液压四足机器人足端的力预测控制与运动平稳性

针对液压四足机器人在坚硬路面行走时,足端位置易受刚性冲击,导致运动姿态平稳性差的问题,提出一种液压四足机器人足端力预测控制方法.在分析液压四足机器人结构的基础上,根据运动学与力学模型构建了液压伺服系统的力控制模型;采用改进自适应布谷鸟优化BP神经网络算法建立足端力预测控制模型,通过仿真对比分析验证了该算法的可行性.最后...     

四足机器人改进型对角小跑步态研究

传统的四足机器人对角小跑步态一般在机体坐标系中进行规划,在实际应用中存在着摆动腿无法同时着地、机体翻转无法有效抑制等问题,这些都降低了机器人运动的稳定性和精确性。针对以上问题,提出了一种在世界坐标系下规划的改进型对角小跑步态方法,该方法通过浮动机体运动学对摆动相进行规划,在足端的雅可比矩阵中引入机体姿态相关项,从而保证了摆动腿能同时着地,同时在支撑相和摆动相之间增加了四腿同时着地的调整相,对机器人机体位姿进行调整。对比仿真和样机试验结果表明：与传统方法相比,所提方法能够使摆动腿同时着地并能连续调整机体位姿,使机器人获得更好的运动稳定性和更高的位移控制精度。     

Mechanism of Spine Motion About Contact Time in Quadruped Running

The current research of quadruped robot focuses on the quadruped robot with spine motion. Contact time is a very important part of system performance. However, the mechanism of spine motion about contact time has not been clearly elucidated. In this paper, the e ect of spine motion on contact time is studied deeply from dynamic view.Firstly, a simplified model of the quadruped robot with spine joint is set up, its dynamic equations are derivated, and a method that can generate passive periodic locomotion is proposed. Secondly, according to the vertical spring oscillator model, the two-dimension planar locomotion of the simplified model is regarded as a special vibration in the vertical direction, and the approximate formula of calculating contact time is obtained. Finally, the approximate formula of calculating contact time is verified by the simulation results of passive periodic locomotion, and the e ect of spine motion on contact time is deeply discussed based on the approximate formula of calculating contact time. The discussion proves that spine motion indeed has little e ect on contact time, but spine motion can slightly reduce body pith movement and regulate the leg sti ness in leg contact phase. This research proposes an e ective research method which can be used to study the motion mechanism of the quadruped robot with spine motion,and the mechanism of spine motion about contact time is clearly elucidated which is helpful to set the parameters of mechanical structure and study control algorithm about the quadruped robot with spine motion.     

液压四足机器人机身扰动抑制及实验研究

针对液压四足机器人在运动过程中的机身扰动较大的问题,提出基于运动学和虚拟模型的液压四足机器人机身扰动抑制策略。分析机器人机身扰动产生的机理及其影响,建立四足机器人整机运动学方程,根据机器人实时姿态反馈抑制机身扰动。同时在机器人机身横滚和俯仰自由度上引入弹簧阻尼虚拟元件,通过调整虚拟力的大小控制机身姿态。面向机器人对角小跑步态,对机器人摆动相和支撑相进行足端轨迹规划。通过液压四足机器人平台进行实验验证,实验结果表明,该扰动抑制策略能够根据机器人的机身姿态调整关节角度,机器人机身起伏小,机器人实际运动轨迹与理论运动轨迹接近,验证了所提方法的有效性。     

类人猿型机器人前向四足步行的研究

类人猿机器人是一种具有多种移动方式的新型机器人。同常规的四足步行机器人相比,该机器人的结构具有特殊性和复杂性。为了实现拥有这种结构机器人的前向四足步行,我们提出了新的步态、轨迹规划、稳定平衡判据。仿真和实验结果证实了这些分析的合理性。     

Energy efficiency analysis of quadruped robot with trot gait and combined cycloid foot trajectory

Quadruped robots consume a lot of energy, which is one of the factors restricting their application. Energy efficiency is one of the key evaluating indicators for walking robots. The relationship between energy and elastic elements of walking robots have been studied, but different walking gait patterns and contact status have important influences on locomotion energy efficiency, and the energy efficiency considering the foot-end trajectory has not been reported. Therefore, the energy consumption and energy efficiency of quadruped robot with trot gait and combined cycloid foot trajectory are studied. The forward and inverse kinematics of quadruped robot is derived. The combined cycloid function is proposed to generate horizontal and vertical foot trajectory respectively, which can ensure the acceleration curve of the foot-end smoother and more successive, and reduce the contact force between feet and environment. Because of the variable topology mechanism characteristic of quadruped robot, the leg state is divided into three different phases which are swing phase, transition phase and stance phase during one trot gait cycle. The non-continuous variable constraint between feet and environment of quadruped robot is studied. The dynamic model of quadruped robot is derived considering the variable topology mechanism characteristic, the periodic contact and elastic elements of the robot. The total energy consumption of walking robot during one gait cycle is analyzed based on the dynamic model. The specific resistance is used to evaluate energy efficiency of quadruped robot. The calculation results show the relationships between specific resistance and gait parameters, which can be used to determine the reasonable gait parameters.     

