Control of non‐integer‐order dynamical systems using sliding mode scheme

This article deals with the problem of control of canonical non‐integer‐order dynamical systems. We design a simple dynamical fractional‐order integral sliding manifold with desired stability and convergence properties. The main feature of the proposed dynamical sliding surface is transferring the sign function in the control input to the first derivative of the control signal. Therefore, the resulted control input is smooth and without any discontinuity. So, the harmful chattering, which is an inherent characteristic of the traditional sliding modes, is avoided. We use the fractional Lyapunov stability theory to derive a sliding control law to force the system trajectories to reach the sliding manifold and remain on it forever. A nonsmooth positive definite function is applied to prove the existence of the sliding motion in a given finite time. Some computer simulations are presented to show the efficient performance of the proposed chattering‐free fractional‐order sliding mode controller. © 2015 Wiley Periodicals, Inc. Complexity 21: 224–233, 2016     

Radio resource management scheme and outage analysis for network-assisted multi-hop D2D communications

In a cellular network it's very difficult to make spectrum resource more efficiently. Device-to-Device (D2D) technology enables new service opportunities, and provides high throughput and reliable communication while reducing the base station load. For better total performance, short-range D2D links and cellular links share the same radio resource and the management of interference becomes a crucial task. Here we argue that single-hop D2D technology can be used to further improve cellular networks performance if the key D2D radio resource management algorithms are suitably extended to support multi-hop D2D communications. Aiming to establish a new paradigm for the analysis and design of multi-hop D2D communications, We propose a radio resource allocation for multi-hop D2D routes based on interference avoidance approach in LTE-A networks. On top of that, we investigate the outage probability of D2D communication. We first introduce a new definition of outage probability by considering the maximum distance to be allowable for single-hop transmission. Then we study and analyze the outage performance of a multi-hop D2D route. We derive the general closed form expression of outage probability of the multi-hop D2D routes. The results demonstrate that the D2D radio, sharing the same resources as the cellular network, provide higher capacity compared to pure cellular communication where all the data is transmitted through the base station. They also demonstrate that the new method of calculation of D2D multi hop outage probability has better performance than classical method defined in the literature.     

Optimal Control of a Ship for Collision Avoidance Maneuvers

We consider a ship subject to kinematic, dynamic, and moment equations and steered via rudder under the assumptions that the rudder angle and rudder angle time rate are subject to upper and lower bounds. We formulate and solve four Chebyshev problems of optimal control, the optimization criterion being the maximization with respect to the state and control history of the minimum value with respect to time of the distance between two identical ships, one maneuvering and one moving in a predetermined way.Problems P1 and P2 deal with collision avoidance maneuvers without cooperation, while Problems P3 and P4 deal with collision avoidance maneuvers with cooperation. In Problems P1 and P3, the maneuvering ship must reach the final point with a given lateral distance, zero yaw angle, and zero yaw angle time rate. In Problems P2 and P4, the additional requirement of quasi-steady state is imposed at the final point.The above Chebyshev problems, transformed into Bolza problems via suitable transformations, are solved via the sequential gradient-restoration algorithm in conjunction with a new singularity avoiding transformation which accounts automatically for the bounds on rudder angle and rudder angle time rate.The optimal control histories involve multiple subarcs along which either the rudder angle is kept at one of the extreme positions or the rudder angle time rate is held at one of the extreme values. In problems where quasi-steady state is imposed at the final point, there is a higher number of subarcs than in problems where quasi-steady state is not imposed; the higher number of subarcs is due to the additional requirement that the lateral velocity and rudder angle vanish at the final point.     

DSC Calibration During Cooling

A number of compounds are investigated for DSC calibration during cooling. Adamantane and Zn show fast reversible transitions and can be applied both for temperature and for heat calibration. A third compound, namely 4,4′-azoxyanisole, has a liquid crystal to isotropic liquid transition at 409 K. This compound can be used for temperature calibration. Heat calibration with this compound is more problematic because of the small heat effect and the construction of the baseline. Two other compounds, namely Hg and Pb, show a slight undercooling. Nevertheless they can be used for heat calibration, and possibly also for temperature calibration during cooling. This revised version was published online in August 2006 with corrections to the Cover Date.     

