六足步行机横向行走最佳步态及其运动特性初探

本文分别以纵向稳定裕量和一般稳定裕量为准则,通过对六足步行机横向行走几何模型的分析和计算机优化计算,得出六足步行机横向运动时的最佳步态为广义三角步态.此外,文中对广义三角步态的运动特性(包括静态稳定性、爬坡能力、越沟能力等)进行了初步研究,阐明了这些运动特性与步行机若干几何参数间的内在联系,为六足步行机的总体尺寸设计提供了理论依据。     

步行机器人的研究

1.首先介绍了步行机步态的定义及四足步行机的对称规则步态,在此基础上,对四足步行机稳定性问题进行了深入的研究,提出了基于能量考虑(计入运动速度影响)稳定性分析计算的能量法.2.详细讨论了运动主平面与垂直旋转轴具有偏距的圆柱型空间缩放式腿机构运动学,对四足步行机进行了与运动学控制有关的运动分析,给出了步行机运动速度与步态之间的关系,机体速度加速度与足端速度加     

六足步行机运动学及步行机构

六足步行机尚有许多问题需要解决.本学位论文对六足步行机的步态、步行机构以及足端轨迹规划等步行机基本间题展开了深入的研究,分析了步行的横向行走特性,得到了最佳稳定的横向步态,和纵向步态结合在一起,形成正交步态.将现有关单方向行走步态扩展到两个正交方向的行走步态,用分析的方法得出全方位步行机构应采用圆柱型空间缩放机构,并对步行机构作了运动学探讨.用级数方法对     

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.     

六足步行机横爬步态和运动干涉问题的研究

本文对六足步行机的两种横向爬行步态作了讨论,决出了在某一给定的静态稳定条件下.机体有效长度和绝对步幅之间的关系曲线。从工程角度出发,分析了步行机设计中应注意的运动干涉问题,并提出了这类问胚的解决方法。     

六足步行机跟导步态研究

本文给出了工程中实用的六足步行机器人跟导步态的实现条件，用能量法分析了这种步态的运动稳定性，给出了采用这种步态的六足行机的最大运动速度求解方法，分析了这种步态的越沟能力，并在ＳＧＩ工作站上对该步态的平地行走，跨沟及斜坡行走情形进行了仿真实验。     

六足步行机的转向问题探讨

本文用临界状态￣［１，２］方法对六足步行机的转向问题进行了研究，给出了六足步行机转向步态的拟定方法及其稳定裕度的计算方法。     

六足步行机的能量稳定性

本文详细讨论了六足步行机器人的能量稳定方法,给出并证明了六足步行机能量稳定裕量的一般计算公式,分析了横向及纵向行走的六足步行机采用三角步态时的能量稳定性,比较了能量稳定法和几何稳定法.     

六足步行机的稳定性研究

本文综合了各种地形条件下的六足步行机器人的静态稳定性方法,详细讨论了能量稳定法,证明了求解六足步行机能量稳定值分量的计算公式,并用能量稳定法分析了采用广义三角步态行走和横向运动六足步行机的爬坡能力、跨越障碍能力等越野性能,首次用数学表达式表述了机体     

4足步行机器人斜坡运动的研究

在4足步行机的运动环境中,上下坡是一种基本的典型环境.本文研究了缩放式4足步行机在上下坡环境中运动的一些基本规律,得出了上下坡时4足步行机在不同坡度下的最大步长,最佳机体高度.对4足步行机上下坡时能保持稳定运动的边界环境条件也进行了研究.     

Fault-Tolerant Gait Planning for a Hexapod Robot Walking over Rough Terrain

Multi-legged robots need fault-tolerant gaits if one of attached legs suffers from a failure and cannot have normal operation. Moreover, when the robots with a failed leg are walking over rough terrain, fault-tolerance should be combined with adaptive gait planning for successful locomotion. In this paper, a strategy of fault-tolerant gaits is proposed which enables a hexapod robot with a locked joint failure to traverse two-dimensional rough terrain. This strategy applies a Follow-The-Leader (FTL) gait in post-failure walking, having the advantages of both fault-tolerance and terrain adaptability. The proposed FTL gait can produce the maximum stride length for a given foot position of a failed leg and better ditch-crossing ability than the previous fault-tolerant gaits. The applicability of the proposed FTL gait is verified using computer graphics simulations.     

