I want to build 4-wheel mobile robot with the servo motor drivers. What website I can find the schematic of servo motor drivers with PIC microcontroller???
Or do you just mean how do you connect a PIC to an RC servo motor? If this is the case, it's not called a servo motor driver- the power electronics that drive the servo are inside the servo so you aren't buiding the servo driver. It's called, "HOw do I connect an RC servo motor to a PIC": http://www.best-microcontroller-projects.com/servo-motor.html
It's basically:
-WIre up the power to the servo and the power to the PIC
-connect the signal pin of the RC servo motor to a pin on the PIC that has something called "output compare"
So (maybe not so obviously?) you need at least two H-bridges (and therefore at least two motors).
You need at least two H-bridges and two motors. They can be set up in two configurations:
-2-drive motors, one for each side of the robot
-or one drive motor and one steering motor- in this case the H-bridge for the steering motor will be much more complicated than the one for the drive motor since you need absolute position feedback and control. You can also just use an RC servo motor (which takes care of that for you) for steering.