A lattice-type reconfigurable robotic system for achieving gaits of chain-type robots

Traditional lattice-type reconfigurable robots can only achieve the flow-style locomotion with low efficiency. Since gaits of chain-type robots are proved to be efficient and practical, this paper presents a novel lattice distortion approach for lattice-type reconfigurable robots to achieve locomotion gaits of chain-type robots. Using this approach, the robotic system can be actuated by local lattice distortion to move as an ensemble. In this paper, a rule that makes the lattice distortion equivalent to joint rotation is presented firstly. Then, a kind of module structure is designed according to requirements of the lattice distortion. Finally, a motion planning for achieving locomotion is developed, which works well in physics-based simulations of completing a serpentine locomotion gait of a snake-like robot and a tripod gait of a hexapod robot.     

六边形对称分布六腿机器人的典型步态及其运动性能分析

为了便于在不同地理条件下合理地选择较优的步态,实现稳定高效的智能行走,本文针对一种六边形 对称分布的六腿机器人研究其不同步态的优劣．主要从行走能力、稳定性和能耗3 个角度对六边形对称结构的六腿 机器人在同样占空比下的3 种静态稳定周期步态进行了比较研究,此外还简要分析了其越障能力和穿越窄道的能 力．研究分析结果表明3 种步态（横向昆虫式摆动步态、哺乳动物式踢腿步态和混合步态）在不同条件下各有优劣： 横向昆虫式摆动步态在能耗和越障能力方面较其他两种步态有优势;而混合步态在稳定性上最具优势,其它能力处 于中间;哺乳动物式踢腿步态则可穿越窄道,步长上较昆虫摆动步态略好．本文的研究工作为六边形对称结构的六 腿机器人在未知复杂地貌环境下的智能行走提供了重要参考．     

Planar legged walking of a passive-spine hexapod robot

This paper proposes a new legged walking method for a novel passive-spine hexapod robot. This robot consists of several body segments connected by passive body joints. Each of the body segments carries two 1-DoF (degree of freedom) actuated legs. The robot is capable of achieving planar legged walking by rapidly abducting and adducting its legs. To model the mobility of a robot based on this simple design, the candidate configurations from all possible configurations are first selected in a mobility analysis of the robot based on the screw theory. All the feasible sequences of these candidate configurations are then searched to form planar locomotion gaits. Next, locomotive performance of the gaits is analyzed. Finally, the proposed locomotion design and gait planning methods are verified through simulations and experiments.     

Effects of turning gait parameters on energy consumption and stability of a six-legged walking robot

Minimization of energy consumption plays a key role in the locomotion of a multi-legged robot used for various purposes. Turning gaits are the most general and important factors for omni-directional walking of a six-legged robot. This paper presents an analysis on energy consumption of a six-legged robot during its turning motion over a flat terrain. An energy consumption model is developed for statically stable wave gaits in order to minimize dissipating energy for optimal feet forces distributions. The effects of gait parameters, namely angular velocity, angular stroke and duty factors are studied on energy consumption, as the six-legged robot walks along a circular path of constant radius with wave gait. The variations of average power consumption and energy consumption per unit weight per unit traveled length with the angular velocity and angular stroke are compared for the turning gaits of a robot with four different duty factors. Computer simulations show that wave gait with a low duty factor is more energy-efficient compared to that with a high duty factor at the highest possible angular velocity. A stability analysis based on normalized energy stability margin is performed for turning motion of the robot with four duty factors for different angular strokes.     

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。     

面向仿人机器人自然步态规划的人体步行实验分析

自然步态规划方法是实现仿人机器人步态柔顺和能量优化的可行方法,该方法要求对人体步行及其平衡策略进行定量研究．本文分析自然步态规划方法的原理,建立了一套快捷有效的人体步态测试系统,并通过实验建立了人体步行的参数化数据库．实验结果揭示了人体步行的参数化特征及其平衡策略,对于仿人机器人的自然步态规划及控制提供了理论指导．结论特别指出,仅仅通过规划的方式实现仿人机器人的自然步态是不完备的,自然步态的实现必须同仿生控制策略相结合．同时实验结论对于仿人机器人的本体优化设计也提供了参考．     

基于CPG的沙漠蜘蛛机器人多模式运动控制方法

模仿具有多种运动模式的沙漠蜘蛛,设计了本体为双层六杆5R闭链机构的仿蜘蛛机器人,其中16个主动关节由直流伺服电机控制．提出了基于Hopf振荡器的中枢模式发生器（CPG）运动控制模型,用于实现仿蜘蛛机器人的翻滚、爬行、侧滚等多种运动模式以及步态切换．利用Matlab和ADAMS对仿蜘蛛机器人的多模式运动进行动力学仿真,结果表明机器人可实现连续平稳的翻滚、爬行、侧滚运动,验证了CPG仿生控制方法应用于闭链机器人多模式运动的可行性．     

