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.     

五自由度并联机械腿静力学性能评价与优化设计

为了对一种六足机器人的五自由度并联机械腿进行静力学性能评价和优化设计,提出了一种同时考虑约束力映射关系和驱动力映射关系的腿部机构静力学分析方法,并基于此方法对机械腿进行了优化设计.首先,通过分析腿部机构的驱动、约束映射关系,分别建立了腿部机构的驱动雅可比矩阵和约束雅可比矩阵;应用虚功原理建立了腿部机构的驱动静力传递平衡方程,在定义驱动静力学评价指标的基础上绘制了评价指标分布图,得出了结构参数与驱动静力评价指标之间的关系曲线.然后,采用同样的方法建立了腿部机构的约束静力传递平衡方程,定义了约束静力学性能评价指标,得出了结构参数与约束静力评价指标之间的关系曲线.最后,基于驱动、约束静力学性能评价指标,采用蒙特卡罗法对结构参数进行了优化设计.计算表明,固定平台结构参数a为200mm、运动平台结构参数b为80 mm,UPU支链长度l1min,l3max分别为500mm、900mm时,腿部机构的静力学综合性能最好.     

基于ADAMS的一种六足移动机器人的设计与研究

针对复杂环境对机器人的移动要求,提出了一种新型六足移动机器人的设计思想.设计了机器人的主要结构,对该机器人的设计进行阐述,并分析了其越障构态的变化特点.用静力学方法对机器人进行了越障理论分析,建立了六足机器人参数化模型,经ADAMS对机器人进行机构运动仿真,获得了机器人运动学特性曲线,为机器人总体系统设计与数值计算提供了参考依据.     

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。     

Novel Door-opening Method for Six-legged Robots Based on Only Force Sensing

Current door-opening methods are mainly developed on tracked, wheeled and biped robots by applying multi-DOF manipulators and vision systems. However, door-opening methods for six-legged robots are seldom studied, especially using 0-DOF tools to operate and only force sensing to detect. A novel door-opening method for six-legged robots is developed and implemented to the six-parallel-legged robot. The kinematic model of the six-parallel-legged robot is established and the model of measuring the positional relationship between the robot and the door is proposed. The measurement model is completely based on only force sensing. The real-time trajectory planning method and the control strategy are designed. The trajectory planning method allows the maximum angle between the sagittal axis of the robot body and the normal line of the door plane to be 45º. A 0-DOF tool mounted to the robot body is applied to operate. By integrating with the body, the tool has 6 DOFs and enough workspace to operate. The loose grasp achieved by the tool helps release the inner force in the tool. Experiments are carried out to validate the method. The results show that the method is effective and robust in opening doors wider than 1 m. This paper proposes a novel door-opening method for six-legged robots, which notably uses a 0-DOF tool and only force sensing to detect and open the door.     

Tripod gait-based turning gait of a six-legged walking robot

The turning gait planning and improvement methods of a six-legged walking robot on the basis of tripod gait are presented in this study. A projection method that considers an unstructured environment is proposed for the turning gait planning of the six-legged walking robot. The body and foot motion trajectories of the swing legs are planned with polynomial curves to keep the robot steady while walking. Two basic turning gaits, namely, circling and spinning gaits, are successfully designed with the planning method. An optimized method is proposed to improve the turning angle, which is subjected to stability, kinematics, and relief amplitude constraints in the unstructured environment. The turning ability of the turning gait is improved with the optimized turning angle. The circling and spinning gaits are implemented in simulations and experiments. Results demonstrate that the planning and improvement methods for the turning gait are valid and correct.

     

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.     

一种简易足式移动机器人

描述了一种结构简单的双三角足式移动机器人，分析了该机构的行走步态及控制原理。该机构模仿六足昆虫的行走步态，具有三个自由度，分别由三个直流电机控制。电位器可实现单片机对直流电机的闭环控制，反射式光电传感器和行程开关使得六足机构自身具有一定的反应能力。对样机进行了实验，实验结果表明该机构机动性好，运动平稳。     

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.     

六足步行机的稳定性监控系统

本文综合了各种地形条件下的六足步行机的静态稳定性方法,详细讨论了能量稳定法,并用这种方法分析了六足步行机的越野能力,研究了六足机转向时的步态选择及其稳定性,给出了六足机总体结构尺寸的一种CAD方法,设计了一个适于各种地形条件的六足步行机的稳定性监控系统。     

六足步行机缩放式腿机构的机械设计

本文详细讨论了用于六足步行机器人的缩放式步行机构的选型及其结构参数的选择,给出了这种缩放机构的传动系统及机械结构的设计,为研制实用的六足步行机器人步行机构提供了设计依据。     