Energy-optimal gait analysis of quadruped robots

It is important for walking robots such as quadruped robots to have an efficient gait. Since animals and insects are the basic models for most walking robots, their walking patterns are good examples. In this study, the walking energy consumption of a quadruped robot is analyzed and compared with natural animal gaits. Genetic algorithms have been applied to obtain the energy-optimal gait when the quadruped robot is walking with a set velocity. In this method, an individual in a population represents the walking pattern of the quadruped robot. The gait (individual) which consumes the least energy is considered to be the best gait (individual) in this study. The energy-optimal gait is analyzed at several walking velocities, since the amount of walking energy consumption changes if the walking velocity of the robot is changed. The results of this study can be used to decide what type of gait should be generated for a quadruped robot as its walking velocity changes. This work was presented, in part, at the Sixth International Symposium on Artificial Life and Robotics, Tokyo, Japan, January 15–17, 2001.     

Dynamically balanced optimal gaits of a ditch-crossing biped robot

This paper deals with the generation of dynamically balanced gaits of a ditch-crossing biped robot having seven degrees of freedom (DOFs). Three different approaches, namely analytical, neural network (NN)-based and fuzzy logic (FL)-based, have been developed to solve the said problem. The former deals with the analytical modeling of the ditch-crossing gait of a biped robot, whereas the latter two approaches aim to maximize the dynamic balance margin of the robot and minimize the power consumption during locomotion, after satisfying a constraint stating that the changes of joint torques should lie within a pre-specified value to ensure its smooth walking. It is to be noted that the power consumption and dynamic balance of the robot are also dependent on the position of the masses on various links and the trajectory followed by the hip joint. A genetic algorithm (GA) is used to provide training off-line, to the NN-based and FL-based gait planners developed. Once optimized, the planners will be able to generate the optimal gaits on-line. Both the NN-based and FL-based gait planners are able to generate more balanced gaits and that, too, at the cost of lower power consumption compared to those yielded by the analytical approach. The NN-based and FL-based approaches are found to be more adaptive compared to the other approach in generating the gaits of the biped robot.     

Path tracking with quadruped walking machines using discontinuous gaits

Discontinuous gaits for walking machines offer great advantages over wave gaits, and they seem more adequate for following a path over irregular terrain. This paper, focused on quadruped walking robots, addresses the problem of following an arbitrary path using both discontinuous crab and turning gaits. First, the paper presents the algorithms to generate these gaits as local motions and highlights their advantages in comparison with continuous gaits. This comparison considers stability, velocity, power consumption and terrain adaptability. The algorithms for tracking an arbitrary trajectory using these gaits are then introduced, and some simulations and experimental results are reported.     

Stability analysis of wave-crab gaits of a quadruped

Crab walking is as important as forward walking as applied to walking machine control. Crab walking is especially important to a quadruped since a quadruped has a similar leg geometric layout in both longitudinal and lateral directions. In the studies of forward walking gaits, the wave gait was found to be the optimally stable. In this article, the wave gait is applied to the crab walking of a quadruped and it is modified into four types of wave-crab gaits according to the range of crab angle. The stability formulae of these wave-crab gaits are then derived analytically based on the following three stability measurements: stability margin (S_m), body-longitudinal (or lateral) stability margin (S_bl or S_bt) and crab longitudinal stability margin (S_cl). S_m is the true stability index under quasi-static walking condition. However, the equations are more complicated. S_bl (or S_bt) is simpler and can be used as a good approximation of S_m. S_cl was commonly adopted as the stability index in the previous gait studies. Nevertheless, S_cl is found to be misleading for a large portion of crab angle range. The analytical results derived in this paper are useful to the geometric design and to the real-time control of a quadruped.     