小型两栖仿龟机器人多模式运动研究

针对浅滩环境和水下狭窄空间的科研考察、资源勘探等任务,提出一种“腿－多矢量喷水”复合驱动的小型两栖仿龟机器人。通过研究“腿－多矢量喷水”复合式驱动系统的运动机理,设计仿生爬行步态和旋转步态。根据“腿－多矢量喷水”复合驱动机构的变结构特性,提出“H”、“工”和“X”等多模式运动。通过机器人水中运动学建模,建立基于实时动态推力矢量分配优化机制的水中3维自主运动控制方法。最后搭建机器人原型机,陆地上的多地形运动实验验证了机器人在非结构化浅滩环境中的适应能力强,水中运动控制实验验证了两栖机器人多模式运动控制的灵活性和可行性。     

A versatile locomotion mechanism for amphibious robots: eccentric paddle mechanism

Most of recently developed rescue robots can only be deployed to limited attacked regions after tsunami and the floods, due to their limited mobility on complex amphibious terrains. To access such amphibious environments with improved mobility, we propose a novel eccentric paddle mechanism (ePaddle) which has a set of paddles eccentrically placed in a wheel to perform multiple terrestrial, aquatic, and amphibious gaits. One of the advantages of our proposed ePaddle mechanism is its unique locomotion versatility introduced by the eccentric distance between the paddle shaft and the wheel center. We demonstrate this versatility by proposing five typical gaits for traveling on different terrains. For instance, wheeled rolling gait is used to achieve high-speed locomotion on even terrain. Legged gait is applied to travel on the rough terrains. To access the soft terrains where wheels slip and legs sink, a wheel-leg-integrated gait is performed by digging the paddle into the ground. To swim in the water, rotational paddling and oscillating paddling gaits are proposed. For each of these gaits, standard gait sequence is defined and joint parameters are calculated based on kinematics. An ePaddle prototype is then built and tested with the proposed gait sequences. Experimental results verify the design of the ePaddle mechanism as well as its versatile gaits.     

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.     

NSGA-Ⅱ在蛇形机器人中的优化与控制

研究蛇形机器人蜿蜒运动步态的优化与控制问题。结合摩擦力模型,并分析蛇形机器人运动步态模型,根据基于闭环反馈的控制系统结构运用PID控制器对其步态进行跟踪控制,在此基础上采用基于非支配排序遗传算法(NSGA-Ⅱ)对步态进行优化,该优化方法实现对闭环反馈跟踪控制系统的参数优化。仿真结果表明,NSGA-Ⅱ算法能达到变量优化目的,在功率和速度之间寻找最优值,对于解决蛇形机器人运动步态多目标优化问题是可行有效的。     

Self-organized adaptive legged locomotion in a compliant quadruped robot

In this contribution we present experiments of an adaptive locomotion controller on a compliant quadruped robot. The adaptive controller consists of adaptive frequency oscillators in different configurations and produces dynamic gaits such as bounding and jumping. We show two main results: (1) The adaptive controller is able to track the resonant frequency of the robot which is a function of different body parameters (2) controllers based on dynamical systems as we present are able to “recognize” mechanically intrinsic modes of locomotion, adapt to them and enforce them. More specifically the main results are supported by several experiments, showing first that the adaptive controller is constantly tracking body properties and readjusting to them. Second, that important gait parameters are dependent on the geometry and movement of the robot and the controller can account for that. Third, that local control is sufficient and the adaptive controller can adapt to the different mechanical modes. And finally, that key properties of the gaits are not only depending on properties of the body but also the actual mode of movement that the body is operating in. We show that even if we specify the gait pattern on the level of the CPG the chosen gait pattern does not necessarily correspond to the CPG’s pattern. Furthermore, we present the analytical treatment of adaptive frequency oscillators in closed feedback loops, and compare the results to the data from the robot experiments.

