization with nonlinear predictive control. This factor can realize the multi-objective optimization and adjusts predictive weights in a cost function. The burden of calculation in this algorithm is reduced, and a good real-time performance is produced. The controller based on the MPSO-NPC can effectively track the output of the electro-hydraulic servo system. The simulation results show the correctness and effectiveness of the method proposed in this paper.
Owing to the nonlinearity of the electro-hydraulic servo system, the conventional control methods produce poor control performances. Aiming at the nonlinear control of the electro-hydraulic servo system, a nonlinear predictive control algorithm based on multi-objective particle swarm optimization (MPSO-NPC) is presented. The regulating factor proposed in this paper combines the notion of multi-objective optimization with nonlinear predictive control. This factor can realize the multi-objective optimization and adjusts predictive weights in a cost function. The burden of calculation in this algorithm is reduced, and a good real-time performance is produced. The controller based on the MPSO-NPC can effectively track the output of the electro-hydraulic servo system. The simulation results show the correctness and effectiveness of the method proposed in this paper.
2018, 37(11): 1698-1704.
doi: 10.13433/j.cnki.1003-8728.20180118
Abstract:
In order to analyze the intermediate frequency cabin noise of special vehicle better, a hybrid FE-SEA (Finite element-statistical energy analysis) method is used, and the hybrid FE-SEA model was established to obtain the modal density of each subsystem, the internal loss factor, coupling loss factor and radiation efficiency of FE body according to the theoretical method. And the excitations on engine mount and transfer case suspension were obtained through the real vehicle test data. The obtained parameters and excitations are applied to the hybrid FE-SEA model, and the FE subsystem is modeled in the frequency range of 200~800 Hz. Then, the noise pressure level of the vehicle interior is obtained by simulation prediction, at the same time, compared with the test results, the absolute error is within 7%, showing that the precision of the simulation model is better. Finally, the power contribution of the body panels is analyzed, the main power contribution of the acoustic cavity noise in the cab and the lower part of the tune are obtained.
In order to analyze the intermediate frequency cabin noise of special vehicle better, a hybrid FE-SEA (Finite element-statistical energy analysis) method is used, and the hybrid FE-SEA model was established to obtain the modal density of each subsystem, the internal loss factor, coupling loss factor and radiation efficiency of FE body according to the theoretical method. And the excitations on engine mount and transfer case suspension were obtained through the real vehicle test data. The obtained parameters and excitations are applied to the hybrid FE-SEA model, and the FE subsystem is modeled in the frequency range of 200~800 Hz. Then, the noise pressure level of the vehicle interior is obtained by simulation prediction, at the same time, compared with the test results, the absolute error is within 7%, showing that the precision of the simulation model is better. Finally, the power contribution of the body panels is analyzed, the main power contribution of the acoustic cavity noise in the cab and the lower part of the tune are obtained.
2018, 37(11): 1705-1710.
doi: 10.13433/j.cnki.1003-8728.20180123
Abstract:
Blade are important component in aeroengine with high cost. Therefore, in order to repair the damaged blades, the points cloud must be accurately obtained. This paper will propose a novel measurement method with the virtual stereo vision. Firstly, the principle and advantages of the virtual stereo vision are analyzed, and the internal and external parameters are calibrated by using the nonparametric model and precision calibration target. Then, the KLT (Kanade-Lucas-Tomasi)algorithm and epipolar constraints are used to realize the stereo matching between the speckle points. Finally, the method to minimize the sum of squared distance between the point and the projective ray is utilized as the constraint condition to calculate the spatial coordinates of blade point cloud. The experimental results show that the correlation coefficient of the fitting blade surface is larger than 0.99, and the mean error of blade surface geometry value is less than 0.2 mm. Therefore, the high accuracy and reliability for the points cloud of aeroengine blade can be acquired with a simplified system.
