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Control of a tip-force destabilized shear beam by observer-based boundary feedback. (English) Zbl 1167.35532

Summary: We consider a model of the undamped shear beam with a destabilizing boundary condition. The motivation for this model comes from atomic force microscopy, where the tip of the cantilever beam is destabilized by van der Waals forces acting between the tip and the material surface. Previous research efforts relied on collocated actuation and sensing at the tip, exploiting the passivity property between the corresponding input and output in the beam model. In this paper we design a stabilizing output-feedback controller in a noncollocated setting, with measurements at the free end (tip) of the beam and actuation at the beam base. Our control design is a novel combination of the classical “damping boundary feedback” idea with a recently developed backstepping approach. A change of variables is constructed which converts the beam model into a wave equation (for a very short string) with boundary damping. This approach is physically intuitive and allows both an elegant stability analysis and an easy selection of design parameters for achieving desired performance. Our observer design is a dual of the similar ideas, combining the damping feedback with backstepping, adapted to the observer error system. Both stability and well-posedness of the closed-loop system are proved. The simulation results are presented.

MSC:

35Q72 Other PDE from mechanics (MSC2000)
74K10 Rods (beams, columns, shafts, arches, rings, etc.)
35J05 Laplace operator, Helmholtz equation (reduced wave equation), Poisson equation
93B07 Observability
93D15 Stabilization of systems by feedback
93B52 Feedback control
93B60 Eigenvalue problems