油-气管道检测机器人技术现状及展望

为提高油-气管道检测的效果,结合国内外典型管道机器人的特点,综合分析了管道机器人运动控制技术、定位技术和实时检测技术3个方面的现状,并指出了核心技术的不足;针对石油化工行业高温带压管道环境,提出管道检测机器人的研究重点为分层模糊神经网络运动控制技术、CCD视觉定位技术、低频电磁定位技术和分层图像分割的优化方法等。为进一步提高化工油-气管道内检测机器人的检测效果提供了理论依据。     

机床爬行的仿真研究及控制措施

通过理论分析和数字仿真说明机床爬行的机理和原因，并针对各种原因全面介绍了国内外相应的防止方法和具体措施。     

汽车盘式制动衬片热压模设计

分析了汽车盘式制动嚣零件的工艺性，对其成形制造工艺、衬片模具结构及其设计、衬片模具的选材及主要零部件的制造加工要点、衬片模具的工作过程及使用情况等作了系统地介绍。     

卧式离心铸造汽缸套"黑斑"形成机理及预防措施

卧式离心铸造合金铸铁汽缸套"黑斑"是一种由合金成分和生产工艺等因素而造成的"夹层"石墨漂浮、比重偏析的综合缺陷.主要预防措施是强化冷却和将锰含量提高到2%.     

钢管除锈机设计与经验

介绍了钢管除锈机的基本原理及设计过程,实践证明:使用钢管除锈机不仅保证了除锈质量,还提高了工作效率。     

Finite-time coordination in multiagent systems using sliding mode control approach

Finite-time stability in dynamical systems theory involves systems whose trajectories converge to an equilibrium state in finite time. In this paper, we use the notion of finite-time stability to apply it to the problem of coordinated motion in multiagent systems. Specifically, we consider a group of agents described by fully actuated Euler–Lagrange dynamics along with a leader agent with an objective to reach and maintain a desired formation characterized by steady-state distances between the neighboring agents in finite time. We use graph theoretic notions to characterize communication topology in the network determined by the information flow directions and captured by the graph Laplacian matrix. Furthermore, using sliding mode control approach, we design decentralized control inputs for individual agents that use only data from the neighboring agents which directly communicate their state information to the current agent in order to drive the current agent to the desired steady state. Sliding mode control is known to drive the system states to the sliding surface in finite time. The key feature of our approach is in the design of non-smooth sliding surfaces such that, while on the sliding surface, the error states converge to the origin in finite time, thus ensuring finite-time coordination among the agents in the network. In addition, we discuss the case of switching communication topologies in multiagent systems. Finally, we show the efficacy of our theoretical results using an example of a multiagent system involving planar double integrator agents.     

A 3D analysis of the joint torques developed during driver's ingress–egress motion

Providing an easy ingress–egress (I/E) movement remains a challenge for car designers. I/E has been largely studied in kinematics, but not in dynamics. This study proposes: (1) to evaluate and describe the motor torques developed in the lower limbs and lumbar joints during I/E motions and (2) to analyse the influence of the car geometry and subject anthropometry. An experiment was performed to observe 15 subjects of three anthropometrical groups getting in and out of a car mock-up simulating three different vehicle configurations. Motor torques were extracted using an inverse dynamics analysis. Both ingress and egress motions were primarily characterised by large torques. Overall, the taller a subject and the lower the seat of the vehicle were, the larger the peak torques were. Moreover, peak torques were higher for egress than ingress. These results are discussed in regard to the current knowledge on I/E ergonomics.     

用于虚拟现实的360度视频编码技术新进展*

随着虚拟现实技术不断发展,360度视频编码开始成为研究热点。应用于虚拟现实的360度视频与传统的视频相比分辨率更高,编码数据量更大,在实际应用中面临传输带宽有限的瓶颈,编码效率问题有待解决。归纳分析了国际标准组织联合视频研究组（joint video exploration team, JVET）正在制定的360度视频编码投影变换技术及其编码优化方法,综合对比了各变换技术的编码性能。根据当前最新研究成果,对下一步研究需要解决的问题进行了探讨总结,给出未来的研究方向和思路。     

弯道岸坡上粗细泥沙统一起动流速公式

该文基于概率论与泥沙起动基本理论,考虑了起动概率、相对暴露度与细颗粒泥沙间黏结力和附加下压力对泥沙起动的影响,采用滑动起动模型,从理论上推导出了适用于弯道岸坡上粗、细泥沙颗粒起动的统一流速公式,完善了已有研究成果对泥沙起动概率考虑的不足。公式综合了弯道岸坡、顺直岸坡、正负坡及平坡等条件下粗细泥沙颗粒起动流速计算,可简化为各简单条件下泥沙起动流速公式。通过各简单条件下泥沙起动流速实测资料验证,该文公式与实测数据符合良好。     

Paramedics on the job: Dynamic trunk motion assessment at the workplace

Many paramedics' work accidents are related to physical aspects of the job, and the most affected body part is the low back. This study documents the trunk motion exposure of paramedics on the job. Nine paramedics were observed over 12 shifts (120 h). Trunk postures were recorded with the computer-assisted CUELA measurement system worn on the back like a knapsack. Average duration of an emergency call was 23.5 min. Sagittal trunk flexion of >40° and twisting rotation of >24° were observed in 21% and 17% of time-sampled postures. Medical care on the scene (44% of total time) involved prolonged flexed and twisted postures (∼10 s). The highest extreme sagittal trunk flexion (63°) and twisting rotation (40°) were observed during lifting activities, which lasted 2% of the total time. Paramedics adopted trunk motions that may significantly increase the risk of low back disorders during medical care and patient-handling activities.