柔性多体系统动力学在直升机旋翼桨叶上的应用

提出了一种全新的计算旋翼桨叶动力响应的方法。以柔性多体系统动力学为基础，结合有限单元法和拉格朗日方程，推导出绕动轴转动的多柔体动力学质量矩阵，建立了直升机旋翼桨叶的动力学控制方程及其系数矩阵的解析表达式，采用Rung-Kutta法进行数值积分．分析了挥舞运动在强耦合状态下的运动规律。仿真结果表明采用此方法建立旋翼桨叶的动力学控制方程。可以更真实的反映桨叶的实际运动状态。     

直升机旋翼锥体与动平衡主动调节技术

针对直升机桨叶质量、气动条件等不平衡引起的旋翼低频振动过大的问题,提出一种以旋翼锥体为约束、仅通过调整桨叶变距拉杆的主动减振技术.该技术在建立的桨叶挥舞摆振扭转耦合的动力学模型基础上,使用最小二乘辨识方法估计振动频域分量和变距拉杆位移之间的线性模型,从而构造并求解以旋翼锥体为约束条件、低频振动分量为控制目标的二次型性能指标函数,同时将该算法用Simulink模块实现,进行实时化仿真计算,并验证控制结果的有效性.结果表明：该算法约束旋翼锥体的同时能够降低旋翼80%以上的低频振动,而且对桨毂中心升力、扭矩等的影响在0.3%以内,并未对直升机其他动力响应产生不良影响,结合Simulink模型的实时化仿真为直升机锥体和动平衡调整提供了一种工程应用思路.     

基于微多普勒分析的直升机旋翼参数估计

针对直升机的分类和识别问题,提出一种利用微多普勒特征估计直升机旋翼参数的方法。建立单频信号下直升机旋翼微动模型和回波模型,定量分析直升机旋翼的微多普勒调制特征,及其与旋翼旋转速度、旋翼叶片长度和旋翼叶片片数之间的关系,利用平滑伪Wigner-Vill分布和图像处理相结合的方法提取微多普勒调制特征,估计直升机旋翼的相关微动参数。仿真结果证明了该方法的有效性。     

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。     

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.     

Mathematical Modeling and Experimental Identification of an Unmanned Helicopter Robot with Flybar Dynamics

This paper presents a mathematical model for a model‐scale unmanned helicopter robot, with emphasis on the dynamics of the flybar. The interaction between the flybar and the main rotor blade is explained in detail; it is shown how the flapping of the flybar increases the stability of the helicopter robot as well as assists in its actuation. The model helicopter has a fast time‐domain response due to its small size, and is inherently unstable. Therefore, most commercially available model helicopters use the flybar to augment stability and make it easier for a pilot to fly. Working from first principles and basic aerodynamics, the equations of motion for full six degree‐of‐freedom with flybar‐degree of freedom are derived. System identification experiments and results are presented to verify the mathematical model structure and to identify model parameters such as inertias and aerodynamic constants. © 2004 Wiley Periodicals, Inc.     

Surrogate based optimization of helicopter rotor blades for vibration reduction in forward flight

The effectiveness of surrogate modeling of helicopter vibrations, and the use of the surrogates for minimization of helicopter rotor vibrations are studied. The accuracies of kriging, radial basis function interpolation, and polynomial regression surrogates are compared. In addition, the surrogates are used to generate an objective function which is employed in an optimization study. The design variables consist of the cross-sectional dimensions of the structural member of the blade and non-structural masses. The optimized blade is compared with a baseline rotor blade which resembles an MBB BO-105 blade. Results indicate that: (a) kriging surrogates best approximate vibratory hub loads over the entire design space and (b) the surrogates can be used effectively in helicopter rotor vibration reduction studies.     

基于双目视觉的直升机旋翼桨叶挥舞角测量

为实现直升机旋翼桨叶挥舞角的测量,提出了一种基于双目视觉的测量方法.首先,在直升机旋翼桨叶上均匀布置编码标记点,用已标定的双目摄像机对旋翼桨叶每隔一定角度采集标记点图像;其次,对左右摄像机图像上的标记点进行解码和匹配,得到标记点的左右图像视差,进而计算标记点三维坐标;再次,利用标记点在各个角度下的三维坐标,计算旋翼中心和转轴方向,建立旋翼坐标系;最后,在旋翼坐标系下,根据标记点静止与高速旋转时在同一角度下的三维坐标,计算挥舞角大小.利用风扇叶片进行仿真试验,结果验证了该方法具有自动化程度高和测量精度高的特点,可满足直升机旋翼桨叶挥舞角测量的要求.     

三种直升机旋翼共锥度测量新方法

直升机旋翼共锥度是旋翼动平衡测量的一个重要参数;它直接影响直升机机动性能、安全性能等多方面重要指标;针对在旋翼高速旋转的状态下测量共锥度值的系统特点,介绍了3种基于摄像机成像的直升机旋翼共锥度测量新方法,利用摄像机采集光源在桨叶上的成像信息,对图像进行处理、计算,从而得到直升机旋翼的共锥度值;对每种方法的基本结构、计算方法进行了较详细的介绍,该方法结构简单,安装方便,可实现对直升机旋翼共锥度值较高精度的测量,具有较高的实用价值.     

