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摘 要

随着计算机技术和智能技术的飞速发展，移动机器人已经应用于各种领域，以帮助人类完成各种工作。 基于此实现自主移动机器人的动态感知，外部环境的实时定位和导航是重要的保证，具有重要的研究意义。 本课题以四台Mecanum轮式全向移动机器人为研究对象，对基于ROS的定位导航系统进行了分析与设计。

完成全方位移动机器人平台的系统建设和程序调试。 走廊和室内环境的全向移动功能，位置和地图构建功能。

关键词：机器人操作系统（ROS） , 全向移动机器人，麦克纳姆伦，

Design and Research of Omnidirectional Mobile Robot System Based on Robot Operation System (ROS)

ABSTRACT

With the rapid development of computer technology and intelligent technology, mobile robots have been applied to a variety of fields to help humans complete all kinds of work. It is an important guarantee for autonomous mobile robot to realize dynamic perception and real-time positioning of external environment and navigation based on it, which has important research significance. In this subject, the four Mecanum wheeled omnidirectional mobile robot is taken as the research object, and the positioning and navigation system based on ROS is analyzed and designed.

Finish the system construction and program debugging of omnidirectional mobile robot platform. The omnidirectional mobile function, location and map building ability in corridor and indoor environment.

Keywords: Robot Operation System (ROS), omnidirectional mobile robot, Mecanum wheel

Contents

摘要 I

ABSTRACT II

CHAPTER I INTRODUCTION OF OMNIDIRECTIONAL MOBILITY 1

1.1 Introduction 1

1.2 Literature Review 1

1.3 Omnidirectional mobility 3

1.4 Conventional wheel designs 5

1.5 Special wheel designs 6

1.6 Mecanum wheel design 8

CHAPTER II KINEMATICS amp; CONTROL LAWS 11

CHAPTER III TRAJECTORY PROFILES 15

3.1 Position and velocity control 15

3.2 Discrete implementation 16

3.3 Performance indicators 17

3.4 All-round and precise controller 18

CHAPTER IV SIMULATION AND EXPERIMENTAL RESULTS 20

CHAPTER V CONCLUSIONS 26

REFERENCES 27

ACKNOWLEDGEMENTS 29

CHAPTER I INTRODUCTION OF OMNIDIRECTIONAL MOBILITY

1.1 Introduction

Both Industrial and technical adaptation as well as applications of cellular robots are getting increasingly important. they need often been used for monitoring, inspection and transportation tasks. Another emerging market is mobile entertainment robots. one among the most requirements of an autonomous cellular robot is its ability to maneuver round the OR, avoiding obstacles and finding its thanks to subsequent place to try to to its work, a skill referred to as location and navigation. to understand where to travel, the robot must know the present location precisely. this suggests that an outsized number of sensors, external references and algorithms must be used. to maneuver in narrow areas and avoid obstacles, cellular robots must have good mobility and maneuverability. This skill mainly depends on the development of the wheel. during this field, research is being conducted to enhance the autonomous navigation capabilities of cellular robot systems. This chapter introduces universal cellular robots for educational purposes. because of Mecanum's special wheels, this robot has wide movement options. This chapter contains some information about conventional and special wheel construction, aspects of mechanical construction of Mecanum wheels also as about robots, kinematic models, and electronic and control strategies: remote, line tracking, autonomous strategies. due to its ability to maneuver and its various control options, the robot described during this chapter are often used as a beautiful learning platform. This report is that the results of research conducted within the robotics laboratory of the school of engineering "Gh. Asachi” Iasi University of Technology, Romania.

