小型双足步行机器人的步态规划

为了解决双足步行机器人的步态控制,实现机器人稳定步行.为加强机器人的行走稳定性和优化步态过程,通过构造机器人行走过程中应满足的约束条件,规划机器人行走时的基本姿态及重心轨迹.根据规划的行走姿态及轨迹建立运动学方程,求解方程得到机器人各关节的运动轨迹.通过Matlab软件进行对运动轨迹模型的仿真,仿真得到的结果与设想的结果一致,证明步行得到平滑的关节轨迹是平稳的,并验证了方法的可行性.     

双足机器人NAO爬楼步态规划

双足机器人的爬楼梯性能是衡量其在复杂环境下行走能力的一项重要指标.本文针对双足机器人NAO爬楼梯步态规划问题,提出一种离线步态规划方法：基于几何法建立机器人爬楼梯逆运动学模型;将运动解耦为前向运动和侧向运动,对于起步、中步和止步三个阶段,采用加速度空间法和几何约束规划法,计算各关节运动轨迹,并基于其逆运动学模型,得到各关节角序列;分别基于NAOSim和NAO进行虚拟样机仿真实验和实物样机验证.实验结果表明,步态规划方法合理有效.     

基于虚拟样机技术的四足机器人静态稳定步态规划

针对现有技术文献中广泛使用的多种静态稳定步态中速度稳定性与稳定裕度不可兼得的通病,在随动质心的静态步态基础上,利用参数化坐标变换矩阵方法规划出一种四足机器人前进过程中质心以曲线轨迹移动的静态步态方法,使该步态方法以连续性速度运动的过程中保证一定稳定裕度;通过D-H法求得四足机器人的逆运动学坐标变换矩阵,分别在三维空间中对四足机器人的四组足端轨迹方程进行规划,并带入MATLAB软件后以逆运动学方程计算出关节夹角驱动方程,利用步态规划图求出机器人四条腿各自对应的夹角驱动方程以及机体质心轨迹方程;最后在MSC.ADAMS软件中建立四足机器人虚拟样机并对规划的步态进行虚拟仿真,仿真结果验证了该步态对提升四足机器人对于速度连续性以及稳定裕度的提升。     

理疗师交互下的下肢康复训练机器人个性化步态规划方法

针对偏瘫患者的个体差异及病况差异,提出了一种理疗师交互下的下肢康复训练机器人步态规划方法,在理疗师-减重悬吊式康复训练机器人-患者三者共存的复杂环境中,理疗师穿戴主控外骨骼直接行走实现步态时空参数规划,并融入理疗师的医学经验及对患者的评估.首先,基于旋量理论建立运动学模型,实现理疗师空间与机器人空间的运动映射;然后,统一规划机器人关节运动轨迹、减重机构重心调整轨迹及跑步机步速.最后,通过理疗师步态参数的实时采集、运动映射实验及机器人轨迹跟踪实验,验证了步态时空规划方法的有效性.结果表明,髋、膝关节规划角度在人体关节活动范围内,速度变化平稳,关节轨迹规划和重心调整规划均符合人体行走的生理特性.理疗师的参与实现了渐进康复训练中的个性化步态规划.     

基于体感的仿人机器人步态学习与控制

针对现有理想化步态动力学模型规划方法复杂、人为指定参数过多、计算量大的问题,提出一种基于体感数据学习人体步态的仿人机器人步态生成方法。首先,用体感设备收集人体骨骼信息,基于最小二乘拟合方法建立人体关节局部坐标系;其次,搭建人体与机器人映射的运动学模型,根据两者间主要关节映射关系,生成机器人关节转角轨迹,实现机器人对人类行走姿态的学习;然后,基于零力矩点(ZMP)稳定性原则,对机器人脚踝关节转角采用梯度下降算法进行优化控制;最后,在步态稳定性分析上,提出使用安全系数来评价机器人行走稳定程度的方法。实验结果表明,步行过程中安全系数保持在0~0.85,期望为0.4825,ZMP接近于稳定区域中心,机器人实现了仿人姿态的稳定行走,证明了该方法的有效性。     

