Recursive parameter identification algorithm stability analysis via pi-sharing

Pi-sharing is introduced as an extension of the application of passivity and hyperstability concepts for discrete-time systems, providing connections between input-output and state-space stability notions. Using tools developed within the pi-sharing framework, new stability results for the output error class identification algorithm are derived. This approach offers a clear interpretation of the role of the SPR condition in the work of Landau and Silveira and its absence in the work of Tomizuka and Altay.