三轴液压仿真转台灰箱辩识研究

三轴液压仿真转台由于伺服阀的非线性及框架间速度和力矩耦合特性使系统的模型非常复杂,常规的理论建模方法建立的数学模型与实际的系统相差较大,这使得鲁棒控制在液压转台中的应用受到一定限制.根据系统模型的结构特征和系统的实际特性对系统进行灰箱辩识是解决这一问题的最好办法.文中通过具体实例说明这种建模方法的有效性.     

三轴飞行模拟仿真转台的设计及控制问题研究

论述了三轴仿真转台的总体设计布局，驱动元件及控制方案等问题，分析了影响转台控制系统性能的因素并提出了相应的解决措施。最后，对转台最重要的指标之一低速问题进行了详细的探讨。     

三轴液压仿真转台三轴相交度测试方法

根据三轴仿真转台自身的结构特点,针对决定其精度的重要环节——相交度的测试问题,提出了新的简洁的测试方法,从而为三轴仿真转台的安装、调试提供可靠数据,以保证其精度指标达到设计要求。     

三轴飞行姿态仿真转台高性能指标及其实现

本文详细讨论了三轴飞行姿态仿真转台（三轴均由液压摆动马达驱动）的主要性能指标及影响它们的主要因素，在此基础上，给出了实现三轴飞行姿态仿真转台高性能指标的途径。同时，对三轴飞行姿态仿真转台中框架双液压马达同步驱动方案进行了探讨。     

OUT型闭式三轴转台的结构设计

本文介绍了ＯＵＴ型闭式三轴转台的结构型式，具体讨论了各轴系的轴承布置、精度计算等设计问题，并分析、总结了该三轴转台的结构特点。     

三轴仿真转台外框电液位置伺服系统自适应神经元网络控制

本文针对三轴飞行姿态仿真转台外框电液位置伺服系统的特点和技术要求，采用自适应神经元网络控制策略对其控制。仿真结果表明，自适应神经元网络控制以其特有的自学习、非线性等优点，完全满足三轴飞行姿态仿真转台外框电液伺服系统对控制策略的要求，由其构成的控制系统既具有良好的动态性能，又具有较强的鲁棒性与适应性。     

三轴转台框架的形状优化设计

本文叙述了三轴转台四种不同的布局型式。提出了用Ｂｅｚｉｅｒ曲线和Ｆｏｕｒｉｅｒ级数描述三轴转台框架的形状，将形状优化设计问题转换为可用参数优化设计方法求解的形式。建立了ＯＵＴ型三轴转台外框架结构的形状优化设计数学模型，然后给出了用增广乘子法对问题进行求解的步骤     

三轴运动模拟转台的结构对称性与动力学计算

本文给出了三轴运动模拟转台动力学相互作用的计算公式，并讨论了它的结构对称性问题。     

三轴模拟转台的外框结构有限元优化设计

本文建立了某三轴模拟转台的外框结构分析模型和结构优化设计模型，利用基于性态模型的约束变尺度法对其进行了优化设计，得出了在一阶固有频率和静态变形约束下的最优方案。     

带有轴间动力学解耦的三轴转台自适应控制

针对某型号转台存在的轴间非线性耦合，运用非线性解耦的方法进行了解耦设计，并基于解耦后的系统提出用超稳定性和正性的方法进行自适应模型跟随控制器设计，来解决系统在运行过程中参数发生变化对控制性能影响的问题。仿真结果表明，当系统参数在一定范围变化甚至被控对象模型阶次发生变化时，所设计的自适应模型跟随控制器仍能保证系统具有良好的控制性能。     

