四足机器人步态生成算法研究与仿真

在四足机器人行走动态控制的研究中,为使四足机器人能在复杂地面状况下行走,提出了一种四足机器人在不平坦地面爬行时的平动步态生成算法.首先构建四足机器人步行机构模型,根据静态稳定性对角线原理的判定确定机器人腿的摆动顺序;以平动步态为例根据机器人前行方向、初始位姿、地面不平坦等因素计算一个步态周期后机器人的位姿从而实现平动直线行走的连续步态算法.考虑了机器人机构约束以及状态变化因素使机器人在每一个步态周期都能跨出尽可能大的步幅实现行走效率的最大化.通过仿真验证了算法的正确性.仿真结果对四足机器人步态稳定性的研究及实现具有实际的参考价值.     

二足机器人之动态平衡研究

主要探讨二足机器人（biped robots）行走或受到外力干扰时,通过动态平衡控制使机器人行走更趋稳定,并增强站立时稳定性．二足机器人动态平衡之实现,主要是将动态平衡控制程序撰写于Nios Ⅱ发展环境中,当二足机器人行走时,利用脚底压力传感器取得压力值,运算及判断二足机器人实际重心是否落在二足机器人支撑多边形范嗣内,并计算实际重心与期望重心之误差,以模糊控制器将二足机器人重心控制于支撑多边形范围内,使二足机器人行走时能够更加稳定,实验结果表明该方法是有效的．     

便携式神经肌肉功能性电刺激系统设计

本项目应用于肢体瘫痪或功能衰退的人群,电刺激器通过小电流刺激患者肢体引起肌肉收缩,从而使肢体产生动作。系统以STM32F407单片机为主控芯片,产生脉宽、频率可调的单相波形,经过光耦多路开关组合成双相波形,然后进行波形放大,且幅值可调,再经过电极刺激肢体,使肢体产生预先设定的相应动作。系统以6节干电池供电,器件选用小功率贴片元件,通过升压电源负载功率验证了系统各模块能稳定工作,从而实现一种功耗低、体积小、便携式的刺激器。     

步态分析及在功能性电刺激系统中的应用

文中提出一种足下垂功能性电刺激实时控制算法—基于自适应阈值的足下垂FES启停控制算法:将患者的小腿角速度信号和步态过程结合分析,在每一个步态周期内实时识别脚尖离地和脚跟着地2个关键时刻点。在脚尖离地时对患者患肢胫骨前肌施加电刺激,输出基于阈值和耐受值的梯形波,在脚跟着地时停止电刺激。实验验证了算法的可行性,通过分析步态的角速度信息和设计的启停控制模式可以辅助患者行走,在一定程度上帮助患者改善步态。     

基于PIC单片机的六足机器人制作

基于仿生原理，以PIC单片机为控制器的核心，制作出了动作灵活、价格低廉以及模块化结构的六足机器人。该机器人能够严格按三角步态进行行走，实现诸如直线、转弯、躲避障碍物和追踪物体等行走功能。文中介绍了该机器人三角步态的行走原理、结构组成、控制系统和控制算法。     

步行机器人的步态选择与静态平衡

本文的研究范围包括步行机器人的步态选择和四足步行机的静态行走平衡,首先,根据“有限状态理论”,引入了一个关于步态的新定义,在此基础上,研究了步态的选择准则,两个基本特性及其综合方法.最后.导出了使四足步行机保持静态稳定行走的充分和必要条件.     

虚拟人行走的动作融合

研究在行走时虚拟人动作与虚拟地形之间的交互性。通过碰撞检测来确定人体在地面之上的正确位置。利用动作融合的方法,即将几个典型动作按合适的权重结合产生新的动作数据,实时地驱动虚拟人并使之对环境变化的反应满足视觉上的逼真性。融合过程中各原始动作的权重取决于沿着和垂直于人体运动方向的2个地面坡度,同时也通过对地形的几何分析来实现虚拟人对其周边地形的感知。     

两栖多足机器人水下步态分析

通过对两栖动物运动机理的研究,针对两栖多足机器人水下行走的特点,采用减轻重力、附加流 体力的方法,提出了静水环境下的动力学模型,并基于对模型的分析提出了适用于两栖多足机器人水下运动 的“蹬踏—漂浮”步态．该步态不但解决了两栖多足机器人以陆地行走步态在水下行走时出现的抓地不牢及 稳定性不够的问题,而且提高了水下步行速度．通过分析两栖多足机器人的水下实验结果,验证了步态的可 行性．     

