How to make Soccer Robot for Robocup

How to make Soccer Robot for Robocup

Hey Everyone..!!!
The news is that We have some great and most exciting events coming ahead.Some of us are very curious about robotics.Sometimes just for the fun and sometimes for the sake of academic projects.
And believe me when first time i made a robot i was too much excited to play with it.After that i participated in some robotics competitions and then i heard about something that could be the
Dream.That is something Big..!!.I hope You are aware about this event.Yes i'm talking about Robocup.
 I made a robot for small soccer league that was held in my institute.On that basis we were preparing for the robocup. So here i'm going to tell you about small soccer league (SSL).After that we will see some setup for robocup senior category.
we will design an omni directional robot for small size soccer league.

This guide will cover the following topics:

Contents:

1. Introduction to Soccer Robot and Robocup SSL
2. Basics of Robot
3. Manual Controlling of Robot
4. Basics of Autonomous Robots
5. Mechanical design
6. Mechanical Parts
7. Designing of robot base
8. Omni Wheels design 
9. Dribbler
10. Kicker
11. Electronic design
12. Electronic Parts
13. Wireless Communication using nRF24L01
14. Solenoid
15. Ball Detector Circuit
16. Booster
17. Motor Driver
18. Programming and Algorithms

Introduction to Soccer Robot and Robocup SSL

This guide is based on Small Size League (SSL) and making of Soccer playing Robot .The entire

system has been divided into four main parts, the first one is Vision system second one is Artificial

Intelligence (AI) system, third is Referee Box and finally five remotely controlled robots. It includes

mechanics, electronics, mechatronics and programming skills

The vision system is digitally processed with two signals capturing from camera mounted on top of the field. The position and orientation of ball and robots are computed by the vision system through camera. The information of vision system is transmitted to AI system which is responsible for making, deciding and providing the strategic game decisions. The roles of robots provide the teams to be acted according to the commands transmitted by database. The controls are goalkeeper, defense and forward. The main factor is to avoid the collision with the robots and specifically avoid the collisions with opponents. The decisions for game are to play with commands given to the wireless receiver. The robot is capable enough to execute the commands that converted by the AI system. This cycle is repeated 30 times per second. Moreover, the referee transmits relevant decisions such as penalties, goals, start of game, end of game, etc. These commands are sent to the AI system through a serial link. All robots are responsible and capable enough to execute effectively the commands sent via AI system. Our robot includes specialized and effective electronics with such accuracy to communicate with remote computer and control locomotion and all defined actions. Similarly mechanical section which is explained ahead and has four main parts movements, control of ball, shoot and protection, strong chases and reduced friction Omni wheels.

Basics of Robot

Robot is the machine

which performs the human work and tasks automatically or manually. Therefore the robot is

defined as the mechanical devise which can be programmed to let work as per command defined,

such as moving, picking the tools, dropping the tools and dragging etc. The action of robot can

be categorized with three steps that are sense, think and act.

This project is based on the AI ( Artificial intellegence )system and the control signals are given and processed through wireless module. The basic is the design of AI system, communication done through NRF wireless module, strong chases and selection of the motors using required motor drivers.

Manual Controlling of Robot

The robots are designed with a test bench where you can test your algorithms and signal processing. The batteries to power-up the modules must be efficient and their current rating must meet the requirement.

The motors are selected such that their RPM should be enough to bear the weight of the robot. The speed must not be reduced. Chases of the robot and structure of the robot must be designed with sharp precision.

The tires must be selected as to have locomotion in large number of varieties. Manual controlling of robot works through wireless remotes and through other medium of wireless communication like Bluetooth, infra-red, internet protocol using router and or joystick. The block diagram for manually controlling robot.

Basics of Autonomous Robots

The autonomous robots have their own algorithms otherwise it can be easy by connecting sensors at different places of the robots. Autonomous robot is entirely different with respect to its controlling explained in next section. The basic of Autonomous robot is mainly consists of AI and the vision system. The vision system is designed to give information of the field to AI system and the AI has algorithms built in it. The decisions are taken according to the information received. The game decisions are totally dependent on AI system.

