Wearable exoskeleton is a wearable device to enhance human ability,however,it is too heavy because of some constraints,such as material,structure and energy storage battery. Thus it brings fatigue to people after a lo...Wearable exoskeleton is a wearable device to enhance human ability,however,it is too heavy because of some constraints,such as material,structure and energy storage battery. Thus it brings fatigue to people after a long period of wearing. The research aims at optimizing shoulder fatigue and improving wearing comfort by means of changing the device-body contact material. After analyzing the current wearable exoskeletons ' weight, a standard load was set and a wearable exoskeleton was designed that could switch the weight. The experiment chose movement stability and change of cumulative pressure upon shoulder as the indexes of fatigue. The indexes were measured and analyzed before and after changing the contact material to memory foam with the standard load. The results showed promotion in action stability and obvious decrease in cumulative pressure upon shoulder.The experiment proves that the using of memory foam in wearable exoskeleton has evident effects on optimizing shoulder fatigue with load,promoting movement stability and wearing comfort.展开更多
Through dimension analysis, an almost analytical model for the maximum diffusion induced stress（DIS）and critical temperature（or concentration） difference at which cracks begin to initiate in the diffusion process ...Through dimension analysis, an almost analytical model for the maximum diffusion induced stress（DIS）and critical temperature（or concentration） difference at which cracks begin to initiate in the diffusion process is developed. It interestingly predicts that the spacing of diffusioninduced cracks is constant, independent of the thickness of specimen and the temperature difference. These conclusions are validated by our thermal shock experiments on alumina plates. Furthermore, the proposed model can interpret observed hierarchical crack patterns for high temperature jump cases, and a three-stage relation between the residual strength and the temperature difference. The prediction for crack spacing can guide the biomimetic thermal-shockfailure proof design, in which the hard platelets smaller than the predicted diffusion induced by constant crack-spacing are embedded in a soft matrix, and, therefore, no fracture will happen. This may guide the design of the thermal protection system and the lithium ion battery. Finally we present the maximum normalized DISes for various geometry and boundary conditions by single-variable curves for the stressindependent diffusion process and two-variable contour plots for the stress-dependent diffusion process, which can provideengineers and materialists a simple and easy way to quickly evaluate the reliability of related materials and devices.展开更多
基金the Fundamental Research Funds for the Central Universities,China(No.16D110301)Research Innovation Project of Shanghai Municipal Education Commission,China(No.201506000008)Science and Technology Guidance Project of Chinese Textile Industry Association(No.2015109)
文摘Wearable exoskeleton is a wearable device to enhance human ability,however,it is too heavy because of some constraints,such as material,structure and energy storage battery. Thus it brings fatigue to people after a long period of wearing. The research aims at optimizing shoulder fatigue and improving wearing comfort by means of changing the device-body contact material. After analyzing the current wearable exoskeletons ' weight, a standard load was set and a wearable exoskeleton was designed that could switch the weight. The experiment chose movement stability and change of cumulative pressure upon shoulder as the indexes of fatigue. The indexes were measured and analyzed before and after changing the contact material to memory foam with the standard load. The results showed promotion in action stability and obvious decrease in cumulative pressure upon shoulder.The experiment proves that the using of memory foam in wearable exoskeleton has evident effects on optimizing shoulder fatigue with load,promoting movement stability and wearing comfort.
基金support from the National Natural Science Foundation of China(Grants.11372158,11425208,and 51232004)Tsinghua University Initiative Scientific Research Program(Grant.2011Z02173)
文摘Through dimension analysis, an almost analytical model for the maximum diffusion induced stress（DIS）and critical temperature（or concentration） difference at which cracks begin to initiate in the diffusion process is developed. It interestingly predicts that the spacing of diffusioninduced cracks is constant, independent of the thickness of specimen and the temperature difference. These conclusions are validated by our thermal shock experiments on alumina plates. Furthermore, the proposed model can interpret observed hierarchical crack patterns for high temperature jump cases, and a three-stage relation between the residual strength and the temperature difference. The prediction for crack spacing can guide the biomimetic thermal-shockfailure proof design, in which the hard platelets smaller than the predicted diffusion induced by constant crack-spacing are embedded in a soft matrix, and, therefore, no fracture will happen. This may guide the design of the thermal protection system and the lithium ion battery. Finally we present the maximum normalized DISes for various geometry and boundary conditions by single-variable curves for the stressindependent diffusion process and two-variable contour plots for the stress-dependent diffusion process, which can provideengineers and materialists a simple and easy way to quickly evaluate the reliability of related materials and devices.
