Decentralized optimal tracking control for large-scale nonlinear systems with tracking error constraints

In this article, a decentralized optimal tracking control strategy is proposed for a class of nonlinear systems with tracking error constraints by utilizing adaptive dynamic programming (ADP). It should be noted that ADP technology cannot be directly used to solve decentralized optimal tracking problem of large-scale interconnected nonlinear system with nonzero equilibrium points, since that an infinite domain performance index function may result in an unsolvable solution. In addition, by introducing a smooth function, the constrained tracking error is transformed into an unconstrained one. Then, the error dynamics and a new infinite domain performance index function are designed, such that ADP technology can be used. Following the designed performance index function, the tracking error can be ensured within a small neighborhood of zero. Finally, the feasibility and the effectiveness of the proposed decentralized optimal control scheme are verified through two simulation examples.     

果实表面颜色计算机视觉分级技术研究

本文借助计算机中的视觉自动检测技术来测量在果实表面的着色度,并对该颜色进行了分级,进一步的对颜色进行分析与研究,进而来获得出最终的水果果实的彩色图像,进一步的分析出对应的结果。因此,在本文中,对果实表面颜色进行了全面综合的分析与研究,进而来得出对应的果实颜色分级标准和原则。     

基于虚拟导航线的农业机器人精确视觉导航方法

针对农田、野外环境中无人工标记情况下的导航问题，提出了一种基于虚拟导航线的农业机器人精确视觉导航方法。该方法不需要铺设导航线或者路标即可引导机器人行走直线。首先，根据需求确定需要跟踪的目标区域，之后控制机器人调整方向直到目标移至视野中央；其次，根据机器人和目标的位置确定参照目标，并依据两个目标的位置确定虚拟导航线；然后，动态更新导航线，并结合虚拟定标线和虚拟导航线确定偏移角度和偏移距离；最后，利用偏移参数构建模糊控制表，并以此实现对机器人旋转角度和行走速度的调整。实验结果表明，该算法能较为精确地实现对导航路线的识别，进而利用模糊控制策略使机器人沿直线向目标行走，且导航精度在10 cm以内。     

Exploratory factor analysis and validity of the virtual reality symptom questionnaire and computer use survey

Abstract

The widespread use of virtual reality head-mounted-displays (HMDs) calls for a re-examination of the impact of prolonged exposure to fixed visual displays at close ocular proximity. The purpose of this study is to validate the Virtual Reality Symptoms Questionnaire (VRSQ), created to understand symptoms of prolonged HMDs use, and Computer Use Survey (CUS), created to assess general physical and visual discomfort symptoms. Participants (N?=?100) recorded their general discomfort symptoms using the CUS, performed an interactive task using a HMD for thirty minutes, and then answered the CUS again along with the VRSQ. VRSQ, analysed using an exploratory factor analysis, indicated a clear two-factor solution, and demonstrated very good internal consistency (α?=?0.873). The CUS, also analysed using an exploratory factor analysis, indicated a four-factor solution, and demonstrated good internal consistency (α?=?0.838).

Practitioner Summary: A quantitative-experimental study was conducted to explore the factor structure and validate both the Virtual Reality Symptoms Questionnaire (VRSQ), and the Computer Use Survey (CUS). Findings indicate the VRSQ and CUS are precise and accurate survey instruments for evaluating discomfort after VR-HMD use and the latter for computer use.

Abbreviations: VRSQ: virtual reality symptom questionnaire; CUS: computer use survey; OLED: organic light-emitting diode; MSQ: pensacola motion symptom questionnaire; SSQ: simulator sickness questionnaire; 3?D: three-dimensional computer generated space; VR: virtual reality; VR-HMD: virtual reality head-mounted-display; HMDs: head-mounted-displays; EFA: exploratory factor analysis     

紫砂造型艺术中直线和六方的韵律——简析“六方抽角壶”的形态结构与视觉感应

通过分析直线的性质和"六方抽角壶"的形态结构,探讨直线应用在紫砂光素方器中所产生的节奏韵律,以艺术审美的评判标准论证"六方抽角壶"刚柔并济、虚实相间、层次递进的视觉感应。     

Improved magnetic particle tracking technique in dense gas fluidized beds

Noninvasive monitoring of multiphase flow is rapidly gaining increased interest. More specifically noninvasive particle tracking techniques have received a lot of attention in recent years to study dense granular flow. However, these techniques are usually quite expensive and require strict safety measures. An improved magnetic particle tracking (MPT) technique for dense granular flow will be presented in this article. The improvements of the analysis technique for MPT will be demonstrated and rigorously tested with a three‐dimensional system and two‐dimensional sensor system. The strengths and limitations of the MPT technique will also be reported. Finally, the results of the MPT are compared with data obtained from a combined particle image velocimetry and digital image analysis technique. © 2014 American Institute of Chemical Engineers AIChE J, 60: 3133–3142, 2014     

Distribution of large biomass particles in a sand‐biomass fluidized bed: Experiments and modeling

The axial distribution of large biomass particles in bubbling fluidized beds comprised of sand and biomass is investigated in this study. The global and local pressure drop profiles are analyzed in mixtures fluidized at superficial gas velocities ranging from 0.2 to 1 m/s. In addition, the radioactive particle tracking technique is used to track the trajectory of a tracer mimicking the behavior of biomass particles in systems consisting of 2, 8, and 16% of biomass mass ratio. The effects of superficial gas velocity and the mixture composition on the mixing/segregation of the bed components are explored by analyzing the circulatory motion of the active tracer. Contrary to low fluidization velocity (U = 0.36 m/s), biomass circulation and distribution are enhanced at U = 0.64 m/s with increasing the load of biomass particles. The axial profile of volume fraction of biomass along the bed is modeled on the basis of the experimental findings. © 2014 American Institute of Chemical Engineers AIChE J, 60: 869–880, 2014     

轮式移动机器人滑移轨迹跟踪控制策略研究

针对轮式移动机器人在滑移条件下的轨迹跟踪问题,提出一种自适应模糊控制策略。利用模糊状态观测器对未知的复杂系统模型进行速度估计和补偿,通过设计输出向量将位置约束转换为输出约束,并构造Barrier Lyapunov函数来保证机器人的运动约束,在此基础上设计更简单的纵向滑移模型,利用李亚普诺夫定理分析闭环系统的稳定性,证明了闭环系统中所有信号都是有界的。最后通过仿真和实验验证了自适应模糊控制策略在轮式机器人纵向滑移情况下的有效性和实用性。     

基于深度学习的单目视觉水下机器人目标跟踪方法研究

介绍了一种基于深度学习的单目视觉水下机器人目标跟踪新方法,采用该方法能够使自主水下机器人(AUV)在水下复杂环境中实现图像增强处理与目标识别跟踪,对于视频图像中的每个图像,使用预先经过训练的深度卷积神经网络计算图像传输图,图像传输图提供了图像深度信息的相关估计,该方法能够识别水下目标区域,并标明水下目标运动及跟踪方向。实验表明:该方法能够更精确、更稳定地获取水下环境中的定位数据。     

传统山地建筑视觉造型分析

传统山地建筑是人们在长期实践经验的积累下发展起来的一类建筑形式。这类建筑巧妙地利用山地地形来建造,在视觉造型艺术上有着独特的风格和魅力。本文分析了传统山地建筑视觉造型特征,希望对山地建筑创作有所启发。