What types of controllers are there?

Two-point controllers operate with two states: on and off. Three-point controllers add a neutral intermediate state. In contrast, continuous controllers, which are designed to reach and maintain the setpoint quickly and accurately, operate with less overshoot. The basic types of continuous controllers are P, I and D controllers. The P controller quickly brings the actual value closer to the setpoint, but has a permanent control deviation that can be compensated for by combining it with an I controller. The I controller integrates the control deviation over time to compensate for it, but is slow. A PI controller combines these characteristics, but responds slowly to sudden changes. This is where the D controller comes in, quickly correcting even small deviations. Since a pure D controller does not recognise a constant deviation, it is combined with P or PI controllers to improve response time. A PID controller combines all three algorithms to respond quickly to both large and small control deviations and eliminate permanent deviations.