A generic PWM strategy for multi-leg VSI-fed machine drives

A generic pulse width modulation（PWM） strategy is proposed for the multi-leg voltage source inverter（VSI）.First, the multi-leg VSI is modeled, which is independent from the load structure. Secondly, the proposed PWM strategy is deduced by inverting the mathematical model of the multileg VSI. According to the relationship between the leg number of VSIs and the phase number of electrical machines, the multi-leg VSI-fed machine drives are classified into two types：matched and unmatched applications. The leg numbers of VSIs and the phase number of electrical machines are equal in matched applications while they are different in unmatched applications. The existing PWM strategies cannot be directly used for both matched and unmatched applications. However,the proposed PWM strategy can be general for both matched and unmatched applications, and no modifications are required. The effectiveness of the proposed PWM strategy is verified by experimental results.

Motion Error Compensation of Multi-legged Walking Robots

Existing errors in the structure and kinematic parameters of multi-legged walking robots,the motion trajectory of robot will diverge from the ideal sports requirements in movement.Since the existing error compensation is usually used for control compensation of manipulator arm,the error compensation of multi-legged robots has seldom been explored.In order to reduce the kinematic error of robots,a motion error compensation method based on the feedforward for multi-legged mobile robots is proposed to improve motion precision of a mobile robot.The locus error of a robot body is measured,when robot moves along a given track.Error of driven joint variables is obtained by error calculation model in terms of the locus error of robot body.Error value is used to compensate driven joint variables and modify control model of robot,which can drive the robots following control model modified.The model of the relation between robot＇s locus errors and kinematic variables errors is set up to achieve the kinematic error compensation.On the basis of the inverse kinematics of a multi-legged walking robot,the relation between error of the motion trajectory and driven joint variables of robots is discussed.Moreover,the equation set is obtained,which expresses relation among error of driven joint variables,structure parameters and error of robot＇s locus.Take MiniQuad as an example,when the robot MiniQuad moves following beeline tread,motion error compensation is studied.The actual locus errors of the robot body are measured before and after compensation in the test.According to the test,variations of the actual coordinate value of the robot centroid in x-direction and z-direction are reduced more than one time.The kinematic errors of robot body are reduced effectively by the use of the motion error compensation method based on the feedforward.

Optimal Load Balancing Leveling Method for Multi-leg Flexible Platforms

The working platforms supported with multiple extensible legs must be leveled before they come into operation.Although the supporting stiffness and reliability of the platform are improved with the increasing number of the supporting legs,the increased overdetermination of the multi-leg platform systems leads to leveling coupling problem among legs and virtual leg problem in which some of the supporting legs bear zero or quasi zero loads.These problems make it quite complex and time consuming to level such a multi-leg platform.Based on rigid body kinematics,an approximate equation is formulated to rapidly calculate the leg extension for leveling a rigid platform,then a proportional speed control strategy is proposed to reduce the unexpected platform distortion and leveling coupling between supporting legs.Taking both the load coupling between supporting legs and the elastic flexibility of the working platform into consideration,an optimal balancing legs’ loads(OBLL) model is firstly put forward to deal with the traditional virtual leg problem.By taking advantage of the concept of supporting stiffness matrix,a coupling extension method(CEM) is developed to solve this OBLL problem for multi-leg flexible platform.At the end,with the concept of supporting stiffness matrix and static transmissibility matrix,an optimal load balancing leveling method is proposed to achieve geometric leveling and legs’ loads balancing simultaneously.Three numerical examples are given out to illustrate the performance of proposed methods.This paper proposes a method which can effectively quantify all of the legs’ extension at the same time,achieve geometric leveling and legs’ loads balancing simultaneously.By using the proposed methods,the stability,precision and efficiency of auto-leveling control process can be improved.

Design and Analysis of a Multi-Legged Robot with Pitch Adjustive Units

The paper proposes a novel multi-legged robot with pitch adjustive units aiming at obstacle surmounting.With only 6 degrees of freedom,the robot with 16 mechanical legs walks steadily and surmounts the obstacles on the complex terrain.The leg unit with adjustive pitch provides a large workspace and empowers the legs to climb up obstacles in large sizes,which enhances the obstacle surmounting capability.The pitch adjustment in leg unit requires as few independent adjusting actuators as possible.Based on the kinematic analysis of the mechanical leg,the biped and quadruped leg units with adjustive pitch are analyzed and compared.The configuration of the robot is designed to obtain a compact structure and pragmatic performance.The uncertainty of the obstacle size and position in the surmounting process is taken into consideration and the parameters of the adjustments and the feasible strategies for obstacle surmounting are presented.Then the 3D virtual model and the robot prototype are built and the multi-body dynamic simulations and prototype experiments are carried out.The results from the simulations and the experiments show that the robot possesses good obstacle surmounting capabilities.

