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Nowadays, the existing walking wheels still have problems with the wheel-legs structure and the traction trafficability on the loose sand. It is commonly believed that African ostrich (Struthio camelus) is a kind of bipedal species with superior running performance on the sandy environment. Being enlightened by this, four bionic walking wheels (herringbone wheel, in-line wheel, V-shaped wheel and combination wheel) were designed and tested by imitating the structure and posture of ostrich’s feet travelling on sand. The results showed that when the wheel load was 20, 30 and 50N respectively and the slip ratio was less than 35%, the herringbone wheel had better traction trafficability than that of other wheels. When the wheel load was 30, 50 and 70N and the slip ratio was more than 35%, the in-line wheel had better performance than that of other wheels. It was shown in this thesis that the bionic walking wheels designed with the multi-posture wheel-legs and the simple structure could reduce the soil resistance and the disturbance to sand, thereby achieving a superior performance of traveling on sand. In addition, a new idea and research method for designing of walking mechanism on soft terrain has been provided in this thesis. 相似文献
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“Nondissociative” chain walking is a mechanism where an alkylmetal species undergoes rapid β-hydride elimination and reinsertion to move the metal center along the alkyl chain without dissociating an alkene intermediate during the migration process. This digest summarizes the unique characteristics of the nondissociative chain walking mechanism compared to the stepwise alkene isomerization mechanism and their use in catalytic organic synthesis. 相似文献
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Agnideep Das Jules Schleinitz Lydia Karmazin Bruno Vincent Dr. Nolwenn Le Breton Guillaume Rogez Dr. Aurélie Guenet Prof. Sylvie Choua Dr. Laurence Grimaud Prof. Marine Desage-El Murr 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(35):e202200596
Mechanisms combining organic radicals and metallic intermediates hold strong potential in homogeneous catalysis. Such activation modes require careful optimization of two interconnected processes: one for the generation of radicals and one for their productive integration towards the final product. We report that a bioinspired polymetallic nickel complex can combine ligand- and metal-centered reactivities to perform fast hydrosilylation of alkenes under mild conditions through an unusual dual radical- and metal-based mechanism. This earth-abundant polymetallic complex incorporating a catechol-alloxazine motif as redox-active ligand operates at low catalyst loading (0.25 mol%) and generates silyl radicals and a nickel-hydride intermediate through a hydrogen atom transfer (HAT) step. Evidence of an isomerization sequence enabling terminal hydrosilylation of internal alkenes points towards the involvement of the nickel-hydride species in chain walking. This single catalyst promotes a hybrid pathway by combining synergistically ligand and metal participation in both inner- and outer- sphere processes. 相似文献
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The passive dynamic walking is a new concept of biped walking. Researchers have been working on this area with both theoretical analysis and experimental analysis ever since McGeer. This paper presents our compass-like passive walking model with a new set of testing system. Two gyroscopes are used for measuring the angles of two legs, and ten FlexiForce sensors are used for measuring the contact forces on the feet. We got the experimental data on the passive walking process with the validated testing system. A great emphasis was put on the contact process between the feet and the slope. The contact process of the stance leg was divided into four sections, and differences between the real testing contact process and the classic analytical contact process with no bouncing and slipping were summarized. 相似文献
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由人类步行的生物力学研究得到启发,在被动双足步行机器人的髋关节处引入了扭簧,并通过仿真和试验研究了弹簧刚度对被动步行稳定性的影响.在仿真中,用胞映射方法计算被动步行机器人的吸引盆,并用吸引盆来衡量机器人的稳定性,研究了弹簧刚度对被动步行吸引盆大小的影响. 仿真结果表明, 吸引盆随着弹簧刚度的增大而增大. 在试验中,使机器人在各弹簧刚度参数下沿斜坡向下行走100次,记录下行走到头的次数作为稳定性的度量. 试验结果表明, 存在一个大小适中的弹簧刚度使机器人稳定性最大. 对弹簧提高机器人稳定性的原因进行了分析,对造成仿真与试验之间差异的原因进行了分析. 相似文献
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研究了变刚度半被动双足机器人行走控制问题。采用仿人的行走控制策略,使用变刚度双足弹簧负载倒立摆模型,利用模型自稳定性,在双支撑阶段调整后腿刚度使机器人的能量保持在期望能量附近,在单支撑阶段调整摆动腿落地位置控制质点的高度和前向速度。仿真结果表明:本文采用的控制策略可以实现双足机器人在水平面上的稳定行走,无扰动时可以使机器人实现零输入的被动周期行走,有外部扰动时腿部变刚度控制可使机器人总能量恢复平衡并重新进入稳态行走,控制系统具有鲁棒性。 相似文献
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双足机器人动态步行稳定的判据 总被引:2,自引:0,他引:2
本文以七刚体十二自由度双足步行机器人为模型,推导了动态步行稳定的判别条件.这一判别条件可用于校核双足步行机器人运动规划的可行性,也对调整修正运动规划有指导作用. 相似文献
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以二氯化镍为原料制得配合物(DME)Ni Cl2(1);以2,6-二异丙基苯胺和丁二酮为原料,经缩合反应制得α-二亚胺配体(2);1与2经络合反应合成了一种用于乙烯齐聚制备超支化聚乙烯的新型链行走催化剂(3),其结构经IR,XRD和元素分析表征。以乙烯齐聚为探针反应,考察了助催化剂,反应温度和反应时间对3催化活性的影响。结果表明:在较优反应条件[Al Et30.14 mol,n(Al)∶n(Ni)=600,于20℃反应0.5 h]下,3催化活性为2.5×106g PE·(mol·Ni·h·MPa)-1。齐聚产物为支化聚乙烯,部分支链中碳原子数大于4。 相似文献