Difference between Setpoint control system and Follow-up control system
Follow-up control: Here the setpoint is constantly changing. Example herefor: Trajectory of a robot
Fixed value control: Here the setpoint is constant over a longer period of time or permanently. Examples: temperature control, compressed air control.
In general, fixed value controls are easier to handle than follow-up controls.
Note: What you won't necessarily find in a textbook: With a pure P control, there is always a permanent control difference. In the case of a fixed value control with a pure P controller, it is possible to specify an "incorrect setpoint" for the controller in order to actually achieve the desired value of the controlled variable.