考虑足地作用的足式机器人环境表征与路径规划

足式机器人在行走过程中,足端与地面之间的相互作用影响机器人的地面通过情况。足地作用与地表的几何形状和地面的物理特性息息相关,因此仅基于几何特性地图进行路径规划难以满足野外环境下规避松软沙土等非几何危险的需求。针对该问题,考虑足地作用力学提出包含几何与物理特性的环境模型进行足式机器人路径规划。通过简化和统一软硬地面下的足地作用模型,提出表征地面法向松软特性和切向摩擦特性的参数化指标,结合几何特性构建更全面的环境模型。综合考虑影响机器人通过性的地面几何与物理特征,重构路径规划的优化目标,通过图搜索算法实现最优路径规划。以六足机器人Elspider为对象进行仿真和试验,验证了所提出的方法能够有效规避非几何危险,实现了更安全、通过性更强的路径规划。     

考虑轮胎几何与胎压因素的轮地相互作用力模型及其参数辨识

轮地相互作用力对于车辆设计、通过性评价、控制和仿真等方面具有极其重要的作用。传统模型以平板压力为力学假设前提,导致模型中各项参数难以同时响应轮胎几何和胎压因素对轮地相互作用力的影响。采用特定几何和胎压条件下的轮胎弹性形变量建立虚拟刚性轮形,结合轮地接触应力的分布状况,推导一种新的轮地相互力模型。该模型依据轮胎运动状态划分为轮胎准静态压载的垂向载荷模型以及轮胎稳态滑转的牵引力模型,模型中各项参数具有反映轮胎几何、胎压和土壤力学性质之间关联性的特点。通过土槽和原位地面试验对轮地相互作用力模型及其参数辨识结果进行验证,试验结果表明,不同几何尺寸和胎压下的轮胎垂向载荷与试验值之间最大误差不超过0.1 kN,模型参数辨识结果与试验值之间相对误差不超过12%,依据参数辨识结果计算的轮胎牵引力与试验值之间方均根误差为0.37。因而该模型可以有效地应用于考虑轮胎几何和胎压因素的轮地相互作用力学计算中。     

月球车足部构型参数对其驱动性能的影响研究

以二级半转轮腿式月球车为研究对象,考虑月球车在松软月面上的下限问题,在轮腿的跨步杆两端各添加一个"足",并设计出两种月球车轮腿足部构型方案,以增大足部与月壤间的有效接触面积和摩擦力。依据车辆地面力学基本理论,分析月球车的轮腿足瓣与月壤的相互作用力学特性,建立了月球车无轮刺足瓣与月壤的相互作用力学模型,在此基础上,分析了足瓣轮刺效应。提出月球车驱动性能的四个评价指标:足瓣沉陷指标、足部牵引性能指标、驱动电动机性能指标和爬坡性能指标,通过给定月壤特性参数、月球车载荷和滑转率,研究了足瓣的半径、宽度以及轮刺的高度和个数对挂钩牵引力、驱动力矩的影响。Matlab仿真表明,增大足瓣半径、宽度以及轮刺高度和个数均可以提高月球车的驱动性能,与增加足瓣宽度相比,增加足瓣半径效果更好。研究结果为后续的足部机构设计提供了理论参考。     

基于滑转沉陷和轮刺效应的月球车轮地相互作用地面力学及其应用研究

正项目负责人:高海波(E-mail:gaohaibo@buaa.edu.cn)依托单位:哈尔滨工业大学项目批准号:509750591.项目简介月球车轮地相互作用力学是进行月球车设计、动力学仿真、运动控制和月壤力学参数估计的基础,具有重要的理论研究价值和应用前景。目前月球车研究中主要采用传统车辆地面力学理论,不能有效反映车轮的高滑转沉陷和轮刺效应等问题,而且传统地面力学理论对月球车设计、控制、实时仿真和力学参数辨识等方面无法提供可直接借鉴的研究成果。本项目研究了:1月球车轮地相互作用滑转沉陷问题;2轮刺效应、车轮构型及尺寸对轮地相互作用力学的影响;3基于驱动效率     

