onoffkontroll

Onoffkontroll, known in English as on/off control or bang-bang control, is a simple control strategy in which the actuator output is restricted to two states: fully on or fully off. The control action is determined by comparing a process variable to a setpoint, often with a hysteresis to prevent rapid switching.

Operation: The system measures a variable y(t) and uses a threshold scheme with an upper threshold y_high and a lower threshold y_low. If y(t) exceeds y_high, the actuator is activated ('on'); if y(t) falls below y_low, the actuator is deactivated ('off'); if y(t) lies between thresholds, the previous state is maintained. This creates a deadband that reduces switching frequency.

Characteristics and trade-offs: Simple, robust, and inexpensive; does not require a precise model or continuous control action. It can produce sustained oscillations around the setpoint due to the process dynamics, and is inherently non-optimal from a control perspective. It may cause energy inefficiency and wear in mechanical relays due to frequent switching unless constrained by hysteresis.

Applications: Widely used in residential thermostats, heating and cooling systems, refrigeration, motor control with relays, and some process industries where a binary actuator is adequate or where simplicity is prioritized.