面向松软地面仿蟹步行足研究

发布时间：2018-06-26 03:12

本文选题：仿生 + 中华绒螯蟹　；参考：《吉林大学》2017年博士论文

【摘要】：与轮式车辆相比,腿式步行机构在松软非结构地面有不可替代的优势,发展潜力巨大,仿生技术的兴起为腿式步行机构的研制开辟了新的方向。中华绒螯蟹具有优秀的运动能力,不仅能长途迁徙,还能自由穿梭于泥沼、湿地等松软地面环境而不受困,因此,中华绒螯蟹的运动特性及步足指节结构为腿式步行机构及其触土部件——步行足的设计提供生物模版和仿生依据。运用三维运动观测系统采集中华绒螯蟹在平地、斜坡、沙地三种地面的运动学及动力学参数,通过图像分析步足关节角、切土角和入土角的变化,比较中华绒螯蟹在不同地面环境的行走姿态差异,讨论各步足在运动中的作用。结果发现中华绒螯蟹在斜坡行走时的质心速度与加速度最小,负荷因子最大,步足切土角波动大,入土角较小,证明中华绒螯蟹在斜坡行走步伐缓慢,支撑时间更多,需不断变换和调整姿态,以避免失衡;中华绒螯蟹在沙地行走时步足长节-腕节关节角小于平地和斜坡两种硬地面,切土角值最小,入土角分布集中,说明采用小步幅、高步频、降低身体重心的方式,防止下陷受困。中华绒螯蟹运动时第2、3对步足长节-腕节关节角最大,为主要步行足,第1对步足还起支撑作用,第4对步足较少主动参与行走,对行走的作用较小。借助体视显微镜、EDS、XRD、FTIR检测及扫描电镜(SEM)等手段对中华绒螯蟹第2、3对步足的指节进行生物学研究,分别从材料组成和微观结构,并结合三点弯曲试验揭示指节轻质高强的特性。结果表明中华绒螯蟹步足指节的主要元素组成包括C、Ca、O和少量其他元素,几丁质(糖类)和蛋白质是指节外骨骼中的主要有机物成分,包含的主要无机物成分为CaCO3,多以方解石为主要晶体结构形式,且晶化程度良好,还有部分以无定形碳酸钙的形式存在;中华绒螯蟹指节的外骨骼结构为多层结构,包括上表皮、外表皮和内表皮三层。外表皮厚度不均匀,与指节表面的凹凸有关,内表皮呈现出Bouligand结构特点:若干独立的纤维束排列组成蛋白纤维层,各纤维层间有一定的螺旋角,整体构成“扭转-胶合板”的形式。纤维层平面规则分布很多孔道,内部含有螺旋形的孔小管,用于输送营养物质到各部位,并可增加内表皮层的韧性;指节尖端的外表皮层表现出高度钙化,增加了指节尖端的表面强度、提高抗冲击能力和耐磨性。三点弯曲试验结果显示,湿润指节试样的韧性材料特征明显,且弯曲载荷较大,说明指节的力学特性受水合作用的影响较大。使用扫描电镜观察中华绒螯蟹的指节截面结构特征,建立仿生模型,提取几何参数,运用工程仿生方法设计4种仿生步行足与圆柱足进行比较,在6种土壤条件下进行土槽试验。结果表明,在试验条件下,仿生步行足的入土能耗和出土能耗均低于圆柱足,沟纹仿生结构有利于提高步行足推进性能;影响步行足推进性能的主要因素是土壤的含水率,其次为入土深度和速度,土壤粒径对步行足推进性能无显著影响;当垂直负载相同时,锥形仿生足的推进性能比圆柱足更好。综合分析步行机构的完整运动过程,仿生步行足的表现优于圆柱足,运动灵活轻便,提高牵引力,适用于轻质轻载小型步行机构。步行足作为触土部件在土壤中运动时受到的水平阻力随速度增加而小幅线性增大,与入土深度的2次方成正比;圆锥触土部件水平阻力随锥角增大呈2次方非线性增加;结合土壤阻力估算式,引入锥角和速度参数,建立适用于锥形变截面与圆柱触土部件的水平阻力预测模型,能够较准确地预测和评估触土部件在松软地面的推进性能。以中华绒螯蟹为生物原型,简化步足关节,设计六足仿蟹步行机构。其中腿部采用闭链式连杆结构,以齿轮机构和连杆机构为主要传动形式,利用凸轮机构实现步行腿的交替运动,通过对虚拟样机的仿真分析,步行机构各步行腿的负荷因子为54.21%~74.36%,且步行腿空回时间短,有较好的运动连续性与稳定性。对仿蟹步行机构在3种不同粗糙度地面进行通过性试验,得到仿蟹步行机构在粗糙地面的稳定性高于光滑地面。以减小位移差值、加速度最大值、增加平均速度、抬腿高度等为目标,优化仿蟹步行机构腿部杆件EF、FG和GH的长度,通过寻优求解,得到杆件的长度最优值为别为EF=31.6mm、FG=36mm、GH=115mm,优化后的综合目标值比初始值降低11.06%,仿蟹步行机构的整体性能有效提升。选择并确定仿生步行足类型和尺寸,与仿蟹步行机构装配,在干沙和湿沙两种介质中进行通过性试验,采用三维运动观测和分析系统测量仿蟹步行机构的通过性能。结果表明,在试验条件下,与原样机A相比,仿生足15°安装的样机B与仿生足0°安装的样机C的最大牵引负载较高,具有较好的牵引性能,当牵引负载增大,步行机构的平均运动速度随之线性下降,垂直负载对平均运动速度的影响较小。结合牵引性能,对仿蟹步行机构的运动图像解析,当牵引负载一定时,在相同垂直负载下,3种样机步行足的沉陷量大小为:样机A样机B样机C,安装仿生步行足的仿蟹步行机构的承载能力较强,在运动中可减少入土和出土能耗,提高运动效率,比原样机具有更好的松软地面通过性能。步行足的安装角度对仿蟹步行机构的性能有影响,仿生步行足与腿部杆以15°安装时,仿蟹步行机构的牵引性能、承载能力和通过性能优于步行足0°安装的步行机构。
[Abstract]:Compared with wheeled vehicles, the leg walking mechanism has an irreplaceable advantage in the soft and unstructured ground and has great potential for development. The rise of bionic technology has opened up a new direction for the development of leg walking mechanism. The Chinese mitten crab has excellent sports ability, not only can migrate long distance, but also freely shuttle in the soft ground ring, such as marsh, wetland and so on. Therefore, the motion characteristics of the Eriocheir sinensis and the foot knuckle structure provide the biometric and bionic basis for the leg walking mechanism and its touching part, the design of the foot foot, and the kinematic and dynamic parameters of the three kinds of ground surface of the Eriocheir sinensis in flat, slope and sandy land are collected by the three-dimensional motion observation system. The difference in walking posture of Eriocheir sinensis in different ground environment is compared, and the effect of foot on the movement is discussed. The results show that the centroid velocity and acceleration of the Chinese mitten crab on the slope are the smallest, the load is the largest, the foot cutting angle fluctuates greatly, and the angle of the earth is smaller. The Chinese Mitten Crab (Eriocheir sinensis) walks slowly on the slope and supports more time. It needs to be constantly transformed and adjusted to avoid unbalance. The long joint angle of the Eriocheir sinensis is less