用于阵形控制的无人机编队飞行仿真平台设计与实现

设计了一种模块化结构的无人机编队飞行仿真实验平台.根据阵形控制的模拟需求,将仿真平台进行功能化模块构建,并通过内集方式予以集成.仿真平台结合时序驱动机制、虚拟现实技术、记录与回放技术以及数据分析与重栽软件,使得仿真数据具有时序性、可视性、可记录及重绘性,,操作人员具有高度的参与性,各模拟模块可以根据不同的研究成果进行更改、升级和替代.经过多次仿真实验,该仿真平台运行稳定可靠、占用系统资源小,为无人机编队飞行的研究提供了预验证性的工具,为今后的仿真系统设计提供了一个参考.

多移动机器人主—从编队控制研究

多机器人编队控制是多移动机器人自主协调控制领域中的关键技术。这篇论文在基于局部测量和局部控制的框架下，研究具有主—从跟踪结构的移动机器人编队系统的建模和控制问题。论文的主要研究内容可分为如下三个方面：针对一阶运动学和二阶运动学模型的编队控制器设计；将基于运动学的编队控制器与基于从机器人动力学的载体控制器相结合；将队形反馈信息融入主机器人的轨迹跟踪控制器，给出了主机器人的协调编队控制器的设计。具体内容可概括为如下几个方面：（1）以主—从机器人编队中从机器人的固联视觉传感器的观察角度出发，用视觉等效相对速度建立了主—从机器人编队系统的运动学模型。同时，在该模型中考虑了由视觉传感器时间延迟所导致的模型误差对编队系统的影响。在基于该运动学模型的编队控制器的设计过程中结合了基于从机器人载体的动力学的速度控制器。这种基于编队运动学和机器人本体动力学相结合的控制方法，避免了以往文献中速度跟踪响应无限快的假设。使得对编队控制系统的分析和设计更趋于实际。用Lyapunov稳定性理论证明了主—从机器人之间的编队跟踪误差和从机器人载体的速度跟踪误差都可以收敛到零--整体系统的渐进稳定性。（2）结合上述编队控制律，提出了一种编队系统中从机器人主动避障的方法，该方法能够令从机器人在避开动态障碍物的同时，与主机器人保持期望的相对距离或相对方位。这种方法的实质是由主机器人来引导从机器人的避障过程，主—从机器人之间通过相互协作来完成避障任务。这就使得从机器人即使在避障的过程中也能够与主机器人保持部分的协作。这样，当避障过程结束之后，主—从机器人之间可以迅速的恢复队形。（3）导出了一种新的基于相对运动学的主—从跟踪系统的二阶运动学模型。利用这个运动学模型，我们设计了一个由反馈线性化控制器和一个滑模控制器组成的复合控制器，来实现机器人主—从跟踪系统的控制。运用Lyapunov理论证明了所设计的队形控制器能够镇定包括内部动力学系统在内的整个主—从跟踪系统。同时，该控制器使得队形跟踪系统对主机器人的绝对加速度具有鲁棒性。此外，在前述控制器的基础上，我们设计了一个自适应队形控制器来处理主—从跟踪系统中存在的参数不确定性。（4）将上述基于二阶运动学的编队控制方法与从机器人的载体动力学控制系统相结合，给出了将编队运动学与载体动力学相结合的编队控制器设计方法。同时，针对载体动力学模型中含有参数不确定性的情况，设计了基于自适应控制方法的编队控制器。同时，利用Lyapunov理论给出了保证整体系统稳定性的条件。（5）基于主—从编队系统的二阶运动学模型，将队形反馈信息引入主机器人的轨迹跟踪控制器中，形成了主—从机器人协调编队的辅助控制律。该辅助控制律所对应的虚拟协调力通过主机器人的动力学系统形成了真实的协作控制力。该控制器与前一章中的从机器人的鲁棒编队跟踪控制器共同形成了主—从编队系统的协调控制器。应用Lyapunov理论给出了在主—从机器人分别采用协调编队控制器的作用下所形成的闭环系统的稳定性条件。进一步地，我们将主机器人的面向轨迹跟踪任务的协调控制器转换为面向路径跟踪任务的协调控制器。分别利用了基于MATLAB的仿真平台和实际的多移动机器人系统，验证了以上各方法的有效性。

基于跟随领航者法的多UUV队形控制方法研究

本文主要研究基于跟随领航者法的多 UUV(unmanned underwater vehicle)队形控制。在 UUV 载体坐标系下建立系统的运动学模型,该模型是对笛卡尔坐标系下的运动学模型的改进,避免了极坐标系下奇异点的出现。该模型经过输入输出反馈线性化,获得稳定的队形控制器。同时,为了缩小队形控制律中的控制参数的调整范围,本文提出了辅助算法,在此基础上分析参数的有效范围。将队形控制律在多 UUV 数字仿真平台上验证,证实了改进的运动学模型和控制律的有效性。

