Bionic Quadruped Robot Dynamic Gait Control Strategy Based on Twenty Degrees of Freedom

Quadruped robot dynamic gaits have much more advantages than static gaits on speed and efficiency, however high speed and efficiency calls for more complex mechanical structure and complicated control algorithm. It becomes even more challenging when the robot has more degrees of freedom.As a result, most of the present researches focused on simple robot, while the researches on dynamic gaits for complex robot with more degrees of freedom are relatively limited. The paper is focusing on the dynamic gaits control for complex robot with twenty degrees of freedom for the first time. Firstly, we build a relatively complete 3 D model for quadruped robot based on spring loaded inverted pendulum(SLIP) model, analyze the inverse kinematics of the model, plan the trajectory of the swing foot and analyze the hydraulic drive. Secondly, we promote the control algorithm of one-legged to the quadruped robot based on the virtual leg and plan the state variables of pace gait and bound gait. Lastly, we realize the above two kinds of dynamic gaits in ADAMS-MATLAB joint simulation platform which testify the validity of above method.

Design and Analysis of a Magnetic Bearings with Three Degrees of Freedom

The current research of supporting and transmission system in flywheel energy storage system(FESS) focuses on the low consumption design. However, friction loss is a non-negligible factor in the high-speed but lightweight FESS energy and momentum storage with mechanical-type supporting system. In order to realize the support system without mechanical loss and to maximize the e ciency of the flywheel battery, a permanent magnet biased magnetic bearings(PMBMB) is applied to the FESS with the advantages of low loss, high critical speed, flexible controllability and compact structure. In this frame, the relevant research of three degrees of freedom(3-DOF) PMBMB for a new type FESS is carried out around the working principle, structural composition, coupling characteristics analysis, mathematical model, and structural design. In order to verify the performance of the 3-DOF PMBMB, the radial force mathematical model and the coupling determination equations of radial two DOF are calculated according to an equivalent magnetic circuit, and radial–axial coupling is analyzed through finite element analysis. Moreover, a control system is presented to solve the control problems in practical applications. The rotor returns to the balanced position in 0.05 s and maintains stable suspension. The displacement fluctuation is approximately 40 μm in the y direction and 30 μm in the x direction. Test results indicate that the dynamic rotor of the proposed flywheel energy storage system with PMBMB has excellent characteristics, such as good start-of-suspension performance and stable suspension characteristics. The proposed research provides the instruction to design and control a low loss support system for FESS.

Dynamic analysis of new type elastic screen surface with multi degree of freedom and experimental validation

A feasible method was proposed to improve the vibration intensity of screen surface via application of a new type elastic screen surface with multi degree of freedom(NTESSMDF). In the NTESSMDF, the primary robs were coupled to the main screen structure with ends embedded into the elastomers, and the secondary robs were attached to adjacent two primary robs with elastic bands. The dynamic model of vibrating screen with NTESSMDF was established based on Lagrange's equation and the equivalent stiffnesses of the elastomer and elastic band were calculated. According to numerical simulation using the 4th order Runge-Kutta method, the vibration intensity of screen surface can be enhanced substantially with an averaged acceleration amplitude increasing ratio of 72.36%. The primary robs and secondary robs vibrate inversely in steady state, which would result in the friability of materials and avoid stoppage. The experimental results validate the dynamic characteristics with acceleration amplitude rising by62.93% on average, which demonstrates the feasibility of NTESSMDF.

Primary resonance of multiple degree-of-freedom dynamic systems with strong non-linearity using the homotopy analysis method

A homotopy analysis method（HAM）is presented for the primary resonance of multiple degree-of-freedom systems with strong non-linearity excited by harmonic forces.The validity of the HAM is independent of the existence of small parameters in the considered equation.The HAM provides a simple way to adjust and control the convergence region of the series solution by means of an auxiliary parameter.Two examples are presented to show that the HAM solutions agree well with the results of the modified Linstedt-Poincar＇e method and the incremental harmonic balance method.

