The above-knee intelligent bionic leg is very helpful to amputees in the area of rehabilitation medicine. This paper first introduces the functional demand of the above-knee prosthesis design. Then, the advantages of ...The above-knee intelligent bionic leg is very helpful to amputees in the area of rehabilitation medicine. This paper first introduces the functional demand of the above-knee prosthesis design. Then, the advantages of the four-bar link mechanism and the magneto-rheological （MR） damper are analyzed in detail. The fixed position of the MR damper is optimized and a virtual prototype of knee joint is given. In the end, the system model of kinematics, dynamics, and controller are given and a control experiment is performed. The control experiment indicates that the intelligent bionic leg with multi-axis knee is able to realize gait tracking of the amputee＇s healthy leg based on semi-active control of the MR damper.展开更多
探求鞭腿技术击打不同类型目标时因动作运用不当可能引发膝关节运动损伤的危险时刻。运用VICON System 3D运动采集系统,对10名优秀散打运动员鞭腿技术进行空击、击打脚靶、沙包时的运动轨迹进行采集,依据鞭打动作特点和下肢关节运动特征...探求鞭腿技术击打不同类型目标时因动作运用不当可能引发膝关节运动损伤的危险时刻。运用VICON System 3D运动采集系统,对10名优秀散打运动员鞭腿技术进行空击、击打脚靶、沙包时的运动轨迹进行采集,依据鞭打动作特点和下肢关节运动特征,将鞭腿动作划分为3个时刻、2个时段,对其在各时刻的动作速度、作用腿膝关节角度、角速度、力矩等运用VICON Nexus和Polygon分析软件进行处理。研究结果表明:作用腿膝关节屈伸、内收外展、回旋角度和角速度以及关节力矩等各方面均存在着显著性差异(P<0.05);鞭腿空击技术类型的动作速度相对较慢,击打时段膝关节角速度相对较快、伸展时段膝关节呈外旋、加速并过度伸展状态;击打脚靶类型的动作速度相对较快,伸展时段膝关节呈外旋伸展运动状态;击打沙包类型膝关节的各项力矩相对较大,伸展时段膝关节呈反方向运动状态。鞭腿的3种击打类型均存在引发膝关节运动损伤的危险时刻,建议运动员在训练和实战时遵循鞭腿技术动作的运动规律。展开更多
Since a self-elevating platform often works in water for a long time, the lattice leg is largely influenced by wave and current. The amplitude of leg joint stresses is a very important factor for the fatigue life of t...Since a self-elevating platform often works in water for a long time, the lattice leg is largely influenced by wave and current. The amplitude of leg joint stresses is a very important factor for the fatigue life of the platform. However, there are not many researches having been done on the mechanism and dynamic stress analysis of these leg joints. This paper focuses on the dynamic stress analysis and suppression methods of the leg joints of self-elevating platforms. Firstly, the dynamic stresses of the lattice leg joints are analyzed for a self-elevating platform by use of the 5th-order Stokes wave theory. Secondly, the axial and bending stresses are studied due to their large contributions to total stresses. And then, different joint types are considered and the leg-hull interface stiffness is analyzed for the improvement of the joint dynamic stress amplitude. Finally, some useful conclusions are drawn for the optimization design of the self-elevating platform.展开更多
Cruciform joints in ships are prone to fatigue damage and the determination of type of weld plays a significant role in thefatigue design of the joint. In this paper, the effect of weld geometry on fatigue failure of ...Cruciform joints in ships are prone to fatigue damage and the determination of type of weld plays a significant role in thefatigue design of the joint. In this paper, the effect of weld geometry on fatigue failure of load carrying cruciform joints inships is investigated using Effective Notch Stress (ENS) approach. A fictitious notch of 1 mm radius is introduced at theweld root and toe and fatigue stress is evaluated. The effect of weld leg length (l) and weld penetration depth (p) on ENS atweld root and toe are determined. The critical weld leg length (lcr) at which fatigue failure transitions from weld root toweld toe is investigated. An approximation formula for determination of the critical weld leg length considering weldpenetration depth (p) is proposed.展开更多
基金supported by China Postdoctoral Science Foundation(No. 20080441093)Key Laboratory Foundation of Liaoning Province(No. 2008S088)Postdoctoral Science Foundation of Northeastern University (No. 20080411)
文摘The above-knee intelligent bionic leg is very helpful to amputees in the area of rehabilitation medicine. This paper first introduces the functional demand of the above-knee prosthesis design. Then, the advantages of the four-bar link mechanism and the magneto-rheological （MR） damper are analyzed in detail. The fixed position of the MR damper is optimized and a virtual prototype of knee joint is given. In the end, the system model of kinematics, dynamics, and controller are given and a control experiment is performed. The control experiment indicates that the intelligent bionic leg with multi-axis knee is able to realize gait tracking of the amputee＇s healthy leg based on semi-active control of the MR damper.
文摘探求鞭腿技术击打不同类型目标时因动作运用不当可能引发膝关节运动损伤的危险时刻。运用VICON System 3D运动采集系统,对10名优秀散打运动员鞭腿技术进行空击、击打脚靶、沙包时的运动轨迹进行采集,依据鞭打动作特点和下肢关节运动特征,将鞭腿动作划分为3个时刻、2个时段,对其在各时刻的动作速度、作用腿膝关节角度、角速度、力矩等运用VICON Nexus和Polygon分析软件进行处理。研究结果表明:作用腿膝关节屈伸、内收外展、回旋角度和角速度以及关节力矩等各方面均存在着显著性差异(P<0.05);鞭腿空击技术类型的动作速度相对较慢,击打时段膝关节角速度相对较快、伸展时段膝关节呈外旋、加速并过度伸展状态;击打脚靶类型的动作速度相对较快,伸展时段膝关节呈外旋伸展运动状态;击打沙包类型膝关节的各项力矩相对较大,伸展时段膝关节呈反方向运动状态。鞭腿的3种击打类型均存在引发膝关节运动损伤的危险时刻,建议运动员在训练和实战时遵循鞭腿技术动作的运动规律。
基金supported by the Shanghai Science Foundation of Important Projects for Post Doctoral Research, China (Grant No. 09R21421600)
文摘Since a self-elevating platform often works in water for a long time, the lattice leg is largely influenced by wave and current. The amplitude of leg joint stresses is a very important factor for the fatigue life of the platform. However, there are not many researches having been done on the mechanism and dynamic stress analysis of these leg joints. This paper focuses on the dynamic stress analysis and suppression methods of the leg joints of self-elevating platforms. Firstly, the dynamic stresses of the lattice leg joints are analyzed for a self-elevating platform by use of the 5th-order Stokes wave theory. Secondly, the axial and bending stresses are studied due to their large contributions to total stresses. And then, different joint types are considered and the leg-hull interface stiffness is analyzed for the improvement of the joint dynamic stress amplitude. Finally, some useful conclusions are drawn for the optimization design of the self-elevating platform.
文摘Cruciform joints in ships are prone to fatigue damage and the determination of type of weld plays a significant role in thefatigue design of the joint. In this paper, the effect of weld geometry on fatigue failure of load carrying cruciform joints inships is investigated using Effective Notch Stress (ENS) approach. A fictitious notch of 1 mm radius is introduced at theweld root and toe and fatigue stress is evaluated. The effect of weld leg length (l) and weld penetration depth (p) on ENS atweld root and toe are determined. The critical weld leg length (lcr) at which fatigue failure transitions from weld root toweld toe is investigated. An approximation formula for determination of the critical weld leg length considering weldpenetration depth (p) is proposed.
