基于ADAMS风洞柔壁喷管动力学仿真分析

基于刚柔耦合动力学理论,联合ADAMS和PATRAN/NASTRAN软件,对风洞柔壁喷管进行了动力学仿真,同时运用NASTRAN软件有限元分析了柔壁部件的非线性变形。比较两种计算结果发现,忽略柔壁变形的非线性,动力学仿真会存在较大误差。为此,采用分段线性化的方法,计入柔壁的非线性变形,改进柔壁喷管的动力学仿真模型。结果表明：改进后的动力学仿真准确度较高,可应用于柔壁喷管运动控制设计。最后,进一步分析了推杆驱动位移对柔壁结构强度的影响关系,为合理控制推杆驱动,确保柔壁无损伤提供必要的理论依据。     

几何非线性对整体壁板断裂参数的影响分析

基于有限元法和断裂力学理论,借助有限元软件ABAQUS计算了某整体壁板纵向裂纹的J积分。考虑了几何非线性,并与未考虑几何非线性所得结果进行了对比,对于不同的内压下以及不同蒙皮厚度情况下的结果进行了分析,结果表明几何非线性对机身壁板纵向裂纹裂尖J积分有明显的影响。     

电压变化时Boost PFC变换器的混沌和分叉现象

利用小信号模型对开关电源控制器进行设计过程中常出现混沌分叉等不稳定现象。以工程设计的角度,建立了平均电流型BoostPFC的精确电路模型,分析了系统中存在的非线性现象,结合非线性分叉和混沌理论对这类非线性现象进行了详细的分析和推导。     

On the selection of optimal global geopotential model for geoid modeling: A case study in Pakistan

A statistical comparison has been made between gravity field parameters derived from different global geopotential models (GGMs) and observed gravity anomalies, gravimetric geoid and GPS-Leveling data. The motivation behind this study is the selection of best possible global geopotential model that best matches statistically with the local observed data in Pakistan. This will facilitate in decreasing the load on observed data for the development of regional gravimetric geoid in remove-compute-restore technique when used in the Stokes’s integral for computation of the residual part. It is observed that combined geopotential models such as EGM96 and PGM200A, EIGEN-GL04C and EIGEN-CG03C reflect the better match in the total spectral range of gravity and GPS-Leveling data. Results of the precise local geoid model also indicate similar characteristics. A very-high-degree model “EGM2008” (degree/order 2160) exhibits relatively superior statistical fit with observed ground data in Pakistan region. For satellite-only models an increasing trend in the standard deviation can be seen with maximum of about ∼4 m in difference between GPS-Leveling and corresponding GGM’s geoid with increase in the order from 50 to 120 and then it decreases afterwards. However, for the EIGEN-CHAMP03SP, standard deviation saturates to a value of 3.4 m. This is an indication of contamination in the long to medium wavelength part, i.e. 50–100° for the satellite-only models. Moreover, the models DEOS-CHAMP-01C, GGM02C and then ITG-GRACE03 appear to have better fit for medium to long wavelength and can possibly be recommended for use as long wavelength part with the local observed data. While a hybrid geopotential model selection can be achieved through the selection from either of DEOS-CHAMP-01C, GGM02C, GGM02S, EIGEN-GRACE02S or ITG-GRACE03 in the long wavelength (to degree and order 40) and EGM96, PGM200A, EIGEN-GL04C, EIGEN-CG03C or even EGM2008 in medium to short wavelength, i.e. from degree 41 to maximum degree and order.     

求解流体力学反问题的数学方法及应用

流体力学反问题是一类重要的非线性问题，这类问题在工程中有广泛的应用，如过坝水流问题，给定流量的射流和翼型设计问题。由于这类流动求解区域不确定，导致问题的非线性特征，使数值计算十分困难，本文将以亚、跨声速翼型设计问题为例，提出了一种求解流体力学反问题的新方法。     

热和振动复合环境中人体热调节的数值模拟

本文针对热和振动复合环境对人体的影响特点，建立了该复合环境中二维人体热调节系统的数学模型．采用数值方法对人体热调节系统数学模型进行求解，计算了不同热和振动复合环境条件下人体温度分布及动态响应，计算结果与实验结果相符较好，相对误差小于５％．     

NONLINEAR DYNAMIC INVERSION CONTROL WITH ADAPTIVE COMPENSATION FOR FLIGHT CONTROL SYSTEM

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Super twisting controller for on-orbit servicing to non-cooperative target

A relative position and attitude coupled controller is proposed for rendezvous and docking between two docking ports located in different spacecraft. It is concerned with servicing to a tumbling non-cooperative target spacecraft in arbitrary orbit subjected to external disturbances.By considering both kinematic and dynamical coupled effects of relative rotation on relative translation, a coupled dynamic model is established to represent the relative motion of docking port on target spacecraft with respect to another on the service spacecraft. The spacecraft control is based on the second order sliding mode algorithm of super twisting(ST). It is schemed to manipulate the relative position and attitude synchronously. A formal proof of the finite time convergence property of the closed-loop system is derived theoretically by the second method of Lyapunov. Numerical simulations with the designed ST controller are presented to validate the analytic analysis by contrast with the twisting control algorithm. Simulation results demonstrate that the proposed relative position and attitude integrated controller is characterized by high precision, strong robustness and high reliability.     

基于视线制导的空间交会停靠控制方法

空间交会停靠段的控制经常采用的一种方法是基于视线位置信息的平行接近法.对纵向控制中的非线性滑动模态控制方法进行了研究和改进,考虑了视线角对纵向控制的耦合作用,增加了耦合项,并进行了存在性和稳定性分析.对于横向和纵向同时协调控制,提出一种多变量互相耦合的非线性滑动模态视线制导控制方法,并对同时协调控制进行了存在性和稳定性分析.