Output Feedback Control of Radially-Dependent Reaction-Diffusion PDEs on Balls of Arbitrary Dimensions

TL;DR

This paper develops a novel power series method to solve boundary control problems for reaction-diffusion PDEs with radially-varying coefficients on n-balls, overcoming singularities that hinder traditional approaches.

Contribution

It introduces a direct power series approach for kernel equations with singularities, establishing conditions for analyticity and evenness, and enabling practical control and observer design.

Findings

Proves existence and convergence of the series solution.

Provides a numerical method applicable despite singularities.

Addresses boundary control and estimation for radially-varying PDEs.

Abstract

Recently, the problem of boundary stabilization and estimation for unstable linear constant-coefficient reaction-diffusion equation on n-balls (in particular, disks and spheres) has been solved by means of the backstepping method. However, the extension of this result to spatially-varying coefficients is far from trivial. Some early success has been achieved under simplifying conditions, such as radially-varying reaction coefficients under revolution symmetry, on a disk or a sphere. These particular cases notwithstanding, the problem remains open. The main issue is that the equations become singular in the radius; when applying the backstepping method, the same type of singularity appears in the kernel equations. Traditionally, well-posedness of these equations has been proved by transforming them into integral equations and then applying the method of successive approximations. In this case, with the resulting integral equation becoming singular, successive approximations do not easily apply. This paper takes a different route and directly addresses the kernel equations via a power series approach, finding in the process the required conditions for the radially-varying reaction (namely, analyticity and evenness) and showing the existence and convergence of the series solution. This approach provides a direct numerical method that can be readily applied, despite singularities, to both control and observer boundary design problems.