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.     

Experimental validation of the utility of structural optimization

This paper addresses the topic of validating structural optimization methods by use of experimental results. The paper describes the need for validating the methods as a way of effecting a greater and an accelerated acceptance of formal optimization methods by practicing engineering designers. The range of validation strategies is defined which includes comparison of optimization results with more traditional design approaches, establishing the accuracy of analyses used, and finally experimental validation of the optimization results. The remainder of the paper describes examples of the use of experimental results to validate optimization techniques. The examples include experimental validation of the following: optimum design of a trussed beam; combined control-structure design of a cable-supported beam simulating an actively controlled space structure; minimum weight design of a beam with frequency constraints; minimization of the vibration response of helicopter rotor blade; minimum weight design of a turbine blade disk; aeroelastic optimization of an aircraft vertical fin; airfoil shape optimization for drag minimization; optimization of the shape of a hole in a plate for stress minimization; optimization to minimize beam dynamic response; and structural optimization of a low vibration helicopter rotor.     

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.     

直升机桨叶动平衡试验技术研究

通过研究直升机桨叶动平衡试验技术,重点分析了采用基准桨叶校准试验台、标准桨叶和伴随桨叶,以及采用标准桨叶和伴随桨叶校验批生产桨叶的几个关键步骤和技术途径,统一了部分术语和定义,整理了相关参数的计算公式,是对直升机桨叶动平衡试验技术的一次消化和总结,对于深入研究基准桨叶校准方法具有非常重要的意义,同时也为开展新型号直升机的桨叶动平衡试验打下了基础.     

基于模态参数及小波变换的旋转梁结构损伤识别

本文采用旋转悬臂梁模型模拟旋翼直升机桨叶结构,并对其开展损伤识别问题研究.首先,基于有限元方法,采用Hamilton变分原理,建立旋转结构的动力学模型,通过对比理论和实验的结果验证模型的正确性.其次,利用不同模态参数(位移模态、应变模态)对旋转悬臂梁结构进行损伤识别研究.最后,针对位移模态,基于小波变换的奇异性分析特性,研究通过小波系数辅助损伤识别的方法.计算结果表明,对于旋转结构,应变模态的损伤识别效果较好,而位移模态若结合小波变换的奇异性分析,同样可以实现较为准确的损伤识别效果.     

The stochastic aeroelastic response analysis of helicopter rotors using deep and shallow machine learning

Neural Computing and Applications - This paper addresses the influence of manufacturing variability of a helicopter rotor blade on its aeroelastic responses. An aeroelastic analysis using finite...     

Computational simulation and analysis of double-swept blade in BVI noise reduction

The TURNS computational fluid dynamics (CFD) code with the Beddoes prescribed wake and the WOPWOP computational acoustics code is used to study blade-sweep blade–vortex interaction (BVI) noise reduction design. The CFD three-dimensional unsteady solutions of blade surface pressure distributions are used as the input to WOPWOP acoustics computational code to produce the overall sound pressure level (OASPL) on a 3-rotor radiation observer hemisphere around the helicopter rotor. To study the effects of blade sweep on BVI noise reduction, computations are performed on a baseline rectangular blade and a corresponding double-swept blade to better understand the impact of blade sweep on BVI noise reduction in relation to the interaction angle between blade leading edge and the shed tip-vortex. The present study indicates that tip-region blade forward sweep produces favorable BVI angles for dominate BVIs to reduce the maximum BVI noise level on the advancing side, while increasing noise level on the retreating side. Increasing in the noise level on the retreating side as a trade-off for decreasing in the maximum noise level on the advancing side results favorably in the reduction of the overall maximum noise level and in changing the ‘hot’ noise spots into a more desirable ‘less hot’ noise region.     

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。     

基于PCNN的桨叶图像提取及锥度测量

针对目前对直升机桨叶共锥度测量难度大、精度低、无法对桨叶逐点测量的缺点,提出了一种应用视觉系统测量旋翼共锥度的新方法,给出了系统的总体安装方案并对系统的成像误差精度进行了分析,由于旋翼桨叶处于高速旋转状态需要实时处理的特点,提出了一种基于脉冲藕合神经网络(PCNN)的分割方法,在设计好的旋翼桨叶模型上进行了相关实验,通过与其它分割算法的对比,验证了算法的具有很高的识别率;实验结果表明:基于PCNN的分割方法具有较高的精度,适用于实时的旋翼锥度测量系统.     

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.     

Experimental Analysis of Variable Collective-pitch Rotor Systems for Multirotor Helicopter Applications

This paper presents an experimental study of variable collective-pitch rotor systems for multirotor helicopter applications. An experimental research facility has been established to conduct this research. The facility enables the high-resolution measurement of forces and torques produced by rotor systems. The power consumption of the rotor system during experimentation can also be recorded. The experimental research facility also allows for the characterisation of the effect of rotor systems on multirotor helicopter performance. It is shown that the variable collective-pitch rotors have a significant performance advantage over fixed-pitch rotors when comparing thrust response, and multirotor helicopter step input response performance. Further, it is observed that variable collective-pitch rotors are more efficient in terms of energy consumption than comparable fixed-pitch rotors under similar operating conditions.