Analysis and design of microsoccer robot

Journal of Harbin Insitute of Technology (New Series), Vol.9, No.3, 2002Analysis and design of microsoccer robotZHANG Zhi-chao, ZHAO Chen, DING Feng, WU Lian-xi张智超，赵臣，丁凤,昊连熙( School of Mechanical Engineeing, Tianjin University , Tianjin 300072, China)Abstract: Frum the analysis of mirosot robot soccer, the design of the robot is discussed in detail covering thebasic ideas of design, the general design procedure, main calculations, and the cinematic model of robot, elc.Key words: multiagent robot soccer; analysis; designCLC number: TP242.6 Docunent code: AArticle ID: 1005-9113(2002)03-0318-050 INTRODUCTION3) Movement control ability. In order to accom-Robot soccer is a new kind of intemational high- plish the match silly，a socer robot should be abletech competition developed rapidly in recent years. Asto accurately implement varieties of movements , simplea marking and challenging subject of AI and Robotics，or complex.it not only provides an ideal lest-bed for the research of4) Collision-avoiding ability. As the whole robothigh technologies such 8 muli-agent cooperation, butsystem works in definite rhythm, the robot would not ,also presents a new type of competition item with highexcept taking other measures , change its movement be-interests and intelligence.fore receiving the next movement command. This inher-At present robot soccer is organized independentlyent defect may easily lead to cllision during the matchby two organisms -The International Al Intitute and The especially when the robol moves at high speed or isFederation of Intermational Robol-soccer Association.closed 10 others. Though we can decrees this kind ofThe former presents such competition items as the Sim-collision by better progranning σr by increasing thulation League, the Small-Size League (F-180), thecalculation speed of the computer, it should take otherMiddle-Size League (F2000) and SONY Leagued Ro- measures in order to avoid absolutely the cllision.bot League. The main competition items organized by :Above analyses mean that the key of the design ofFIRA are NAROSOT， MIROSOT， ROBOSOT， S-mirosot robot lies on the process of the data from theKheperasot and Benchmark.host computer and on the realizing of the desired move-Soccer robots are also divided into two kinds: vi- ment. Though the robot works in the same way as wire-sion-based system and robot-based system.less remole controlled vehicle, its intelligence is muchSoccer robot represented by AIBO and P3 has now higher than the ltter. Since it is the robot that is thereached a considerable high level.executor of the match, and its quality may influenceThis paper deals mainly with the design of mirosot deeply the result, it can be said that the robol be thesoccer robot. Lack of industrial support less work is key of the manufacture of the whole robol soccer sys-done in the development of high quality soccer robot,1 ANALYSIS OF MIROSOT SOCCER2 BASIC IDEAS ABOUT THE DESIGNIn order to meet the need of competition, a mirosotAccording to above analysis， a mirosot robotrobot should at least possess following functions:should have at least five parts to complete the match:1) Wireless conmunication ability. The trobut the wireless communication module , the motion control-should be able to rereive the movement commands sentling module , the driving module, the power system andby the communication subsystem.the robot body. The ollision-avoiding subsystem may2) Conmand process ability. As all three robols be added according to the need.are controlled by one single host computer during theThe prininle. mnle nf the. rmnhrut being to completemaltch and each robot moves at different speed, the ro-the d中国煤化Ins also from thebot should possess the ability to process a set of com- design:fYHCNMHGermination of theReceived 2001 -11 -02..318●Journal of Harbin Institute of Technology (New Series), Vol. 9, No.3, 2002paraneters of motion， the selection of the mode ofate. In order to determine reasonably the pararneltersmovement, the selection of the mode of driving, andof notion of the robot, it should well analyze the rela-the calculation of transmission system, etc. The detailtions between three parts of the mirosot soccer systemwill be discussed laler.and fully consider the capability and cost of the wholeAfter above design the motion control module cancompetition system.be then developed. In order to receive and process theAt last, the robot to design must have a good inte-wireless data and control the motion correctly, an em-gral capacity. In the match the robot moves and stopsbedded computer system is generally implanted in thefrequently and should realize different mode of mo~robot. In fact all modules in the robot are organized a-tions. It should demand of course that the robot as around the micro controller. The design includes follow-whole possess some satisfying characteristics. For ex-ing works: the selection of micro contoller, the designample, the barycenter of the robot