Non-Simultaneous Failure of Ice in Front of Multi-Leg Structures

Because the multi-leg jacket structure is the major type of offshore structures in the Bohai Sea, the study of non-simultaneous failure of ice on multi-leg structures is important. However, the non-simultaneous failure has not been considered in engineering design until now, obviously resulting in costly design and notable waste. To resolve this problem, this paper, by means of analysis of experimental data, calculates the coefficient of the non-simultaneous failure for the double-pile structure, the square four-leg structure, the single-line multi-pile structure, and the conical structure, respectively, and provides some reference criteria for engineering design.

Free gait generation method for omnidirectional locomotion on abrupt terrain with multi-legged biomimetic robot

In order to achieve omnidirectional locomotion on rough terrain with multi-legged biomimetic robot,a free gait generation approach is proposed based on local rules.The phase coordinates of each operation leg was established according to the motion task and a universal depiction of leg-end locomotion was implemented;the mathematical relation of gait pattern and walking velocity of multi-legged robot was put forward;combined polynomial curve was adopted to generate the leg-end trajectory,which was capable of accomplishing walking missions and accommodating to landform conditions;a distributed network of local rules for gait control was constructed based on a set of local rules operating between adjacent legs.In the simulation experiments,adaptive regulation of inter-leg phase sequence,omnidirectional locomotion and ground accommodation were realized.Moreover,statically stable free gait was obtained simultaneously,which provided multi-legged robot with the capability of walking on irregular terrain reliably and expeditiously.

Solving position-posture deviation problem of multi-legged walking robots with semi-round rigid feet by closed-loop control

The semi-round rigid feet would cause position-posture deviation problem because the actual foothold position is hardly known due to the rolling effect of the semi-round rigid feet during the robot walking. The position-posture deviation problem may harm to the stability and the harmony of the robot, or even makes the robot tip over and fail to walk forward. Focused on the position-posture deviation problem of multi-legged walking robots with semi-round rigid feet, a new method of position-posture closed-loop control is proposed to solve the position-posture deviation problem caused by semi-round rigid feet, based on the inverse velocity kinematics of the multi-legged walking robots. The position-posture closed-loop control is divided into two parts: the position closed-loop control and the posture closed-loop control. Thus, the position-posture control for the robot which is a tight coupling and nonlinear system is decoupled. Co-simulations of position-posture open-loop control and position-posture closed-loop control by MATLAB and ADAMS are implemented, respectively. The co-simulation results verify that the position-posture closed-loop control performs well in solving the position-posture deviation problem caused by semi-round rigid feet.

Analysis and control for a bioinspired multi-legged soft robot

Untethered soft miniature robots are considered to have a wide range of applications in biomedical field.However,researchers today still have not reached a consensus on its configuration design and actuation method.Here,inspired by the tentacles of a certain kind of echinodermata,we propose a soft multi-legged robot with a total weight of 0.26 g capable of multiple locomotion modes.Based on the magnetic field distribution of a square permanent magnet,we qualitatively analyze the motion mechanism of the robot.Finally,we carried out relevant experimental research.The research shows that the robot can move forward,backward,steering and cross obstacles under the control of the magnetic field,and can combine these abilities to navigate the maze.

