Joint space compliance control for a hydraulic quadruped robot based on force feedback

In the realm of quadruped robot locomotion,compliance control is imperative to handle impacts when negotiating unstructured terrains.At the same time,kinematic tracking accuracy should be guaranteed during locomotion.To meet both demands,ajoint space compliance controller is designed,so that compliance can be achieved in stance phase while position tracking performance can be guaranteed in swing phase.Unlike operational space compliance control,the joint space compliance control method is easy to implement and does not depend on robot dynamics.As for each joint actuator,high performance force control is of great importance for compliance design.Therefore,a nonlinear PI controller based on feedback linearization is proposed for the hydraulic actuator force control.Besides,an outer position loop（compliance loop）is closed for each joint.Experiments are carried out to verify the force controller and compliance of the hydraulic actuator.The robot leg compliance is assessed by a virtual prototyping simulation.

New variables for measuring joint space width to evaluate knee osteoarthritis

Assessing the radiographic features of knee osteoarthritis （OA）, especially joint space narrowing, is important for evaluating disease progression. The purpose of this study was to quantitatively analyze joint space narrowing by measuring 2 new variables： the average joint space width （aJSW） and the articulate angle （AA） on X-ray films, and to evaluate the relationship between the 2 variables, knee function and OA symptoms. Methods Using the web-based radiology viewer （Cedara I-ReachTM 4.1.1）, we measured the 2 variables in 50 knees of 41 patients with knee OA participating in the Shanghai OA Study. We also evaluated the Kellgren-Lawrence （K-L） grade, the Western Ontario and McMaster Universities OA Index （WOMAC）, and additional questionnaire in OA knees. The study was approved by the ethics committee of Shanghai Ninth People＇s Hospital （No. 2009-28）. Results The aJSW correlated with the K-L grade （r=-0.57, P 〈0.001）, kneeling （r=-0.29, P=0.04）, sitting cross-legged on the floor （r=-0.31, P=0.03）, WOMAC pain （r=-0.31, P=0.03）, WOMAC disability （r=-0.35, P=0.01）, pain while squatting （r=-0.37, P=0.01）, and defecating in a squatting position （r=-0.39, P= 0.01）. The AA correlated with defecating in a squatting position （r=0.29, P=0.05）, WOMAC disability （r=0.30, P=0.04） and K-L grade （r=0.44, P=0.003）. The K-L grade also correlated with pain while squatting （r=-0.40, P=0.005） and defecating in a squatting position （r=-0.34, P=0.02）, WOMAC pain （r=0.30, P=0.04）, and WOMAC disability （r=0.30, P=0.04）. Conclusions The aJSW closely correlated with knee OA symptoms and function scores, and was more sensitive to knee OA related disabilities than K-L grade and the AA. The aJSW could be used as a new variable for knee OA evaluation.

Influence of void space on microscopic behavior of fluid flow in rock joints

Advanced microfluidic technology was used to examine the microscopic viscous and inertial effects evolution of water flow in rock joints. The influence of void space on fluid flow behaviour in rock joints under different flow velocities was experimentally investigated at the micro scale. Using advanced fabrication technology of microfluidic device, micro flow channels of semicircular, triangular, rectangular and pentagonal cavities were fabricated to simulate different void space of rock joints, respectively. Using the fluorescence labelling approach, the trajectory of water flow was captured by the microscope digital camera when it passed over the cavity under different flow velocities. The flow tests show that the flow trajectory deviated towards the inside of the cavity at low flow velocities. With the increase in flow velocity, this degree of flow trajectory deviation decreased until there was no trajectory deviation for flow in the straight parallel channel. The flow trajectory deviation initially reduced from the void corner near the entrance. At the same time, a small eddy appeared near the void corner of the entrance. The size and intensity of the eddy increased with the flow velocity until it occupied the whole cavity domain. The gradual reduction of flow trajectory near the straight parallel channel and the growth of eddy inside the cavity reflect the evolution of microscopic viscous and inertial forces under different flow velocities.The eddy formed inside the cavity does not contribute to the total flow flux, but the running of the eddy consumes flow energy. This amount of pressure loss due to voids could contribute to the nonlinear deviation of fracture fluid flow from Darcy's law. This study contributes to the fundamental understanding of non-Darcy's flow occurrence in rock joints at the micro scale.

