Can anyone tell me how to control the DC motors using ROS and Arduino

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On the smaller Arduinos with only 2kb RAM I've had trouble using rosserial because of the amount of RAM consumed, so I've abandoned that for ros_arduino_bridge. If you are using a motor driver not already supported by ros_arduino_bridge, you'll have to modify the code in a couple of places.

First, in ROSArduinoBridge.ino, look at this code (lines 48-64):

//#define USE_BASE      // Enable the base controller code
#undef USE_BASE     // Disable the base controller code

/* Define the motor controller and encoder library you are using */
#ifdef USE_BASE
   /* The Pololu VNH5019 dual motor driver shield */
   #define POLOLU_VNH5019

   /* The Pololu MC33926 dual motor driver shield */
   //#define POLOLU_MC33926

   /* The RoboGaia encoder shield */
   #define ROBOGAIA

   /* Encoders directly attached to Arduino board */
   //#define ARDUINO_ENC_COUNTER
#endif

You need to uncomment the definition of USE_BASE, comment out ROBOGAIA, and then add your own define for your motor controller, say #define RKI1340_MOTOR_CONTROLLER.

Then, in motor_driver.ino, you'll need to add code to support that motor driver. The bottom of that file looks like this:

#else
  #error A motor driver must be selected!
#endif

You'll need to add an #elif before the #else for RKI1340_MOTOR_CONTROLLER, and add a definition of void setMotorSpeeds(int leftSpeed, int rightSpeed).

There are other changes required to support encoders different from the ones already coded. You might compare with the changes Marco Walther made to support the Pololu A-Star board with onboard motor driver. (I've contributed to his mods.)

https://github.com/mw46d/ros_arduino_...