Identification in the time and frequency domains: a comparison using the ECC bench-mark model

A comparison is made between the time domain identification of z-domain models and frequency domain identification of s-domain models. Each approach has specific advantages, which depend on the intended application of the estimated model. The use of periodic excitation signals is also examined and their advantages discussed. The application of time and frequency domain techniques is illustrated using the 1991 European Control Conference bench-mark model, in the presence of coloured noise, load disturbances, nonlinear effects and actuator dynamics. The robustness of the algorithms to each of these effects is studied. It is found that time and frequency techniques give equivalent results in most cases but that wide divergences can occur under certain conditions.