盾构切削混凝土桥桩刀盘荷载分析

依托北京地铁12号线盾构直接切削西坝河桥16根800桥桩工程,通过三维数值模拟和理论推导,对盾构法清障掘进面荷载展开研究。通过三维动态模拟,分析单个刀具逐次切混凝土荷载变化规律。基于等效原理与单刀切削荷载,提出一种对切桩刀具数、推力及扭矩的估算模型。并将此估算模型用于计算苏州地铁直接切削广济桥掘进面荷载,对比分析计算结果与精确叠加值在推力、扭矩方面的平均误差分别为10%、3.3%,验证了该估算模型的正确性。应用本文模型对盾构穿越西坝河桥各轴桩位掘进面切桩荷载进行预测分析,指出切桩工况主要对扭矩造成影响。研究结果可为类似地层盾构清障工程中掘进面荷载计算提供参考。     

轮廓特征包在激光主动照明识别系统中的应用

提出了一种结合轮廓转动惯量和特征包(Bo F)算法的激光主动照明目标识别方法。介绍了转动惯量的定义,并提出了一种多尺度轮廓转动惯量特征区域检测方法和轮廓转动惯量局部不变特征提取方法。多尺度轮廓转动惯量特征区域检测方法能够提取出包含轮廓的最小特征区域,而轮廓转动惯量局部不变特征能够很好地描述轮廓的大小、位置、规则度等信息,对于各种图像变换具有不变性,并且计算效率较高。使用Bo F算法统计图像的轮廓转动惯量局部不变特征,生成归一化特征直方图作为整幅图像的特征向量,输入训练好的支持向量机分类器进行识别。实验结果表明与基于Hu矩和BP神经网络的目标识别方法相比,所提算法在旋转和仿射变换下的识别率分别提高7.33%和19.08%。     

外部转矩干扰的非完整移动机器人轨迹追踪控制研究

针对外部转矩干扰的非完整机器人运动不稳定、轨迹追踪控制精度较低等问题,提出了无源控制理论的控制方法。构造了非完整移动机器人的动力学模型,介绍了机器人空间运动控制的基本形式。采用无源控制方法设计了机器人末端执行器,使用李雅普诺夫综合法对无源控制闭环系统的稳定性和追踪误差的渐近收敛性进行了证明。结合具体实例,通过Matlab软件对外部转矩干扰的非完整移动机器人运动追踪轨迹和输出转矩进行仿真,并且与PI控制方法形成对比。仿真结果显示,无源控制方法的实际轨迹朝理论轨迹收敛,轨迹追踪误差较小,输出转矩波动小。无源控制方法可以避免外部转矩干扰的非完整机器人运动不稳定,提高轨迹追踪精度。     

Electromagnetic torque detecting for optimization of in-mould electromagnetic stirring in the billet and bloom continuous casting

ABSTRACT

In this paper, an electromagnetic torque device based on the theoretical model was established to determine the optimum frequency accurately and conveniently in billet and bloom continuous casting with in-mould electromagnetic stirring (M-EMS). Magnetic characteristics with M-EMS was investigated by numerical simulation and physical experiment with the application of electromagnetic torque device and gauss meter. In addition, the effects of stirring frequency with M-EMS on macro segregation and equiaxed crystal ratio were compared and analysed for 55SiCr with 150?mm?×?150?mm billet caster and BU with 310?×?360?mm bloom caster by a series of plant trials, respectively. The results showed that maximum magnetic flux density and maximum electromagnetic torque occurred with different frequency and same current in M-EMS, and central equiaxed crystal ratio and macro segregation has been significantly improved by optimum frequency with M-EMS.     

First experimental results of intrinsic torque on EAST

Direct measurements of the intrinsic torque profile in L-mode plasmas on the EAST tokamak have been performed using the balanced neutral beam injection. Co-and counter-current neutral beams are modulated to balance the intrinsic and externally injected torques, which result in the rotation profile close to zero and flat. The experimental results show that the intrinsic torque derived from momentum balance equations is found to be in the co-current direction, peaked in the plasma edge and negligibly small in the core.     

