基于足地接触特性辨识的六足机器人自适应阻抗控制

为提高足式机器人在未知地面环境中运动适应能力,提出了一种基于足地接触特性辨识的模糊自适应阻抗控制算法.首先,针对六足机器人提出一种足地接触特性辨识方法.为降低六足机器人行走时足地之间的冲击力,提出了一种六足机器人沿腿长方向基于足地接触参数的模糊自适应阻抗控制器.基于六足机器人在不平坦地面行走时的足地接触状态,建立机器人步态控制状态机及行走控制框架.通过六足机器人仿真模型,对足地接触特性辨识方法、模糊自适应阻抗控制器以及机器人行走控制框架进行仿真验证,并应用到"青骓"六足机器人样机进行实验验证.     

基于ADAMS的仿生四足机器人运动分析与仿真

在了解国外主要研究成果的基础上,对四足机器人的关键技术进行了总结与分析。运动控制是四足机器人设计的关键技术之一,运动分析是为设计灵活稳定的物理样机及步态规划提供依据。在分析了仿生四足机器人实现运动要求的基本姿态的基础上,设计仿生四足机器人的机械结构;利用ADAMS建立了系统的考虑仿生四足机器人足部与地面接触的仿真模型,对其进行步态规划,仿真获得了四足机器人的动态特性;根据仿真结果,判断了步态规划的正确性及其影响,分析了摆动腿与地面冲击加速度过大的原因并提出了优化方案。     

新型仿生六足机器人自由步态中足端轨迹规划

设计了一种具有变形关节和轮式足端的新型仿生六足机器人,该机器人具备轮式、爬行、步行等运动模式,有较好的灵活性及环境适应能力。运用矢量法构建了机器人运动学模型,并利用几何关系对模型进行求解。对机器人沿给定的路径执行自由步态时机器人所允许的最大步幅进行了分析。基于不同的地形条件,规划了抛物线和直线-抛物线两种足端轨迹。仿真结果表明,机器人在沿给定的路径执行自由步态时,抛物线和直线-抛物线两种足端轨迹规划方法合理、可行。     

足板驱动两栖机器人陆地运动研究

对足板驱动两栖机器人陆地运动进行研究,在分析足板驱动两栖机器人的运动学和动力学基础上,采用虚拟样机技术建立了考虑足板与地面接触的仿真模型。通过仿真研究了机器人做匀速运动时地面对足板的冲击以及电机驱动力矩的变化情况,从而指导电机选型和机械结构设计,同时为分析机器人系统的动态特性提供了依据。     

四足机器人对角小跑步态动态稳定步行足端非连续约束及动力学建模

将四足机器人对角小跑步态周期分为摆动相和支撑相,采用D-H坐标法进行四足机器人运动学建模分析,提出基于质心运动定理分析腿机构处于支撑相的足端非连续约束力,通过力雅可比矩阵建立足端约束力与关节广义驱动力的映射关系。考虑足端与环境间的非连续约束,建立了具有变拓扑机构、非连续约束等特征的四足机器人非线性动力学模型,并通过虚拟样机仿真验证了动力学理论分析的正确性,为提高四足机器人非结构环境的机动性和动态稳定性研究提供了参考。     

四足机器人在非规则地形上的路径规划

建立了非规则复杂地形环境的简化数学模型。结合地形环境的模型建立的问题的相关模型。基于启发式的遗传算法,进化选择不仅仅在交配繁殖阶段,更是融入了种群初始化阶段。通过对机器人连续轨迹的离散化建模,将复杂路径规划问题简化,实现了路径的高效自主优选。为四足机器人的静步态运动的全局路径规划建立了新的思路。     

基于危险指数最小化的机器人安全路径规划

为防止机器人在运动过程中与人相撞,提高机器人运动的安全性,本文提出一种基于危险指数最小化的机器人安全路径规划方法。该方法将危险指数与改进人工势场法融入到机器人的安全路径规划中。在人机共处的非结构化环境中,首先计算出机器人的危险指数,并以危险指数最小化为目标规划机器人的路径。建立了三自由度机器人与人共处仿真模型,通过路径规划仿真,结果表明,基于危险指数最小化的机器人安全路径规划,可以有效确保机器人工作环境中人的安全性。     

基于旋量理论的四足机器人运动学分析

在调研分析当前足式机器人的研究进展的基础上,提出一种基于旋量理论的四足机器人运动学建模方法.运用旋量理论建立其运动学模型,建立各个关节的速度螺旋后根据罗德里格斯公式推导出该四足机器人的正运动学显式解析解,运用空间几何方法推导出该四足机器人的逆运动学显式解析解.最后运用专业多体动力学仿真软件Adams对所设计的四足机器人进行运动学仿真分析,验证了运动学理论推导的正确性及改四足机器人设计的合理性.提出四足机器人运动学算法的显式解析解,特别适用于对四足机器人控制有实时性要求的应用场景,为足式机器人的实时控制打下坚实的算法基础.该四足机器人运动学算法对后续的四足机器人甚至足式机器人的动力学、轨迹规划、步态规划研究都具有重要的参考意义.     