仿真转台伺服系统动态模型辨识与计算

仿真转台广泛应用于光电制导导引头及其对抗的仿真,对某型仿真转台进行高精度模型辨识可以有效提高系统的动态控制精度和设计效率。基于此,提出了一种转台伺服系统频率特性自动测试方法,根据测试数据采用参数递阶辨识方法分段拟合得到了被控对象的高精度传递函数模型。辨识结果与实测数据相比:在体现伺服系统重要特征的中低频段,幅度绝对误差1 d B,相位绝对误差2°;在高频段,得到了复杂的机械谐振环节特性,验证了被控对象传递函数模型的准确性。对于转台的动态精度计算,采用频率设计分析建模方法,结合被控对象高精度传递函数和实际校正环节模型得到了转台的动态精度计算模型,通过比较同一输入情况下实测动态误差与模型输出误差数据验证了模型准确性,结果表明了该方法的有效性。建立的动态精度计算模型能够反映实际系统的动态过程和动态误差变化规律,也为同类设备伺服系统的模型辨识和动态精度分析计算提供了方法。     

Wing kinematics measurement and aerodynamics of free-flight maneuvers in drone-flies

The time courses of wing and body kinematics of two free-flying drone-flies, as they performed saccades, were measured using 3D high-speed video, and the morpho- logical parameters of the wings and body of the insects were also measured. The measured wing kinematics was used in a Navier-Stokes solver to compute the aerodynamic forces and moments acting on the insects. The main results are as following. （1） The turn is mainly a 90° change of heading. It is made in about 10 wingbeats （about 55 ms）. It is of interest to note that the number of wingbeats taken to make the turn is approximately the same as and the turning time is only a little different from that of fruitflies measured recently by the same approach, even if the weight of the droneflies is more than 100 times larger than that of the fruitflies. The long axis of body is about 40° from the horizontal during the maneuver. （2） Although the body rotation is mainly about a vertical axis, a relatively large moment around the yaw axis （axis perpendicular to the long axis of body）, called as yaw moment, is mainly needed for the turn, because moment of inertial of the body about the yaw axis is much larger than that about the long axis. （3） The yaw moment is mainly pro- duced by changes in wing angles of attack： in a right turn, for example, the dronefly lets its right wing to have a rather large angle of attack in the downstroke （generally larger than 50°） and a small one in the upstroke to start the turn, and lets its left wing to do so to stop the turn, unlike the fruitflies who generate the yaw moment mainly by changes in the stroke plane and stroke amplitude.     

考虑颗粒间碰撞的气固两相流拉格朗日模拟

在均匀,稳定的各向同性气固两相紊流场颗粒弥散的拉格朗日模拟计算方法基础上,进一步考虑了流场中颗粒之间的碰撞对于模拟计算结果的影响。与Lavieville用大涡模拟所做的计算结果进行了对比,以对本方法进行验证,并考察了颗粒间的碰撞分别对流体相和颗粒相的影响。     

利用卡尔曼滤波和参数自调整控制器提高飞行仿真转台性能

为了提高惯性器件仿真的真实性,飞行仿真转台被广泛应用于半实物仿真系统.但是飞行仿真转台的响应误差、响应滞后、非线性等特性影响了整个半实物仿真系统的性能.采用卡尔曼滤波器对转台的状态进行估计,并设计了带有前馈的闭环控制器,减小了飞行仿真转台的低频相位滞后.通过对转动轴上的转动惯量进行辨识,控制器的参数可以自动调整来减小负载惯量变化对系统的影响,同时控制器对系统的力矩扰动进行了补偿.经过试验验证,转台小信号运行时的失真度残小为原来的1/5,动态仿真性能也有显著提高.     

Collaborative optimization of linear vibrating screen screening efficiency and dynamic response stability based on coupled DEM-MBK simulation

The dynamic response stability of the vibrating screen is an important factor affecting the screening effect and the structural performance of the vibrating screen. In this paper, to improve dynamic response stability and screening efficiency, we optimized the configuration of linear screening process parameters based on the co-optimization method with dual objectives via the virtual experiment. Firstly, a coupled DEM-MBK simulation model was established according to the dynamics of linear screen, and the dynamic response law of the screen machine under material impact was investigated. Secondly, the quantitative index of dynamic response stability according to the time-domain characteristics of the centroid amplitude was established. The trend and significance of three types of screening process parameters, including excitation, damping and structure, on the screening efficiency and dynamic response stability were analyzed through virtual orthogonal experiments. Finally, a parameter configuration scheme to achieve co-optimization was proposed based on the comprehensive balance method. The virtual experiment results show that the screening efficiency and dynamic response stability of the proposed scheme are improved by 3.28% and 49.07%, respectively, compared with the empirical parameter configuration. Obviously, the co-optimization method can maintain high screening efficiency and dynamic response stability at the same time, which is beneficial to improve the service life of the screen surface and screen body.     