Particle production, back reaction and singularity avoidance

We consider particle production in Robertson-Walker spacetime as particle-antiparticle rotation. We thereby obtain a scale factor that guarantees particle production. We then study quantum field effects in spatially flat homogeneous and isotropic spacetime with energy density of created particles and one loop quantum correction as back reaction. In the numerical solution initial values are determined from particle production simulated scale factor and obtain the evolution of the universe both at early and late times having a bounce.     

高职生顶岗实习的健康风险与避险工具分析

顶岗实习是培养高职学生职业能力的重要环节。在顶岗实习期间, 学生可能会遭遇意外伤害和重大疾病等潜在风险的威胁。医疗保险、实习责任险、轻松筹等三种避险工具在抵制健康风险上既有自身的优点, 又存在着各自的问题与不足。针对存在的问题, 应从提高医保保障水平、实习责任保险强制化以及规范管理轻松筹等方面进行改进, 以更好地发挥其避险功能。     

Relating geologic units and mobility system kinematics contributing to Curiosity wheel damage at Gale Crater,Mars

Curiosity landed on plains to the north of Mount Sharp in August 2012. By June 2016 the rover had traversed 12.9 km to the southwest, encountering extensive strata that were deposited in a fluvial-deltaic-lacustrine system. Initial drives across sharp sandstone outcrops initiated an unacceptably high rate of punctures and cracks in the thin aluminum wheel skin structures. Initial damage was found to be related to the drive control mode of the six wheel drive actuators and the kinematics of the rocker-bogie suspension. Wheels leading a suspension pivot were forced onto sharp, immobile surfaces by the other wheels as they maintained their commanded angular velocities. Wheel damage mechanisms such as geometry-induced stress concentration cracking and low-cycle fatigue were then exacerbated. A geomorphic map was generated to assist in planning traverses that would minimize further wheel damage. A steady increase in punctures and cracks between landing and June 2016 was due in part because of drives across the sharp sandstone outcrops that could not be avoided. Wheel lifetime estimates show that with careful path planning the wheels will be operational for an additional ten kilometers or more, allowing the rover to reach key strata exposed on the slopes of Mount Sharp.     

高光谱成像技术检测高温障碍胁迫下番茄叶片色差的研究

提出了利用可见/近红外高光谱成像技术检测高温障碍胁迫下番茄叶片色差的方法。首先采集380~1 023 nm波段范围内60个高温障碍胁迫和60个健康番茄叶片的高光谱图像,同时获取全部叶片的色差值(L*, a*和b*),然后提取所有样本的高光谱图像中感兴趣区域(region of interest, ROI)的光谱反射率值。基于不同预处理方法建立偏最小二乘(partial least squares, PLS)预测模型,再利用连续投影算法(successive projections algorithm, SPA)提取特征波长并建立SPA-PLS预测模型。最后分别基于全波段和特征波段建立偏最小二乘-判别分析(partial least squares-discriminant analysis, PLS-DA)模型。结果显示,全波段中基于原始光谱信息建立的模型效果最好,3个色差值的预测集决定系数(determination coefficient, R2)分别是0.818,0.109和0.896;基于特征波长建立的模型预测集R2分别是0.591,0.244和0.673;所有模型预测集的总体识别率均大于77.50%。结果表明,可见/近红外高光谱成像技术检测番茄叶片色差值(L*和b*)和识别高温障碍样本是可行的。     

初始权值优化技术在机器人学习中的应用

针对移动机器人建立了基于BP神经网络的智能避障控制模型,提出了初始权值优化技术,使得样本组与初始权值相匹配,显著地提高了网络的收敛速度.为了提高系统的实时性,文中采用C和汇编语言混合编制控制程序.计算机仿真和实测结果表明该系统具有学习能力强、人机交互效果好等优点.     

深亚微米IC物理设计流程中的串扰控制

信号完整性的设计收敛已经成为当前深亚微米集成电路物理设计流程中的关键问题。对信号完整性收敛产生不利影响的有三个因素：串扰、直流电压降和电迁移。其中影响最大的是串扰,串扰噪声会产生大量的时序违规、逻辑错误。主要关注基于串扰控制的物理设计方法,包括新的流程、各个设计阶段对串扰的分析及修正的方法,以达到快速的时序收敛。并且根据真实的设计实例,提出了几点有效的控制串扰的方法和对于信号完整性管理比较有价值的观点。