基于装卸顺序的中型机多航段协同配载优化

多航段、多经停的航空货运航班,飞行过程中需要合理控制飞机的重心(CG)位置,保持平衡状态,中转站装卸操作过程中需要避免额外装卸操作,减少时间和劳力浪费,因此,研究多航段航班的协同配载问题具有重要现实意义。根据航空器自身特点与集装器(ULD)装卸顺序,结合各航段飞机装载平衡与过站机场ULD装卸操作要求,通过协调分配各航段ULD和散货位置,建立了中型机联程航班多目标整数线性规划模型。模型考虑了ULD和散货的质量、体积及与舱位的匹配限制,航空器限重、舱位限重、舱位及区域累积限重、上下舱联合限重和CG位置的平衡限制,以及前后航段ULD和散货的连接性约束。根据造成中间机场额外装卸操作的2种原因,基于装卸顺序,提出装卸优化模型,通过ULD的舱内平移,优化了CG,减少了装卸次数。以B757-200F机型为例,在两装一卸、一装两卸和两装两卸3种场景下,采用商用求解器Gurobi,分别针对3种不同目标函数组合进行求解和分析对比。实验表明:所提模型可以有效协调过站货物的额外装卸次数,优化前后两航段的CG位置。

随机风荷载下陡峭山区长短腿输电塔多构件可靠度评估

长短腿输电塔在陡峭山区的输电线路工程中应用广泛,准确评估该结构体系中各个构件的可靠度水平对其维护加固具有重要意义。鉴于此,基于拟蒙特卡罗法开展了随机风荷载作用下陡峭山区中长短腿输电塔多构件可靠度分析。根据《架空输电线路杆塔结构设计技术规程》(DL/T 5486—2020),给出长短腿输电塔不同构件常见的5类失效模式及其功能函数;通过同时考虑材料和风荷载的随机性,采用拟蒙特卡罗法建立长短腿输电塔多构件可靠度分析框架;以某输送电压为500 kV的输电线路中长短腿输电塔为例,进行了多构件可靠度评估,并分析了不同塔腿级差、杆塔呼高以及设计风速对长短腿输电塔可靠指标的影响规律。分析结果表明:长短腿输电塔的所有构件可靠指标均在3.2以上,满足规范要求的Ⅱ级安全水准,短腿主材为长短腿输电塔最薄弱构件,可靠指标相比于长腿主材减小了23.25%,应予以重视;杆塔呼高每增大6 m,长短腿输电塔可靠指标最大下降3.37%,设计风速每增大1 m∙s^(-1),可靠指标最大降低2.83%;塔腿级差每增大3 m,可靠指标最大降低10.48%,建议杆塔设计时应尽量避免出现塔腿级差过大的情况。

模块化多足机器人腿部工作空间研究

为了使机器人能够适应复杂的工作环境,提出了一种新型模块化可重构多足机器人,其六条腿在正六边形躯体的六个面上均匀分布。机器人具有臂腿转换功能,机器人执行任务时,能够将腿转换成机械臂。首先,基于Denavit-Hartenberg(D-H)方法,建立机器人腿部的数学模型,并进行运动学分析。然后采用蒙特卡洛法对机器人的腿部工作空间进行求解,为后续机器人的运动控制、执行任务提供参考。

采用37.5■锦纶开发多功能弹力Legging面料

文章以37.5■锦纶科技纱线4.4 tex/34 f消光DTY为主纱,夹入2.2 tex黑氨纶材料,采用双面互锁的织造方式,开发出一款集抗菌、凉感、远红外、吸湿速干、防紫外线功能为一体的多功能弹力Legging针织面料。详细介绍该面料的原料选择、织造工艺以及染整工艺,并对面料的基本性能进行测试。结果表明,该面料具有较好的多项功能以及优良的包覆性能,可以满足女子多场景的运动与穿着舒适性的相关需求。

一种开闭链混合的多模式移动轮腿机器人设计与仿真研究

为提高机器人通过复杂环境的能力,设计了一款新型轮腿机器人。首先对机器人整机进行了构型设计和运动模式分析;然后对其腿部机构进行了运动学分析,并针对常见障碍地形进行了机器人越障性能分析;最后进行虚拟样机仿真,仿真结果验证了机器人具有较强的越障能力。

Undulatory gait planning method of multi-legged robot with passive-spine

In this paper,we propose a new gait planning method for a multi-legged robot which has only 1 degree-of-freedom in each leg and has a passive body joint between two body segments.We firstly introduce the Finite State Machine(FSM)to the undulatory gait planning method of the 2n-legged robot.Then,the undulatory gait sequence for straight line motion is achieved by undulations motion.The idea that legged locomotion is achievable by less actuation of 2n-legged robot as well as the gait planning methods are verified finally by simulations and experiments.