基于旋量理论的四足机器人运动学分析

在调研分析当前足式机器人的研究进展的基础上,提出一种基于旋量理论的四足机器人运动学建模方法.运用旋量理论建立其运动学模型,建立各个关节的速度螺旋后根据罗德里格斯公式推导出该四足机器人的正运动学显式解析解,运用空间几何方法推导出该四足机器人的逆运动学显式解析解.最后运用专业多体动力学仿真软件Adams对所设计的四足机器人进行运动学仿真分析,验证了运动学理论推导的正确性及改四足机器人设计的合理性.提出四足机器人运动学算法的显式解析解,特别适用于对四足机器人控制有实时性要求的应用场景,为足式机器人的实时控制打下坚实的算法基础.该四足机器人运动学算法对后续的四足机器人甚至足式机器人的动力学、轨迹规划、步态规划研究都具有重要的参考意义.     

液压驱动六足机器人一种低冲击运动规划方法

足地接触冲击对大尺度重载足式机器人的运动性能影响显著。针对液压驱动六足机器人,以低冲击平顺运动为目标,提出一种减小足地接触冲击的足端轨迹规划方法。基于仿生构型和运动学模型推导腿部关节的角度函数,根据液压缸铰点布置和腿部机构几何关系推导出各液压缸活塞杆的位置控制函数,分析表明关节和液压缸运动平稳,速度、加速度无突变。基于Vortex搭建机器人仿真平台,采用该方法实现了步行过程的仿真模拟,机体稳定前移过程中的垂向起伏微小,侧向偏移率约为2.1%。将该方法应用于开发的六足机器人原理样机,进行野外自然环境行走测试,各关节按预定轨迹平稳运动,足端受力合理。仿真结果与试验结果具有较好的一致性,验证了提出的运动规划方法合理可行。     

转动C形腿与沙土作用建模及力学参数辨识

机器人足端与沙土相互作用力学模型的建立和参数辨识，是沙土表面步行移动机器人多模态感知和决策的重要约束条件和物理信息。C形腿构型在沙土表面具有高通过性和适应性，基于地面动力学中的抵抗力学理论，充分考虑C形腿在摆动步态条件下位姿和速度矢量对足地相互作用动态力学的影响，进而建立C形腿与沙土的相互作用力学模型。然后，通过三组宽度条件的C形腿与沙土表面的转动接触力学试验，提取数据并分析水平和竖直接触力随姿态角度的变化规律。然后，通过积分模型的解析推导获得线性表达形式，基于递归最小二乘算法对未知参数矩阵进行逐项推导。最后，基于逐项迭代输入输出矩阵函数，获得参数在已有数据样本容量空间内的辨识结果。与试验结果相比，辨识后的预测竖直力和水平力误差分别为4.05%和4.22%，验证参数辨识的准确性和有效性。辨识的参数能够反映沙土地面的部分物理特征，基准值则反映腿部几何构型对力学模型的影响。     

软体足式机器人驱动、建模与仿真研究综述

软体足式机器人因其优越的移动性能及面对复杂地形的通过能力受到越来越多研究者的关注。由于受到材料性质、驱动方法及制造工艺等多方面的限制,如何实现软体足式机器人的创新结构设计,提升软体机器人的运动速度和负载能力是目前亟待解决的问题之一。综述从仿生结构与驱动方法的角度对目前软体足式机器人的研究发展进行了系统阐述。由于软体机器人多为连续变形结构,加之软材料的物理非线性和软结构变形的几何非线性,力学建模与仿真一直是软体机器人研究领域的瓶颈。梳理了目前软体机器人的主要建模理论,总结了软体机械臂的建模与控制方法,进一步将其拓展到软体足式机器人的系统建模中。介绍了传统商业软件的应用与物理仿真引擎开发的进展,分析了软体机器人虚拟仿真的主要方法,展望了软体足式机器人的应用场景与未来研究方向。     

Biped walking robot based on a 2-UPU+2-UU parallel mechanism

Existing biped robots mainly fall into two categories： robots with left and right feet and robots with upper and lower feet. The load carrying capability of a biped robot is quite limited since the two feet of a walking robot supports the robot alternatively during walking. To improve the load carrying capability, a novel biped walking robot is proposed based on a 2-UPU＋2-UU parallel mechanism. The biped walking robot is composed of two identical platforms（feet） and four limbs, including two UPU（universal-prismatic-universal serial chain） limbs and two UU limbs. To enhance its terrain adaptability like articulated vehicles, the two feet of the biped walking robot are designed as two vehicles in detail. The conditions that the geometric parameters of the feet must satisfy are discussed. The degrees-of-freedom of the mechanism is analyzed by using screw theory. Gait analysis, kinematic analysis and stability analysis of the mechanism are carried out to verify the structural design parameters. The simulation results validate the feasibility of walking on rugged terrain. Experiments with a physical prototype show that the novel biped walking robot can walk stably on smooth terrain. Due to its unique feet design and high stiffness, the biped walking robot may adapt to rugged terrain and is suitable for load-carrying.     