浅析BigDog四足机器人

根据BigDog四足机器人目前已经公开的技术资料,对BigDog机器人的整体概况和主要核心技术点进行了分析。机械系统重点分析了BigDog的结构特性和运动特性,以及由此产生的高功率密度问题;通过剖析BigDog液压驱动系统基本构成,发现结构仿生的缺陷限制了BigDog机动性能的进一步提升。研究表明,复杂地形条件下BigDog的运动控制首先取决于姿态的检测和地形的感知,姿态安全是BigDog实现持续纵向运动的前提条件。基本行走控制算法研究表明,液压系统的输出特性,能良好地满足BigDog的动力需求;通过几种典型的运动状态分析,对BigDog的控制实现过程进行了诠释。因非结构化环境移动机器人的智能性主要取决于导航系统的设计,故重点分析了BigDog的导航系统,特别是全自主导航部分。最后结合课题组四足机器人的研究经历,对四足机器人的研发提出了一些建议。     

NOVEL FORMULATION OF STATIC STABILITY FOR A WALKING QUADRUPED ROBOT

By defining the static stable area for foot placement, a new approach to analysis of quadruped robot stability is presented. Unlike conventionally, the method avoids solving complicated direct kinematics of quadruped robot and shows the information on the robot stability and the selection of swing leg. Especially, the proposed algorithm can be used as real-time operation for on-line gait generation and control for quadruped robots. The effectiveness of the proposed approach is shown through a practical crawling experiment of the quadruped robot TITAN-VIII.     

基于机体翻转的四足机器人翻越台阶过程的运动学分析

为了提高四足机器人的越障能力,提出一种基于机体翻转的台阶翻越方法。在台阶翻越过程中,可以将四足机器人等效为平面连杆机构。对一个完整的翻越过程进行了运动规划,将其划分为5个阶段;然后分别对每个阶段进行了运动学建模与仿真分析,得到机器人各关节角位移的变化曲线以及机体重心的位移曲线。最后讨论了机器人台阶翻越能力与几何参数之间的关系,分析结果表明,采用该方法研制的四足机器人具有较强的台阶翻越能力。从运动学角度验证了四足机器人翻转式翻越台阶的可行性,对足式机器人的越障方式进行了有益的探索,为进一步的研究提供了理论基础。     

Design of a cyclic inhibitory CPG controller for the locomotion of a snakelike robot

The rhythmic locomotion of a creature is a self-excitation behavior of the CPG (central pattern generator), which makes it supremely adapted for environment. Based on this fact, firstly, a snake-like robot controller with cyclic inhibitory CPG model was designed, and then the stability of a single neuron, CPG model and the NON (neuron oscillator network) was analyzed. By implementing this control architecture to a simulator based on the mechanical dynamics of a real snake-like robot named Perambulator-I, we presented preliminary rules for parameter setting of the CPG controller to modulate the number of S shapes, the curve of the body shape, locomotion velocity, and the curve of the locomotion trajectory for serpentine locomotion. Moreover, we demonstrated that Perambulator-I can successfully exhibit serpentine locomotion by using the output of the proposed CPG controller. The results of this paper provide a realistic approach for designing an artificial CPG controller. __________ Translated from Chinese Journal of Mechanical Engineering, 2006, 42(5) (in Chinese)     

基于地面反力检测的四足马机器人适应步行法

为适应国内外对四足马机器人进行的广泛研究,根据四足马机器人的结构模型和步行稳定性分析,对其适应步行法进行了研究。首先,介绍了具有12个运动关节和球形脚部的四足马机器人结构模型,并求出了其运动学反解;其次,在分析步行稳定性和检测地面反力的基础上,提出了一种四足马机器人适应步行的实现方法;最后,通过自制的小型四足马机器人进行了适应步行实验。实验结果表明,所提出的四足马机器人适应步行法具有可行性。     

Kinematics and dynamics analysis of a quadruped walking robot with parallel leg mechanism

