In this project we will build a robotic car from scratch and control it using a smartphone via bluetooth.
Like real cars, the robotic car also have wheels which are actuated using DC motors. For a moving object to be stable, you need at least 3 contact points. Like, in car you have four wheels, but in bicycle, there are only two wheel. A cyclist can control bicycle only when he is cycling, but of he stops he can’t balance the cycle without resting his foot on the ground.
In our mobile robot, we have 2 wheels and one caster touching the ground. Caster wheel is just round ball rolling on the ground. It can move in any direction.
A differential wheeled robot is a mobile robot whose movement is based on two separately driven wheels placed on either side of the robot body. It can thus change its direction by varying the relative rate of rotation of its wheels and hence does not require an additional steering motion.
If both the wheels are driven in the same direction and speed, the robot will go in a straight line. If both wheels are turned with equal speed in opposite directions, the robot will rotate about the central point of the axis. Otherwise, depending on the speed of rotation and its direction, the center of rotation may fall anywhere on the line defined by the two contact points of the tires. While the robot is traveling in a straight line, the center of rotation is an infinite distance from the robot.
Figure: (a) Pure translation occurs when both wheels move at the same angular velocity; (b) pure rotation occurs when the wheels move at opposite velocities.
At a time, the mobile robot can move forward, backward, right or left and stop. Given below is the flow chart:
We are using Arduino Bluetooth Controller App to send command to the robot via Serial port 3.
Given below is the example code.