新型3-DOF 1T2R并联机构的运动学分析与尺度优化

移动和转动混合运动的并联机构具有很高的研究和应用价值。基于转移混合输出运动的机构适用范围广,但该类机构的设计比较困难。为了研发和推广转移混合运动的1T2R并联机构,基于平面五杆机构和一条无约束支链,设计了一种一平移两转动(1T2R)的并联机构。首先,根据方位特征(POC)方程对机构进行了拓扑结构分析,并计算了该机构的自由度;然后,对该并联机构进行了运动学建模,推导了其位置正反解的解析表达式,并基于雅可比矩阵分析了机构的奇异性,利用三维离散搜索法计算了机构的工作空间,给出了机构在工作空间中的灵巧度分布情况;最后,利用粒子群算法(PSO)对机构的工作空间和灵巧度进行了双重优化,同时探讨了无约束支链的布置角φ对机构工作空间和灵巧度的影响。研究结果表明:所设计的1T2R并联机构结构简单,具有位置解析解;优化后的机构的工作空间和灵巧度分别提升了93.47%,203.42%;当无约束支链的驱动方向与平面(2P-3R)机构垂直布置时,能够获得更好的运动性能。该结果为3-DOF 1T2R机构的实际应用奠定了理论基础。

5-DOF混联机器人设计与运动学分析

针对现有2R1T并联机构并不能很好地满足航空航天工业制孔稳定性的问题,设计了一种全新的两转一移并联机构3SPU-PU,并基于此并联机构设计了2-DOF转头,构造了5-DOF混联机器人,可用于某型飞机座舱盖制孔。首先,利用修正的G-K公式计算了3SPU-PU并联机构的自由度;其次,利用子结构综合的方法对所设计的五自由度混联机器人进行了逆运动学分析;运用ADAMS仿真分析与MATLAB理论计算对运动学分析理论模型进行了验证;最后,利用有限元分析方法对混联机器人进行了静力学分析。结果表明,所设计的混联机器人刚度大、质量轻,能更好地满足制孔稳定性的需求,研究结果也为混联机器人的样机研制、动力学分析及实时控制打下了理论基础。

Separation of Comprehensive Geometrical Errors of a 3-DOF Parallel Manipulator Based on Jacobian Matrix and Its Sensitivity Analysis with Monte-Carlo Method

Parallel kinematic machines （PKMs） have the advantages of a compact structure,high stiffness,a low moving inertia,and a high load/weight ratio.PKMs have been intensively studied since the 1980s,and are still attracting much attention.Compared with extensive researches focus on their type/dimensional synthesis,kinematic/dynamic analyses,the error modeling and separation issues in PKMs are not studied adequately,which is one of the most important obstacles in its commercial applications widely.Taking a 3-PRS parallel manipulator as an example,this paper presents a separation method of source errors for 3-DOF parallel manipulator into the compensable and non-compensable errors effectively.The kinematic analysis of 3-PRS parallel manipulator leads to its six-dimension Jacobian matrix,which can be mapped into the Jacobian matrix of actuations and constraints,and then the compensable and non-compensable errors can be separated accordingly.The compensable errors can be compensated by the kinematic calibration,while the non-compensable errors may be adjusted by the manufacturing and assembling process.Followed by the influence of the latter,i.e.,the non-compensable errors,on the pose error of the moving platform through the sensitivity analysis with the aid of the Monte-Carlo method,meanwhile,the configurations of the manipulator are sought as the pose errors of the moving platform approaching their maximum.The compensable and non-compensable errors in limited-DOF parallel manipulators can be separated effectively by means of the Jacobian matrix of actuations and constraints,providing designers with an informative guideline to taking proper measures for enhancing the pose accuracy via component tolerancing and/or kinematic calibration,which can lay the foundation for the error distinguishment and compensation.