1.2 Literature Review

Previous work There are two types of multi-direction wheel platforms: one type uses special wheels and the other because it includes conventional wheels. Special machines that are mainly tested on multipurpose cellular platforms have active tracking instructions and passive instructions. Conventional wheels are often divided into two types, wheels and steering wheels. The Mecanum Wheel was discovered in 1973 by a Swedish engineer (Mecanum Company) named Ilon (Ilon, 1975). Therefore, called Mecanum or Swedish wheels. The use of these four wheels ensures the movement of one-way vehicles without conventional steering systems (Muir amp; Neumann, 1990; Dickerson amp; Lapin, 1991). Braunl, 1999). The main robot moves with Mecanum wheels (called "Uranus"), which are very similar to our vehicles, designed and built at Carnegie Mellon University (Muir amp; Neuman, 1987a and 1987b), see Fig. 1-1. There is no suspension, what is important if the floor is not completely flat. The advantages of Mecanum wheeled vehicles compared to the steering wheel (Dickerson amp; Lapin, 1991). (Muir amp; Neuman, 1987a and 1987b) introduced a kinematic model and developed an algorithmic Uranus feedback control program consisting of 4 Mecanum wheels that are identical to our platform except for suspension. There are several alternatives to Mecanum four-wheel drive are bestowed by (Diegel et al., 2002; Arthur Koestler amp; Braunl, 2004; Siegwart amp; Nourbakash, 2004;Efendi et al., 2006; etc.). Mecanum wheeled cars have several drawbacks. consistent with (Nagatani et al., 2000), Mecanum wheeled vehicles tend to slide, and consequently lateral mileage differs from longitudinal mileage with identical wheel rotation. additionally, the ratio of longitudinal routes to transversal routes changes with soil conditions with an equivalent wheel rotation. The second disadvantage is that the purpose of contact move between the wheels and therefore the ground parallel to the axle, albeit the bicycle is usually in touch with the bottom. Lateral movements create horizontal vibrations. the ultimate disadvantage is its ability to beat obstacles can't be separated from the direction of travel. Wheel skid prevents the foremost popular method for replacing the dead using shaft encoders (Everett, 1995 and Borenstein et al., 1996) to figure well on Mecanum wheeled vehicles. to beat this problem, visual readings of the dead are used as non-slip sensors (Giachetti et al., 1998 and Nagatani et al., 2000). this system, which is additionally utilized in optical mice, uses an integrated video camera that continuously records footage from the bottom floor and image processing hardware on the robot, thus determining the speed and direction during which the present image has moved relative to the previous image's speed and direction of the point of reference this. in theory, our approach is analogous to the ideas mentioned above. However, we do not just believe visual positioning information, we use this information to take care of the odometrical system.

Figure 1-1. Uranus omnidirectional mobile robot

1.3 Omnidirectional mobility

The omnidirectional term is employed to explain the power of a system to maneuver instantaneously in any direction from any configuration. Robotic vehicles are often designed for flat traffic. They work on warehouse floors, roads, lakes, tables, etc. In two-dimensional space, the body has three degrees of freedom. It can shift in two directions and rotate round the center of gravity. However, most conventional vehicles cannot control every level of freedom independently. Conventional wheels cannot move parallel to the axle. These so-called support wheels, which aren't of an equivalent name, prevent the vehicle from employing a sliding steering almost like a car perpendicular to the direction of travel. Although it can usually reach any location and orientation in 2D space, this will require complicated maneuvers and road planning (Fig. 1-2). this is often the case for manned vehicles and robots.

Figure 1-2: lateral parking of a differential driver model robot

If the vehicle doesn't have a limitation not an equivalent name, he can drive altogether directions altogether directions. This ability is usually referred to as omnidirectional mobility. Multidirectional vehicles have the good advantage of driving in confined spaces on conventional (non-homonymous) platforms with an Ackerman steering system like a car or differential drive system (Bornstein et al., 1996). you'll work sideways, activate the location, and follow complicated paths. These robots can easily perform tasks in environments with static and dynamic barriers and narrow pathways. Such environments are usually found in workshops, warehouses, hospitals, et al. Flexible operation and movement of materials with real-time control became an integral a part of modern production. Automated controlled vehicles (AGVs) are often utilized in flexible manufacturing systems to maneuver spare parts and guide them as required. Conversely, non-homonym robots can move in several directions (back and forth) and draw multiple curved trajectories, but cannot work sideways. For parallel parking, robots that are moved differently must perform a series of maneuvers, for instance (see Figure 1-3). Robot cars can't even spin. Figure 1-3 illustrates this. Shaded circles on the proper and left of the vehicle can't be accessed to the Ackerman platform thanks to a system that determines the minimum turning radius. the event of multipurpose vehicles continues to demonstrate the effectiveness of this sort of architecture and adds floor platforms to vehicles that have exceptional maneuverability. Multi-directional vehicles are divided into two categories which describe the sort of wheel placement they use for mobility: conventional wheel designs and special wheel designs. Within the introduction to the present report, it's stated that the cellular robot from which the movement must be controlled allows for broad mobility. To better understand this concept, we are now discussing.

Figure 1-3 mobility of a car-like mobile robot.

Robotic vehicles are often designed for even traffic. Some examples are cleaning floors or transporting goods to warehouses. In two-dimensional (2D) space, the body has three degrees of freedom (3 DOF). It often moves along the x and y axes and rotates around the center of gravity of the θ axis (Figure 3.1). Most robotic cars cannot control these three degrees of freedom despite non-holonomic limitations. For example, imagine a road with several cars parked on the side of the road. If the movers usually want to park their car outside between two cars, they can't just drive sideways. Often, the driving force must push and pull several times to form enough angles to drive the car into empty space and reach a satisfactory final level (see Figure 1-4). this is often thanks to the lack of the car to use the sliding steering to maneuver perpendicular to the direction of travel: non-holonomic limitations. Albeit such vehicles can by and large arrive at any area and direction in 2D space, complex moves and street arranging might be required, whether or not they are human or automated fueled vehicles.

