This paper presents an actuator used for the trajectory correction fuze,which is subject to high impact loadings during launch.A simulation method is carried out to obtain the peak-peak stress value of each component,...This paper presents an actuator used for the trajectory correction fuze,which is subject to high impact loadings during launch.A simulation method is carried out to obtain the peak-peak stress value of each component,from which the ball bearings are possible failures according to the results.Subsequently,three schemes against impact loadings,full-element deep groove ball bearing and integrated raceway,needle roller thrust bearing assembly,and gaskets are utilized for redesigning the actuator to effectively reduce the bearings’stress.However,multi-objectives optimization still needs to be conducted for the gaskets to decrease the stress value further to the yield stress.Four gasket’s structure parameters and three bearings’peak-peak stress are served as the four optimization variables and three objectives,respectively.Optimized Latin hypercube design is used for generating sample points,and Kriging model selected according to estimation result can establish the relationship between the variables and objectives,representing the simulation which is time-consuming.Accordingly,two optimization algorithms work out the Pareto solutions,from which the best solutions are selected,and verified by the simulation to determine the gaskets optimized structure parameters.It can be concluded that the simulation and optimization method based on these components is effective and efficient.展开更多
In this work,synchronous cutting of concave and convex surfaces was achieved using the duplex helical method for the hypoid gear,and the problem of tooth surface error correction was studied.First,the mathematical mod...In this work,synchronous cutting of concave and convex surfaces was achieved using the duplex helical method for the hypoid gear,and the problem of tooth surface error correction was studied.First,the mathematical model of the hypoid gears machined by the duplex helical method was established.Second,the coordinates of discrete points on the tooth surface were obtained by measurement center,and the normal errors of the discrete points were calculated.Third,a tooth surface error correction model is established,and the tooth surface error was corrected using the Levenberg-Marquard algorithm with trust region strategy and least square method.Finally,grinding experiments were carried out on the machining parameters obtained by Levenberg-Marquard algorithm with trust region strategy,which had a better effect on tooth surface error correction than the least square method.After the tooth surface error is corrected,the maximum absolute error is reduced from 30.9μm before correction to 6.8μm,the root mean square of the concave error is reduced from 15.1 to 2.1μm,the root mean square of the convex error is reduced from 10.8 to 1.8μm,and the sum of squared errors of the concave and convex surfaces was reduced from 15471 to 358μm^(2).It is verified that the Levenberg-Marquard algorithm with trust region strategy has a good accuracy for the tooth surface error correction of hypoid gear machined by duplex helical method.展开更多
In conventional technical trajectory correction schemes,continuous attitude adjusting mechanisms, such as canards, are inferior in terms of response time and efficiency of executing instructions. Discontinuous attitud...In conventional technical trajectory correction schemes,continuous attitude adjusting mechanisms, such as canards, are inferior in terms of response time and efficiency of executing instructions. Discontinuous attitude adjusting mechanisms, such as the lateral pulse jet, have complex impact on the airflow layer of the projectile surface caused by the thrust vector jet flow. An improved two-dimensional trajectory correction mechanism is designed based on the principle of firing mass blocks by a tailor-made propellant. The mechanical properties of the thrust force(namely the correction force) is analyzed. The trajectory correction model is established to analyze the effects of correction starting moment and correction phase angle of a thrust force on the projectile's trajectory. According to the trajectory correction scheme, an improved genetic algorithm is employed to this work. The scheme is tested in the simulation. The results show that the correction scheme is effective to reduce target dispersion and increase the precision of the impact point.展开更多
Active set method and gradient projection method are curre nt ly the main approaches for linearly constrained convex programming. Interior-po int method is one of the most effective choices for linear programming. In ...Active set method and gradient projection method are curre nt ly the main approaches for linearly constrained convex programming. Interior-po int method is one of the most effective choices for linear programming. In the p aper a predictor-corrector interior-point algorithm for linearly constrained c onvex programming under the predictor-corrector motivation was proposed. In eac h iteration, the algorithm first performs a predictor-step to reduce the dualit y gap and then a corrector-step to keep the points close to the central traject ory. Computations in the algorithm only require that the initial iterate be nonn egative while feasibility or strict feasibility is not required. It is proved th at the algorithm is equivalent to a level-1 perturbed composite Newton method. Numerical experiments on twenty-six standard test problems are made. The result s show that the proposed algorithm is stable and robust.展开更多
海冰密集度是描述海冰特征的重要参数,准确获取海冰密集度对研究全球气候变化具有重要意义。针对北极夏季海冰密集度反演精度较低的问题,本文通过对微波辐射传输模型中的海冰发射率和初始海冰密集度进行优化估算,改善了微波辐射传输模...海冰密集度是描述海冰特征的重要参数,准确获取海冰密集度对研究全球气候变化具有重要意义。针对北极夏季海冰密集度反演精度较低的问题,本文通过对微波辐射传输模型中的海冰发射率和初始海冰密集度进行优化估算,改善了微波辐射传输模型对夏季观测亮温的大气校正效果,从而优化被动微波海冰密集度的反演结果,本研究采用2019年6—9月的FY-3D/MWRI亮温数据,分别利用优化前和优化后的ASI2算法(ASI2和ASI2E),结合固定系点(FTP)与动态系点(DTP),分别获得了4套夏季北极海冰密集度数据(ASI2-FTP、ASI2-DTP、ASI2E-FTP、ASI2E-DTP),并利用14景MODIS影像对结果进行了精度验证。研究结果表明,本研究提出的优化方法可有效提高北极夏季海冰密集度的反演精度,其中该优化方法对基于固定系点的反演改进尤为明显,其优化后的均方根误差(root mean square error,ERMSE)由21.9%减小到15.43%,偏差(bias,|B_(bias)|)由-12.40%下降到-6.01%。4种反演方法中,基于动态系点的算法优化后(ASI2E-DTP)表现尤为明显,其E_(RMSE)和B_(bias)分别为14.33%和-4.53%。展开更多
基金The authors would like to acknowledge National Defense Pre-Research Foundation of China(Grant No.41419030102)to provide fund for conducting experiments.