should be enoughof communication module, the design of control cirlow; it should also be near the driving axis of the ro-cuit, and the programming of communication and con-bot, etc. Some measures must be taken after the deepanalysis.The basie role of the robot body is to bear and in-Considered that the vision system, the decisionstall all modules in it and to decrees the influence ofsystem and the communication system are often updatedcollision with other robols. The design is therefore howspeedily but the robol will be improved slowly, someto meet these requirements.indexes such as the maximum speed of the robot mayIn order to be convenienl for manufacturing, ma-oflen be decided a bit higher than the actual need inintenance and improvememt in the future, it would beorder to meel the changes.belter that the robol be modularized. Moreover, as theIn conclusion, the robot to design must satisfy fol-size of the robot is limited, each part in the robotlowing requirements : the parameters be reasonable andshould be as diminutive as possible. Using specifieadvanced ; the commands be received and treated cor-chips is a good solution to minimize the size of the con-reetly; the arangement be rational; and the movementtrol board.be smart and accurale. Naturally, the mbot should alsoThe wireless communication module, the motionbe easily produced.controlling module, the driving module, and the powerThe design of the robot being complex, it needssystem being all assembled in the body of the robol,oflen pass several times to finish the work.they should be arranged reasonably. In addition, it isbetter that all modules in the robot be fixed firmly in3 DESIGN AND CALCULATION OF MIROSOTorder to decrees the influence of collision.ROBOTSince all of the. modules in the robot are motorizedby the power system, the power system should naturally3.1 Design of the Motionbe efficient and universal. Chargeable battcry is a goodThe robot performing the match on the plane ofchoice. It demands also that all subsystems be energythe table, the ideal case is that the robot has three de-saving in order for the robot to complele the match.grees of freedorm: two lranslations and one rolation.DC molor is often used to drive the robol. It has aThe possible mode of motion includes three types:wide range of speed and the control circuit is not So-womm lype, wheeled type, and caterpillar type. Con-phisticaled. More important is that DC motor can besidered thal the obot needs move at a high speed andpowered by chargeable battery.changes the diretion frequently, the wheeled lype isDuring the design of the robot ，the relationsoften chosen. There are three cases as shown in Fig. 1.lween the robot and other systems must be considered.Among them the bi-wheel type is often selected.We know from above analysis that a robot soccer systemThe main reason is that it is the easiest to design. Alconsisls of a CCI) camera, a host computer with wire-though it has only lwo degrees of freedom, the lateralless communication device and three soccer robots.motion can be easily realized by a rotation and a trans-These three pars form a closed loop system of vision. .lation. The weakness is that slipping may occur duringSo we must consider their infuence aumong them. Fothe motion.example the velocity of he robot is related with the res-olution of the CCD camera, the processing speed of theframe grabber, and the cormunication speed betweenthe host computer and the robot. If the speed of the ro-bot is high, the resolution of the CCD camera and the| 中国煤化工processing speed of the frame grabber should also beEnuiondhigh. Othenwise the action of the robot will become un-TYHCN MH Giopesrefined and the positioning of the robot will be inaccu-●319●Joumnal of Harin Istiute of Technology (New Serie), Vol.9, No.3, 2002There are two types of motor, the stepper molorEnooder Cer bot Miderand DC molor that can be used. DC motors are pre-ferred to stepper motors due to smaller sizes and lessWreepower consumption( as shown in Fig. 2).Wheek(R)Fig.3 Arrangement of motorsAxis(R)PrCauster3.2 Design of Control SystemMCU is the core of the control system. During theFig.2 Analysis of forceselection, we consider mainly the operation speed, thefunctions, the size and the power consumption.During the seletin of the DC motor, the princi-There are two main control upproaches. One isple work is to ealeulale is power consumption and theopen-loop control mode and the other is closed looporque of the molor. The siructure and size must alsocontrol mode( a shown in Fig.4).be laken into account.The minimum lorqpue on the robot axis is calculat-1 PWMed by the fllwing caleulations:General power:P= UIMain I。M629 rulse .CPU Dala. AB E MotorCearStatic frictional force: F, = mughex FRolling frictional force:F = F,Ro/RTorque on one axis: T: = 0.5FR = 0. 