欠驱动两足步行机器人研究现状

针对欠驱动两足步行机器人的研究现状与发展趋势进行了探讨。首先,总结了被动行走和踝关节欠驱动两足机器人的研究现状,介绍了欠驱动两足步行机器人的基本研究方法,包括问题描述、步态规划、运动控制和稳定性判定等,并对欠驱动两足机器人需要进一步研究的问题和发展方向进行深入研究,最终目标是将欠驱动控制策略应用于两足步行机器人的行走过程控制,以提高其运动性能。     

双足被动步行的全局稳定性分析

在经典双足被动步行动力学模型的基础上,分析环境和力学参数影响下机器人被动步行的全局稳定性。计算不同模型参数下被动步行稳定不动点,采用胞胞映射计算得到不同模型参数下该动力学模型稳定单周期步态的吸引区域。研究发现双足被动步行的鲁棒性与其环境、力学参数关系密切,同时提出估计不动点吸引域形状的2个度量：最小半径与最大半径。实验结果给出被动步行稳定区域与斜坡倾角和质量比值的关系,同时通过分析某些偏离不动点较大的稳定吸引胞,以及吸引域的最小半径与最大半径的变化趋势,反映了双足被动步态的鲁棒性。     

半被动双足机器人的准开环控制

目前的被动行走机器人还只能完成单一的步态,且非常容易摔倒,为此对半被动双足机器人的稳定行走控制问题进行了研究．通过结合被动行走和主动控制两种原理的优点,提出了一种准开环的行走控制方法．通过检测安装在机器人足底和髌骨处的接触开关信号,在髋关节处施加一个间断的、微小的开环振荡力矩,进而实现高效的稳定步行．仿真结果表明,当控制参数在较大范围内变化时,双足机器人仍可实现稳定行走,且步行能耗特性与人类相似;通过调节振荡力矩的参数,机器人可实现稳定的行走模式转换．     

仿人机器人动态步行控制综述

综述了仿人机器人动态步行的研究历史和研究现状。归纳了动态步行的特点,分析了动态步行稳定性判定方法,介绍了基于ZMP的姿态稳定判据和基于庞加莱映射（Poincaré Map）的步态稳定判据。总结了仿人机器人学习适应复杂地面环境步行的方法,概述了动态步行控制实现的典型解决方案,指出了动态步行控制中待解决的问题,并探讨了未来的发展方向。     

双足步行机器人转弯步态规划及其实现

针对双足步行机器人的转弯步态规划及其实现问题进行了研究.首先介绍了双足步行机器人转弯步态规划方法和所涉及的关键问题,包括关键点轨迹插值和逆运动学解算,然后给出了实现双足步行机器人转弯步态规划的具体步骤,最后通过对实验室新研制的双足步行机器人转弯运动进行仿真和实验研究,证实了本文所提出的几何约束加修正补偿的双足步行机器人转弯步态规划方法的有效性和可行性.     

全方位六足步行机器人分析——腿机构、运动学、静力学分析、步态规划与步行软件

本文对全方位六足步行机器人步行中所涉及的步态规划、步行算法及步行软件,稳定性分析、能耗分析等问题进行了深入地研究.首先依据相对运动学原理建立全方位六足步行机器人的运动学。并对其工作空间进行了详细地分析,接着讨论了步行机器人的单腿静力学分析及多腿触地情况下足端力的分力求解问题.把 M-P 广义逆与求解超静定力问题的解法相结合,对足端力的分布特性及求解方法进行了研究.     

基于深度强化学习的双足机器人斜坡步态控制方法

为提高准被动双足机器人斜坡步行稳定性,本文提出了一种基于深度强化学习的准被动双足机器人步态控制方法.通过分析准被动双足机器人的混合动力学模型与稳定行走过程,建立了状态空间、动作空间、episode过程与奖励函数.在利用基于DDPG改进的Ape-X DPG算法持续学习后,准被动双足机器人能在较大斜坡范围内实现稳定行走.仿...     

