针对大型提花机承受载荷时易发生弯曲变形导致拉刀提升高度不够,使直针钩子无法被电磁装置吸附的问题,首先对拉刀结构、载荷以及曲柄滑块驱动机构运动情况进行分析。其次,基于变截面梁理论和结构优化的方法,采用非均匀有理B样条(Non-Uni...针对大型提花机承受载荷时易发生弯曲变形导致拉刀提升高度不够,使直针钩子无法被电磁装置吸附的问题,首先对拉刀结构、载荷以及曲柄滑块驱动机构运动情况进行分析。其次,基于变截面梁理论和结构优化的方法,采用非均匀有理B样条(Non-Uniform Rational B-Splines,NURBS)曲线表达拉刀侧面、截面形状,通过数值方法计算拉刀截面惯性矩函数、弯矩函数,并通过有限差分法计算拉刀变形量。通过有限元方法(Finite Element Method,FEM)、等效为等截面梁的方法对挠度计算方法进行验证,误差在10%以内。最后,以最小质量为目标,采用原-对偶不可行内点算法对拉刀结构进行优化。优化结果表明,相较于优化初值模型,拉刀质量减小约17%,最大挠度减小约2667%。展开更多
Methods of digital human modeling have been developed and utilized to reflect human shape features.However,most of published works focused on dynamic visualization or fashion design,instead of high-accuracy modeling,w...Methods of digital human modeling have been developed and utilized to reflect human shape features.However,most of published works focused on dynamic visualization or fashion design,instead of high-accuracy modeling,which was strongly demanded by medical or rehabilitation scenarios.Prior to a high-accuracy modeling of human legs based on non-uniform rational B-splines(NURBS),the method of extracting the required quasi-grid network of feature points for human legs is presented in this work.Given the 3 D scanned human body,the leg is firstly segmented and put in standardized position.Then re-sampling of the leg is conducted via a set of equidistant cross sections.Through analysis of leg circumferences and circumferential curvature,the characteristic sections of the leg as well as the characteristic points on the sections are then identified according to the human anatomy and shape features.The obtained collection can be arranged to form a grid of data points for knots calculation and high-accuracy shape reconstruction in future work.展开更多
Modifying the knots of a B-spline curve, the shape of the curve will be changed. In this paper, we present the effect of the symmetric alteration of four knots of the B-spline and the NURBS surfaces, i.e., symmetrical...Modifying the knots of a B-spline curve, the shape of the curve will be changed. In this paper, we present the effect of the symmetric alteration of four knots of the B-spline and the NURBS surfaces, i.e., symmetrical alteration of the knots of surface, the extended paths of points of the surface will converge to a point which should be expressed with several control points. This theory can be used in the constrained shape modification of B-spline and NURBS surfaces.展开更多
文摘针对大型提花机承受载荷时易发生弯曲变形导致拉刀提升高度不够,使直针钩子无法被电磁装置吸附的问题,首先对拉刀结构、载荷以及曲柄滑块驱动机构运动情况进行分析。其次,基于变截面梁理论和结构优化的方法,采用非均匀有理B样条(Non-Uniform Rational B-Splines,NURBS)曲线表达拉刀侧面、截面形状,通过数值方法计算拉刀截面惯性矩函数、弯矩函数,并通过有限差分法计算拉刀变形量。通过有限元方法(Finite Element Method,FEM)、等效为等截面梁的方法对挠度计算方法进行验证,误差在10%以内。最后,以最小质量为目标,采用原-对偶不可行内点算法对拉刀结构进行优化。优化结果表明,相较于优化初值模型,拉刀质量减小约17%,最大挠度减小约2667%。
基金National Natural Science Foundation of China(Nos.12002085 and 51603039)Shanghai Pujiang Program,China(No.19PC002)+1 种基金Fundamental Research Funds for the Central Universities,China(No.2232019D3-58)Initial Research Funds for Young Teachers of Donghua University,China(No.104-07-0053088)。
文摘Methods of digital human modeling have been developed and utilized to reflect human shape features.However,most of published works focused on dynamic visualization or fashion design,instead of high-accuracy modeling,which was strongly demanded by medical or rehabilitation scenarios.Prior to a high-accuracy modeling of human legs based on non-uniform rational B-splines(NURBS),the method of extracting the required quasi-grid network of feature points for human legs is presented in this work.Given the 3 D scanned human body,the leg is firstly segmented and put in standardized position.Then re-sampling of the leg is conducted via a set of equidistant cross sections.Through analysis of leg circumferences and circumferential curvature,the characteristic sections of the leg as well as the characteristic points on the sections are then identified according to the human anatomy and shape features.The obtained collection can be arranged to form a grid of data points for knots calculation and high-accuracy shape reconstruction in future work.
基金Project supported by the National Natural Science Foundation of China (No. 60473130) and the National Basic Research Program (973) of China (No. G2004CB318000)
文摘Modifying the knots of a B-spline curve, the shape of the curve will be changed. In this paper, we present the effect of the symmetric alteration of four knots of the B-spline and the NURBS surfaces, i.e., symmetrical alteration of the knots of surface, the extended paths of points of the surface will converge to a point which should be expressed with several control points. This theory can be used in the constrained shape modification of B-spline and NURBS surfaces.
