Development of a Leg Mechanism for Soft Landing Based on Biological Motion

With jumping mechanisms,soft landing motion is important to protect loads and the mechanisms.This study proposes a leg mechanism for soft landing based on biological motion.Human jumping motion with a load suggests a unique motion for soft landing.The landing model consists of two periods.Jerk is minimized in the first period and force is minimized in the second period.In comparison with other landing models,this model is specialized for soft landing motion protecting an objective part.Given all mechanisms have mass,such model is useful in practical application.For the purpose of realizing soft landing motion,this study proposes a new leg mechanism.The mechanism achieves quick variable transmission with cam and wire.Design process of the cam is explained with dynamics and computation.With the calculated cam shape,the leg mechanism can be driven by constant input voltage for simple control.Robustness against height change is also verified with landing simulation.With 50mm falling experiment,prototype leg mechanism performed soft landing without bounce motion and large sound.The acceleration profile of the body also agrees with the proposed soft landing model.

Expecting a Soft Landing

Amid the uncertainties of the global economy,China’s economic slowdown this year has triggered worries that the country’s growth engine is losing steam. Some even anticipate a hard landing. Lu Zhongyuan,Vice President of the Development Research Center of the State Council,dismissed the worries at a recent briefing in Beijing.Edited excerpts of his views follow:

Research on Bionic Jumping and Soft Landing of Single Leg System in Quadruped Robot

This paper proposed a novel multi-motion wheel-leg-separated quadruped robot that can adapt to both the structured and unstructured grounds.The models of the positive/inverse position,velocity,acceleration,and workspace of the single leg mechanism in the quadruped robot were established.A single leg complex dynamic model of the quadruped robot is derived,considering the mass and inertial force of all the components in the mechanical leg.Combined with the human jumping law in situ,the jumping trajectory of the single leg was planned.To reduce landing impact,a soft landing strategy based on motion planning was proposed by simulating human knee bending and buffering action.The change law of the kinetic energy and momentum of all the links in the single leg mechanism during the jump process was studied,and the influencing factors of jump height were analyzed to realize the height control of the jump.Single leg jumping dynamics model was established,and a dynamic control strategy for trajectory tracking with foot force compensation was proposed.In Adams and MATLAB/Simulink software,the jump simulation of single leg mechanism was carried out.The prototype of quadruped robot was developed,and the jumping experiment of the single leg mechanism was tested.The robot's single leg bionic jumping and soft landing control are realized.

Orbital maneuver strategy design based on piecewise linear optimization for spacecraft soft landing on irregular asteroids

Recently,asteroid exploration becomes an important branch of human’s deep space activities.In this paper,a piecewise linear optimal orbital maneuver strategy is designed for a spacecraft soft landing on irregular-shaped asteroids.First,the space around an irregular asteroid is converted into several grid units,and the gravitational field of the asteroid is linearly fitted in each unit.Then,the soft-landing orbital maneuver strategy design problem is formulated as a piecewise linear optimal problem,and further transferred into a family of two-point boundary value problems,which can be solved using collocation method.Finally,a corresponding algorithm is developed to obtain the piecewise linear optimal maneuver strategy,which is proved to be able to achieve the soft-landing mission well.Simulation results show that the error of the model linearization is small enough,while the calculation efficiency is remarkably improved,and the robustness of maneuver strategy is also improved.

Expecting a Soft Landing

Amid the uncertainties of the global economy, China’s e conomic slowdown this year has triggered worries that the country’s growth engine is losing steam. Some even anticipate a hard landing. Lu Zhongyuan, Vice President of the Development Research Center of the State Council, dismissed the worries at a recent briefing in Beijing,saying the slowdown is the result of the government’s macro-control and is still within the normal fluctuation range. Edited excerpts of his views follow:

地外天体软着陆自主导航与控制技术研究进展

软着陆探测是重要的地外天体探测方式,制导、导航与控制(Guidance,Navigation and Control,GNC)是地外天体软着陆成功的关键。首先梳理了国内外月球、火星和小天体等地外天体软着陆任务发展现状;在此基础上,总结了地外天体软着陆任务典型GNC方案及自主导航与控制技术主要进展;最后,针对未来的地外天体精确定点软着陆任务,提出了需要重点关注和发展的自主导航与控制关键技术,为未来技术发展提供借鉴和参考。

软土地区多井降水与回灌条件下的土层沉降特征研究

为研究软土地区车站基坑降水与回灌引起的土体沉降及土层变形特征,结合上海市域铁路示范区线水乡客厅站抽水试验工程实例,通过分析土体在抽水及回灌作用下的水位变化与土层沉降特征,研究表明,(1)抽水过程中,含水层中上部和上部弱透水层中产生的沉降明显大于抽水含水层下部土层产生的沉降;停止抽水和回灌过程中,抽水含水层中上部和上部弱透水层中产生的回弹明显大于抽水含水层下部土层。(2)抽水期间,地面沉降距离抽水中心愈近,沉降值愈大,远离抽水中心,地面沉降有逐渐减小的趋势;回灌引起的地面回弹与抽水沉降的影响规律并不相同;(3)土层间变形量和含水体层厚和层间岩土体性质密切相关,回弹模量大且层厚大的土层较回弹模量小,且层厚小的土层回弹性效率高,各含水体均存在非线性回弹。

