一种基于并联6自由度结构的电动轮足机器人

针对现有基于串联式机械腿结构的四足机器人无法同时满足承载能力大、环境适应性强、运动速度快等要求的问题,提出了一种基于并联6自由度结构的电动轮足机器人结构原理,集成了轮式运动和足式运动各自的优势.在对机器人并联式轮腿进行运动学和动力学分析基础上,建立了单腿动力学模型和机器人整体运动学模型,提出了机器人机身姿态调整算法,有效提高了机器人运动过程中姿态的平稳性.仿真与实验验证了所提出的轮足复合式机器人的可行性和轮式运动时机器人机身姿态调整策略的有效性.     

一种六足步行机器人的自由步态算法

本文探讨了适用于六足步行机器人的步态类型和机器人腿运动的三个约束条件,提出了一种适用于六足步行机器人在不规则地形上运动的自由步态算法.机器人在大部分的地形状况下以标准模式行走.当标准模式失效时,则采用自适应模式,对机器人状态进行调整,以实现正常的行走运动.在保证运动速度和能量效率的前提下,使机器人具备良好的地形适应能力.最后,文章给出了算法的程序流程图,并在MATLAB下进行了仿真验证.     

电动并联六轮足机器人的运动驱动与多模态控制方法

提出一种并联六轮足移动机器人．该机器人设有多模式Stewart型腿结构,其负载能力大,集成了轮式运动和足式运动的优点,可实现足式、轮式、轮足复合式运动．首先,阐述了机器人设计思路,对电动并联六轮足机器人的硬件系统和控制系统进行设计．其次,针对足式运动模式,设计了一套完整的足式“三角”步态和稳定行走算法,该算法可降低足端与地面之间的垂直方向冲击,防止足式运动拖腿或打滑;针对轮式运动模式,设计并介绍了6轮协同控制和轮式协同转向原理;针对轮足复合式运动模式,介绍了变高度、变支撑面、变轮距、主动隔振控制原理,重点分析了主动隔振控制和变轮距控制,可实现主动隔振及姿态平稳控制,提高了机器人在崎岖颠簸地形下的轮足复合式运动的稳定性．最后,对电动并联六轮足机器人的足式、轮式、轮足复合式运动模式进行实验,实验结果验证了本文提出的并联六轮足移动机器人设计的可行性和各运动模式下驱动与控制算法的有效性．     

连续不规则台阶环境四足机器人步态规划与控制

为了实现四足机器人在无崎岖地形先验知识情况下的自主爬行,提出了一种四足机器人运动控制方法.该方法采用间歇爬行步态作为主步态,将爬行运动分解为若干任务分别进行控制:基于NESM(normalized energy stability margin)判据计算内外倾的稳定裕度并根据其比值进行质心位置调整;使用坐标映射的方式调整足端坐标进行地面坡度适应;通过调整各腿长度控制机器人的高度;利用姿态传感器信息进行姿态恢复.仿真和实验表明,机器人仅依赖内部传感器即实现了在崎岖地形稳定行走,验证了本文方法的有效性和可靠性.     

六足机器人不规则地形下的运动规划算法研究

以六足类昆虫典型代表——蚂蚁爬越障碍柱和障碍柱堆的两种运动过程及其特点为分析对象,总结了蚂蚁在应对不规则地形时的运动策略,建立了更为合理的六足机器人的运动学数学模型;并仿照蚂蚁在应对不规则地形时的运动策略,提出在进行仿生六足机器人运动规划时,可将地形划分为浅度不平地形和深度不平地形两种情况,进而针对两种地形情况提出了六足机器人在不规则地形条件下的运动规划算法。最后通过样机试验验证所提算法的有效性。     

一种粗糙地形下四足仿生机器人的柔顺步态生成方法

传统以刚体动力学为基础的四足机器人运动控制方法对地形误差敏感,无法适应粗糙复杂地形,因此提出一种基于虚拟模型的运动控制方法用于实现四足机器人在粗糙地形下的行走.建立了以足底接触力为约束的高层步行任务和底层运动控制的映射关系.采用弹簧-阻尼-质量虚拟模型对四足机器人进行建模,将四足机器人的步行任务用一系列作用于机体质心的虚拟力去表征,基于各足等效力矩平衡的原则,将笛卡儿空间的虚拟力矢量分配到各支撑足,利用雅可比矩阵把足端力矢量转换为机器人关节空间的关节转矩.针对崎岖的空间3维粗糙地形,建立了机器人躯干姿态与地形的关联参数,通过调整躯干姿态有效扩大了机器人对粗糙地形的适应程度.运动仿真结果表明,机器人可以实现粗糙地形下稳定连续的行走,足底接触力平稳、无冲击,证明了该柔顺步态生成方法的合理性和有效性.     

