Implementation of Wireless Control System for Omni Directional Mobile Robot

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1 ISSN: olume 5, Issue 9, September 06 Implemetatio of Wireless Cotrol System for Omi Directioal obile Robot i i yit Phu, Tha Zaw Soe, Abstract The fuctios of directio cotrolled Omidirectioal mobile robot are described i this paper. Omidirectioal mobile robot cosists of four ecaum wheels. The mai cocept of ecaum wheels mobile robots is the ewly desiged wheel which cosists of a hub carryig a umber of free movig rollers agled at 5⁰ about the hub's circumferece. The stregth of this wheel is the ehaced maeuverability of the mobile robot that eeds extreme maeuverability i cogested eviromet. The aim of this system is to drive o a straight path from a locatio o the floor to aother without havig to rotate first. The Omidirectioal mobile robot is cotrolled the robot s directio to move ay directio by ug joystick. It icludes two mai parts: oe is trasmittig ad aother is receivig. A itroductio to the workigs of a ecaum wheel, the motio aalysis ad the kiematic modelig of a WD omidirectioal robot ug ecaum wheels ad the compariso results betwee theoretical ad experimetal are preseted. Idex Terms Omidirectioal mobile robot, ecaum wheel, Kiematics model, Joystick cotroller, Wireless cotrol ug RF, Arduio Uo I. INTRODUCTION obility is a key issue of assistive mobile robots. Omidirectioal drive mechaism is very attractive i that it guaratees excellet mobility eve i small ad arrow spaces. ay desigs of omidirectioal ad ear omidirectioal vehicles have bee proposed. These ca geerally be broke ito two approaches: covetioal wheel desigs ad special wheel desigs. Covetioal wheels are mechaically simple, have high load capacity ad high tolerace to work surface irregularities. However, due to their o-holoomic ature, they are ot truly omidirectioal. Desigs have bee proposed to achieve ear omidirectioal mobility ug covetioal wheel. ehicles based o this desig have at least two active wheels, each of which has both drivig ad steerig actuators. They ca move i ay directio from ay cofiguratios. However, this type of system is ot truly omidirectioal because it eeds to stop ad re-oriet its wheels to the desired directio wheever it eeds to travel i a trajectory with o-cotiuous curvatures. ost special wheel desigs are based o cocept that achieves tractio i oe directio ad allow passive motio i aother, thus allowig greater flexibility i cogested eviromets. Oe of the more commo omidirectioal wheel desigs is that of the ecaum wheel, iveted i 973 by Begt Ilo, a egieer with the Swedish compay ecaum AB. ecaum wheel is based o the priciple of a cetral wheel with a umber of rollers placed at a agle aroud the periphery of the wheel. The agled peripheral roller traslates a portio of the force i the rotatioal directio of the wheel to force ormal to the wheel directioal. Depedig o each idividual wheel directio ad speed, the resultig combiatio of all these forces produces a total force vector i ay desired directio thus allowig the platform to move freely i directio of resultig force vector, without chagig the directio of the wheel. The overall block diagram of the system is show i fig.. Trasmitter Sectio Receiver Sectio Arduio Uo LCD RF trasmitter RF receiver Arduio Uo otor Drivers otors Fig.. Overall Block Diagram of the System Fig. shows the overall system of the robot. I this research, joystick is used for directio cotrol i the remote cotroller. Firstly, the operator seds the sigal with the help of joystick cotroller. Whe the circuits are started, Arduio Uo is readig the data from the operator ad the sedig data to RF trasmitter that trasmits data to the robot. Durig that time, RF receiver receives the data ad Arduio Uo o the robot is procesg ad aalyzig the data from the remote cotrol. The Arduio Uo cotrols the motor drivers i accordace with the data received from RF receiver o the robot. Depedig o the joystick directios, the four motors will be operated appropriate fuctios. Omidirectioal movemet occurs accordig to the four motor directios by ug four ecaum wheels. I this research, the two circuits are eeded to cotrol the robot; trasmittig circuit ad receivig circuit. The operatio of remote cotrol circuit represets trasmittig part ad the operatio of the motor cotrol circuit represets receivig part. I the remote cotrol circuit, Arduio Uo is the mai cotroller iterfacig with RF module ad joystick. The RF module trasmits serial data with the baud rate 9600bps. The desig process is clearly explaied i the ext sectio with detailed iformatio regardig the compoets which are used, followed by the results ad fially eds with compariso results for error checkig ad coclusio. All s Reserved 06 IJSETR 877

ISSN: 78 7798 olume 5, Issue 9, September 06 II.