基于遗传算法的四足机器人行走步态规划

因RoboCup四腿组比赛所采用机器人的关节刚度较低，采用固定形状行走轨迹的步态规划方法所产生的实际步态和规划步态偏差较大。这种偏差限制了机器人行走速度的提高。为了提高机器人的行走速度，在原有步态规划方法的基础上，引入200组坐标描述任意形状的机器人行走轨迹，并用改进的遗传算法寻找最适合机器人行走的轨迹形状。实验结果表明：改进的行走轨迹规划方法经学习后的实际步态更有利于机器人的行走，在行走更加平稳的同时可使机器人获得更快速的行走效果。     

一种改进的机器人在线全身关节补偿

基于三维线性倒立摆模型和ZMP生成了双足机器人的步行模式;在实际的行走过程中,机器人实际的步态轨迹和期望的步态轨迹之间存在一定的误差;为了机器人稳定地行走,必须对机器人的步行模式进行在线修正;提出了一种基于爬山算法的机器人在线全身关节补偿;通过对机器人各关节的补偿,修正机器人的质心偏差,从而达到机器人步行模式的在线修正;最后,通过计算机仿真和实体机器人验证了改方案的可行性。     

基于实时ZMP检测的类人足球机器人步态规划

为了保证类人机器人行走的稳定性,合理的步态规划和误差补偿是最为关键的两个方面。针对研究新一代的类人足球机器人AFU2008,在步态规划方面,根据ZMP(零力矩点)稳定性原理,首先用参考轨迹法进行关节轨迹规划,然后由运动学逆解出的关节转角值对机器人舵机进行实际控制;在误差补偿方面,采用对ZMP影响较大的上体运动进行误差补偿,并针对传统的上体补偿方法的局限性,提出了允许上体高度作匀速运动的改进方法。最后通过仿真和实际实验表明:相对于传统补偿方法,新方法能够更加明显减小机器人的ZMP误差,提高机器人ZMP的稳定裕度,使得类人机器人可以稳定快速的行走。     

基于ADAMS的双足机器人拟人行走动态仿真

在双足机器人HEUBR_1的设计中,下肢采用了一种新的串并混联的仿人结构,并在足部增加了足趾关节.为验证该仿人结构设计的合理性及拟人步态规划的可行性,在ADAMS虚拟环境中建立了双足机器人HEUSR_1的仿真模型.通过拟人步态规划生成了运动仿真数据,在ADAMS虚拟环境中实现了具有足趾运动的拟人稳定行走,经仿真分析,获得了双足机器人HEUBR_1拟人行走步态下的运动学和动力学特性,仿真结果表明:双足机器人HEUBR_1的串并混联的仿人结构设计能够满足行走要求,且拟人步态规划方法可行,有足趾运动的拟人行走具有运动平稳、能耗低、足底冲击力小的特点.稳定行走的仿真步态数据可为下一步双足机器人HEUBR_1样机行走实验提供参考数据.     

基于ZMP的仿人机器人跑步运动模式

采用小车-曲面桌子模型,提出了一种基于零力矩点(zero moment point,ZMP)的仿人机器人跑步运动模式.在单腿支撑阶段和飞行阶段,分别规划了仿人机器人的质心运动轨迹和双脚运动轨迹.在单腿支撑阶段,求解根据小车-曲面桌子模型建立的动力学方程,依据小车的运动轨迹规划出仿人机器人的质心轨迹;在飞行阶段,仿人机器人质心可看作抛物线运动,质心轨迹可通过水平方向上的匀速运动和竖直方向上的自由落体运动轨迹表示.分析了双脚与地面接触时的力及力矩约束.通过改变ZMP调整身体的倾斜角度,保持身体动态平衡.同时根据动力学方程分别求解出踝关节及其他关节的关节力矩.仿真实验结果表明:仿人机器人跑步时各关节角度和关节驱动力矩变化稳定,能够实现稳定的跑步,验证了方法的有效性.     