磁共振3D space序列在膝关节半月板放射状撕裂中的诊断价值

目的 评价磁共振3D space序列在膝关节半月板放射状撕裂中的诊断价值,提高对此病的影像认识,为临床诊疗提供帮助。方法 回顾性分析29例经关节镜证实的膝关节半月板放射状撕裂患者的磁共振资料;对比常规磁共振2D序列与3D space序列在半月板放射状撕裂病变中的诊断效能,使用Fisher确切概率法对两种方法诊断半月板放射状撕裂的准确率进行比较。结果 3D space序列和常规2D序列诊断半月板放射状撕裂的准确率分别为96.7%(29/30)、80.0%(24/30),3D space序列诊断准确率高于常规2D序列,差异有统计学意义(P<0.05)。结论 3D space序列在半月板放射状撕裂的诊断中具有较高价值,其诊断效能优于2D序列。

Numerical evaluation of buckling behavior in space structure considering geometrical parameters with joint rigidity

The buckling behavior of single layer space structure is very sensitive. The joint rigidity, moreover, is one of the main factors of stability which may determine the entire failure behavior. Thus, the reasonable stiffness of joint system, which is neither total pin assumption nor perfect fix condition, is very important to apply to the real single layer space one. Therefore, the purpose of this work was to investigate the buckling behavior of single layer space structure, using the development of the upgraded stiffness matrix for the joint rigidity. To derive tangential stiffness matrix, a displacement function was assumed using translational and rotational displacement at the node. The geometrical nonlinear analysis was simulated not only with perfect model but also with imperfect one. As a result, the one and two free nodal numerical models were investigated using derived stiffness matrix. It was figured out that the buckling load increases in proportion to joint rigidity with rise-span ratio. The stability of numerical model is very sensitive with the initial imperfection, responding of bifurcation in the structure.

贯通型标准JRC双节理剪切力学及声发射特性研究

节理岩体的抗剪性能是影响工程岩体强度及稳定性的关键因素。基于3D打印技术制作标准JRC节理面模具和固定夹板,采取一体化浇筑方式制备不同节理面间距和不同粗糙度的双节理试样,结合声发射(acousticemission,AE)技术探究不同法向应力条件下粗糙双节理岩体剪切力学特性和破坏演化特征。结果表明:剪切应力-剪切位移曲线形态受节理粗糙度和法向应力共同影响。随JRC和法向应力的增加,剪切应力软化程度加重;法向应力较大时,峰后阶段剪切应力存在多次突降现象,突降值随法向应力的增加而增大。峰值剪切强度出现在双节理间岩石夹层断裂时刻,随JRC和法向应力的增加呈增大趋势,随节理面间距增加呈减小趋势。AE结果表明:岩石夹层断裂时刻AE能量大幅突增,AE能量峰值稍滞后于剪切应力峰值,随法向应力的增加,AE能量峰值和累积AE能量值增大;AE定位点空间上集中于岩石夹层部分,时间上频发于200~600 s内,随节理面间距的增加,AE定位点的集中范围扩大。

面向战区联合作战的空间需求响应任务规划

针对战区联合作战中的空间需求响应问题,描述了面向战区联合作战的空间需求响应任务规划的背景;从空间资源能力、空间需求响应机制、空间需求响应效益和代价等方面,分析了空间需求响应任务规划所需考虑的主要因素;定义并描述了任务规划模型,设计了任务规划计算方法,并结合战区联合作战实际进行了案例仿真与分析,验证了模型和方法的有效性,为战区联合作战中空间需求的有效响应提供了理论和方法支撑。

柔性关节空间机械臂传感容错无模型自适应控制

针对传感信号畸变、丢失等故障状态严重影响空间机械臂控制系统性能的问题,提出基于空间机械臂运动传感器故障观测的无模型自适应容错控制方法。采用动态线性化和递推参数估计思想设计传感故障监测器,实现对传感畸变及数据丢失等故障的判定,并进行运动状态预测估计;建立包含跟踪误差变化率项的无模型自适应控制准则函数,有效惩罚由传感故障引起的参数估计突变问题;设计面向柔性关节空间机械臂的新型传感容错无模型自适应控制(SFT-MFAC)算法。仿真结果表明,在不同传感故障情况下,所提控制策略均能快速准确识别传感故障信息,避免系统瞬时发散,有效延长系统响应时间,增加控制系统的鲁棒性。

