Convection-diffusion is a physical phenomenon that appears in a multitude of dynamical systems, e.g. vibrating string with damping or chemical and thermal systems. This paper focuses on a structure preserving spatial discretization scheme of a general dynamical system with convection and diffusion in the port-Hamiltonian framework. The preservation of the port-Hamiltonian structure ensures that specific properties, such as passivity, of the infinite dimensional system are preserved.
I. INTRODUCTIONSystems with spatial and temporal dynamics occur in many engineering applications where they are typically modeled by partial differential equations or as state space models over infinite dimensional state or phase spaces. The control of infinite dimensional systems is generally troublesome due to the fact that an infinite number of states needs to be controlled through a finite number of control variables. Currently, one can distinguish two common approaches for the control of infinite dimensional systems. The first one, late lumping [1], [2], amounts to designing an infinite dimensional control law which renders the infinite dimensional system stable while achieving some desired performance. The second approach, early lumping [3], amounts to first spatially discretizing the infinite dimensional system and, subsequently, designing a finite dimensional control law based on the dynamics of the spatially discretized system. All control design approaches based on finite element models belong to this category. This paper considers the first step in the early lumping control approach, namely the spatial discretization of a 1D convective and diffusive infinite dimensional port-Hamiltonian (pH) system [4]. There are compelling reasons to model convective and diffusive phenomena in infinite dimensional system in the port-Hamiltonian framework. The most important one is that pH systems have structural properties, such as passivity, that make them extremely suitable for control design, see [5], [6]. These properties are ensured by the special mathematical structure of a pH system and are typically lost by arbitrary spatial discretization schemes.The problem of structure preservation in discretization schemes of pH systems is of paramount importance. Indeed, from the general perspective of modeling, simulation, model approximation, and control system design, there is a need for specialized discretization schemes that preserve the pH structure in spatial discretizations. Classical spatial T. Voß and S. Weiland are with