Blade are important component in aeroengine with high cost. Therefore, in order to repair the damaged blades, the points cloud must be accurately obtained. This paper will propose a novel measurement method with the virtual stereo vision. Firstly, the principle and advantages of the virtual stereo vision are analyzed, and the internal and external parameters are calibrated by using the nonparametric model and precision calibration target. Then, the KLT (Kanade-Lucas-Tomasi)algorithm and epipolar constraints are used to realize the stereo matching between the speckle points. Finally, the method to minimize the sum of squared distance between the point and the projective ray is utilized as the constraint condition to calculate the spatial coordinates of blade point cloud. The experimental results show that the correlation coefficient of the fitting blade surface is larger than 0.99, and the mean error of blade surface geometry value is less than 0.2 mm. Therefore, the high accuracy and reliability for the points cloud of aeroengine blade can be acquired with a simplified system.
2018, 37(11): 1711-1715.
doi: 10.13433/j.cnki.1003-8728.20180075
Abstract:
The influence of the third time cutting parameters of medium-speed wire cut electrical discharge machining (MS-WEDM) multiple cutting on the surface quality and cutting speed was studied, which was conducive to improve the quality of multiple cutting process. It was a single factor experiment to study the influence that the third cutting parameters of pulse width, inter-pulse, power amplifier, and wire speed on the surface roughness and cutting speed. It made experiment of the orthogonal experiment with four level and four factors. With comprehensive evaluation method made multi-objective optimization problem of the surface roughness and the cutting speed, which was transformed into single objective problem of the weighted composite score. The results show that the more optimal pulse width is 2 μs, the optimal pulse interval is 5 μs, the optimal power amplifier is 1, the optimal wire speed is 3 m/s, and the surface roughness is 1.26 μm, the cutting speed is 84.86 mm2/min, the weighted composite score is 0.22.
The influence of the third time cutting parameters of medium-speed wire cut electrical discharge machining (MS-WEDM) multiple cutting on the surface quality and cutting speed was studied, which was conducive to improve the quality of multiple cutting process. It was a single factor experiment to study the influence that the third cutting parameters of pulse width, inter-pulse, power amplifier, and wire speed on the surface roughness and cutting speed. It made experiment of the orthogonal experiment with four level and four factors. With comprehensive evaluation method made multi-objective optimization problem of the surface roughness and the cutting speed, which was transformed into single objective problem of the weighted composite score. The results show that the more optimal pulse width is 2 μs, the optimal pulse interval is 5 μs, the optimal power amplifier is 1, the optimal wire speed is 3 m/s, and the surface roughness is 1.26 μm, the cutting speed is 84.86 mm2/min, the weighted composite score is 0.22.
2018, 37(11): 1716-1721.
doi: 10.13433/j.cnki.1003-8728.20180119
Abstract:
Due to the difficulty in selecting hydrocyclone empirically to achieve the best separation effect, this paper discusses the influence of 6 factors on separation prevention. The first 6 columns of the L64 (89) table is choosen for various data groups, and the ELM model is established to compare the orthogonal results. The results show that the reflected ELM model and the orthogonal experiments can only give a set of optimal combinations, the separation effect is 63.08%, the prediction of the separation results on ELM with 4 sets of values and the optimal combination of orthogonal experiments is close to or equal to 63.01%, 62.78%, 63.02% and 63.08%, respectively. Therefore, in the process of producing a cyclone, the multi group results predicted by the ELM model can be used as a reference to save the cost of post selection.
Due to the difficulty in selecting hydrocyclone empirically to achieve the best separation effect, this paper discusses the influence of 6 factors on separation prevention. The first 6 columns of the L64 (89) table is choosen for various data groups, and the ELM model is established to compare the orthogonal results. The results show that the reflected ELM model and the orthogonal experiments can only give a set of optimal combinations, the separation effect is 63.08%, the prediction of the separation results on ELM with 4 sets of values and the optimal combination of orthogonal experiments is close to or equal to 63.01%, 62.78%, 63.02% and 63.08%, respectively. Therefore, in the process of producing a cyclone, the multi group results predicted by the ELM model can be used as a reference to save the cost of post selection.