5mugRoFig.4 Closed loop control modeTorque on one mutor:Ty = T:/(in,) = (mugRo)/(2in,) < (7n)Open-loop control is simple and of low cosl. But itwheredoes not have a good capacity t0 resist the disturbance.m: mass of the robot;Robots with this kind of contrul is ually. used forμ: statie friction cefficient between the grounddemonstration or teaching. Close-loop control robot isand the wheels;generally used to perform the match. By using thisg: gravitational acceleration;mode of control the motion precision is well improved.R: radius of axis;Fig. 5 shows the detailed structure.R: radius of wheel;Aplifiedη,: gear box efficiency;PR:MRotationT: stall torque of the motor listed in the molorDigialIotion Controller PWM+由inar-MooTi: gear ratio;Amature current:l = Ty/Kr +6; .Kp: torque constant listed in the motor speeifica-Two phuseEncod+pulsespeedtion provided;1。: no load current also listed in the motor spec.Fig.5 PMW control structureRotation speed of motor:n = (u-Ir)/kxemt < rums;Frequency modulation is generally used in ther: terminal resistance listed in the motor specifi-communication system. During the design, it shouldcations;choose a suitable wireless communication chip and wellKem: back emf constant listed in the molor spec.design the communication device. The communicationThe specd of the robot isv = (2πRn)/(60i).protocol should be well programmed.During the calculation the gear ratio is determinedaccording to the rotation speed of the wheel and speed4 KINEMATIC MODEL OF THE ROBOTof the motor without load.There are two ways to arrange the motorsDuring the match, the host computer gets all in-(Fig.3). If the size of the motor is small enough, weformation by CCD over the ground. It then analyzes thecan place two motors end to end. This is an arrange-dala中国煤化工to execule by thement with symmnetry stucture. When closed loop con-robot. to make the deci-trol mode is applied, parallel arrangement is often a-sionYHCNMHGbot( a shown indopled owing to the adding of encoder and gearbox.Fig.6) is necessary. The information consists of the●320.Journal of Harbin Insiute of Technology (New Series), Vol.9, No.3, 2002position and orientation of the robot.As showed below，the position of the robot can beCase 1calelated lyP =唯↑2Case 2Fig.6 Cinenatic model of the robotCuse 3The control parameter of the robot is as follow:U={"}where-0-这v: the velocity of the robot;w: the rotating velocity of the robol.The relation between the parameter and the veloci-ArCase 4ty of the left and right wheel of the robot is describedFIg.7 Kinematic model of robotbyv= k +PL3) The robot and the target are not on the sameine. All parameters of the pose will be adjusted.|DL = v一Link point B and point T. Then link point B andw=point R. Draw a line OB thal is perpendicular to BT and(Up =v+叫then draw a line perpendicular I0 BR. These two per-pendicular lines will intersect at point 0. In a periodicwhere L is the width of the robot.time, he robot will move along the circle with the ra-The instantaneous center o[ rotation ( ICR) can be .diurm of OB.calculaled by以=w(R+号)R= 4.n+些2Uk-PDuring the match there are four principle casesYn=a(R-气)( as shown in Fig. 7)4) When there is a roadblock between the robot1) The robot, ball and target are on the sarneand the ball, the robot must change its direction to aline. The pose of the robot does not need adjusted. Invoid the roadblock. In this case , the robot may contin-this case the robot can move forward.ue to move with the present velocity and choose another[D=W=DRpoint P. as the new target point.lo =0P. =P+{Ax},Ay> 1.5L2) The robot, ball and target on the same line bulthe robot should at first rotate and then kick the bal.The velocity being not changed, we can adjust theIn this case the pose of the robot should be adjusted.velocity of the left and right wheel to get the new con-The udjustment can be calculated by following e trol parameter w.quation.pD =0(w =眼-些Dp =p+21,The robot rotats around its own center by he an-Aho I中国煤化工d in one satm-gle 0.pling pers more compli-θ=w.Tcated, it:YHCNMHGemotionmod-el to calculate the control parameters..321●Journal of Harbin Instiute of Technology (New Series), Vol.9, No.3, 2002[A]. Proceedings of RoboCup97[C]. [s 1]: Springer5 CONCLUSIONPress, 1997.[2] MURPHY R R. MIROS0I97 . Robotics Compeition Cor-ner[J]. Robotics and Autonomous Systems, 1998， 23In this paper the design problem of mirosot robot251-281.is discussed , including the analysis of basic functions3] KITANO H. RoboCup-97 Robot Soccer World Cup I[ M].of the robot, the basic ideas of the design, the general[s lI] :Springer Press, 1997.design procedure and main calculations, the cinematic[4] BROOKS R. A robust layered control sysem for a mobilemodel of the robot, etc.robot[ A]. IEEE J Robotics and Automation[C]. [s1]:The design of mirosot robot is not simple. It is re-[sn] ,1986. 14-23.latedwith many high techniques such as robotics ，5] PAUL R P. Robot Manipulalors : Mathematics, Program-ming and Control[ M ]. Cambridge: MIT Press, 1985.mechatronics , automation and intelligent control, digit-al circuit and single chip computer, etc.References:[1] KITANO H. Robo Cup - A callenge problem for AI中国煤化工MYHCNMHG●322●