A control for an insectomorphic robot in climbing to the top of a vertical corner and in moving on a step ladder

For a six-legged robot, the problem of climbing a roof of a vertical right dihedral corner along its walls and a vertical high shelf with the help of a step ladder is investigated. The motions are realized with the help of the dry friction forces. The motion of the robot is formed by imposing servo-constraints in the form of adaptive step cycles of legs and the required geometric structure of body motion. An asymptotically stable program motion of legs relative to the body and the whole system is implemented by a PD controller. The results of 3D computer simulation of the controlled robot dynamics are presented.     

Feedforward and Feedback Dynamic Trot Gait Control for Quadruped Walking Vehicle

To realize dynamically stable walking for a quadruped walking robot, the combination of the trajectory planning of the body and leg position (feedforward control) and the adaptive control using sensory information (feedback control) is indispensable. In this paper, we propose a new body trajectory, the 3D sway compensation trajectory, for a stable trot gait; we show that this trajectory has a lower energy consumption than the conventional sway trajectory that we have proposed. Then, for the adaptive attitude control method during the 2-leg supporting phase, we consider four methods, that is, a) rotation of body along the diagonal line between supporting feet, b) translation of body along the perpendicular line between supporting feet, c) vertical swing motion of recovering legs, and d) horizontal swing motion of recovering legs; we then describe how we verify the stabilization efficiency of each method through computer simulation, stabilization experimentation, and experimenting in walking on rough terrain using the quadruped walking robot, TITAN-VIII.     

Motion control for an insectomorphic robot on a movable ball

The problem of motion design of a six-legged robot with the help of a ball rolling on a horizontal support plane is investigated. The robot motion is synthesized in order to accelerate or decelerate the ball in the direction of the longitudinal axis of the body and to provide a dynamic stability of the robot on the ball. It is executed with the help of dry friction forces. The motion of the body and legs is executed by imposing servoconstraints in the form of adaptive step cycles of legs and the required geometrical structure of body motion. Asymptotically stable program motion of legs with respect to the body and the entire system is provided by a PD-controller. The results of 3D computer simulation of the controlled robot dynamics are presented.     

An insectomorphic robot climbing over a freely rolling ball

An algorithm for the control of an insectomorphic robot climbing over a ball that rolls freely on a horizontal plane is developed and tested using computer simulation. The proposed motion involves three maneuvers. First, the robot climbs the ball at rest from the horizontal surface. At the end of this maneuver, the ball gains an angular velocity due to errors in the execution of the programmed motion. The further motion of the robot is designed so as to reduce the velocity gained in the course of climbing to an acceptable level. The motion is completed by the maneuver of getting down to the supporting horizontal plane from the almost motionless ball. The robot motion is implemented using the Coulomb friction without any special devices. The asymptotic stability of the programmed motion of the system as a whole is ensured by a PD controller that implements the step cycles of the leg motions and the planned motion of the body. Results of 3D computer simulation of the robot motion are discussed. The model of the mechanical robot-ball system is formed using the Universal Mechanism program package; this model is described by an automatically derived system of differential equations that take into account the dynamics of all solid elements.     

Insectomorphic robot climbing a freely rolling ball

The problem of control of autonomous motion of a six-legged robot from a support horizontal plane to a ball that can freely move on this plane in an arbitrary direction is solved. Further robot motion aimed at acceleration or deceleration of the ball both in the direction of the longitudinal axis of its body and in the transverse direction ensuring dynamic stability of the robot on the ball is synthesized. Analytical conditions of implementability of the maneuver of climbing a ball are found. Formulas for estimating the maximum ball radius for which climbing of the robot is possible are obtained. Using the developed control algorithms, the robot can climb the ball and, staying on it, move the ball to the desired position in the plane. Robot motion is performed owing to the dry friction forces. Asymptotic stability of the programmed motion of the whole system is provided by a PD controller, which implements necessary step cycles of legs motion and the planned law of body motion. Results of 3D computer simulation of the controlled robot dynamics are discussed.     