An improved force-based impedance control method for the HDU of legged robots

Hydraulic drive mode enables legged robots to have excellent characteristics, such as greater power-to-weight ratios, higher load capacities, and faster response speeds than other robots. Nowadays, highly integrated valve-controlled cylinder, called hydraulic drive unit (HDU), is employed to drive the joints of these robots. However, various robot control issues exist. For example, during the walking process of legged robots, different obstacles are encountered, making it difficult to control such robots because the load characteristics of the ends of their feet change with the environment. Furthermore, although the adoption of HDU has resulted in high-performance robot control, the hydraulic systems of these robots still have problems, such as strong nonlinearity, and time-varying parameters. Consequently, robot control is very difficult and complex. This paper proposes an improved second-order dynamic compliance control system, impedance control, for HDU. The control system is designed to rectify the issues affecting the impedance control accuracy of the dynamic compliance serial–parallel composition between the HDU force control inner loop and the impedance control outer loop. Specifically, it consists of a compliance-enhanced controller and a feedforward compensation controller for the force control inner loop. Furthermore, the dynamic compliance composition of the inner and outer HDU control loops is rearranged. The results of experiments conducted indicate that the proposed method significantly improves the control accuracy compared to that of traditional force-based impedance control.     

动态环境下移动机器人路径规划的改进蚁群算法

研究动态环境下移动机器人路径规划问题,采用栅格法对机器人工作空间进行建模,在使用蚁群算法进行全局路径搜索过程中引入人工势场的概念,使蚂蚁对最优路径更加敏感;机器人针对动态环境中可能出现的不同类型障碍物分别执行不同的避障策略;同时提出一种最优路径预测模型用于预测在避障过程中是否出现新的最优路径。算法结合人工势场法和蚁群算法的特点,将全局路径规划与局部路径规划相融合以提高路径搜索的效率。仿真结果验证了该算法的有效性。     

Learning gait of quadruped robot without prior knowledge of the environment

Walking is the basic skill of a legged robot, and one of the promising ways to improve the walking performance and its adaptation to environment changes is to let the robot learn its walking by itself. Currently, most of the walking learning methods are based on robot vision system or some external sensing equipment to estimate the walking performance of certain walking parameters, and therefore are usually only applicable under laboratory condition, where environment can be pre-defined. Inspired by the rhythmic swing movement during walking of legged animals and the behavior of their adjusting their walking gait on different walking surfaces, a concept of walking rhythmic pattern(WRP) is proposed to evaluate the walking specialty of legged robot, which is just based on the walking dynamics of the robot. Based on the onboard acceleration sensor data, a method to calculate WRP using power spectrum in frequency domain and diverse smooth filters is also presented. Since the evaluation of WRP is only based on the walking dynamics data of the robot’s body, the proposed method doesn’t require prior knowledge of environment and thus can be applied in unknown environment. A gait learning approach of legged robots based on WRP and evolution algorithm(EA) is introduced. By using the proposed approach, a quadruped robot can learn its locomotion by its onboard sensing in an unknown environment, where the robot has no prior knowledge about this place. The experimental result proves proportional relationship exits between WRP match score and walking performance of legged robot, which can be used to evaluate the walking performance in walking optimization under unknown environment.     

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.     

Real time traversability analysis to enhance rough terrain navigation for an 6 × 6 autonomous vehicle

An autonomous vehicle should be driven at a velocity that allows it to feasibly track a predetermined path. For autonomous vehicles that require high velocity navigation over rough terrain, the driving velocity should be calculated in real time and maximized without exceeding any safety limits. In order to compute the driving velocity in real time, several factors including path curvature, terrain characteristics, vehicle dynamics, and interaction between vehicle and terrain need to be taken into account, along with real time constraints. In this study, a method based on real time traversability analysis is proposed to determine the maximum permissible velocity at which an autonomous vehicle can traverse rough terrain with guaranteed stability. Simulations validated the proposed method for a 6 × 6 autonomous vehicle with articulated suspension traveling over rough terrain.     

Type Design and Behavior Control for Six Legged Robots

The research on legged robots attracted much attention both from the academia and industry. Legged robots are multi-input multi-output with multiple end-e ector systems. Therefore,the mechanical design and control framework are challenging issues. This paper reviews the development of type synthesis and behavior control on legged robots; introduces the hexapod robots developed in our research group based on the proposed type synthesis method. The control framework for legged robots includes data driven layer,robot behavior layer and robot execution layer. Each layer consists several components which are explained in details. Finally,various experiments were conducted on several hexapod robots. The summarization of the type synthesis and behavior control design constructed in this paper would provide a unified platform for communications and references for future advancement for legged robots.     

移动机器人在线实时路径规划

研究了不确定环境下移动机器人的路径规划问题。采用全局规划和局部规划相结合的方法，提出了一种基于极坐标空间，以期望方向角为优化性能指标的在线实日寸路径规划方法。该法利用机器人的传感器系统，实时探测局部环境信息，在每次的局部规划窗口，确定机器人的期望方向角，以机器人的实际运动方向角与期望方向角之间的差异来驱动机器人避开障碍物和朝向目标点运动。该法不仅简单灵活，而且克服了全局规划和局部规划的缺陷。仿真实验表明其有效可行性、实时性、优化性、精度高、稳定性好。