核电站放射性污染液压扭力扳手的去污实践

核电站在日常生产及大修过程中,放射性污染设备和场地的检修作业会产生一定量的污染检修工具,其中包含价值高、体积大、去污难度大的液压扭力扳手。因液压扭力扳手结构复杂、主子部件较多、且热点多淤积在死角位置,导致其放射性去污难度较大,国内核电站多作放射性固体废物处理为主。液压扭力扳手作为高价值专用工具,大量放射性污染检修工具报废给核电站成本管控、放射性废物最小化管理和电站辐射防护最优化带来了较大的压力。针对此问题, 电站开展了多项放射性污染液压扭力扳手深度去污试验,采用化学去污、机械去污、泡沫去污、超声波去污等多种组合工艺,经过四个阶段的深度去污试验,最终将多台放射性污染液压扭力扳手全部去污合格,并全部实现现场复用。此次深度去污试验研究总结的“放射性污染液压扭力扳手深度去污方法”,去污因子超过10³,去污试验各项指标效果良好,方法可行、有效、实用,可为业内同行提供参考。     

Direct torque control of doubly fedinduction motor using three-level NPCinverter

This article presents the direct torque control (DTC) strategy for the doubly fed induction motor (DFIM) connected to two three-level voltage source inverters (3LVSIs) with neutral point clamped (NPC) structure. This control method allows to reduce the torque and flux ripples as well as to optimize the total harmonic distortion (THD) of motor currents. The use of 3LVSI increases the number of generated voltage, which allows improving the quality of its waveform and thus improves the DTC strategy. The system modeling and control are implemented in Matlab/ Simulink environment. The analysis of simulation results shows the better performances of this control, especially in terms of torque and flux behavior, compared to conventional DTC.     

Influence of the gasket materials on the clamping pressure distribution in a PEM water electrolyzer: Bolt torques and operation mode in pre-conditioning

To keep optimally connected, all electrolysis cell elements is one of the most important design criteria. The optimal distribution of the clamping points is crucial to increasing cell performance. In this work, the compression pressure distribution inside of a 25 cm² PEM electrolysis cell was evaluated, using different materials: Teflon®, Viton®, ethylene propylene diene monomer rubber (EPDM), and nitrile rubber. Sealing material evaluation was performed taking as performance indicators: total compressed area (%) and compression pressure, for different torques applied. Pressure distribution was obtained by using pressure-sensitive films, analyzing the distribution of pressure points from three-dimensional plots (3D), and quantifying intensities of the images obtained. Results showed that pressure points distribution depends on the stiffness and thickness of the gasket materials. For a tightening torque of 3.70 N m, a pressure of 2.23 MPa is obtained with 85% of the membrane area compressed using nitrile rubber-EPDM gaskets.     

Modified dynamic surface approach with bias torque for multi-motor servomechanism

This paper presents a modified neural dynamic surface control (DSC) with an adaptive bias torque for the multi-motor servomechanism (MMS) with backlash, friction and other disturbances. By introducing a continuous hybrid differentiator to replace the first-order filter in each step, a modified DSC is developed to improve the load tracking precision of MMS. However, when the MMS enters the backlash band, only DSC cannot guarantee the load tracking performance. Thus, an adaptive bias torque is firstly proposed based on the prescribed performance function technique to compensate the backlash nonlinearity and guarantee the load tracking performance of MMS. In addition, the unknown dynamics including the friction and other disturbances are approximated by using wavelet echo state networks where the weights are all updated online. By means of Lyapunov stability theory, the semi-globally uniformly ultimately bounded (SGUUB) property of all signals in the closed-loop system is proved. Finally, simulations and experimental results based on a four-motor servomechanism are presented to show the effectiveness of the proposed approach.     

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介绍了一种全新设计的材料扭转试验机,主要采用了液压回转式夹具装夹试样,通过伺服电机—滚珠丝杆—传感器方式对长线材试样施加恒定的拉紧力,以及伺服电机—减速机构驱控夹头双向旋转,可针对Ф7 mm~Ф14 mm、2 000 MPa级长线材试样开展各类扭转以及低成本的慢速拉扭复合疲劳试验。基于对试样扭矩变化的实时跟踪,可实现0.000 5~30 r/min的变速扭转以及在扭矩陡降(即最大扭转塑性)瞬时临界采样,供后续试样内部组织与外表面形貌评价分析。