Force distribution of a six-legged walking robot with high constant speed

For a walking robot with high constant body speed, the dynamic effects of the legs on the transfer phase are dominant compared with other factors. This paper presents a new force distribution algorithm to maximize walkable terrain without slipping considering the dynamic effects of the legs on the transfer phase. Maximizing the walkable terrain means having the capability of walking on more slippery ground under the same constraint, namely constant body speed. A simple force distribution algorithm applied to the proposed walking model with a pantograph leg shows an improvement in the capability of preventing foot-slippage compared with one using a pseudo-inverse method.     

Typical gait analysis of a six-legged robot in the context of metamorphic mechanism theory

The equivalent mechanism of the system is often considered as one specific mechanism in most existing studies of multi-legged robots, however the equivalent mechanism is varying while the robot moves on the ground. Four typical tripod period gaits of a radial symmetrical six-legged robot are analyzed. Similar to the metamorphic mechanism, the locomotion of multi-legged robot is considered as a series of varying hybrid serial-parallel mechanisms by assuming the constraints of the feet on the ground with hinges. One gait cycle is divided into several periods, and in different walking period there is a specific equivalent mechanism corresponding to it, and the walking process of multi-legged robot is composed by these series of equivalent mechanisms. Walking performance can be got by analyzing these series of equivalent mechanisms. Kinematics model of the equivalent mechanism is established, workspaces of equivalent mechanisms are illustrated by simulation and a concept of static stability workspace is proposed to evaluate the static stability of these four gaits. A new method to calculate the stride length of multi-legged robots is presented by analyzing the relationship between the workspace of two adjacent equivalent parallel mechanisms in one gait cycle. The stride lengths of four gaits are given by simulations. Comparison of stride length and static stability among these four typical tripod gaits are given. It has been proved that mixed gait and insect-wave gait II have better static stability than mammal kick-off gait and insect-wave gait I. Insect-wave gait II displays its advantage on stride length while the height of robot body lower than 87 mm, mammal kick-off gait has superiority on stride length while the height of robot body higher than 115 mm, and insect-wave gait I shows its shortcoming in stride length. The proposed method based on metamorphic theory and combining the footholds and body height of robot provides a new method to comprehensive analyze the performance of multi-legged robot.     

一种用于多足步行机器人步态控制的CPG模型

基于对生物节律性周期运动的CPG控制的概念,采用Lakshmanan和Murali的双变量简化Hodgkin-Huxley振荡神经元模型作为CPG的振子。对该模型进行了不动点及稳定性分析和分岔分析,指出了其二次Hopf分岔特性和振荡条件。在此基础上,建立了一种用于八足步行机器人步态控制的CPG模型。通过分阶段遗传算法,分别针对几种步态进行了参数优化,通过仿真验证了所提出的CPG模型的可行性。     

六足机器人模块化结构设计

为实现性能优越而结构简单的六足移动设想,通过对六足机器人进行步态和传动结构特征的分析,提出了六足机器人模块化结构设计方案,并利用Solidworks完成了各模块及机器人的整体构型。最后,对其结构特征进行了分析,论证了该六足机器人的特性和优势。研究结果表明,该模块化结构设计方案有助于推动六足机器人的广泛应用。     

教学型双足步行机器人直线行走步态稳定规划方法

通过对双足机器人行走步态的研究,利用多项式插值法对双足机器人直线行走步态进行规划,分析了踝关节轨迹和髋关节轨迹,通过调节单腿支撑期和双腿支撑期的比例系数来调整机器人的行走步态,使其实现稳定步行。再通过ADAMS建立虚拟样机仿真实验,验证了这种步态规划方法的正确性与可行性。     

六足步行机器人的并联机械腿设计

将并联机构用于六足步行机器人的腿部结构,以拓展六足步行机器人的应用领域.提出了一种基于(U+UPR)P+ UPS机构的并联机械腿,并对机械腿进行了结构参数设计.首先,对腿部机构进行了运动学分析,推导出了腿部机构的位置反解方程和速度传递方程;分析了腿部机构的工作空间并绘制了工作空间三维图,定义了工作空间性能评价指标,绘制了结构参数与工作空间性能指标的关系曲线.然后,对腿部机构进行了运动灵活性分析并绘制了雅克比矩阵条件数分布图,定义了运动灵活性评价指标,绘制了结构参数与运动灵活性指标的关系曲线.最后,基于工作空间性能指标和运动灵活性指标,采用蒙特卡罗法进行了结构参数分析,选取了一组性能较好的结构参数并考虑加工和装配工艺性,设计了一种新型3自由度并联机械腿的虚拟样机,为六足步行机器人的进一步研究奠定了基础.     

