倾转旋翼飞行器配平及仿真分析

倾转旋翼飞行器是一种特殊的飞行器,在操纵方式上既有直升机的旋翼操纵,又有定翼机的舵面操纵,在过渡段何时完全退出旋翼周期变距操纵是一个很有研究意义的问题.在进行仿真特性分析之前,首先需要对倾转旋翼飞行器过渡段进行数学建模,利用统一的数学模型对倾转旋翼飞行器过渡段进行描述.考虑倾转旋翼飞行器XV-15的复杂空气动力学,加入旋翼尾流对机翼、垂尾以及平尾的气动干扰,建立了该飞行器的数学模型.利用Maltab仿真软件搭建了XV-15的simulink仿真模型,分别对直升机模式、定翼机模式以及过渡模式进行了配平,并对配平结果进行了分析,分析了不同飞行模式下的操纵特性规律,并给出了何时完全退出旋翼周期变距操纵量的建议.     

直升机飞行动力学建模及可视化研究

研究了直升机飞行动力学建模及可视化仿真的相关技术。建模时综合考虑了直升机的主要气动力部件的建模以及气动干扰等问题。主旋翼是直升机建模的关键,详细讨论了与其相关的翼型气动力模型、诱导速度模型和挥舞运动模型的建模方法。同时利用虚拟现实技术构建了直升机三维实体模型。基于Simulink和虚拟现实工具箱,给出了将飞行动力学数值模型同虚拟场景结合起来的方法,实现了计算、仿真、显示一体化。最后采用算例直升机数据,进行了定直飞行的配平计算和操纵响应分析,结果证明了模型的合理性和有效性。     

三倾转旋翼无人机直升机模式建模与控制研究

针对一种新型三旋翼构型的倾转旋翼无人机的直升机模式控制问题进行研究,采用牛顿欧拉法对这种新型三旋翼构型的倾转旋翼无人机直升机模式进行了详细的动力学建模分析,建立了该无人机悬停模式6自由度非线性模型;在对该模型进行线性化的基础上,设计了这种三倾转旋翼无人机直升机模式下的高度、俯仰通道、滚转通道以及偏航通道的PID控制器,并在Matlab/Simlink环境下建立其仿真模型,对所设计的控制算法进行验证;实验结果表明,所设计的控制器能够满足系统的控制性能要求。     

某型舰载直升机飞行模拟器飞行仿真系统设计

对某型舰载直升机飞行模拟器飞行仿真系统进行了设计研究.给出了某型舰载直升机飞行模拟器飞行仿真系统的模型框架.定义了建模过程中所涉及的主要坐标系,研究与分析了与主旋翼相关的诱导速度、挥舞角、拉力、扭矩的计算方法,给出了舰载直升机部件气动建模思路.最后,结合舰载直升机数据,对直升机飞行模拟器飞行仿真系统对舰载机飞行员的操纵响应进行了仿真分析.设计的舰载直升机飞行模拟器飞行仿真系统已经成功应用到了某型舰载直升机飞行模拟器上,具有仿真度高、实时性好等特点,起到了良好的训练效果,得到了舰载直升机飞行教员和学员的认可.     

某型直升机飞行性能仿真建模与验证

主要研究并建立直升机飞行性能仿真模型,在直升机动力学和运动学微分方程的基础上重点解算作用在直升机各部件上的气动力和力矩模型,建立旋翼和尾桨的气动仿真模型,对旋翼挥舞运动进行了分析研究,还考虑了平尾、垂尾、机身和重力的仿真模型。最后通过对各飞行性能指标及其验证原理方法的分析研究,验证了静态性能指标,应用标量指标法验证动态性能指标。     