Kinematic Constraints on Fault-Tolerant Gaits for a Locked Joint Failure

Fault-tolerant gaits in legged locomotion are defined as gaits with which legged robots can continue their walking after a failure event has occurred to a leg of the robot. For planning an efficient fault-tolerant gait, kinematic constraints and remaining mobility of the failed leg should be closely examined with each other. This paper addresses the problem of kinematic constraints on fault-tolerant gaits. The considered failure is a locked joint failure which prevents a joint of a leg from moving and makes it locked in a known place. It is shown that for the existence of the conventional fault-tolerant gait for forward walking on even terrain, the configuration of the failed leg must be within a range of kinematic constraints. Then, for coping with failure situations where the existence condition is not satisfied, the conventional fault-tolerant gait is adopted by including the adjustment of the foot trajectory of the failed leg. The foot trajectory adjustment procedure is analytically derived to show that it can help the fault-tolerant gait avoid dead-lock resulting from the kinematic constraint. To demonstrate its effectiveness, the proposed method is applied to the fault-tolerant gait generation for a quadruped robot walking with the wave-crab gait before a locked joint failure.     

How to optimize the slope walking motion by the quadruped walking robot

Reduction of the energy consumption is one of the most important problems to utilize quadruped walking robots for various works on rugged terrain. The authors have studied basic strategy to achieve high energy efficiency when the quadruped walking robot do the motion essentially requires positive power by the analysis of body rising motion. This paper discusses the energy efficiency of the slope walking motion by the quadruped walking robot. First, we investigate the walking posture in consideration of ideal actuator characteristics where the robot consumes few negative powers at each joint which causes the main energy loss of the walking robot. Then, we investigate optimal walking posture in consideration of DC motor characteristics by the full search of three gait parameters which define the crawl gait. Furthermore, we derive the optimal walking motion by the optimization of three gait parameters which are kept constant during one cycle gait and instantaneous parameters such as body velocity and supporting forces changed at each moment simultaneously.     

Two walking gaits for a planar bipedal robot equipped with a four-bar mechanism for the knee joint

The design of a knee joint is a key issue in robotics and biomechanics to improve the compatibility between prosthesis and human movements, and to improve the bipedal robot performances. We propose a novel design for the knee joint of a planar bipedal robot, based on a four-bar linkage. The dynamic model of the planar bipedal robot is calculated. Two kinds of cyclic walking gaits are considered. The first gait is composed of successive single support phases with stance flat-foot on the ground separated by impacts. The second gait is a succession of finite time double support phases, single support phases, and impacts. During the double support phase, both feet rotate. This phase is ended by an impact of the toe of the forward foot, while the rear foot is taking off. The single support phase is ended by an impact of the swing foot heel, the other foot keeping contact with the ground through its toe. For both gaits, the reference trajectories of the rotational joints are prescribed by cubic spline functions in time. A parametric optimization problem is presented for the determination of the parameters corresponding to the optimal cyclic walking gaits. The main contribution of this paper is the design of a dynamical stable walking gait with double support phases with feet rotation, impacts, and single support phases for this bipedal robot.     