AI works on two algorithms mainly. Programmer

can go with Dijktra Algorithm or A* Algorithm. Dijktra is old one and it is not followed these days

usually, but A* is being followed and many projects of AI has been designed using many other algorithm. The other operation and working is same as the defined in manual controlling section. The robots have their locomotion defined and all the signals are always predefined, therefore the main part of robot is the motors. The motors get the signals from their respective drivers and the drivers get signals from the receiver of the wireless module. The communication is totally based on wireless and between two nodes there will be no wired connections. The receiver is NRF module and getting signals from database wirelessly. The programming and algorithms are built for the receiver to understand the transmitting signals coming from the transmitter of the database. These all summarize the basics of Autonomous robot and its controlling.

Mechanical design

This section explains about the details of mechanical work and design of robot and its

mechanics. Since we are designing the robot having circular base with omni wheels therefore we

have to be very carefully about alignment and chases. The purpose of using omni wheels is to

provide a motion in different direction like front, back, diagonal, left, right, clockwise and

counter clockwise. The base of the robot is such that it supports the rigidity to the structure. The

base of any robot must be dynamically strong that it must be following the direction and must

not be distract from the given commands. The design must be chosen that the integration of body

parts is easy.The chapter aims to create the locomotion of robot and such mechanism to

create base of complete autonomous robot therefore on follow the commands by

avoiding each obstacle to complete the desired tasks the study of motion of robot mechanism and

also the dynamics and mechanics should be done.

Mechanical Parts

Robot consists of such mechanical parts that they cannot be considered as simple. The dimension

of the parts with complete weight of the robot is required to join each with structure of the robot.

The Robot consists of following mechanical parts.

1- Acrylic Sheet

2- Omni wheels

3- Dribbler

4- Kicker

5- Motors

Designing of robot base

Acrylic Sheet (base)

We have designed the base of robot from acrylic sheet which is cut by using laser cutting

machine. The shape of base is circle having the diameter of 250mm and the upper portion is

about 230mm.The upper two wheels are at the angle of 35dergree from centre and the lower two wheels are at the angle of 45 degree this designed is inspired from one of the team who participated in Robocup. This design gives the drag to the robot when moving forward and also a movement in

the respective angle. The thickness of acrylic sheet is about 5mm we choose acrylic because it is

light weight and its cutting is less expensive then the metal.

You can also check out this post about Aluminium base of Robot instead of acrylic sheet.click on the image of aluminium base for more information about designing.

how-to-design-robot-chassis

Omni Wheels design 

In the robot we have used the omni-directional wheels because these wheels give us the

advantage of the movement in any direction it can also slide the robot and reduces the friction.

The diameter of each wheel is 60 mm. Omni-wheels are advised on the abstraction of an

accustomed caster that has the adeptness to cycle or 'slip' sideways.

This is the sketch diagram of coupler. These coupler couple the shaft of the

motors. This links the wheels and motors to be connected.

Dribbler

The dribbler is used to have the ball in the possession of the robot it is located on the front of

robot a rod which is attached to the helical gear and the other helical gear is located at the

90degree which is rotated due to the motor and revolve the dribbler rod. The dimension of the

dribbler is given.

Kicker

The kicker material is of aluminum at the front end which will be kicking the ball.The rod

which is passing inside from solenoid coil is the mixture of aluminum and MS rod. The

mechanism of how the kicker will be acting force towards the ball.The front dimension off the kicker is given in this figure.

See the Detailed post about Kicker mechanism and solenoid.The solenoid is also discussed in electronics section.

Selection of motor

The motors which we have used in this robot are a DC gear motors having high rpm and high

torque they are PMDC typed.The advantages of these motors are constant magnetic field which

is uncontrolled by external source.We have used four motors of same rpm assembled with Omni

wheels. The locomotion of the robot is controlled with the logics designed using H-bridge with

each motor to control the direction of the motor.

