A unified formulation of optimal guidance-to-collision law for accelerating and decelerating targets

This paper provides a unified formulation of optimal guidance-to-collision law for a target with an arbitrary acceleration or deceleration. The collision course for general target acceleration or deceleration is first determined from the engagement geometry in conjunction with the nonlinear engagement kinematics in the proposed approach. The heading error defined in the collision course is then adopted as a variable to be nullified for accomplishing the intercept condition.The proposed guidance ...     

Analysis and design of a three-phase LCC-type resonant converter

A three-phase dc-to-dc LCC-type resonant converter with high-frequency transformer isolation is proposed. The operation and a simple analysis of the converter are presented. Design curves are obtained and a design example is given. SPICE simulation and experimental results are presented to verify the performance of the proposed converter for varying load conditions. The converter proposed has several advantages, e.g., operation in lagging PF mode for the entire load range, requires a narrow variation required in switching frequency, reduced component size and stresses, etc     

基于导波传播模型的MUSIC损伤识别算法

针对结构健康监测领域的损伤近场定位问题,提出了适用于复合材料结构损伤识别的近场二维多重信号分类（MUSIC）损伤识别算法。该损伤识别算法将导波传播模型引入近场二维MUSIC损伤识别模型,构造损伤散射信号与实验差信号的互相关矩阵,通过信号子空间与噪声子空间正交特性构造近场二维MUSIC空间谱。通过数值仿真和实验验证了所提出的损伤识别算法能够有效地识别复合材料结构损伤位置信息,具有很高的定位精度和分辨率。针对飞机垂直尾翼的加强筋结构对导波传播特性影响较大的问题,提出了分区域监测的损伤检测策略,并利用基于导波传播模型的二维MUSIC空间谱损伤识别算法成功地识别飞机垂直尾翼结构损伤,实现了复杂复合材料结构损伤识别的工程验证。     

航天器有限时间输出反馈姿态控制

研究在角速度不可测时航天器的有限时间姿态控制问题。基于有限时间控制技术,提出了由修正Rodrigues参数进行姿态描述的航天器输出反馈姿态控制算法。首先设计了单个航天器的输出反馈姿态控制器,在没有角速度反馈时也能够保证航天器姿态在有限时间内调节到期望姿态。之后,设计了无需绝对角速度和相对角速度信息的多航天器分布式输出反馈姿态控制器。使用Lyapunov理论和图论,对闭环系统全局有限时间稳定性进行了严格的证明。最后对提出的控制算法进行了数值仿真,其结果验证了所设计的航天器输出反馈控制算法的可行性和有效性。     

Novel sliding mode controller for synchronous motor drive

A novel sliding mode controller with an integral-operation switching surface is proposed. Furthermore, an adaptive sliding mode controller is investigated, in which a simple adaptive algorithm is utilized to estimate the bound of uncertainties. The position control for a permanent magnet (PM) synchronous servo motor drive using the proposed control strategies is illustrated. The theoretical analysis and the theorems for the proposed sliding mode controllers are described in detail. Simulation and experimental results show that the proposed controllers provide high-performance dynamic characteristics and are robust with regard to plant parameter variations and external load disturbance     

Space-time registration of radar and ESM using unscented Kalman filter

Space and time alignments are the prerequisites for the successful fusion of multiple sensors. A space-time registration model is proposed to estimate the system biases and to perform time synchronization together for mobile radar and electronic support measure (ESM) systems. A space-time registration model for radar and ESM is first developed, and an unscented Kalman filter (UKF) is proposed to estimate the space-time biases and target states simultaneously. The posterior Cramer-Rao bounds (PCRBs) are derived for the proposed UKF registration algorithm for ESM detection probability less than or equal to one. Theoretical analyses are performed to evaluate the accuracy and robustness of the proposed method. Computer simulations show that the UKF registration algorithm is indeed effective and robust for different radar and ESM tracking scenarios.     

A Digital Incremental Oscillator: Generation of Sinusoidal Waveform in DPCM

Based on the concept of incremental computations, a digital oscillator structure is proposed which consists of two incremental integrators and one incremental multiplier. Models for these elements are developed and detailed analyses are made showing that the errors of the proposed structure are extremely low compared with the direct-form one. The proposed oscillator structure can be implemented without a hardware multiplier and can generate sinusoidal waveforms in the differential pulse code modulation representation.     

