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《中国航空学报》2020,33(2):476-492
Rotor noise is one of the most important reasons for restricting helicopter development; hence, the optimization design of rotor blade considering aeroacoustic and aerodynamic performance at the same time has always been the focus of research attention. For complex rotor design problems with a large number of design variables, the efficiency of the traditional Kriging model needs to be improved. Thus, Hierarchical Kriging (HK) model is employed in this study for rotor optimization design. By using the validated RANS solver and acoustic method based on the FW–Hpds equation, an efficient aerodynamic/aeroacoustic optimization method for high-dimensional problem of rotors in hover based on HK model is developed. By using present HK model and new infill-sampling criteria, the number of design variables is increased from less than 20–53. Results of two analytical function test cases show that the HK model is efficient and accurate in calculation. Subsequently, the helicopter rotor blade is optimally designed for aerodynamic/aeroacoustic performance in hover based on the HK model with high dimensional design variables. The objective function is adopted to improve the rotational noise characteristics by reducing the absolute peak of the acoustic pressure. In addition, the constraints of thrust, hover efficiency, solidity, and airfoils thickness are strictly satisfied. Optimization results show that the Kriging model finds the objective of reducing the noise by 2.87 dB after 248 iterations while the HK model does it only after 164 iterations. The optimization efficiency of the HK model is significantly higher than that of the traditional Kriging model. In the case analyzed, the HK model saves 35% of the time used by the Kriging model. 相似文献
995.
推进器羽流的电磁矢量控制是基于电磁位形的改变使得喷射的羽流改变方向。为了原理性验证电推进羽流电磁矢量控制技术,针对螺旋波电推进器,开展了磁场位形调制仿真设计和试验验证。说明了电磁矢量调制线圈能够改变磁场位型,并且在试验过程中验证了等离子体羽流随磁场位型变化而产生的羽流方向偏转。在周期性磁场调制过程中,验证了等离子体密度参数随之周期性涨落。螺旋波电推进羽流方向最大偏转角度60°,可控偏转频率15Hz,说明了电推进羽流电磁矢量控制的可行性。 相似文献
996.
Jean-Charles MARE 《中国航空学报》2019,32(1)
This paper deals with the modelling and simulation of aircraft systems, in particular for power transmission and control. It is intended to review, propose and disseminate best practices for making model-based/simulation-aided engineering more efficient at any phase of the system life cycle. The proposals are aimed at creating value, not only by increasing the performance of the product under study but also by shortening the time to market, capitalizing knowledge, mitigating risks and facilitating concurrent engineering. The needs associated with the engineering activities are firstly identified to define a set of requirements for the models. Then, these requirements are used to drive the considerations leading to model development, focusing in particular on the process, modelled physical effects, modelling level, model architecting and concurrent engineering. The third part deals with the model implementation, giving special consideration to the different types of models, causalities, parameterization, implementation and verification. Each part is illustrated by examples related to safety critical actuators. 相似文献
997.
Bang-Zhao Zhou Xiao-Feng Liu Guo-Ping Cai Yun-Meng Liu Pan Liu 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2019,63(1):496-511
Capturing an uncontrolled space target is a tremendously challenging research topic. Target capture by a space robot can be well planned according to predicted motion of the target. In this paper, motion prediction of an uncontrolled space target is studied and a motion prediction algorithm is proposed. In the proposed algorithm, firstly a method for identifying the parameters of motion state and inertial property of the target is established; and then through substituting the identified parameters into the dynamic equations of the target, the motion of the target can be predicted as the solution of the equations. In the identification of the parameters, the unscented Kalman filter (UKF) is applied. In order to support the UKF, a method for estimating noise level of the observation data is developed, so our motion prediction algorithm is noise adaptive. A practical convergent criterion is also designed to determine the time when the estimated result of the UKF is accurate enough, such that the predicted motion is credible enough. After that, the accuracy of the prediction is further improved by an optimization method. In the end of this paper, numerical simulations are done to verify the validity of the proposed motion prediction algorithm. Simulation results indicate that the proposed algorithm is able to predict the motion of the target precisely. 相似文献
998.
《中国航空学报》2020,33(2):508-519
A Non-Intrusive Reduced-Order Model (NIROM) based on Proper Orthogonal Decomposition (POD) has been proposed for predicting the flow fields of transonic airfoils with geometry parameters. To provide a better reduced-order subspace to approximate the real flow field, a domain decomposition method has been used to separate the hard-to-predict regions from the full field and POD has been adopted in the regions individually. An Artificial Neural Network (ANN) has replaced the Radial Basis Function (RBF) to interpolate the coefficients of the POD modes, aiming at improving the approximation accuracy of the NIROM for non-samples. When predicting the flow fields of transonic airfoils, the proposed NIROM has demonstrated a high performance. 相似文献
999.
《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2020,65(3):909-932
This paper investigates bottomside thickness parameters at Digisonde stations over midlatitude and high latitude regions, and compares the diurnal, seasonal, and solar activity variations in 2014 and 2009. The geographic latitudes of high latitude considered in this work are located beyond ±60° and those of midlatitude are located between ±40° and ±60°. The IRI-modeled B0 with ABT-2009 option (B0_IRI) are also examined and compared with four kinds of the B0 values, i.e., the observed B0 (B0_obs) from GIRO, the computed B0 following to Jamjareegulgarn et al. (2017a) (B0_old), the calculated B0 with a correction factor regarding to Jamjareegulgarn et al. (2017b) (B0_new), and the B0 with an average correction factor (B0_new_c_av). The average correction factors are proposed additionally in this work so as to assist occasionally the experimental B0 nonexistence of Digisonde which are equal to 0.2658 and 0.2058 for midlatitudes and high latitudes, respectively. Results show that the diurnal variations of B0_new and B0_new_c_av are in a good agreement with those of B0_obs evidently compared with those of B0_IRI and B0_old at every station during the three seasons over high and middle latitudes. During the three seasons, the diurnal variations of B0_new_c_av show similar trends and are close to one another with the B0_obs and the B0_new with small deviations. The differences between the B0obs and the B0_new_c_av also show similar trends and are close to one another with those between the B0obs and the B0_new. In contrast, the B0_IRI with ABT-2009 option seems to predict the B0 values poorly during the three seasons at high latitudes and some seasons at midlatitudes. The proposed B0_new is useful for computing approximately the observed B0 and the ionogram-based total electron content (ITEC) of Digisonde, and the plasma scale height over midlatitudes and high latitudes. 相似文献
1000.
Qi Li Jianping Yuan Chong Sun 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2019,63(5):1541-1553
In this paper, the motion control problem of autonomous spacecraft rendezvous and docking with a tumbling target in the presence of unknown model parameters, external disturbances, actuator saturation and faults is investigated. Firstly, a nonlinear six degree-of-freedom dynamics model is established to describe the relative motion of the chaser spacecraft with respect to the tumbling target. Subsequently, a robust fault-tolerant saturated control strategy with no precise knowledge of model parameters and external disturbances is proposed by combining the sliding mode control technique with an adaptive methodology. Then, within the Lyapunov framework, it is proved that the designed robust fault-tolerant controller can guarantee the relative position and attitude errors converge into small regions containing the origin. Finally, numerical simulations are performed to demonstrate the effectiveness and robustness of the proposed control strategy. 相似文献