nodisturbance

Nodisturbance is a term used to describe a condition or design objective in which a system's output remains unaffected by external disturbances. It is not a universally standardized term but appears in discussions of disturbance rejection and decoupling in control theory, electronics, and mechanical systems. The concept emphasizes the goal of eliminating or greatly reducing the influence of perturbations.

In formal terms, a nodisturbance design would enforce that the transfer function from disturbance input to output is zero, often by feedback control, feedforward cancellation, or structural decoupling. Equivalent ideas include robust control, disturbance observers, and H-infinity methods that strive to minimize sensitivity to disturbances within a specified operating range.

Applications abound in power supplies, where regulation aims for nodisturbance against input voltage fluctuations; in aerospace, where attitude control counters wind disturbances; and in precision manufacturing, where vibration isolation reduces external perturbations on sensors or actuators.

Limitations: true nodisturbance is rarely achievable across all frequencies; practical implementations offer partial disturbance rejection over a bandwidth, with trade-offs in stability, cost, and performance.

See also: disturbance rejection, robust control, decoupling, transfer function, feedback control.