Introduction

This robot is in small size that can follow some different aims. for example searching a target among others.e.g. an object with a certain color or shape. The instrument below should be used it's just a simple lens including 3 optical sensors (photocell). They can detect objects by means of the difference between light intensity each color reflects.

Also it can follow a direction , having turns or angles (0-360), the length of path is not important. The other main goal is solving a labyrinth (Maze). In this field which is the most important one, the brain is just a 89c51 Microcontroller. and this part is separated from PC. The power supply is on the robot itself and is provided by some batteries.

A brief description of different fields and tasks is as follow:

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I-       Mechanical structure

This part includes something about mechanical parts and shape of robot and there is something written about units that produces the movement. The machine can turn to each side , go straight or backward, ... ,and the details are described as below: The movement of robot is provided by means of two separated DC motors. There are two gearboxes that relate the rotational movement from DC motor to Wheels. They play the interface role between motors and turning wheels. Each gearbox is separated from the other one. They change turning ratio into 1/27 of original speed, so, the wheels turn 27 times stronger( power*27, speed/27 ). There are 2 wheels situated on the end of the diameter of the base plate of robot, moving freely (A&B). In this way the movement to each direction is provided.

          As you see, when both C and D are turning forward, the robot moves straight , and if both turn backward, it provides a backward movement on a right direction. Note: The distance is measured by counting the number of the turns using Shaft-encoders. To turn to left or right , there are 2 ways: -Stop C and turn D forward or backward ( or vice versa ) -turning C forward and D backward ( or vice versa )

          note:

          1) There are 2 Shaft-Encoders that help the robot measures the angle of rotation, and passed distance. The robot can have a careful turn up to 360 degree. These opti-counters are situated on CD, and are separated from main wheels E and F. for more information about Shaft-Encoders , refer to "Electronic points" .

          2) There are two wheels moving freely, pointed by A and B. They are used for balancing the base and harnessing the movement and turns in a better way. These two are situated on another diameter called AB and is vertically placed on CD.

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II-      Electronics

All points are gathered about the circuit and their provider elements. There are something about electronics and hardware equipment of robot, for example: The system of gathering information, processing unit, memory, the motor controller circuit, ... are explained here.

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III-     For solving a maze

 In this design, we have used some other components to accomplish robot's main task (solving a maze). For this purpose , we have used shaft-encoders to calculate the amount of movement and to make the action of turning. Another attached block is the system of estimating the distance of objects from the robot in different directions. The detailed description is given below:

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IV-     Sensors
 

         4 infra red transmitter and receiver are used for the sides and probably to beneath with this configuration. the robot can move parallel to the wall of the maze and avoid diversion. It can also find walls or open spaces. The sensors beneath are for detecting some sings (e.g. a line). The circuit accompanying these sensors in as follows. The basic system of the sensor circuit is based on the infra red transmitters being turned on (whit modulated frequency of 1 KHz) sequentially and reading the result from the infra red receivers, which are all, connected in parallel .with this method the robot get information on the objects near itself. condition.

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V-       Shaft Encoders

The robot will use 2 shaft encoders with the aid of these and by a the difference between the movements of the shafts it can estimate how much it has turned or gone forward. The sensors for the shaft encoders are Opti-Counter.

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VI-     Algorithm of solving the maze

The microcontroller program is quit simple and compact, and so it fits in an 89C51. The algorithm for solving the maze is as follow: The algorithm builds up a string of the directions the robot has gone as an example (F-F-R-F-F-F-L-F-F) for the maze. Where F-F means two blocks forward (L=left, R=right, B=back, F=forward). When ever the robot reaches a dead end. The algorithm tries to direct the robot to the pervious position till if finds the desire thing (solving a maze may mean finding something in the maze or finding assign in the maze or arrival in certain situation (x0,y0),etc).