六足机器人机构优化设计及运动仿真分析

针对多连杆组合机器人驱动复杂性问题,对一种齿轮—连杆组合机构的六足机器人进行优化设计。采用优化算法对腿部各连杆尺度进行了优化分析并进行了运动学仿真,在相同工况下分别对机器人直线行走、曲线行走以及直线—曲线行走的质心轨迹、关节的角速度、角加速度进行分析并对比优化前与优化后实验数据。实验结果表明,六足机器人机构设计符合实际情况,模型优化的合理性与准确性得到进一步验证,进而为以后多足机器人更深入研究奠定基础。     

A novel six-legged walking machine tool for in-situ operations

Frontiers of Mechanical Engineering - The manufacture and maintenance of large parts in ships, trains, aircrafts, and so on create an increasing demand for mobile machine tools to perform in-situ...     

Method for analyzing articulated torques of heavy-duty six-legged robot

The accuracy of an articulated torque analysis influences the comprehensive performances of heavy-duty multi-legged robots. Currently, the extremal estimation method and some complex methods are employed to calculate the articulated torques, which results in a large safety margin or a large number of calculations. To quickly obtain accurate articulated torques, an analysis method for the articulated torque is presented for an electrically driven heavy-duty six-legged robot. First, the rearmost leg that experiences the maximum normal contact force is confirmed when the robot transits a slope. Based on the ant-type and crab-type tripod gaits, the formulas of classical mechanics and MATLAB software are employed to theoretically analyze the relevant static torques of the joints. With the changes in the joint angles for the abductor joint, hip joint, and knee joint, variable tendency charts and extreme curves are obtained for the static articulated torques. Meanwhile, the maximum static articulated torques and the corresponding poses of the robot are also obtained. According to the poses of the robot under the maximum static articulated torques, ADAMS software is used to carry out a static simulation analysis. Based on the relevant simulation curves of the articulated torques, the maximum static articulated torques are acquired. A comparative analysis of the maximum static articulated torques shows that the theoretical calculation values are higher than the static simulation values, and the maximum error value is approximately 10%. The proposed method lays a foundation for quickly determining accurate articulated torques to develop heavy-duty six-legged robots.     

Dynamics analysis of leg mechanism of six-legged firefighting robot

Journal of Mechanical Science and Technology - A novel 3-DOF Leg mechanism (LM), which consists of a 2RUS+RU PM, a space parallelogram mechanism and a connecting spherical joint is proposed. The LM...     

一种步行机器人结构分析

在介绍混合输入五杆机构输出轨迹可调的基础上，将混合输入五杆机构用作步行机器人腿部机构来提高其步行能力与柔性；同时将机器人控制系统、元器件、传感器密封在机体中，通过动密封轴传动驱动腿部机构实现步行，从而增强步行机器人的环境适应性。     

Human-tracking strategies for a six-legged rescue robot based on distance and view

Human tracking is an important issue for intelligent robotic control and can be used in many scenarios, such as robotic services and human-robot cooperation. Most of current human-tracking methods are targeted for mobile/tracked robots, but few of them can be used for legged robots. Two novel human-tracking strategies, view priority strategy and distance priority strategy, are proposed specially for legged robots, which enable them to track humans in various complex terrains. View priority strategy focuses on keeping humans in its view angle arrange with priority, while its counterpart, distance priority strategy, focuses on keeping human at a reasonable distance with priority. To evaluate these strategies, two indexes(average and minimum tracking capability) are defined. With the help of these indexes, the view priority strategy shows advantages compared with distance priority strategy. The optimization is done in terms of these indexes, which let the robot has maximum tracking capability. The simulation results show that the robot can track humans with different curves like square, circular, sine and screw paths. Two novel control strategies are proposed which specially concerning legged robot characteristics to solve human tracking problems more efficiently in rescue circumstances.     