多水下机器人的队形控制方法研究

本文采用跟随领航者法研究多水下机器人(Unmanned Underwater Vehicles, UUVs)的队形控制，研究内容主要包括三个方面：设计基于运动学模型的多UUVs队形控制器；将该队形控制器结合机器人的动力学特性研究队形控制问题；研究领航者避碰算法以及多UUVs群体的队形变换策略。 跟随领航者法根本的问题是研究领航者与任意一个跟随者之间的协调问题，因此本文将复杂的多UUVs系统简化为若干组两个UUVs组成的基本队形模型。为了避免出现极坐标系下不可预见的奇异点，我们提出在UUV载体坐标系下建立运动学模型，实现与UUV动力学坐标系的统一。将该模型转化为误差动力学模型之后，经过输入输出反馈线性化，得出基于运动学模型的队形控制律。将该控制律应用到多UUV的队形控制问题中，则每个跟随者与领航者之间都具有协调，跟随者之间互相独立。 上述队形控制器中UUV具有无限快的速度跟踪能力，而实际上UUV不具备这样的能力，因此在队形控制器的设计过程中应结合UUV的动力学特性，使得对多UUVs队形控制问题的分析和设计更接近实际。本文以基本队形模型为研究对象，结合实际载体的动力学特性，研究队形控制器。 在未知的海洋环境中，当多UUVs系统检测到障碍物时，本文所采用的策略是：领航者采用基于模糊逻辑的避碰控制算法，顺利地通过障碍物区域；同时，领航者依据其艏部的避碰声纳信息，发出变换队形的指令。该策略使得领航者在引领跟随者顺利通过障碍物区域的同时，又不影响领航者与跟随者之间的协调。 在变换队形的过程中，存在着UUV之间发生碰撞的隐患，本文提出了就近原则：领航者左侧的UUV依然在左侧或中间，右侧的依然在右侧或中间。 本文分别利用了MATLAB仿真平台和多UUVs数字仿真平台，验证了以上各方法的有效性。由于多UUVs数字仿真平台中的控制参数、水动力系数、传感器参数均源自于实际的载体和历次湖试、海试的试验数据，UUV之间的通信信道是基于实际的水声通信模型，因此该平台上的仿真结果可以证明上述方法具有实际可行性。

Simulation of Severe Slugging Formation and Control in Offshore Riser

In this paper, available elimination techniques are assessed. OLGA2000 software is used to simulate severe slugging formation mechanism in certain offshore riser. The simulation results show that pressure fluctuations of riser base and riser top is very large and severe slugging easily forms. Sensibility analysis shows that the measures and methods which include properly reducing pipe riser diameter, reducing water cut increasing terminal pressure, decreasing the height and inclination of riser and increasing GOR can eliminate or control severe slugging in riser pipe.

Application of Ru(bpy)(3)(2+) in control and formation of gold surface nanostructure through oxidation-reduction cycling

It was studied that the nanostructure formed on a gold surface via a simple oxidation-reduction cycles (ORC) in 0.1 M KCl containing Ru(bpy)(3)(2+) with different concentrations. Atomic force microscopy (AFM) and energy-dispersed spectroscopy (EDS) were used to characterize the nanostructure formed on the gold surface. Sweep-step voltammetry and corresponding electroluminescence (ECL) response, in situ electrochemical quartz crystal microbalance (EQCM) measurement were used to monitor the ORC. procedure. It was found that the surface structure became more uniform in the presence of Ru(bpy)(3)(2+), and the surface roughness was decreasing with the increasing of Ru(bpY)(3)(2+) concentration, suggesting a simple and effective method to control the formation of nanostructure on the gold surface.

Photoperiodic long-day control of sporophyll and hair formation in the brown alga Undaria pinnatifida

Two photoperiodic responses, the development of sporophylls and hairs, have been quantified in sporophytes of the brown alga Undaria pinnatifida. In a final experiment, the algae were cultivated in outdoor, 2000-L seawater tanks in a greenhouse for up to 12 weeks, and daylength was regulated by automatic blinds mounted on top of the tanks. Vegetative young sporophytes were treated under short-day (SD; 8 h light per day) or long-day conditions (LD; 16 h light per day), at 12 h light per day or in a night-break regime (NB; 8 h light per day, 7.5 h dark, 1 h light, 7.5 h dark). The earliest sporophyll development was observed 6, 7 or 9 weeks under LD, NB or SD conditions, respectively. After 12 weeks the sporophylls were significantly longer and wider under LD or NB conditions than in the SD regime, and only half of the experimental algae had formed sporophylls under SD conditions, but all algae under LD or NB conditions. In a foregoing 7-week culture experiment performed in 300-L indoor tanks, enhanced sporophyll formation had also been observed under LD and not under SD conditions (NB omitted). In both experiments, blade elongation rates remained high until the end of the experiments in SD, but declined during sporophyll initiation in LD, NB or at 12 h light per day. Another difference caused by photoperiod was observed in regard to the development of surface hair spots which occurred in both experiments on the blades in LD, NB or at 12 h light per day with identical densities, but were completely lacking under SD conditions. It is concluded that U. pinnatifida is a facultatative long-day plant in regard to reproduction forming vigorously sporophylls in long days, and an obligate long-day plant in regard to hair formation.