双足机器人动态步态规划

针对目前仿人机器人动态步行在样机上实现较少的情况,将多项式插值方法运用于机器人踝关节轨迹规划,结合已知髋关节运动轨迹,利用几何约束的方法求取膝关节运动轨迹,得到完整步态周期内各关节运动规律,最终实现NAO机器人的动态步行。实验结果证实了基于多项式插值的几何约束规划方法是可行且有效的。     

基于图像处理的人体步态信息采集与处理

为了获取健康人体的正常步态信息, 提出了一种快捷有效的获取方法. 通过在下肢关节点处粘贴标记点, 利用摄像机获取正常人行走的图像, 对图像进行二值化处理, 提取出标记点坐标. 经过最小二乘拟合分析可得到人体脚心在一个步态周期内的运动轨迹及运动速度. 最后对下肢康复机器人进行步态规划, 得到下肢康复机器人的步态轨迹及其速度,并对不同年龄人群的步态速度曲线进行了分析. 实验结果表明, 该系统可行性好, 工作稳定, 为下肢康复机器人的运动学分析与控制提供有力的理论依据和验证方法.     

Demonstration and Analysis of Quadrupedal Passive Dynamic Walking

Animals, including human beings, can travel in a variety of environments adaptively. Legged locomotion makes this possible. However, legged locomotion is temporarily unstable and finding out the principle of walking is an important matter for optimum locomotion strategy or engineering applications. As one of the challenges, passive dynamic walking has been studied on this. Passive dynamic walking is a walking phenomenon in which a biped walking robot with no actuator walks down a gentle slope. The gait is very smooth (like a human) and much research has been conducted on this. Passive dynamic walking is mainly about bipedalism. Considering that there are more quadruped animals than bipeds and a four-legged robot is easier to control than a two-legged robot, quadrupedal passive dynamic walking must exist. Based on the above, we studied saggital plane quadrupedal passive dynamic walking simulation. However, it was not enough to attribute the result to the existence of quadrupedal passive dynamic walking. In this research, quadrupedal passive dynamic walking is experimentally demonstrated by the four-legged walking robot 'Quartet 4'. Furthermore, changing the type of body joint, slope angle, leg length and variety of gaits (characteristics in four-legged animals) was observed passively. Experimental data could not have enough walking time and could not change parameters continuously. Then, each gait was analyzed quantitatively by the experiment and three-dimensional simulation.     

Level-ground walking for a bipedal robot with a torso via hip series elastic actuators and its gait bifurcation control

Recent studies have shown that a bipedal robot with a torso supported by springs on the hip can have a stable passive gait on a slope, while such a robot walking on level ground is a new challenge and has rarely been studied. This research adds actuators in series with the springs to form series elastic actuators on the hip and applies a state machine as controller to achieve stable walking on level ground. During walking, hip series elastic actuators support the torso from the legs as well as complement the energy to the system via elastic potential energy. The state machine uses the landing impact of the swing leg and the actuation durations as events to make the robot switch between successive active and passive walking processes. Because this simple scheme makes full use of the dynamics of the robot, it can lead to an efficient and natural gait. By means of numerical simulation, in addition to the stable period-1 gait, we found a variety of gait bifurcation phenomena, including the period-doubling bifurcation, the Neimark–Sacker bifurcation, the Neimark–Sacker-2 bifurcation, the period-X bifurcation, and the Neimark–Sacker-X bifurcation, among which many types have never been reported in previous studies. We also show that the unstable period-1 gait embedded in the bifurcation gait can be stabilized by applying the Ott–Grebogi–Yorke method. Not only can the gait bifurcation be suppressed, but also higher gait performance can be achieved.     

Translational Crawl and Path Tracking of a Quadruped Robot

Translational crawl and path tracking are presented for a quadruped robot, named TITAN‐VIII, to walk on rough ground. The generalized and explicit formulation is derived to generate the translational crawl gait in an arbitrary direction automatically, to control the joint positions, and to estimate the robot localization in a walking environment. Compared to conventional gaits, the proposed gait is characterized by a natural and continuous transition between any successive gait cycles, by a maximized stride of the robot in each gait cycle, and by different foot trajectories corresponding to the uneven terrain. Especially, the proposed approach enables the quadruped robot to track a reference path in a complex walking environment, based on dead‐reckoning localization for the robot. The effectiveness of the proposed method is demonstrated through the experimental results. © 2002 Wiley Periodicals, Inc.