I this paper, the system is maily composed of five parts; the first part is the ecaum wheel, the secod is joystick, the third is RF trasmittig ad receivig data, the fourth is the Arduio Uo ad the

The cotrol system cosists of the followig devices; RF modules, Arduio Uo, joystick, L98 Driver, DC motors, LCD are icluded. A. Desig of ecaum Wheel I this research, the omidirectioal mobile robot cosists of four ecaum wheels.

2 ISSN: olume 5, Issue 9, September 06 II. AIN COPONENTS AND DESIGN OF ECANU WHEEL FOR WIRELESS CONTROL ONIDIRECTIONAL OBILE ROBOT SYSTE I this desig, the followig mai compoets are maily used for cotrollig the omidirectioal mobile robot. I this paper, the system is maily composed of five parts; the first part is the ecaum wheel, the secod is joystick, the third is RF trasmittig ad receivig data, the fourth is the Arduio Uo ad the fifth is drivig the motors. The robot is completely cotrolled by wireless remote. The cotrol system cosists of the followig devices; RF modules, Arduio Uo, joystick, L98 Driver, DC motors, LCD are icluded. A. Desig of ecaum Wheel I this research, the omidirectioal mobile robot cosists of four ecaum wheels. The desig of a ecaum wheel icludes rollers that are at a 5 agle to the x ad y axis which traslates a portio of the force i the rotatioal directio of the wheel to the directio ormal to the wheel s directio. Sice the rollers are i a 5 to the x axis ad the y axis, the traslated portio of the force to the directio ormal to the wheel s directio will be equal to the force i the rotatioal axis of the wheel (as show i fig. ). Fig..The velocity compoets of the ecaum wheel (i =,,3, depedig o the wheel) (a). Calculatio of wheel parameters The wheel itself cosists of a hub carryig a umber of free movig rollers agled at 5 about the hub's circumferece. The agled peripheral rollers traslate a portio of the force i the rotatioal directio of the wheel to a force ormal to the wheel directio. Depedig o each idividual wheel directio ad speed, the resultig combiatio of all these forces produce a total force vector i ay desired directio thus allowig the platform to move freely i the directio of the resultig force vector, without chagig of the wheels themselves. The wheel parameters ca be calculated with the followig formula. Where, Fig.. Wheel parameters This shape should respect the equatio: x y R Where, R is the exteral radius of the wheel. The umber of roller ca be calculated by; L r R The legth of the roller (L r ) is, Lr The wheel width (Lw) is, L cos * cos w L r R R ta For L r R 5, R L w R R Left () () (3) () (5) (6) (7) Left Left (i) (ii) Fig.3. (i) Basis compoets of ecaum wheel (ii) exploded view of ecaum wheel Fig.5. Robot motio accordig to the directio of the wheels (b) Kiematic odel of ecaum wheel I order to cotrol the ecaum wheel based vehicle, it is critical to uderstad the kiematic equatios ivolved. The explaatio below gives the cotrol equatios for each motor based o a x, y, w (logitudial, lateral ad yaw) iput. All s Reserved 06 IJSETR 878

Fig.6. Bird s eye view of the ecaum wheel layout Fig.6. shows the force vectors resultig from the wheels beig drive forward.

