What is the speed controll system of Turtlebot2(kobuki base) like?

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I'm using Turtlebot 2(kobuki base) & kobuki_core and trying to control the velocity (& angular velocity) of turtlebot 2.

I would like to know kobuki's speed controll system.

Please tell me what the speed control system of Turtlebot2 is like?

(I already know that "Twist.msg" controls the speed of turtlebot and "ControllerInfo.msg" may be related with PID gain. I would like to know what the system between these parameters and turtlebot2(kobuki)'s "real" speed is like. I read slightly codes of kobuki_core ( https://github.com/yujinrobot/kobuki_... ) ,but I could't understand them well...)