1. Robotics Workshop Tryst `08

2. Events Covered Diathlon Robowars Grid Game on Micromouse*

3. Diathlon: Tryst ‘08 By Jatin Pasrija

4. Objective The main objective of the competition is to design a manually controlled robot which can move on land as well as water. The robot needs to collect the coins already kept on the field and place them in a basket.

5. Game Field

6. Problem Statement The machine (Emperor) can be at maximum 30x30x30 cm in dimension at the starting time. During the course of the game, the height can reach a maximum of 40cm. The coins (Pawns) are made up of a magnetic material. Hence the most obvious means of collecting them is by using an electromagnet. 7 Coins are resting on poles of height 30 cm - 3 on the Land area and 4 in the water zone.

7. Problem Statement The queen is common to both the team and is resting on a pole of height 35 cm in the center of the field. Points are scored by picking up coins and placing them in a basket which is fixed in the water area. The objective of the game is to score as many points as possible in the time frame of 5 minutes.

8. Mechanical Aspect-1 Base: The structure must be such that the base of the robot must be at least 5 cm above the ground level. This is to ensure that the motors and electrical circuit is kept above the water. Pole: To pick up coins from height of 30-35 cm, we need to have a pole-like structure on the base (something similar to a fishing rod). The pole must hold a movable electromagnet, the movement being produced by a simple pulley arrangement controlled by a single motor.

9. Mechanical Aspect-2 Refer to the problem statement here: “The machine (Emperor) can be at maximum 30x30x30 cm in dimension at the starting time. During the course of the game, the height can reach a maximum of 40cm”. According to our model, our robot will reach height greater than 30 cm at the time of start. Hence it is desirable to have an arrangement in which the pole is of height lower than 30 cm at the beginning, but as soon as the game starts, the height of 40 cm is reached. One of the ways of doing this is by using a spring which engages as soon as the wheels begin motion and pushes the pole to its desired height. There is, of course, scope for innovation here !

10. Electrical Aspect The Diathlon competition is basically a test of mechanical aspect of robotics, in the sense that the electrical arrangement is relatively trivial. Like in any manual robot competition, we need to move the wheel motors in both the clockwise and anticlockwise direction. To turn the robot, we run the left and right motors in opposite direction. The sense of rotation of a DC motor can be reversed by simply reversing the direction of applied voltage. A crude way to achieve this is by using a normal switching circuit. However switching at high currents has its disadvantages. It leads to sparks inside the switch which is not desirable. SPDT=Single Pole Double Throw

11. A Relay circuit We must connect a diode across the coil of the relay. This is to prevent a back-current from flowing into the circuit due to braking of motors.

12. An H-Bridge Arrangement Note that all other configurations will lead to shorting (in other words, it will destroy the circuit !)

13. Working of an H-bridge

15. Using SPDT relay

16. Electrical Component contd… Apart from controlling the motor, we need to drive the motor controlling the height of the electromagnet. This can be done by a similar H-Bridge arrangement as shown in the previous slides. Another aspect is switching of the electromagnet, which is trivial and can be achieved by a simple switch.

17. Micro Mouse: An overview Shashank Singla

18. What is a Micro Mouse A Micro Mouse is an miniature electro-mechanical robot, typically consisting of three main subsystems: 1. The drive system 2. An array of sensors, and 3. The control system. Its purpose is to find its way through ANY type of maze - in the shortest amount of time. maze It integrates several different disciplines of engineering, ranging from electrical to mechanical to computer science

19. Maze The standard maze is made up of a 16 by 16 grid of cells, each 180 mm square with walls 50 mm high. The mice are completely autonomous robots that must find their way from a predetermined starting position to the central area of the maze unaided. autonomous robots

20. Micromouse – Building Blocks

21. Chassis and wheels The chassis needs to hold two motors, a castor, circuit and the power supply. It can be made using aluminum sheets. The robustness and flexibility of the robot depends on the chassis. The wheels are a crucial part of the robot as they must be very precise in their size for the straight motion of the robot.

22. Motors Stepper motors suits for the micromouse. Those which come out of old electronic gadgets would be more than sufficient. While choosing a stepper motor for a micromouse, one must keep a few things in mind. We need to look for motors with low voltages and higher current ratings. This holds true for unipolar as well as bipolar motors.

23. Motor Driver IC L298 can be used as the motor driver for the stepper motors because of its high current capabilities.

24. Micromouse – Building Blocks Sensors Side- looking sensors to measure the distance from the wall and detect their absence/presence. Sensors are the most critical of all the systems. The accuracy of the micromouse relies on the quality of sensors.

25. The Brain Microcontrollers act as the brain for the mouse. PIC 18F4550, a very powerful chip, supported by Microchip’s C18 C compiler. Micromouse demands a lot of processing power, a good onboard ADC (Analog to Digital Converter) and lot of multiprocessing tasks (good set of timers), this PIC has got it all. All the programming for the micromouse can be done in C. Coding would deal with ADC control, motor driver control based on the feedback from the sensors. Further to reduce time in traversing all the paths we would have to manage memory of the robot.

26. LCD Screen LCD is an extremely handy debugging tool. Microchip’s C18 compiler has inbuilt LCD libraries. A 16x2 LCD can be used. You can use the LCD for two main purposes: You can display all the sensor readings on the LCD so that you could observe and note the readings as the mouse moves through the maze. you can also calibrate the mouse easily using the LCD, since, instead of reprogramming the PIC every time, all we have to do is create a menu interface and change the values of ‘parameters’.

27. Power Supply Micromouse need a 12V battery as our power supply. Ni-Cd batteries can be used for this purpose because of their better performance. The batteries should be as light as possible.

28. Expenditure Estimated Cost in Rs. Chassis - 300 Stepper Motors - 1000 Wheels - 400 Motor Drivers - 400 Microcontroller - 300 Sensors - 300 Electronic Circuitry - 200 16x2 LCD – 120 Battery - 600 Approximate Expenditure->Rs 3500

29. Opportunities Micromouse competition has been a very prestigious technical event throughout the world. In India, IIT Bombay organizes this event, which is the centre of attraction in Techfest, with participants from India, Nepal, Sri Lanka, Pakistan, Singapore, Iran and as far as USA battling it out and setting newer records every time. The winner receives a cash prize of USD 1000 along with glory to take away.

30. Manual Robot Demonstration in Robotics Room at 8.00 pm Thank You!