压电谐振驱动三足机器人的平面运动

设计并实现了一类利用压电陶瓷片作动,由三条曲梁足支撑的振动驱动机器人.建立了在一条足共振驱动下机器人水平运动的动力学方程,数值计算解释了摩擦作用下的运动机理,寻找到异性摩擦对运动方向、速度的影响和压电激励频率与运动速度间的关系.通过建立圆弧曲梁控制方程求解圆弧型足面内振动的固有频率及振型,设计了三组不同频率的圆弧曲梁足参数,实验制作了机器人模型,利用压电控制三足间振动的共振切换,实现了预想的三个方向的运动以达到平面运动的效果,实验测量了机器人的运动速度与理论计算吻合得较好.     

Ladder Climbing Method for the Limb Mechanism Robot ASTERISK

A ladder climbing method for the limb mechanism robot ASTERISK is proposed. This robot has six legs. The upper three legs hold on to the upper rung from both sides alternately, just like pinching it. The lower three legs hold on to the lower rung in the same way. Hence, the robot can take hold of the ladder stably. First, the robot releases the left upper and lower legs from the current rungs, and hangs them on the next rungs while supporting itself with the other four legs. Then, the mid two legs and the right two legs are moved to the next rungs in sequence. Finally, the robot lifts up its body using the six legs. Depending on the relative pose of the robot to the ladder, the robot automatically selects the legs that can support vertical and/or horizontal forces applied by the rungs. The robot then distributes its weight to the legs supporting the vertical force based on their force margins. The legs that cannot support forces are controlled to always touch the rungs slightly in order to pinch the rungs with the other legs. The advantages of the proposed gait and control method are verified by analysis of the leg workspace for generating the ladder climb gait, analysis of the range of force direction that the legs can support, analysis of the joint torques required for ladder climbing and an experiment on force distribution. Finally, the range of ladder pitch variation that ASTERISK can climb is clarified.     

适用多种环境的救灾勘探四足仿生机器狗

随着自然灾害的频发,救援人员的伤亡人数也在增加,机器人代替人完成救援工作成为研究热点。根据对国际相关领域研究成果的分析,设计了一款稳定性高,环境适应能力强的仿生四足机器狗。全身支架采用铝合金打造,腿部采用碳纤维打造,搭配大扭矩电机,结合六自由度机械臂,实现不同地形环境下的前进方式转换。基于前肘后膝式的腿型设计并结合ADAMS仿真,实现稳定行走。结合气体检测和图像识别模块,实现救灾现场的环境勘探和搜救任务。基于稳定裕度最优化的原则,采用对角步态的行走步态控制方式。公布了8自由度前肘后膝X腿型式四足机器狗机械设计及其步态控制方案。     

一种多模型融合的仿猎豹四足机器人复杂运动控制方法

针对具有2自由度主动脊柱关节的仿猎豹四足机器人,基于任务分解思想和生物神经系统机理,提出多模型融合的控制方法。该方法以弹簧负载倒立摆模型实现单腿跳跃控制,通过中枢模式发生器（CPG）实现4条腿之间以及脊柱―腿之间的协调控制,利用虚拟模型控制实现机器人与环境交互,采用基于CPG输出的有限状态机来融合3个控制模型,构建仿猎豹四足机器人的多模型分层运动控制器。参考猎豹脊柱运动特征,设计了机器人脊柱关节运动模式,给出脊柱与腿的协调控制策略。最后,在Webots仿真环境中搭建了仿猎豹四足机器人虚拟样机,实现了不同步态下的脊柱―腿的协调控制、在崎岖地形上稳定奔跑,以及平滑的对角―疾驰―对角步态转换,仿真结果验证了所提出的多模型融合的四足机器人运动控制方法的有效性。     

Posture Stabilization Strategy for a Trotting Point-foot Quadruped Robot

This paper proposes a posture stabilization strategy for achieving the stable trot gait of a point-foot quadruped robot. Specifically, a stepping strategy (foot placement strategy) has been developed to achieve a stable trot gait. Because in the trot gait of a quadruped robot the diagonal legs can be considered to contact and leave the ground at the same time, the trot gait can be considered as a virtual biped gait. Based on the dynamic model of a virtual biped gait, the stepping point (or the foot placement) that achieves the stabilization of the robot is determined. Finally, the effectiveness of the proposed posture stabilization strategy is validated experimentally.     