基于足地接触特性辨识的六足机器人自适应阻抗控制

为提高足式机器人在未知地面环境中运动适应能力,提出了一种基于足地接触特性辨识的模糊自适应阻抗控制算法.首先,针对六足机器人提出一种足地接触特性辨识方法.为降低六足机器人行走时足地之间的冲击力,提出了一种六足机器人沿腿长方向基于足地接触参数的模糊自适应阻抗控制器.基于六足机器人在不平坦地面行走时的足地接触状态,建立机器人步态控制状态机及行走控制框架.通过六足机器人仿真模型,对足地接触特性辨识方法、模糊自适应阻抗控制器以及机器人行走控制框架进行仿真验证,并应用到"青骓"六足机器人样机进行实验验证.     

汽车动力总成刚体惯性参数的辨识

本文以某动力总成为研究对象,基于试验模态分析方法进行了动力总成惯性参数辨识。首先给出了动力总成的频响函数及其拟合方法,并推导了动力总成表面响应和激励与坐标原点之间的关系,建立了动力总成运动学方程,进而得到了刚体惯性参数的表达式;然后以矩阵条件数的方法对动力总成模态试验过程中混入的干扰噪声进行了误差分析;基于测试点的矩阵条件数对响应点的位置进行了推导,并将其表达成与动力总成表面物理参数（如长度、面积等）有关的形式,从而得到了响应点的最好和最差布置形式以及最少的测试点数目;采用捶击法进行了动力总成模态试验,并以最小矩阵条件数原则进行了动力总成惯性参数的辨识。最后,本文也给出了关于进一步消除模态试验测量误差的一些措施。     

四足机器人单腿系统及其跳跃柔顺控制的研究

为了解决四足机器人运动过程中的着地冲击力问题,设计了 一种基于力的阻抗控制的柔顺控制方法.以四足机器人单腿系统的结构为基础,对其进行运动学分析,进一步求解其速度雅克比矩阵和力雅克比矩阵.将单腿系统简化为"质量-弹簧-阻尼"模型,分析研究单腿系统的跳跃运动特性并规划质心运动轨迹.基于阻抗控制的思想,设计了基于力阻抗控制方...     

足式机器人单腿跳跃仿真与实验

针对跳跃运动足地冲击大的特点,基于仿生学设计一种液压驱动四足机器人单腿,分别建立单腿着地相和飞行相的运动学和动力学模型。为了满足单腿跳跃性能要求和减少足地冲击,提出基于三次曲线轨迹跟踪的跳跃方法。使用MSC.ADAMS和Simulink对单腿竖直跳跃过程进行仿真,并搭建了单腿竖直跳跃实验平台和闭环控制系统。     

机器人操作臂动力学参数的动静态辨识方法研究

针对机器人惯性参数辨识的问题,提出了一种机械臂动力学参数的动静态混合辨识方法。在静态辨识中,通过变换机械臂的构型构造多维矩阵,利用机器人基座六维力传感器采集的三维力及力矩值,采用最小二乘法求解机械臂各连杆质量与质心坐标的乘积,为动态辨识过程消去待辨识参数的二次方项,降低辨识的复杂度。利用静态辨识结果,基于牛顿-欧拉算法推导参数解耦形式的机械臂动力学方程。在动态辨识中,规划各关节按照特定的组合方式运动,根据采集的各关节的力矩、速度及加速度值,采用伪逆法辨识各连杆的惯性张量以及质心坐标,继而完成动力学参数的全辨识,算法的参数辨识误差低于0.7%。最后,通过仿真实验验证了该辨识算法的正确性与可行性。     