Electrochemical, spectroscopic and SPM evidence for the controlled formation of self-assembled monolayers and organised multilayers of ferrocenyl alkyl thiols on Au(111)

Organised multilayers were formed from the controlled self-assembly of ferrocene alkyl thiols on Au(111) surfaces. The control was accomplished by increasing the concentration of the thiol solutions used for the assembly. Cyclic voltammetry, ellipsometry, scanning probe microscopy (STM and AFM) and in situ FTIR spectroscopy were used to probe the differences between mono- and multilayers of the same compounds. Electrochemical desorption studies confirmed that the multilayer structure is attached to the surface via one monolayer. The electrochemical behaviour of the multilayers indicated the presence of more than one controlling factor during the oxidation step, whereas the reduction was kinetically controlled which contrasts with the behaviour of monolayers, which exhibit kinetic control for the oxidation and reduction steps. Conventional and imaging ellipsometry confirmed that multilayers with well-defined increments in thickness could be produced. However, STM indicated that at the monolayer stage, the thiols used promote the mobility of Au atoms on the surface. It is very likely that the multilayer structure is held together through hydrogen bonding. To the best of out knowledge, this is the first example of a controlled one-step growth of multilayers of ferrocenyl alkyl thiols using self-assembly techniques.

TMVA, a novel GPIb-binding protein, significantly prevents platelet microthrombi formation and prolongs discordant cardiac xenograft survival

In xenotransplantation, donor endothelium is the first target of immunological attack. Activation of the endothelial cell by preformed natural antibodies leads to platelet binding via the interaction of the glycoprotein (GP) Ib and von Willebrand factor (vWF). TMVA is a novel GPIb-binding protein purified from the venom of Trimeresurus mucrosquamatus. In this study, the inhibitory effect of TMVA on platelet aggregation in rats and the effect on discordant guinea pig-to-rat cardiac xenograft survival were investigated. Three doses (8, 20 or 40 mug/kg) of TMVA were infused intravenously to 30 rats respectively. Platelet aggregation rate was assayed 0.5, 12, and 24 h after TMVA administration. Wister rats underwent guinea pig cardiac cervical heterotopic transplantation using single dosing of TMVA (20 mug/kg, i.v., 0.5 h before reperfusion). Additionally, levels of TXB2 and 6-keto-PGF(1alpha) within rejected graft tissues were determined by radioimmunoassay. Treatment with TMVA at a dose of 20 or 40 mug/kg resulted in complete inhibition of platelet aggregation 0.5 h after TMVA administration. Rats receiving guinea pig cardiac xenografts after TMVA therapy had significantly prolonged xenograft survival. Histologic and immunopathologic analysis of cardiac xenografts in TMVA treatment group showed no intragraft platelet microthrombi formation and fibrin deposition. Additionally, the ratio of 6-keto-PGF(1alpha) to TXB2 in TMVA treatment group was significantly higher than those in control group. We conclude that the use of this novel GPIb-binding protein was very effective in preventing platelet microthrombi formation and fibrin deposition in a guinea pig-to-rat model and resulted in prolongation of xenograft survival. The increased ratio of PGI(2)/TXA(2) in TMVA treatment group may protect xenografts from the endothelial cell activation and contribute to the prolongation of xenograft survival.

Selective control of toxic Microcystis water blooms using lysine and malonic acid: An enclosure experiment

Three enclosures (10 x 10 x 1.5-1.3 m in depth) were set beside Dianch Lake, Kunming, People's Republic of China, for the period from July 28 to August 26, 2002. The enclosures were filled with cyanobacterial (Microcystis aeruginosa) water bloom-containing lake water. Lake sediment that contained macrophytes and water chestnut seeds was spread over the entire bottom of each enclosure. Initially, 10 g/m(2) of lysine was sprayed in Enclosure B, and 10 g/m(2) each of lysine and malonic acid were sprayed together in Enclosure C. Enclosure A remained untreated and was used as a control. The concentrations of lysine, malonic acid, chlorophyll a, and microcystin as well as the cell numbers of phytoplankton such as cyanobacteria, diatom, and euglena were monitored. On day 1 of the treatment, formation of cyanobacterial blooms almost ceased in Enclosures B and C, although Microcystis cells in the control still formed blooms. On day 7 Microcystis cells in Enclosure B that had been treated with lysine started growing again, whereas growth was not observed in Microcystis cells in Enclosure C, which had been treated with lysine and malonic acid. On day 28 the surface of Enclosure B was covered with water chestnut (Trapa spp.) and the Microcystis blooms again increased. In contrast, growth of macrophytes (Myriophllum spicatum and Potamogeton crispus) was observed in Enclosure C; however, no cyanobacterial blooms were observed. Lysine and malonic acid had completely decomposed. The microcystin concentration on day 28 decreased to 25% of the initial value, and the pH shifted from the initial value of 9.2 to 7.8. We concluded that combined treatment with lysine and malonic acid selectively controlled toxic Microcystis water blooms and induced the growth of macrophytes. (c) 2005 Wiley Periodicals, Inc.