The specification of motor (Model Number:JGY37-545) is

1.  12 to 24 V
2.  1.2A
3.  stall Current = 1.4A
4.  speed = 1120 rpm (on no load)
5.  Torque = 1.5 kg.cm

The Dimension of motor are

1.  Motor Size: 51mm(L) x 36mm(D)
2.  Shaft Diameter: 6mm

ELECTRONIC DESIGN 

Electronic Parts

1.  Battery
2.  Power distribution circuit
3.  H-bridge
4.  Arduino
5.  NRF-module
6.  Boost Converter
7.  Ball detector circuit
8.  Solenoid

Battery

The battery is providing source to each component and it is selected as per requirement of

the current. We have selected the lipo battery for our robot because it’s a light weight and

provide us our required current. Our Battery consist of 5 lipo cells each cell having

3.7volts total of 18.5volts battery having 5000mAh current.

• Output voltage 18.5V
• Initial Current 5A Max
• Discharge (c) 25
• Max Charge Rate (C) 2
• Weight (g) 640
• Length(mm) 146
• Height(mm) 51
• Width(mm) 42

Power Distribution circuit

In the robot we needed 3 different voltages to operate our devices first our battery contain

18.5 volts which are needed to operate motors secondly we needed 12 volts to operate our

motor driver IC IR2104, dribbler motor and for booster circuit because input of our booster is

12 volts. In last we needed 5 volt to operate our controller Arduino and for ball detector

circuit.

For this purpose we design two regulators for step down voltages by using LM7812 and

LM7805 the circuit diagram are as follow.

12 volt regulator circuit consists of

1.  LM7812
2.  diode

5volt regulator circuit consists of

1. LM7805
2. diode
3. capacitor

Arduino Development Board

I am not going to discuss about the basics of arduino here.you can read about arduino in these following posts.

Getting-started-with-arduino-microoController

Guide of arduino boards

Wireless Communication using nRF24L01

The wireless communication is done between various nodes. Since we are at the node of between

receiving data from GUI, therefore wireless module is used. The controlling of robot is being

done by using joystick. The module which we used for wireless communication is nRF24L01.

I already discussed complete details about nrf and arduino interfacing.Read the detailed post of nrf24Lo1+. Arduino codes for nrf are also available in that post.

Wireless Communication using arduino and nrf24lo1+

Solenoid

A solenoid consists on coil of insulated wire. We have to design solenoid to provide strong inner

magnetic field in order to fulfill our purpose of kicking mechanism. For this purpose Teflon

material is used on which copper is wounded, when current flowsthrough the coil then strong

magnetic field is produced within the core due to which kicking mechanism of the robot will

work.

One more post is available for kicker mechanism and solenoid.You can get the design files from there.

specification of the solenoid:

1. Wire gauge 30 AWG
2. Input voltage 230 V
3. Number of turns of Cu wire 1800
4. Resistance/meter of Cu wire 0.339
5. Diameter of Teflon 8mm

Ball Detector Circuit

To start the dribbler we have designed the ball detector circuit which is mounted on the sides of

dribbler by using IR sensor. When there is no object the receiver receive the signal from

transmitter and when the ball comes to our robot the signal will be disconnected the receiver will

not generate the output signal and then this logic is inverted through using NOT gate and it will

generate a signal to operate the motor driver for the dribbler. The circuit is shown in the figure

Read Detailed post of Ball detector circuit with circuit diagram.

Booster

For the kick we have to energize our coil and to energize the coil we needed high voltages for

this purpose we have designed the boost converter which convert the 12 volt into 220 volts.

See the Detailed post about Booster 

Booster circuit for solenoid mechanism

Motor Driver

To control the direction and speed of motor we have to use motor drivers.

I have done this part using L298 ic and also with L298 module.

See the related post to this part.

L298 and IR2104 motor driver circuits

motor-drivers-and-dual-h-bridge-l298

PROGRAMMING AND ALGORITHMS

First step was to control robot manually by using remote and wireless communication this step

was done by using arduino and nrf we first manually control the robot and check its parts are

properly working and seeing its direction by controlling motors.