基于群论的六足机器人运动空间研究

针对六足机器人相对复杂的机械结构,提出一个简化模型结构,利用等条件约束把腿支链转化为滑动连杆.其次,针对简化后的模型,依据其运动约束方程,分析研究六足机器人可达空间以及姿态空间.在群论基础上,结合六足机器人的运动约束模型,着重分析机器人初始状态的对称性与其运动空间对称性的关系,并通过分层搜索算法,求解六足机器人运动空间.最后通过仿真数据分析六足机器人运动空间随不同参数调整的变化情况,对比分析机器人不同初始状态与其运动空间的关系,同时对运动平台的姿态空间及其截面进行分析.分析与仿真结果表明,利用群约束模型可以对复杂并联机器人运动空间进行更详尽的分析,得到包括空间对称性、姿态空间以及空间截面的详细信息.     

全方位六足步行机器人运动规划的相对运动算法

本文提出了步行机器人运动控制算法。该方法以相对运动学原理为基础,把机体的运动规划问题转化为腿的足端轨迹规划问题,从而使步行机器人运动控制问题得到大大简化.并应用该方法对全方位三角步态算法及稳定性进行分析求解.     

PUMA机器人逆运动模拟退火粒子群求解方法

机器人逆运动问题随着运动关节的增多而越来越复杂,要建立逆运动通用的解析算法相当困难。提出利用模拟退火粒子群优化算法在解空间的搜索能力,直接从正向运动方程出发求解机器人关节变量的方法,讨论了目标函数的建立方式及算法实现步骤。实验分析该方法在位置和姿态方面的求解精度,并证实了算法的有效性。     

沟壑类非连续地形下的四足机器人运动控制

针对四足机器人踏入野外沟攀或踏上非结构化下行台阶时出现的姿态失稳问题,提出模仿生物神经反射机理的抗垂直惯性力平衡控制方法,即通过检测躯干的俯仰角突变信息,触发姿态反射,通过四条腿协调运动快速调整机器人姿态,抵抗惯性力造成的瞬时失稳.本文利用一个8自由度的四足仿生机器人设计了对比实验:机器人可成功跨越1.2倍跨距的沟壑并...     

Real-time obstacle detection for legged robots using the Kinect sensor

Autonomous navigation of legged robots in complex environments poses a great deal of challenges compared with ground vehicles because of their different terrain traverse capabilities. An obstacle for vehicles may be traversable for legged robots. This paper proposes a real-time obstacle detection algorithm for legged robots using the Microsoft Kinect sensor. First, the elevation map of a reference grid is calculated. Then an obstacle definition for legged robots is proposed, which makes it possible for a legged robot to discriminate traversable areas from non-traversable areas. To reduce computational cost, sometimes, efficient judging rules are developed to identify obstacles. A spiral search strategy is proposed to find the most ground-like point as the starting point for graph-based traversal. Breadth-First-Traversal of the graph is used to label all traversable areas connecting to the starting point. Experimental results demonstrate that our algorithm is reliable and efficient. The proposed algorithm can be employed in real-time obstacle detection for legged robots in complex environments.     

Optimization and evaluation of swing leg retraction for a hydraulic biped robot

To improve the locomotion performance of legged robots, the swing leg retraction (SLR) technique is investigated in a hydraulic biped robot. First, the influence of SLR on the locomotion performance of the hydraulic biped robot is analyzed in theory and simulations based on an extended spring load inverted pendulum model. The influence contains three performance indicators: energy loss/effiency, friction/slipping, and impact/compliance. Second, by synthesizing three performance indicators, using unified objective method and particle swarm optimization algorithm, the optimal SLR rate for gait planning based on Bezier curve is addressed. Finally, experiments are implemented to validate the effectiveness and feasibility of proposed method. And, the results show that the SLR technique is useful to reduce the impact force, improve the robot's locomotion stability and make room for impedance performance improvement of compliance controller. This research provides an insight for locomotion control of hydraulic legged robots.     

一种多足步行机器人行走状态分析模型

结合步行机器人行走的动力学特性,通过对机器人的加速度传感器信息进行离散傅立叶变换,建立了行走相关特征值的概率模型.通过使用马氏距离作为判定标准,对步行机器人的行走稳定性给出定量描述.四足步行机器人平台上的实验结果表明,该模型能够实时反映机器人的行走特性,帮助机器人在行走状态受环境影响发生改变时,根据行走特征及时调整运动,保证其稳定性.     

