openingsloopfrequentierespons

Openingsloopfrequentierespons, in English open-loop frequency response, describes how a dynamic system responds to sinusoidal excitation when no feedback is applied. For a linear time-invariant system with transfer function G(s) (continuous time) or G(z) (discrete time), the open-loop frequency response is obtained by evaluating the transfer function on the imaginary axis: G(jω) or G(e^{jω}). The output is a scaled, phase-shifted version of the input, with magnitude |G(jω)| and phase ∠G(jω) that vary with frequency. It is commonly presented as a Bode plot, showing magnitude in decibels (20 log10|G(jω)|) and phase in degrees across a range of frequencies.

Measurement and computation: In a model-based setting, G(s) provides the open-loop response directly. In experiments, the frequency response is measured by applying a swept sinusoidal input and recording the steady-state output, then forming the ratio Y(jω)/X(jω). This open-loop transfer function is often denoted L(s) = G(s)H(s) when a controller H(s) is part of the system.

Applications: Openingsloopfrequentierespons is used to assess how the system will behave when feedback is added. It informs controller design (such as lead or lag compensation and gain selection) to achieve target bandwidth, phase margin, and stability. It also supports predicting closed-loop behavior using stability criteria like Nyquist and Bode, and helps evaluate robustness to plant variations.

Relation to closed-loop response: The closed-loop transfer function depends on the open-loop transfer function L(s); shaping the open-loop response directly influences closed-loop performance.