Here is t the desired velocity of the platform, is the rotatioal velocity of the platform ad r is the distace from the ceter of the platform to the wheel cotact poit with a ad b beig the scalar

ISSN: 78 7798 olume 5, Issue 9, September 06 Logitudial elocity: r x ( t) ( 3 ) Trasversal elocity: r y ( t) ( 3 ) Agular elocity: r z ( t) ( 3 ) ( a b) The resultat velocity ad its directio i the

5cm ROLLER LENGTH Wheel radius cm Number of rollers Legth of the rollers Wheel width ϕ.5cm cm 6⁰ () (5) (6) (7)

(i) Force vectors actio o left ecaum wheel, (ii) Force vectors actio o left ecaum wheel The complete kiematic equatios are; w ty tx ( a b) Left Frot otor w ty tx ( a b) Frot otor 3w ty tx ( a b) Left

3 Fig.6. Bird s eye view of the ecaum wheel layout Fig.6. shows the force vectors resultig from the wheels beig drive forward. It ca be see that if all four wheels are drive forward at the same speed the x-axis compoets cacel out ad the platform will move forwards. Here is t the desired velocity of the platform, is the rotatioal velocity of the platform ad r is the distace from the ceter of the platform to the wheel cotact poit with a ad b beig the scalar compoets. ISSN: olume 5, Issue 9, September 06 Logitudial elocity: r x ( t) ( 3 ) Trasversal elocity: r y ( t) ( 3 ) Agular elocity: r z ( t) ( 3 ) ( a b) The resultat velocity ad its directio i the statioery coordiate axis (x, y, z) ca be achieved by the followig equatios: y ta x R x y TABLE I. PARAETERS OF ECANU WHEEL FOR cm WHEEL RADIUS AND.5cm ROLLER LENGTH Wheel radius cm Number of rollers Legth of the rollers Wheel width ϕ.5cm cm 6⁰ () (5) (6) (7) (8) (i) (ii) Fig.7. (i) Force vectors actio o left ecaum wheel, (ii) Force vectors actio o left ecaum wheel The complete kiematic equatios are; w ty tx ( a b) Left Frot otor w ty tx ( a b) Frot otor 3w ty tx ( a b) Left Rear otor w ty tx ( a b) Rear otor The above equatios are represeted by, (8) (9) (0) () A. Wireless cotrol with RF modules This radio frequecy (RF) trasmissio system employs Amplitude Shift Keyig (ASK) with trasmitter/receiver (Tx/Rx) pair operatig at 3 Hz. The trasmitter module takes serial iput ad trasmits these sigals through RF. The trasmitted data is received by a RF receiver operatig at the same frequecy as that of the trasmitter. The maximum baud rate is 9600 bps. The above equatios are represeted by, w w = 3w w ( a b) x ( a b) * ( a b) y z ( a b) That x, y ad ω z are calculated through the iverse equatio as follows. x = r y * z ( a b) ( a b) ( a b) * 3 ( a b) () (3) (i) (ii) Figure.8. (i) RF module trasmitter (ii) RF module receiver The maximum lauch distace of trasmitter is 00 meter,trasmittig power is 0mW, trasmittig frequecy is 33Hz ad operatig voltage is 3.5 to.the receiver module has operatig voltage is 5. For motor cotrol, i trasmittig part, eleve push buttos are used to iput the data for the RF trasmitter. I receivig part, RF module receives data ad set sigal to the cotroller to drive the motors. All s Reserved 06 IJSETR 879

