Semiaktiv

Semiaktiv is a German adjective meaning partially active or semi-active, used in technical and scientific contexts to describe systems that are not fully active or passive but lie between these extremes. The term is commonly used in engineering, control theory, and robotics to categorize devices and control strategies that modulate a parameter such as stiffness, damping, or gain in response to operating conditions, while not supplying the primary energy to move the load.

In practice, semi-active systems can adjust their behavior in real time, using external energy to control a parameter but relying on the environment or the host system to supply the main energy flow. Examples include semi-active suspension systems in automobiles, which regulate damping forces via controllable dampers (often magnetorheological or valve-controlled units) based on sensors and control algorithms. Semi-active suspension aims to improve ride comfort and road-holding without the energy losses or complexity of fully active systems. Control strategies include methods such as skyhook or ground-hook control.

The term also appears in other domains, including defense and acoustics, where devices adjust properties like reflectivity or sensitivity without injecting power into the measured signal. In general usage, semi-active describes a middle ground between passive (no energy input or control) and active (energy supplied to the load) approaches.