Singularity analysis of a two-dimensional elastic cable with 1:1 internal resonance

A two-degree-of-freedom bifurcation system for an elastic cable with 1：1 internal resonance is investigated in this paper. The transition set of the system is obtained with the singularity theory for three cases. The whole parametric plane is divided into several different persistent regions by the transition set. The bifurcation diagrams in different persistent regions are obtained.

Analysis of State Homicide Rates Using Statistical Ranking and Selection Procedures

Nonparametric and parametric subset selection procedures are used in the analysis of state homicide rates (SHRs), for the year 2005 and years 2014-2020, to identify subsets of states that contain the “best” (lowest SHR) and “worst” (highest SHR) rates with a prescribed probability. A new Bayesian model is developed and applied to the SHR data and the results are contrasted with those obtained with the subset selection procedures. All analyses are applied within the context of a two-way block design.

针对半月板损伤患者的运动学步态分析

目的:探讨应用Codamotion 2CX1三维动态关节运动捕捉系统分析不同程度半月板损伤患者运动学特征。方法:2020年12月至2022年6月收治的半月板损伤患者及招募的正常人共135例,男82例,女53例;年龄14~29岁;病程1~3个月。结合临床症状及MRI检查明确半月板损伤诊断,根据Stoller分级标准将半月板损伤分为4级:0级(正常)37例,Ⅰ级30例,Ⅱ级33例,Ⅲ级35例。采用Codamotion 2CX1三维动态关节运动捕捉系统对各组受试者进行行走测试,采集步行及运动学定量化指标,包括膝关节屈伸、内外旋、内外翻,并对其进行运动学进行分析。结果:在膝关节屈曲/伸直的分布中,4组患者膝关节最大屈曲、最小伸直及膝关节屈伸范围比较,差异有统计学意义(P<0.05);在膝关节内旋/外旋的分布中,4组患者膝关节内旋及膝关节旋转范围比较,差异有统计学意义(P<0.05);在膝关节内翻/外翻的分布中,4组患者膝关节外翻及膝关节翻转范围比较,差异有统计学意义(P<0.05);临床分期进展与膝关节伸直、外旋、内外翻及翻转活动范围呈正相关(P<0.05);与膝关节屈曲、内旋及屈伸、旋转活动范围呈现负相关(P<0.05);膝关节内旋、外旋角度可以作为半月板损伤临床分期的独立影响因素(P=0.006,0.019<0.05)。结论:半月板损伤患者膝关节运动发生了明显变化,且不同临床分期下,变化有一定差异,步态分析为半月板损伤的运动学分析提供了一个可靠的依据,有助于更好了解关节的运动学指标,同时提供了一个较为可靠的辅助诊疗方案,为后续医学研究提供了新方向。

人工肾脏泵用磁悬浮轴承设计与磁力特性分析

代替透析膜的持续离心分离新方法提高了依赖血液透析治疗的肾脏病患者生活质量,随之,人工肾脏泵的研究被很多学者关注.但传统人工肾脏泵采用滚动轴承进行支撑,存在溶血高、血栓率高等问题,为此,本文利用磁悬浮轴承的非接触、无润滑、高转速等优点,研发了一种应用于人工肾脏泵的结构紧凑且节能的单自由度控制型磁悬浮轴承.利用有限元分析软件进行仿真,探索径向被动控制部分和轴向主动控制部分的设计参数,并对总体进行仿真验证,进而对磁悬浮轴承进行结构性能评估.结果表明:仿真与实验的径向位移刚度系数分别为47.432 N/mm和49.531 N/mm,轴向电流刚度系数分别为0.144 N/AT和0.135 N/AT,轴向位移刚度系数为223.071 N/mm,满足该磁悬浮轴承的五自由度稳定悬浮要求;所设计的磁悬浮轴承简化了系统结构,减小了控制难度以及降低了系统功耗.