4 ISSN: olume 5, Issue 9, September 06 RF Trasmitter Trasmit Sigal RF Receiver supported with 5 ad DC supply. The receivig circuit is described i fig. 5 Serial Data Serial Data 5 Exteral Power supply USB iterface CC IN IN S OUT CU Iput Data CU Output Data Figure.9. Wireless RF module trasmittig ad receivig system CC Ao A A A3 A A5 Power pi ANALOG IN Atmega 38P-PU DIGITAL(~PW) Gd 3 ~ ~0 ~9 8 7 ~6 ~ 5 ~ 3 Tx- IN 3 OUT L98 IN OUT 3 ENA A ENA B OUT SENSA SENSB 5 CC S IN IN OUT IN 3 IN OUT L98 ENA A ENA B OUT 3 SENSA OUT SENSB RX-0 III. SYSTE BLOCK DIAGRA AND OPERATION OF THE CONTROL CIRCUIT OF ONIDIRECTIONAL OBILE ROBOT A. Circuit Operatio of the Trasmittig Part Ug the iformatio received from the joystick cotroller, RF module trasmits sigal as serial data to the robot. By presg each correspodig stick movemet, the operator ca cotrol simultaeously ot oly the robot movemet but also extiguishig. The circuit is supported with 5 ad DC supply. The trasmittig circuit diagram is show i fig JOYSTICK 5 X Positio Y Positio SW Exteral Power supply CC Ao A A A3 A A5 Power pi ANALOG IN Atmega 38P-PU USB iterface DIGITAL(~PW) Gd 3 ~ ~0 ~9 8 7 ~6 ~ 5 ~ 3 Tx- RX-0 RF odule receiver Data 5 SCL SDA INT A0 A A Atea IC SS DD EE P0 P P P3 P P5 P6 P7 LCD Display RS RW E D0 D! D D3 D D5 D6 D7 RF odule receiver Data 5 Fig.. Receivig Circuit Atea I. SOFTWARE IPLEENTATION OF THE CONTROL SYSTE I this sectio, trasmittig ad receivig parts of motor cotrol are metioed. Arduio C programmig laguage is applied i this research. A. Trasmittig Part At the start of the system, defiig register, creatig variables ad assigig I/O pis are operated by the Arduio Uo. The facts that whether joystick is pressed or ot are firstly checked. Whe joystick is ot pressed, o data is trasmitted. If the desired joystick directio is pressed, the correspodig sigal is trasmitted i the form of serial data by the RF trasmitter with the baud rate 9600 bps. The trasmissio flow chart is show i figure.. B. Receivig Part At the start of the system, defiig register, creatig variables ad assigig I/O pis are operated by the Arduio Uo. The Arduio Uo receives the serial data from the remote cotrol to iterface with the drivers. There are four motors i the circuit. Each of these motors ca be cotrolled to rotate forward or backward by the istructio of the program. The operatig system flow chart for receivig part is described i fig.3. Fig.0. Trasmittig Circuit B. Circuit Operatio of the Receivig Part All the motors are drive by the commad sigal received from the remote cotrol device. The Arduio Uo is also used as the mai microcotroller to iterface with other devices by receivig the data from RF receiver. The robot is moved to ay directio with the help of four DC motors drive by L98. DC motors are used to tur the robot right/left or forward/backward or forward right/forward left or backward right/backward left ad stop. The circuit is All s Reserved 06 IJSETR 880

Start ISSN: 78 7798 olume 5, Issue 9, September 06 Iitialize Serial Port from Joystick Is Joystick activated? NO YES Trasmit Sigal depeds o Joystick positio NO Stop sigal o? Ed YES Fig.

Ed YES Appropriate fuctios Fig.3. Operatig system flow chart for receivig part NO. TEST AND RESULTS I this system, the speed of motors is cotrolled by joystick, Arduio Uo ad radio frequecy module.

5 Start ISSN: olume 5, Issue 9, September 06 Iitialize Serial Port from Joystick Is Joystick activated? NO YES Trasmit Sigal depeds o Joystick positio NO Stop sigal o? Ed YES Fig.. Operatig system flow chart for trasmittig part Fig..Simulatio result of the system Start Iitialize Serial Iput from Trasmitter Check Serial Iput from Trasmitter Receive the data? Ed YES Appropriate fuctios Fig.3. Operatig system flow chart for receivig part NO. TEST AND RESULTS I this system, the speed of motors is cotrolled by joystick, Arduio Uo ad radio frequecy module. I testig, the directio of motors ca be chaged by presg the switches. For this system, Arduio Uo ca be performed as a cotroller. I the trasmitter sectio, the user eters the iput sigal from the switches ad the these sigals are sedig from microcotroller to radio frequecy module (RF). Radio frequecy trasmitter module seds these sigals to the receiver sectio. I the receiver sectio, receiver module receives the sigals that are set from trasmitter module. Depedig o the received sigals ad the motor will be rotated accordig to the istructed directio. The motor will move forward whe the simulatio result of the system. Simulatio result of the system is show i Fig. Kiematics model of this type of robot has bee calculated ad compare with experimetal result show i Tables. Results of testig coditios are displayed o the LCD as show i Fig 5.Fig 6 ad 7 show the hardware cofiguratio for trasmittig part ad receivig part. Fig.5.Commad Result o LCD TABLE II. THEORETICAL RESULT x y t ω ρ Left Left ⁰ ⁰ Left TABLE III. EXPERIENTAL RESULT x y t ω ρ Left Left Left 5⁰ 5 ⁰ ⁰ ⁰ ⁰ ⁰ All s Reserved 06 IJSETR 88

