【作者】 张立杰；

【导师】 潘存云；

【作者基本信息】 国防科学技术大学 ， 机械工程， 2008， 博士

【摘要】 移动机器人已经广泛应用于侦查、营救、排爆、探测、采矿、娱乐、竞技等诸多行业,在军事、安全、生产、生活以及科学研究中扮演着越来越重要角色。随着移动机器人应用领域的不断拓展,对移动性能的要求不断提高,各种混合式移动机构相继问世。轮-腿混合式移动机构继承了轮式和腿式移动的优点,既能够保持较高的移动效率,又具有良好的通过性能,是传统混合式移动机构中研究较多的一种,已经取得了大量研究成果。但是,分析现有轮-腿混合式移动机构,其结构仍然存在一些值得改进和完善的不足之处,例如为实现既定功能而增加的附加装置、驱动器配置方式、特定运动模式下的机构冗余等,这些问题的存在不但增加了结构设计难度,往往还会对机构动态性能造成一定影响,给控制系统设计带来一定困难。本文提出一种新型复合式仿生轮-腿机构,它独特的结构特征和运动实现原理明显不同于现有轮-腿混合式移动机构,避免和纠正了上述轮-腿混合式移动机构中的不足之处,对这种新型机构进行深入研究对于高性能移动平台的开发具有一定的参考价值。围绕本文提出的新型复合式仿生轮-腿机构,开展了一系列的研究工作:对所提出的轮-腿机构进行了结构和功能实现原理分析,并针对混合式轮-腿机构的不足,总结归纳了其结构特点。轮-腿机构具有全新的结构特点和运动实现方式,论文从其形成原理入手,从具有相似功能的常见机构的结构特点出发,分析了它的结构特征及轮、腿、轮-腿复合三种运动功能的实现过程,概括了其有别于混合式轮-腿机构的结构特点。对仿生关节机构传动过程中接触力的时变特征进行了深入研究,得到了时变刚度系数曲线。仿生关节是轮-腿机构的主要结构和功能单元,受结构影响,关节传动过程中轮齿间接触力具有时变特征。论文利用微分几何相关方法和定理,分析了齿面的曲面特征,研究了单、双齿啮合区间变化规律,建立了反向啮合点位置求解方程,基于Hertz静力接触理论得到了接触刚度系数的变化曲线,为机构的动力学研究奠定基础。对所提出的轮-腿机构进行了运动学分析,给出了运动学正解和逆解方程。在运动学分析中,定义了用于准确描述机构运动状态的三个关键参数和用于运动分析的一个重要平面,即方位角、偏转角、偏转轴和偏摆平面,灵活运用连续变换的余弦变换矩阵和一次有限转动的欧拉定理,充分利用机构的结构特点,建立了机构在不同运动方式下的运动模型。将牛顿-欧拉法应用到轮-腿机构动力学分析当中,建立了机构的动力学模型。文中对车轮和地面之间的作用力对轮-腿机构的作用效果进行了分析,对仿生关节传动过程中接触力及其力臂的表达式进行了推导,对构件的运动姿态和惯性力、惯性力矩进行了求解,分别应用牛顿和欧拉定理建立了构件的平衡方程。最后,为满足实际需要,还研究了由模型计算所得驱动力向惯性系转换方法。进行了轮-腿机构的运动学和动力学虚拟样机试验,对机构功能实现的可行性进行检验和评估,并将试验结果与理论模型仿真结果进行对比,从而对模型描述机构运动和动力特征的可信度做出判断。论文研究了虚拟样机技术在轮-腿机构上的应用,并对试验内容、方法和过程进行了详细介绍。文中以样条曲线作为IMPACT函数的关键参数定义了虚拟样机中接触碰撞的力学行为,对关键构件的运动参数和受力状况进行了分析,对接触力的变化规律进行了观测,结果表明轮-腿机构能够实现既定功能。通过将试验数据与理论计算结果比较可以发现两者误差很小,说明本文所建立模型能够真实反映机构的运动特性。设计了轮-腿机构和多运动态轮-腿移动平台物理样机,初步运动学试验表明轮-腿机构完全能够实现设计运动形式,基于该机构的移动平台能够实现直行、斜行、原地转弯、跨步、小半径转弯等多种移动姿态,具有较好的移动性能和环境适应能力。更多还原

