【作者】 周卫华；

【导师】 郭吉丰；

【作者基本信息】 浙江大学 ， 电气工程， 2013， 博士

【摘要】 全方位移动机器人属于平面三自由度全方位移动系统,具有运动灵活的特点,适合在狭窄的空间内运动。全方位轮是构成移动机器人的关键因素,是主要的运动机构。目前,推广应用较多的全向轮是Mecanum轮,但Mecanum有其自身的缺点,其制作相对困难,运动过程中因接触点轴向移动存在“震动”现象。为此,本文另辟蹊径,采用连续切换全向轮的方案,并提出了一种单排连续切换全向轮的优化结构,研制相应移动机器人,进而研究此类全向轮的各向异性及其对机器人的轮系布局方式、自锁特性的影响,最后分析此类移动机器人的驱动控制特点,并提出优化的控制策略。论文的主要研究内容及其结果如下：1.提出了一种优化的连续切换全向轮结构,分析基于此轮的全方位移动机器人轮系布局问题。首先给出了连续切换全向轮的结构,通过Y型支架连接大小辊子,具有结构简单、安装方便等特点。分析并总结了用连续切换全向轮构成全方位移动机器人的规则和条件,并给出了三轮、四轮以及六轮能实现全方位运动的排布方式。从驱动能力、车体稳定性、系统可控性等角度分析,证明采用四轮的排布方式相对较优。2.介绍了移动机器人电气控制系统的设计与实现。分析对比了现阶段应用在移动机器人的不同控制方法,包括主控器选型、通讯方式、电机驱动器种类等问题。考虑到移动机器人的特点,采用并实现了适合应用在该移动机器人上的电气控制系统,并介绍了主要的软件设计思路。3.分析了连续切换全向轮和基于此的移动机器人运动的各向异性,主要有：(1)分析了移动机器人在驻停时的自锁特性。分析了全向轮运动过程中不同接触点摩擦力的组成形式,并建立斜面的实验系统,实测摩擦系数与地面介质、接触点等的关系,进而给出此全向轮的自锁角(摩擦角),从理论和实验上解决了移动机器人各个运动方向的自锁特性。(2)从运动学方程出发,分析了移动机器人速度的各向相异性。理论计算可得移动机器人的速度朝各个方向运动是不同的,并用ADAMS软件进行仿真,仿真结果与理论计算的结果相吻合。(3)根据非完整系统的劳斯方程,建立了全向轮机器人的动力学方程,理论和实验分析了移动机器人各个方向运动加速度的各向相异性。给出了车体在斜面运动时不发生后翻和侧翻的条件,用ADAMS软件进行仿真验证了模型,为此类系统的设计和控制提供了理论基础。4.针对基于连续切换全向轮移动机器人的特点,提出了优化的控制方法。具体为：(1)分析了四轮驱动移动机器人的冗余特性和驱动特性,在一些特殊方向可采用力矩和速度的双PI控制。四轮驱动的移动机器人是个冗余系统,针对移动机器人运动过程中四个轮子相互挤压(挤压是指电机的作用力对移动机器人运动无实质贡献,只是磨损机器人与轮子的连接部件)的问题,建立了车体速度与电机输出力矩同时控制的PI控制系统,实验结果表明：移动机器人沿正向运动时(正向指速度方向与相邻轮子轴线垂直),效率能提高13%左右,当移动机器人沿斜向运动时(斜向指速度方向与相邻轮子轴线成45°),效率能提高6%左右,同时车体速度的稳定性也得到了相应的提高。(2)从能量最省角度讨论了移动机器人加速过程中力矩分配的问题。从移动机器人动力学方程出发,增加了效率最大化的约束方程。从理论和实验分析可得,相对于其他的控制方法,基于效率最大化的力矩分配方式在移动机器人加速过程中效率能提高2%～3%左右。更多还原

【Abstract】 As a3DOF mobile system, the omni-directional mobile robot is suitable for movement in narrow space with flexible motion characteristic. The omni-directional wheel is the key factor of the mobile robot as the main movement mechanism. Currently, the Mecanum wheel is widely used. But Mecanum wheel has some shortcomings, such as difficult in production, the "shock" phenomenon occurs during the movement due to uncertain axial movement contact points. This article tries to find a way to study another omni-directional wheel—single-row continuous alternate wheel. Considering the current researches of the alternate wheels, the single-row continuous alternate omni-directional wheel and the mobile robot are optimal designed and manufactured. The anisotropy of the wheel and its impact on the layout of the wheels and self-lock characteristics are studied. At last, based on the analysis of such mobile robot drive control features, optimal control strategise are proposed.The main researches and conclusions of this article contain the following aspects:1、This article puts forward the optimal designing of a single-row continuous alternate wheel, and solves the structural problem of the layout of the omni-directional mobile robot. At first, the structure of the wheel is introduced with simple structure and easy installation advantages through the Y-shaped brackets which are made for fixing rollers. Through analyzing and summarizing the rules and conditions of the omni-directional mobile robot, the full range motion arrangements of three wheels, four wheels and six wheels are proposed. Considering the drive capability, body stability and controllability of the system, the arrangement of the four wheels is chosen as the actual bodywork.2、Designing and implementation of the electrical control system are introduced. The analysis and comparison of different control methods in the mobile robot are proposed, including selections of the master controller, means of communication, types of the motor drive. Taking into account the characteristics of the mobile robot, electrical control system which is suitable for the mobile robot and the major software design ideas are described.3、The anisotropy of the mobile robot is analyzed, including the following three main aspects: (1) The self-lock characteristics of the mobile robot is analyzed and solved. Through analyzing the composition of the friction force on different contact points when the wheel moves, the experiment system is established. The relationships between friction coefficient with ground media, contact points are measured by experiments. And the omni-directional wheel self-lock angle (friction angle) is proposed. Self-lock characteristics of the mobile robot on the slope in all directions is solved through theoretical and experimental analysis.(2) The anisotropy of the robot speed is analyzed based on kinematic equation. The speed of the mobile robot in each direction is different through theoretical calculation. Simulation results by ADAMS software and theoretical calculation results are the same.(3) Dynamic equations of the system are obtained according to the nonholonomic system of Rolls equations. The acceleration anisotropy of the mobile robot is obtained in all directions by theoretical and experimental analysis. The rollover and backward conditions of the mobile robot moves on the slope are calculated, and the model is simulated by using ADAMS software. The theoretical basis for system practical application is provided.4, The optimal control method of the mobile robot based on single-row continuous alternate wheel is obtained, mainly including two aspects:(1) A dual PI control of motor torque and speed can be used in special directions by analyzing the four wheels drive mobile robot redundancy features and drive features. The mobile robot consists four wheels is a redundant system. In order to reduce the squeeze between the four wheels (squeeze is a part of the motor force, no contribution to the mobile robot, but harmful to the joint), a dual PI control system includes vehicle speed and motor output torque is established. Experimental results show that when the mobile robot moves along the forward direction (forward direction refers to the direction of the velocity perpendiculars to the axis of the adjacent wheels), the efficiency can be increased by13%. And when the mobile robot moves obliquely (oblique direction means that the angle of velocity and axis of the adjacent wheels is45°), the efficiency can be increased by6%. Meanwhile, the stability of the vehicle speed is also increased.(2) In order to solve moment distribution problem of the mobile robot in the acceleration process, efficiency maximization of the constraint equation is added from the mobile robot dynamics equation. From the theoretical and experimental analysis, related to the other control methods, the efficiency can be increased by2%to3%by using the method of efficiency maximization.更多还原