How to make Soccer Robot for RoboCup
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 the 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 of 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 the RoboCup senior category.
we will design an Omni directional robot for small size soccer league.
This guide will cover the following topics:
- Introduction to Soccer Robot and RoboCup SSL
- Basics of Robot
- Manual Controlling of Robot
- Basics of Autonomous Robots
- Mechanical design
- Mechanical Parts
- Designing of robot base
- Omni Wheels design
- Electronic Design
- Electronic Parts
- Wireless Communication using nRF24L01
- Ball Detector Circuit
- Motor Driver
- 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 the system has been divided into four main parts, the first one is Vision system the 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 the camera mounted on top of the field. The position and orientation of ball and robots are computed by the vision system through the 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 the database. The controls are a 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 the 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, the start of the game, end of the 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, the mechanical section which is explained ahead and has four main parts movements, control of the ball, shoot and protection, strong cases and reduced friction Omni wheels.
Basics of Robot
The robot is the machine which performs the human work and tasks automatically or manually. Therefore the robot is defined as the mechanical device 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 the robot can be categorized with three steps that are sensitive, think and act.
This project is based on the AI ( Artificial intelligence )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 a large number of varieties. Manual controlling of robot works through wireless remotes and through another medium of wireless communication like Bluetooth, infra-red, internet protocol using router and or joystick. The block diagram for manually controlling the 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. The autonomous robot is entirely different with respect to its controlling explained in next section. The basic of the 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. The programmer can go with Dijkstra Algorithm or A* Algorithm. Dijkstra 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 another algorithm. The other operation and working are same as the defined in the manual controlling section. The robots have their locomotion defined and all the signals are always predefined, therefore the main part of the 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 the Autonomous robot and it’s controlling.
This section explains the details of mechanical work and design of robot and its
mechanics. Since we are designing the robot having a circular base with Omni wheels, therefore, we have to be very careful about alignment and chases. The purpose of using Omni wheels is to provide a motion in a different direction like the 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 distracted 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 the base of complete autonomous robot therefore on following the commands by avoiding each obstacle to complete the desired tasks the study of the motion of robot mechanism and also the dynamics and mechanics should be done.
The robot consists of such mechanical parts that they cannot be considered as simple. The dimension of the parts with a complete weight of the robot is required to join each with the structure of the robot.
The Robot consists of following mechanical parts.
1- Acrylic Sheet
2- Omni wheels
Designing of robot base
Acrylic Sheet (base)
We have designed the base of the robot from an acrylic sheet which is cut by using the laser cutting machine. The shape of the base is a circle having the diameter of 250mm and the upper portion is about 230mm.The upper two wheels are at the angle of 35dergree from the center and the lower two wheels are at the angle of 45 degrees this designed is inspired from one of the teams 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 the acrylic sheet is about 5mm we choose acrylic because it is light weight and its cutting is less expensive than the metal.
You can also check out this post about Aluminium base of Robot instead of acrylic sheet.click on the image of an aluminum base for more information about designing.
Omni Wheels design
In the robot, we have used the omnidirectional 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 the coupler. These coupler couples the shaft of the
motors. This links the wheels and motors to be connected.
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.
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 an acting force towards the ball.The front dimension of the kicker is given in this figure.
See the Detailed post about Kicker mechanism and solenoid.The solenoid is also discussed in the 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 a constant magnetic field which is uncontrolled by an external source.We have used four motors of the 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) :
- 12 to 24 V
- stall Current = 1.4A
- speed = 1120 rpm (on no load)
- Torque = 1.5 kg.cm
The Dimension of motor:
- Motor Size: 51mm(L) x 36mm(D)
- Shaft Diameter: 6mm
Well, we have discussed almost everything about mechanical part.The electronics part will be discussed in another post.
Read the rest of the part of the Tutorial.
Soccer Robot Electronics Design Part 2