结构动力学应用中若干基本概念的研究

结构动力特性被广泛应用于结构振动控制、结构可靠性设计和健康监测,由此涉及到一些动力学基本概念的理解问题尚待深入探讨。采用一简支梁横向振动算例以及分别通过模态位移法和模态加速度法对多自由度系统的响应振幅进行分析计算,探讨结构位移响应与第一阶固有频率的关系、结构各阶位移模态的贡献与模态应变能的关系。基于模态正交性,通过分析多自由度振动系统的位移响应,论述了系统共振的必要条件,即在保证系统振动频率(某阶固有频率)等于激励频率的同时,其位移响应还应呈现出相应模态的形态;实现多自由度系统纯模态共振,可用于精确识别结构的模态参数。

基于ANSYS的工业机械臂结构分析与拓扑优化设计

机械臂的刚度和固有频率对其可靠性有重要影响,需对其进行深入研究。文章对某型六自由度工业机械臂进行建模设计,在ANSYS软件采用有限元分析方法对机械臂在力矩最大的工况下进行静态结构分析和模态分析,验证其刚度和固有频率是否符合要求。进一步采用拓扑优化方法对大臂进行优化,然后对大臂进行模型重构,导入到整个机械臂中进行结构分析与模态分析,比较优化前后机械臂的性能差异,验证了改良后机械臂的可靠性,实现轻量化目标,为后续生产提供参考依据。

多自由度四臂动物离心机设计与研究

针对当前动物离心机的局限性,设计了一种多自由度四臂动物离心机,用于航空航天医学实验。利用运动学对动物离心机进行运动分析;采用SolidWorks软件对动物离心机进行了建模;为提高动物离心机的结构稳定性,建立了有限元模型,对静止支撑结构进行了模态分析;利用动力学分析确定了动物离心机的驱动功率,并通过运行调试,验证了动物离心机工作稳定性。研究结果表明,多自由度四臂动物离心机确保了可靠性和安全性,满足实验要求,验证了设计方案的可行性。

社区尺度斜入射波场下场地-建筑群耦合作用模拟方法

场地-城市相互作用(site-city interaction,SCI)效应会显著改变场地地震波场分布及建筑反应,基于SCI效应理论计算研究方法的发展现状,发挥谱元(spectral element,SE)法可快速高效求解三维地震波场传播和多自由度(multi-degree of freedom,MDOF)模型计算量小且可同时模拟大量建筑的优势,同时,结合频率波数域(frequency wave number analysis,FK)方法,以等效地震荷载的方式施加地震波场,建立了FK-SE-MDOF耦合方法,实现了SE-MDOF耦合模型中多种波型(P波、SV波和SH波)的斜入射输入,解决了当前三维SCI效应研究方法中未能同时考虑建筑非线性、频谱特性、地震波波型及入射角度影响的问题。首先对方法原理进行了介绍;然后,通过与振动台试验的对比,验证了方法的正确性;进而,采用该方法建立理想场地-城市建筑群相互作用耦合模型,主要探讨了入射角度和地震波波型对SCI效应的影响,得到了一些有益结论。该方法较为真实地反映SCI效应影响的同时,可反映建筑基础轮廓对地震波场的影响,适用于需考虑建筑轮廓信息的社区尺度SCI效应研究,可为城市规划、抗震设计、风险评估以及震后救援等工作提供定量指导。

水泥混凝土凹坑路面破损对大客车乘员平顺性影响分析

不平整水泥混凝土路面严重影响了行车的平顺性,为揭示大客车与不平整路面相互作用关系,本文以重型大客车为研究对象,基于拉格朗日方程和达朗贝尔原理建立7自由度整车平顺性模型。通过滤波白噪声法建立4轮路面激励模型,借助ADAMS仿真软件建立整车动力学模型以及路面和凹坑模型,并结合大客车与不平整路面平顺性评价标准,以Z轴最大加速度绝对值进行对比分析。研究表明:凹坑路面对车辆平顺性影响显著。后排座椅位置受到的振动要远高于其他座椅位置处受到的振动。在同一位置的不同两侧,左侧的Z轴最大加速度绝对值明显高于右侧,特别在后排位置其Z轴最大加速度绝对值大约是右侧的1.5倍。当凹坑深度较小时,并不随着车速的增加与位置的不同而对乘坐的舒适性有较大影响;而当凹坑深度较大时,随着车速的增加,虽然4个位置的Z轴最大加速度绝对值变化较大,但均小于31.44 m/s^(2),不会对大客车上的乘员造成影响,平顺性良好。