Dynamic Analysis Tool for Legged Robots

The paper introduces a systematic approach for dealing with legged robot mechanism analysis. First, we briefly summarize basic mathematical tools for studying the dynamics of these multi-loop and parallel mechanisms using a unified spatial formulation which is useful for computer algorithms. The dynamic behavior analysis is based on two stages. The first one deals with establishing the equations of motion of the whole mechanism including legs tip impact effects and allowing us to solve the direct and inverse dynamic problems. The second concerns the feet–ground interaction aspect which is one of the major problem in the context of dynamic simulation for walking devices. We focus on the phenomenon of contact by introducing a general model for dynamic simulation of contacts between a walking robot and ground. This model considers a force distribution and uses an analytical form for each force depending only on the known state of the robot system. Finally, some simulation results of biped robot are given. The simulation includes all phenomena that may occur during the locomotion cycle: impact, transition from impact to contact, contact during support with static friction, transition from static to sliding friction and sliding friction.     

Gait optimization of step climbing for a hexapod robot

RHex-style hexapod robot is a type of legged robot which can perform multiple moving gaits according to different applications, due to its simple structure and strong mobility. However, traversing high obstacles has always been a big challenge for legged robots. In this paper, gait optimization of a hexapod robot is proposed for climbing steps at different heights, which even enables the robot to climb the step 3.9 times of the leg length. First, a previous step-climbing gait is optimized by adjusting body inclination when placing front legs on top of the step, which enables RHex with different sizes to perform the rising stage of the gait. Second, to improve the climbing heights, a novel quasi-static climbing gait is proposed by using the reversed claw-shape legs to reach the higher step. The nondeformable legs are used to raise the center of mass (COM) of the body by lifting the front and rear legs alternately so that the front legs can reach the top of the step, then the front and middle legs are lifted alternately to maneuver COM up onto the step. The simulations and dynamic analysis of climbing steps are utilized to verify the feasibility of the improved gait. Finally, the step-climbing experiments at different heights are performed with the optimized gaits to compare with the existing gaits. The results of simulations and experiments show the superiority of the proposed gaits due to climbing higher steps.     

四轮驱动滑动吸盘爬壁机器人的动力学研究

研究了四轮驱动滑动吸盘式爬壁机器人在滑动导向运动方式下的动力学问题．首先分析了机器人在壁面上安全移动的运动状态和约束条件, 然后对驱动轮支撑力分布、驱动轮与壁面间的横向摩擦力以及密封圈摩擦力进行分析,进而基于牛顿---欧拉法建立了机器人的动力学方程, 并用驱动力矩安全系数来表征驱动力矩的安全程度．通过动力学仿真,分析了吸附压力、驱动轮分布、密封圈刚度等对驱动力矩的影响, 为四轮驱动滑动吸盘式爬壁机器 人结构优化和安全运动控制提供理论依据．     

毫米级潜艇形机器人在低雷诺数液体中的3D运动及微操作方法研究

为模拟机器人在人体环境中的3D运动及微操作,提出了毫米级潜艇形机器人在低雷诺数液体中保持水平姿态实现3D运动及执行微操作的方法.首先,设计并加工了潜艇形机器人以及4线圈磁驱动系统,通过COMSOL软件对磁场系统进行了有限元仿真.然后,对机器人在低雷诺数液体环境中的受力情况进行了分析,建立了机器人运动模型并研究了其多种运动模式.机器人在低雷诺数液体中可以保持水平姿态沿设定路线运动,包括垂直上升、对角上升、直角运动、螺旋上升等3D运动,最大运动速度为1.2 mm/s.通过设计的无线能量传输系统将电能引入到小尺度空间,机器人可通过无线电能驱动其前端的夹持器执行夹取、搬运、释放等微操作.     

