Further results on nonlinear receding-horizon observers

In this note, further results are proposed that concern the design and the convergence of receding-horizon nonlinear observers. The key feature is the definition of observability radius in relation with a prespecified compact set of initial configurations. This enables a semiglobal convergence result to be derived that turns out to be a global convergence result when appropriate regularity assumptions are made. A simple example is proposed to illustrate the basic features of the note.