Figure 1-4 3 DOF

1.4 Conventional wheel designs

The ordinary wheel configuration utilized for portable robots with omnidirectional abilities can be partitioned into two kinds, the haggles controlling wheel. They have more prominent stacking limit and more noteworthy capacity to bear lopsided ground contrasted with extraordinary wheel designs. Notwithstanding, due to their non-holonomic nature, they are not genuine omnidirectional wheels. This design isn't truly directed, because there's a limited amount of your time, when observing continuous turns, before the steering motor can realign the wheel to regulate it to the anticipated curve (Dubowski et al., 2000). The time constant of this process is accepted far faster than the rough dynamics of the vehicle for many applications. it's therefore considered to be ready to trace the trail with zero radius and make the term everywhere. Most platforms, which include conventional wheels and average direction alignment, include a minimum of two wheels that are driven independently and driven independently (Borenstein et al., 1996). The roller wheels are active just like the one in Fig. 1-5 or a standard wheel (Fig. 1-6) are often accustomed achieve this closeness with directional play.

Figure 1-5 Active castor wheel

Figure 1-6 starred wheel (a) powered steering wheel (b) lateral offset.

1.5 Special wheel designs

The special wheel design is predicated on concepts that activate traction in one direction and allows passive movement within the other direction, which allows greater flexibility an overloaded environment (Yu et al., 2000). The special wheel design is predicated on concepts that activate traction in one direction and allows passive movement within the other direction, which allows greater flexibility an overloaded environment (Yu et al., 2000). This design can include universal wheels, Mecanum wheels (Sweden) and wheel ball mechanisms. Universal wheels (Fig. 1-7) offer a mixture of limited and unlimited movements during rotation. This mechanism consists of a little roller that's arranged round the outside diameter of the wheel to make sure normal wheel rotation, but remains roll freely within the direction parallel to the axle. The wheel is in a position to perform this action because the rollers are mounted perpendicular to the axis of rotation wheels. When two or more of those wheels are mounted on the vehicle platform, their combined limited and unlimited movement allows continuous mobility.

Figure 1-7 universal wheel (a)simple (b) double (c) alternative

Mecanum wheels (Sweden) have a design almost like universal wheels, except that the roller is mounted at an angle, as shown in Fig 1-8. This configuration moves part the force within the direction of rotation of the wheel to the force that perpendicular to the direction of the wheel. Platform configuration consists of 4 wheels, arranged almost like a car. Power is due the direction and speed of every of the four wheels are often added to the overall force vector, which allows the vehicle to be moved altogether directions. Another special design of the wheel is that the ball ball mechanism. It uses a lively ring, which supported by a motor and gearbox, to transmit power through winding and friction to a ball which will directly spin in any direction. Each of those special wheel designs produces excellent maneuverability, but is restricted to hard and flat Surface because it's smaller diameter of the roller. A general description from nature some of these designs is given in Table 1.

Table 1:Properties of wheel designs

Figure 1-8 Mecanum wheel

1.6 Mecanum wheel design

One of the foremost common wheel designs is that the Mechanum wheel, discovered in 1973 by Beng Ilon, an engineer from the Swedish company Mecanum AB (Ilon, 1975). The wheel itself consists of hub 1, which carries several rollers 2 which will move freely at an angle of 45 ° round the perimeter of the hub (Figure 1-9). Because in Fig. 6 is harder to supply, simpler wheel hubs are chosen (Fig. 1-10). The angle between the roller axes and therefore the center wheel axis is often of any value, but 45 ° for conventional Swedish wheels. Angular circular rollers change a part of the force with the direction of rotation of the wheel into a force that perpendicular to the direction of the wheel. Counting on each direction and speed of the wheel, the mixture resulting from all of those forces creates a complete force vector within the desired direction, Let the platform move freely within the direction of the force vector produced without changing itself.

Figure 1-9 Basis components of mecanum wheel

Figure 1-10 Mecamum wheel (a) front (b) explode view

The rollers are shaped so that the wheel silhouette is one-way round (Fig. 10.a). We can get the roller shape if we hold the cylinder with outer diameter of the wheel through the plane at an angle (the angle between the roller axis and the hub), in our case γ = $ 45 (Fig. 11). This shape should respect the equation

(1.1)

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