outputonly

Outputonly is a term used in several fields to describe a condition, mode, or approach in which a system, process, or analysis yields results without a controlled input channel as part of the operation. In practice, output-only implies that inputs are either unknown, unavailable, or deliberately omitted, and emphasis is placed on interpreting the produced data.

In system identification, especially in structural dynamics and vibration analysis, output-only identification (or modal identification) uses measurements of a system’s responses to infer model properties such as natural frequencies, damping, and mode shapes. External excitations may be ambient or not directly measured; the input signal is treated as unknown. The approach relies on the richness of the response data and often employs statistical or optimization techniques to extract parameters from observed outputs.

In hardware or software, output-only mode can refer to devices or programs that generate data or results without accepting user commands or input. Examples include data loggers, sensor nodes that stream measurements, automated report generators, or watchdog systems that publish status information. In such contexts, security and reliability concerns include ensuring that the lack of input channels does not compromise validation or safety.

Limitations arise because the lack of explicit input information can make parameter estimation ill-posed or non-unique. Assumptions about the excitation, environment, or prior models are often required, and results should be validated with independent data or experiments.

See also: system identification, modal analysis, data logger, output-only problem.