Logic

Line Following and Turning The autonomous robots are required to perform their respective tasks without any manual guidance. Thus the technique used to make the robots reach the desired locations in order to perform their tasks is the white line following, cross detection and turning technique using the optoelectronic sensors. These optoelectronic sensors are actually developed during the project using light to voltage converter IC – OPT101 and LED. These sensors work on the principle of reflective light amplification. The IC – OPT101 comprised of a photodiode and amplifier. The light of LED reflects from the surface and falls on to the OPT101 which is amplified by the amplifier inbuilt the IC. The intensity of the light falling onto the photodiode of IC depends upon the color of the surface. Thus while the sensor is on the white line it gives the saturated output voltage where as while not on the white line it gives a low voltage. This voltage is converted into a digital signal using an analog comparator IC TLC324 where the second input to the IC is a fixed voltage. Thus when the output voltage of the sensor is below certain level i.e. when the sensor is not on white line it gives ‘0’ as the output whereas if the output voltage of the sensor is above certain level i.e. when the sensor is on the white line it gives ‘1’ as the output. Using six such sensors divided into two rows on in front and one at the rear side the white line following is achieved. To make the robot follow the white line various sequences of the possible states of the sensors are considered and depending upon the same, position of the robot and correction required in the proper direction is analyzed. Finally on the basis of the required correction, PWM signal is applied to the H-Bridge drive circuit which uses LMD18200T IC, and the straight line is followed by the robot. For the motion of the robot high torque Maxon Motors are used with the gearbox having 1:18 ratio of gear reduction. While the robot follows the white line it is also required for the robot to take 90 degree turn in certain direction. For the same the cross detection is used in which the robot counts the number of crosses in the grid it passes and when this number matches with the number of cross where it has to turn or stop, the robot stops the straight line motion and the by rotating both the motors in the opposite directions it takes the turn in the

desired direction till the desired sensor in the front line of the sensors come onto the white line.