What does hysteresis describe in control systems?

Hysteresis in control systems refers to the phenomenon where the output of a system depends not only on its current input but also on its previous inputs, specifically highlighting the difference in input levels for operation in both directions. This means that when a control system is switched from one state to another (for example, from on to off), the input required to switch back to the original state is different from the initial input that caused the change.

This characteristic is particularly important in systems where overshoot or oscillation might otherwise occur if the input-output relationship were more direct or linear. Hysteresis is commonly observed in devices like thermostats, where the temperature set-point for turning on and off may differ, preventing rapid toggling and providing system stability.

In this context, the focus on the difference in input levels accurately captures how hysteresis works within control systems, acknowledging the history of inputs that influence the current response of a system.