PID Control

Control theory looks at a lower level of intelligence than the deliberative and reactive architectures that we have looked at before. An example of when it may be needed in robotics is as follows: you need a robot to travel at some specific speed and that is all the input you give the robot, as the terrain becomes more challenging the motors will have to work harder to keep the robot at this specified speed. A controller can be used that is given required speed and some sensor feedback about the actual speed to figure out how much power the motor needs. PID control is a simple example, PID stands for Proportional, Integral and Derivative. These are all error terms calculated in the controller, in a P control the error is found between the required speed and the current speed, this error is multiplied but some factor and the output is sent to the motors. If you are still interested at this point, (and I think you should be, it's quite important stuff) please check out this article by John Holland from the EE Times and you will learn all about it.

Here is a quick video showing the difference between P control and PID control: