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781.
用可压方法及预处理方法求解了低马赫数紊流流动,其中空间离散格式采用了Roe格式,紊流模型采用了DES模型.以绕NACA0012的紊流流动为例,分析了该方法对提高流动速度和精度的特性,并将其用到多段翼型及绕圆柱的非定常流动中.数值模拟结果表明,该方法能有效求解低速流动及混合流场问题,且具有较高的数值精度. 相似文献
782.
大柔性飞机起落架缓冲器参数设计 总被引:9,自引:0,他引:9
为解决现行飞机起落架缓冲器设计不考虑机体柔性存在的问题,以大柔性飞机支柱型起落架油气式缓冲器为例,采用三质量块飞机着陆模型和功量预估分配法选择缓冲器参数,并对其进行着陆响应动力学分析。研究结果表明,机体一阶模态频率和起落架与机体连接点位置是影响机体储存着陆功量的两个主要因素:机体一阶模态频率小于2 H z时,机体储存的着陆功量预估公式计算误差小于5%;机体储存能量的耗散效率较低。 相似文献
783.
飞机垂直尾翼的气动特性直接关系到垂直尾翼尺寸和质量,通过流动控制方法提高垂直尾翼的升力可以进一步减小垂直尾翼尺寸,对减小结构质量具有实际意义。采用计算流体力学方法,对垂直尾翼的协同射流主动流动控制进行数值模拟;研究射流动量系数对连续协同射流的影响规律,以及射流动量系数、堵塞比、喷口数量等参数对离散协同射流的影响规律。结果表明:对于连续型协同射流,随着射流动量系数的增大,增升减阻和抑制分离的效果越显著;对于离散型协同射流,随着堵塞比的增加,增升效果逐渐下降,但功耗也同时下降;随着喷口数量的增多,增升效果先增大后减小,综合气动效率有所提升。 相似文献
784.
Yaen Xie Xiande Wu Takaya Inamori Zhen Shi Xinzhu Sun Hongtao Cui 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2019,63(3):1147-1160
This paper presents a trajectory planning algorithm for a space robot with dual-manipulators. Here one manipulator of the space robot captures a target, and another manipulator is free. In this case, this study uses one manipulator as the mission manipulator to capture the target, and another as the balance manipulator aiming at the compensation of the pose disturbance. For this method, a novel trajectory planning algorithm applied to the balance manipulator is presented. The trajectory planning problem is transformed into series of problems of the optimal state solution, and then the iterative algorithms for the trajectory planning are designed. In the iterative algorithms, the bias force on the spacecraft base caused by the balance manipulator is used as the compensation force. Then, to calculate the expected compensation force and torque, a pose control law for the spacecraft base is introduced. The expected compensation force and torque provide equality constraints for optimization problems, which implies that the trajectory planning algorithm compensates for not only the disturbance generated by the manipulator’s motion, but also environmental disturbances. This is because the expected compensation force and torque depend on the pose change of the spacecraft base rather than the type of the disturbance. Numerical simulation was carried out to analyze the proposed trajectory planning method. It was observed that the method greatly reduces the disturbance of Manipulator A on the spacecraft base. These results validated the effectiveness of the proposed method for the trajectory planning to make the spacecraft base disturbance up to minimum. 相似文献
786.
Robust H∞ controller design for attitude stabilization of flexible spacecraft with input constraints
Chuang Liu Keke Shi Zhaowei Sun 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2019,63(5):1498-1522
This paper addresses the attitude stabilization and vibration suppression problem for flexible spacecraft subject to model parameter uncertainty, controller perturbations, external disturbances and input constraints. The attitude model of flexible spacecraft is described and converted into a state space form in terms of passive and active vibration suppression schemes. A novel state feedback controller is proposed based on the exactly available expectation of a new variable, which is introduced to model a randomly occurring controller gain perturbation. Based on Lyapunov stability theory, sufficient conditions for the existence of the nonfragile H∞ controller considering input constraints are given based on linear matrix inequalities (LMIs) in terms of additive perturbation and multiplicative perturbation. Then, the developed controller subject to required constraints can be obtained, where the nonfragile property is fully considered to improve the tolerance to uncertainties in the controller. Numerical simulations are performed to demonstrate the effectiveness and superiority of the proposed control strategy in attitude stabilization and vibration suppression, where it should be noted that the passive vibration suppression scheme is superior for high natural frequencies while the active vibration suppression scheme is superior for low natural frequencies. Moreover, the low natural frequencies have more influence on the performance of attitude stabilization and vibration suppression. 相似文献
787.
To investigate the longitudinal motion stability of aircraft maneuvers conveniently, a new stability analysis approach is presented in this paper. Based on describing longitudinal aerodynamics at high angle-of-attack (a < 50 ) motion by polynomials, a union structure of two-order differential equation is suggested. By means of nonlinear theory and method, analytical and global bifurcation analyses of the polynomial differential systems are provided for the study of the nonlinear phenomena of high angle-of-attack flight. Applying the theories of bifurcations, many kinds of bifurcations, such as equilibrium, Hopf, homoclinic (heteroclinic) orbit and double limit cycle bifurcations are discussed and the existence conditions for these bifurcations as well as formulas for calculating bifurcation curves are derived. The bifurcation curves divide the parameter plane into several regions; moreover, the complete bifurcation diagrams and phase portraits in different regions are obtained. Finally, our conclusions are applied to analyzing the stability and bifurcations of a practical example of a high angle-of-attack flight as well as the effects of elevator deflection on the asymptotic stability regions of equilibrium. The model and analytical methods presented in this paper can be used to study the nonlinear flight dynamic of longitudinal stall at high angle of attack. 相似文献
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