2018, 37(11): 1722-1730.
doi: 10.13433/j.cnki.1003-8728.20180069
Abstract:
In the intelligent fault diagnosis of rotating machinery, the unsupervised learning with the complex network structure has some problems, such as too large parameters, long training time and not satisfactory diagnosis accuracy with the simple learning structure. Aiming at the above problems, this paper uses fuzzy information granulation and sparse auto-encoder to construct a parallel learning network. At the same time, the sparse auto-encoder of the parallel structure adaptively extracts the features of multiple parameters reconstructed after granulation, and then the extracted features are fused and classified with random forest. Experimental results show that this method can identify faults with high accuracy. Compared with the commonly used methods with the serial network structure, the method not only reduces the network parameter adjustment complexity and the multi-layer network influence but also reduces the training time, while improving the diagnostic accuracy.
In the intelligent fault diagnosis of rotating machinery, the unsupervised learning with the complex network structure has some problems, such as too large parameters, long training time and not satisfactory diagnosis accuracy with the simple learning structure. Aiming at the above problems, this paper uses fuzzy information granulation and sparse auto-encoder to construct a parallel learning network. At the same time, the sparse auto-encoder of the parallel structure adaptively extracts the features of multiple parameters reconstructed after granulation, and then the extracted features are fused and classified with random forest. Experimental results show that this method can identify faults with high accuracy. Compared with the commonly used methods with the serial network structure, the method not only reduces the network parameter adjustment complexity and the multi-layer network influence but also reduces the training time, while improving the diagnostic accuracy.
2018, 37(11): 1731-1736.
doi: 10.13433/j.cnki.1003-8728.20180121
Abstract:
In order to detect the operation fault of wind turbine in real-time and recognize its health status of the unit, a bearing health status recognition method based on vibration signal analysis using ITD (Intrinsic time-scale decomposition)-MSE (multiscale entropy)is proposed in this paper. The method is applied to ensure that the vibration signal is pretreated, and the time domain characteristics of the reconstructed signal are extracted, the ELM (Extreme learning machine) is then adopted to recognize the health status of wind turbine bearings. Firstly, the vibration signal of wind turbine bearings is decomposed using ITD to obtain a series of inherent rotation components. Then, MSE is calculated and used as a standard to select relevant components to reconstruct the signal. Afterwards, the reconstructed signals' RMS, kurtosis, crest factor and peak-to-peak value are calculated to input to the ELM model. Finally, the ELM model is established and the health status of wind turbine bearings can be recognized. The experimental results have shown that the proposed method is capable of recognizing the health status of wind turbine bearings accurately.
In order to detect the operation fault of wind turbine in real-time and recognize its health status of the unit, a bearing health status recognition method based on vibration signal analysis using ITD (Intrinsic time-scale decomposition)-MSE (multiscale entropy)is proposed in this paper. The method is applied to ensure that the vibration signal is pretreated, and the time domain characteristics of the reconstructed signal are extracted, the ELM (Extreme learning machine) is then adopted to recognize the health status of wind turbine bearings. Firstly, the vibration signal of wind turbine bearings is decomposed using ITD to obtain a series of inherent rotation components. Then, MSE is calculated and used as a standard to select relevant components to reconstruct the signal. Afterwards, the reconstructed signals' RMS, kurtosis, crest factor and peak-to-peak value are calculated to input to the ELM model. Finally, the ELM model is established and the health status of wind turbine bearings can be recognized. The experimental results have shown that the proposed method is capable of recognizing the health status of wind turbine bearings accurately.
2018, 37(11): 1737-1743.
doi: 10.13433/j.cnki.1003-8728.20180117
Abstract:
The finite element simulation of the temperature distribution and the thermal deformation of the grinding wheel spindle bearing system is carried out with a certain type of horizontal grinding machine. Based on the theory of thermal characteristics of rolling bearing and the theory of heat transfer, ANSYS Workbench software is used to simulate the steady-state and transient temperature field of the spindle-bearing system. The variation law of the roller and the raceway temperature of the bearing roller and the inner and outer ring are obtained. Thermo-structural coupling analysis and temperature field simulation and the thermo-structural coupling analysis of the spindle-bearing system are carried out, and the variation law of thermal displacement and the thermal stress of the spindle in radial, tangential and axial directions are obtained. The results reveal the relationship between the temperature rise caused by thermal effects produced by bearing friction and the thermal deformation and thermal distortion of the spindle.