Method for six-legged robot stepping on obstacles by indirect force estimation

Adaptive gaits for legged robots often requires force sensors installed on foot-tips, however impact, temperature or humidity can affect or even damage those sensors. Efforts have been made to realize indirect force estimation on the legged robots using leg structures based on planar mechanisms. Robot Octopus III is a six-legged robot using spatial parallel mechanism(UP-2UPS) legs. This paper proposed a novel method to realize indirect force estimation on walking robot based on a spatial parallel mechanism. The direct kinematics model and the inverse kinematics model are established. The force Jacobian matrix is derived based on the kinematics model. Thus, the indirect force estimation model is established. Then, the relation between the output torques of the three motors installed on one leg to the external force exerted on the foot tip is described. Furthermore, an adaptive tripod static gait is designed. The robot alters its leg trajectory to step on obstacles by using the proposed adaptive gait. Both the indirect force estimation model and the adaptive gait are implemented and optimized in a real time control system. An experiment is carried out to validate the indirect force estimation model. The adaptive gait is tested in another experiment. Experiment results show that the robot can successfully step on a 0.2 m-high obstacle. This paper proposes a novel method to overcome obstacles for the six-legged robot using spatial parallel mechanism legs and to avoid installing the electric force sensors in harsh environment of the robot’s foot tips.     

A total torque index for dynamic performance evaluation of a radial symmetric six-legged robot

This article focuses on the dynamic index and performance of a radial symmetric six-legged robot. At first the structure of the robot is described in brief and its inverse kinematics is presented. Then the dynamic model is formulated as based on the Lagrange equations. A novel index of total torque is proposed by considering the posture of the supporting legs. The new index can be used to optimize the leg’s structure and operation for consuming minimum power and avoiding unstable postures of the robot. A characterization of the proposed six-legged robot is obtained by a parametric analysis of robot performance through simulation using the presented dynamic model. Main influences are outlined as well as the usefulness of the proposed performance index.     

The six-legged walking robot capable of terrain adaptationLe robot a six pieds marchant capable de l'adaptation au terrain

This paper presents some results of the development of the control system for a six-legged walking robot. New results on visual-and force-feedback are presented. Now the robot features the active compliance and can move over a terrain with a complex relief.     

Tripod robot with cylindrically actuated limbs: Structure and kinematics

The kinematic analysis of a novel tripod with six degrees of freedom is presented. The kinematic chains of the mechanism have an RCS structure. Two elements of each cylindrical pair C of the chain constitute a crank-type limb that carries out two controlled motions––rotation around and translation along the limb axis. The limb is connected passively to the fixed base and to the movable platform by rotational and spherical hinges, respectively. The structure, kinematics, working space and singular positions of the tripod are examined. Since three of the six active tripod motions are rotations, the inverse kinematics solution is non-unique; this, in turn, necessitates the choice of one of eight variants for the initial positions of the limbs and one of two directions for limb rotations.     

新型六足爬行机器人设计

采用了仿哺乳类的腿部结构,并针对这种腿部结构设计了六足的行走方式,通过对12个步进电机的控制,采用三角步态,实现了六足机器人的直行功能.仿真及试验证明,这种结构能较好地维持六足机器人自身的平衡,并且对今后更深入地研究六足机器人抬腿行走姿态及可行性,具有较高的参考价值.     

四足步行机器人稳定性分析

基于四足步行机器人模型对机器人的瞬时质心坐标进行了计算,得出了瞬时质心的运动规律,分析了各质量模块对机器人质心坐标的影响,对比了瞬时质心位移与几何中心位移的相对关系。给出了四足步行机器人静步态稳定性判定的公式,计算了基于瞬时质心的稳定裕度,并对稳定裕度进行了对比分析。     

双足溜冰机器人步态规划的研究

将ZMP稳定性理论应用到两足溜冰机器人的姿态稳定性分析中,得到了机器人溜冰运动的姿态稳定性判据.从仿生学的角度出发,提出了溜冰机器人的单腿蹬地溜冰步态,以稳定性分析为基础,对溜冰机器人的溜冰步态规划进行了研究,实验结果验证了步态规划方法的正确性.     

类人猿型机器人前向四足步行的研究

类人猿机器人是一种具有多种移动方式的新型机器人。同常规的四足步行机器人相比,该机器人的结构具有特殊性和复杂性。为了实现拥有这种结构机器人的前向四足步行,我们提出了新的步态、轨迹规划、稳定平衡判据。仿真和实验结果证实了这些分析的合理性。