全球空间安全治理视域下临近空间飞行监管研究

临近空间作为全球一体化的重要连接点,是实现长期驻空侦察、全球精准打击的军事战略高点。受空天划界论争的影响,临近空间飞行的监管规则仍依附于国内立法,在国际层面尚未实现有效规制和协调。在临近空间法律地位不清、监管主体不明、监管客体不定、监管内容复杂、飞行活动存有争议的情况下,现有国际航空航天法律制度已无法满足调整此类新型利益关系的实践需要。构建针对性的监管制度不仅是行业有序发展的基础,也是确保地面国国防安全和临近空间资源有序开发利用的重要保障。在国内立法层面,中国可参鉴《临近空间管制公约(草案)》的相关条款,积极推进临近空间融入航空法或航天法的制度设计,或制定单行的临近空间法,以国内立法引领国际立法;在国际立法层面,应以国际民用航空组织为主导,通过修订《国际民用航空公约》(又称《芝加哥公约》)相关附件或增设临近空间飞行的新附件标准,推进国际统一规则的构建。

四川大学博物馆结构设计重难点分析研究

四川大学博物馆采用钢框架结构体系,并设置屈曲约束支撑改善结构的抗震性能。介绍了四川大学博物馆的结构设计参数及抗震性能目标。针对结构设计中的重难点,开展了屈曲约束支撑的工作机理分析、框架柱计算长度与穿层柱分析、东侧大悬挑空间的相关分析。利用反应谱分析及时程分析探究了屈曲约束支撑工作机理,分析结果表明,屈曲约束支撑能够有效改善钢结构产生塑性铰的状况,起到保护主体钢框架的作用。针对东侧大悬挑空间的功能要求,设计采用了屋顶桁架结合钢拉杆吊挂东侧大楼梯的结构形式,通过结构防连续倒塌分析、楼板应力分析、楼盖舒适度分析、关键节点有限元分析等确保该部位结构设计安全合理。对整体结构受力机理和薄弱部位进行了研究,提出了重点部位的设计原则和加强措施。

汽车组合仪表有意电磁干扰空时域联合分离系统设计

有意电磁波与汽车仪器电磁传输波产生的混合干扰,降低了汽车组合仪表的稳定运行能力,造成仪表设备失灵;为避免上述情况的发生,设计汽车组合仪表有意电磁干扰空时域联合分离系统;在步进电机驱动电路中,设置汽车组合仪表控制器、分离电源与PCB电路板、有意电磁干扰数字传感器;分配有意电磁波空时域源地址,通过计算干扰信号平坦度的方式,确定脉冲参数的取值范围,实现汽车组合仪表有意电磁的空时域干扰效应分析;估算有意电磁波干扰信号的数目,按照信号分解的处理原则,求解联合分离修正函数,实现电磁干扰的联合分离;在设置频率范围在100 MHz~1 GHz之间、幅度范围为0.5~5 V、脉冲宽度范围为10~100 ns区间后,通过实验结果表明,设计系统应用后可以在混合信号中,按照空域、时域标准的不同分离有意电磁波,且分离后的信号波长、信号频率依然在1.0μm、300 Hz左右,不会因混合干扰降低汽车组合仪表的稳定运行能力。

Orthodontic retreatment of an adult woman with mandibular backward positioning and temporomandibular joint disorder:A case report

BACKGROUND The role of occlusal factors on the occurrence of temporomandibular joint disorders(TMDs)is still unclear and it is tricky for orthodontists to treat malocclusions in patients with TMDs.We report the case of the second orthodontic treatment of an adult female with Class II division 2 malocclusion associated with TMD.With the removal of anterior occlusal interference,TMD symptoms were alleviated and cone beam computed tomography(CBCT)images showed the bilateral condyles shifted forward.CASE SUMMARY This case report presented an orthodontic retreatment of an adult female with TMD and mandibular backward positioning based on CBCT examination and Joint Space Index(JSI)analysis.The left and right JSI values of-38.5 and-52.6 indicated that the position of bilateral condyles had posterior displacement.Ten years prior to this evaluation,she underwent orthodontic treatment resulting in the extraction of two upper premolars and one lower central incisor.The joint symptoms,including pain and sounds,were alleviated along with verified mandibular forward repositioning by extraction of another lower central incisor.CONCLUSION Mandibular backward positioning could be associated with TMD.JSI analysis based on CBCT is a convenient way to examine condylar positions quantitatively.