模拟加速方法的设计和验证

为在直升机旋翼气动性能数值模拟时简化建模过程、缩减计算时间,利用用户自定义函数（User Defined Function,UDF）设计混合模型盘激励模型和线激励模型,并对简单旋翼的悬停工况进行模拟.与风洞试验结果的对比表明：所设计的混合模型在简化旋翼模型的同时,能有效地计算旋翼的气动特性,模拟旋翼悬停时的流场,具有正确性和可行性;盘激励模型作为定常计算模型能够较快地计算得到旋翼的气动性能,缺点是不能体现每个桨叶对流场的单独作用;所设计的线激励模型在计算时由于所用的诱导速度为平均值,所以计算结果中旋翼效率比实际值偏高;通过与粒子图像测速（Particle Image Velocimetry,PIV）测量结果对比发现,线激励模型能较好地模拟出桨尖涡的分布.     

带后缘襟翼翼型的非定常气动特性数值仿真

研究直升飞机性能优化问题,旋翼系统是直升机振动的最主要来源.主动后缘襟翼控制技术可以在源头上抑制直升机的振动,准确预测与分析后缘襟翼-翼型的非定常气动特性是主动后缘襟翼设计的基础.在Fluent计算平台上采用Navier-Stokes方程,分析了在亚音速条件下,后缘襟翼的NACA0012翼型在襟翼与翼型均做俯仰振荡运动时的气动特性,对襟翼的偏角、襟翼与翼型之间的缝隙、以及马赫数等因素对翼型气动特性进行仿真.对结果进行比较,验证了计算的正确性,为后缘襟翼非定常气动力的分析提供了重要的依据.     

共轴刚性旋翼桨尖间距建模与参数影响研究

共轴刚性旋翼桨尖间距是涉及直升机飞行安全的关键问题,建立了共轴刚性旋翼综合气弹分析模型,开展了升力偏置、前进比、旋翼交叉角、提前操纵角以及高阶气动载荷等因素对桨尖间距影响的数值计算和分析研究.研究结果表明,升力偏置是影响桨尖间距最重要的因素,随着升力偏置量增大,桨尖间距呈线性减小趋势,而且旋翼拉力越大,趋势直线的斜率就越大,本质上桨尖间距是由桨根动态挥舞弯矩决定的,桨尖间距不会随飞行速度的增大而减小,旋翼交叉角对桨尖间距有一定的调节作用,提前操纵角和高阶气动载荷则对桨尖间距影响很小.     

基于Vega的直升机视景仿真技术研究与实现

以开发一套直升机飞行模拟仿真系统为目的,对仿真应用系统开发中各种常见的建模和驱动技术尤其是动态仪表面板仿真模块进行了研究,提出了可行的实现方案;利用建模工具Creator对飞机、仪表和大面积地形进行了可视化建模,利用DOF(Degrees OfFreedom)技术实现了直升机旋翼、尾翼以及仪表指针的动态交互;基于VC++集成开发环境,应用Vega API编程技术实现了直升机视景仿真应用系统的全部设计功能;直升机试飞实验证明,该视景系统取得了比传统视景系统更好的效果。     

旋翼复合材料桨叶参数化及有限元建模

直升机旋翼桨叶结构建模通常只考虑内部结构的几何特征,在进行优化设计时,没有考虑设计参数对初始静强度设计的影响,为优化设计,提出采用有限元离散方法,面向多数直升机采用的C型梁结构,将桨叶内部结构分为带设计控制点的三大类构型模块,建立了在设计过程中能够保证桨叶大梁设计强度不变的参数化模型,并有针对性的提出背景网格与层结构网格结合的快速有限元离散方法,生成高效的旋翼复合材料桨叶剖面参数化有限元模型.通过对“海豚”直升机桨叶剖面建模,验证参数化建模方法的可靠性和有效性.     

