(a) A Line Follower Robot is an automated guided vehicle, which follows a visual line embedded on the floor or ceiling. A line follower consists of an infrared light sensor and an infrared LED. It works by illuminating a surface with infrared light; the sensor then picks up the reflected infrared radiation and, based on its intensity, determines the reflectivity of the surface in question. The sensor based black line follower robots are one of the most basic robots used to follow black line on white background or vice versa. These robots may be used to in various industrial and domestic applications such as to carry goods, floor cleaning, delivery services and transportation. 

(b) Obstacle Avoidance Robot is designed to allow robot to navigate in unknown environment by avoiding collisions. Obstacle avoiding robot senses obstacles in the path, avoids it and resumes its running. If the sensor detects an obstacle in the middle of the robot’s path, then the algorithm randomly changes its direction to the left or right until the sensors no longer detect an obstacle. Obstacle avoiding robots can be used in almost all mobile robot navigation systems. They can be used for household work like automatic vacuum cleaning. They can also be used in dangerous environments, where human penetration could be fatal.