仿生机器蟹单足惯性参数在线识别神经网络模型

机器人惯性参数识别是机器人精确建模以及机器人控制和仿真的关键问题之一。足端力传感器的接入会影响机器蟹系统的动力学特性,同时力传感器的输出也真实地反映了机器蟹的力作用和机器蟹足端的动力学特性。文中基于足端力传感器的输出信号,对在线识别仿生机器蟹单足末端惯性参数进行了分析和研究,并建立了惯性参数在线识别的神经网络模型,网络学习后其权值即为辨识的惯性参数。     

足式机器人的稳定行走*

足式机器人在行走过程中,足端与地面之间的法向冲击力将影响机器人的在垂直方向上的稳定性。被动柔顺可以减小垂直冲击力但同时可引发平台持续震荡。针对该问题,设计基于足端力反馈的主动柔顺控制器,分析其对机器人垂直稳定性的影响。机器人由于机械间隙、步态、路面等因素将出现足端打滑现象,导致机器人水平方向失稳。引入摆腿回缩技术,分析摆腿回缩对机器人水平稳定性能的影响。仿真和液压足式机器人行走试验验证提出方法的有效性,提高了机器人行走过程中的垂直和水平方向稳定性。     

Method for six-legged robot stepping on obstacles by indirect force estimation

Adaptive gaits for legged robots often requires force sensors installed on foot-tips, however impact, temperature or humidity can affect or even damage those sensors. Efforts have been made to realize indirect force estimation on the legged robots using leg structures based on planar mechanisms. Robot Octopus III is a six-legged robot using spatial parallel mechanism(UP-2UPS) legs. This paper proposed a novel method to realize indirect force estimation on walking robot based on a spatial parallel mechanism. The direct kinematics model and the inverse kinematics model are established. The force Jacobian matrix is derived based on the kinematics model. Thus, the indirect force estimation model is established. Then, the relation between the output torques of the three motors installed on one leg to the external force exerted on the foot tip is described. Furthermore, an adaptive tripod static gait is designed. The robot alters its leg trajectory to step on obstacles by using the proposed adaptive gait. Both the indirect force estimation model and the adaptive gait are implemented and optimized in a real time control system. An experiment is carried out to validate the indirect force estimation model. The adaptive gait is tested in another experiment. Experiment results show that the robot can successfully step on a 0.2 m-high obstacle. This paper proposes a novel method to overcome obstacles for the six-legged robot using spatial parallel mechanism legs and to avoid installing the electric force sensors in harsh environment of the robot’s foot tips.     

沙地环境下椭圆型腿运动特性实验研究

对移动机器人来说,适应复杂环境是相当重要的.椭圆型腿结合了轮式和腿式的优点,具有椭圆型腿的移动机器人在地面运动中有很好的运动性能,但椭圆型腿与地面的动力学还没有深入的研究,尤其是椭圆型腿在松软沙地介质的通过性.主要介绍椭圆型腿在沙地介质中运动性能的研究实验平台的设计,同时对其运动性能进行分析.通过对移动平台重心起伏、周期步长、前进速度和推进效率的分析,为椭圆型腿的优化提供实验依据.椭圆腿的足地实验对椭圆型腿的优化设计和移动机器人的控制有重要意义.     

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.     

并联六轮腿机器人机身平稳性控制方法研究

轮腿式机器人在非结构化路面运动时,机身平稳性控制对于提高运动平稳性、降低系统能耗、提高定位与建图精度等具有重要意义。针对并联式六轮腿机器人在通过不规则地形时足端悬空、姿态倾斜、机身晃动等问题,提出一种融合足端力控制器、姿态控制器及重心高度控制器的机身平稳性控制框架。其中,足端力控制器通过阻抗控制算法抑制机器人足端受力因地形变化带来的突变扰动;机身姿态控制器对机身倾斜角进行解耦,并控制各腿的长度补偿机身的偏移量;重心高度控制器根据各腿的伸长量自适应地调节机身高度,保证腿部执行机构具有足够的运动空间。针对三种控制器相互耦合、对外部扰动抑制效果不佳等问题,利用串级控制的思想将三种控制目标统一为力跟踪控制,降低机身振荡的风险。在并联式六轮腿机器人上进行了实验验证,结果表明所提出的控制算法框架能有效抑制外部地形扰动,当机器人以大约0.6 m/s的速度前进时,机身的俯仰角及横滚角保持在-0.7°~0.7°范围内,足端接触力维持在期望力附近,且机身重心高度随地面起伏自适应地调整,确保了机器人的运动平稳性。     