相交轴转子系统当量化建模与扭振响应分析

齿轮联结的相交轴转子系统具有转子不同体、不同速、不同轴线等结构特点,使其动力学建模异于常规转子系统,论文采用当量化建模方法,将相交轴转子系统转化为同转速、同轴线的转子系统并建立动力学模型,通过与已有研究对比验证了文中基于DyRoBeS当量化建模方法的有效性.以相交轴齿轮联结转子系统典型结构——某型直升机尾传动系统为研究对象,建立了当量化转子系统动力学模型,分析了系统各阶扭振临界转速及其组成、联结齿轮啮合刚度对扭振的影响、联结齿轮转动惯量对系统临界转速的影响,结果表明:传动系统第1、2阶临界转速为派生临界转速,其余8阶均源于各组成轴;中、尾减啮合刚度值与扭振的各阶共振峰值存在映射关系,部分啮合刚度值会激发共振极大值,应尽量避免;中、尾减啮合刚度变化会引发系统临界转速的变化,尤其是第1、2阶临界转速;不同阶临界转速对各个联结齿轮转动惯量的敏感性亦不同.论文从转子动力学角度研究了齿轮联结的相交轴转子系统的动力学特性,可为此类转子系统的结构优化设计及运行维护提供理论依据.     

On The Modeling of Twin Rotor MIMO System Using Chirp Inputs as Test Signals

This paper addresses the modeling problem for the twin rotor multi input multi output system. To develop experimental data, this popular commercial laboratory model of a helicopter from Feedback Instruments Ltd is excited with band limited chirp inputs. The conclusions drawn in this paper lead to four significant achievements: 1) derivation of a linear nominal model for Twin Rotor MIMO System, TRMS in short, from its equivalent nonlinear mathematical representation; 2) dynamic modeling of TRMS; 3) determination of non‐minimum phase dynamics; and 4) determination of linear operating region. The work considers systematic study of the system dynamics of TRMS and analytical treatment of its identified data leading to derivation of the RHP zero dynamics followed by pictorial illustrations indicating resonant modes associated with the plant. The method used in the present paper can be essentially used in modeling of 2 × 2 plants exhibiting non‐minimum phase dynamics and model uncertainties.     

涡轴发动机旋翼系统仿真建模研究

在直升机的仿真建模中,涡轮轴发动机模型的准确程度直接影响着动力系统模型的逼真程度,同时它也是直升机动力学建模的重要组成部分。为解决上述问题,研究了涡轮轴发动机建模方法,给出了考虑旋翼负载反馈的发动机控制系统模型,以及内、外环串联控制回路的发动机输出功率控制方式,设计了涡轮轴发动机动力调节的控制律,从而实现了涡轮轴发动机和旋翼一体化的直升机动力系统仿真模型,并通过仿真实例对模型进行验证,证实了模型的正确性。     

A New Nonlinear Controller for Trajectory Tracking of the Longitudinal Dynamics of a Small Scale Helicopter

A nonlinear control scheme is proposed for the trajectory tracking problem of a small scale helicopter’s longitudinal dynamics. The control scheme is based on a control design procedure that constructs static feedback regulators for nonlinear systems which are linearizable by dynamic feedback. Besides, the flatness characteristics of the helicopter’s longitudinal dynamics are used to design the desired trajectory. The controller proposed is based on the longitudinal model of the small scale helicopter including the main rotor and stabilizer bar dynamics. Sufficient conditions are given to guarantee asymptotic convergence to zero of the tracking error and to keep the main rotor thrust always negative assuming that all the helicopter’s parameters are known and that all helicopter’s states are measured. Numerical simulations are given to show the performance of the controller in the presence of the main rotor and stabilizer bar dynamics.     