【Abstract】 Mobile robots are being used widely in such diverse applications as reconnaissance operations, rescue operations, exploder removing, planetary explorations, mining, entertainment industries, sports competition etc., and play more and more important roles in military mission, safety guard, manufacturing, daily life of human beings and scientific research, and so on. Along with the environments becoming more and more complex, the locomotion ability must be improved so as to make mobile robots have the adaptability to maneuver on different types of terrains. As a result, tremendous hybrid locomotion systems have been presented in the past decades. Wheelled-legged hybrid locomotion mechanism inherits the merits of both legged mechanism and wheeled mechanism, and can move with excellent locomotive efficiency, while maintaining excellent locomotion performance. Consequently, more attention is focus on it, and large amounts of achievements with versatile structural forms have been come up with. However, there are still few structural hurdles in them, and need to be improved or overcomed, such as the switching system whose function is to alter the locomotion mode according to different terrains, the arrangement of the actuator which is usually mounted on every joint and drive it directly, the phenomena of redundant mechanism in special locomotion mode, and so on. All of these not only increase the difficulty in structural design, but also give rise to a higher possibility of making the dynamical performance of the hybrid locomotion mechanism worse. In this work, a novel bionic wheelled-Legged-fused mechanism is presented, which is distinctly different in structure and principle of realizing the locomotion modes, and eliminats or corrects the shortcomings in traditional hybrid locomotion mechanisms mentioned above. An in-depth study on this new mechanism is useful for the development of high performance locomotion mechanism.A series of researches are carried out on it as follows:The structural principle and the locomotion capabilities of the bionic wheelled-legged-fused mechanism are introduced. Also, its structural characteristics are summarized in accord with the shortcomings existing in the wheelled-legged hybrid locomotion mechanisms. The wheelled-Legged-fused mobile mechanism has an innovative structure and can execute legged-mode, wheelled-mode, and wheelled-legged mode according to the environment. Based on several conventional mechanisms with similar function to the new mechanism, the paper presents its forming principle, the structural characteristics and the principle of realizing the three locomotion modes, and summarizes them as a conclusion.The time-variable characteristics of the meshing force in the bionic joint transmission are studied, and the time-variable-meshing-stiffness coefficient curves are obtained. The bionic joint is the main component of the new mechanism not only in structure but in function. Affected by the structural features of the joint, the meshing force in the bionic joint transmission shows time-variable characteristics. Based on the essential principle of differential geometry, the characteristics of the working flanks of the involute ring tooth are analyzed. The variety between single-tooth-meshing-span and two-teeth-meshing-span alternatively in transmission is studied. The equations to solve the position of the inverse meshing point are deduced. And then, based on the Hertz elastic contact theory, the formula for the calculation of the meshing-stiffness is given and the time-variable-meshing-stiffness coefficient curves are drawn, which is essential in dynamics.The related kinematics analysis for the new mechanism is accomplished, and the forward kinematics and inverse kinematics equations are derived. In kinematics analysis, three key parameters and an important plane are defined. The three parameters, named azimuth angle, deflection angle and deflection axis, respectively, are used to describe the spatial orientation of the new mechanism, while the plane, called deflection plane, is used to analyze the instantaneous configuration of the mechanism at anytime of the whole process. Then, combining the sequential cosines transformation matrix with the Euler’s theorem on rotation, the kinematics models are derived correspond to three types of locomotion modes.The dynamics model of the wheelled-legged-fused mechanism is set up using the Newton-Euler formulation. In this section, the interaction between ground and the wheel mounted on the output shaft of the new mechanism is analyzed firstly. Then, the expression for determined the meshing force vector and the arm of the meshing force vector is derived. After the inertia force and inertia moment of each component are calculated, the equilibrium equations for each body are written based on the Newton-Euler formulation. In order to meet the practical requirement, the transformation method of the actuating force from reference frame to gravity frame is presented in the last.The virtual prototype of the new mechanism is established, and the feasibility for the new mechanism to realize the design functions is examined and evaluated based on it. Also, the experimental results are employed to determine the reliability of the kinematics and dynamics models, by comparing them with the calculations of the models. In this process, the application of the virtual prototype in the wheel-leg-fused mechanism is introduced in details. A spline curve is used to define the contact force in establishing the virtual prototype, which is a key parameter in impact-function-based contact force calculations in ADAMS. In the experiments, emphasis is focus on the motion state of several important components, and load state of them is analyzed, especially, the contact forces from the gear pairs are measured. All of the experimental results demonstrate that the new mechanism can meet the design requirement and have the capability of executing the wheelled-mode, legged-mode and wheelled-legged mode. Results of the comparison drawn between the experimental results and the calculations of the kinematics and dynamics models validate the reliability of the models.A physical prototype of the new mechanism is established, and meanwhile, a quadruped vehicle based on it is assembled. Results from a preliminary kinematics test based on them verifies that the mechanism design meet its requirements for traversing with the wheelled-mode, legged-mode and wheelled-legged mode, and the vehicle can realize multi-locomotion-configurations, such as straight movement, side movement, turning in place, walking, and turning in small radius, and so on. which make the vehicle have a strong locomotion performance and a better adaptability on extreme environments.更多还原