4自由度番茄采摘机软体机械臂运动学分析

综合考虑番茄采摘机软体机械臂在复杂环境中的使用需求,以此来确定番茄采摘机械的4自由度模型。对番茄采摘软体机械臂进行正运动和逆运动分析,同时确定机械臂结构、关节长度、自由度选择等参数,并绘制出三维模型,从而为下一步选择控制系统硬件及软件编程奠定基础。

一种变自由度单回路机构的变拓扑结构设计及拓扑分析

特殊单回路机构通过一些特殊位置后会发生自由度变化,从而使其拓扑学、运动学/动力学性能发生变化,并适用于不同的应用背景。研究设计了一种由8个转动副(R)组成的单回路并联机构,它有3种运动模式,分别为2自由度、4自由度以及3自由度驱动,对应3个机构;然后,分析计算了3种运动模式下机构的方位特征集、自由度、耦合度3个主要拓扑特性,并分析了3种机构变拓扑结构的稳定性及可转变性;同时,对运动模式1、模式3下机构的位置正反解进行了分析。为基于这种变自由度单回路机构单元的可重构并联机构的研究提供了基础。

平粮机械臂设计及运动学分析

针对传统人工平粮作业方式费时费力、存在安全隐患等问题,面向现有履带式、桁架式平粮装备及方法作业空间大、效率低、能耗高等缺点,设计一款七自由度的机械臂以实现高大平房仓内粮面的自动平整。机械臂各个关节主要由数字液压缸驱动,选择MCU对各个关节数字液压缸进行控制,同时建立该机械臂的标准D-H参数表,通过MATLAB Robotics Toolbox建立机械臂三维仿真模型,采用几何法和基于物体雅可比的Newton-Raphson算法对其机械臂进行逆运动学求解,并通过蒙特卡洛法对工作空间进行仿真分析,利用五次多项式插值和T型插值对其运动轨迹进行仿真,利用RRT*算法进行避障路径规划。结果表明:该机械臂工作空间可覆盖平房仓内待平粮位置,运动轨迹平稳可靠,满足所需工作要求,T型插值法可以使机械臂运动轨迹在4~6 s之间,关节加速度降低至0 rad/s,RRT*算法可使机械臂精确避开高度在4~8 m范围内无需作业的粮堆。可为高大平房仓伸入式平粮装备研制和智能控制平台搭建提供基础支撑。

基于弹性网络回归的地震动参数排序与比选

为合理选取地震动参数以有效减小结构损伤预测的不确定性,基于弹性网络回归技术对多个地震动参数进行了比选。基于多种地震动参数以及大量单自由度(SDOF)模型的增量动力分析结果建立弹性网络回归模型,定义回归模型中回归系数值以及回归系数值为非零值的个数分别为地震动参数的敏感性系数和频数。基于地震动参数敏感性和频数分析结果对多种地震动参数进行排序,研究结构恢复力模型、地震动集和结构极限状态对地震动参数排序结果的影响。基于一座8层钢框架结构分析结果验证了基于弹性网络回归的地震动参数比选方法的有效性。结果表明:选取代表性的地震动参数加入最小二乘回归模型时,不同结构极限状态下回归分析中残差标准差显著减小。基于大量SDOF体系的地震动参数排序结果比选出了受地震动集、结构恢复力模型和结构极限状态影响较小的地震动参数。结果可为结构抗震能力预测用地震动参数的比选提供理论基础。