Design and implementation of a hybrid fuzzy logic controller for a quadrotor VTOL vehicle

Helicopters have generated considerable interest in both the control community due to their complex dynamics, and in military community because of their advantages over regular aerial vehicles. In this paper, we present the modeling and control of a four rotor vertical take-off and landing (VTOL) unmanned air vehicle known as quadrotor aircraft. This model has been generated using Newton-Euler equations. In order to control the helicopter, classical PD (proportional derivative) and Hybrid Fuzzy PD controllers have been designed. Although fuzzy control of various dynamical systems has been presented in literature, application of this technology to quadrotor helicopter control is quite new. A quadrotor helicopter has nonlinear characteristics where classical control methods are not adequate especially when there are time delays, disturbances and nonlinear vehicle dynamics. On the other hand, Fuzzy control is nonlinear and it is thus suitable for nonlinear system control. Matlab Simulink has been used to test, analyze and compare the performance of the controllers in simulations. For the evaluation of the autonomous flight controllers, some experiments were also performed. For this purpose, an experimental test stand has been designed and manufactured. This study showed that although, both of the classical PD and the Fuzzy PD controllers can control the system properly, the Fuzzy PD controllers performed slightly better than the classical PD controllers, and have benefits such as better disturbance rejection, ease of building the controllers.     

From the Test Benches to the First Prototype of the muFly Micro Helicopter

The goal of the European project muFly is to build a fully autonomous micro helicopter, which is comparable to a small bird in size and mass. The rigorous size and mass constraints infer various problems related to energy efficiency, flight stability and overall system design. In this research, aerodynamics and flight dynamics are investigated experimentally to gather information for the design of the helicopter’s propulsion group and steering system. Several test benches are designed and built for these investigations. A coaxial rotor test bench is used to measure the thrust and drag torque of different rotor blade designs. The effects of cyclic pitching of the swash plate and the passive stabilizer bar are studied on a test bench measuring rotor forces and moments with a 6–axis force sensor. The gathered knowledge is used to design a first prototype of the muFly helicopter. The prototype is described in terms of rotor configuration, structure, actuator and sensor selection according to the project demands, and a first version of the helicopter is shown. As a safety measure for the flight tests and to analyze the helicopter dynamics, a 6DoF vehicle test bench for tethered helicopter flight is used.     

An improved nonlinear model for a helicopter and its self-repairing control with multiple faults via quantum information technique

In this paper, an improved nonlinear model for a 3-DOF helicopter and its self-repairing control scheme are investigated via quantum information technique. Firstly, adopting the mechanism analysis, a modified dynamic model is developed, in which the couplings among axes are considered. Such a modeling scheme is useful for applications when the accuracy of original model can not be satisfied. Then, a reconfigurable control scheme is designed for the twin rotor helicopter with multiple faults and parametric uncertainties, which combines active disturbance rejection control method with model reference adaptive control method. In addition, quantum information technique is used to increase the accuracy of self-repairing control of helicopter. Finally, simulation verification is presented in both aspects of modeling and control. The effectiveness and feasibility of the proposed scheme are verified by comparative simulations.     

Diagnosis using a first-order stochastic language that learns

We have created a diagnostic/prognostic software tool for the analysis of complex systems, such as monitoring the “running health” of helicopter rotor systems. Although our software is not yet deployed for real-time in-flight diagnosis, we have successfully analyzed the data sets of actual helicopter rotor failures supplied to us by the US Navy. In this paper, we discuss both critical techniques supporting the design of our stochastic diagnostic system as well as issues related to its full deployment. We also present four examples of its use.Our diagnostic system, called DBAYES, is composed of a logic-based, first-order, and Turing-complete set of software tools for stochastic modeling. We use this language for modeling time-series data supplied by sensors on mechanical systems. The inference scheme for these software tools is based on a variant of Pearl’s loopy belief propagation algorithm [Pearl, P. (1988). Probabilistic reasoning in intelligent systems: Networks of plausible inference. San Francisco, CA: Morgan Kaufmann]. Our language contains variables that can capture general classes of situations, events, and relationships. A Turing-complete language is able to reason about potentially infinite classes and situations, similar to the analysis of dynamic Bayesian networks. Since the inference algorithm is based on a variant of loopy belief propagation, the language includes expectation maximization type learning of parameters in the modeled domain. In this paper we briefly present the theoretical foundations for our first-order stochastic language and then demonstrate time-series modeling and learning in the context of fault diagnosis.