Integration of vision and walking skills together with high-level strategies for quadruped robots to play soccer

Legged robots taking part in real multi-agent activities represent a very innovative challenge. This domain of research requires developments in three main areas. First, without any feedback information from the environment, there is no way for robots to achieve some tasks autonomously. Fortunately, the quadruped 'Sony' prototypes on which all experiments are carried out are equipped with an enhanced vision system; thanks to its CCD camera located in its head, the robot can obtain color images of the scene around it. Extracting relevant information from the images captured is not easy since it must be done onboard in real time. Moreover, image treatment procedures should have high process rates for the robot to react quickly in front of unexpected events. A special vision module composed of three parts has been designed for these purposes. The second point to focus on is the walking ability of the robot. Quadrupeds are designed to move efficiently and rapidly on flat ground. The objective of the walking module is to generate appropriate walking patterns allowing the machine to walk in the desired direction. Walking gaits are produced like reflexes by the robot itself to adapt to the situation. With regard to the design of these gaits, emphasis has been put on increasing speed and mastering transitions. Finally, the machine should be given a minimum of intelligence since it has to manage vision information and its walking gaits by itself. When involved in situations of cooperation or competition or both, like in a soccer game, a high-level supervision task is welcome. This paper presents detailed developments of these three points and describes how they are implemented on a real robot.     

Implementation of omnidirectional crawl for a quadruped robot

As a reptile animal crawls in a cluttered environment, so a quadruped robot should be able to crawl on an irregular ground profile with its static stability by adopting the straightgoing and standstill-turning free gaits. The generalized and explicit formulations for the automatic generation of straight-going gaits and various standstill-turning gaits are presented in this paper. The maximized stride for the straight-going gait and the maximum turning angle for the turning gait of a quadruped robot named TITAN-VIII in a gait cycle are discussed by considering the robot's mechanism constraints and the irregularities of the ground profile. The control algorithm, including control of the joint positions of the robot, is described to implement the desired walking path of the quadruped robot. The effectiveness of the proposed method is demonstrated through experimental result.     

The standard circular gait of a quadruped walking vehicle

A quadruped walking vehicle has the potential capability of being developed into a vehicle of high mobility and adaptability to terrain by making use of its high degree of motion freedom. The authors have investigated the gait control problems of a walking vehicle, i.e. the straightforward or crab walk of the vehicle on rough terrains. This paper introduces a more generalized gait, namely, a circular gait around an arbitrarily located turn center, and discusses a standard circular gait. The standard circular gait is the one which maximizes the speed of walking and the rotational angle in a circular walk, and this consideration forms the basis of the discussion on advanced gait control problems. This paper formalizes the problems and analyses them by using mathematical optimization methods such as non-linear programming. Computations are carried out on a TITAN III, the quadruped walking vehicle model constructed by the authors. Several characteristics of the optimum gait and the final gait selection chart are derived. The validity of these conditions was verified by a circular walking experiment using the TITAN III.     

A CMAC neural-network-based algorithm for the kinematic control of a walking machine

In this paper a hierarchical, neural network control architecture of a walking machine is proposed. The neural network is based on the theory of the Cerebellum Model Articulation Controller (CMAC) which is a neuromuscular control system. Some preliminary studies of kinematic control and gait synthesis are presented to demonstrate the effectiveness of the CMAC neural network. After having been trained to learn the multivariable, nonlinear relationships of the leg kinematics and gaits, CMAC is utilized to perform feedforward kinematic control of a quadruped in straight-line walking and step climbing. Simulation examples are provided and discussed. This algorithm can be extended to control other highly nonlinear processes which are hierarchical in nature and cannot be modeled by mathematical equations.     

Fault-tolerant locomotion of the hexapod robot

In this paper, we propose a scheme for fault detection and tolerance of the hexapod robot locomotion on even terrain. The fault stability margin is defined to represent potential stability which a gait can have in case a sudden fault event occurs to one leg. Based on this, the fault-tolerant quadruped periodic gaits of the hexapod walking over perfectly even terrain are derived. It is demonstrated that the derived quadruped gait is the optimal one the hexapod can have maintaining fault stability margin nonnegative and a geometric condition should be satisfied for the optimal locomotion. By this scheme, when one leg is in failure, the hexapod robot has the modified tripod gait to continue the optimal locomotion.