For the local catenary path of yarn in steady motion fre-quently encountered in textile processing,this paper studiesthe mathematical expression of its geometrical configurationand tension variation,as well as the cur...For the local catenary path of yarn in steady motion fre-quently encountered in textile processing,this paper studiesthe mathematical expression of its geometrical configurationand tension variation,as well as the curve inclination angleand its maximum suspending deflection.The final math-ematical equations and graphical curves are all presented indimensionless forms,as they are more general and universalthan dimensional expressions and graphs.On the otherhand,we can also find out the catenary yarn tension fromexperimentally measured geometrical parameters by calcula-tions based on these graphs or mathematical expressions asgiven in the paper.展开更多
In this paper,the vector equation of a generaliseddoubly wound helix was derived.Treloar’s pliedyarn geometry could be obtained as a special case ofthe generalised doubly wound helix.The shortest fi-bre length around...In this paper,the vector equation of a generaliseddoubly wound helix was derived.Treloar’s pliedyarn geometry could be obtained as a special case ofthe generalised doubly wound helix.The shortest fi-bre length around the surface of a helical tube(formed by fibre helices)was determined by apply-ing variational principles.The fibre length as calcu-lated by using Treloar’s geometry was compared in-directly with the shortest possible fibre length at dif-ferent levels of yarn deformation when some of Tre-loar’s rigid geometrical constraints were relaxed.Anew idea based on non-concentric circles was intro-duced to approximate the fibre helix movement in atwo-ply yarn.A torsional model of two-ply yarnwas developed and the theoretical predictions werecompared with some preliminary experimental re-sults.展开更多
为了提高直捻机上纱机械臂的避障路径规划效率,提出一种动态目标圆采样结合回归机制的改进型双向快速扩展随机树算法(Dynamic-target-circle Sampling and Regression mechanism Bidirectional Rapidly-exploring Random Trees,DSRB-RRT...为了提高直捻机上纱机械臂的避障路径规划效率,提出一种动态目标圆采样结合回归机制的改进型双向快速扩展随机树算法(Dynamic-target-circle Sampling and Regression mechanism Bidirectional Rapidly-exploring Random Trees,DSRB-RRT)。为解决随机树盲目采样问题,提出了一种动态目标圆采样法,引导随机树在以目标为圆心的动态圆区域内进行采样;为解决随机树拓展速度慢,提出了一种变步长变概率法,根据障碍物信息自行改变拓展步长和偏置概率,加快随机树收敛;引入了回归机制防止随机树在区域内过度采样;算法生成路径后,裁剪路径中冗余节点来缩短路径长度,并用三次B样条曲线平滑优化路径。仿真结果表明,DSRB-RRT算法相比于加入目标偏置的RRT、BI-RRT和GS-RRT在不同障碍场景下的收敛效率更高,平均路径更短。在ROS系统中对上纱机械臂进行仿真,验证了DSRB-RRT算法的有效性,可以提高机械臂路径规划效率。展开更多
针对筒子纱搬运过程中存在纱线架、放置平台、其他筒子纱等多障碍物的环境下,传统的目标偏置RRT容易陷入局部最优的问题,提出一种改进的RRT(rapidly-exploring random tree)算法。通过几何包络法建立碰撞检测模型,并添加距离系数g,使机...针对筒子纱搬运过程中存在纱线架、放置平台、其他筒子纱等多障碍物的环境下,传统的目标偏置RRT容易陷入局部最优的问题,提出一种改进的RRT(rapidly-exploring random tree)算法。通过几何包络法建立碰撞检测模型,并添加距离系数g,使机械臂末端与障碍物保持安全距离;提出随机动作选择策略,使树每一次扩展前对扩展动作进行选择;提出弱化目标偏置策略,根据X goal相对于X near和X rand连线的位置,对扩展方向进行偏置;根据垂距限值法和三次样条插值对初始路径处理,得到一条平滑路径。通过与RRT算法、M-RRT算法、添加引力系数的RRT算法和改进的RRT算法仿真对比,路径长度方面最大下降了23.3%,时间方面最大下降了82.5%,并始终与障碍物保持50 mm以上的距离。结果表明该算法提升了机械臂搬运的效率和安全性。展开更多
文摘For the local catenary path of yarn in steady motion fre-quently encountered in textile processing,this paper studiesthe mathematical expression of its geometrical configurationand tension variation,as well as the curve inclination angleand its maximum suspending deflection.The final math-ematical equations and graphical curves are all presented indimensionless forms,as they are more general and universalthan dimensional expressions and graphs.On the otherhand,we can also find out the catenary yarn tension fromexperimentally measured geometrical parameters by calcula-tions based on these graphs or mathematical expressions asgiven in the paper.
文摘In this paper,the vector equation of a generaliseddoubly wound helix was derived.Treloar’s pliedyarn geometry could be obtained as a special case ofthe generalised doubly wound helix.The shortest fi-bre length around the surface of a helical tube(formed by fibre helices)was determined by apply-ing variational principles.The fibre length as calcu-lated by using Treloar’s geometry was compared in-directly with the shortest possible fibre length at dif-ferent levels of yarn deformation when some of Tre-loar’s rigid geometrical constraints were relaxed.Anew idea based on non-concentric circles was intro-duced to approximate the fibre helix movement in atwo-ply yarn.A torsional model of two-ply yarnwas developed and the theoretical predictions werecompared with some preliminary experimental re-sults.
文摘为了提高直捻机上纱机械臂的避障路径规划效率,提出一种动态目标圆采样结合回归机制的改进型双向快速扩展随机树算法(Dynamic-target-circle Sampling and Regression mechanism Bidirectional Rapidly-exploring Random Trees,DSRB-RRT)。为解决随机树盲目采样问题,提出了一种动态目标圆采样法,引导随机树在以目标为圆心的动态圆区域内进行采样;为解决随机树拓展速度慢,提出了一种变步长变概率法,根据障碍物信息自行改变拓展步长和偏置概率,加快随机树收敛;引入了回归机制防止随机树在区域内过度采样;算法生成路径后,裁剪路径中冗余节点来缩短路径长度,并用三次B样条曲线平滑优化路径。仿真结果表明,DSRB-RRT算法相比于加入目标偏置的RRT、BI-RRT和GS-RRT在不同障碍场景下的收敛效率更高,平均路径更短。在ROS系统中对上纱机械臂进行仿真,验证了DSRB-RRT算法的有效性,可以提高机械臂路径规划效率。
