1、PDF外文：http:/ 中文 5790 字 出处： Electronics, Robotics and Automotive Mechanics Conference, 2009. CERMA'09. IEEE, 2009: 187-192 AxeBot Robot: The Mechanical Design for an Autonomous Omni directional Mobile Robot Tiago P. do Nascimento, Augusto Loureiro da Costa, Cristiane Correa Paim Post-
2、graduation Program in Electrical Engineering Universidade Federal da Bahia Salvador, Bahia, Brasil tiagopnieee.org, augusto.loureiroufba.br, cpaimufba.br Abstract The AxeBot robots mechanical design, a fully autonomous mobile robot, for the RoboCup Small Size League, is presented in this
3、 paper. The AxeBot robot uses three omnidirectional wheels for movement and is equipped by a shooting device for shooting the ball in different directions. Once the AxeBot robot is a fully autonomous mobile robot all the sensors, engines, servos, batteries, and the computer system, must be emb
4、edded on. The project can be separated in four different parts: the chassis design, the wheel design, the shooting device design and the overall assembly which makes a shell design possible to cover the whole robot. The AxeBot mechanical design brings up a new chassis concept for three w
5、heels omnidirectional robot, also present a new shooting device, and finally present AxeBots prototype assembly. 1. Introduction The RoboCup Initiative is an international research group whose aims are to promote the fields of Robotics and Artificial Intelligence. A standa
6、rd challenge, a soccer match performed by autonomous robot teams, was proposed in 1996 1. Initially with three different leagues 2D: Robot Soccer Simulation league, Small Size Robot league, and Middle Size Robot league. Nowadays these leagues have been increased up to: Four-Legged League, Humanoid L
7、eague, Middle Size League, RoboCup Junior Soccer, Small Size League, Soccer Simulation, Standard Robot League. Also, another challenge, the RoboCup Rescue was proposed in 1999 to show that the result from the robot soccer research could be directly applied on a real world problem like a disaster res
8、cue made by robots. Through the integration of technology and advanced computer algorithms, the goal of RoboCup is to build a team of humanoid robots that can beat the current World Cup champions by the year 2050. The AxeBot uses three omnidirectional wheels, positioned on a circle with an ang
9、le of 120o among each wheel, to move in different directions. Three Maxxon A-22 motors are used to drive the omnidirectional wheels, one motor per wheel. These motors are controlled by two Brainstem Moto 1.0 and a cascade controller made to control the robot trajectory 2 3. The AxeBot also hol
10、ds a shooting device to kick the ball in different directions, a Vision System with a CMUCam Plus and GP202 Infra-red sensor 4, a embedded Computer System based on StrongArm, called StarGate Kit and a IEEE 802.11 wireless network card. This work presents the mechanical project to enclose these equip
11、ments into an fully autonomous omnidirectional robot called AxeBot. The complete AxeBot dynamics and kinematics model can be found in 5, this model was used to specify some mechanical parameter, like the wheel diameter. 2. The Chassis The chassis of the robot is the frame to whi
12、ch all other components can be attached, directly or indirectly. Therefore the chassis must be strong enough to carry the weight of all parts when the robot is in rest o in movement. The chassis has to withstand the forces on it, caused by the acceleration of the robot as well. Another important req
13、uirement of the chassis is that it fixes all components in a stiff way, so that there will be small relative displacements of the components within the robot, during acceleration and deceleration. This is particular important for the three driving motors, which are positioned on the ground plane wit
14、h an angle of 120o between each motor. The performance of the control of the robot is dependent on a precise and stiff placement of the motors 6. The chassis has to be strong enough also to withstand a collision of the robot against the wall or against another robot, with the highest possible
15、impact velocity that can occur. Finally the chassis has to be built with the smallest amount of material. At first to reduce the costs, and to minimize the total weight of the robot. Less weight requires less power to accelerate. So with the same motors, less weight gives you more acceleration. This
16、 is of course only true, when all the power generated by the motors can be transferred, via the wheels, to the ground. In other words, the wheels must have enough traction that there will be no slip between the wheels and the ground 7. 2.1. Material Fiberglass was used to build
17、the chassis. This choice is purely financial, because the material is not expensive (although it is strong) and there is no need to hire a professional constructor. The building of all the chassis (six in total) can be done by the team members themselves. Only the moulds have to be built by a profes
18、sional. The upper and lower chassis can be made using one mould that can be adjusted to produce the different chassis. 2.2. Design The primary goal of the design is the fixation of the motors in the desired positions. Therefore a ground plate with 3 slots for the motors is modeled. At t
19、he front side each motor can be attached to the chassis. At the rim of the ground plate an edge is attached to give the chassis more torsion stiffness. This edge can also be used for attaching other components of the robot, like the covering shell. Also there is a cutout to create space for the shoo
20、ting device of the robot. In section 5 the design of this device will be discussed. However no final design will be presented and therefore we stick with this assumption that the shooting device needs these cutouts. All edges are rounded, because this will make the construction of the easier part. T
21、he final part, the lower chassis, is shown in the figure below. This part is modeled in Solid Edge. To get a stiffer and stronger chassis, a second chassis part, the upper chassis, is modeled. This is almost an exact copy of the first part, only now there are 3 cutouts that provide more space
22、for placing the components of the robot. These cutouts also save some material and therefore weight. The both parts are This sandwich construction gives the whole chassis more stiffness, and so the total thickness of both the chassis can probably be lower than using one chassis part. Fi
23、gure 1: Lower chassis Figure 2: Upper and lower chassis attached to each other 2.3. Chassis mould To build these parts, a mould was made. This is just a negative of the actual robot parts. In figure 3 the mould of the upper chassis. To change this mould in the mould f
24、or the lower chassis, where the ground plate does not have holes, the indicated pieces (with white stripes) and the not indicated left piece (symmetric to the most right part) should be lowered 4 mm. For the upper and lower chassis, the basis mould is exactly the same. Only piece one and two are dif
25、ferent for the two chassis, the motor piece and the shooting system piece are the same. Figure 3: Chassis mould 3. Wheels The AxeBot robot is equipped with three wheels positioned on a circle with an angle of 120 among attached to each other as shown in the picture be
26、low.each wheel. These wheels have to enable the omnidirectionality of the AxeBot robot. This means that the wheels have to be able to let the robot make two translational movements (in x and y-direction, see figure 4) without rotating the robot around its z-axis (the axis perpendicular to the y and x-axis, that is rotation in figure 4). The wheels have also to enable a rotation of the total robot around the z-axis.