仿人型机器人动态步行控制方法

本文介绍了仿人型机器人动态步行的一些基本问题和相关概念．从信息和控制的 角度对近年来仿人型机器人动态步行研究中出现的步态规划和姿态控制方法进行了分析,并 指出了它们的特点．提出了先进仿人型机器人实现过程中值得进一步研究的问题．     

基于BP神经网络的被动步行稳定不动点的估算

建立了被动步行机器人的动力学模型．使用BP 神经网络对被动步行稳定不动点进行估算,并将估算值 作为Newton-Raphson 迭代的初值来求解稳定不动点．该方法解决了以往利用非最简模型求解不动点时,由于初值 选取不当所造成的搜索成功率低以及搜索时间长的问题．在获取训练样本时,参数变化较小时不动点的变化很小; 利用这一特点,在计算相邻两个样本的不动点时,只使一个参数发生较小的变化,并将本次使用Newton-Raphson 迭 代搜索得到的稳定不动点作为搜索下一样本不动点时的初值．使用1 000 组随机产生的参数对所得神经网络进行测 试,结果表明该方法可以大幅提高稳定不动点的搜索成功率,大幅缩短搜索时间．     

机器人动态步行控制技术

本文讨论了步行机器人中最复杂和棘手的动态步行控制问题,详述了现有的动态步行控制技术及其现状,分析和比较了各类控制方法的利弊和存在的问题,提出了今后的努力方向.     

Energy-Optimal Design of Walking Machines

In a general definition of robot components given by Wolfram Stadler, communications and power supply are included showing the close relation between robots and walking machines. Both of them are based on mechatronics allowing variable programmable operations.Biped walking represents a complex motion of sophisticated systems in nature as well as in engineering. A young human requires more than 1 year to learn walking while old humans need additional devices for save walking. While passive machines walk only on inclined planes, active machines may walk in all kinds of terrains. However, the active devices known from literature consume so much energy that their operation time is very restricted.In this paper the modeling of walking systems using the method of multibody dynamics is presented including the contact and impact problem inherent to biped walking. The limit cycle of passive motions is investigated as well as the related stability using shooting approaches with optimization techniques. The active machines proposed are controlled using the principles of inverse dynamics and advanced linear control strategies. In particular, the energy consumption between passive and active walking machines is compared by a coefficient of efficiency. At the time being human walking is still the most efficient and it is considered as a benchmark for the mechatronic design of walking machines.     

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.     

Passive dynamic turning in 3D biped locomotion: an extension to passive dynamic walking

Passive dynamic walking usually refers to a kind of walking where a biped walker is able to walk downhill, without any actuation or control, just due to the gravity. Although most of works done in this regard have concentrated on passive walking along a straight line, in this paper we extend this concept to a more general case of locomotion, i.e. turning or walking along curved path. We call the novel extension passive turning, and categorize it to two types of finite and infinite. We showed that the finite type is still applicable on a typical downhill or ramp, while the infinite type is only practical on a specific surface profile that we call it helical ramp. Furthermore, several stability and parameter analysis are also conducted to evaluate more aspects of this notion. We highlighted that surprisingly, the passive straight walking is actually a special case of passive turning, just with infinite radius of turn and less asymptotical stability. It should be noted that the present study is performed using a model of an arc-foot three-dimensional (3D) compass gait walker.     

Simulation verification for the robustness of passive compass gait with a joint stiffness adjustment

A passive walking robot can achieve a smooth gait without any sensory feedback while walking down a slope. This phenomenon is based on the transformation of potential energy into kinetic energy in the legs. Although the entrainment is observed in a passive gait motion, there is a possibility that the passive gait cannot be achieved in the case of variations in physical parameters, initial conditions, and disturbances. To realize a robust passive gait against variations in physical parameters, this paper proposes a passive gait system that possesses a joint stiffness adjustment. Targeting a compass model, this paper investigates the effectiveness of the proposed method for a passive gait against variations in slope angle and hip joint mass through simulation. As a result, the simulation results show that this method especially has strong robustness against the slope angle variation.     