ISSN: 78 7798 olume 5, Issue 9, September 06

Hardware costructio of trasmittig part Power Bak Battery Rollers ecaum Wheel Arduio Uo RF Receiver odule [] Improved ecaum Wheel Desig for Omidirectioal obile Robot Olaf Diegel, Aparma Badve, Gle

6 ISSN: olume 5, Issue 9, September 06 REFERENCES LCD Trasmittig Atea Joystick Fig.6.Hardware costructio of trasmittig part Power Bak Battery Rollers ecaum Wheel Arduio Uo RF Receiver odule [] Improved ecaum Wheel Desig for Omidirectioal obile Robot Olaf Diegel, Aparma Badve, Gle Bright,Joha Potgieter, Sylvester Tlale echatroic ad Robotics Research Group Istitue of techology ad Egieerig, assey Uiversity, Aucklad mechatroics.massey.ac.z Proc-0 Australia Coferece o Robotic ad Automatio Aucklad 7-9 November [] A Desig of Omi-Directioal for obile Robot Jefri Efedi ohd Salih, ohd Rizo ohd Juhari, Sazali Yaacob adabdul Hamid Adom School of echatroics Egieerig Kolej Uiversiti Kejuruteraa Utara alaysia (KUKU) Kompleks Pusat Pegajia KUKU 0600 Jejawi, Perlis jefri_salih@kukum.edu.my A Robot Egieerig Textbook By ohse Shahipoor (Uiversity of New exico) 00 KUKU Egieerig Research Semiar 006 [3] Ioa Doroftei, ictor Grosu ad eaceslav Spiu, Gh. Asachi Techical Uiversity of Iasi Romaia Omidirectioal obile Robot Desig ad Implemetatio [] Kiematic odel of a Four ecaum Wheeled obile Robot. Hamid Taheri, College of Electroic ad Iformatio NUAA Najig, Chia. Big Qiao, College o Astroautics NUAA Najig Chia. Nurallah Ghaemiezhad, College of Automatio, NUAA Najig,Chia Iteratioal Joural of Computer Applicatios ( ) olume 3 No. 3, arch 05 [5] Rya Thomas,Omi-directioal mobile platform for the trasportatio of heavy object (0, assey Uiversity, Palmerstoe North, New Zealad.) otor Drivers Fig.7.Hardware costructio of receivig part I. CONCLUSION This paper represets a wireless cotrol Omi directioal mobile robot ug ecaum wheel ad it is desiged for oly as a sample. This sample ca be based to costruct Omi directioal mobile robot practically used i dealig with may other applicatios. The ecaum wheels preset a umber of advatages that makes them a real iterest i developmet of the omidirectioal platforms. The suggested mobile robot has a squared mobile platform ad four ecaum wheels at each corer. By harmoiously coordiatig the four ecaum wheels, immediate forward/backward, lateral ad rotatioal motio, i other words, omidirectioal motio is guarateed. Such robots ca be applied as log loads trasportatio, ad idoor applicatios, like small goods trasportatio, powered robotic wheelchairs or shoppig carts etc. are also cotrolled by wireless RF commuicatio. For the future work, to get precise movemet, this robot ca be added a cotrol law ad ca be cosidered the dyamic model of this type of robot. ACKNOWLEDGENTS The author is very thakful to Dr.yit Thei, Rector of adalay Techological Uiversity, for his ecouragemet, ivaluable permissio ad his kid support i carryig out this paper work. The author is deeply grateful to Dr.Wut Yi Wi, Associate Professor ad Head, Departmet of echatroic Egieerig, adalay Techological Uiversity for supplyig all ecessary thigs. The author especially appreciates ad thaks all her teachers for paper support, ad guidace durig theoretical study ad paper preparatio duratios. All s Reserved 06 IJSETR 88

PROJECT #2 GENERIC ROBOT SIMULATOR

Uiversity of Missouri-Columbia Departmet of Electrical ad Computer Egieerig ECE 7330 Itroductio to Mechatroics ad Robotic Visio Fall, 2010 PROJECT #2 GENERIC ROBOT SIMULATOR Luis Alberto Rivera Estrada