The finite element simulation of the temperature distribution and the thermal deformation of the grinding wheel spindle bearing system is carried out with a certain type of horizontal grinding machine. Based on the theory of thermal characteristics of rolling bearing and the theory of heat transfer, ANSYS Workbench software is used to simulate the steady-state and transient temperature field of the spindle-bearing system. The variation law of the roller and the raceway temperature of the bearing roller and the inner and outer ring are obtained. Thermo-structural coupling analysis and temperature field simulation and the thermo-structural coupling analysis of the spindle-bearing system are carried out, and the variation law of thermal displacement and the thermal stress of the spindle in radial, tangential and axial directions are obtained. The results reveal the relationship between the temperature rise caused by thermal effects produced by bearing friction and the thermal deformation and thermal distortion of the spindle.
2018, 37(11): 1744-1749.
doi: 10.13433/j.cnki.1003-8728.20180226
Abstract:
As one of important components in an inertial navigation system (INS), bracket's dynamic characteristics have a significant influence on INS. Taking the damping system of a certain type unmanned aerial Vehicle (UAV) as an example, the system parameters have been designed and process-matched according to the requirements of dynamic characteristics. Then, the topology optimization design has been carried on the bracket by using the variable density method. After optimization, the mass of the bracket has been reduced 19.9%, and the first order natural frequency of the damping system has been increased from 57.09 Hz to 58.76 Hz. Finally, the line vibration and angular vibration tests have been done on the inertial navigation damping system. The results show that the resonant frequency of the INS damping system optimized is 55 Hz, the maximum acceleration transmissibility is 2.2, -3 dB bandwidth is in the range of 30~40 Hz, and phase lag is 5.16°~9.17°, all of these can meet the design requirements, which represents that the INS damping system design and the bracket topology optimization method are valid.
As one of important components in an inertial navigation system (INS), bracket's dynamic characteristics have a significant influence on INS. Taking the damping system of a certain type unmanned aerial Vehicle (UAV) as an example, the system parameters have been designed and process-matched according to the requirements of dynamic characteristics. Then, the topology optimization design has been carried on the bracket by using the variable density method. After optimization, the mass of the bracket has been reduced 19.9%, and the first order natural frequency of the damping system has been increased from 57.09 Hz to 58.76 Hz. Finally, the line vibration and angular vibration tests have been done on the inertial navigation damping system. The results show that the resonant frequency of the INS damping system optimized is 55 Hz, the maximum acceleration transmissibility is 2.2, -3 dB bandwidth is in the range of 30~40 Hz, and phase lag is 5.16°~9.17°, all of these can meet the design requirements, which represents that the INS damping system design and the bracket topology optimization method are valid.
2018, 37(11): 1750-1754.
doi: 10.13433/j.cnki.1003-8728.20180131
Abstract:
Aiming at the deficiencies of facial features location and driver fatigue judgments in driving fatigue detection, a new method called supervised descend method was proposed to locate driver's face features simultaneously. Driver's eye blink frequency, yaw frequency and nodding frequency are extracted to build the fatigue detection sample database based on eye blink, yawn and nodding judgments, then a naive Bayesian classifier was constructed to judge the driver's fatigue state. If a driver appears fatigue state during driving, warning message would be given promptly to prevent traffic accidents. In the actual driving environment video test result, the average accuracy rate of the driver's fatigue detection achieved 94.87%, with good performances.
