Drive Your Robot

Drive Your Robot

You can build a  simple mobile robot using two DC motors and two wheels. And now I am going to explain you how you can drive your robot. The driving mechanism now I am going to explain is differential drive.

The differential drive design has two DC motors in left and right which are attached  to two wheels. And since we need three ground contacts we need extra castor wheel.

Here by changing the speeds of the two motors we can make robot to go on different paths.

So using differential drive we can achieve movements as follows

         Driving straight forward : V_Left = V_Right

         Driving a right curve :        V_Left > V_Right

        Spot turning : V_left = -V_Right

So by adjusting the speeds of two motors we can move the robot as we need. So to control the motor speeds we need a motor controller circuit. If you don't know about motor controller you can view the article about the motor controller in this blog.         DC Motor Control Circuit For Your Robot. 

So we can change the motor speed by changing the given voltage to it, otherwise we can change the voltage given at enable pin of the motor controller to change the speed.  

 This could be achieved by using the PWM output pins in your micro controller. So let's see what is Pulse Width Modulation

Pulse Width Modulation
           

            In order to control the motor speed we can generate a voltage signal that is proportional to the motor speed. In other words we can generate an analog voltage signal to control the speed. But instead of generating analog signals we can use pulses of digital signal to achieve this. By changing the width of pulse we can generate the analog voltage signal to control the motor. This method is known as Pulse width modulation. And in most microcontrollers there are PWM output pins to control DC motors, or drive servo motors etc.

So by changing the voltage at enable pin of the motor controller we can drive our robot.

So next our target is to drive the robot according to its environment, for example following an line, or avoiding obstacles etc. So in my next post I will explain how to control the robot motion according to its environment.   There I will discuss about the PID control theory to move robot.