光学阵列器件的慢刀伺服车削加工技术

慢刀伺服技术是相对于快刀伺服提出的方法.采用C轴、X轴、Z轴联动的方法在极坐标或圆柱坐标内进行加工.光学阵列如微透镜阵列、微反射镜阵列在高速数据、声音和视频信号传输中具有重要作用.将光学阵列看作一个自由曲面,使用慢刀伺服车削技术一次加工成形,可以解决传统加工中将光学阵列分块加工后拼装和调整的困难.但是由于光学阵列表面形状复杂,其表面法线的突变可能会使机床运动超出伺服轴执行能力.根据慢刀伺服加工技术的特点,建立了伺服轴执行能力限制曲线,研究了不同刀具半径补偿方式对加工的影响.实验结果表明,根据机床伺服轴执,厅能力合理选择刀具半径补偿方式可实现微光学阵列器件高精度加工.     

内表面间垂直度的高精度测量方法设计与误差分析

针对框体类零件超精密加工的难点问题--内表面问垂直度误差的高精度测量,提出了一种基于波面干涉技术测量的新方法,建立了垂直度测量系统,分析了各调整误差对测量结果的影响.该方法能够实现框体类零件内表面间垂直度误差的高精度测量与评价,并能得到误差的三维分布,测量结果可直接用于零件的确定性修形加工.实验表明,该方法可实现0.6"的综合测量精度.     

高超声速滑翔式飞行器再入轨迹多目标多约束优化

轨迹优化是高超声速滑翔式飞行器关键技术之一.为避免间接法求解轨迹优化问题时对初值敏感以及伪谱法求解轨迹优化问题中难以处理航路点和禁飞区等问题,提出采用基于Akima插值多项式的直接法求解高超声速滑翔式飞行器再入轨迹优化问题.以驻点热流密度最小和到达目标点时间最小为优化目标,考虑了终端约束、航路点约束、禁飞区约束、动压约束、过载约束等约束条件.仿真结果表明:采用的插值方法可以减少插值过程中的控制变量越界问题;得到的Pareto前沿具有良好的分布性,在初步设计时能够给设计者较大的选择余地;和文献中的单目标优化结果相比,本文所采用的算法也具有较好的寻优能力.     

Integrated guidance and control of guided projectile with multiple constraints based on fuzzy adaptive and dynamic surface

Based on fuzzy adaptive and dynamic surface (FADS), an integrated guidance and control (IGC) approach was proposed for large caliber naval gun guided projectile, which was robust to target maneuver, canard dynamic characteristics, and multiple constraints, such as impact angle, limited measurement of line of sight (LOS) angle rate and nonlinear saturation of canard deflection. Initially, a strict feedback cascade model of IGC in longitudinal plane was established, and extended state observer (ESO) was designed to estimate LOS angle rate and uncertain disturbances with unknown boundary inside and outside of system, including aerodynamic parameters perturbation, target maneuver and model errors. Secondly, aiming at zeroing LOS angle tracking error and LOS angle rate in finite time, a nonsingular terminal sliding mode (NTSM) was designed with adaptive exponential reaching law. Furthermore, combining with dynamic surface, which prevented the complex differential of virtual control laws, the fuzzy adaptive systems were designed to approximate observation errors of uncertain disturbances and to reduce chatter of control law. Finally, the adaptive Nussbaum gain function was introduced to compensate nonlinear saturation of canard deflection. The LOS angle tracking error and LOS angle rate were convergent in finite time and whole system states were uniform ultimately bounded, rigorously proven by Lyapunov stability theory. Hardware-in-the-loop simulation (HILS) and digital simulation experiments both showed FADS provided guided projectile with good guidance performance while striking targets with different maneuvering forms.     

Clustered coverage orienteering problem of unmanned surface vehicles for water sampling

This study investigates a clustered coverage orienteering problem (CCOP), which is a generalization of the classical orienteering problem. The problem is widely motivated by the emerging unmanned techniques (eg, unmanned surface vehicles and drones) applied to environmental monitoring. Specifically, the unmanned surface vehicles (USVs) are used to monitor reservoir water quality by collecting samples. In the CCOP, the water sampling sites (ie, the nodes) are grouped into clusters, and a minimum number of nodes must be visited in each cluster. With each node representing a certain coverage area of the water, the objective of the CCOP is to monitor as much as possible the total coverage area in one tour of the USV, considering that overlapping areas provide no additional information. An integer programming model is first formulated through a linearization procedure that captures the overlapping feature. A two-stage exact algorithm is proposed to obtain an optimal solution to the problem. The efficiency and effectiveness of the two-stage exact algorithm are demonstrated through experiments on randomly generated instances. The algorithm can effectively solve instances with up to 60 sampling sites.     