四足机器人躯干重心稳定的变步长行走研究

在机器人稳定性控制优化问题的研究中,四足机器人行走过程中躯干重心位置的波动是运动不平稳的一个重要原因,也会带来机器人的低能效比和机械寿命缩短等问题.为了解决上述问题,研究了四足机器人行走过程中保持重心稳定的方法,提出重心无波动关节运动规划方法.从静止加速到指定速度的过程,速度的增加按S型曲线变化,保证重心的平稳加速;在恒速行走过程中,以躯干重心位置变化的加速度为零、足端在起脚和落脚位置的冲击为零作为约束条件,计算出四足机器人各关节的运动函数,保证了行走过程的重心平稳.机器人行走的步长在行走过程中动态计算,计算依据是保证整个行走过程中重心在水平面的投影始终在机器人支撑脚所在多边形范围之内,可进一步减小重心在垂向的波动.对所提方法进行了计算机仿真,运动规划及关节驱动函数在Matlab中实时解算,运动过程的程序控制采用Matlab的状态机技术,四足机器人行走的动力学过程用Adams实时计算.仿真过程中四足机器人行走平稳,实际重心曲线在横向和垂向的偏移波动极小,表明提方法对于重心的控制是有效的,为机器人稳定行走设计提供了依据.     

六足步行机器人控制系统研究

六足机器人是一种具有多支链与时变拓扑结构的特种机器人,该类机器人能够在复杂环境中稳定行走,长期以来一直是国内外机器人研究领域的热点之一。本文从仿生角度出发,归纳六足机器人稳定行走的三种方式;根据六足机器人各足支撑点围成的多边形区域与机体重心在其投影的关系来评定六足机器人行走稳定性,为实现六足机器人稳定性行走提供理论依据;最后根据机器人控制精度增加和智能力减少的原则,以分级递阶的方式设计六足机器人的运动控制系统。     

Iterative learning control of a drop foot neuroprosthesis — Generating physiological foot motion in paretic gait by automatic feedback control

Many stroke patients suffer from the drop foot syndrome, which is characterized by a limited ability to lift the foot and leads to a pathological gait. We consider treatment of this syndrome via Functional Electrical Stimulation (FES) of the peroneal nerve during the swing phase of the paretic foot. We highlight the role of feedback control for addressing the challenges that result from the large individuality and time-variance of muscle response dynamics. Unlike many previous approaches, we do not reduce the control problem to the scalar case. Instead, the entire pitch angle trajectory of the paretic foot is measured by means of a 6D Inertial Measurement Unit (IMU) and controlled by an Iterative Learning Control (ILC) scheme for variable-pass-length systems. While previously suggested controllers were often validated for the strongly simplified case of sitting or lying subjects, we demonstrate the effectiveness of the proposed approach in experimental trials with walking drop foot patients. Our results reveal that conventional trapezoidal stimulation intensity profiles may produce a safe foot lift, but often at the cost of too high intensities and an unphysiological foot pitch motion. Starting from such conservative intensity profiles, the proposed learning controller automatically achieves a desired foot motion within one or two strides and keeps adjusting the stimulation to compensate time-variant muscle dynamics and disturbances.     

一种基于多传感器的步态相位实时检测系统

对人体步态相位进行准确实时的判断是智能假肢等康复机器人控制的基础,提出并建立了一种实时状态相位检测系统.该系统包含了4只压力传感器和2只姿态传感器,能够准确地区分出平地行走时足跟着地、足放平、足跟离地、足尖离地、摆动弯曲以及摆动伸展等五种状态相位,实验表明:该系统能够适应不同测试者的不同步幅和步速,并能够应用在假肢的实时控制中.     

基于行走时脚摆角的步态识别方法

提出一种利用脚摆动特征进行步态识别的方法。对步态序列图像进行背景提取、图像差分、阈值分割、形态学后处理后,提取行走时的脚摆角作为特征参数,再分别采用BP神经网络、最近邻分类器和K近邻分类器法对这些特征数据进行识别分类与比较分析。实验结果表明,与同类方法相比,该方法可以更快速地进行步态识别,且识别性能较好。     

A Highly Backdrivable, Lightweight Knee Actuator for Investigating Gait in Stroke

