Fundamental lemma and informativity for identification: Scalar non-square strongly σ2-relevant discrete 2D systems

Building on our earlier work (Bharti and Pal, 2024), in this paper, we look at scalar non-square σ 2 -relevant systems, i.e., systems that have compatibility equations along with the relevant governing equation. Algebraically, these are systems with a non-principal equation ideal. We employ the concept of representation formulae developed in (Pal and Pillai, 2013) to provide necessary and sufficient condition for a given data set to be informative for identification. Moreover, we provide an analogue for the fundamental lemma, i.e., a data-driven non-parametric representation of the admissible trajectories of the strongly σ 2 -relevant 2D behaviour.