基于静平衡的四足机器人直行与楼梯爬越步态

为提升四足机器人的障碍爬越能力,采用稳定裕度作为四足机器人静态稳定的判据,以落足点形成的 象限边界明确了不同初始位姿机器人的迈腿可能性．基于迈腿次序将所有步态划分为24 种类型．利用运动空间需 求最小、稳定裕度最大、步态协调性最好3 个基本评价指标,对四足机器人的24 种基本步态进行了对比分析．提出 了基于投影分析法结合平面静平衡步态理论的楼梯爬越步态研究方法,并以上述3 个特性参数最佳为要求,对楼梯 爬越步态进行了系统仿真,所得结果为四足机器人的直行与楼梯爬越步态选择提供了理论依据．实验表明了所研究 方法的有效性．     

Development of a new spinning gait for a planar snake robot using central pattern generators

In this paper, we first present dynamic equation of n-link snake robot using Lagrange’s method in a simplified matrix form and verify them experimentally. Next, we introduce a new locomotion mode called spinning gait. Central pattern generators (CPGs) are used for online gait generation. To realize spinning gait, genetic algorithm is used to find optimal CPG network parameters. We illustrate both theoretically, using derived robot dynamics and experimentally that the CPG-based online gait generation method allows continuous and rather smooth transitions between gaits. Lastly, we present an application where the snake robot is guided from an initial to final position while avoiding obstacles by changing CPG parameters.     

仿蟹机器人步态分析与仿真

在仿蟹机器人的行走控制中,步态的选择对机器人的稳定快速行走具有至关重要的作用。本文对仿蟹八足机器人的基本步态进行了分类,并进一步对八足波形步态进行分析,得出八足步行机器人在采用双四足步态的行走方式时,既可以满足速度的要求,又可以保证机器人的稳定性。通过计算机软件ADAMS对所选步态进行全局仿真,结果验证了步态规划的合理性,同时得到了机器人相关物理量的变化曲线,为进一步选择电机,分析机器人系统的动态特性提供了依据。     

Experimental study on the oscillating paddling gait of an ePaddle mechanism with flexible configuration

In this paper, a novel eccentric paddle locomotion mechanism (ePaddle) has been proposed to enhance the mobility of amphibious robots for multi-terrains tasks with diverse locomotion gaits. The oscillating paddling gait of the ePaddle mechanism enables the robot to perform stationary observation or attitude maneuvering operations in shallow water. To increase the thrust generated by this gait, the ePaddle mechanism has a flexible configuration, i.e. a flexible paddle and three rigid paddles. The effects of the oscillating amplitude and period of the gait to thrust are analyzed and compared with the thrusts measured with rigid configuration. Experimental results demonstrate that the flexible configuration is able to produce much more net thrust than the rigid configuration when the ePaddle is oscillating at large amplitude.     

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.     

An approach to analyzing biped locomotion dynamics and designing robot locomotion controls

An approach to analyzing biped locomotion problems is presented. This approach applies the principles of Lagrangian dynamics to derive the equations of motion of locomotion gaits, state-variable techniques to analyze locomotion dynamics, and multivariable feedback to design locomotion controls. A robot model which has no knee joints or feet and is constrained to motion in the sagittal plane is chosen as a sufficiently simple model of a biped to illustrate the approach. A goal of the analysis is the design of a locomotion control for the robot which produces a walking gait having a velocity and stride length similar to those of a human walking gait. The principle feature of the approach is a much deeper understanding of the dynamics of biped locomotion than previous approaches have provided.     

Gait transition for a quadrupedal robot by replacing the gait matrix of a central pattern generator model

The pattern-generator-based approach for legged robot control is inspired by biological neural mechanisms of locomotion, in which a special challenge is gait transition. In this paper we build a holosymmetric central pattern generator model and propose parameter-setting principles for a gait matrix capable of producing typical quadrupedal gaits, and based on them present an approach of directly replacing the gait matrix for gait transition, with a focus on three problems emerging during transition: breakpoint, phase-lock and oscillation-stop. Breakpoints are smoothed by remaining the current outputs during transition, similar to a zero-order holder. Breaking the phase-lock is accomplished by adding a perturbation to the state matrix at the transiting point. An oscillation-stop of less than one period can be ignored. With such treatments, it is proved that gait transitions between any two gaits on a quadrupedal robot can be achieved at arbitrary phase locations in a walk cycle, theoretically and experimentally in part.     

An aperiodic Z type spinning gait planning method for a quadruped walking robot

Spinning gaits are used for altering the direction of body in a narrow space. Previous studies reveal thatz type leg-lifting sequence is suitable for spinning motion. In this paper, we focus on anz type aperiodic spinning gait for a quadruped walking robot. We proposed a condition of support pattern suitable for the aperiodicz type spinning motion. Based on the condition, we proposed an aperiodicz type spinning gait planning method. It is shown that spinning capability can be independent of required stability margin. A simulation shows that good spinning capability and good terrain adaptability are obtained.