It is desired to require a walking robot for the elderly and the disabled to have large capacity,high stiffness,stability,etc.However,the existing walking robots cannot achieve these requirements because of the weight-payload ratio and simple function.Therefore,Improvement of enhancing capacity and functions of the walking robot is an important research issue.According to walking requirements and combining modularization and reconfigurable ideas,a quadruped/biped reconfigurable walking robot with parallel leg mechanism is proposed.The proposed robot can be used for both a biped and a quadruped walking robot.The kinematics and performance analysis of a 3-UPU parallel mechanism which is the basic leg mechanism of a quadruped walking robot are conducted and the structural parameters are optimized.The results show that performance of the walking robot is optimal when the circumradius R,r of the upper and lower platform of leg mechanism are 161.7 mm,57.7 mm,respectively.Based on the optimal results,the kinematics and dynamics of the quadruped walking robot in the static walking mode are derived with the application of parallel mechanism and influence coefficient theory,and the optimal coordination distribution of the dynamic load for the quadruped walking robot with over-determinate inputs is analyzed,which solves dynamic load coupling caused by the branches’ constraint of the robot in the walk process.Besides laying a theoretical foundation for development of the prototype,the kinematics and dynamics studies on the quadruped walking robot also boost the theoretical research of the quadruped walking and the practical applications of parallel mechanism.     

Controller tuning based on optimization algorithms of a novel spherical rolling robot

This study presents the construction process of a novel spherical rolling robot and control strategies that are used to improve robot locomotion. The proposed robot drive mechanism is constructed based on a combination of the pendulum and wheel drive mechanisms. The control model of the proposed robot is developed, and the state space model is calculated based on the obtained control model. Two control strategies are defined to improve the synchronization performance of the proposed robot motors. The proportional-derivative and proportional-integral-derivative controllers are designed based on the pole placement method. The proportional-integral-derivative controller leads to a better step response than the proportional-derivative controller. The controller parameters are tuned with genetic and differential evaluation algorithms. The proportional-integral-derivative controller which is tuned based on the differential evaluation algorithm leads to a better step response than the proportional-integral-derivative controller that is tuned based on genetic algorithm. Fuzzy logics are used to reduce the robot drive mechanism motors synchronizing process time to the end of achieving a high-performance controller. The experimental implementation results of fuzzy-proportional-integral-derivative on the proposed spherical rolling robot resulted in a desirable synchronizing performance in a short time.

     

基于虚拟样机技术的四足机器人步态规划与仿真

建立四足机器人质心与各关节角的关系,利用虚拟样机技术,通过质心轨迹来控制四足机器人的运动。首先,建立四足机器人质心与各关节角的运动学方程;然后,规划四足机器人的质心轨迹;最后,应用ADAMS建立虚拟样机模型,结合MATLAB对预定的质心轨迹进行联合仿真。通过对仿真结果中的机体位移、速度、关节转矩的响应曲线进行分析,并结合静力学仿真结果,对四足机器人的机构设计提出合理的简化方案。     

Gait Analysis of Quadruped Robot Using the Equivalent Mechanism Concept Based on Metamorphosis

The previous research regarding the gait planning of quadruped robot focuses on the sequence for lifting o and placing the feet, but neglects the influence of body height. However, body height a ects gait performance significantly, such as in terms of the stride length and stability margin. We herein study the performance of a quadruped robot using the equivalent mechanism concept based on metamorphosis. Assuming the constraints between standing feet and the ground with hinges, the ground, standing legs and robot body are considered as a parallel mechanism, and each swing leg is regarded as a typical serial manipulator. The equivalent mechanism varies while the robot moves on the ground. One gait cycle is divided into several periods, including step forward stages and switching stages. There exists a specific equivalent mechanism corresponding to each gait period. The robot's locomotion can be regarded as the motion of these series of equivalent mechanisms. The kinematics model and simplified model of the equivalent mechanism is established. A new definition of the multilegged robot stability margin, based on friction coe cient, is presented to evaluate the robot stability. The stable workspaces of the equivalent mechanism in the step forward stage of trotting gait under di erent friction coe cients are analyzed. The stride length of the robots is presented by analyzing the relationship between the stable workspaces of the equivalent mechanisms of two adjacent step forward stages in one gait cycle. The simulation results show that the stride length is larger with increasing friction coe cient. We herein propose a new method based on metamorphosis, and an equivalent mechanism to analyze the stability margin and stable workspace of the multilegged robot.     