Aiming at the deficiencies of facial features location and driver fatigue judgments in driving fatigue detection, a new method called supervised descend method was proposed to locate driver's face features simultaneously. Driver's eye blink frequency, yaw frequency and nodding frequency are extracted to build the fatigue detection sample database based on eye blink, yawn and nodding judgments, then a naive Bayesian classifier was constructed to judge the driver's fatigue state. If a driver appears fatigue state during driving, warning message would be given promptly to prevent traffic accidents. In the actual driving environment video test result, the average accuracy rate of the driver's fatigue detection achieved 94.87%, with good performances.
2018, 37(11): 1755-1761.
doi: 10.13433/j.cnki.1003-8728.20180039
Abstract:
Reliability of rotor systems directly affects safe operation of the whole wind turbines. Therefore, it's necessary to establish reliability model reasonably and estimate its parameter accurately, to reflect the real reliability of rotor systems. Weibull distribution is widely used to reliability modeling in various fields. Support vector regression (SVR) maintaining the feature, suiting for small samples, the support vectors machine can be used to estimate reliability model parameters under small sample data. Based on rotor system fault data from a certain field since putting into operation, the reliability model of which is established, parameters of model are estimated by SVR, the estimating result is compared with that of traditional least square parameter estimation, and the final result indicates that the parameter estimation method based on SVR is more accurate, and more suitable to small sample data.
Reliability of rotor systems directly affects safe operation of the whole wind turbines. Therefore, it's necessary to establish reliability model reasonably and estimate its parameter accurately, to reflect the real reliability of rotor systems. Weibull distribution is widely used to reliability modeling in various fields. Support vector regression (SVR) maintaining the feature, suiting for small samples, the support vectors machine can be used to estimate reliability model parameters under small sample data. Based on rotor system fault data from a certain field since putting into operation, the reliability model of which is established, parameters of model are estimated by SVR, the estimating result is compared with that of traditional least square parameter estimation, and the final result indicates that the parameter estimation method based on SVR is more accurate, and more suitable to small sample data.
2018, 37(11): 1762-1767.
doi: 10.13433/j.cnki.1003-8728.20180128
Abstract:
The work aims to improve the service life of cutting tools by depositing nano-hard TiN/TiCN coatings on W18Cr4V substrate. With N2 and C2H2 as reaction gas, the high quality coatings were prepared on W18Cr4V substrate by taking advantage of reactive magnetron sputtering using optimal parameters. XRF, XRD, SEM were employed to investigate the structure, chemical composition and surface morphology of coatings. The micro-hardness and frictional wear properties were studied by using micro-hardness tester and pin disc friction and wear testing machine, respectively. The service life and thermal stability of the coatings were studied by cutting test. The results show that the coatings mainly composed of TiCxN1-x and TiN and the elements distribute relatively uniform, which the average grain sizes of coating were 35.65 nm and 32.12 nm. The hardness of the coatings isabove 3 300 HV. The abrasion resistance, cutting performance and thermal stability of the coating are high, the friction coefficient and wear loss are low, and the service life of the coated cutter is about 3 times that of the non-coated cutter.
The work aims to improve the service life of cutting tools by depositing nano-hard TiN/TiCN coatings on W18Cr4V substrate. With N2 and C2H2 as reaction gas, the high quality coatings were prepared on W18Cr4V substrate by taking advantage of reactive magnetron sputtering using optimal parameters. XRF, XRD, SEM were employed to investigate the structure, chemical composition and surface morphology of coatings. The micro-hardness and frictional wear properties were studied by using micro-hardness tester and pin disc friction and wear testing machine, respectively. The service life and thermal stability of the coatings were studied by cutting test. The results show that the coatings mainly composed of TiCxN1-x and TiN and the elements distribute relatively uniform, which the average grain sizes of coating were 35.65 nm and 32.12 nm. The hardness of the coatings isabove 3 300 HV. The abrasion resistance, cutting performance and thermal stability of the coating are high, the friction coefficient and wear loss are low, and the service life of the coated cutter is about 3 times that of the non-coated cutter.