Stiffness analysis and optimization in robotic drilling application

Low stiffness characteristics limit the application of industrial robots in the field of precision manufacturing. This paper focuses primarily on the stiffness properties of drilling robots by further studying the stiffness ellipsoid model. A Cartesian compliance model is proposed to describe the robot stiffness in Cartesian space. Based on the compliance model, a quantitative evaluation index of the robot’s processing performance is defined. By choosing a proper drilling posture, the performance index in the cutting tool direction is optimized. Higher accuracy of the countersink depth and hole axial direction can be guaranteed. From the perspective of the robot processing mechanism, the key role of the per-load pressing force is first indicated. By applying a per-load pressing force, the performance index on the machining plane is enhanced. Hole diameter accuracy is improved significantly. A stiffness improving factor used to evaluate the stiffness promotion degree is also proposed. Finally, experiments were conducted to verify the correctness of the proposed model. Drilling experiments were performed to investigate the effectiveness of the robot processing performance index improving methods The principle of pressing force used in engineering applications is given based on processing parameters.     

A study on tracking error based on mechatronics model of a 5-DOF hybrid spray-painting robot

Industrial robots suffer from difficulties in predicting and guaranteeing tracking performance due to the complex dynamic behavior and inaccurate mechatronics model. This study investigates the tracking error and motion accuracy improvement based on a mechatronics model of a 5-degree of freedom hybrid spray-painting robot. The dynamic model of the robot is derived by using Lagrange equation, and an identification method is presented to identify the torque coefficient and joint friction synchronously. An accurate mechatronics model is established after the theoretical dynamic modeling and friction identification. The tracking error generation mechanism of the robot control system is studied, and its analytical equation is derived on the basis of a transfer function. A multichannel feedforward controller is synthesized to reduce the tracking error from different sources. The effectiveness of the proposed method in improving tracking accuracy is verified by physical experiments.

     

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.     

空间多关节六足步行机超确定输入能量最优解析

本文讨论了空间多关节六足步行机的能量合理分配问题,文中首先导出六足步行机的速度、加速度和惯性力的解析计算公式,在此基础上着重讨论步行机输入量多于自由度的超确定输入问题,导出了超确定输入的协调方程和最优能量分配方程。     

六足仿生机器人运动控制系统的设计

以目前存各种领域得到广泛应用的机器人为研究对象,通过实践中对六足昆虫的观察,得出三角步态的稳定性分析,构建出六足机器人的基本运动模型.用Atmel系列单片机作为控制器,采用模块化递阶控制技术融合传感器技术完成对六足仿生机器人的运动控制策略的设计和试验.试验结果表明该机器人具有良好的稳定性和机动性.     

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.     

六足步行机缩放式腿机构的计算机辅助设计

本文分析了六足步行机圆柱型缩放式腿机构的运动规律及其受力状况,并结合机构的运动空间、六足步行机的最佳机体高度及结构约束等条件,给出了一种合理选择这种机构各设计参数的优化设计方法及计算实例。     

Static Force Analysis of Foot of Electrically Driven Heavy-Duty Six-Legged Robot under Tripod Gait

The electrically driven six-legged robot with high carrying capacity is an indispensable equipment for planetary exploration, but it hinders its practicability because of its low efficiency of carrying energy. Meanwhile, its load capacity also affects its application range. To reduce the power consumption, increase the load to mass ratio, and improve the stability of robot, the relationship between the walking modes and the forces of feet under the tripod gait are researched for an electrically driven heavy-duty six-legged robot. Based on the configuration characteristics of electrically driven heavy-duty six-legged, the typical walking modes of robot are analyzed. The mathematical models of the normal forces of feet are respectively established under the tripod gait of typical walking modes. According to the MATLAB software, the variable tendency charts are respectively gained for the normal forces of feet. The walking experiments under the typical tripod gaits are implemented for the prototype of electrically driven heavy-duty six-legged robot. The variable tendencies of maximum normal forces of feet are acquired. The comparison results show that the theoretical and experimental data are in the same trend. The walking modes which are most available to realize the average force of distribution of each foot are confirmed. The proposed method of analyzing the relationship between the walking modes and the forces of feet can quickly determine the optimal walking mode and gait parameters under the average distribution of foot force, which is propitious to develop the excellent heavy-duty multi-legged robots with the lower power consumption, larger load to mass ratio, and higher stability.     

6足步行机的控制系统设计及运动仿真

针对一种空间闭链RSTR机构六足步行机,通过机构运动分析,合理规划其运动轨迹;成功搭建控制系统,实现了步行机行走、遇障碍自动停止的功能;利用ADAMS进行运动学仿真分析,得出结论：六足步行机基本能维持静态稳定步行,整个步行机行走过程中实现了其连续运动,且行走轨迹基本为直线,并能保持一个较高的静态稳定移动速度。