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基于连杆机构旋转法则的平面单环闭链结构装配误差不确定性分析 被引量:5
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作者 赵强强 郭俊康 洪军 《机械工程学报》 EI CAS CSCD 北大核心 2018年第11期29-38,共10页
影响平面单环闭链结构装配精度的主要误差源有杆件加工偏差、装配约束误差以及铰链间隙。而铰链间隙的随机性导致平面单环闭链结构装配误差具有不确定性。为了能够实现装配精度预测和获得装配误差边界,通过分析平面单环四杆结构装配特点... 影响平面单环闭链结构装配精度的主要误差源有杆件加工偏差、装配约束误差以及铰链间隙。而铰链间隙的随机性导致平面单环闭链结构装配误差具有不确定性。为了能够实现装配精度预测和获得装配误差边界,通过分析平面单环四杆结构装配特点,提出单杆件固定和双杆件连接两种装配单元,并建立两种单元的误差模型。在此基础上,完成了无间隙平面单环闭链结构装配误差建模。然后通过引入连杆机构旋转法则,以虚拟杆件表征铰链间隙并将其视为“短杆”,从而基于杆件旋转不变性建立了考虑间隙的平面单环闭链结构装配误差不确定性分析模型,并给出了装配误差边界计算方法。最后以平面五杆单环结构作为数值案例,验证了所提出方法与模型的可行性与实用性。 展开更多
关键词 装配单元 旋转法则 平面单环结构 装配误差
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利用方差改进混凝土三维轴对称本构模型
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作者 姜庆远 刘宗仁 +1 位作者 田宇 徐雪宁 《沈阳建筑大学学报(自然科学版)》 CAS 2008年第2期248-251,共4页
目的为了使混凝土三维轴对称构件非线性有限元分析结果更加准确,利用方差对三维轴对称本构模型进行改进.方法根据Darwin和Pecknold提出的"等效单轴应变"概念,在Elwi和Murry混凝土三维轴对称正交异性本构模型的基础上,建立了... 目的为了使混凝土三维轴对称构件非线性有限元分析结果更加准确,利用方差对三维轴对称本构模型进行改进.方法根据Darwin和Pecknold提出的"等效单轴应变"概念,在Elwi和Murry混凝土三维轴对称正交异性本构模型的基础上,建立了新的混凝土三维轴对称本构模型.与Elwi和Murry的原模型不同,本构关系矩阵中的非对角元素的取值,是根据模型与试验方差最小的原则确定.结果通过与原模型对比可以看出,新模型的计算结果和试验符合较好.结论提出的三维轴对称模型是合理可行的,而且误差较小,可广泛地用于各种三维轴对称构件.利用方差改进模型方法不仅可用于三维轴对称模型,而且可以用于二维、三维模型.新的主应力旋转法则简单可行,可以避免计算结果突变. 展开更多
关键词 混凝土 三维轴对称本构模型 有限元分析 方差 主应力旋转法则
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土体边界面模型在ABAQUS软件中的研发与验证 被引量:3
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作者 钦亚洲 孙钧 《同济大学学报(自然科学版)》 EI CAS CSCD 北大核心 2012年第9期1318-1322,共5页
天然土体一般都处于偏压固结状态,存在着初始各向异性.即使是等压固结土体,在其后的偏压加载过程中,也会产生应力诱发各向异性.土体各向异性对其强度、变形及屈服面倾向都会产生影响.Wheeler弹塑性模型采用旋转硬化来描述土体的各向异性... 天然土体一般都处于偏压固结状态,存在着初始各向异性.即使是等压固结土体,在其后的偏压加载过程中,也会产生应力诱发各向异性.土体各向异性对其强度、变形及屈服面倾向都会产生影响.Wheeler弹塑性模型采用旋转硬化来描述土体的各向异性.在Wheeler模型的基础上,结合边界面理论,将Wheeler模型拓展为各向异性边界面模型.模型采用ABAQUS软件的UMAT子程序接口,通过隐式积分算法(图形返回算法)编程实现.采用本模型对高岭土三轴不排水剪切试验进行了模拟,并与试验结果作了对比验证.结果表明:模型能够合理描述具有初始各向异性土体的应力应变行为、孔压曲线及应力路径,并能反映偏压加载下的应力诱发各向异性;模型既可适用于模拟正常固结土,也适用于对中等超固结土的模拟. 展开更多
关键词 超固结土 土体各向异性 土体边界面模型 UMAT子程序 旋转硬化法则
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A novel algorithm for a rotation invariant template matching 被引量:1
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作者 LEI Ming ZHANG Guang-jun 《Optoelectronics Letters》 EI 2008年第5期379-383,共5页
A novel algorithm for a rotation invariant template matching is proposed when the fluctuating scope of the rotation angle is limited within the region of [-20°,20°]. The matching candidates are selected usin... A novel algorithm for a rotation invariant template matching is proposed when the fluctuating scope of the rotation angle is limited within the region of [-20°,20°]. The matching candidates are selected using a computationally low cost improved correlation algorithm. "AND" operation is adopted to reduce the computational cost. Therefore the algorithm improves the matching speed consumedly. The simulation results verify the efficiency of the proposed method. Moreover,when the size of reference image is fixed,the advantage of this time-saving algorithm is more obvious as the increase of the size of the real time image. The matching speed of the proposed method is over 20 times faster than the speed of the two-level pyramid decomposing accelerating method. 展开更多
关键词 运算法则 旋转 模板匹配 不变量
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Orthogonal transformation operation theorem of a spatial universal uniform rotating magnetic field and its application in capsule endoscopy 被引量:9
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作者 ZHANG YongShun YU ZiChun +2 位作者 YANG HuiYuan HUANG YunKui CHEN Jun 《Science China(Technological Sciences)》 SCIE EI CAS CSCD 2017年第6期854-864,共11页
According to the anti-phase sine current superposition theorem, the orientation, the magnetic flux density, the angular speed and the rotational direction of the spatial universal rotating magnetic field (SURMF) can... According to the anti-phase sine current superposition theorem, the orientation, the magnetic flux density, the angular speed and the rotational direction of the spatial universal rotating magnetic field (SURMF) can be controlled within the tri-axial orthogonal square Helmholtz coils (TOSHC). Nevertheless, three coupling direction angles of the normal vector of the SURMF in the Descartes coordinate system cannot be separately controlled, thus the adjustment of the orientation of the SURMF is difficult and the flexibility of the robotic posture control is restricted. For the dimension reduction and the decoupling of control variables, the orthogonal transformation operation theorem of the SURMF is proposed based on two independent rotation angular variables, which employs azimuth and altitude angles as two variables of the three-phase sine current superposition formula derived by the orthogonal rotation inverse transformation. Then the unique control rules of the orientation and the rotational direction of the SURMF are generalized in each spatial quadrant, thus the scanning of the normal vector of the SURMF along the horizontal or vertical direction can be achieved through changing only one variable, which simplifies the control process of the orientation of the SURMF greatly. To validate its feasibility and maneuverability, experiments were conducted in the animal intestine utilizing the innovative dual hemisphere capsule robot (DHCR) with active and passive modes. It was demonstrated that the posture adjustment and the steering rolling locomotion of the DHCR can be realized through single variable control, thus the orthogonal transformation operation theorem makes the control of the orientation of the SURMF convenient and flexible significantly. This breakthrough will lay a foundation for the human-machine interaction control of the SURMF. 展开更多
关键词 dual hemisphere capsule robot (DHCR) spatial universal rotating magnetic field (SURMF) orthogonal transformation operation variable decoupling
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