2018, 37(11): 1768-1775.
doi: 10.13433/j.cnki.1003-8728.20180183
Abstract:
To address the disadvantage that subjective evaluation method lacks quantitative data support in styling assessment process, a styling evaluation method based on eye movement data was developed. This paper took the airplane seat as the research object, used the RED remote desktop type eye tracker of SMI company to collect 14 subjects' eye movement data during the evaluation process of 8 different airplane seats, and obtained the subjective ratings to eight airplane seats. A mathematical model about airplane seat styling evaluation based on support vector machine, which used five eye movement parameters as inputs, was established and verified. The result showed that it had higher accuracy, compared with neural network model. The research helps enterprise improve efficiency of airplane seats design and evaluation, and reduce cost and development time; it also benefits the airliners' seating type selection. In consideration of good accuracy of styling evaluation model, it is suitable for further popularization and application; it provides an efficient evaluation method for the product design evaluation.
To address the disadvantage that subjective evaluation method lacks quantitative data support in styling assessment process, a styling evaluation method based on eye movement data was developed. This paper took the airplane seat as the research object, used the RED remote desktop type eye tracker of SMI company to collect 14 subjects' eye movement data during the evaluation process of 8 different airplane seats, and obtained the subjective ratings to eight airplane seats. A mathematical model about airplane seat styling evaluation based on support vector machine, which used five eye movement parameters as inputs, was established and verified. The result showed that it had higher accuracy, compared with neural network model. The research helps enterprise improve efficiency of airplane seats design and evaluation, and reduce cost and development time; it also benefits the airliners' seating type selection. In consideration of good accuracy of styling evaluation model, it is suitable for further popularization and application; it provides an efficient evaluation method for the product design evaluation.
2018, 37(11): 1776-1782.
doi: 10.13433/j.cnki.1003-8728.20180227
Abstract:
The product scheme design, delivery of which relies greatly on the maturity management, is the main basis of product development. In the process of the methodology to model based system engineering (MBSE) in the scheme design to model, there is a lack of quantitative evaluation method for maturity, as far as the author is concerned. To strengthen the effective control of the scheme design, a maturity evaluation method with system engineering model was proposed in this paper. Based on the system engineering model in the scheme design, a system engineering model for maturity including establishment and iteration of maturity was established. The design elements are utilized in the maturity model, evaluating the completion rate of the design elements and the coverage rate of requirements, and the maturity of system engineering model in the scheme design is finally given by percentage form. The application in environment control system of spacecraft scheme design shows the effectiveness of the present method.
The product scheme design, delivery of which relies greatly on the maturity management, is the main basis of product development. In the process of the methodology to model based system engineering (MBSE) in the scheme design to model, there is a lack of quantitative evaluation method for maturity, as far as the author is concerned. To strengthen the effective control of the scheme design, a maturity evaluation method with system engineering model was proposed in this paper. Based on the system engineering model in the scheme design, a system engineering model for maturity including establishment and iteration of maturity was established. The design elements are utilized in the maturity model, evaluating the completion rate of the design elements and the coverage rate of requirements, and the maturity of system engineering model in the scheme design is finally given by percentage form. The application in environment control system of spacecraft scheme design shows the effectiveness of the present method.
2018, 37(11): 1783-1790.
doi: 10.13433/j.cnki.1003-8728.20180076
Abstract:
Rigid-flexible coupling dynamics models for taxi and brake analysis are established. In order to analyze the influence factors of brake torque on gear buffeting in this model, the control variable method is applied. Simulation analysis is carried out on this model by changing only one parameter at a time. The simulation results show obviously that:when the frequency of brake torque variation gets close to the resonance frequency, gear buffeting phenomenon is very intense. When the maximum value of the brake torque rises, the gear buffeting phenomenon becomes acute. If the magnitude of gear buffeting fluctuation rises, the range of gear buffeting amplitude is larger in response. Based on previous conclusions, the slip rate braking control strategy and deceleration control strategy are applied for anti-skid braking control respectively, the further research on gear buffeting phenomena under two control cases is conducted, and the response under two different ways of anti-skid braking control strategy are compared. The results show that:the slip rate braking control method with PID controller are much better than the braking control method of deceleration control type, it can improve main gear brake efficiency, slow down gear buffeting, and also improve landing safety.