水泥土帷幕桩联合堆载预压对路基沉降的影响

针对市政道路工程中遇到的深厚软土状态地基,通常需要借助水泥土帷幕桩联合堆载预压技术做有效加固,并针对不同工况展开了模型试验。研讨了水泥土帷幕桩在桩长不同、布置形式不同,布设位置也不同的情况下,路堤加固后在全服役周期内体现出的沉降特性。结果显示,坡脚位置上帷幕桩的增设确实让路堤沉降的可控性出现了明显的提升;设置桩长的时候需要参照软土地基含水率在竖直方向的分布规律加以确定;在坡脚位置上布置的帷幕桩并没有对路基沉降产生明显影响,另外在具体工程中,确定坡脚处帷幕桩具体布置位置的时候,还应该考虑到坡脚部位的反挖工作量,其是否邻近灌溉水。这些结论可为日后类似工程的施工提供参考。

ARCGIS软件在第三次国土调查中应用研究

ARCGIS软件是测绘地理信息项目中常用软件。第三次国土调查是作为一项在国情国力方面的调查,其目的是调查清楚全国土地资源利用情况和国土地类现状,为以后诸如国土空间规划、基本农田划定、生态文明建设等方面提供基础数据和政策导向。在第三次国土调查中,ARCGIS为内业数据处理提供了强大的技术支撑。ARCGIS软件可对线状地物图斑化和野外举证数据提前批处理进行详细的研究,在水利、农业、生态、交通、林业、住建等方面都有非常广泛的应用。

泉州海湾大道软土地基处治方案研究

通过泉州海湾大道工程案例,分析项目地质情况、软基路段分布情况、土体参数,从常用的浅层、中层、深层软基处理方法中初选软基处理方案。通过地基处理计算、软基段边坡稳定分析及沉降分析等方法充分比选各方案的技术可行性。在技术可行的基础上,通过施工可行性及工程投资等方面对各方案进行综合比选,选出适应本项目不同深度的最优方案。同时,对存在软基的特殊断面位置进行特殊处理。在控制总沉降的同时,过渡特殊位置的差异沉降,使设计方案能够达到良好的处治效果,满足设计使用要求。

Hierarchical Optimization of Landing Performance for Lander with Adaptive Landing Gear

A parameterized dynamics analysis model of legged lander with adaptive landing gear was established. Based on the analysis model, the landing performances under various landing conditions were analyzed by the optimized Latin hypercube experimental design method. In order to improve the landing performances, a hierarchical optimization method was proposed considering the uncertainty of landing conditions. The optimization problem was divided into a higher level(hereafter the "leader") and several lower levels(hereafter the "follower"). The followers took condition?ing factors as design variables to find out the worst landing conditions, while the leader took bu er parameters as design variables to better the landing performance under worst conditions. First of all, sensitivity analysis of landing conditioning factors was carried out according to the results of experimental design. After the sensitive factors were screened out, the response surface models were established to reflect the complicated relationships between sensi?tive conditioning factors, bu er parameters and landing performance indexes. Finally, the response surface model was used for hierarchical optimization iteration to improve the computational e ciency. After selecting the optimum bu er parameters from the solution set, the dynamic model with the optimum parameters was simulated again under the same landing conditions as the simulation before. After optimization, nozzle performance against damage is improved by 5.24%, the acceleration overload is reduced by 5.74%, and the primary strut improves its performance by 21.10%.

软土地区深基坑变形原因及控制措施分析

深基坑变形受地下水位、土壤的力学特性及周围建筑物等多种因素的影响,在研究深基坑变形时,需要考虑软土地区的特殊性。软土地区的土壤具有较高的含水量和较低的强度,易发生沉降和变形。因此,软土地区深基坑的设计和施工要采取相应的措施控制变形,并保证结构的安全性。文章先阐述了软土地区深基坑变形控制的必要性,然后分析软土地区深基坑变形的原因,最后研究了软土地区深基坑变形控制措施。通过采取有效的控制措施,有利于改善土体的物理力学性能,提高被动区土体抗力,减小基坑的变形,增强基坑的稳定性。

考虑局部自相似性的土地复垦规划空间预测算法

土地复垦规划时土地图像存在较大噪声,且不同地区的土地复垦情况可能存在空间异质性,无法达到理想空间预测效果。为此,提出一种考虑局部自相似性的土地复垦规划空间预测算法。利用低秩逼近处理方法对噪声污染的观测矩阵的核范数低秩逼近,得到矩阵的最小核范数,实现土地空间图像去噪;利用局部自相似性计算土地再利用贡献值,以此建立空间预测模型,计算子区域内栅格与所选区域栅格差异程度;利用ArcGIS软件计算评价因子,以此划分等级,预测土地复垦规划空间。由实验结果可知,该算法预测的空间规划基本适宜度比例最大,其次是不适宜度、中度适宜度、临界适宜度,与理想规划结果一致。