Filtering of moving targets using SBIR sequential frames

In this paper three-dimensional (3-D) finite-impulse response (FIR) filters are proposed for moving target detection and tracking from multiframe space-based infrared (SBIR) data. An optimal, in the l_p sense, 3-D FIR filter design technique is proposed which is suitable for the above application. This technique is the first 3-D FIR design of its kind presented in the open literature. Directional, matched, and adaptive 3-D filtering techniques are proposed. Prior to the filtering, clutter mean estimation and mean subtraction are required. Real time implementation of directional and/or matched filters for processing maneuvering targets is discussed and filter design methods are proposed. Finally, performance comparisons of the proposed and other available 3-D FIR and infinite-impulse response (IIR) filters, on real SBIR data, are presented in which the advantages of the proposed 3-D filters are shown     

复合加载下加劲板疲劳裂纹扩展研究

本文以含倾斜裂纹平板和加劲板为实验模型,进行了平板和加劲板Ⅰ-Ⅱ复合型裂纹疲劳扩展实验。本文提出了复合型加劲板应力强度因子的工程算法,并利用S法和应变准则进行寿命估算,对扩展路径以及线切割预制和疲劳预制裂纹的异同进行了讨论。 实验与计算的结果表明,本文提出的复合型加劲板应力强度因子算法是一种较好的工程算法,应变准则应用于疲劳问题以估算寿命,其结果相当令人满意。     

混合线性/非线性模型的准高斯Rao-Blackwellized粒子滤波法

 针对混合线性/非线性模型,提出一种新的递推估计滤波算法,称为准高斯Rao-Blackwellized粒子滤波器（Q-GRBPF）。算法采用Rao-Blackwellized思想,将线性状态与非线性状态进行分离,对非线性状态运用准高斯粒子滤波（Q-GPF）算法进行估计,并将其后验分布近似为单个高斯分布,再利用非线性状态的估计值对线性状态进行卡尔曼滤波（KF）估计。将Q-GRBPF应用于目标跟踪的仿真结果表明,与Rao-Blackwellized粒子滤波器（RBPF）相比,Q-GRBPF在保证估计精度的前提下有效降低了计算复杂度,计算时间约为RBPF的58%;与Q-GPF相比,x坐标与y坐标的估计精度分别提升了45％和30％,而计算时间也节省了约30％。     

不对称推力完全自动补偿技术

研究了一种适用于多发飞机的不对称推力完全自动补偿策略,并针对发动机失效后的不对称推力飞行特性进行研究。首先,推导了横航向达到平衡状态的条件,提出了一种基于发动机转子转速信号的自动补偿控制方法,在保证补偿效果的同时,解决了自动补偿系统可靠性低的问题,该自动补偿控制方法将高压转子转速信号与低压转子转速信号进行逻辑运算,结合高压转子转速差控制副翼和方向舵偏转,再与主飞行控制系统共同作用使飞机达到平衡状态。然后,基于横航向主飞行控制系统具有滚转角保持功能的特点,优化自动补偿控制系统。最后,全包线内建立飞机达到平衡状态的线性化数学模型,设计了不对称推力完全自动补偿控制律。通过MATLAB/Simulink建模并进行仿真验证,仿真结果表明完全自动补偿控制方法对不对称推力飞行具有良好的补偿效果。     

增广拉格朗日子集模拟优化方法

传统的工程结构优化设计方法在求解多设计变量、多约束条件的结构优化设计问题时,存在诸多不足,针对上述问题,基于增广拉格朗日约束处理方法和子集模拟优化方法发展一种新的结构优化设计方法——增广拉格朗日子集模拟优化方法(ALSSO).该方法首先利用拉格朗日乘子法处理多重约束条件,然后利用子集模拟优化方法对转化后的无约束优化问题进行求解;对罚函数因子的更新方法进行改进,以保证收敛过程的稳定性;利用两个算例对该方法的计算精度、稳健性以及计算效率进行验证,并与其他优化方法进行对比.结果表明:增广拉格朗日子集模拟优化方法具有非常优秀的寻优性能.     

双轨火箭橇全时程动力学仿真分析研究

随着用于武器系统的新理论、新技术和新材料的发展,火箭橇的应用越来越广泛。本文针对双轨火箭橇系统,建立了橇轨-滑车系统的动力学分析模型。建立了橇车三维实体模型的简化与优化匹配方法,推导了考虑阻尼、橇轨间隙以及不平顺度的火箭橇运动动力学方程组并进行了求解。对于橇车动态特性计算问题、橇车设计与载荷预测,具有重要的理论与应用价值。     

双向比对高精度物理时间同步方法

提出一种面向未来卫星在轨应用的闭环物理高精度时间同步方法。比较了所提方法与其他时间同步方法的区别与优势，建立了远程系统时间同步基本模型与误差传递模型，基于双向测距和时间传递技术分析了高精度钟差获取原理，给出了时钟调整环路的时域频域参数依赖关系。完成了高精度时间同步地面试验系统构建，测试了开环非调钟状态下钟差测量精度误差、闭环调钟状态下时间同步准确度误差以及长时运行情况下的时间同步监测结果。测试结果表明，该方法能够实现优于1 ns量级的时间同步，为高精度时间同步技术研究提供了新的途径。     