than the two kinds of hard ground on the ground and slope when walking in the sand. The angle of the soil cutting is the smallest and the angle of the earth is distributed. It shows that the small step, the high step frequency and the weight of the body are used to reduce the weight of the body. 2,3 of Eriocheir sinensis has the largest joint angle of the foot long joint and the wrist joint in the movement of the Chinese mitten crab. It is the main walking foot. The first pairs of feet also support the foot. The fourth pairs of feet are less active and have less action on walking. With the help of stereoscopic microscope, EDS, XRD, FTIR detection and scanning electron microscopy (SEM), the Chinese mitter is used to treat the Chinese mitten Eriocheir. The biological study of crabs 2,3 to the foot of the foot, respectively from the material composition and microstructure, and combined with the three point bending test to reveal the characteristics of the light and high strength of the knuckle. The results show that the main elements of the step foot knuckles of Eriocheir sinensis include C, Ca, O and a small amount of other elements, and the chitin (saccharide) and protein are the main elements in the exoskeleton of the phalanx. The main composition of the organic matter is CaCO3, mostly with calcite as the main crystal structure, and the crystallization degree is good, and some of them exist in the form of amorphous calcium carbonate; the exoskeleton structure of the Eriocheir sinensis's knuckle is multilayer structure, including the upper epidermis, the outer skin and the inner epidermis. The skin thickness is not uniform, and the skin thickness is not uniform. The surface of the knuckle is related to the concave and convex surface, and the inner epidermis is characterized by Bouligand structure: a number of independent fiber bundles arranged in a protein fiber layer, a certain spiral angle between each layer of fiber, and the whole form of "torsional plywood". The fibrous layer is regularly distributed in many channels, and the inner part contains a spiral orifice, which is used to transport nutrients. To each part, the toughness of the inner epidermis can be increased; the surface cortex at the tip of the phalanx shows a high calcification, increases the surface strength of the knuckle tip, improves the impact resistance and wear resistance. The three point bending test results show that the ductile material of the humid knuckle specimen is characterized by obvious characteristics and the bending load is larger, indicating that the mechanical properties of the knuckle are affected by water. The influence of cooperation is great. Using scanning electron microscope to observe the structural characteristics of the cross section of Eriocheir sinensis, establish a bionic model, extract geometric parameters, use engineering bionic method to compare 4 kinds of bionic feet with cylindrical feet, and carry out soil grooves under 6 soil conditions. The results show that under the test conditions, the bionic walking foot is entered. The soil energy consumption and unearthed energy consumption are lower than the cylindrical foot, the furrow bionic structure is beneficial to improve the walking foot propulsion performance. The main factors affecting the walking foot propulsion performance are soil moisture content, followed by soil depth and velocity, and the soil particle size has no significant influence on the walking foot propulsion performance; when the vertical load is the same, the propelling of the conical bionic foot is the same. It is better than a cylindrical foot. The comprehensive analysis