Application of Modelica/MWorks on modeling,simulation and optimization for electro-hydraulic servo valve system

Electro-hydraulic servo valve is a typical complicated multi-domain system constituted by mechanical, electric, hydraulic and magnetic components, which is widely used in electro-hydraulic servo systems such as construction machinery, heavy equipment, weapon and so forth. The traditional method of modeling and simulation of servo valve is based on block diagram or signal flow, which cannot describe the servo valve system from components level nor be used in modeling and simulation of overall servo systems. In the procedure of traditional method, computational causality must be involved in modeling of servo valve, which is inconvenient to execute modification on components or parameters. Modelica is an object-oriented modeling language which is suited for large, complex, heterogeneous and multi-domain systems. The key features of Modelica are multi-domain, object-oriented and non-causal, which are suitable for modeling of servo valve and make the model readable, reusable, and easy to modify. The simulation results show similar curves with traditional method. This new servo valve modeling and simulation method can provide the engineers a more efficient way to design and optimize a servo valve and an overall servo system.     

Interfacial kinematics and governing mechanisms under the influence of high strain rate impact conditions: Numerical computations of experimental observations

This paper investigates the complex interfacial kinematics and governing mechanisms during high speed impact conditions. A robust numerical modelling technique using Eulerian simulations are used to explain the material response of the interface subjected to a high strain rate collision during a magnetic pulse welding. The capability of this model is demonstrated using the predictions of interfacial kinematics and revealing the governing mechanical behaviours. Numerical predictions of wave formation resulted with the upward or downward jetting and complex interfacial mixing governed by wake and vortex instabilities corroborate the experimental observations. Moreover, the prediction of the material ejection during the simulation explains the experimentally observed deposited particles outside the welded region. Formations of internal cavities along the interface is also closely resemble the resulted confined heating at the vicinity of the interface appeared from those wake and vortex instabilities. These results are key features of this simulation that also explains the potential mechanisms in the defects formation at the interface. These results indicate that the Eulerian computation not only has the advantage of predicting the governing mechanisms, but also it offers a non-destructive approach to identify the interfacial defects in an impact welded joint.     

Applications of scale-adaptive simulation technique based on one-equation turbulence model

A modified scale-adaptive simulation (SAS) technique based on the Spalart-Allmaras (SA) model is proposed. To clarify its capability in prediction of the complex turbulent flow, two typical cases are carried out, i.e., the subcritical flow past a circular cylinder and the transonic flow over a hemisphere cylinder. For comparison, the same cases are calculated by the detached-eddy simulation (DES), the delayed-detached eddy simulation (DDES), and the XY-SAS approaches. Some typical results including the mean pressure coefficient, velocity, and Reynolds stress profiles are obtained and compared with the experiments. Extensive calculations show that the proposed SAS technique can give better prediction of the massively separated flow and shock/turbulent-boundary-layer interaction than the DES and DDES methods. Furthermore, by the comparison of the XY-SAS model with the present SAS model, some improvements can be obtained.     

弹体贯穿钢筋混凝土数值模拟

详细描述了依据损伤原理建立的连续损伤模型,并对该模型进行了改进。在LS DYNA程序用户自定义材料模型中加入改进的连续损伤模型,并对弹体侵彻钢筋混凝土的穿孔过程进行了数值模拟,其结果与实验结果相吻合,模型可以用于钢筋混凝土的动态破坏预报。