Biped Gait Generation and Control Based on a Unified Property of Passive Dynamic Walking

Principal mechanisms of passive dynamic walking are studied from the mechanical energy point of view, and novel gait generation and control methods based on passive dynamic walking are proposed. First, a unified property of passive dynamic walking is derived, which shows that the walking system's mechanical energy increases proportionally with respect to the position of the system's center of mass. This yields an interesting indeterminate equation that determines the relation between the system's control torques and its center of mass. By solving this indeterminate equation for the control torque, active dynamic walking on a level can then be realized. In addition, the applications to the robust energy referenced control are discussed. The effectiveness and control performances of the proposed methods have been investigated through numerical simulations.     

Adding an Upper Body to Passive Dynamic Walking Robots by Means of a Bisecting Hip Mechanism

Passive dynamic walking is a promising idea for the development of simple and efficient two-legged walking robots. One of the difficulties with this concept is the addition of a stable upper body; on the one hand, a passive swing leg motion must be possible, whereas on the other hand, the upper body (an inverted pendulum) must be stabilized via the stance leg. This paper presents a solution to the problem in the form of a bisecting hip mechanism. The mechanism is studied with a simulation model and a prototype based on the concept of passive dynamic walking. The successful walking results of the prototype show that the bisecting hip mechanism forms a powerful ingredient for stable, simple, and efficient bipeds     

Passivity-Based Control of Bipedal Locomotion

In this article, we have shown how to design energy-based and passivity-based control laws that exploit the existence of passive walking gaits to achieve walking on different ground slopes, to increase the size of the basin of attraction and robustness properties of stable limit cycles, and to regulate walking speed. Many of the results presented in this are the compass gait are equally applicable to bipeds with knees and a torso. Practical considerations such as actuator saturation, ground reaction forces, and ground friction need to be addressed. The problem of foot rotation introduces an underactuated phase into the walking gait, which greatly challenges the application of energy shaping ideas. For walking in 3D, finding purely passive limit cycles, which is the first step in applying our energy control results, may be difficult. It was shown how ideas of geometric reduction can be used to generate 3D stable gaits given only 2D passive limit cycles.     

Toward a human-like biped robot with compliant legs

Conventional models of bipedal walking generally assume rigid body structures, while elastic material properties seem to play an essential role in nature. On the basis of a novel theoretical model of bipedal walking, this paper investigates a model of biped robot which makes use of minimum control and elastic passive joints inspired from the structures of biological systems. The model is evaluated in simulation and a physical robotic platform by analyzing the kinematics and ground reaction force. The experimental results show that, with a proper leg design of passive dynamics and elasticity, an attractor state of human-like walking gait patterns can be achieved through extremely simple control without sensory feedback. The detailed analysis also explains how the dynamic human-like gait can contribute to adaptive biped walking.     

可侧向摆动的欠驱动双足机器人

为解决机器人的侧向平衡问题,同时为使机器人的行走空间由二维扩展到三维,确立了可以侧向周期稳定偏转的有弹性脚的欠驱动步行机器人模型。根据混合动力系统的特点,建立了侧向摆动方程及脚碰撞地面的方程,并利用数值仿真得到了不同初始状态下的稳定极限环。根据运动状态分析,找到了弹性脚的欠驱动步行机器人所允许的侧向偏转范围。施加基于能量的控制可以消除摆动过程中出现的干扰,使欠驱动步行机器人回归到稳定状态,稳定的侧向摆动保证了欠驱动步行机器人的稳定行走。     

Experimental studies on passive dynamic bipedal walking

Passive dynamic walking is a gait developed, partially or in whole, by the energy provided by gravity. The research on passive dynamic bipedal walking helps create an understanding of walking mechanics. Moreover, the experimental passive dynamic research provides a base to compare and validate computer simulation results. An improved kneed bipedal walking mechanism was designed and built to study the passive gait patterns. The first aim of this study is to determine the equivalency of testing a passive dynamic biped walker on a treadmill to testing on a ramp. Based on the small difference between the gait patterns measured on the two test platforms, testing on a treadmill was found equivalent to testing on a ramp. Gait measurements were then conducted on the treadmill to evaluate the effects of the treadmill inclination angle, mass distribution of the biped, and the length of flat feet on the gait pattern. Results show that most of these parameters had significant effects on the step length, step period and hip velocity of the passive walker. Our experimental results are also compared with previous experimental results.