Formation of self-assembly and the mechanism of Si nanoquantum dots prepared by low pressure chemical vapor deposition

Si nanoquantum dots have been formed by self-assembled growth on the both Si-O-Si and Si-OH bonds terminated SiO2 surfaces using the low-pressure chemical vapor deposition (LPCVD) and surface thermal decomposition of pure SiH4 gas. We have experimentally studied the variation of Si. dot density with Si-OH bonds density, deposition temperature and SiH4 pressure, and analyzed qualitatively the formation mechanism of the Si nanoquantum dots based on LPCVD surface thermal dynamics principle. The results are very. important for the control of the density and size of Si nanoquantum dots, and have potential applications in the new quantum devices.

Crack control in GaN grown on silicon (111) using In doped low-temperature AlGaN interlayer by metalorganic chemical vapor deposition

The effects of In doped low-temperature (LT) AlGaN interlayer on the properties of GaN/Si(111) by MOCVD have been investigated. Using In doping LT-interlayer can decrease the stress sufficiently for avoiding crack formation in a thick (2.0 mu m) GaN layer. Significant improvement in the crystal and optical properties of GaN layer is also achieved. In doping is observed to reduce the stress in AlGaN interlayer measured by high-resolution X-ray diffraction (HRXRD). It can provide more compressive stress to counteract tensile stress and reduce crack density in subsequent GaN layer. Moreover, as a surfactant, indium is observed to cause an enhanced PL intensity and the narrowed linewidths of PL and XRD spectra for the LT-interlayer. Additionally, the crystal quality of GaN layer is found to be dependent on the growth parameters of underneath In-doped LT-AlGaN interlayer. The optimal parameters, such as TMIn flow rate, TMAl flow rates and thickness, are achieved to obtain nearly 2.0 mu m thick crack free GaN film with advanced optical and crystal properties. (c) 2005 Elsevier B.V. All rights reserved.

CONTROLLED FORMATION AND CHARACTERISTICS OF INTERFACES IN GAAS/ALGAAS SINGLE QUANTUM-WELLS

The influence of heterostructure quality on transport and optical properties of GaAs/AlGaAs single quantum wells with different qualities was studied. In a conventional sample-A, the transport scattering time and the quantum scattering time are small and close to each other. The interface roughness scattering is a dominant scattering mechanism. From comparison between theory and experiment, interface roughness with fluctuation height 2.5 Angstrom and the lateral size of 50-70 Angstrom were estimated. For samples introducing superlattices instead of AlGaAs layers or by utilizing growth interruption, both the transport and PL measurements showed that interfaces were rather smooth in the samples. The two scattering times are much longer. The interface roughness scattering is relegated to an unimportant position. Results demonstrated that it is important to control the formation of heterostructures in order to improve the interface quality.

SrF2 hierarchical flowerlike structures: Solvothermal synthesis, formation mechanism, and optical properties

We present a solvothermal route to the synthesis of SrF2 hierarchical flowerlike structures based on thermal decomposition of single source precursor (SSP) of strontium trifluoroacetate in benzylamine solvent. These flowerlike superstructures are actually composed of numerous aggregated nanoplates, and the growth process involves the initial formation of spherical nanoparticles and subsequent transformation into nanoplates. which aggregated together to form microdisks and finally flowerlike superstructures. The results demonstrate the important role of benzylamine in the formation of well-defined SrF2 superstructures, not only providing size and shape control to form nanoplates but also contributing to the self-assembly behavior of nanoplates to build into flower-like superstructures. Additionally, the photoluminescence properties of the obtained SrF2 superstructures are studied.

Synthesis of CdTe nanocrystals using Te nanorods as the Te source and the formation of microtubes with red fluorescence

Here, we report an alternative route to the preparation of highly luminescent CdTe nanocrystals (NCs) using Te nanorods instead of freshly prepared NaHTe as the Te source via a one-pot route under hydrothermal conditions. Furthermore, microtubes with red fluorescence were generated via simply aging the above CdTe NC suspension under ambient conditions.