Amphibious salamanders often swing their waist to coordinate quadruped walking in order to improve their crawling speed. A robot with a swing waist joint, like an amphibious salamander, is used to mimic this locomotio...Amphibious salamanders often swing their waist to coordinate quadruped walking in order to improve their crawling speed. A robot with a swing waist joint, like an amphibious salamander, is used to mimic this locomotion.A control method is designed to allow the robot to maintain the rotational speed of its legs continuous and avoid impact between its legs and the ground. An analytical expression is established between the amplitude of the waist joint and the step length. Further, an optimization amplitude is obtained corresponding to the maximum stride. The simulation results based on automatic dynamic analysis of mechanical systems（ADAMS） and physical experiments verify the rationality and validity of this expression.展开更多
Passive dynamic walking has been developed as a possible explanation for the efficiency of the human gait. This paper presents a passive dynamic walking model with segmented feet, which makes the bipedal walking gait ...Passive dynamic walking has been developed as a possible explanation for the efficiency of the human gait. This paper presents a passive dynamic walking model with segmented feet, which makes the bipedal walking gait more close to natural human-like gait. The proposed model extends the simplest walking model with the addition of fiat feet and torsional spring based compliance on ankle joints and toe joints, to achieve stable walking on a slope driven by gravity. The push-off phase includes foot rotations around the toe joint and around the toe tip, which shows a great resemblance to human normal walking. This paper investigates the effects of the segmented foot structure on bipedal walking in simulations. The model achieves satisfactory walking results on even or uneven slopes.展开更多
Micromechanics aims mainly at establishing the quantitative relation between the macroscopic mechanical behavior and the microstructure of heterogeneous materials.
Vacuum roll cladding （VRC） was used to bond pure titanium （Ti） plate to a plain low carbon steel （Q345） with the aim of obtaining a high-quality Ti-steel clad plate. The effect of interfacial compound on the mie...Vacuum roll cladding （VRC） was used to bond pure titanium （Ti） plate to a plain low carbon steel （Q345） with the aim of obtaining a high-quality Ti-steel clad plate. The effect of interfacial compound on the mierostructure and mechanical properties of Ti-steel clad plate was studied by electron probe microanalysis, scanning electron microscopy, X-ray diffraction and shear test. The clad plates were heated at 850 ℃ for 120 min and welded at different levels of vacuum. The results indicated that the cracked zone of the bonded interface decreased significantly with the increase in the level of vacuum during welding. Welding at atmospheric pressure, the randomly distributed TiN damaged the continuity of TiC and the uniformly diffused region of Ti and Fe at the bonded interface, while welding in vacuum of 1 × 10^-2 Pa, maximum shear strength of 298 MPa was obtained because of the decrease in TiN content.展开更多
A stainless steel clad plate composed of stainless steel and carbon steel was prepared by vacuum hot rolling process, and its microstructure, especially the bonding interface, was evaluated using an optical microscope...A stainless steel clad plate composed of stainless steel and carbon steel was prepared by vacuum hot rolling process, and its microstructure, especially the bonding interface, was evaluated using an optical microscope, a scanning electron micro- scope and a transmission electron microscope （TEM）. The corresponding mechanical properties were also assessed by means of hardness and shear tests. The results showed a bonding interface formed between stainless steel and carbon steel, which was relatively straight in macroscope but serrated in microscope. Decarburization layer and carbon-enriched layer were distinguished at the side of carbon steel and stainless steel near the interface, respectively, which should be related to diffusion of carbon and alloying elements. The carbon-enriched layer could also be identified as a recombination region, whose microstructure was mainly recognized as martensite by TEM. Consequently, the hardness was the highest at this region. Furthermore, the result of shear test at the bonding interface showed that the shear strength was 395 MPa and the fracture mode was dominated as ductile fracture, indicating the bonding interface with good quality.展开更多
基金supported by the State Key Laboratory of Robotics and System (HIT) (SKLRS-2009-MS-09)the National Natural Science Foundation of China (NSFC) (Grants 61503008, 51575005)the China Postdoctoral Science Foundation (Grant 2015M570013)
文摘Amphibious salamanders often swing their waist to coordinate quadruped walking in order to improve their crawling speed. A robot with a swing waist joint, like an amphibious salamander, is used to mimic this locomotion.A control method is designed to allow the robot to maintain the rotational speed of its legs continuous and avoid impact between its legs and the ground. An analytical expression is established between the amplitude of the waist joint and the step length. Further, an optimization amplitude is obtained corresponding to the maximum stride. The simulation results based on automatic dynamic analysis of mechanical systems（ADAMS） and physical experiments verify the rationality and validity of this expression.
基金supported by the National Natural Science Foundation of China (61005082, 61020106005)Doctoral Fund of Ministry of Education of China (20100001120005)+1 种基金PKU-Biomedical Engineering Join Seed Grant 2012the 985 Project of PekingUniversity (3J0865600)
文摘Passive dynamic walking has been developed as a possible explanation for the efficiency of the human gait. This paper presents a passive dynamic walking model with segmented feet, which makes the bipedal walking gait more close to natural human-like gait. The proposed model extends the simplest walking model with the addition of fiat feet and torsional spring based compliance on ankle joints and toe joints, to achieve stable walking on a slope driven by gravity. The push-off phase includes foot rotations around the toe joint and around the toe tip, which shows a great resemblance to human normal walking. This paper investigates the effects of the segmented foot structure on bipedal walking in simulations. The model achieves satisfactory walking results on even or uneven slopes.
文摘Micromechanics aims mainly at establishing the quantitative relation between the macroscopic mechanical behavior and the microstructure of heterogeneous materials.
文摘Vacuum roll cladding （VRC） was used to bond pure titanium （Ti） plate to a plain low carbon steel （Q345） with the aim of obtaining a high-quality Ti-steel clad plate. The effect of interfacial compound on the mierostructure and mechanical properties of Ti-steel clad plate was studied by electron probe microanalysis, scanning electron microscopy, X-ray diffraction and shear test. The clad plates were heated at 850 ℃ for 120 min and welded at different levels of vacuum. The results indicated that the cracked zone of the bonded interface decreased significantly with the increase in the level of vacuum during welding. Welding at atmospheric pressure, the randomly distributed TiN damaged the continuity of TiC and the uniformly diffused region of Ti and Fe at the bonded interface, while welding in vacuum of 1 × 10^-2 Pa, maximum shear strength of 298 MPa was obtained because of the decrease in TiN content.
文摘A stainless steel clad plate composed of stainless steel and carbon steel was prepared by vacuum hot rolling process, and its microstructure, especially the bonding interface, was evaluated using an optical microscope, a scanning electron micro- scope and a transmission electron microscope （TEM）. The corresponding mechanical properties were also assessed by means of hardness and shear tests. The results showed a bonding interface formed between stainless steel and carbon steel, which was relatively straight in macroscope but serrated in microscope. Decarburization layer and carbon-enriched layer were distinguished at the side of carbon steel and stainless steel near the interface, respectively, which should be related to diffusion of carbon and alloying elements. The carbon-enriched layer could also be identified as a recombination region, whose microstructure was mainly recognized as martensite by TEM. Consequently, the hardness was the highest at this region. Furthermore, the result of shear test at the bonding interface showed that the shear strength was 395 MPa and the fracture mode was dominated as ductile fracture, indicating the bonding interface with good quality.
