基于质心偏移的移动机器人轨迹跟踪控制

针对非完整约束下质心偏移的移动机器人,提出了一种改进滑模变结构的轨迹跟踪控制方法,并通过此方法得到一种具有全局渐近稳定性的跟踪控制器。以三轮移动机器人的运动模型为基础,该跟踪控制器的设计分为两部分:第一部分是采用X方向和前向角方向同时具有虚拟反馈变量,通过Lyapunov方法对控制系统进行稳定性分析,设计出切换函数;第二部分是滑模控制器设计,采用指数趋近律,使用S型指数函数代替符号函数,减少了滑模变结构控制的抖动,由此设计出了线速度和角速度的控制律,用来渐近整定移动机器人跟踪误差,实现了对参考轨迹的全局渐近跟踪。实验结果表明:该控制律能够在极短时间内趋于稳定,其跟踪平面坐标误差和前向角误差也能在极短时间内收敛于0,并且移动机器人也能够有效地跟踪期望轨迹,其控制效果具有明显的改善,且具有很好的抗干扰性能。     

稳恒磁场在金属相变过程中的应用

稳恒磁场在材料科学中的应用越来越受到关注。本文从稳恒磁场作用下生成的磁化力和洛伦兹力两个角度归纳了稳恒磁场对金属材料的固态相变和液态相变的影响。其中磁化力可以影响固态相变过程，形成取向．引起磁对流，进行磁性分离。而洛伦兹力可以抑制熔体的流动和波动，提高溶质离子在基体中的固溶度，另外，利用洛伦兹力还可以在电磁离心铸造中获得均匀的凝固组织。     

溪洛渡电厂18F机组启动试运行试验研究

总结了溪洛渡右岸18F机启动试运行试验。检验了厂家的保证值,划分了18F机在全负荷范围的稳定运行区域,并找出了各运行区域振动的主要频率。试验成果有助于溪洛渡东电机组及电网的安全运行。     

折板跌落式竖井设计约束条件研究

结合国内深层隧道排水工程-广州市东濠涌深层排水隧道,通过物理模型试验探讨了不同折板间距情况下折板竖井消能规律,并根据竖井中水流在折板间需满足的过流能力及充分消能的约束条件,研究了折板竖井消能的最大过流流量及稳定消能边界,提出了折板竖井设计应同时满足的约束条件以及折板通气孔的推荐位置。研究表明,在折板间距与折板宽度的比值小于0.408时,约束条件只有最大过流能力;当比值大于0.408时,只需考虑充分消能的约束条件。     

基于多传感器的四旋翼飞行器硬件系统设计

四旋翼飞行器由于其简单的机体结构与较为复杂的姿态控制,近年来在军用和民用领域广泛应用。旨在通过四旋翼飞行器飞控平台的搭建,实现对飞行器姿态的稳定控制。首先论述了四旋翼飞行器的飞行原理与机械结构,给出了硬件系统总体结构。在对各功能模块整合的基础上,实现基于多传感器的控制系统硬件电路设计。仿真与实验证明：多传感器使用过程中,通过卡尔曼滤波进行姿态数据的融合,有效地解决了加速度计、陀螺仪易受外界干扰问题,所设计硬件系统在飞行实验中性能稳定,为四旋翼的稳定控制提供了参考。     

Globally Stable Adaptive Tracking Control for Uncertain Strict‐Feedback Systems Based on Neural Network Approximation

This paper addresses the problem of globally stable adaptive neural tracking control for a class of strict‐feedback nonlinear systems. Compared with the existing works, the salient properties of the proposed scheme are given as follows. First, a novel switching controller is developed, which consists of a traditional adaptive neural controller and an extra robust controller to pull back the transient outside of the approximation domain. Second, only two adaptive parameters need to be tuned online, and the computational burden is considerably alleviated in practice. Third, to design the desired switching controller via the backstepping technique, a novel switching function, which has continuous derivatives up to the nth order, is constructed. It is shown that the system output converges to a small neighborhood of the reference signal and the closed‐loop system is globally stable. Finally, an example is provided to verify the effectiveness of the proposed control method.     

一种用于舰载无人机通信的天线伺服系统设计

为克服舰载设备使用稳定平台的可靠性问题,提出并设计了一种脱离稳定平台用于舰载无人机通信的天线伺服系统。该天线伺服系统用于舰艇对舰载无人机的实时跟踪,具有自动跟踪和手动跟踪两种工作模式,并且结构简单、工作稳定、响应速度快。从系统设计原理出发,阐述了系统的机电作动机构、角度跟踪算法、系统硬件电路设计以及伺服电机控制策略。实验表明,该伺服系统能够实时对舰载无人机进行精确跟踪,从而保障舰艇与无人机的有效通信。     

Fast local image inpainting based on the Allen–Cahn model

In this paper, we propose a fast local image inpainting algorithm based on the Allen–Cahn model. The proposed algorithm is applied only on the inpainting domain and has two features. The first feature is that the pixel values in the inpainting domain are obtained by curvature-driven diffusions and utilizing the image information from the outside of the inpainting region. The second feature is that the pixel values outside of the inpainting region are the same as those in the original input image since we do not compute the outside of the inpainting region. Thus the proposed method is computationally efficient. We split the governing equation into one linear equation and one nonlinear equation by using an operator splitting technique. The linear equation is discretized by using a fully implicit scheme and the nonlinear equation is solved analytically. We prove the unconditional stability of the proposed scheme. To demonstrate the robustness and accuracy of the proposed method, various numerical results on real and synthetic images are presented.     

Establishing spatial trends in water chemistry and stable isotopes (δ15N and δ13C) in the Elwha River prior to dam removal and salmon recolonization

Two high‐head dams on the Elwha River in Washington State (USA) have changed the migratory patterns of resident and anadromous fish, limiting Pacific salmon to the lower 7.9 km of a river that historically supported large Pacific salmon runs. To document the effects of the dams prior to their removal, we measured carbon and nitrogen stable isotope ratios of primary producers, benthic macroinvertebrates, and fish, and water chemistry above, between and below the dams. We found that δ¹⁵N was significantly higher in fish, stoneflies, black flies, periphyton and macroalgae where salmon still have access. Fish and chloroperlid stoneflies were enriched in δ¹³C, but the values were more variable than in δ¹⁵N. For some taxa, there were also differences between the two river sections that lack salmon, suggesting that factors other than marine‐derived nutrients are structuring longitudinal isotopic profiles. Consistent with trophic theory, macroalgae had the lowest δ¹⁵N, followed by periphyton, macroinvertebrates and fish, with a range of 6.9, 6.2 and 7.7‰ below, between, and above the dams, respectively. Water chemistry analyses confirmed earlier reports that the river is oligotrophic. Phosphorous levels in the Elwha were lower than those found in other regional rivers, with significant differences among regulated, unregulated and reference sections. The removal of these dams, among the largest of such projects ever attempted, is expected to facilitate the return of salmon and their marine‐derived nutrients (MDN) throughout the watershed, possibly altering the food web structure, nutrient levels and stable isotope values that we documented. Published in 2010 by John Wiley & Sons, Ltd.     

宽范围可调稳压电源的设计

介绍了一种以单片机为核心的智能化高精度直流稳压电源的设计,通过集成有A／D、D／A的单片机、三端稳压源、霍尔传感器和上位机组成闭环系统,实现高精度宽范围可调稳定电压的输出,特别适用于各种有较高精度要求的场合,该电源工作可靠,性能良好,现已成功用于某导弹遥测系统测试设备。