of the complete motion process of the walking mechanism, the performance of the bionic walking foot is better than the cylindrical foot, the movement is flexible and light, the traction is improved, and the walking foot is applied to the light weight and light load small walking mechanism. The horizontal resistance of the 2 depth is proportional to the depth of the cone, and the horizontal resistance of the conical soil component increases with the increase of the 2 times of the cone angle, and the cone angle and velocity parameters are introduced in combination with the soil resistance estimation formula, and the horizontal resistance prediction model suitable for the conical variable section and the cylindrical contact element can be established. It can accurately predict and evaluate the push of the contact parts on the soft ground. Taking the Eriocheir sinensis as the biological prototype and simplifying the foot foot joint and designing the six foot crab walking mechanism, the leg uses the closed chain link structure, the gear mechanism and the connecting rod mechanism as the main transmission form, and the alternating motion of the walking leg is realized by the cam mechanism. Through the simulation and analysis of the virtual prototype, the walking legs are all walking legs. The load factor is 54.21%~74.36%, and the walking leg time is short, and it has better motion continuity and stability. The stability of the crab walking mechanism on 3 different roughness ground is tested. The stability of the crab walking mechanism in the rough ground is higher than that of the smooth ground. The length of leg members EF, FG and GH of the walking mechanism of the crab walking mechanism is optimized. The optimum value of the length of the rod is not EF=31.6mm, FG=36mm, GH=115mm, and the overall target value after optimization is 11.06% lower than the initial value, and the overall performance of the crab walking mechanism is improved effectively. The type and size are assembled with the crab walking mechanism, and the pass performance test is carried out in two media of dry sand and wet sand. The performance of the crab walking mechanism is measured by three dimensional motion observation and analysis system. The results show that the maximum traction of the prototype B of the bionic foot and the prototype of the prototype C is compared with the original A. With the higher traction load and better traction performance, the average motion speed of the walking mechanism decreases linearly with the increase of the traction load, and the vertical load has little effect on the average motion speed. Combining with the traction performance, the motion picture analysis of the crab walking mechanism, when the traction load is certain, 3 kinds of prototype walking feet under the same vertical load. The size of the subsidence is as follows: the prototype A prototype B prototype C, the bionic walking foot like walking crab walking mechanism has a strong bearing capacity, which can reduce the energy consumption of the earth and unearthed, improve the movement efficiency, and have better performance of the soft ground than the original machine. The installation angle of walking foot has an influence on the performance of the crab walking mechanism, bionic walking. When the foot and leg bar is installed at 15 degrees, the traction performance, carrying capacity and passing performance of the crab like walking mechanism are better than that of walking mechanism with 0 degrees walking foot.
【学位授予单位】：吉林大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：Q811

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