液压机器人作动器建模及关节转角跟踪控制

针对液压四足机器人作动器伺服精度较差问题,分别推导电液伺服作动器在摆动相、刚性支撑相和弹性支撑相的等效模型,分析各作动器模型特点,提出比例内环自适应幅相控制外环的复合控制策略,应用比例控制器保证位置内环的稳定性,采用自适应幅相控制器进行幅值和相位补偿。通过机器人单腿测试平台进行控制策略验证,实验结果表明:所提控制策略可使系统幅值衰减小于2%,相位滞后小于4°,验证了此方法的有效性。     

Reinforcement learning and neural network-based artificial intelligence control algorithm for self-balancing quadruped robot

Journal of Mechanical Science and Technology - This paper proposes an artificial intelligence (AI)-based new control algorithm for a self-balancing quadruped robot. A quadruped robot is a good...     

一种新型四足变胞爬行机器人的步态规划研究

随着移动机器人在探测救援中的应用逐渐增多,活动灵巧、环境适应能力强的多足机器人越来越受到国内外学者的关注。介绍一种腰部可以活动的四足机器人的设计及其步态生成,并展示了活动腰部可提升机器人对极端环境的适应性。提出三个基本假设以简化机构模型,提出腰部构态变换规则,并用几何方法说明了腰部构型变化可扩大机器人腿部活动空间,从而提升对复杂环境的适应性。另外,腰部运动与步态融合,生成了两种新的基本步态——扭腰直行步态和原地旋转步态。基于提出的两种步态,对比了固定腰部与可动腰部条件下运动稳定裕度的变化,分别计算了狭窄弯道通过条件,并分析了所设计步态对头部视觉的影响,从而证明所设计机器人具有较高的极端环境适应能力。     

Energy Expenditure of Trotting Gait Under Different Gait Parameters

Robots driven by batteries are clean, quiet, and can work indoors or in space. However, the battery endurance is a great problem. A new gait parameter design energy saving strategy to extend the working hours of the quadruped robot is proposed. A dynamic model of the robot is established to estimate and analyze the energy expenditures during trotting. Given a trotting speed, optimal stride frequency and stride length can minimize the energy expenditure. However, the relationship between the speed and the optimal gait parameters is nonlinear, which is difficult for practical application. Therefore, a simplified gait parameter design method for energy saving is proposed. A critical trotting speed of the quadruped robot is found and can be used to decide the gait parameters. When the robot is travelling lower than this speed, it is better to keep a constant stride length and change the cycle period. When the robot is travelling higher than this speed, it is better to keep a constant cycle period and change the stride length. Simulations and experiments on the quadruped robot show that by using the proposed gait parameter design approach, the energy expenditure can be reduced by about 54% compared with the 100 mm stride length under 500 mm/s speed. In general, an energy expenditure model based on the gait parameter of the quadruped robot is built and the trotting gait parameters design approach for energy saving is proposed.     

中枢模式发生器与足端轨迹的非线性映射

控制的仿生性和行走的稳定性是四足机器人步态研究中重要的两个方面。 为了提高四足机器人运动的稳定性,本文通 过 Hopf 振荡器搭建了 CPG 模型,分别实现了多种步态及步态之间的转换。 比较了基于 CPG 的步态控制方法和轨迹规划的步 态规划方法在行走上的优劣性。 为了同时利用 CPG 控制和轨迹规划的优点,提出采用神经网络将 CPG 控制曲线与足端轨迹 逆运动学获得的驱动曲线进行非线性映射,使得四足机器人在控制上具备仿生特性,在足端接触上具备零冲击特性。 仿真和实 验结果表明,采用 CPG 的步态生成方法和轨迹规划方法四足机器人的行走速度理论行走速度 80 mm/ s 相近,但采用 CPG 的步 态生成方法四足机器人侧向位移在±10 mm 以内且俯仰角在±1. 5°之间,而采用轨迹规划的控制方法四足机器人侧向位移在 ±35 mm 以内且俯仰角在±4°之间,可见两种控制方式对侧向偏移和俯仰运动的表现不一致。 通过实验测量可知,机器人采用 walk 步态行走速度为 18. 57 mm/ s,与理论行走速度 20 mm/ s 接近,步态转换后以 trot 步态行走,行走速度为 76. 15 mm/ s,与理 论行走速度 80 mm/ s 接近,少许误差可能是装配和行走过程打滑导致的。 测量其侧向偏移程度可知,其侧向的偏移量左侧在 15 mm 内,右侧在 25 mm 内,其侧向偏移量均在合适的范围内,证明所提算法的有效性。