I am building a two-wheels self-balancing robot and using PID controller to control its speed. The measured value is the encoder signals from the Hall sensors on the back of the DC geared motors. But in my notes, it mentions only to use PI controller, meaning that the Derivative term is set to zero. But i can't understand why? Isn't it better to use a full PID controller to achieve the best results?
I researched online and the best explanation i could find is that for a PI controller which controls the speed, there is a need for faster response so the Derivative term can be omitted. But i am not convinced of this explanation... Maybe someone can offer a better and more complete explanation?
Also, for the angle balancing part, why is the PD controller preferred instead of PI controller and why not use full PID?