There are two common classes of control systems, with many variations and combinations:
i.) logic or sequential controls, and feedback or linear controls.
ii.) fuzzy logic, which attempts to combine some of the design simplicity of logic with the utility of linear control.
Some devices or systems are inherently not controllable.
The term “control system” may be applied to the essentially manual controls that allow an operator to, for example, close and open a hydraulic press, where the logic requires that it cannot be moved unless safety guards are in place.