Computer-aided geometric design of legs for a walking vehicle

A legged vehicle is potentially more energy efficient and mobile than conventional vehicles in rough terrain. The performance of such a legged vehicle is strongly dependent on the leg geometry. In general, a leg linkage which possesses three-degree-of-freedom foot motion is adequate. A preliminary design of the leg with a view to good energy efficiency resulted in a four-bar leg. This was described by S. M. Song et al. [Mech. Mach. Theory 19, 17–24 (1984)]. In the present paper, the mobility of the legged vehicle is brought into consideration in the leg design. A study of the mobility of a six-legged vehicle shows that a large walking envelope is required for each leg linkage. In order to satisfy this requirement, the original four-bar leg was modified into a seven-bar leg by mounting another four-bar linkage on the coupler of the original four-bar linkage. Also, a different type of leg linkage based on pantograph mechanism was designed. A comparison of the leg performance of both types of leg is made in this paper and the pantograph leg is found to be more effective.     

Development and evaluation of a compact 6-axis force/moment sensor with a serial structure for the humanoid robot foot

In order to walk safely, forces and moments exerted on humanoid robot foot should be measured and used for controlling the robot. This paper describes the development and evaluation of a six-axis force/moment sensor used under humanoid robot foot. The developed sensor is capable of measuring 400 N horizontal force, 1000 N vertical force, 20 N·m moment about the horizontal axis and 10 N·m moment about the vertical axis using rectangular cross-sectional beams. The structure of the sensor is newly modeled, and the sensing elements are simulated by using finite element method (FEM). Then the sensor is fabricated by attaching strain gages onto the beams. Finally, a characteristic test of the developed sensor is carried out, and the output from FEM analysis agrees with those from the characteristic test.     

Analysis on the performance of the SLIP runner with nonlinear spring leg

The spring-loaded inverted pendulum(SLIP) has been widely studied in both animals and robots.Generally,the majority of the relevant theoretical studies deal with elastic leg,the linear leg length-force relationship of which is obviously conflict with the biological observations.A planar spring-mass model with a nonlinear spring leg is presented to explore the intrinsic mechanism of legged locomotion with elastic component.The leg model is formulated via decoupling the stiffness coefficient and exponent of the leg compression in order that the unified stiffness can be scaled as convex,concave as well as linear profile.The apex return map of the SLIP runner is established to investigate dynamical behavior of the fixed point.The basin of attraction and Floquet Multiplier are introduced to evaluate the self-stability and initial state sensitivity of the SLIP model with different stiffness profiles.The numerical results show that larger stiffness exponent can increase top speed of stable running and also can enlarge the size of attraction domain of the fixed point.In addition,the parameter variation is conducted to detect the effect of parameter dependency,and demonstrates that on the fixed energy level and stiffness profile,the faster running speed with larger convergence rate of the stable fixed point under small local perturbation can be achieved via decreasing the angle of attack and increasing the stiffness coefficient.The perturbation recovery test is implemented to judge the ability of the model resisting large external disturbance.The result shows that the convex stiffness performs best in enhancing the robustness of SLIP runner negotiating irregular terrain.This research sheds light on the running performance of the SLIP runner with nonlinear leg spring from a theoretical perspective,and also guides the design and control of the bio-inspired legged robot.