深部煤系储层缝间干扰多裂缝同步扩展规律试验研究

为研究深部煤系储层缝间干扰多裂缝同步扩展规律,采用自行研制的TCHFSM-I型大尺寸真三轴压裂渗流模拟装置,开展不同压裂孔间距、不同注液速率对多裂缝同步扩展规律的影响试验。通过观察和分析压裂过程中裂缝扩展形态、注液压力演化规律,以及声发射动态响应特征和注液流量演化特征,结果表明:压裂孔间距较小时,左右两侧裂缝扩展长度大于中部裂缝,随着压裂孔间距增大,左中右3条裂缝均衡扩展;增大注液速率可以使起裂压力增高,多裂缝长度增加,有效提高储层改造体积;增大压裂孔间距和注液速率,可以使左中右3个压裂孔的注液流量占比更均衡。

交替极化阵列对消盲区分析与验证

当干扰信号的空域和极化域特征与目标信号相似时,采用空极化域联合抗干扰技术在消除干扰的同时也会抑制目标信号,导致干扰对消后信干噪比(signal to interference plus noise ratio,SINR)低于雷达系统需求,从而形成干扰对消盲区。针对这一现象,通过在空域、极化域与空极化域分别建立交替极化阵列对消盲区模型,推导了对消盲区位置和大小的数学表达式,从而给出了交替极化阵列对消盲区的数学表征方法。进而分析了交替极化阵列对消盲区的分布规律与影响因素,研究发现阵元间距能够显著影响交替极化阵列对消盲区的分布,在相同条件下交替极化阵列对消盲区大于共点极化阵列对消盲区,结果表明交替极化阵列虽然通过减少天线数目降低了设备成本,但增大了阵列的对消盲区。然后,对消盲区模型进行了数值仿真,仿真结果验证了理论分析。最后,利用信道模拟器搭建了实验平台,信道模拟实验测得的对消盲区与理论值基本一致,再次证明了分析结论的有效性。

机器人学基础课程轨迹规划仿真教学研究

机器人轨迹规划技术是机器人学基础课程中的核心内容,是研究机器人、机械臂等系统的重要理论基础,课程体现了较强的实践性,理论知识涉及三维空间,公式推导过程较为复杂、抽象。应用MATLAB中强大的数值计算和可视化功能,结合轨迹规划中理论公式对机器人轨迹进行规划、分析。通过数值仿真对机器人笛卡尔空间、关节空间的轨迹进行规划,让学生直观地学到轨迹规划理论,掌握从公式推理到数值仿真的实践过程,增强学生对轨迹规划的理解,提高学生的专业知识能力,提升教学效果。

Is the Cape Stone Forest in Shantou City formed by wave erosion? A comparison of the pedestal rocks on the coasts and the mountains of Queshi in eastern Guangdong, China

Cape Stone Forest is a group of granite rock pillars(pedestal rocks) towering over Shilin Lake, on the southern shore of Shantou Bay in eastern Guangdong, China. The rock pillars were previously identified as sea stacks because they have marine notch-like concave sidewalls at their base, and more importantly, the lake is immediately adjacent to the bay, which is exposed to the open sea. However, rock pillars similar in shape and size can also be found at the top of Queshi Mountain, which is only about 300 meters northwest of the lake and about 85 meters above sea level. Therefore, the marine origin of Cape Stone Forest is seriously questioned. In this study, 3D imagery and drone technology were used to collect data in the investigations without direct manual measurements in the water or on the mountain. It shows that the concave sidewalls of the rock pillars in the lake and on the mountains occur at different heights and are exposed to different directions, while a natural sea stack on Mayu Island at the mouth of Shantou Bay has a horizontal notch parallel to the sea level, although the granite rock of the sea stack is the same as that of the lake and the mountains. The eastern side of the island, where the sea stack is located, is exposed to the open sea but blocks large waves for the rock pillars in the lake. Therefore, the origin of Cape Stone Forest cannot be explained by wave-based mechanisms. The only satisfactory explanation that takes into account all the field evidence is that the narrow rock pillars of the lake and mountain were formed by chemical weathering that penetrated closely the spaced joints of the granite rock, and the notch-like concave sidewalls were formed by more effective chemical weathering at the base of the pillars.