文摘This paper presents an actuator used for the trajectory correction fuze,which is subject to high impact loadings during launch.A simulation method is carried out to obtain the peak-peak stress value of each component,from which the ball bearings are possible failures according to the results.Subsequently,three schemes against impact loadings,full-element deep groove ball bearing and integrated raceway,needle roller thrust bearing assembly,and gaskets are utilized for redesigning the actuator to effectively reduce the bearings’stress.However,multi-objectives optimization still needs to be conducted for the gaskets to decrease the stress value further to the yield stress.Four gasket’s structure parameters and three bearings’peak-peak stress are served as the four optimization variables and three objectives,respectively.Optimized Latin hypercube design is used for generating sample points,and Kriging model selected according to estimation result can establish the relationship between the variables and objectives,representing the simulation which is time-consuming.Accordingly,two optimization algorithms work out the Pareto solutions,from which the best solutions are selected,and verified by the simulation to determine the gaskets optimized structure parameters.It can be concluded that the simulation and optimization method based on these components is effective and efficient.
基金Projects(52075552,51575533,51805555,11662004)supported by the National Natural Science Foundation of China。
文摘In this work,synchronous cutting of concave and convex surfaces was achieved using the duplex helical method for the hypoid gear,and the problem of tooth surface error correction was studied.First,the mathematical model of the hypoid gears machined by the duplex helical method was established.Second,the coordinates of discrete points on the tooth surface were obtained by measurement center,and the normal errors of the discrete points were calculated.Third,a tooth surface error correction model is established,and the tooth surface error was corrected using the Levenberg-Marquard algorithm with trust region strategy and least square method.Finally,grinding experiments were carried out on the machining parameters obtained by Levenberg-Marquard algorithm with trust region strategy,which had a better effect on tooth surface error correction than the least square method.After the tooth surface error is corrected,the maximum absolute error is reduced from 30.9μm before correction to 6.8μm,the root mean square of the concave error is reduced from 15.1 to 2.1μm,the root mean square of the convex error is reduced from 10.8 to 1.8μm,and the sum of squared errors of the concave and convex surfaces was reduced from 15471 to 358μm^(2).It is verified that the Levenberg-Marquard algorithm with trust region strategy has a good accuracy for the tooth surface error correction of hypoid gear machined by duplex helical method.
基金supported by the National Natural Science Foundation of China(11372142)
文摘In conventional technical trajectory correction schemes,continuous attitude adjusting mechanisms, such as canards, are inferior in terms of response time and efficiency of executing instructions. Discontinuous attitude adjusting mechanisms, such as the lateral pulse jet, have complex impact on the airflow layer of the projectile surface caused by the thrust vector jet flow. An improved two-dimensional trajectory correction mechanism is designed based on the principle of firing mass blocks by a tailor-made propellant. The mechanical properties of the thrust force(namely the correction force) is analyzed. The trajectory correction model is established to analyze the effects of correction starting moment and correction phase angle of a thrust force on the projectile's trajectory. According to the trajectory correction scheme, an improved genetic algorithm is employed to this work. The scheme is tested in the simulation. The results show that the correction scheme is effective to reduce target dispersion and increase the precision of the impact point.
文摘Active set method and gradient projection method are curre nt ly the main approaches for linearly constrained convex programming. Interior-po int method is one of the most effective choices for linear programming. In the p aper a predictor-corrector interior-point algorithm for linearly constrained c onvex programming under the predictor-corrector motivation was proposed. In eac h iteration, the algorithm first performs a predictor-step to reduce the dualit y gap and then a corrector-step to keep the points close to the central traject ory. Computations in the algorithm only require that the initial iterate be nonn egative while feasibility or strict feasibility is not required. It is proved th at the algorithm is equivalent to a level-1 perturbed composite Newton method. Numerical experiments on twenty-six standard test problems are made. The result s show that the proposed algorithm is stable and robust.
文摘海冰密集度是描述海冰特征的重要参数,准确获取海冰密集度对研究全球气候变化具有重要意义。针对北极夏季海冰密集度反演精度较低的问题,本文通过对微波辐射传输模型中的海冰发射率和初始海冰密集度进行优化估算,改善了微波辐射传输模型对夏季观测亮温的大气校正效果,从而优化被动微波海冰密集度的反演结果,本研究采用2019年6—9月的FY-3D/MWRI亮温数据,分别利用优化前和优化后的ASI2算法(ASI2和ASI2E),结合固定系点(FTP)与动态系点(DTP),分别获得了4套夏季北极海冰密集度数据(ASI2-FTP、ASI2-DTP、ASI2E-FTP、ASI2E-DTP),并利用14景MODIS影像对结果进行了精度验证。研究结果表明,本研究提出的优化方法可有效提高北极夏季海冰密集度的反演精度,其中该优化方法对基于固定系点的反演改进尤为明显,其优化后的均方根误差(root mean square error,ERMSE)由21.9%减小到15.43%,偏差(bias,|B_(bias)|)由-12.40%下降到-6.01%。4种反演方法中,基于动态系点的算法优化后(ASI2E-DTP)表现尤为明显,其E_(RMSE)和B_(bias)分别为14.33%和-4.53%。