Rigid-flexible coupling dynamics models for taxi and brake analysis are established. In order to analyze the influence factors of brake torque on gear buffeting in this model, the control variable method is applied. Simulation analysis is carried out on this model by changing only one parameter at a time. The simulation results show obviously that:when the frequency of brake torque variation gets close to the resonance frequency, gear buffeting phenomenon is very intense. When the maximum value of the brake torque rises, the gear buffeting phenomenon becomes acute. If the magnitude of gear buffeting fluctuation rises, the range of gear buffeting amplitude is larger in response. Based on previous conclusions, the slip rate braking control strategy and deceleration control strategy are applied for anti-skid braking control respectively, the further research on gear buffeting phenomena under two control cases is conducted, and the response under two different ways of anti-skid braking control strategy are compared. The results show that:the slip rate braking control method with PID controller are much better than the braking control method of deceleration control type, it can improve main gear brake efficiency, slow down gear buffeting, and also improve landing safety.
2018, 37(11): 1791-1798.
doi: 10.13433/j.cnki.1003-8728.20180129
Abstract:
After providing plank design criteria, the loads in yaw, lateral and longitudinal directions for initiating the shimmy were theoretically analyzed, considering the scaling effect, delaying effect, and form effect. Influence of the main parameters in plank design on initial loads was researched, such as installation angle, cross-section shape and size. Then, applying the multi body modeling and simulation method of landing gear with flexible body, confirmed excitation efficiency of nose landing gear with different installation angles in yaw, lateral and longitudinal directions, as well as tire loads and acceleration responses on axle, which were generated by the planks designed with different height and width. At last, the shimmy test results show that the three planks are safe and effective.
After providing plank design criteria, the loads in yaw, lateral and longitudinal directions for initiating the shimmy were theoretically analyzed, considering the scaling effect, delaying effect, and form effect. Influence of the main parameters in plank design on initial loads was researched, such as installation angle, cross-section shape and size. Then, applying the multi body modeling and simulation method of landing gear with flexible body, confirmed excitation efficiency of nose landing gear with different installation angles in yaw, lateral and longitudinal directions, as well as tire loads and acceleration responses on axle, which were generated by the planks designed with different height and width. At last, the shimmy test results show that the three planks are safe and effective.
2018, 37(11): 1799-1804.
doi: 10.13433/j.cnki.1003-8728.20180139
Abstract:
Circulation control flap system is an advanced flap system, which can improve the takeoff and landing performance and reduce the complexity of the system. A circulation control flap system with a flap deflection angle of 60° is used as geometric model, both the lifting characteristics of the circulation control flap system in different momentum coefficients and the control effect of the circulation control on the flow separation are studied through solving steady Reynolds-averaged Navier Stokes equations with Fluent software. The simulation results show that when the angle of attack is 0 and the momentum coefficient is 0.05, 1.7, 31.4; With the increase of the momentum coefficient, the circulation control flap system can control the flow separation behind the deflection flap effectively, accelerate the flow velocity on the upper surface of the airfoil under the influence of ejection effect, and increase the circulation of the airfoil, so that the lift coefficient of the airfoil is improved effectively.
Circulation control flap system is an advanced flap system, which can improve the takeoff and landing performance and reduce the complexity of the system. A circulation control flap system with a flap deflection angle of 60° is used as geometric model, both the lifting characteristics of the circulation control flap system in different momentum coefficients and the control effect of the circulation control on the flow separation are studied through solving steady Reynolds-averaged Navier Stokes equations with Fluent software. The simulation results show that when the angle of attack is 0 and the momentum coefficient is 0.05, 1.7, 31.4; With the increase of the momentum coefficient, the circulation control flap system can control the flow separation behind the deflection flap effectively, accelerate the flow velocity on the upper surface of the airfoil under the influence of ejection effect, and increase the circulation of the airfoil, so that the lift coefficient of the airfoil is improved effectively.