基于关节空间位形优选的稳定平台运动学标定

船舶姿态稳定平台装载作业时,其作业精度必须要满足工程实际的需要.传统的方法难以建立包含全部误差源的误差模型,因而针对3-UPS&S姿态稳定平台的运动学标定问题,从关节空间的角度切入,建立了基于驱动关节等效误差的模型,并开展了基于关节空间的位形优选工作.首先,使用伪误差理论建立了驱动关节等效误差模型,其将稳定平台工作空间各维度相互耦合的姿态误差解耦并转化为关节空间等效驱动关节误差,并借助4阶幂多项式将后者描述为随位形变化的函数,从而构建了稳定平台整机误差辨识模型.其次,采用三坐标测量臂制定姿态误差测量方案,建立可解耦至关节空间的参数辨识方法,并开展离线辨识和误差实时在线补偿.在解耦至关节空间参数辨识的基础上,着重研究如何在关节空间中开展测量位形优选工作,以提升平台的姿态补偿精度.通过对各驱动杆离散化处理获得稳定平台的可达工作范围,而后基于残差分析理论定义了位形优选指标,并采用Exchange-Add-Exchange算法对位形优选的约束问题进行优化分析,利用计算机开展仿真实验获取了最佳测量位形.最后,根据测量方案,采用三坐标测量臂获取样机姿态误差数据并开展误差补偿实验,验证所提方法的正确性和有效性.实验结果表明,稳定平台的姿态体积精度由标定前的0.487°降低为0.065°.

关节间隙宽度测量对内侧膝关节单髁置换效果及预后的影响

背景:与全膝关节置换相比,膝关节单髁置换具有康复快、成本低、本体感觉好等优点,但其术后高翻修率也是不容忽视的问题。目前对于导致膝关节单髁置换后高翻修率的原因尚不完全明确,因此术前严格把握手术指征对改善膝关节单髁置换后疗效和降低翻修率至关重要。作为常用的影像学测量手段,关节间隙宽度的评估可能对膝关节单髁置换手术指征的选择具有重要的临床参考价值。目的:综述关节间隙宽度的测量方法及对判定内侧膝关节单髁置换疗效和预后的影响。方法:通过万方和PubMed数据库检索1950-01-01/2023-06-01发表关于膝关节单髁置换疗效评价因素和关节间隙宽度对膝关节单髁置换疗效影响的相关文献,通过将文献汇总、分析,对关节间隙宽度的测量方法、术前内侧间室关节间隙宽度对内侧膝关节单髁置换疗效的影响、内侧膝关节单髁置换后外侧间室关节间隙宽度变化对预后的影响做以综述。结果与结论:①尽管目前用于研究和测量膝关节关节间隙宽度的方法很多,但负重位下X射线片测量关节间隙宽度仍是日常骨科实践中评估骨关节炎进展的常用方法,其可适度反映软骨厚度。②术前膝关节内侧间室关节间隙宽度会影响内侧活动平台膝关节单髁置换后的疗效,内侧关节间隙宽度/外侧关节间隙宽度<40%或内侧关节间隙宽度≤2mm的膝骨关节炎患者,可能更适合行内侧活动平台膝关节单髁置换。③内侧膝关节单髁置换后外侧间室关节间隙宽度变化对预后产生一定影响,术后通过改善外侧间室的关节匹配度,可延缓外侧间室关节退变的进展、降低假体翻修率,但尚欠缺相关的临床研究。总之,关节间隙宽度的影像学测量对判定内侧膝关节单髁置换的术后疗效和预后具有重要的临床参考价值。

腰椎黄韧带形态及其与周围结构的解剖学关系

目的开展腰椎黄韧带形态及其与周围结构的解剖学关系研究。方法观察1具层厚0.2 cm的连续腰椎横断层、3具层厚1.0 cm的腰椎横断层和1具层厚2.0 cm的腰椎矢状断层标本中的黄韧带。解剖10具人体标本(男性4具,女性6具)的腰椎椎管后壁,观察腰椎黄韧带形态及其与周围结构的关系。结果15具标本均表现为腰椎黄韧带外侧端覆盖椎间孔后壁的全部,其上缘前方与脊神经相毗邻;椎管后壁外侧半黄韧带覆盖关节突关节囊,内侧半黄韧带附着于相邻椎板,其上缘附着于上位椎弓板中部,下缘附着于下位椎弓板上缘;6具(40%)标本的腰椎黄韧带与关节突关节囊、上位椎弓板、棘间韧带之间见疏松结缔组织或间隙。结论黄韧带与椎间孔前后径关系密切,黄韧带后方的硬膜后间隙使两侧关节突关节腔存在潜在连通可能。

节理特征对截齿截割力影响的模拟研究

为探究节理参数对截齿截割力影响的变化规律,利用SolidWorks构建镐形截齿三维模型,运用有限元软件ABAQUS,建立截齿截割节理煤岩的有限元耦合模型,研究不同节理参数下截割力变化趋势。结果表明:随节理倾角增加,截割力均值、截割力峰值均值呈先增加后减小的趋势,其在节理倾角为30°时最小;随节理间距增加,截割力均值、截割力峰值均值呈增大的趋势。该研究可为复杂煤层工况下滚筒合理参数匹配奠定研究基础。