Here is the Code for arduino boards:

Code

1. TX

#include <SPI.h>

#include <nRF24L01.h>

#include <RF24.h>

#define CE_PIN 9

#define CSN_PIN 10

#define JOYSTICK_X A0

#define JOYSTICK_Y A1

#define JOYSTICK_A A2

#define JOYSTICK_B A3

const uint64_t pipe = 0xF2E4F3F6E9LL;

RF24 radio(CE_PIN, CSN_PIN);

int joystick[4];

void setup()

{

Serial.begin(9600);

radio.begin();

radio.openWritingPipe(pipe);

}

void loop()

{

joystick[0] = analogRead(JOYSTICK_X);

joystick[1] = analogRead(JOYSTICK_Y);

joystick[2] = analogRead(JOYSTICK_A);

joystick[3] = analogRead(JOYSTICK_B);

radio.write( joystick, sizeof(joystick) );

}

2. RX

#include <SPI.h>

#include <nRF24L01.h>

#include <RF24.h>

#define CE_PIN 9

#define CSN_PIN 10

const uint64_t pipe = 0xF2E4F3F6E9LL;

RF24 radio(CE_PIN, CSN_PIN);

int joystick[4];

int x,y,a,b;

// Motor A

int dir1PinA = 36;

int dir2PinA = 37;

int speedPinA = 5;

// Motor B

int dir1PinB = 34;

int dir2PinB = 35;

int speedPinB = 4;

// Motor C

int dir1PinC = 24;

int dir2PinC = 25;

int speedPinC = 2;

// Motor D

int dir1PinD = 26;

int dir2PinD = 27;

int speedPinD = 3;

void setup()

{

Serial.begin(9600);

pinMode(dir1PinA,OUTPUT);

pinMode(dir2PinA,OUTPUT);

pinMode(speedPinA,OUTPUT);

pinMode(dir1PinB,OUTPUT);

pinMode(dir2PinB,OUTPUT);

pinMode(speedPinB,OUTPUT);

pinMode(dir1PinC,OUTPUT);

pinMode(dir2PinC,OUTPUT);

pinMode(speedPinC,OUTPUT);

pinMode(dir1PinD,OUTPUT);

pinMode(dir2PinD,OUTPUT);

pinMode(speedPinD,OUTPUT);

delay(1000);

Serial.println("Nrf24L01 Receiver Starting");

radio.begin();

radio.openReadingPipe(1,pipe);

radio.startListening();;

}

void loop()

{

if ( radio.available() )

{

bool done = false;

while (!done)

{

done = radio.read( joystick, sizeof(joystick) );

//Serial.print("X = ");

Serial.print(joystick[0]);

//x=joystick[0];

//Serial.print(" Y = ");

Serial.println(joystick[1]);

//y=joystick[1];

//Serial.print(" A = ");

Serial.print(joystick[2]);

//a=joystick[2];

//Serial.print(" B = ");

Serial.print(joystick[3]);

//b=joystick[3];

if(joystick[0]<2){ // Forward

analogWrite(speedPinA, 180);

analogWrite(speedPinB, 180);

analogWrite(speedPinC, 150);

analogWrite(speedPinD, 150);

digitalWrite(dir1PinA, LOW);

digitalWrite(dir2PinA, HIGH);

digitalWrite(dir1PinB, HIGH);

digitalWrite(dir2PinB, LOW);

digitalWrite(dir1PinC, LOW);

digitalWrite(dir2PinC, HIGH);

digitalWrite(dir1PinD, HIGH);

digitalWrite(dir2PinD, LOW);}

downward

else if(joystick[0]>1022){

analogWrite(speedPinA, 180);

analogWrite(speedPinB, 190);

analogWrite(speedPinC, 150);

analogWrite(speedPinD, 150);

digitalWrite(dir1PinA, HIGH);

digitalWrite(dir2PinA, LOW);