可调足式机器人腿部机构设计

为实现腿部机构足端轨迹多样化以增强足式机器人地面适应性,同时提高其运动稳定性,课题组基于曲柄摇杆和曲柄滑块机构设计了一种可调整足式机器人腿部机构。采用解析法对该机构进行了运动学分析,建立了以理想的足端轨迹为设计要求的单目标优化模型,考虑了腿部机构运动过程中的平稳性,引入了速度波动指标,以轨迹-速度为设计目标,采用NSGA-Ⅱ多目标优化方法对机构进行优化,对优化结果进行了对比分析;基于多目标优化结果建立了腿部机构的足端轨迹库,并进行腿部机构多步态分析;以该腿部机构构建4足机器人三维模型,运用ADAMS对整机进行运动仿真。研究结果表明:多目标优化比单目标优化的轨迹误差增大了0.16%,而速度波动降低了5.84%;多目标优化与已有相关研究相比,速度波动幅值降低了25.44 mm/s。4足机器人三维模型仿真结果验证了可调整腿部机构的设计具有可行性。

基于手脚融合功能的多足步行机器人正运动学分析

简单介绍了一种新型机器人——基于手脚融合功能的多足步行机器人的结构,并对该类机器人的正运动学问题进行了详细研究。对该类机器人的两种典型运动状态——行走和抓取状态的运动学关系进行了阐述。文中首先根据机器人结构的约束关系导出了机器人机体轨迹(质心)的表达式,再对具有抓取功能的串联机械手的正运动学关系进行研究后,获得了机器人在抓取物体时的运动学关系。文中对相关公式进行了推导,给出了表达式,最后以相关算例进行了说明。该研究结果对于加快该类机器人的实用进程有显著意义。

模块化多足步行机器人的运动控制系统研究

为解决机器人对复杂多变的环境适应性不强的问题,研制了模块化的多足步行机器人系统。针对模块化多足步行机器人的机构特点,设计并实现了一种位于机器人模块化控制体系底层的基于CAN总线的运动控制系统。采用微处理器、专用的运动控制和驱动芯片以及光电编码器实现了机器人关节的伺服闭环运动控制;采用CAN总线作为模块间的通信接口,有效地支持了多关节实时控制。提出了一种具有3层抽象结构特点的可扩展的软件体系结构,为运动控制系统提供模块化支持。实验验证了运动控制系统软硬件的可靠性和有效性。

多管真空循环脱气系统循环流动模型

发展一个分析两管和多管真空循环脱气系统的循环流动特征数学模型．采用空间变密度的均相流模型模拟上升管中的气液两相流动，使用纯液相和气液两相之间的密度差作为系统中循环流动的驱动力，上升管中的气相体积分率是通过移植和修正喷气搅拌钢包含气率模型获得．利用空度技术处理包括钢包、真空室、上升管和下降管在内的复杂几何系统的流场计算．使用本模型对两管和多管真空循环脱气系统在喷气量为 ５－３５ Ｌ／ｍｉｎ情况下进行数值模拟．计算的下降管出口处的速度分布与文献中的测量值很接近．分析计算结果表明，多管系统中的速度分布比两管系统的速度分布均匀，即在下降管面积相同的情况下，多管系统的循环流量大于两管系统的循环流量．示踪剂扩散的模拟结果亦清楚展示了两种系统中流动特征的差别．

三相多芯柱变压器暂态仿真新模型

在变压器等效电路基础上提出了新的三相多芯柱变压器暂态仿真模型。仿真模型由基本的电路元件构成,不需要编写接口程序,应用方便;模型结构简单,所使用的电感参数少;新的模型中漏感参数和反应铁心磁路的励磁电感参数互相独立,不涉及病态矩阵的运算,计算更为稳定。通过三相三柱式和三相五柱式变压器的磁等值回路,讨论了模型中各参数的确定方法。通过与UMEC模型的比较验证了所提模型的准确性。

基于ADAMS的四足机器人运动仿真研究

作为工业机器人的一个主要研究分支,多足机器人具有很强的环境适应性和运动灵活性,正在日益受到重视。应用三维建模软件UG建立了四足机器人的模型,导入到虚拟样机分析软件ADAMS中生成虚拟样机模型,并对四足机器人进行了步态规划,利用MATLAB计算得到机器人关节运动轨迹,导入到ADAMS中,模拟了机器人的实际运动状态,得到其爬行轨迹。利用虚拟样机进行仿真为多足机器人步态规划的研究提供了一种良好的试验方法。