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1.
The coaxial compound helicopter has two possible strategies for heading control: collective differential and rudder deflection. A flight dynamics model is developed to assess the effect of different heading control strategies. This includes the trim characteristics, steady flight performance,controllability, and manoeuvrability. The trim study demonstrates that heading control strategies are less influential on trim results, and the steady flight performance is also not significantly affected by the heading control strategy adopted. The controllability analysis shows although heading bandwidth and phase delay results at various speeds with different heading control strategies are all satisfied, the control derivative of the collective differential decreases as speed increases, and its heading aggressive agility is degraded into Level 3 in high-speed flight. In addition, using collective differential would lead to severe heading-rolling coupling as forward speed increases. On the contrary, the control derivative and aggressive agility of the rudder deflection is improved with forward speed, and there is no evidence of heading-rolling coupling. Finally, the transient turn MissionTask-Element(MTE) is utilized to investigate the heading manoeuvre characteristics in different heading control strategies, which indicates that the collective differential would add the amplitude of control input and the power consumption during this MTE. 相似文献
2.
针对可重复使用运载器(RLV)再入飞行强非线性、快时变特性和多种控制模式给姿态控制器设计带来的困难和挑战,提出了一种双环滑模反作用控制系统(RCS)/气动舵复合控制器设计方案。首先建立了RLV再入飞行的数学模型,基于时标分离原理,设计了快、慢双环回路控制系统,并采用滑模控制律(SMCL)获得控制力矩指令;所设计的RCS/气动舵复合控制器,由控制分配将控制力矩指令分别映射成RCS推力器执行的开关指令和气动舵面偏转指令,采用链式递增融合协调气动舵与RCS的复合控制。仿真结果表明,双环滑模RCS/气动舵复合控制器能较好地完成姿态跟踪控制,有效地节省RCS燃料,实现了气动舵面与RCS的协调控制。控制方案也能用于再入飞行器或空天飞机的控制系统设计。 相似文献
3.
A tubular moving-magnet linear oscillating motor (TMMLOM) has merits of high efficiency and excellent dynamic capability. To enhance the thrust performance, quasi-Halbach permanent magnet (PM) arrays are arranged on its mover in the application of a linear electro-hydrostatic actuator in more electric aircraft. The arrays are assembled by several individual segments, which lead to gaps between them inevitably. To investigate the effects of the gaps on the radial magnetic flux density and the machine thrust in this paper, an analytical model is built considering both axial and radial gaps. The model is validated by finite element simulations and experimental results. Distributions of the magnetic flux are described in condition of different sizes of radial and axial gaps. Besides, the output force is also discussed in normal and end windings. Finally, the model has demonstrated that both kinds of gaps have a negative effect on the thrust, and the linear motor is more sensitive to radial ones. 相似文献
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《中国航空学报》2020,33(1):324-338
Aircraft undergoing actuator failures into under-actuation have been seldom studied in literature. Aiming at addressing actuator failures of Total Loss of Effectiveness (TLOE) as well as Partial Loss of Effectiveness (PLOE) resulting in different system actuations, reconfigurable Fault-Tolerant Control (FTC) is proposed for supersonic wingless missiles under actuation redundancy. The under-actuated system of TLOE failure patterns is solved by transformation to cascade systems through a ‘shape variable’. Meanwhile, actuator TLOE faults of different unknown failure patterns from proper actuation to under-actuation are accommodated by a reconfigurable adaptive law on a multiple-model basis. The backstepping technique with the Extended State Observer (ESO) method adopted as a basic strategy is applied to an established symmetric coupled missile system with actuator PLOE faults, modeling errors, and external disturbances. Additionally, the nonlinear saturation characteristics of actuators are settled by an auxiliary system with the Nussbaum function technique. The stability of the control system is analyzed and proven through Lyapunov theory. Numerical simulations are implemented in the presences of aerodynamic uncertainties, gust disturbance, and actuator failures. Results demonstrate the effectiveness of the proposed method with satisfactory tracking performance and actuator fault tolerance capacity. 相似文献
6.
Mansour Kabganian Hamed Kouhi Morteza Shahravi Farhad Fani Saberi 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2018,61(9):2328-2343
The thrust vector control (TVC) scheme is a powerful method in spacecraft attitude control. Since the control of a small spacecraft is being studied here, a solid rocket motor (SRM) should be used instead of a liquid propellant motor. Among the TVC methods, gimbaled-TVC as an efficient method is employed in this paper. The spacecraft structure is composed of a body and a gimbaled-SRM where common attitude control systems such as reaction control system (RCS) and spin-stabilization are not presented. A nonlinear two-body model is considered for the characterization of the gimbaled-thruster spacecraft where, the only control input is provided by a gimbal actuator. The attitude of the spacecraft is affected by a large exogenous disturbance torque which is generated by a thrust vector misalignment from the center of mass (C.M). A linear control law is designed to stabilize the spacecraft attitude while rejecting the mentioned disturbance torque. A semi-analytical formulation of the region of attraction (RoA) is developed to ensure the local stability and fast convergence of the nonlinear closed-loop system. Simulation results of the 3D maneuvers are included to show the applicability of this method for use in a small spacecraft. 相似文献
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湍流控制屏(TCS)是航空发动机风扇噪声试验必备的试验设施。由于湍流控制屏的作用,风扇前传噪声向远场传播时会产生传递损失。通过对湍流控制屏的声学校准,可以获取湍流控制屏的声学修正量,从而实现对风扇前传噪声的修正。本文结合实际工程应用条件,分析了湍流控制屏重复安装的位置精度、校准声源重复性、稳定性、校准声源位置偏差、温湿度修正等因素对湍流控制屏声学修正量精度的影响;结合上述影响因素,对湍流控制屏160 Hz~40 kHz的声学修正量的特征进行分析,总结工程应用中湍流控制屏高精度声学校准的注意事项,提出湍流控制屏的声学校准应包含测量不确定度。 相似文献
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10.
波瓣穿透率对波瓣混合排气系统性能影响 总被引:9,自引:5,他引:4
基于Navier-Stokes方程组对某型涡扇发动机波瓣强迫混合排气系统进行了数值模拟,获得了波瓣长度以及扩张角分别不变时,不同穿透率模型的流场、涡量场的变化规律,揭示了通过不同方法改变穿透率对强迫排气系统混合性能的影响。模拟结果表明,在排气系统出口处,当瓣长一定时,热混合效率随穿透率的增加先增加而后逐渐趋于不变,当波瓣扩张角不变时,热混合效率随穿透率的增加而增加;总压恢复系数和推力系数随穿透率的增加均不断降低。 相似文献