digitalWrite(dir1PinB, LOW);

digitalWrite(dir2PinB, HIGH);

digitalWrite(dir1PinC, HIGH);

digitalWrite(dir2PinC, LOW);

digitalWrite(dir1PinD, LOW);

digitalWrite(dir2PinD, HIGH);}

//ccw

else if(joystick[3]>1021){

analogWrite(speedPinA, 120);

analogWrite(speedPinB, 135);

analogWrite(speedPinC, 60);

analogWrite(speedPinD, 60);

digitalWrite(dir1PinA, HIGH);

digitalWrite(dir2PinA, LOW);

digitalWrite(dir1PinB, HIGH);

digitalWrite(dir2PinB, LOW);

digitalWrite(dir1PinC, HIGH);

digitalWrite(dir2PinC, LOW);

digitalWrite(dir1PinD, HIGH);

digitalWrite(dir2PinD, LOW);}

//cw

else if(joystick[3]<2){

analogWrite(speedPinA, 120);

analogWrite(speedPinB, 120);

analogWrite(speedPinC, 60);

analogWrite(speedPinD, 60);

digitalWrite(dir1PinA, LOW);

digitalWrite(dir2PinA, HIGH);

digitalWrite(dir1PinB, LOW);

digitalWrite(dir2PinB, HIGH);

digitalWrite(dir1PinC, LOW);

digitalWrite(dir2PinC, HIGH);

digitalWrite(dir1PinD, LOW);

digitalWrite(dir2PinD, HIGH);}

else {// Stop (Freespin)

analogWrite(speedPinA, 0);

analogWrite(speedPinB, 0);

analogWrite(speedPinC, 0);

analogWrite(speedPinD, 0);

digitalWrite(dir1PinA, LOW);

digitalWrite(dir2PinA, LOW);

digitalWrite(dir1PinB, LOW);

digitalWrite(dir2PinB, LOW);

digitalWrite(dir1PinC, LOW);

digitalWrite(dir2PinC, LOW);

digitalWrite(dir1PinD, LOW);

digitalWrite(dir2PinD, LOW);}

//kick

if(joystick[2]<2){

digitalWrite(40,HIGH);}

else{

digitalWrite(40,LOW);}

}

}

else

{

analogWrite(speedPinA, 0);

analogWrite(speedPinB, 0);

analogWrite(speedPinC, 0);

analogWrite(speedPinD, 0);

digitalWrite(dir1PinA, LOW);

digitalWrite(dir2PinA, LOW);

digitalWrite(dir1PinB, LOW);

digitalWrite(dir2PinB, LOW);

digitalWrite(dir1PinC, LOW);

digitalWrite(dir2PinC, LOW);

digitalWrite(dir1PinD, LOW);

digitalWrite(dir2PinD, LOW);

Serial.println("No radio available");

}

}

Concluding Statement:

After these step we proceed to the Artificial intelligence, after controlling manually robot. First we

serially communicate it with GUI through NRF module. One end of NRF is interfaced with

Arduino UNO R3 and on another end we used Arduino MEGE 2560.

in SSL vision the camera captures the image of the robots playing and ball by using color pattern

embed on them. This information is broadcasted though WIFI modem. This than is received by

our PCs and this information extracted through the file provided by management of the event

named as ‘protobuf.’ This information is further utilized to calculate and make the strategy for

our robots on the field and predict the movement of opponent and ball using Line equations and

orientation. This smart intelligence is used to make strategy. This strategy is used to calculate the

directions and PWMs of all the motors mounted on each robot. Than transmitted to our robot

through NRF modules. For this AI server, we are using multi threading in C# to process for 2

robots at the same time.

I hope you understand the method and sequence of steps.Half of the things i have covered in separate posts so that's why i didn't discussed everything here.
In coming post we will see how to setup the field for autonomous robot.Installation of SSL software and testing with example code.
Follow for upcoming updates as still there is much more left about autonomous robot.so we will cover up everything in coming posts.
I hope you enjoyed it...keep making robots...!!!