# Taxes (systems theory)

Control is influencing the behavior of a system . A system is brought into a different state by control. The change in system behavior occurs through information, messages, stimuli or input.

For the system-theoretical consideration of control , only the flow of information is important; in the form of a mathematical model is to abstract from the accompanying energy and material flow; see. Control theory .

## Examples

• Switching lighting on or off , whereby a changeover circuit with the aid of several switches is a more complex control than that with the aid of just one switch.
• Limit value switching: When a threshold value is reached, a switching occurs, e.g. B. switching off a kettle when the cooking temperature is reached.
• Program control: Changes in the state of several control variables take place one after the other according to a time or route plan. The change in state of a control variable can be a prerequisite for changing the next variable B. in a washing machine according to the washing program.
• Steering: the intended influencing of the direction of travel of vehicles of all kinds

## Delimitation from the regulation

Control is not regulation with which it is often confused. A control alone cannot prevent an additional change in status from occurring in the system due to fault (s). Regulation basically means counteracting changes in the state of the system through disturbances.

### Examples

• Water temperature: Influencing the water temperature at the tap by changing the tap positions is solely a control. Keeping the water temperature constant by turning the taps on the basis of the actual water temperature determined, by comparing the setpoint and actual value, is overall a regulation. The disturbance is essentially the changing temperature of the incoming hot and cold water and changes in the flow rate at the tap due to indirect expansion or contraction due to changing temperature. Independent regulation takes place in automatic mixers that contain a temperature sensor and a mixer tap controlled by this. Only the setpoint of the water temperature needs to be set on such devices.
• Direction of travel: The steering of vehicles to influence the direction of travel is a control. The change in the direction of travel by steering becomes a regulation in that the controller permanently influences the status of the steering system variable after comparing the direction of travel with the desired course of the journey (e.g. on the road, in the air corridor, in the canal). The “steering” of a car is generally a follow-up regulation: the car journey should follow the road; Disturbances are that the course of the road is constantly changing. Vehicles in autopilot mode are controlled without human intervention.