• Control systems are present in most systems we see. Example - elevator height.


• Some systems are naturally unstable and tend to self destruct. Example - balanced broom.


• Other systems are self regulating, and tend to some stable state - these are good candidates for open loop control. Example - city water tank


• Other systems need some sort of regulation mechanisms added, these are called closed loop systems. Example - car cruise control


• If a system is simple we will say that it is linear. Example - perfect elevator


• A system can be subject to complicating factors that make it difficult/impossible to model mathematically. Example - elevator in tall building with stretchy cable


• If a system has switched states it can be described as discrete. Example - buttons to call elevator, open/close doors


• Temporal/sequential systems can change over time, this requires sequential control. Example - washing machine