多无人机协同覆盖路径规划

多无人机协同覆盖路径规划(CPP)由于其并行性和容错能力,对于提高无人机完成侦察、监视、搜索等任务的效率具有重要意义。提出了一种基于无人机任务性能评价和任务区域划分的多无人机协同CPP算法。定量分析了无人机执行覆盖任务的能力,根据无人机及携带成像传感器的性能给出了计算无人机任务性能指数的数学公式;提出了一种基于任务性能和子区域宽度的任务区域划分算法,使无人机的总转弯次数达到最少。仿真结果表明,所提出的CPP算法能够规划出全局最优的多无人机协同覆盖路径。     

一类非线性系统的反演变结构控制及应用

针对一类非线性系统 ,将其变换为易于设计变结构控制规律的规范型。利用小脑关节神经网络( CMAC)估计系统中的不确定函数 ,利用 CMAC神经网络和多面滑模技术估计出变换后系统的状态 ,最后利用变结构控制技术设计出控制器 ,特点是无需已知不确定性函数及其各阶导数的上界 ,与经典设计方法相比 ,所提出的方案允许非参数化不确定性。最后将此方法应用于空空弹控制系统的设计中 ,仿真结果表明了该方法的有效性     

Fault-tolerance wide voltage conversion gain DC/DC converter for more electric aircraft

In this paper, a fault-tolerance wide voltage conversion gain DC/DC converter for More Electric Aircraft (MEA) is proposed. The proposed converter consists of a basic Cuk converter module and n expandable units. By adjusting the operation state of the expandable units, the voltage conversion gain of the proposed converter could be regulated, which makes it available for wide voltage conversion applications. Especially, since mutual redundancy can be realized between the basic Cuk converter module and the expandable units, the converter can continuously work when an unpredictable fault occurs to the fault-tolerant parts of the proposed converter, which reflects the fault tolerance of the converter and significantly improves the reliability of the system. Moreover, the advantages of small input current ripple, automatic current sharing and low voltage stress are also integrated in this converter. The working principle and features of the proposed converter are mainly introduced, and an experimental prototype with 800 W output power has been manufactured to verify the practicability and availability of the proposed converter.     

Attitude control of a satellite with redundant thrusters

Redundant thrusters are generally used for a reliable attitude control system. Also, redundant thrusters yield a better performance if they are used appropriately. In this paper, the authors propose an efficient redundancy management algorithm to reduce the fuel consumption. The algorithm is based on a linear programming problem which is a constrained optimization problem. For the algorithm, a cost function is defined as a quantity related to the fuel consumption for a maneuver. The independent variables are the thrusters' on-times which are control input variables of a satellite dynamic model. The advantage of the proposed method is verified by numerical examples. The examples show that the proposed method consumes less fuel than an existing method for a given maneuvering command. A sub-optimal algorithm is also discussed for an onboard computation. The proposed algorithm is applied to two maneuvers: move-to-rest and rest-to-rest. This is verified by a numerical simulation.     

Higher-order vibration of thick composite and sandwich plates based on an alternative higher-order model

The transverse stretching vibration of thick sandwich plates, which is attributed to largely different stiffness at the adjacent layers, is a challenging issue, and efficient approach for such issue is less reported in the published literature. Thus, natural frequencies corresponding to stretching vibration modes are generally neglected in engineering design, which might impact structural safety as frequencies of the exciting force are close to transverse stretching vibration frequencies. This paper proposes an alternative higher-order model for dynamic analysis corresponding to the higher-order vibration modes. The proposed model is classified in the displacement-based equivalent single-layer theory, as the number of displacement parameters in the proposed model is independent of the layer number. The continuity of displacements and transverse shear stresses can be fulfilled at the interfaces between the adjacent layers of structures. To demonstrate the capability of the proposed model, typical examples are analyzed by utilizing the proposed model, the three-dimensional finite element method and the chosen higher-order models. By comparing with the exact three-dimensional elasticity solutions, it is found that the proposed model can yield more accurate natural frequencies corresponding to the higher-order displacement modes than the selected models. Moreover, the factors influencing reasonable prediction of the higher-order frequencies are investigated in detail, which can provide a reference for the accurate prediction of the higher-order frequencies.     

Adaptive controller design for a linear motor control system

Three different adaptive controllers for a permanent magnet linear synchronous motor (PMLSM) position-control system are proposed. The proposed controllers include: a backstepping adaptive controller, a self-tuning adaptive controller, and a model reference adaptive controller. The detailed systematic controller design procedures are discussed. A PC-based position control system is implemented. Several experimental results including transient responses, load disturbance responses, and tracking responses of square-wave, sinusoidal-wave, and triangular-wave commands are discussed and compared. The proposed system has a good robustness performance even though the inertia of the system is increased to 10 times. The experimental results validate the theoretical analysis.