Abstract. We present a mathematical and numerical analysis on a control model for the time evolution of a multi-layered piezoelectric cantilever with tip mass and moment of inertia, as developed by Kugi and Thull [31]. This closed-loop control system consists of the inhomogeneous Euler-Bernoulli beam equation coupled to an ODE system that is designed to track both the position and angle of the tip mass for a given reference trajectory. This dynamic controller only employs first order spatial derivatives, in order to make the system technically realizable with piezoelectric sensors. From the literature it is known that it is asymptotically stable [31]. But in a refined analysis we first prove that this system is not exponentially stable.In the second part of this paper, we construct a dissipative finite element method, based on piecewise cubic Hermitian shape functions and a Crank-Nicolson time discretization. For both the spatial semi-discretization and the full x − t-discretization we prove that the numerical method is structure preserving, i.e. it dissipates energy, analogous to the continuous case. Finally, we derive error bounds for both cases and illustrate the predicted convergence rates in a simulation example.
ModelThe Euler-Bernoulli beam (EBB) equation with tip mass is a well-established model with a wide range of applications: for oscillations in telecommunication antennas, or satellites with flexible appendages [2,5], flexible wings of micro air vehicles [8], and even vibrations of tall buildings due to external forces [41]. The interest of engineers and mathematicians in the corresponding control problems started in the 1980s. So various boundary control laws have been devised and mathematically analyzed in the literature -with the stabilization of the system being a key objective (cf. [34]). Soon afterwards, also exponentially stable controllers were developed which require, however, higher order boundary controls for an EBB with both applied tip mass and moment of inertia [42]. On the other hand, if only a tip mass is applied, lower order controls are sufficient for exponential stabilization [12]. In spite of this progress, and due to its widespread technological applications, considerable research on EBB-control problems is still underway: In the more recent papers [22,20] exponential stability of related control systems was established by verifying the Riesz basis property. For the exponential stability of a more general class of boundary control systems (including the Timoshenko beam) in the port-Hamiltonian approach we refer to [49].We shall analyze an inhomogeneous multi-layered piezoelectric EBB with applied tip mass and moment of inertia, coupled to a dynamic controller that uses only low order boundary measurements. This system was introduced by Kugi and Thull in [31] to independently control the tip position and the tip angle of a piezoelectric cantilever along prescribed trajectories. This beam is composed of piezoelectric layers and the electrode shape of the layers was used as an addi...