Obstacle avoidance/detection mechanism

What is obstacle avoidance/detection?

A robot is made smarter by adding on sensors which will increase its intelligence. Reading and understanding of a robots environment gives the robot with enormous amount or artificial intelligence. Very basic sense required for an autonomous  robot would be to gather details of objects around it. When a robot is required to move from one point to another by itself, it need to understand the obstacles present around it. At a very basic level the information about the surroundings will be the distance of the obstacles from the robot and their position with respect to the robots position. When the robot has capability to extract this information, it can easily navigate without any collision.

How to make a robot avoid/detect an obstacle?

    We need to embed the robot with sensors around it to extract the information about the obstacles surrounding it. The simplest way of doing this is by adding bump sensors(Push button for ex) around the robot. When a robot collides with the obstacle around it, the switch is pressed, this gives a signal to the robot that it has bumped into an obstacle. By having multiple sensors around the robot, the switch activating the signal will give the position of the obstacle with respect to the robot.

By using infrared/ultrasonic sensors, the robot can detect the presence of obstacle around it without any contact with it. This feature can be expanded to measure the distance between the bot and the obstacle to get a digital map of its surrounding.

Obstacle avoidance/detection Algorithm.

We shall consider the robot equipped with three infrared sensors S1, S2 and S3 starting from left. Based on the position of the obstacle the appropriate sensors are activated. Activated sensors are shown in orange. Let us consider the basic scenarios encountered.

Case 1: No Obstacle (All the three sensors are deactivated).

When there is no obstacle in front of the robot, all three sensors S1, S2 and S3 are off. This means that the robot has no obstacles ahead and hence the bot can move forward till it detects any obstacle (by triggering of any sensors).To make a robot move forward, both the motors M1 and M2 are rotated in same direction.

Case 2 :Obstacle detected on right side:

When the robot encounters an obstacle in the front right side, the sensor S3 detects the presence of it and triggers an signal. Now to avoid the obstacle the robot has to turn left. The motor M2 is rotated in the forward direction and M1 is slowed down or stopped. as a net effect the robot turns left and avoids the collision to the obstacle on the right side of the robot.

Case 3: Obstacle on the Left side:

When the robot encounters an obstacle in the front left side, the sensor S1 detects the presence of it and triggers an signal. Now to avoid the obstacle the robot has to turn left. The motor M1 is rotated in the forward direction and M2 is slowed down or stopped. As a net effect the robot turns right and avoids the collision to the obstacle on the left side of the robot.

Case 4: Obstacle in front of the robot:

When the robot encounters an obstacle right in front of the robot, this is signaled by all three sensors S1, S2 and S3. In this situation the robot cannot navigate further and hence a default turn towards right or towards left must be made. Also to be sure that the robot doesn't collide, a sharp turn is made by rotating M2 in reverse direction and M1 in forward direction.