Variable stiffness control of series elastic actuated biped locomotion

This study investigates the problem of dynamic walking impact on a biped robot. Two online variable stiffness control algorithms, i.e., torque balance algorithm (TBA) and surface fitting algorithm (SFA), are proposed based on virtual spring leg to achieve compliant performance. These two algorithms target on solving the high nonlinearity commonly existing in legged robot actuators. A planar biped robot experiment platform is designed for testing the proposed variable stiffness control. The experiments compare the performance of TBA and SFA and verify that applying the variable stiffness control of a virtual spring leg is capable of effectively absorbing unforeseen ground impacts and thus improving stability and safety of walking biped robots.     

Dynamically-Stable Motion Planning for Humanoid Robots

We present an approach to path planning for humanoid robots that computes dynamically-stable, collision-free trajectories from full-body posture goals. Given a geometric model of the environment and a statically-stable desired posture, we search the configuration space of the robot for a collision-free path that simultaneously satisfies dynamic balance constraints. We adapt existing randomized path planning techniques by imposing balance constraints on incremental search motions in order to maintain the overall dynamic stability of the final path. A dynamics filtering function that constrains the ZMP (zero moment point) trajectory is used as a post-processing step to transform statically-stable, collision-free paths into dynamically-stable, collision-free trajectories for the entire body. Although we have focused our experiments on biped robots with a humanoid shape, the method generally applies to any robot subject to balance constraints (legged or not). The algorithm is presented along with computed examples using both simulated and real humanoid robots.     

An investigation of climbing up stairs for an inchworm robot

In this research, an inchworm-type robot is being developed for the purpose of rescue missions. This robot has the ability to traverse obstacles such as stairs with fewer joints than legged robots. A self-standing inchworm robot, which has five links and four joints, is produced for trial purposes. In order for this robot to be able to climb up stairs, the kinematical analysis and the development of the program were investigated. As a result, the effectiveness of this robot is confirmed experimentally.     

Improving the Motion of Walking Machines by Autonomous Kinematic Calibration

Legged machines designed to walk on flat or irregular terrain do not need to possess great foot positioning accuracy in order to perform stable motion. However, the propulsion of the body—which normally follows a straight line—, requires feet to follow perfect straight lines—in the body's reference frame—, which must be parallel to each other; otherwise internal foot forces will arise. When this occurs, mainly due to mechanical imperfections and kinematic inaccuracies, foot slippage and changes in the attitude/altitude of the vehicle appear. In the case of legged robots that need to move on rigid structures to achieve stable locomotion, precise foot positioning is required to reduce the foot force interaction. Examples of such robots are legged robots that move by grasping structures or climbing robots that clasp their feet to a wall. Kinematic calibration is a traditional method of improving the accuracy of robot manipulators. These techniques, especially those based on kinematic closed chains, can also be applied to legged robots. This article introduces a method for calibrating legged machines autonomously. The theory has been developed to control a special four-legged robot, and for calibrating purposes each leg has been considered as a 2-DOF leg. Nevertheless, the theory can be easily extended to 3-DOF-leg machines as well as to six-legged machines. The method is of particular interest for industrial machines that walk on rigid structures so that the feet clasp firmly and cannot slip. The method is evaluated through simulation and tested in an industrial four-legged machine developed to walk in a double bottom cell of a ship's hull. Some experiments have been conducted using the calibrated kinematic model to validate the usefulness of the calibration method.     

Design and Development of the Lifting and Propulsion Mechanism for a Biologically Inspired Water Runner Robot

This paper describes the design and development of a novel robot, which attempts to emulate the basilisk lizard's ability to run on the surface of water. Previous studies of the lizards themselves have characterized their means of staying afloat. The design of a biomimetic robot utilizing similar principles is discussed, modeled, and prototyped. Functionally, the robot uses a pair of identical four bar mechanisms, with a 180 ^deg phase shift to achieve locomotion on the water's surface. Simulations for determining robot lift and power requirements are presented. Through simulation and experimentation, parameters are varied with the focus being a maximization of the ratio of lift to power. Four legged robots were more easily stabilized, and had a higher lift-to-power ratio than two legged robots. Decreases in characteristic length and running speed, and increases in foot diameter and foot penetration depth all cause a higher lift to power ratio. Experimental lift approached 80 gr, and experimental performance exceeded 12 gr/W for four legged robots with circular feet. This work opens the door for legged robots to become ambulatory over both land and water, and represents a first step toward robots which run on the water instead of floating or swimming.