仿蟹机器人交错等相位波形步态研究

在观察生物螃蟹的基础上,研制了仿蟹机器人实验样机.利用事件序列法对生物螃蟹的行走过程进行了分析,提出了仿蟹机器人交错等相位波形步态.交错等相位波形步态以2n足波形步态为基础,将8个步行足交错分为两组,通过调节组内先后摆动的两步行足间的相位因子,使同组的各步行足相位平均分配在一个步态周期内,以减小机体能量损耗.仿蟹机器人...     

Stability Analysis of a Wheel-Track-Leg Hybrid Mobile Robot

This paper proposes a new wheel-track-leg hybrid robot. The hybrid robot comprises a robot body, four driving mechanisms, four independent track devices, two supporting legs and one wheel lifting mechanism, which can fully benefit different advantages from wheeled, tracked and legged robots to adapt itself to varied landforms (the rough terrain and high obstacle). Based on the symmetrical mechanical structure, locomotion modes of the mobile robot are analyzed. With the coordinate transformation matrix, the center of mass of the robot is described. Moreover, the stability pyramid method is used to analyze on the climbing motion, especially in the hybrid locomotion mode. Through theoretical analysis, simulation and experimental verification, it’s proven that the robot can remain stable in the process of climbing motion.     

基于改进蚁群算法的四足机器人步态规划

四足机器人关节众多、运动方式复杂,步态规划是四足机器人运动控制的基础。传统的算法多基于仿生原理,缺乏广泛适应性。 在建立运动学方程的基础上,提出了一种基于改进蚁群算法的步态规划算法。该算法利用了四足机器人4条腿运动的线性无关性,将步态规划问题转换为在四维空间里求取最长路径问题。仿真结果表明,该算法得出了满足约束条件的所有步态,最后通过机器人样机检验,验证了该算法求取结果的有效性和合理性。     

基于CPG的六足机器人运动步态控制方法

中枢模式发生器（CPG）在六足机器人的运动步态控制中起着至关重要的作用。为了研究六足机器人的运动控制方法,首先基于仿生学原理设计了六足机器人的机械结构,并在虚拟样机软件ADAMS中搭建其三维模型;其次选择Hopf振荡器作为CPG单元,并改进了振荡器模型;然后设计了六足机器人的CPG网络拓扑结构,包含单腿关节映射函数方案和腿间CPG环形耦合网络方案,并对其进行了改进;最后通过ADAMS和MATLAB联合仿真实验,验证了所设计六足机器人的运动稳定性和CPG控制方案的可行性与有效性。仿真结果表明,该方法能够满足六足机器人不同运动步态的控制需求,对六足机器人的运动控制具有一定的实际应用价值。     

Ground adaptive and optimized locomotion of snake robot moving with a novel gait

In this paper, we present a novel gait, forward head serpentine (FHS), for a two dimensional snake robot. The advantage of this new gait is that the head link remains in the forward direction during motion. This feature significantly improves snake robot potential applications. Genetic Algorithm (GA) is used to find FHS gait parameters. Relationship between FHS gait parameters and friction coefficients of the ground are developed. Next, robot speed is considered in the optimization. A fitness function covering robot speed and head link angular changes is defined. A general sinusoidal wave form is applied for each joint. GA is used to find gait parameters resulting in maximum speed while head link angular changes remain in an acceptable range. Optimal gait parameters are also calculated for different friction coefficients and relationships between them are developed. Experiments are also performed using a 5-link snake robot. It is shown that experimental and theoretical results closely agree.     

Experimentally Verified Optimal Serpentine Gait and Hyperredundancy of a Rigid-Link Snake Robot

In this study, we examine, for a six-link snake robot, how an optimal gait might change as a function of the snake- surface interaction model and how the overall locomotion performance changes under nonoptimal conditions such as joint failure. Simulations are evaluated for three different types of friction models, and it is shown that the gait parameters for serpentine motion are very dependant on the frictional model if minimum power expenditure is desired for a given velocity. Experimental investigations then motivate a surface interaction model not commonly used in snake locomotion studies. Using this new model, simulation results are compared to experiments for nominal and nonnominal locomotion cases including actuator faults. It is shown that this model quite accurately predicts locomotion velocities and link profiles, but that the accuracy of these predictions degrades severely at speeds where actuator dynamics become significant.