嵌入遗传算法的顺轨干涉SAR海表流场反演新方法

顺轨干涉SAR海表流场探测技术研究对于实现流场探测的全球化、精细化具有重要作用。为了提高海表流场迭代收敛速度和参数反演精度,依据校正系数的参数特点构建适应度函数的约束关系,将校正系数设计问题转化为仿真干涉相位与实测干涉相位差和雷达、平台参数约束条件下的比例因子选择问题,进而设计遗传算法计算校正系数的技术方法,并嵌入海表流场迭代反演算法,从而构建一种反演新方法。星载SAR数据仿真实验结果表明:海表流向反演的均方根误差优于10.0°,海表流速的均方根误差优于0.1 m/s,这符合海表流场反演精度要求。改进的海表流场反演算法可减少2~3次迭代,有效提高了反演效率。研究对于提高顺轨干涉SAR海表流场探测的实效性和准确性具有重要意义。     

考虑落角约束与驾驶仪特性的自适应径向基空间末制导律

为使舰炮制导炮弹在打击近岸机动目标的末制导段满足落角约束,考虑驾驶仪动态特性,基于自适应径向基逼近网络与动态面提出一种空间末制导律。构建弹目相对运动模型,通过带改进微分跟踪器的扩张状态观测器估计目标加速度。为零化视线角跟踪误差与角速率,采用自适应指数趋近律设计非奇异终端滑模,运用自适应径向基逼近网络削弱控制指令抖振。通过Lyapunov第二法证明了系统的视线角跟踪误差与视线角速率均最终一致有界。仿真实验表明:该末制导律使制导炮弹在空间中打击不同机动形式的近岸目标时,具备良好的末制导性能。     

Exact analysis of (R,s, S) inventory control systems with lost sales and zero lead time

We study an (R, s, S) inventory control policy with stochastic demand, lost sales, zero lead‐time and a target service level to be satisfied. The system is modeled as a discrete time Markov chain for which we present a novel approach to derive exact closed‐form solutions for the limiting distribution of the on‐hand inventory level at the end of a review period, given the reorder level (s) and order‐up‐to level (S). We then establish a relationship between the limiting distributions for adjacent values of the reorder point that is used in an efficient recursive algorithm to determine the optimal parameter values of the (R, s, S) replenishment policy. The algorithm is easy to implement and entails less effort than solving the steady‐state equations for the corresponding Markov model. Point‐of‐use hospital inventory systems share the essential characteristics of the inventory system we model, and a case study using real data from such a system shows that with our approach, optimal policies with significant savings in inventory management effort are easily obtained for a large family of items.     

石墨烯电声换能器的设计与对比

为了使石墨烯电声换能器获得最优性能,主要针对石墨烯热致发声器件和静电式发声器件进行了发声机理研究,通过理论建模和分析,得到了薄膜尺寸、厚度以及应力等结构参数对两种电声换能器的频率响应特性的影响规律。通过微纳加工制造方法设计和制备了一批不同结构参数下的电声换能器,并对这些器件进行了性能测试和对比分析,结果表明：薄膜厚度对热致电声换能器发声声压影响显著,即薄膜越薄,该电声换能器的发声声压越大;薄膜半径、厚度和应力对静电式电声换能器的频带影响较大,即薄膜半径越大,厚度越薄,应力越小,该电声换能器频带越宽。以上研究为优化选取石墨烯电声换能器的类型,优化设计结构参数,提升器件发声性能奠定了基础。     

修正的响应面方法优化螺栓法兰连接结构几何参数

采用响应面法对螺栓法兰连接进行优化设计时,考虑到经典响应面模型的局限性,在获得结构优化参数与响应指标内在联系的基础上,提出了修正响应面模型;设计了数值试验并对比了数值试验值与前述两种响应面模型预测值,结果表明修正响应面模型的预测值不仅误差相对比较均匀,且最大误差绝对值要明显小于经典响应面模型的相应值。采用遗传算法对修正响应面模型进行了以法兰质量最轻为优化目标的参数优化,取得了比较理想的优化结果。