基于信息融合的小天体软着陆组合导航算法

小天体距地球较远,观测信息不足,引力场弱且分布不规则,对自主导航算法的精度和实时性提出了更高的要求。本工作以小天体软着陆自主导航为应用背景,针对惯性导航误差累积和光学导航观测周期长等问题,提出了一种基于信息融合的组合导航算法。以软着陆探测器的位置和速度为状态向量,通过引入了一种信息融合算法,将光学导航信息与惯性导航信息进行信息融合,生成对软着陆探测器状态的估计。实验结果表明:该算法能有效地提高导航定位精度,并对速度误差有一定的抑制作用,为探测器在小天体表面软着陆提供了一种行之有效的方法。

大尺寸自由活塞激波风洞重活塞软着陆关键技术

高焓激波风洞的驱动技术决定了风洞总焓和总压试验能力。重活塞压缩加热技术具有驱动性能强和运行灵活性高等特点,是高焓激波风洞关键驱动技术。针对重活塞发射效能、重活塞与壁面摩擦、膜片破膜等情况带来的大尺寸重活塞难以安全软着陆问题,通过理论分析、动网格数值模拟和试验验证相互结合的手段,分析了重活塞实际运动过程的影响因素,建立了重活塞调谐运行方法,获得了稳定的驱动压力,可为不同的模拟需求提供对应的试验状态。研究了质量为205 kg、275 kg的重活塞在压缩管中运行最高速度分别超过350 m/s、450 m/s的软着陆过程,获得了压缩管末端总压15 MPa、总温3450 K和总压45 MPa、总温4845 K的定压试验状态。本研究解决了大尺寸自由活塞激波风洞重活塞软着陆难题,保障了世界最大尺寸自由活塞驱动的FD-21高焓激波风洞中、质量为数百千克的重活塞、在长度为75 m的压缩管中的运行安全。

基于Unity3D的月面复杂地形场景构建及模拟驾驶系统

为了验证未来月面复杂地形操控技术方案,基于Unity3D物理引擎对月表模型、月球物理环境以及月面光照环境进行了模拟,设计并开发了一套用于模拟月球自主进行着陆点选址以及在线航天器着陆轨迹规划的系统。该模拟系统的工作过程包含了:基于面阵雷达与立体相机信息融合的局部月表重建、基于3D重建结果的月表地形着陆代价的快速评估与自动着陆选址,以及使登陆器能够到达选址目标的最优燃料消耗着陆运动规划,实现了月球着陆器短距离自主选址着陆的模拟系统构建,同时也从仿真的角度初步验证了“地形重建-地形评估-自主选址-软着陆”这一自主着陆过程的可行性。

压扭超材料填充柱壳撞击固壁的动态力学行为研究

航天器着陆时的冲击防护是保证航天器安全着陆的关键技术,针对航天器腿式着陆器对缓冲装置的需求,文章提出了一种新型能量吸收结构——将压扭双螺旋超材料填充于圆柱壳内部,并基于ABAQUS软件建立了该吸能结构的有限元计算模型,模拟了其撞击固壁时的动态力学行为,开展了系统的参数化研究分析。模拟和分析结果表明:1)由于耦合作用,填充了压扭双螺旋超材料的圆柱壳吸能盒的能量吸收能力逐渐会大于压扭双螺旋超材料和圆柱壳能量吸收的线性叠加;2)圆柱壳吸能盒壁厚和压扭双螺旋超材料连杆个数是影响其动态力学特性和能量吸收的关键参数。上述结论可为内充压扭超材料圆柱壳式吸能盒在航天器着陆器中的应用提供一定技术参考。

软土地基公路工程沥青混凝土路面施工技术研究

软土地基公路工程对沥青混凝土路面施工质量要求较高,施工难度较大,施工质量直接关系到公路行车感受。文中以某软土地基公路工程为工程背景,通过软土地基加固、沥青混凝土混合料配制、路面沥青混凝土摊铺及碾压,以此完成沥青混凝土路面施工。通过对施工道路平整度测试,路面国际平整度指数较高,路面平整性良好,采取的施工技术能够有效保证施工质量。

房屋建筑施工中深厚软土地基处理技术分析

为了提升建筑结构的安全性与稳定性,研究房屋建筑施工中深厚软土地基处理技术。文中采用静力观测法评价软土地基的力学特性,判断土壤性质,通过板框桩加固和地下泵送混凝土方案进行深厚软土地基处理,并运用振动传感器技术对深厚软土地基处理进行后续监测。测试结果表明,应用文中技术后,土压力明显降低,地基沉降量得到了明显改善,说明其能提高土体的承载能力和稳定性,提升建筑施工工程质量和安全性。