Many of those who survive a stroke develop a gait disability known as stiff-knee gait (SKG). Characterized by reduced knee flexion angle during swing, people with SKG walk with poor energy efficiency and asymmetry due to the compensatory mechanisms required to clear the foot. Previous modeling studies have shown that knee flexion activity directly before the foot leaves the ground, and this should result in improved knee flexion angle during swing. The goal of this research is to physically test this hypothesis using robotic intervention. We developed a device that is capable of assisting knee flexion torque before swing but feels imperceptible (transparent) for the rest of the gait cycle. This device uses sheathed Bowden cable to control the deflection of a compliant torsional spring in a configuration known as a Series Elastic Remote Knee Actuator (SERKA). In this investigation, we describe the design and evaluation of SERKA, which includes a pilot experiment on stroke subjects. SERKA could supply a substantial torque (12 N $cdot$ m) in less than 20 ms, with a maximum torque of 41 N $cdot$ m. The device resisted knee flexion imperceptibly when desired, at less than 1 N $cdot$ m rms torque during normal gait. With the remote location of the actuator, the user experiences a mass of only 1.2 kg on the knee. We found that the device was capable of increasing both peak knee flexion angle and velocity during gait in stroke subjects. Thus, the SERKA is a valid experimental device that selectively alters knee kinetics and kinematics in gait after stroke.      

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.     

基于主支撑腿运动优化的仿人机器人快速步态规划算法

提出一种基于主支撑腿运动优化的快速步态规划算法,利用快速动态步行的特点,规划ZMP(Zero Moment Point)适时地离开质心投影并始终停留在稳定的支撑区域内．规划过程中考虑了仿人机器人摆动足触地时的碰撞,整个步态产生于深度的优化过程．     

Swing-Leg Retraction for Limit Cycle Walkers Improves Disturbance Rejection

Limit cycle walkers are bipeds that exhibit a stable cyclic gait without requiring local controllability at all times during gait. A well-known example of limit cycle walking is McGeer's ldquopassive dynamic walking,rdquo but the concept expands to actuated bipeds as involved in this study. One of the stabilizing effects in limit cycle walkers is the dissipation of energy that occurs when the swing foot hits the ground. We hypothesize that this effect can be enhanced with a negative relation between the step length and step time. This relation is implemented through an open-loop strategy called swing-leg retraction; a predefined time trajectory for the swing leg makes the swing leg move backwards just prior to foot impact. In this paper, we study the effect of swing-leg retraction through three bipeds; a simple point mass simulation model, a realistic simulation model, and a physical prototype. Their stability is analyzed using Floquet multipliers, followed by an evaluation of how well disturbances are handled using the Gait Sensitivity Norm. We find that mild swing-leg retraction is optimal for the disturbance rejection of a limit cycle walker, as it results in a system response that is close to critically damped, rejecting the disturbance in the fewest steps. Slower retraction results in an overdamped response, characterized by a positive dominant Floquet multiplier. Likewise, faster retraction results in an underdamped response, characterized by a negative Floquet multiplier.     

Generation of a continuous free gait for quadruped robot over rough terrains

Generating a robust gait is one of the most important factors to improve the adaptability of quadruped robots on rough terrains. This paper presents a new continuous free gait generation method for quadruped robots capable of walking on the rough terrain characterized by the uneven ground and forbidden areas. When walking with the proposed gait, the robot can effectively maintain its stability by using the Center of Gravity (COG) trajectory planning method. After analyzing the point cloud of rough terrain, the forbidden areas of the terrain can be obtained. Based on this analysis, an optimal foothold search strategy is presented to help quadruped robot to determine the optimum foothold for the swing foot automatically. In addition, the foot sequence determining method is proposed to improve the performance of robot. With the free gait proposed in this paper, quadruped robot can walk through the rough terrains automatically and successfully. The correctness and effectiveness of the proposed method is verified via simulations.     

Walking and steering control for a 3D biped robot considering ground contact and stability

This paper presents a stable walking control method for a 3D bipedal robot with 14 joint actuators. The overall control law consists of a ZMP (zero moment point) controller, a swing ankle rotation controller and a partial joint angles controller. The ZMP controller guarantees that the stance foot remains in flat contact with the ground. The swing ankle rotation controller ensures a flat foot impact at the end of the swinging phase. Each of these controllers creates 2 constraints on joint accelerations. As a consequence, the partial joint angles controller is implemented to track only 10 independent outputs. These outputs are defined as a linear combination of the 14 joint angles. The most important question addressed in this paper is how this linear combination can be defined in order to ensure walking stability. The stability of the walking gait under closed loop control is evaluated with the linearization of the restricted Poincare map of the hybrid zero dynamics. As a result, the robot can achieve an asymptotically stable and periodic walking along a straight line. Finally, another feedback controller is supplemented to adjust the walking direction of the robot and some examples of the robot steered to walk along different paths with mild curvature are given.